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1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * predicate.c
4 : : * POSTGRES predicate locking
5 : : * to support full serializable transaction isolation
6 : : *
7 : : *
8 : : * The approach taken is to implement Serializable Snapshot Isolation (SSI)
9 : : * as initially described in this paper:
10 : : *
11 : : * Michael J. Cahill, Uwe Röhm, and Alan D. Fekete. 2008.
12 : : * Serializable isolation for snapshot databases.
13 : : * In SIGMOD '08: Proceedings of the 2008 ACM SIGMOD
14 : : * international conference on Management of data,
15 : : * pages 729-738, New York, NY, USA. ACM.
16 : : * http://doi.acm.org/10.1145/1376616.1376690
17 : : *
18 : : * and further elaborated in Cahill's doctoral thesis:
19 : : *
20 : : * Michael James Cahill. 2009.
21 : : * Serializable Isolation for Snapshot Databases.
22 : : * Sydney Digital Theses.
23 : : * University of Sydney, School of Information Technologies.
24 : : * http://hdl.handle.net/2123/5353
25 : : *
26 : : *
27 : : * Predicate locks for Serializable Snapshot Isolation (SSI) are SIREAD
28 : : * locks, which are so different from normal locks that a distinct set of
29 : : * structures is required to handle them. They are needed to detect
30 : : * rw-conflicts when the read happens before the write. (When the write
31 : : * occurs first, the reading transaction can check for a conflict by
32 : : * examining the MVCC data.)
33 : : *
34 : : * (1) Besides tuples actually read, they must cover ranges of tuples
35 : : * which would have been read based on the predicate. This will
36 : : * require modelling the predicates through locks against database
37 : : * objects such as pages, index ranges, or entire tables.
38 : : *
39 : : * (2) They must be kept in RAM for quick access. Because of this, it
40 : : * isn't possible to always maintain tuple-level granularity -- when
41 : : * the space allocated to store these approaches exhaustion, a
42 : : * request for a lock may need to scan for situations where a single
43 : : * transaction holds many fine-grained locks which can be coalesced
44 : : * into a single coarser-grained lock.
45 : : *
46 : : * (3) They never block anything; they are more like flags than locks
47 : : * in that regard; although they refer to database objects and are
48 : : * used to identify rw-conflicts with normal write locks.
49 : : *
50 : : * (4) While they are associated with a transaction, they must survive
51 : : * a successful COMMIT of that transaction, and remain until all
52 : : * overlapping transactions complete. This even means that they
53 : : * must survive termination of the transaction's process. If a
54 : : * top level transaction is rolled back, however, it is immediately
55 : : * flagged so that it can be ignored, and its SIREAD locks can be
56 : : * released any time after that.
57 : : *
58 : : * (5) The only transactions which create SIREAD locks or check for
59 : : * conflicts with them are serializable transactions.
60 : : *
61 : : * (6) When a write lock for a top level transaction is found to cover
62 : : * an existing SIREAD lock for the same transaction, the SIREAD lock
63 : : * can be deleted.
64 : : *
65 : : * (7) A write from a serializable transaction must ensure that an xact
66 : : * record exists for the transaction, with the same lifespan (until
67 : : * all concurrent transaction complete or the transaction is rolled
68 : : * back) so that rw-dependencies to that transaction can be
69 : : * detected.
70 : : *
71 : : * We use an optimization for read-only transactions. Under certain
72 : : * circumstances, a read-only transaction's snapshot can be shown to
73 : : * never have conflicts with other transactions. This is referred to
74 : : * as a "safe" snapshot (and one known not to be is "unsafe").
75 : : * However, it can't be determined whether a snapshot is safe until
76 : : * all concurrent read/write transactions complete.
77 : : *
78 : : * Once a read-only transaction is known to have a safe snapshot, it
79 : : * can release its predicate locks and exempt itself from further
80 : : * predicate lock tracking. READ ONLY DEFERRABLE transactions run only
81 : : * on safe snapshots, waiting as necessary for one to be available.
82 : : *
83 : : *
84 : : * Lightweight locks to manage access to the predicate locking shared
85 : : * memory objects must be taken in this order, and should be released in
86 : : * reverse order:
87 : : *
88 : : * SerializableFinishedListLock
89 : : * - Protects the list of transactions which have completed but which
90 : : * may yet matter because they overlap still-active transactions.
91 : : *
92 : : * SerializablePredicateListLock
93 : : * - Protects the linked list of locks held by a transaction. Note
94 : : * that the locks themselves are also covered by the partition
95 : : * locks of their respective lock targets; this lock only affects
96 : : * the linked list connecting the locks related to a transaction.
97 : : * - All transactions share this single lock (with no partitioning).
98 : : * - There is never a need for a process other than the one running
99 : : * an active transaction to walk the list of locks held by that
100 : : * transaction, except parallel query workers sharing the leader's
101 : : * transaction. In the parallel case, an extra per-sxact lock is
102 : : * taken; see below.
103 : : * - It is relatively infrequent that another process needs to
104 : : * modify the list for a transaction, but it does happen for such
105 : : * things as index page splits for pages with predicate locks and
106 : : * freeing of predicate locked pages by a vacuum process. When
107 : : * removing a lock in such cases, the lock itself contains the
108 : : * pointers needed to remove it from the list. When adding a
109 : : * lock in such cases, the lock can be added using the anchor in
110 : : * the transaction structure. Neither requires walking the list.
111 : : * - Cleaning up the list for a terminated transaction is sometimes
112 : : * not done on a retail basis, in which case no lock is required.
113 : : * - Due to the above, a process accessing its active transaction's
114 : : * list always uses a shared lock, regardless of whether it is
115 : : * walking or maintaining the list. This improves concurrency
116 : : * for the common access patterns.
117 : : * - A process which needs to alter the list of a transaction other
118 : : * than its own active transaction must acquire an exclusive
119 : : * lock.
120 : : *
121 : : * SERIALIZABLEXACT's member 'perXactPredicateListLock'
122 : : * - Protects the linked list of predicate locks held by a transaction.
123 : : * Only needed for parallel mode, where multiple backends share the
124 : : * same SERIALIZABLEXACT object. Not needed if
125 : : * SerializablePredicateListLock is held exclusively.
126 : : *
127 : : * PredicateLockHashPartitionLock(hashcode)
128 : : * - The same lock protects a target, all locks on that target, and
129 : : * the linked list of locks on the target.
130 : : * - When more than one is needed, acquire in ascending address order.
131 : : * - When all are needed (rare), acquire in ascending index order with
132 : : * PredicateLockHashPartitionLockByIndex(index).
133 : : *
134 : : * SerializableXactHashLock
135 : : * - Protects both PredXact and SerializableXidHash.
136 : : *
137 : : * SerialControlLock
138 : : * - Protects SerialControlData members
139 : : *
140 : : * SLRU per-bank locks
141 : : * - Protects SerialSlruCtl
142 : : *
143 : : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
144 : : * Portions Copyright (c) 1994, Regents of the University of California
145 : : *
146 : : *
147 : : * IDENTIFICATION
148 : : * src/backend/storage/lmgr/predicate.c
149 : : *
150 : : *-------------------------------------------------------------------------
151 : : */
152 : : /*
153 : : * INTERFACE ROUTINES
154 : : *
155 : : * predicate lock reporting
156 : : * GetPredicateLockStatusData(void)
157 : : * PageIsPredicateLocked(Relation relation, BlockNumber blkno)
158 : : *
159 : : * predicate lock maintenance
160 : : * GetSerializableTransactionSnapshot(Snapshot snapshot)
161 : : * SetSerializableTransactionSnapshot(Snapshot snapshot,
162 : : * VirtualTransactionId *sourcevxid)
163 : : * RegisterPredicateLockingXid(void)
164 : : * PredicateLockRelation(Relation relation, Snapshot snapshot)
165 : : * PredicateLockPage(Relation relation, BlockNumber blkno,
166 : : * Snapshot snapshot)
167 : : * PredicateLockTID(Relation relation, const ItemPointerData *tid, Snapshot snapshot,
168 : : * TransactionId tuple_xid)
169 : : * PredicateLockPageSplit(Relation relation, BlockNumber oldblkno,
170 : : * BlockNumber newblkno)
171 : : * PredicateLockPageCombine(Relation relation, BlockNumber oldblkno,
172 : : * BlockNumber newblkno)
173 : : * TransferPredicateLocksToHeapRelation(Relation relation)
174 : : * ReleasePredicateLocks(bool isCommit, bool isReadOnlySafe)
175 : : *
176 : : * conflict detection (may also trigger rollback)
177 : : * CheckForSerializableConflictOut(Relation relation, TransactionId xid,
178 : : * Snapshot snapshot)
179 : : * CheckForSerializableConflictIn(Relation relation, const ItemPointerData *tid,
180 : : * BlockNumber blkno)
181 : : * CheckTableForSerializableConflictIn(Relation relation)
182 : : *
183 : : * final rollback checking
184 : : * PreCommit_CheckForSerializationFailure(void)
185 : : *
186 : : * two-phase commit support
187 : : * AtPrepare_PredicateLocks(void);
188 : : * PostPrepare_PredicateLocks(TransactionId xid);
189 : : * PredicateLockTwoPhaseFinish(FullTransactionId fxid, bool isCommit);
190 : : * predicatelock_twophase_recover(FullTransactionId fxid, uint16 info,
191 : : * void *recdata, uint32 len);
192 : : */
193 : :
194 : : #include "postgres.h"
195 : :
196 : : #include "access/parallel.h"
197 : : #include "access/slru.h"
198 : : #include "access/transam.h"
199 : : #include "access/twophase.h"
200 : : #include "access/twophase_rmgr.h"
201 : : #include "access/xact.h"
202 : : #include "access/xlog.h"
203 : : #include "miscadmin.h"
204 : : #include "pgstat.h"
205 : : #include "port/pg_lfind.h"
206 : : #include "storage/predicate.h"
207 : : #include "storage/predicate_internals.h"
208 : : #include "storage/proc.h"
209 : : #include "storage/procarray.h"
210 : : #include "storage/shmem.h"
211 : : #include "storage/subsystems.h"
212 : : #include "utils/guc_hooks.h"
213 : : #include "utils/rel.h"
214 : : #include "utils/snapmgr.h"
215 : : #include "utils/wait_event.h"
216 : :
217 : : /* Uncomment the next line to test the graceful degradation code. */
218 : : /* #define TEST_SUMMARIZE_SERIAL */
219 : :
220 : : /*
221 : : * Test the most selective fields first, for performance.
222 : : *
223 : : * a is covered by b if all of the following hold:
224 : : * 1) a.database = b.database
225 : : * 2) a.relation = b.relation
226 : : * 3) b.offset is invalid (b is page-granularity or higher)
227 : : * 4) either of the following:
228 : : * 4a) a.offset is valid (a is tuple-granularity) and a.page = b.page
229 : : * or 4b) a.offset is invalid and b.page is invalid (a is
230 : : * page-granularity and b is relation-granularity
231 : : */
232 : : #define TargetTagIsCoveredBy(covered_target, covering_target) \
233 : : ((GET_PREDICATELOCKTARGETTAG_RELATION(covered_target) == /* (2) */ \
234 : : GET_PREDICATELOCKTARGETTAG_RELATION(covering_target)) \
235 : : && (GET_PREDICATELOCKTARGETTAG_OFFSET(covering_target) == \
236 : : InvalidOffsetNumber) /* (3) */ \
237 : : && (((GET_PREDICATELOCKTARGETTAG_OFFSET(covered_target) != \
238 : : InvalidOffsetNumber) /* (4a) */ \
239 : : && (GET_PREDICATELOCKTARGETTAG_PAGE(covering_target) == \
240 : : GET_PREDICATELOCKTARGETTAG_PAGE(covered_target))) \
241 : : || ((GET_PREDICATELOCKTARGETTAG_PAGE(covering_target) == \
242 : : InvalidBlockNumber) /* (4b) */ \
243 : : && (GET_PREDICATELOCKTARGETTAG_PAGE(covered_target) \
244 : : != InvalidBlockNumber))) \
245 : : && (GET_PREDICATELOCKTARGETTAG_DB(covered_target) == /* (1) */ \
246 : : GET_PREDICATELOCKTARGETTAG_DB(covering_target)))
247 : :
248 : : /*
249 : : * The predicate locking target and lock shared hash tables are partitioned to
250 : : * reduce contention. To determine which partition a given target belongs to,
251 : : * compute the tag's hash code with PredicateLockTargetTagHashCode(), then
252 : : * apply one of these macros.
253 : : * NB: NUM_PREDICATELOCK_PARTITIONS must be a power of 2!
254 : : */
255 : : #define PredicateLockHashPartition(hashcode) \
256 : : ((hashcode) % NUM_PREDICATELOCK_PARTITIONS)
257 : : #define PredicateLockHashPartitionLock(hashcode) \
258 : : (&MainLWLockArray[PREDICATELOCK_MANAGER_LWLOCK_OFFSET + \
259 : : PredicateLockHashPartition(hashcode)].lock)
260 : : #define PredicateLockHashPartitionLockByIndex(i) \
261 : : (&MainLWLockArray[PREDICATELOCK_MANAGER_LWLOCK_OFFSET + (i)].lock)
262 : :
263 : : #define NPREDICATELOCKTARGETENTS() \
264 : : mul_size(max_predicate_locks_per_xact, add_size(MaxBackends, max_prepared_xacts))
265 : :
266 : : #define SxactIsOnFinishedList(sxact) (!dlist_node_is_detached(&(sxact)->finishedLink))
267 : :
268 : : /*
269 : : * Note that a sxact is marked "prepared" once it has passed
270 : : * PreCommit_CheckForSerializationFailure, even if it isn't using
271 : : * 2PC. This is the point at which it can no longer be aborted.
272 : : *
273 : : * The PREPARED flag remains set after commit, so SxactIsCommitted
274 : : * implies SxactIsPrepared.
275 : : */
276 : : #define SxactIsCommitted(sxact) (((sxact)->flags & SXACT_FLAG_COMMITTED) != 0)
277 : : #define SxactIsPrepared(sxact) (((sxact)->flags & SXACT_FLAG_PREPARED) != 0)
278 : : #define SxactIsRolledBack(sxact) (((sxact)->flags & SXACT_FLAG_ROLLED_BACK) != 0)
279 : : #define SxactIsDoomed(sxact) (((sxact)->flags & SXACT_FLAG_DOOMED) != 0)
280 : : #define SxactIsReadOnly(sxact) (((sxact)->flags & SXACT_FLAG_READ_ONLY) != 0)
281 : : #define SxactHasSummaryConflictIn(sxact) (((sxact)->flags & SXACT_FLAG_SUMMARY_CONFLICT_IN) != 0)
282 : : #define SxactHasSummaryConflictOut(sxact) (((sxact)->flags & SXACT_FLAG_SUMMARY_CONFLICT_OUT) != 0)
283 : : /*
284 : : * The following macro actually means that the specified transaction has a
285 : : * conflict out *to a transaction which committed ahead of it*. It's hard
286 : : * to get that into a name of a reasonable length.
287 : : */
288 : : #define SxactHasConflictOut(sxact) (((sxact)->flags & SXACT_FLAG_CONFLICT_OUT) != 0)
289 : : #define SxactIsDeferrableWaiting(sxact) (((sxact)->flags & SXACT_FLAG_DEFERRABLE_WAITING) != 0)
290 : : #define SxactIsROSafe(sxact) (((sxact)->flags & SXACT_FLAG_RO_SAFE) != 0)
291 : : #define SxactIsROUnsafe(sxact) (((sxact)->flags & SXACT_FLAG_RO_UNSAFE) != 0)
292 : : #define SxactIsPartiallyReleased(sxact) (((sxact)->flags & SXACT_FLAG_PARTIALLY_RELEASED) != 0)
293 : :
294 : : /*
295 : : * Compute the hash code associated with a PREDICATELOCKTARGETTAG.
296 : : *
297 : : * To avoid unnecessary recomputations of the hash code, we try to do this
298 : : * just once per function, and then pass it around as needed. Aside from
299 : : * passing the hashcode to hash_search_with_hash_value(), we can extract
300 : : * the lock partition number from the hashcode.
301 : : */
302 : : #define PredicateLockTargetTagHashCode(predicatelocktargettag) \
303 : : get_hash_value(PredicateLockTargetHash, predicatelocktargettag)
304 : :
305 : : /*
306 : : * Given a predicate lock tag, and the hash for its target,
307 : : * compute the lock hash.
308 : : *
309 : : * To make the hash code also depend on the transaction, we xor the sxid
310 : : * struct's address into the hash code, left-shifted so that the
311 : : * partition-number bits don't change. Since this is only a hash, we
312 : : * don't care if we lose high-order bits of the address; use an
313 : : * intermediate variable to suppress cast-pointer-to-int warnings.
314 : : */
315 : : #define PredicateLockHashCodeFromTargetHashCode(predicatelocktag, targethash) \
316 : : ((targethash) ^ ((uint32) PointerGetDatum((predicatelocktag)->myXact)) \
317 : : << LOG2_NUM_PREDICATELOCK_PARTITIONS)
318 : :
319 : :
320 : : /*
321 : : * The SLRU buffer area through which we access the old xids.
322 : : */
323 : : static bool SerialPagePrecedesLogically(int64 page1, int64 page2);
324 : : static int serial_errdetail_for_io_error(const void *opaque_data);
325 : :
326 : : static SlruDesc SerialSlruDesc;
327 : :
328 : : #define SerialSlruCtl (&SerialSlruDesc)
329 : :
330 : : #define SERIAL_PAGESIZE BLCKSZ
331 : : #define SERIAL_ENTRYSIZE sizeof(SerCommitSeqNo)
332 : : #define SERIAL_ENTRIESPERPAGE (SERIAL_PAGESIZE / SERIAL_ENTRYSIZE)
333 : :
334 : : /*
335 : : * Set maximum pages based on the number needed to track all transactions.
336 : : */
337 : : #define SERIAL_MAX_PAGE (MaxTransactionId / SERIAL_ENTRIESPERPAGE)
338 : :
339 : : #define SerialNextPage(page) (((page) >= SERIAL_MAX_PAGE) ? 0 : (page) + 1)
340 : :
341 : : #define SerialValue(slotno, xid) (*((SerCommitSeqNo *) \
342 : : (SerialSlruCtl->shared->page_buffer[slotno] + \
343 : : ((((uint32) (xid)) % SERIAL_ENTRIESPERPAGE) * SERIAL_ENTRYSIZE))))
344 : :
345 : : #define SerialPage(xid) (((uint32) (xid)) / SERIAL_ENTRIESPERPAGE)
346 : :
347 : : typedef struct SerialControlData
348 : : {
349 : : int64 headPage; /* newest initialized page */
350 : : TransactionId headXid; /* newest valid Xid in the SLRU */
351 : : TransactionId tailXid; /* oldest xmin we might be interested in */
352 : : } SerialControlData;
353 : :
354 : : typedef struct SerialControlData *SerialControl;
355 : :
356 : : static SerialControl serialControl;
357 : :
358 : : /*
359 : : * When the oldest committed transaction on the "finished" list is moved to
360 : : * SLRU, its predicate locks will be moved to this "dummy" transaction,
361 : : * collapsing duplicate targets. When a duplicate is found, the later
362 : : * commitSeqNo is used.
363 : : */
364 : : static SERIALIZABLEXACT *OldCommittedSxact;
365 : :
366 : :
367 : : /*
368 : : * These configuration variables are used to set the predicate lock table size
369 : : * and to control promotion of predicate locks to coarser granularity in an
370 : : * attempt to degrade performance (mostly as false positive serialization
371 : : * failure) gracefully in the face of memory pressure.
372 : : */
373 : : int max_predicate_locks_per_xact; /* in guc_tables.c */
374 : : int max_predicate_locks_per_relation; /* in guc_tables.c */
375 : : int max_predicate_locks_per_page; /* in guc_tables.c */
376 : :
377 : : /*
378 : : * This provides a list of objects in order to track transactions
379 : : * participating in predicate locking. Entries in the list are fixed size,
380 : : * and reside in shared memory. The memory address of an entry must remain
381 : : * fixed during its lifetime. The list will be protected from concurrent
382 : : * update externally; no provision is made in this code to manage that. The
383 : : * number of entries in the list, and the size allowed for each entry is
384 : : * fixed upon creation.
385 : : */
386 : : static PredXactList PredXact;
387 : :
388 : : static void PredicateLockShmemRequest(void *arg);
389 : : static void PredicateLockShmemInit(void *arg);
390 : : static void PredicateLockShmemAttach(void *arg);
391 : :
392 : : const ShmemCallbacks PredicateLockShmemCallbacks = {
393 : : .request_fn = PredicateLockShmemRequest,
394 : : .init_fn = PredicateLockShmemInit,
395 : : .attach_fn = PredicateLockShmemAttach,
396 : : };
397 : :
398 : :
399 : : /*
400 : : * This provides a pool of RWConflict data elements to use in conflict lists
401 : : * between transactions.
402 : : */
403 : : static RWConflictPoolHeader RWConflictPool;
404 : :
405 : : /*
406 : : * The predicate locking hash tables are in shared memory.
407 : : * Each backend keeps pointers to them.
408 : : */
409 : : static HTAB *SerializableXidHash;
410 : : static HTAB *PredicateLockTargetHash;
411 : : static HTAB *PredicateLockHash;
412 : : static dlist_head *FinishedSerializableTransactions;
413 : :
414 : : /*
415 : : * Tag for a dummy entry in PredicateLockTargetHash. By temporarily removing
416 : : * this entry, you can ensure that there's enough scratch space available for
417 : : * inserting one entry in the hash table. This is an otherwise-invalid tag.
418 : : */
419 : : static const PREDICATELOCKTARGETTAG ScratchTargetTag = {0, 0, 0, 0};
420 : : static uint32 ScratchTargetTagHash;
421 : : static LWLock *ScratchPartitionLock;
422 : :
423 : : /*
424 : : * The local hash table used to determine when to combine multiple fine-
425 : : * grained locks into a single courser-grained lock.
426 : : */
427 : : static HTAB *LocalPredicateLockHash = NULL;
428 : :
429 : : /*
430 : : * Keep a pointer to the currently-running serializable transaction (if any)
431 : : * for quick reference. Also, remember if we have written anything that could
432 : : * cause a rw-conflict.
433 : : */
434 : : static SERIALIZABLEXACT *MySerializableXact = InvalidSerializableXact;
435 : : static bool MyXactDidWrite = false;
436 : :
437 : : /*
438 : : * The SXACT_FLAG_RO_UNSAFE optimization might lead us to release
439 : : * MySerializableXact early. If that happens in a parallel query, the leader
440 : : * needs to defer the destruction of the SERIALIZABLEXACT until end of
441 : : * transaction, because the workers still have a reference to it. In that
442 : : * case, the leader stores it here.
443 : : */
444 : : static SERIALIZABLEXACT *SavedSerializableXact = InvalidSerializableXact;
445 : :
446 : : static int64 max_serializable_xacts;
447 : :
448 : : /* local functions */
449 : :
450 : : static SERIALIZABLEXACT *CreatePredXact(void);
451 : : static void ReleasePredXact(SERIALIZABLEXACT *sxact);
452 : :
453 : : static bool RWConflictExists(const SERIALIZABLEXACT *reader, const SERIALIZABLEXACT *writer);
454 : : static void SetRWConflict(SERIALIZABLEXACT *reader, SERIALIZABLEXACT *writer);
455 : : static void SetPossibleUnsafeConflict(SERIALIZABLEXACT *roXact, SERIALIZABLEXACT *activeXact);
456 : : static void ReleaseRWConflict(RWConflict conflict);
457 : : static void FlagSxactUnsafe(SERIALIZABLEXACT *sxact);
458 : :
459 : : static void SerialAdd(TransactionId xid, SerCommitSeqNo minConflictCommitSeqNo);
460 : : static SerCommitSeqNo SerialGetMinConflictCommitSeqNo(TransactionId xid);
461 : : static void SerialSetActiveSerXmin(TransactionId xid);
462 : :
463 : : static uint32 predicatelock_hash(const void *key, Size keysize);
464 : :
465 : : static void SummarizeOldestCommittedSxact(void);
466 : : static Snapshot GetSafeSnapshot(Snapshot origSnapshot);
467 : : static Snapshot GetSerializableTransactionSnapshotInt(Snapshot snapshot,
468 : : VirtualTransactionId *sourcevxid,
469 : : int sourcepid);
470 : : static bool PredicateLockExists(const PREDICATELOCKTARGETTAG *targettag);
471 : : static bool GetParentPredicateLockTag(const PREDICATELOCKTARGETTAG *tag,
472 : : PREDICATELOCKTARGETTAG *parent);
473 : : static bool CoarserLockCovers(const PREDICATELOCKTARGETTAG *newtargettag);
474 : : static void RemoveScratchTarget(bool lockheld);
475 : : static void RestoreScratchTarget(bool lockheld);
476 : : static void RemoveTargetIfNoLongerUsed(PREDICATELOCKTARGET *target,
477 : : uint32 targettaghash);
478 : : static void DeleteChildTargetLocks(const PREDICATELOCKTARGETTAG *newtargettag);
479 : : static int MaxPredicateChildLocks(const PREDICATELOCKTARGETTAG *tag);
480 : : static bool CheckAndPromotePredicateLockRequest(const PREDICATELOCKTARGETTAG *reqtag);
481 : : static void DecrementParentLocks(const PREDICATELOCKTARGETTAG *targettag);
482 : : static void CreatePredicateLock(const PREDICATELOCKTARGETTAG *targettag,
483 : : uint32 targettaghash,
484 : : SERIALIZABLEXACT *sxact);
485 : : static void DeleteLockTarget(PREDICATELOCKTARGET *target, uint32 targettaghash);
486 : : static bool TransferPredicateLocksToNewTarget(PREDICATELOCKTARGETTAG oldtargettag,
487 : : PREDICATELOCKTARGETTAG newtargettag,
488 : : bool removeOld);
489 : : static void PredicateLockAcquire(const PREDICATELOCKTARGETTAG *targettag);
490 : : static void DropAllPredicateLocksFromTable(Relation relation,
491 : : bool transfer);
492 : : static void SetNewSxactGlobalXmin(void);
493 : : static void ClearOldPredicateLocks(void);
494 : : static void ReleaseOneSerializableXact(SERIALIZABLEXACT *sxact, bool partial,
495 : : bool summarize);
496 : : static bool XidIsConcurrent(TransactionId xid);
497 : : static void CheckTargetForConflictsIn(PREDICATELOCKTARGETTAG *targettag);
498 : : static void FlagRWConflict(SERIALIZABLEXACT *reader, SERIALIZABLEXACT *writer);
499 : : static void OnConflict_CheckForSerializationFailure(const SERIALIZABLEXACT *reader,
500 : : SERIALIZABLEXACT *writer);
501 : : static void CreateLocalPredicateLockHash(void);
502 : : static void ReleasePredicateLocksLocal(void);
503 : :
504 : :
505 : : /*------------------------------------------------------------------------*/
506 : :
507 : : /*
508 : : * Does this relation participate in predicate locking? Temporary and system
509 : : * relations are exempt.
510 : : */
511 : : static inline bool
512 : 145032 : PredicateLockingNeededForRelation(Relation relation)
513 : : {
514 [ + + ]: 184907 : return !(relation->rd_id < FirstUnpinnedObjectId ||
515 [ + + ]: 39875 : RelationUsesLocalBuffers(relation));
516 : : }
517 : :
518 : : /*
519 : : * When a public interface method is called for a read, this is the test to
520 : : * see if we should do a quick return.
521 : : *
522 : : * Note: this function has side-effects! If this transaction has been flagged
523 : : * as RO-safe since the last call, we release all predicate locks and reset
524 : : * MySerializableXact. That makes subsequent calls to return quickly.
525 : : *
526 : : * This is marked as 'inline' to eliminate the function call overhead in the
527 : : * common case that serialization is not needed.
528 : : */
529 : : static inline bool
530 : 83931358 : SerializationNeededForRead(Relation relation, Snapshot snapshot)
531 : : {
532 : : /* Nothing to do if this is not a serializable transaction */
533 [ + + ]: 83931358 : if (MySerializableXact == InvalidSerializableXact)
534 : 83792862 : return false;
535 : :
536 : : /*
537 : : * Don't acquire locks or conflict when scanning with a special snapshot.
538 : : * This excludes things like CLUSTER and REINDEX. They use the wholesale
539 : : * functions TransferPredicateLocksToHeapRelation() and
540 : : * CheckTableForSerializableConflictIn() to participate in serialization,
541 : : * but the scans involved don't need serialization.
542 : : */
543 [ + + ]: 138496 : if (!IsMVCCSnapshot(snapshot))
544 : 1965 : return false;
545 : :
546 : : /*
547 : : * Check if we have just become "RO-safe". If we have, immediately release
548 : : * all locks as they're not needed anymore. This also resets
549 : : * MySerializableXact, so that subsequent calls to this function can exit
550 : : * quickly.
551 : : *
552 : : * A transaction is flagged as RO_SAFE if all concurrent R/W transactions
553 : : * commit without having conflicts out to an earlier snapshot, thus
554 : : * ensuring that no conflicts are possible for this transaction.
555 : : */
556 [ + + ]: 136531 : if (SxactIsROSafe(MySerializableXact))
557 : : {
558 : 33 : ReleasePredicateLocks(false, true);
559 : 33 : return false;
560 : : }
561 : :
562 : : /* Check if the relation doesn't participate in predicate locking */
563 [ + + ]: 136498 : if (!PredicateLockingNeededForRelation(relation))
564 : 101395 : return false;
565 : :
566 : 35103 : return true; /* no excuse to skip predicate locking */
567 : : }
568 : :
569 : : /*
570 : : * Like SerializationNeededForRead(), but called on writes.
571 : : * The logic is the same, but there is no snapshot and we can't be RO-safe.
572 : : */
573 : : static inline bool
574 : 25222780 : SerializationNeededForWrite(Relation relation)
575 : : {
576 : : /* Nothing to do if this is not a serializable transaction */
577 [ + + ]: 25222780 : if (MySerializableXact == InvalidSerializableXact)
578 : 25214368 : return false;
579 : :
580 : : /* Check if the relation doesn't participate in predicate locking */
581 [ + + ]: 8412 : if (!PredicateLockingNeededForRelation(relation))
582 : 3886 : return false;
583 : :
584 : 4526 : return true; /* no excuse to skip predicate locking */
585 : : }
586 : :
587 : :
588 : : /*------------------------------------------------------------------------*/
589 : :
590 : : /*
591 : : * These functions are a simple implementation of a list for this specific
592 : : * type of struct. If there is ever a generalized shared memory list, we
593 : : * should probably switch to that.
594 : : */
595 : : static SERIALIZABLEXACT *
596 : 2948 : CreatePredXact(void)
597 : : {
598 : : SERIALIZABLEXACT *sxact;
599 : :
600 [ - + ]: 2948 : if (dlist_is_empty(&PredXact->availableList))
601 : 0 : return NULL;
602 : :
603 : 2948 : sxact = dlist_container(SERIALIZABLEXACT, xactLink,
604 : : dlist_pop_head_node(&PredXact->availableList));
605 : 2948 : dlist_push_tail(&PredXact->activeList, &sxact->xactLink);
606 : 2948 : return sxact;
607 : : }
608 : :
609 : : static void
610 : 1692 : ReleasePredXact(SERIALIZABLEXACT *sxact)
611 : : {
612 : : Assert(ShmemAddrIsValid(sxact));
613 : :
614 : 1692 : dlist_delete(&sxact->xactLink);
615 : 1692 : dlist_push_tail(&PredXact->availableList, &sxact->xactLink);
616 : 1692 : }
617 : :
618 : : /*------------------------------------------------------------------------*/
619 : :
620 : : /*
621 : : * These functions manage primitive access to the RWConflict pool and lists.
622 : : */
623 : : static bool
624 : 1890 : RWConflictExists(const SERIALIZABLEXACT *reader, const SERIALIZABLEXACT *writer)
625 : : {
626 : : dlist_iter iter;
627 : :
628 : : Assert(reader != writer);
629 : :
630 : : /* Check the ends of the purported conflict first. */
631 [ + - ]: 1890 : if (SxactIsDoomed(reader)
632 [ + - ]: 1890 : || SxactIsDoomed(writer)
633 [ + + ]: 1890 : || dlist_is_empty(&reader->outConflicts)
634 [ + + ]: 569 : || dlist_is_empty(&writer->inConflicts))
635 : 1361 : return false;
636 : :
637 : : /*
638 : : * A conflict is possible; walk the list to find out.
639 : : *
640 : : * The unconstify is needed as we have no const version of
641 : : * dlist_foreach().
642 : : */
643 [ + - + + ]: 545 : dlist_foreach(iter, &unconstify(SERIALIZABLEXACT *, reader)->outConflicts)
644 : : {
645 : 529 : RWConflict conflict =
646 : : dlist_container(RWConflictData, outLink, iter.cur);
647 : :
648 [ + + ]: 529 : if (conflict->sxactIn == writer)
649 : 513 : return true;
650 : : }
651 : :
652 : : /* No conflict found. */
653 : 16 : return false;
654 : : }
655 : :
656 : : static void
657 : 792 : SetRWConflict(SERIALIZABLEXACT *reader, SERIALIZABLEXACT *writer)
658 : : {
659 : : RWConflict conflict;
660 : :
661 : : Assert(reader != writer);
662 : : Assert(!RWConflictExists(reader, writer));
663 : :
664 [ - + ]: 792 : if (dlist_is_empty(&RWConflictPool->availableList))
665 [ # # ]: 0 : ereport(ERROR,
666 : : (errcode(ERRCODE_OUT_OF_MEMORY),
667 : : errmsg("not enough elements in RWConflictPool to record a read/write conflict"),
668 : : errhint("You might need to run fewer transactions at a time or increase \"max_connections\".")));
669 : :
670 : 792 : conflict = dlist_head_element(RWConflictData, outLink, &RWConflictPool->availableList);
671 : 792 : dlist_delete(&conflict->outLink);
672 : :
673 : 792 : conflict->sxactOut = reader;
674 : 792 : conflict->sxactIn = writer;
675 : 792 : dlist_push_tail(&reader->outConflicts, &conflict->outLink);
676 : 792 : dlist_push_tail(&writer->inConflicts, &conflict->inLink);
677 : 792 : }
678 : :
679 : : static void
680 : 133 : SetPossibleUnsafeConflict(SERIALIZABLEXACT *roXact,
681 : : SERIALIZABLEXACT *activeXact)
682 : : {
683 : : RWConflict conflict;
684 : :
685 : : Assert(roXact != activeXact);
686 : : Assert(SxactIsReadOnly(roXact));
687 : : Assert(!SxactIsReadOnly(activeXact));
688 : :
689 [ - + ]: 133 : if (dlist_is_empty(&RWConflictPool->availableList))
690 [ # # ]: 0 : ereport(ERROR,
691 : : (errcode(ERRCODE_OUT_OF_MEMORY),
692 : : errmsg("not enough elements in RWConflictPool to record a potential read/write conflict"),
693 : : errhint("You might need to run fewer transactions at a time or increase \"max_connections\".")));
694 : :
695 : 133 : conflict = dlist_head_element(RWConflictData, outLink, &RWConflictPool->availableList);
696 : 133 : dlist_delete(&conflict->outLink);
697 : :
698 : 133 : conflict->sxactOut = activeXact;
699 : 133 : conflict->sxactIn = roXact;
700 : 133 : dlist_push_tail(&activeXact->possibleUnsafeConflicts, &conflict->outLink);
701 : 133 : dlist_push_tail(&roXact->possibleUnsafeConflicts, &conflict->inLink);
702 : 133 : }
703 : :
704 : : static void
705 : 925 : ReleaseRWConflict(RWConflict conflict)
706 : : {
707 : 925 : dlist_delete(&conflict->inLink);
708 : 925 : dlist_delete(&conflict->outLink);
709 : 925 : dlist_push_tail(&RWConflictPool->availableList, &conflict->outLink);
710 : 925 : }
711 : :
712 : : static void
713 : 3 : FlagSxactUnsafe(SERIALIZABLEXACT *sxact)
714 : : {
715 : : dlist_mutable_iter iter;
716 : :
717 : : Assert(SxactIsReadOnly(sxact));
718 : : Assert(!SxactIsROSafe(sxact));
719 : :
720 : 3 : sxact->flags |= SXACT_FLAG_RO_UNSAFE;
721 : :
722 : : /*
723 : : * We know this isn't a safe snapshot, so we can stop looking for other
724 : : * potential conflicts.
725 : : */
726 [ + - + + ]: 6 : dlist_foreach_modify(iter, &sxact->possibleUnsafeConflicts)
727 : : {
728 : 3 : RWConflict conflict =
729 : 3 : dlist_container(RWConflictData, inLink, iter.cur);
730 : :
731 : : Assert(!SxactIsReadOnly(conflict->sxactOut));
732 : : Assert(sxact == conflict->sxactIn);
733 : :
734 : 3 : ReleaseRWConflict(conflict);
735 : : }
736 : 3 : }
737 : :
738 : : /*------------------------------------------------------------------------*/
739 : :
740 : : /*
741 : : * Decide whether a Serial page number is "older" for truncation purposes.
742 : : * Analogous to CLOGPagePrecedes().
743 : : */
744 : : static bool
745 : 0 : SerialPagePrecedesLogically(int64 page1, int64 page2)
746 : : {
747 : : TransactionId xid1;
748 : : TransactionId xid2;
749 : :
750 : 0 : xid1 = ((TransactionId) page1) * SERIAL_ENTRIESPERPAGE;
751 : 0 : xid1 += FirstNormalTransactionId + 1;
752 : 0 : xid2 = ((TransactionId) page2) * SERIAL_ENTRIESPERPAGE;
753 : 0 : xid2 += FirstNormalTransactionId + 1;
754 : :
755 [ # # # # ]: 0 : return (TransactionIdPrecedes(xid1, xid2) &&
756 : 0 : TransactionIdPrecedes(xid1, xid2 + SERIAL_ENTRIESPERPAGE - 1));
757 : : }
758 : :
759 : : static int
760 : 0 : serial_errdetail_for_io_error(const void *opaque_data)
761 : : {
762 : 0 : TransactionId xid = *(const TransactionId *) opaque_data;
763 : :
764 : 0 : return errdetail("Could not access serializable CSN of transaction %u.", xid);
765 : : }
766 : :
767 : : #ifdef USE_ASSERT_CHECKING
768 : : static void
769 : : SerialPagePrecedesLogicallyUnitTests(void)
770 : : {
771 : : int per_page = SERIAL_ENTRIESPERPAGE,
772 : : offset = per_page / 2;
773 : : int64 newestPage,
774 : : oldestPage,
775 : : headPage,
776 : : targetPage;
777 : : TransactionId newestXact,
778 : : oldestXact;
779 : :
780 : : /* GetNewTransactionId() has assigned the last XID it can safely use. */
781 : : newestPage = 2 * SLRU_PAGES_PER_SEGMENT - 1; /* nothing special */
782 : : newestXact = newestPage * per_page + offset;
783 : : Assert(newestXact / per_page == newestPage);
784 : : oldestXact = newestXact + 1;
785 : : oldestXact -= 1U << 31;
786 : : oldestPage = oldestXact / per_page;
787 : :
788 : : /*
789 : : * In this scenario, the SLRU headPage pertains to the last ~1000 XIDs
790 : : * assigned. oldestXact finishes, ~2B XIDs having elapsed since it
791 : : * started. Further transactions cause us to summarize oldestXact to
792 : : * tailPage. Function must return false so SerialAdd() doesn't zero
793 : : * tailPage (which may contain entries for other old, recently-finished
794 : : * XIDs) and half the SLRU. Reaching this requires burning ~2B XIDs in
795 : : * single-user mode, a negligible possibility.
796 : : */
797 : : headPage = newestPage;
798 : : targetPage = oldestPage;
799 : : Assert(!SerialPagePrecedesLogically(headPage, targetPage));
800 : :
801 : : /*
802 : : * In this scenario, the SLRU headPage pertains to oldestXact. We're
803 : : * summarizing an XID near newestXact. (Assume few other XIDs used
804 : : * SERIALIZABLE, hence the minimal headPage advancement. Assume
805 : : * oldestXact was long-running and only recently reached the SLRU.)
806 : : * Function must return true to make SerialAdd() create targetPage.
807 : : *
808 : : * Today's implementation mishandles this case, but it doesn't matter
809 : : * enough to fix. Verify that the defect affects just one page by
810 : : * asserting correct treatment of its prior page. Reaching this case
811 : : * requires burning ~2B XIDs in single-user mode, a negligible
812 : : * possibility. Moreover, if it does happen, the consequence would be
813 : : * mild, namely a new transaction failing in SimpleLruReadPage().
814 : : */
815 : : headPage = oldestPage;
816 : : targetPage = newestPage;
817 : : Assert(SerialPagePrecedesLogically(headPage, targetPage - 1));
818 : : #if 0
819 : : Assert(SerialPagePrecedesLogically(headPage, targetPage));
820 : : #endif
821 : : }
822 : : #endif
823 : :
824 : : /*
825 : : * GUC check_hook for serializable_buffers
826 : : */
827 : : bool
828 : 1299 : check_serial_buffers(int *newval, void **extra, GucSource source)
829 : : {
830 : 1299 : return check_slru_buffers("serializable_buffers", newval);
831 : : }
832 : :
833 : : /*
834 : : * Record a committed read write serializable xid and the minimum
835 : : * commitSeqNo of any transactions to which this xid had a rw-conflict out.
836 : : * An invalid commitSeqNo means that there were no conflicts out from xid.
837 : : */
838 : : static void
839 : 0 : SerialAdd(TransactionId xid, SerCommitSeqNo minConflictCommitSeqNo)
840 : : {
841 : : TransactionId tailXid;
842 : : int64 targetPage;
843 : : int slotno;
844 : : int64 firstZeroPage;
845 : : bool isNewPage;
846 : : LWLock *lock;
847 : :
848 : : Assert(TransactionIdIsValid(xid));
849 : :
850 : 0 : targetPage = SerialPage(xid);
851 : 0 : lock = SimpleLruGetBankLock(SerialSlruCtl, targetPage);
852 : :
853 : : /*
854 : : * In this routine, we must hold both SerialControlLock and the SLRU bank
855 : : * lock simultaneously while making the SLRU data catch up with the new
856 : : * state that we determine.
857 : : */
858 : 0 : LWLockAcquire(SerialControlLock, LW_EXCLUSIVE);
859 : :
860 : : /*
861 : : * If 'xid' is older than the global xmin (== tailXid), there's no need to
862 : : * store it, after all. This can happen if the oldest transaction holding
863 : : * back the global xmin just finished, making 'xid' uninteresting, but
864 : : * ClearOldPredicateLocks() has not yet run.
865 : : */
866 : 0 : tailXid = serialControl->tailXid;
867 [ # # # # ]: 0 : if (!TransactionIdIsValid(tailXid) || TransactionIdPrecedes(xid, tailXid))
868 : : {
869 : 0 : LWLockRelease(SerialControlLock);
870 : 0 : return;
871 : : }
872 : :
873 : : /*
874 : : * If the SLRU is currently unused, zero out the whole active region from
875 : : * tailXid to headXid before taking it into use. Otherwise zero out only
876 : : * any new pages that enter the tailXid-headXid range as we advance
877 : : * headXid.
878 : : */
879 [ # # ]: 0 : if (serialControl->headPage < 0)
880 : : {
881 : 0 : firstZeroPage = SerialPage(tailXid);
882 : 0 : isNewPage = true;
883 : : }
884 : : else
885 : : {
886 [ # # ]: 0 : firstZeroPage = SerialNextPage(serialControl->headPage);
887 : 0 : isNewPage = SerialPagePrecedesLogically(serialControl->headPage,
888 : : targetPage);
889 : : }
890 : :
891 [ # # ]: 0 : if (!TransactionIdIsValid(serialControl->headXid)
892 [ # # ]: 0 : || TransactionIdFollows(xid, serialControl->headXid))
893 : 0 : serialControl->headXid = xid;
894 [ # # ]: 0 : if (isNewPage)
895 : 0 : serialControl->headPage = targetPage;
896 : :
897 [ # # ]: 0 : if (isNewPage)
898 : : {
899 : : /* Initialize intervening pages; might involve trading locks */
900 : : for (;;)
901 : : {
902 : 0 : lock = SimpleLruGetBankLock(SerialSlruCtl, firstZeroPage);
903 : 0 : LWLockAcquire(lock, LW_EXCLUSIVE);
904 : 0 : slotno = SimpleLruZeroPage(SerialSlruCtl, firstZeroPage);
905 [ # # ]: 0 : if (firstZeroPage == targetPage)
906 : 0 : break;
907 [ # # ]: 0 : firstZeroPage = SerialNextPage(firstZeroPage);
908 : 0 : LWLockRelease(lock);
909 : : }
910 : : }
911 : : else
912 : : {
913 : 0 : LWLockAcquire(lock, LW_EXCLUSIVE);
914 : 0 : slotno = SimpleLruReadPage(SerialSlruCtl, targetPage, true, &xid);
915 : : }
916 : :
917 : 0 : SerialValue(slotno, xid) = minConflictCommitSeqNo;
918 : 0 : SerialSlruCtl->shared->page_dirty[slotno] = true;
919 : :
920 : 0 : LWLockRelease(lock);
921 : 0 : LWLockRelease(SerialControlLock);
922 : : }
923 : :
924 : : /*
925 : : * Get the minimum commitSeqNo for any conflict out for the given xid. For
926 : : * a transaction which exists but has no conflict out, InvalidSerCommitSeqNo
927 : : * will be returned.
928 : : */
929 : : static SerCommitSeqNo
930 : 21 : SerialGetMinConflictCommitSeqNo(TransactionId xid)
931 : : {
932 : : TransactionId headXid;
933 : : TransactionId tailXid;
934 : : SerCommitSeqNo val;
935 : : int slotno;
936 : :
937 : : Assert(TransactionIdIsValid(xid));
938 : :
939 : 21 : LWLockAcquire(SerialControlLock, LW_SHARED);
940 : 21 : headXid = serialControl->headXid;
941 : 21 : tailXid = serialControl->tailXid;
942 : 21 : LWLockRelease(SerialControlLock);
943 : :
944 [ + - ]: 21 : if (!TransactionIdIsValid(headXid))
945 : 21 : return 0;
946 : :
947 : : Assert(TransactionIdIsValid(tailXid));
948 : :
949 [ # # ]: 0 : if (TransactionIdPrecedes(xid, tailXid)
950 [ # # ]: 0 : || TransactionIdFollows(xid, headXid))
951 : 0 : return 0;
952 : :
953 : : /*
954 : : * The following function must be called without holding SLRU bank lock,
955 : : * but will return with that lock held, which must then be released.
956 : : */
957 : 0 : slotno = SimpleLruReadPage_ReadOnly(SerialSlruCtl,
958 : 0 : SerialPage(xid), &xid);
959 : 0 : val = SerialValue(slotno, xid);
960 : 0 : LWLockRelease(SimpleLruGetBankLock(SerialSlruCtl, SerialPage(xid)));
961 : 0 : return val;
962 : : }
963 : :
964 : : /*
965 : : * Call this whenever there is a new xmin for active serializable
966 : : * transactions. We don't need to keep information on transactions which
967 : : * precede that. InvalidTransactionId means none active, so everything in
968 : : * the SLRU can be discarded.
969 : : */
970 : : static void
971 : 1777 : SerialSetActiveSerXmin(TransactionId xid)
972 : : {
973 : 1777 : LWLockAcquire(SerialControlLock, LW_EXCLUSIVE);
974 : :
975 : : /*
976 : : * When no sxacts are active, nothing overlaps, set the xid values to
977 : : * invalid to show that there are no valid entries. Don't clear headPage,
978 : : * though. A new xmin might still land on that page, and we don't want to
979 : : * repeatedly zero out the same page.
980 : : */
981 [ + + ]: 1777 : if (!TransactionIdIsValid(xid))
982 : : {
983 : 880 : serialControl->tailXid = InvalidTransactionId;
984 : 880 : serialControl->headXid = InvalidTransactionId;
985 : 880 : LWLockRelease(SerialControlLock);
986 : 880 : return;
987 : : }
988 : :
989 : : /*
990 : : * When we're recovering prepared transactions, the global xmin might move
991 : : * backwards depending on the order they're recovered. Normally that's not
992 : : * OK, but during recovery no serializable transactions will commit, so
993 : : * the SLRU is empty and we can get away with it.
994 : : */
995 [ - + ]: 897 : if (RecoveryInProgress())
996 : : {
997 : : Assert(serialControl->headPage < 0);
998 [ # # ]: 0 : if (!TransactionIdIsValid(serialControl->tailXid)
999 [ # # ]: 0 : || TransactionIdPrecedes(xid, serialControl->tailXid))
1000 : : {
1001 : 0 : serialControl->tailXid = xid;
1002 : : }
1003 : 0 : LWLockRelease(SerialControlLock);
1004 : 0 : return;
1005 : : }
1006 : :
1007 : : Assert(!TransactionIdIsValid(serialControl->tailXid)
1008 : : || TransactionIdFollows(xid, serialControl->tailXid));
1009 : :
1010 : 897 : serialControl->tailXid = xid;
1011 : :
1012 : 897 : LWLockRelease(SerialControlLock);
1013 : : }
1014 : :
1015 : : /*
1016 : : * Perform a checkpoint --- either during shutdown, or on-the-fly
1017 : : *
1018 : : * We don't have any data that needs to survive a restart, but this is a
1019 : : * convenient place to truncate the SLRU.
1020 : : */
1021 : : void
1022 : 1952 : CheckPointPredicate(void)
1023 : : {
1024 : : int64 truncateCutoffPage;
1025 : :
1026 : 1952 : LWLockAcquire(SerialControlLock, LW_EXCLUSIVE);
1027 : :
1028 : : /* Exit quickly if the SLRU is currently not in use. */
1029 [ + - ]: 1952 : if (serialControl->headPage < 0)
1030 : : {
1031 : 1952 : LWLockRelease(SerialControlLock);
1032 : 1952 : return;
1033 : : }
1034 : :
1035 [ # # ]: 0 : if (TransactionIdIsValid(serialControl->tailXid))
1036 : : {
1037 : : int64 tailPage;
1038 : :
1039 : 0 : tailPage = SerialPage(serialControl->tailXid);
1040 : :
1041 : : /*
1042 : : * It is possible for the tailXid to be ahead of the headXid. This
1043 : : * occurs if we checkpoint while there are in-progress serializable
1044 : : * transaction(s) advancing the tail but we are yet to summarize the
1045 : : * transactions. In this case, we cutoff up to the headPage and the
1046 : : * next summary will advance the headXid.
1047 : : */
1048 [ # # ]: 0 : if (SerialPagePrecedesLogically(tailPage, serialControl->headPage))
1049 : : {
1050 : : /* We can truncate the SLRU up to the page containing tailXid */
1051 : 0 : truncateCutoffPage = tailPage;
1052 : : }
1053 : : else
1054 : 0 : truncateCutoffPage = serialControl->headPage;
1055 : : }
1056 : : else
1057 : : {
1058 : : /*----------
1059 : : * The SLRU is no longer needed. Truncate to head before we set head
1060 : : * invalid.
1061 : : *
1062 : : * XXX: It's possible that the SLRU is not needed again until XID
1063 : : * wrap-around has happened, so that the segment containing headPage
1064 : : * that we leave behind will appear to be new again. In that case it
1065 : : * won't be removed until XID horizon advances enough to make it
1066 : : * current again.
1067 : : *
1068 : : * XXX: This should happen in vac_truncate_clog(), not in checkpoints.
1069 : : * Consider this scenario, starting from a system with no in-progress
1070 : : * transactions and VACUUM FREEZE having maximized oldestXact:
1071 : : * - Start a SERIALIZABLE transaction.
1072 : : * - Start, finish, and summarize a SERIALIZABLE transaction, creating
1073 : : * one SLRU page.
1074 : : * - Consume XIDs to reach xidStopLimit.
1075 : : * - Finish all transactions. Due to the long-running SERIALIZABLE
1076 : : * transaction, earlier checkpoints did not touch headPage. The
1077 : : * next checkpoint will change it, but that checkpoint happens after
1078 : : * the end of the scenario.
1079 : : * - VACUUM to advance XID limits.
1080 : : * - Consume ~2M XIDs, crossing the former xidWrapLimit.
1081 : : * - Start, finish, and summarize a SERIALIZABLE transaction.
1082 : : * SerialAdd() declines to create the targetPage, because headPage
1083 : : * is not regarded as in the past relative to that targetPage. The
1084 : : * transaction instigating the summarize fails in
1085 : : * SimpleLruReadPage().
1086 : : */
1087 : 0 : truncateCutoffPage = serialControl->headPage;
1088 : 0 : serialControl->headPage = -1;
1089 : : }
1090 : :
1091 : 0 : LWLockRelease(SerialControlLock);
1092 : :
1093 : : /*
1094 : : * Truncate away pages that are no longer required. Note that no
1095 : : * additional locking is required, because this is only called as part of
1096 : : * a checkpoint, and the validity limits have already been determined.
1097 : : */
1098 : 0 : SimpleLruTruncate(SerialSlruCtl, truncateCutoffPage);
1099 : :
1100 : : /*
1101 : : * Write dirty SLRU pages to disk
1102 : : *
1103 : : * This is not actually necessary from a correctness point of view. We do
1104 : : * it merely as a debugging aid.
1105 : : *
1106 : : * We're doing this after the truncation to avoid writing pages right
1107 : : * before deleting the file in which they sit, which would be completely
1108 : : * pointless.
1109 : : */
1110 : 0 : SimpleLruWriteAll(SerialSlruCtl, true);
1111 : : }
1112 : :
1113 : : /*------------------------------------------------------------------------*/
1114 : :
1115 : : /*
1116 : : * PredicateLockShmemRequest -- Register the predicate locking data structures.
1117 : : */
1118 : : static void
1119 : 1259 : PredicateLockShmemRequest(void *arg)
1120 : : {
1121 : : int64 max_predicate_lock_targets;
1122 : : int64 max_predicate_locks;
1123 : : int64 max_rw_conflicts;
1124 : :
1125 : : /*
1126 : : * Register hash table for PREDICATELOCKTARGET structs. This stores
1127 : : * per-predicate-lock-target information.
1128 : : */
1129 : 1259 : max_predicate_lock_targets = NPREDICATELOCKTARGETENTS();
1130 : :
1131 : 1259 : ShmemRequestHash(.name = "PREDICATELOCKTARGET hash",
1132 : : .nelems = max_predicate_lock_targets,
1133 : : .ptr = &PredicateLockTargetHash,
1134 : : .hash_info.keysize = sizeof(PREDICATELOCKTARGETTAG),
1135 : : .hash_info.entrysize = sizeof(PREDICATELOCKTARGET),
1136 : : .hash_info.num_partitions = NUM_PREDICATELOCK_PARTITIONS,
1137 : : .hash_flags = HASH_ELEM | HASH_BLOBS | HASH_PARTITION | HASH_FIXED_SIZE,
1138 : : );
1139 : :
1140 : : /*
1141 : : * Allocate hash table for PREDICATELOCK structs. This stores per
1142 : : * xact-lock-of-a-target information.
1143 : : *
1144 : : * Assume an average of 2 xacts per target.
1145 : : */
1146 : 1259 : max_predicate_locks = max_predicate_lock_targets * 2;
1147 : :
1148 : 1259 : ShmemRequestHash(.name = "PREDICATELOCK hash",
1149 : : .nelems = max_predicate_locks,
1150 : : .ptr = &PredicateLockHash,
1151 : : .hash_info.keysize = sizeof(PREDICATELOCKTAG),
1152 : : .hash_info.entrysize = sizeof(PREDICATELOCK),
1153 : : .hash_info.hash = predicatelock_hash,
1154 : : .hash_info.num_partitions = NUM_PREDICATELOCK_PARTITIONS,
1155 : : .hash_flags = HASH_ELEM | HASH_FUNCTION | HASH_PARTITION | HASH_FIXED_SIZE,
1156 : : );
1157 : :
1158 : : /*
1159 : : * Compute size for serializable transaction hashtable.
1160 : : *
1161 : : * Assume an average of 10 predicate locking transactions per backend.
1162 : : * This allows aggressive cleanup while detail is present before data must
1163 : : * be summarized for storage in SLRU and the "dummy" transaction.
1164 : : */
1165 : 1259 : max_serializable_xacts = (MaxBackends + max_prepared_xacts) * 10;
1166 : :
1167 : : /*
1168 : : * Register a list to hold information on transactions participating in
1169 : : * predicate locking.
1170 : : */
1171 : 1259 : ShmemRequestStruct(.name = "PredXactList",
1172 : : .size = add_size(PredXactListDataSize,
1173 : : (mul_size((Size) max_serializable_xacts,
1174 : : sizeof(SERIALIZABLEXACT)))),
1175 : : .ptr = (void **) &PredXact,
1176 : : );
1177 : :
1178 : : /*
1179 : : * Register hash table for SERIALIZABLEXID structs. This stores per-xid
1180 : : * information for serializable transactions which have accessed data.
1181 : : */
1182 : 1259 : ShmemRequestHash(.name = "SERIALIZABLEXID hash",
1183 : : .nelems = max_serializable_xacts,
1184 : : .ptr = &SerializableXidHash,
1185 : : .hash_info.keysize = sizeof(SERIALIZABLEXIDTAG),
1186 : : .hash_info.entrysize = sizeof(SERIALIZABLEXID),
1187 : : .hash_flags = HASH_ELEM | HASH_BLOBS | HASH_FIXED_SIZE,
1188 : : );
1189 : :
1190 : : /*
1191 : : * Allocate space for tracking rw-conflicts in lists attached to the
1192 : : * transactions.
1193 : : *
1194 : : * Assume an average of 5 conflicts per transaction. Calculations suggest
1195 : : * that this will prevent resource exhaustion in even the most pessimal
1196 : : * loads up to max_connections = 200 with all 200 connections pounding the
1197 : : * database with serializable transactions. Beyond that, there may be
1198 : : * occasional transactions canceled when trying to flag conflicts. That's
1199 : : * probably OK.
1200 : : */
1201 : 1259 : max_rw_conflicts = max_serializable_xacts * 5;
1202 : :
1203 : 1259 : ShmemRequestStruct(.name = "RWConflictPool",
1204 : : .size = RWConflictPoolHeaderDataSize + mul_size((Size) max_rw_conflicts,
1205 : : RWConflictDataSize),
1206 : : .ptr = (void **) &RWConflictPool,
1207 : : );
1208 : :
1209 : 1259 : ShmemRequestStruct(.name = "FinishedSerializableTransactions",
1210 : : .size = sizeof(dlist_head),
1211 : : .ptr = (void **) &FinishedSerializableTransactions,
1212 : : );
1213 : :
1214 : : /*
1215 : : * Initialize the SLRU storage for old committed serializable
1216 : : * transactions.
1217 : : */
1218 : 1259 : SimpleLruRequest(.desc = &SerialSlruDesc,
1219 : : .name = "serializable",
1220 : : .Dir = "pg_serial",
1221 : : .long_segment_names = false,
1222 : :
1223 : : .nslots = serializable_buffers,
1224 : :
1225 : : .sync_handler = SYNC_HANDLER_NONE,
1226 : : .PagePrecedes = SerialPagePrecedesLogically,
1227 : : .errdetail_for_io_error = serial_errdetail_for_io_error,
1228 : :
1229 : : .buffer_tranche_id = LWTRANCHE_SERIAL_BUFFER,
1230 : : .bank_tranche_id = LWTRANCHE_SERIAL_SLRU,
1231 : : );
1232 : : #ifdef USE_ASSERT_CHECKING
1233 : : SerialPagePrecedesLogicallyUnitTests();
1234 : : #endif
1235 : :
1236 : 1259 : ShmemRequestStruct(.name = "SerialControlData",
1237 : : .size = sizeof(SerialControlData),
1238 : : .ptr = (void **) &serialControl,
1239 : : );
1240 : 1259 : }
1241 : :
1242 : : static void
1243 : 1256 : PredicateLockShmemInit(void *arg)
1244 : : {
1245 : : int max_rw_conflicts;
1246 : : bool found;
1247 : :
1248 : : /*
1249 : : * Reserve a dummy entry in the hash table; we use it to make sure there's
1250 : : * always one entry available when we need to split or combine a page,
1251 : : * because running out of space there could mean aborting a
1252 : : * non-serializable transaction.
1253 : : */
1254 : 1256 : (void) hash_search(PredicateLockTargetHash, &ScratchTargetTag,
1255 : : HASH_ENTER, &found);
1256 : : Assert(!found);
1257 : :
1258 : 1256 : dlist_init(&PredXact->availableList);
1259 : 1256 : dlist_init(&PredXact->activeList);
1260 : 1256 : PredXact->SxactGlobalXmin = InvalidTransactionId;
1261 : 1256 : PredXact->SxactGlobalXminCount = 0;
1262 : 1256 : PredXact->WritableSxactCount = 0;
1263 : 1256 : PredXact->LastSxactCommitSeqNo = FirstNormalSerCommitSeqNo - 1;
1264 : 1256 : PredXact->CanPartialClearThrough = 0;
1265 : 1256 : PredXact->HavePartialClearedThrough = 0;
1266 : 1256 : PredXact->element
1267 : 1256 : = (SERIALIZABLEXACT *) ((char *) PredXact + PredXactListDataSize);
1268 : : /* Add all elements to available list, clean. */
1269 [ + + ]: 1171446 : for (int i = 0; i < max_serializable_xacts; i++)
1270 : : {
1271 : 1170190 : LWLockInitialize(&PredXact->element[i].perXactPredicateListLock,
1272 : : LWTRANCHE_PER_XACT_PREDICATE_LIST);
1273 : 1170190 : dlist_push_tail(&PredXact->availableList, &PredXact->element[i].xactLink);
1274 : : }
1275 : 1256 : PredXact->OldCommittedSxact = CreatePredXact();
1276 : 1256 : SetInvalidVirtualTransactionId(PredXact->OldCommittedSxact->vxid);
1277 : 1256 : PredXact->OldCommittedSxact->prepareSeqNo = 0;
1278 : 1256 : PredXact->OldCommittedSxact->commitSeqNo = 0;
1279 : 1256 : PredXact->OldCommittedSxact->SeqNo.lastCommitBeforeSnapshot = 0;
1280 : 1256 : dlist_init(&PredXact->OldCommittedSxact->outConflicts);
1281 : 1256 : dlist_init(&PredXact->OldCommittedSxact->inConflicts);
1282 : 1256 : dlist_init(&PredXact->OldCommittedSxact->predicateLocks);
1283 : 1256 : dlist_node_init(&PredXact->OldCommittedSxact->finishedLink);
1284 : 1256 : dlist_init(&PredXact->OldCommittedSxact->possibleUnsafeConflicts);
1285 : 1256 : PredXact->OldCommittedSxact->topXid = InvalidTransactionId;
1286 : 1256 : PredXact->OldCommittedSxact->finishedBefore = InvalidTransactionId;
1287 : 1256 : PredXact->OldCommittedSxact->xmin = InvalidTransactionId;
1288 : 1256 : PredXact->OldCommittedSxact->flags = SXACT_FLAG_COMMITTED;
1289 : 1256 : PredXact->OldCommittedSxact->pid = 0;
1290 : 1256 : PredXact->OldCommittedSxact->pgprocno = INVALID_PROC_NUMBER;
1291 : :
1292 : : /* Initialize the rw-conflict pool */
1293 : 1256 : dlist_init(&RWConflictPool->availableList);
1294 : 1256 : RWConflictPool->element = (RWConflict) ((char *) RWConflictPool +
1295 : : RWConflictPoolHeaderDataSize);
1296 : :
1297 : 1256 : max_rw_conflicts = max_serializable_xacts * 5;
1298 : :
1299 : : /* Add all elements to available list, clean. */
1300 [ + + ]: 5852206 : for (int i = 0; i < max_rw_conflicts; i++)
1301 : : {
1302 : 5850950 : dlist_push_tail(&RWConflictPool->availableList,
1303 : 5850950 : &RWConflictPool->element[i].outLink);
1304 : : }
1305 : :
1306 : : /* Initialize the list of finished serializable transactions */
1307 : 1256 : dlist_init(FinishedSerializableTransactions);
1308 : :
1309 : : /* Initialize SerialControl to reflect empty SLRU. */
1310 : 1256 : LWLockAcquire(SerialControlLock, LW_EXCLUSIVE);
1311 : 1256 : serialControl->headPage = -1;
1312 : 1256 : serialControl->headXid = InvalidTransactionId;
1313 : 1256 : serialControl->tailXid = InvalidTransactionId;
1314 : 1256 : LWLockRelease(SerialControlLock);
1315 : :
1316 : : SlruPagePrecedesUnitTests(SerialSlruCtl, SERIAL_ENTRIESPERPAGE);
1317 : :
1318 : : /* This never changes, so let's keep a local copy. */
1319 : 1256 : OldCommittedSxact = PredXact->OldCommittedSxact;
1320 : :
1321 : : /* Pre-calculate the hash and partition lock of the scratch entry */
1322 : 1256 : ScratchTargetTagHash = PredicateLockTargetTagHashCode(&ScratchTargetTag);
1323 : 1256 : ScratchPartitionLock = PredicateLockHashPartitionLock(ScratchTargetTagHash);
1324 : 1256 : }
1325 : :
1326 : : static void
1327 : 0 : PredicateLockShmemAttach(void *arg)
1328 : : {
1329 : : /* This never changes, so let's keep a local copy. */
1330 : 0 : OldCommittedSxact = PredXact->OldCommittedSxact;
1331 : :
1332 : : /* Pre-calculate the hash and partition lock of the scratch entry */
1333 : 0 : ScratchTargetTagHash = PredicateLockTargetTagHashCode(&ScratchTargetTag);
1334 : 0 : ScratchPartitionLock = PredicateLockHashPartitionLock(ScratchTargetTagHash);
1335 : 0 : }
1336 : :
1337 : : /*
1338 : : * Compute the hash code associated with a PREDICATELOCKTAG.
1339 : : *
1340 : : * Because we want to use just one set of partition locks for both the
1341 : : * PREDICATELOCKTARGET and PREDICATELOCK hash tables, we have to make sure
1342 : : * that PREDICATELOCKs fall into the same partition number as their
1343 : : * associated PREDICATELOCKTARGETs. dynahash.c expects the partition number
1344 : : * to be the low-order bits of the hash code, and therefore a
1345 : : * PREDICATELOCKTAG's hash code must have the same low-order bits as the
1346 : : * associated PREDICATELOCKTARGETTAG's hash code. We achieve this with this
1347 : : * specialized hash function.
1348 : : */
1349 : : static uint32
1350 : 0 : predicatelock_hash(const void *key, Size keysize)
1351 : : {
1352 : 0 : const PREDICATELOCKTAG *predicatelocktag = (const PREDICATELOCKTAG *) key;
1353 : : uint32 targethash;
1354 : :
1355 : : Assert(keysize == sizeof(PREDICATELOCKTAG));
1356 : :
1357 : : /* Look into the associated target object, and compute its hash code */
1358 : 0 : targethash = PredicateLockTargetTagHashCode(&predicatelocktag->myTarget->tag);
1359 : :
1360 : 0 : return PredicateLockHashCodeFromTargetHashCode(predicatelocktag, targethash);
1361 : : }
1362 : :
1363 : :
1364 : : /*
1365 : : * GetPredicateLockStatusData
1366 : : * Return a table containing the internal state of the predicate
1367 : : * lock manager for use in pg_lock_status.
1368 : : *
1369 : : * Like GetLockStatusData, this function tries to hold the partition LWLocks
1370 : : * for as short a time as possible by returning two arrays that simply
1371 : : * contain the PREDICATELOCKTARGETTAG and SERIALIZABLEXACT for each lock
1372 : : * table entry. Multiple copies of the same PREDICATELOCKTARGETTAG and
1373 : : * SERIALIZABLEXACT will likely appear.
1374 : : */
1375 : : PredicateLockData *
1376 : 300 : GetPredicateLockStatusData(void)
1377 : : {
1378 : : PredicateLockData *data;
1379 : : int i;
1380 : : int els,
1381 : : el;
1382 : : HASH_SEQ_STATUS seqstat;
1383 : : PREDICATELOCK *predlock;
1384 : :
1385 : 300 : data = palloc_object(PredicateLockData);
1386 : :
1387 : : /*
1388 : : * To ensure consistency, take simultaneous locks on all partition locks
1389 : : * in ascending order, then SerializableXactHashLock.
1390 : : */
1391 [ + + ]: 5100 : for (i = 0; i < NUM_PREDICATELOCK_PARTITIONS; i++)
1392 : 4800 : LWLockAcquire(PredicateLockHashPartitionLockByIndex(i), LW_SHARED);
1393 : 300 : LWLockAcquire(SerializableXactHashLock, LW_SHARED);
1394 : :
1395 : : /* Get number of locks and allocate appropriately-sized arrays. */
1396 : 300 : els = hash_get_num_entries(PredicateLockHash);
1397 : 300 : data->nelements = els;
1398 : 300 : data->locktags = palloc_array(PREDICATELOCKTARGETTAG, els);
1399 : 300 : data->xacts = palloc_array(SERIALIZABLEXACT, els);
1400 : :
1401 : :
1402 : : /* Scan through PredicateLockHash and copy contents */
1403 : 300 : hash_seq_init(&seqstat, PredicateLockHash);
1404 : :
1405 : 300 : el = 0;
1406 : :
1407 [ + + ]: 304 : while ((predlock = (PREDICATELOCK *) hash_seq_search(&seqstat)))
1408 : : {
1409 : 4 : data->locktags[el] = predlock->tag.myTarget->tag;
1410 : 4 : data->xacts[el] = *predlock->tag.myXact;
1411 : 4 : el++;
1412 : : }
1413 : :
1414 : : Assert(el == els);
1415 : :
1416 : : /* Release locks in reverse order */
1417 : 300 : LWLockRelease(SerializableXactHashLock);
1418 [ + + ]: 5100 : for (i = NUM_PREDICATELOCK_PARTITIONS - 1; i >= 0; i--)
1419 : 4800 : LWLockRelease(PredicateLockHashPartitionLockByIndex(i));
1420 : :
1421 : 300 : return data;
1422 : : }
1423 : :
1424 : : /*
1425 : : * Free up shared memory structures by pushing the oldest sxact (the one at
1426 : : * the front of the SummarizeOldestCommittedSxact queue) into summary form.
1427 : : * Each call will free exactly one SERIALIZABLEXACT structure and may also
1428 : : * free one or more of these structures: SERIALIZABLEXID, PREDICATELOCK,
1429 : : * PREDICATELOCKTARGET, RWConflictData.
1430 : : */
1431 : : static void
1432 : 0 : SummarizeOldestCommittedSxact(void)
1433 : : {
1434 : : SERIALIZABLEXACT *sxact;
1435 : :
1436 : 0 : LWLockAcquire(SerializableFinishedListLock, LW_EXCLUSIVE);
1437 : :
1438 : : /*
1439 : : * This function is only called if there are no sxact slots available.
1440 : : * Some of them must belong to old, already-finished transactions, so
1441 : : * there should be something in FinishedSerializableTransactions list that
1442 : : * we can summarize. However, there's a race condition: while we were not
1443 : : * holding any locks, a transaction might have ended and cleaned up all
1444 : : * the finished sxact entries already, freeing up their sxact slots. In
1445 : : * that case, we have nothing to do here. The caller will find one of the
1446 : : * slots released by the other backend when it retries.
1447 : : */
1448 [ # # ]: 0 : if (dlist_is_empty(FinishedSerializableTransactions))
1449 : : {
1450 : 0 : LWLockRelease(SerializableFinishedListLock);
1451 : 0 : return;
1452 : : }
1453 : :
1454 : : /*
1455 : : * Grab the first sxact off the finished list -- this will be the earliest
1456 : : * commit. Remove it from the list.
1457 : : */
1458 : 0 : sxact = dlist_head_element(SERIALIZABLEXACT, finishedLink,
1459 : : FinishedSerializableTransactions);
1460 : 0 : dlist_delete_thoroughly(&sxact->finishedLink);
1461 : :
1462 : : /* Add to SLRU summary information. */
1463 [ # # # # ]: 0 : if (TransactionIdIsValid(sxact->topXid) && !SxactIsReadOnly(sxact))
1464 [ # # ]: 0 : SerialAdd(sxact->topXid, SxactHasConflictOut(sxact)
1465 : : ? sxact->SeqNo.earliestOutConflictCommit : InvalidSerCommitSeqNo);
1466 : :
1467 : : /* Summarize and release the detail. */
1468 : 0 : ReleaseOneSerializableXact(sxact, false, true);
1469 : :
1470 : 0 : LWLockRelease(SerializableFinishedListLock);
1471 : : }
1472 : :
1473 : : /*
1474 : : * GetSafeSnapshot
1475 : : * Obtain and register a snapshot for a READ ONLY DEFERRABLE
1476 : : * transaction. Ensures that the snapshot is "safe", i.e. a
1477 : : * read-only transaction running on it can execute serializably
1478 : : * without further checks. This requires waiting for concurrent
1479 : : * transactions to complete, and retrying with a new snapshot if
1480 : : * one of them could possibly create a conflict.
1481 : : *
1482 : : * As with GetSerializableTransactionSnapshot (which this is a subroutine
1483 : : * for), the passed-in Snapshot pointer should reference a static data
1484 : : * area that can safely be passed to GetSnapshotData.
1485 : : */
1486 : : static Snapshot
1487 : 7 : GetSafeSnapshot(Snapshot origSnapshot)
1488 : : {
1489 : : Snapshot snapshot;
1490 : :
1491 : : Assert(XactReadOnly && XactDeferrable);
1492 : :
1493 : : while (true)
1494 : : {
1495 : : /*
1496 : : * GetSerializableTransactionSnapshotInt is going to call
1497 : : * GetSnapshotData, so we need to provide it the static snapshot area
1498 : : * our caller passed to us. The pointer returned is actually the same
1499 : : * one passed to it, but we avoid assuming that here.
1500 : : */
1501 : 8 : snapshot = GetSerializableTransactionSnapshotInt(origSnapshot,
1502 : : NULL, InvalidPid);
1503 : :
1504 [ + + ]: 8 : if (MySerializableXact == InvalidSerializableXact)
1505 : 6 : return snapshot; /* no concurrent r/w xacts; it's safe */
1506 : :
1507 : 2 : LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
1508 : :
1509 : : /*
1510 : : * Wait for concurrent transactions to finish. Stop early if one of
1511 : : * them marked us as conflicted.
1512 : : */
1513 : 2 : MySerializableXact->flags |= SXACT_FLAG_DEFERRABLE_WAITING;
1514 [ + + ]: 4 : while (!(dlist_is_empty(&MySerializableXact->possibleUnsafeConflicts) ||
1515 [ + - ]: 2 : SxactIsROUnsafe(MySerializableXact)))
1516 : : {
1517 : 2 : LWLockRelease(SerializableXactHashLock);
1518 : 2 : ProcWaitForSignal(WAIT_EVENT_SAFE_SNAPSHOT);
1519 : 2 : LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
1520 : : }
1521 : 2 : MySerializableXact->flags &= ~SXACT_FLAG_DEFERRABLE_WAITING;
1522 : :
1523 [ + + ]: 2 : if (!SxactIsROUnsafe(MySerializableXact))
1524 : : {
1525 : 1 : LWLockRelease(SerializableXactHashLock);
1526 : 1 : break; /* success */
1527 : : }
1528 : :
1529 : 1 : LWLockRelease(SerializableXactHashLock);
1530 : :
1531 : : /* else, need to retry... */
1532 [ - + ]: 1 : ereport(DEBUG2,
1533 : : (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
1534 : : errmsg_internal("deferrable snapshot was unsafe; trying a new one")));
1535 : 1 : ReleasePredicateLocks(false, false);
1536 : : }
1537 : :
1538 : : /*
1539 : : * Now we have a safe snapshot, so we don't need to do any further checks.
1540 : : */
1541 : : Assert(SxactIsROSafe(MySerializableXact));
1542 : 1 : ReleasePredicateLocks(false, true);
1543 : :
1544 : 1 : return snapshot;
1545 : : }
1546 : :
1547 : : /*
1548 : : * GetSafeSnapshotBlockingPids
1549 : : * If the specified process is currently blocked in GetSafeSnapshot,
1550 : : * write the process IDs of all processes that it is blocked by
1551 : : * into the caller-supplied buffer output[]. The list is truncated at
1552 : : * output_size, and the number of PIDs written into the buffer is
1553 : : * returned. Returns zero if the given PID is not currently blocked
1554 : : * in GetSafeSnapshot.
1555 : : */
1556 : : int
1557 : 370 : GetSafeSnapshotBlockingPids(int blocked_pid, int *output, int output_size)
1558 : : {
1559 : 370 : int num_written = 0;
1560 : : dlist_iter iter;
1561 : 370 : SERIALIZABLEXACT *blocking_sxact = NULL;
1562 : :
1563 : 370 : LWLockAcquire(SerializableXactHashLock, LW_SHARED);
1564 : :
1565 : : /* Find blocked_pid's SERIALIZABLEXACT by linear search. */
1566 [ + - + + ]: 840 : dlist_foreach(iter, &PredXact->activeList)
1567 : : {
1568 : 537 : SERIALIZABLEXACT *sxact =
1569 : 537 : dlist_container(SERIALIZABLEXACT, xactLink, iter.cur);
1570 : :
1571 [ + + ]: 537 : if (sxact->pid == blocked_pid)
1572 : : {
1573 : 67 : blocking_sxact = sxact;
1574 : 67 : break;
1575 : : }
1576 : : }
1577 : :
1578 : : /* Did we find it, and is it currently waiting in GetSafeSnapshot? */
1579 [ + + + + ]: 370 : if (blocking_sxact != NULL && SxactIsDeferrableWaiting(blocking_sxact))
1580 : : {
1581 : : /* Traverse the list of possible unsafe conflicts collecting PIDs. */
1582 [ + - + - ]: 2 : dlist_foreach(iter, &blocking_sxact->possibleUnsafeConflicts)
1583 : : {
1584 : 2 : RWConflict possibleUnsafeConflict =
1585 : 2 : dlist_container(RWConflictData, inLink, iter.cur);
1586 : :
1587 : 2 : output[num_written++] = possibleUnsafeConflict->sxactOut->pid;
1588 : :
1589 [ + - ]: 2 : if (num_written >= output_size)
1590 : 2 : break;
1591 : : }
1592 : : }
1593 : :
1594 : 370 : LWLockRelease(SerializableXactHashLock);
1595 : :
1596 : 370 : return num_written;
1597 : : }
1598 : :
1599 : : /*
1600 : : * Acquire a snapshot that can be used for the current transaction.
1601 : : *
1602 : : * Make sure we have a SERIALIZABLEXACT reference in MySerializableXact.
1603 : : * It should be current for this process and be contained in PredXact.
1604 : : *
1605 : : * The passed-in Snapshot pointer should reference a static data area that
1606 : : * can safely be passed to GetSnapshotData. The return value is actually
1607 : : * always this same pointer; no new snapshot data structure is allocated
1608 : : * within this function.
1609 : : */
1610 : : Snapshot
1611 : 1691 : GetSerializableTransactionSnapshot(Snapshot snapshot)
1612 : : {
1613 : : Assert(IsolationIsSerializable());
1614 : :
1615 : : /*
1616 : : * Can't use serializable mode while recovery is still active, as it is,
1617 : : * for example, on a hot standby. We could get here despite the check in
1618 : : * check_transaction_isolation() if default_transaction_isolation is set
1619 : : * to serializable, so phrase the hint accordingly.
1620 : : */
1621 [ - + ]: 1691 : if (RecoveryInProgress())
1622 [ # # ]: 0 : ereport(ERROR,
1623 : : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1624 : : errmsg("cannot use serializable mode in a hot standby"),
1625 : : errdetail("\"default_transaction_isolation\" is set to \"serializable\"."),
1626 : : errhint("You can use \"SET default_transaction_isolation = 'repeatable read'\" to change the default.")));
1627 : :
1628 : : /*
1629 : : * A special optimization is available for SERIALIZABLE READ ONLY
1630 : : * DEFERRABLE transactions -- we can wait for a suitable snapshot and
1631 : : * thereby avoid all SSI overhead once it's running.
1632 : : */
1633 [ + + + + ]: 1691 : if (XactReadOnly && XactDeferrable)
1634 : 7 : return GetSafeSnapshot(snapshot);
1635 : :
1636 : 1684 : return GetSerializableTransactionSnapshotInt(snapshot,
1637 : : NULL, InvalidPid);
1638 : : }
1639 : :
1640 : : /*
1641 : : * Import a snapshot to be used for the current transaction.
1642 : : *
1643 : : * This is nearly the same as GetSerializableTransactionSnapshot, except that
1644 : : * we don't take a new snapshot, but rather use the data we're handed.
1645 : : *
1646 : : * The caller must have verified that the snapshot came from a serializable
1647 : : * transaction; and if we're read-write, the source transaction must not be
1648 : : * read-only.
1649 : : */
1650 : : void
1651 : 13 : SetSerializableTransactionSnapshot(Snapshot snapshot,
1652 : : VirtualTransactionId *sourcevxid,
1653 : : int sourcepid)
1654 : : {
1655 : : Assert(IsolationIsSerializable());
1656 : :
1657 : : /*
1658 : : * If this is called by parallel.c in a parallel worker, we don't want to
1659 : : * create a SERIALIZABLEXACT just yet because the leader's
1660 : : * SERIALIZABLEXACT will be installed with AttachSerializableXact(). We
1661 : : * also don't want to reject SERIALIZABLE READ ONLY DEFERRABLE in this
1662 : : * case, because the leader has already determined that the snapshot it
1663 : : * has passed us is safe. So there is nothing for us to do.
1664 : : */
1665 [ + - ]: 13 : if (IsParallelWorker())
1666 : 13 : return;
1667 : :
1668 : : /*
1669 : : * We do not allow SERIALIZABLE READ ONLY DEFERRABLE transactions to
1670 : : * import snapshots, since there's no way to wait for a safe snapshot when
1671 : : * we're using the snap we're told to. (XXX instead of throwing an error,
1672 : : * we could just ignore the XactDeferrable flag?)
1673 : : */
1674 [ # # # # ]: 0 : if (XactReadOnly && XactDeferrable)
1675 [ # # ]: 0 : ereport(ERROR,
1676 : : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1677 : : errmsg("a snapshot-importing transaction must not be READ ONLY DEFERRABLE")));
1678 : :
1679 : 0 : (void) GetSerializableTransactionSnapshotInt(snapshot, sourcevxid,
1680 : : sourcepid);
1681 : : }
1682 : :
1683 : : /*
1684 : : * Guts of GetSerializableTransactionSnapshot
1685 : : *
1686 : : * If sourcevxid is valid, this is actually an import operation and we should
1687 : : * skip calling GetSnapshotData, because the snapshot contents are already
1688 : : * loaded up. HOWEVER: to avoid race conditions, we must check that the
1689 : : * source xact is still running after we acquire SerializableXactHashLock.
1690 : : * We do that by calling ProcArrayInstallImportedXmin.
1691 : : */
1692 : : static Snapshot
1693 : 1692 : GetSerializableTransactionSnapshotInt(Snapshot snapshot,
1694 : : VirtualTransactionId *sourcevxid,
1695 : : int sourcepid)
1696 : : {
1697 : : PGPROC *proc;
1698 : : VirtualTransactionId vxid;
1699 : : SERIALIZABLEXACT *sxact,
1700 : : *othersxact;
1701 : :
1702 : : /* We only do this for serializable transactions. Once. */
1703 : : Assert(MySerializableXact == InvalidSerializableXact);
1704 : :
1705 : : Assert(!RecoveryInProgress());
1706 : :
1707 : : /*
1708 : : * Since all parts of a serializable transaction must use the same
1709 : : * snapshot, it is too late to establish one after a parallel operation
1710 : : * has begun.
1711 : : */
1712 [ - + ]: 1692 : if (IsInParallelMode())
1713 [ # # ]: 0 : elog(ERROR, "cannot establish serializable snapshot during a parallel operation");
1714 : :
1715 : 1692 : proc = MyProc;
1716 : : Assert(proc != NULL);
1717 : 1692 : GET_VXID_FROM_PGPROC(vxid, *proc);
1718 : :
1719 : : /*
1720 : : * First we get the sxact structure, which may involve looping and access
1721 : : * to the "finished" list to free a structure for use.
1722 : : *
1723 : : * We must hold SerializableXactHashLock when taking/checking the snapshot
1724 : : * to avoid race conditions, for much the same reasons that
1725 : : * GetSnapshotData takes the ProcArrayLock. Since we might have to
1726 : : * release SerializableXactHashLock to call SummarizeOldestCommittedSxact,
1727 : : * this means we have to create the sxact first, which is a bit annoying
1728 : : * (in particular, an elog(ERROR) in procarray.c would cause us to leak
1729 : : * the sxact). Consider refactoring to avoid this.
1730 : : */
1731 : : #ifdef TEST_SUMMARIZE_SERIAL
1732 : : SummarizeOldestCommittedSxact();
1733 : : #endif
1734 : 1692 : LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
1735 : : do
1736 : : {
1737 : 1692 : sxact = CreatePredXact();
1738 : : /* If null, push out committed sxact to SLRU summary & retry. */
1739 [ - + ]: 1692 : if (!sxact)
1740 : : {
1741 : 0 : LWLockRelease(SerializableXactHashLock);
1742 : 0 : SummarizeOldestCommittedSxact();
1743 : 0 : LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
1744 : : }
1745 [ - + ]: 1692 : } while (!sxact);
1746 : :
1747 : : /* Get the snapshot, or check that it's safe to use */
1748 [ + - ]: 1692 : if (!sourcevxid)
1749 : 1692 : snapshot = GetSnapshotData(snapshot);
1750 [ # # ]: 0 : else if (!ProcArrayInstallImportedXmin(snapshot->xmin, sourcevxid))
1751 : : {
1752 : 0 : ReleasePredXact(sxact);
1753 : 0 : LWLockRelease(SerializableXactHashLock);
1754 [ # # ]: 0 : ereport(ERROR,
1755 : : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
1756 : : errmsg("could not import the requested snapshot"),
1757 : : errdetail("The source process with PID %d is not running anymore.",
1758 : : sourcepid)));
1759 : : }
1760 : :
1761 : : /*
1762 : : * If there are no serializable transactions which are not read-only, we
1763 : : * can "opt out" of predicate locking and conflict checking for a
1764 : : * read-only transaction.
1765 : : *
1766 : : * The reason this is safe is that a read-only transaction can only become
1767 : : * part of a dangerous structure if it overlaps a writable transaction
1768 : : * which in turn overlaps a writable transaction which committed before
1769 : : * the read-only transaction started. A new writable transaction can
1770 : : * overlap this one, but it can't meet the other condition of overlapping
1771 : : * a transaction which committed before this one started.
1772 : : */
1773 [ + + + + ]: 1692 : if (XactReadOnly && PredXact->WritableSxactCount == 0)
1774 : : {
1775 : 116 : ReleasePredXact(sxact);
1776 : 116 : LWLockRelease(SerializableXactHashLock);
1777 : 116 : return snapshot;
1778 : : }
1779 : :
1780 : : /* Initialize the structure. */
1781 : 1576 : sxact->vxid = vxid;
1782 : 1576 : sxact->SeqNo.lastCommitBeforeSnapshot = PredXact->LastSxactCommitSeqNo;
1783 : 1576 : sxact->prepareSeqNo = InvalidSerCommitSeqNo;
1784 : 1576 : sxact->commitSeqNo = InvalidSerCommitSeqNo;
1785 : 1576 : dlist_init(&(sxact->outConflicts));
1786 : 1576 : dlist_init(&(sxact->inConflicts));
1787 : 1576 : dlist_init(&(sxact->possibleUnsafeConflicts));
1788 : 1576 : sxact->topXid = GetTopTransactionIdIfAny();
1789 : 1576 : sxact->finishedBefore = InvalidTransactionId;
1790 : 1576 : sxact->xmin = snapshot->xmin;
1791 : 1576 : sxact->pid = MyProcPid;
1792 : 1576 : sxact->pgprocno = MyProcNumber;
1793 : 1576 : dlist_init(&sxact->predicateLocks);
1794 : 1576 : dlist_node_init(&sxact->finishedLink);
1795 : 1576 : sxact->flags = 0;
1796 [ + + ]: 1576 : if (XactReadOnly)
1797 : : {
1798 : : dlist_iter iter;
1799 : :
1800 : 107 : sxact->flags |= SXACT_FLAG_READ_ONLY;
1801 : :
1802 : : /*
1803 : : * Register all concurrent r/w transactions as possible conflicts; if
1804 : : * all of them commit without any outgoing conflicts to earlier
1805 : : * transactions then this snapshot can be deemed safe (and we can run
1806 : : * without tracking predicate locks).
1807 : : */
1808 [ + - + + ]: 468 : dlist_foreach(iter, &PredXact->activeList)
1809 : : {
1810 : 361 : othersxact = dlist_container(SERIALIZABLEXACT, xactLink, iter.cur);
1811 : :
1812 [ + + ]: 361 : if (!SxactIsCommitted(othersxact)
1813 [ + - ]: 241 : && !SxactIsDoomed(othersxact)
1814 [ + + ]: 241 : && !SxactIsReadOnly(othersxact))
1815 : : {
1816 : 133 : SetPossibleUnsafeConflict(sxact, othersxact);
1817 : : }
1818 : : }
1819 : :
1820 : : /*
1821 : : * If we didn't find any possibly unsafe conflicts because every
1822 : : * uncommitted writable transaction turned out to be doomed, then we
1823 : : * can "opt out" immediately. See comments above the earlier check
1824 : : * for PredXact->WritableSxactCount == 0.
1825 : : */
1826 [ - + ]: 107 : if (dlist_is_empty(&sxact->possibleUnsafeConflicts))
1827 : : {
1828 : 0 : ReleasePredXact(sxact);
1829 : 0 : LWLockRelease(SerializableXactHashLock);
1830 : 0 : return snapshot;
1831 : : }
1832 : : }
1833 : : else
1834 : : {
1835 : 1469 : ++(PredXact->WritableSxactCount);
1836 : : Assert(PredXact->WritableSxactCount <=
1837 : : (MaxBackends + max_prepared_xacts));
1838 : : }
1839 : :
1840 : : /* Maintain serializable global xmin info. */
1841 [ + + ]: 1576 : if (!TransactionIdIsValid(PredXact->SxactGlobalXmin))
1842 : : {
1843 : : Assert(PredXact->SxactGlobalXminCount == 0);
1844 : 880 : PredXact->SxactGlobalXmin = snapshot->xmin;
1845 : 880 : PredXact->SxactGlobalXminCount = 1;
1846 : 880 : SerialSetActiveSerXmin(snapshot->xmin);
1847 : : }
1848 [ + + ]: 696 : else if (TransactionIdEquals(snapshot->xmin, PredXact->SxactGlobalXmin))
1849 : : {
1850 : : Assert(PredXact->SxactGlobalXminCount > 0);
1851 : 660 : PredXact->SxactGlobalXminCount++;
1852 : : }
1853 : : else
1854 : : {
1855 : : Assert(TransactionIdFollows(snapshot->xmin, PredXact->SxactGlobalXmin));
1856 : : }
1857 : :
1858 : 1576 : MySerializableXact = sxact;
1859 : 1576 : MyXactDidWrite = false; /* haven't written anything yet */
1860 : :
1861 : 1576 : LWLockRelease(SerializableXactHashLock);
1862 : :
1863 : 1576 : CreateLocalPredicateLockHash();
1864 : :
1865 : 1576 : return snapshot;
1866 : : }
1867 : :
1868 : : static void
1869 : 1589 : CreateLocalPredicateLockHash(void)
1870 : : {
1871 : : HASHCTL hash_ctl;
1872 : :
1873 : : /* Initialize the backend-local hash table of parent locks */
1874 : : Assert(LocalPredicateLockHash == NULL);
1875 : 1589 : hash_ctl.keysize = sizeof(PREDICATELOCKTARGETTAG);
1876 : 1589 : hash_ctl.entrysize = sizeof(LOCALPREDICATELOCK);
1877 : 1589 : LocalPredicateLockHash = hash_create("Local predicate lock",
1878 : : max_predicate_locks_per_xact,
1879 : : &hash_ctl,
1880 : : HASH_ELEM | HASH_BLOBS);
1881 : 1589 : }
1882 : :
1883 : : /*
1884 : : * Register the top level XID in SerializableXidHash.
1885 : : * Also store it for easy reference in MySerializableXact.
1886 : : */
1887 : : void
1888 : 169922 : RegisterPredicateLockingXid(TransactionId xid)
1889 : : {
1890 : : SERIALIZABLEXIDTAG sxidtag;
1891 : : SERIALIZABLEXID *sxid;
1892 : : bool found;
1893 : :
1894 : : /*
1895 : : * If we're not tracking predicate lock data for this transaction, we
1896 : : * should ignore the request and return quickly.
1897 : : */
1898 [ + + ]: 169922 : if (MySerializableXact == InvalidSerializableXact)
1899 : 168620 : return;
1900 : :
1901 : : /* We should have a valid XID and be at the top level. */
1902 : : Assert(TransactionIdIsValid(xid));
1903 : :
1904 : 1302 : LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
1905 : :
1906 : : /* This should only be done once per transaction. */
1907 : : Assert(MySerializableXact->topXid == InvalidTransactionId);
1908 : :
1909 : 1302 : MySerializableXact->topXid = xid;
1910 : :
1911 : 1302 : sxidtag.xid = xid;
1912 : 1302 : sxid = (SERIALIZABLEXID *) hash_search(SerializableXidHash,
1913 : : &sxidtag,
1914 : : HASH_ENTER, &found);
1915 : : Assert(!found);
1916 : :
1917 : : /* Initialize the structure. */
1918 : 1302 : sxid->myXact = MySerializableXact;
1919 : 1302 : LWLockRelease(SerializableXactHashLock);
1920 : : }
1921 : :
1922 : :
1923 : : /*
1924 : : * Check whether there are any predicate locks held by any transaction
1925 : : * for the page at the given block number.
1926 : : *
1927 : : * Note that the transaction may be completed but not yet subject to
1928 : : * cleanup due to overlapping serializable transactions. This must
1929 : : * return valid information regardless of transaction isolation level.
1930 : : *
1931 : : * Also note that this doesn't check for a conflicting relation lock,
1932 : : * just a lock specifically on the given page.
1933 : : *
1934 : : * One use is to support proper behavior during GiST index vacuum.
1935 : : */
1936 : : bool
1937 : 0 : PageIsPredicateLocked(Relation relation, BlockNumber blkno)
1938 : : {
1939 : : PREDICATELOCKTARGETTAG targettag;
1940 : : uint32 targettaghash;
1941 : : LWLock *partitionLock;
1942 : : PREDICATELOCKTARGET *target;
1943 : :
1944 : 0 : SET_PREDICATELOCKTARGETTAG_PAGE(targettag,
1945 : : relation->rd_locator.dbOid,
1946 : : relation->rd_id,
1947 : : blkno);
1948 : :
1949 : 0 : targettaghash = PredicateLockTargetTagHashCode(&targettag);
1950 : 0 : partitionLock = PredicateLockHashPartitionLock(targettaghash);
1951 : 0 : LWLockAcquire(partitionLock, LW_SHARED);
1952 : : target = (PREDICATELOCKTARGET *)
1953 : 0 : hash_search_with_hash_value(PredicateLockTargetHash,
1954 : : &targettag, targettaghash,
1955 : : HASH_FIND, NULL);
1956 : 0 : LWLockRelease(partitionLock);
1957 : :
1958 : 0 : return (target != NULL);
1959 : : }
1960 : :
1961 : :
1962 : : /*
1963 : : * Check whether a particular lock is held by this transaction.
1964 : : *
1965 : : * Important note: this function may return false even if the lock is
1966 : : * being held, because it uses the local lock table which is not
1967 : : * updated if another transaction modifies our lock list (e.g. to
1968 : : * split an index page). It can also return true when a coarser
1969 : : * granularity lock that covers this target is being held. Be careful
1970 : : * to only use this function in circumstances where such errors are
1971 : : * acceptable!
1972 : : */
1973 : : static bool
1974 : 41896 : PredicateLockExists(const PREDICATELOCKTARGETTAG *targettag)
1975 : : {
1976 : : LOCALPREDICATELOCK *lock;
1977 : :
1978 : : /* check local hash table */
1979 : 41896 : lock = (LOCALPREDICATELOCK *) hash_search(LocalPredicateLockHash,
1980 : : targettag,
1981 : : HASH_FIND, NULL);
1982 : :
1983 [ + + ]: 41896 : if (!lock)
1984 : 12752 : return false;
1985 : :
1986 : : /*
1987 : : * Found entry in the table, but still need to check whether it's actually
1988 : : * held -- it could just be a parent of some held lock.
1989 : : */
1990 : 29144 : return lock->held;
1991 : : }
1992 : :
1993 : : /*
1994 : : * Return the parent lock tag in the lock hierarchy: the next coarser
1995 : : * lock that covers the provided tag.
1996 : : *
1997 : : * Returns true and sets *parent to the parent tag if one exists,
1998 : : * returns false if none exists.
1999 : : */
2000 : : static bool
2001 : 25390 : GetParentPredicateLockTag(const PREDICATELOCKTARGETTAG *tag,
2002 : : PREDICATELOCKTARGETTAG *parent)
2003 : : {
2004 [ + + + + : 25390 : switch (GET_PREDICATELOCKTARGETTAG_TYPE(*tag))
+ - ]
2005 : : {
2006 : 8967 : case PREDLOCKTAG_RELATION:
2007 : : /* relation locks have no parent lock */
2008 : 8967 : return false;
2009 : :
2010 : 7553 : case PREDLOCKTAG_PAGE:
2011 : : /* parent lock is relation lock */
2012 : 7553 : SET_PREDICATELOCKTARGETTAG_RELATION(*parent,
2013 : : GET_PREDICATELOCKTARGETTAG_DB(*tag),
2014 : : GET_PREDICATELOCKTARGETTAG_RELATION(*tag));
2015 : :
2016 : 7553 : return true;
2017 : :
2018 : 8870 : case PREDLOCKTAG_TUPLE:
2019 : : /* parent lock is page lock */
2020 : 8870 : SET_PREDICATELOCKTARGETTAG_PAGE(*parent,
2021 : : GET_PREDICATELOCKTARGETTAG_DB(*tag),
2022 : : GET_PREDICATELOCKTARGETTAG_RELATION(*tag),
2023 : : GET_PREDICATELOCKTARGETTAG_PAGE(*tag));
2024 : 8870 : return true;
2025 : : }
2026 : :
2027 : : /* not reachable */
2028 : : Assert(false);
2029 : 0 : return false;
2030 : : }
2031 : :
2032 : : /*
2033 : : * Check whether the lock we are considering is already covered by a
2034 : : * coarser lock for our transaction.
2035 : : *
2036 : : * Like PredicateLockExists, this function might return a false
2037 : : * negative, but it will never return a false positive.
2038 : : */
2039 : : static bool
2040 : 8608 : CoarserLockCovers(const PREDICATELOCKTARGETTAG *newtargettag)
2041 : : {
2042 : : PREDICATELOCKTARGETTAG targettag,
2043 : : parenttag;
2044 : :
2045 : 8608 : targettag = *newtargettag;
2046 : :
2047 : : /* check parents iteratively until no more */
2048 [ + + ]: 13416 : while (GetParentPredicateLockTag(&targettag, &parenttag))
2049 : : {
2050 : 9469 : targettag = parenttag;
2051 [ + + ]: 9469 : if (PredicateLockExists(&targettag))
2052 : 4661 : return true;
2053 : : }
2054 : :
2055 : : /* no more parents to check; lock is not covered */
2056 : 3947 : return false;
2057 : : }
2058 : :
2059 : : /*
2060 : : * Remove the dummy entry from the predicate lock target hash, to free up some
2061 : : * scratch space. The caller must be holding SerializablePredicateListLock,
2062 : : * and must restore the entry with RestoreScratchTarget() before releasing the
2063 : : * lock.
2064 : : *
2065 : : * If lockheld is true, the caller is already holding the partition lock
2066 : : * of the partition containing the scratch entry.
2067 : : */
2068 : : static void
2069 : 49 : RemoveScratchTarget(bool lockheld)
2070 : : {
2071 : : bool found;
2072 : :
2073 : : Assert(LWLockHeldByMe(SerializablePredicateListLock));
2074 : :
2075 [ - + ]: 49 : if (!lockheld)
2076 : 0 : LWLockAcquire(ScratchPartitionLock, LW_EXCLUSIVE);
2077 : 49 : hash_search_with_hash_value(PredicateLockTargetHash,
2078 : : &ScratchTargetTag,
2079 : : ScratchTargetTagHash,
2080 : : HASH_REMOVE, &found);
2081 : : Assert(found);
2082 [ - + ]: 49 : if (!lockheld)
2083 : 0 : LWLockRelease(ScratchPartitionLock);
2084 : 49 : }
2085 : :
2086 : : /*
2087 : : * Re-insert the dummy entry in predicate lock target hash.
2088 : : */
2089 : : static void
2090 : 49 : RestoreScratchTarget(bool lockheld)
2091 : : {
2092 : : bool found;
2093 : :
2094 : : Assert(LWLockHeldByMe(SerializablePredicateListLock));
2095 : :
2096 [ - + ]: 49 : if (!lockheld)
2097 : 0 : LWLockAcquire(ScratchPartitionLock, LW_EXCLUSIVE);
2098 : 49 : hash_search_with_hash_value(PredicateLockTargetHash,
2099 : : &ScratchTargetTag,
2100 : : ScratchTargetTagHash,
2101 : : HASH_ENTER, &found);
2102 : : Assert(!found);
2103 [ - + ]: 49 : if (!lockheld)
2104 : 0 : LWLockRelease(ScratchPartitionLock);
2105 : 49 : }
2106 : :
2107 : : /*
2108 : : * Check whether the list of related predicate locks is empty for a
2109 : : * predicate lock target, and remove the target if it is.
2110 : : */
2111 : : static void
2112 : 3941 : RemoveTargetIfNoLongerUsed(PREDICATELOCKTARGET *target, uint32 targettaghash)
2113 : : {
2114 : : PREDICATELOCKTARGET *rmtarget PG_USED_FOR_ASSERTS_ONLY;
2115 : :
2116 : : Assert(LWLockHeldByMe(SerializablePredicateListLock));
2117 : :
2118 : : /* Can't remove it until no locks at this target. */
2119 [ + + ]: 3941 : if (!dlist_is_empty(&target->predicateLocks))
2120 : 973 : return;
2121 : :
2122 : : /* Actually remove the target. */
2123 : 2968 : rmtarget = hash_search_with_hash_value(PredicateLockTargetHash,
2124 : 2968 : &target->tag,
2125 : : targettaghash,
2126 : : HASH_REMOVE, NULL);
2127 : : Assert(rmtarget == target);
2128 : : }
2129 : :
2130 : : /*
2131 : : * Delete child target locks owned by this process.
2132 : : * This implementation is assuming that the usage of each target tag field
2133 : : * is uniform. No need to make this hard if we don't have to.
2134 : : *
2135 : : * We acquire an LWLock in the case of parallel mode, because worker
2136 : : * backends have access to the leader's SERIALIZABLEXACT. Otherwise,
2137 : : * we aren't acquiring LWLocks for the predicate lock or lock
2138 : : * target structures associated with this transaction unless we're going
2139 : : * to modify them, because no other process is permitted to modify our
2140 : : * locks.
2141 : : */
2142 : : static void
2143 : 2379 : DeleteChildTargetLocks(const PREDICATELOCKTARGETTAG *newtargettag)
2144 : : {
2145 : : SERIALIZABLEXACT *sxact;
2146 : : PREDICATELOCK *predlock;
2147 : : dlist_mutable_iter iter;
2148 : :
2149 : 2379 : LWLockAcquire(SerializablePredicateListLock, LW_SHARED);
2150 : 2379 : sxact = MySerializableXact;
2151 [ + + ]: 2379 : if (IsInParallelMode())
2152 : 11 : LWLockAcquire(&sxact->perXactPredicateListLock, LW_EXCLUSIVE);
2153 : :
2154 [ + - + + ]: 7527 : dlist_foreach_modify(iter, &sxact->predicateLocks)
2155 : : {
2156 : : PREDICATELOCKTAG oldlocktag;
2157 : : PREDICATELOCKTARGET *oldtarget;
2158 : : PREDICATELOCKTARGETTAG oldtargettag;
2159 : :
2160 : 5148 : predlock = dlist_container(PREDICATELOCK, xactLink, iter.cur);
2161 : :
2162 : 5148 : oldlocktag = predlock->tag;
2163 : : Assert(oldlocktag.myXact == sxact);
2164 : 5148 : oldtarget = oldlocktag.myTarget;
2165 : 5148 : oldtargettag = oldtarget->tag;
2166 : :
2167 [ + + + - : 5148 : if (TargetTagIsCoveredBy(oldtargettag, *newtargettag))
+ + + + +
+ - + +
- ]
2168 : : {
2169 : : uint32 oldtargettaghash;
2170 : : LWLock *partitionLock;
2171 : : PREDICATELOCK *rmpredlock PG_USED_FOR_ASSERTS_ONLY;
2172 : :
2173 : 679 : oldtargettaghash = PredicateLockTargetTagHashCode(&oldtargettag);
2174 : 679 : partitionLock = PredicateLockHashPartitionLock(oldtargettaghash);
2175 : :
2176 : 679 : LWLockAcquire(partitionLock, LW_EXCLUSIVE);
2177 : :
2178 : 679 : dlist_delete(&predlock->xactLink);
2179 : 679 : dlist_delete(&predlock->targetLink);
2180 : 679 : rmpredlock = hash_search_with_hash_value
2181 : : (PredicateLockHash,
2182 : : &oldlocktag,
2183 : 679 : PredicateLockHashCodeFromTargetHashCode(&oldlocktag,
2184 : : oldtargettaghash),
2185 : : HASH_REMOVE, NULL);
2186 : : Assert(rmpredlock == predlock);
2187 : :
2188 : 679 : RemoveTargetIfNoLongerUsed(oldtarget, oldtargettaghash);
2189 : :
2190 : 679 : LWLockRelease(partitionLock);
2191 : :
2192 : 679 : DecrementParentLocks(&oldtargettag);
2193 : : }
2194 : : }
2195 [ + + ]: 2379 : if (IsInParallelMode())
2196 : 11 : LWLockRelease(&sxact->perXactPredicateListLock);
2197 : 2379 : LWLockRelease(SerializablePredicateListLock);
2198 : 2379 : }
2199 : :
2200 : : /*
2201 : : * Returns the promotion limit for a given predicate lock target. This is the
2202 : : * max number of descendant locks allowed before promoting to the specified
2203 : : * tag. Note that the limit includes non-direct descendants (e.g., both tuples
2204 : : * and pages for a relation lock).
2205 : : *
2206 : : * Currently the default limit is 2 for a page lock, and half of the value of
2207 : : * max_pred_locks_per_transaction - 1 for a relation lock, to match behavior
2208 : : * of earlier releases when upgrading.
2209 : : *
2210 : : * TODO SSI: We should probably add additional GUCs to allow a maximum ratio
2211 : : * of page and tuple locks based on the pages in a relation, and the maximum
2212 : : * ratio of tuple locks to tuples in a page. This would provide more
2213 : : * generally "balanced" allocation of locks to where they are most useful,
2214 : : * while still allowing the absolute numbers to prevent one relation from
2215 : : * tying up all predicate lock resources.
2216 : : */
2217 : : static int
2218 : 4808 : MaxPredicateChildLocks(const PREDICATELOCKTARGETTAG *tag)
2219 : : {
2220 [ + - + + : 4808 : switch (GET_PREDICATELOCKTARGETTAG_TYPE(*tag))
- - ]
2221 : : {
2222 : 3240 : case PREDLOCKTAG_RELATION:
2223 : 3240 : return max_predicate_locks_per_relation < 0
2224 : : ? (max_predicate_locks_per_xact
2225 : 3240 : / (-max_predicate_locks_per_relation)) - 1
2226 [ + - ]: 3240 : : max_predicate_locks_per_relation;
2227 : :
2228 : 1568 : case PREDLOCKTAG_PAGE:
2229 : 1568 : return max_predicate_locks_per_page;
2230 : :
2231 : 0 : case PREDLOCKTAG_TUPLE:
2232 : :
2233 : : /*
2234 : : * not reachable: nothing is finer-granularity than a tuple, so we
2235 : : * should never try to promote to it.
2236 : : */
2237 : : Assert(false);
2238 : 0 : return 0;
2239 : : }
2240 : :
2241 : : /* not reachable */
2242 : : Assert(false);
2243 : 0 : return 0;
2244 : : }
2245 : :
2246 : : /*
2247 : : * For all ancestors of a newly-acquired predicate lock, increment
2248 : : * their child count in the parent hash table. If any of them have
2249 : : * more descendants than their promotion threshold, acquire the
2250 : : * coarsest such lock.
2251 : : *
2252 : : * Returns true if a parent lock was acquired and false otherwise.
2253 : : */
2254 : : static bool
2255 : 3947 : CheckAndPromotePredicateLockRequest(const PREDICATELOCKTARGETTAG *reqtag)
2256 : : {
2257 : : PREDICATELOCKTARGETTAG targettag,
2258 : : nexttag,
2259 : : promotiontag;
2260 : : LOCALPREDICATELOCK *parentlock;
2261 : : bool found,
2262 : : promote;
2263 : :
2264 : 3947 : promote = false;
2265 : :
2266 : 3947 : targettag = *reqtag;
2267 : :
2268 : : /* check parents iteratively */
2269 [ + + ]: 12702 : while (GetParentPredicateLockTag(&targettag, &nexttag))
2270 : : {
2271 : 4808 : targettag = nexttag;
2272 : 4808 : parentlock = (LOCALPREDICATELOCK *) hash_search(LocalPredicateLockHash,
2273 : : &targettag,
2274 : : HASH_ENTER,
2275 : : &found);
2276 [ + + ]: 4808 : if (!found)
2277 : : {
2278 : 3387 : parentlock->held = false;
2279 : 3387 : parentlock->childLocks = 1;
2280 : : }
2281 : : else
2282 : 1421 : parentlock->childLocks++;
2283 : :
2284 [ + + ]: 4808 : if (parentlock->childLocks >
2285 : 4808 : MaxPredicateChildLocks(&targettag))
2286 : : {
2287 : : /*
2288 : : * We should promote to this parent lock. Continue to check its
2289 : : * ancestors, however, both to get their child counts right and to
2290 : : * check whether we should just go ahead and promote to one of
2291 : : * them.
2292 : : */
2293 : 173 : promotiontag = targettag;
2294 : 173 : promote = true;
2295 : : }
2296 : : }
2297 : :
2298 [ + + ]: 3947 : if (promote)
2299 : : {
2300 : : /* acquire coarsest ancestor eligible for promotion */
2301 : 173 : PredicateLockAcquire(&promotiontag);
2302 : 173 : return true;
2303 : : }
2304 : : else
2305 : 3774 : return false;
2306 : : }
2307 : :
2308 : : /*
2309 : : * When releasing a lock, decrement the child count on all ancestor
2310 : : * locks.
2311 : : *
2312 : : * This is called only when releasing a lock via
2313 : : * DeleteChildTargetLocks (i.e. when a lock becomes redundant because
2314 : : * we've acquired its parent, possibly due to promotion) or when a new
2315 : : * MVCC write lock makes the predicate lock unnecessary. There's no
2316 : : * point in calling it when locks are released at transaction end, as
2317 : : * this information is no longer needed.
2318 : : */
2319 : : static void
2320 : 1073 : DecrementParentLocks(const PREDICATELOCKTARGETTAG *targettag)
2321 : : {
2322 : : PREDICATELOCKTARGETTAG parenttag,
2323 : : nexttag;
2324 : :
2325 : 1073 : parenttag = *targettag;
2326 : :
2327 [ + + ]: 3219 : while (GetParentPredicateLockTag(&parenttag, &nexttag))
2328 : : {
2329 : : uint32 targettaghash;
2330 : : LOCALPREDICATELOCK *parentlock,
2331 : : *rmlock PG_USED_FOR_ASSERTS_ONLY;
2332 : :
2333 : 2146 : parenttag = nexttag;
2334 : 2146 : targettaghash = PredicateLockTargetTagHashCode(&parenttag);
2335 : : parentlock = (LOCALPREDICATELOCK *)
2336 : 2146 : hash_search_with_hash_value(LocalPredicateLockHash,
2337 : : &parenttag, targettaghash,
2338 : : HASH_FIND, NULL);
2339 : :
2340 : : /*
2341 : : * There's a small chance the parent lock doesn't exist in the lock
2342 : : * table. This can happen if we prematurely removed it because an
2343 : : * index split caused the child refcount to be off.
2344 : : */
2345 [ - + ]: 2146 : if (parentlock == NULL)
2346 : 0 : continue;
2347 : :
2348 : 2146 : parentlock->childLocks--;
2349 : :
2350 : : /*
2351 : : * Under similar circumstances the parent lock's refcount might be
2352 : : * zero. This only happens if we're holding that lock (otherwise we
2353 : : * would have removed the entry).
2354 : : */
2355 [ - + ]: 2146 : if (parentlock->childLocks < 0)
2356 : : {
2357 : : Assert(parentlock->held);
2358 : 0 : parentlock->childLocks = 0;
2359 : : }
2360 : :
2361 [ + + + + ]: 2146 : if ((parentlock->childLocks == 0) && (!parentlock->held))
2362 : : {
2363 : : rmlock = (LOCALPREDICATELOCK *)
2364 : 776 : hash_search_with_hash_value(LocalPredicateLockHash,
2365 : : &parenttag, targettaghash,
2366 : : HASH_REMOVE, NULL);
2367 : : Assert(rmlock == parentlock);
2368 : : }
2369 : : }
2370 : 1073 : }
2371 : :
2372 : : /*
2373 : : * Indicate that a predicate lock on the given target is held by the
2374 : : * specified transaction. Has no effect if the lock is already held.
2375 : : *
2376 : : * This updates the lock table and the sxact's lock list, and creates
2377 : : * the lock target if necessary, but does *not* do anything related to
2378 : : * granularity promotion or the local lock table. See
2379 : : * PredicateLockAcquire for that.
2380 : : */
2381 : : static void
2382 : 3947 : CreatePredicateLock(const PREDICATELOCKTARGETTAG *targettag,
2383 : : uint32 targettaghash,
2384 : : SERIALIZABLEXACT *sxact)
2385 : : {
2386 : : PREDICATELOCKTARGET *target;
2387 : : PREDICATELOCKTAG locktag;
2388 : : PREDICATELOCK *lock;
2389 : : LWLock *partitionLock;
2390 : : bool found;
2391 : :
2392 : 3947 : partitionLock = PredicateLockHashPartitionLock(targettaghash);
2393 : :
2394 : 3947 : LWLockAcquire(SerializablePredicateListLock, LW_SHARED);
2395 [ + + ]: 3947 : if (IsInParallelMode())
2396 : 16 : LWLockAcquire(&sxact->perXactPredicateListLock, LW_EXCLUSIVE);
2397 : 3947 : LWLockAcquire(partitionLock, LW_EXCLUSIVE);
2398 : :
2399 : : /* Make sure that the target is represented. */
2400 : : target = (PREDICATELOCKTARGET *)
2401 : 3947 : hash_search_with_hash_value(PredicateLockTargetHash,
2402 : : targettag, targettaghash,
2403 : : HASH_ENTER_NULL, &found);
2404 [ - + ]: 3947 : if (!target)
2405 [ # # ]: 0 : ereport(ERROR,
2406 : : (errcode(ERRCODE_OUT_OF_MEMORY),
2407 : : errmsg("out of shared memory"),
2408 : : errhint("You might need to increase \"%s\".", "max_pred_locks_per_transaction")));
2409 [ + + ]: 3947 : if (!found)
2410 : 2968 : dlist_init(&target->predicateLocks);
2411 : :
2412 : : /* We've got the sxact and target, make sure they're joined. */
2413 : 3947 : locktag.myTarget = target;
2414 : 3947 : locktag.myXact = sxact;
2415 : : lock = (PREDICATELOCK *)
2416 : 3947 : hash_search_with_hash_value(PredicateLockHash, &locktag,
2417 : 3947 : PredicateLockHashCodeFromTargetHashCode(&locktag, targettaghash),
2418 : : HASH_ENTER_NULL, &found);
2419 [ - + ]: 3947 : if (!lock)
2420 [ # # ]: 0 : ereport(ERROR,
2421 : : (errcode(ERRCODE_OUT_OF_MEMORY),
2422 : : errmsg("out of shared memory"),
2423 : : errhint("You might need to increase \"%s\".", "max_pred_locks_per_transaction")));
2424 : :
2425 [ + + ]: 3947 : if (!found)
2426 : : {
2427 : 3941 : dlist_push_tail(&target->predicateLocks, &lock->targetLink);
2428 : 3941 : dlist_push_tail(&sxact->predicateLocks, &lock->xactLink);
2429 : 3941 : lock->commitSeqNo = InvalidSerCommitSeqNo;
2430 : : }
2431 : :
2432 : 3947 : LWLockRelease(partitionLock);
2433 [ + + ]: 3947 : if (IsInParallelMode())
2434 : 16 : LWLockRelease(&sxact->perXactPredicateListLock);
2435 : 3947 : LWLockRelease(SerializablePredicateListLock);
2436 : 3947 : }
2437 : :
2438 : : /*
2439 : : * Acquire a predicate lock on the specified target for the current
2440 : : * connection if not already held. This updates the local lock table
2441 : : * and uses it to implement granularity promotion. It will consolidate
2442 : : * multiple locks into a coarser lock if warranted, and will release
2443 : : * any finer-grained locks covered by the new one.
2444 : : */
2445 : : static void
2446 : 26131 : PredicateLockAcquire(const PREDICATELOCKTARGETTAG *targettag)
2447 : : {
2448 : : uint32 targettaghash;
2449 : : bool found;
2450 : : LOCALPREDICATELOCK *locallock;
2451 : :
2452 : : /* Do we have the lock already, or a covering lock? */
2453 [ + + ]: 26131 : if (PredicateLockExists(targettag))
2454 : 22184 : return;
2455 : :
2456 [ + + ]: 8608 : if (CoarserLockCovers(targettag))
2457 : 4661 : return;
2458 : :
2459 : : /* the same hash and LW lock apply to the lock target and the local lock. */
2460 : 3947 : targettaghash = PredicateLockTargetTagHashCode(targettag);
2461 : :
2462 : : /* Acquire lock in local table */
2463 : : locallock = (LOCALPREDICATELOCK *)
2464 : 3947 : hash_search_with_hash_value(LocalPredicateLockHash,
2465 : : targettag, targettaghash,
2466 : : HASH_ENTER, &found);
2467 : 3947 : locallock->held = true;
2468 [ + + ]: 3947 : if (!found)
2469 : 3614 : locallock->childLocks = 0;
2470 : :
2471 : : /* Actually create the lock */
2472 : 3947 : CreatePredicateLock(targettag, targettaghash, MySerializableXact);
2473 : :
2474 : : /*
2475 : : * Lock has been acquired. Check whether it should be promoted to a
2476 : : * coarser granularity, or whether there are finer-granularity locks to
2477 : : * clean up.
2478 : : */
2479 [ + + ]: 3947 : if (CheckAndPromotePredicateLockRequest(targettag))
2480 : : {
2481 : : /*
2482 : : * Lock request was promoted to a coarser-granularity lock, and that
2483 : : * lock was acquired. It will delete this lock and any of its
2484 : : * children, so we're done.
2485 : : */
2486 : : }
2487 : : else
2488 : : {
2489 : : /* Clean up any finer-granularity locks */
2490 [ + + ]: 3774 : if (GET_PREDICATELOCKTARGETTAG_TYPE(*targettag) != PREDLOCKTAG_TUPLE)
2491 : 2379 : DeleteChildTargetLocks(targettag);
2492 : : }
2493 : : }
2494 : :
2495 : :
2496 : : /*
2497 : : * PredicateLockRelation
2498 : : *
2499 : : * Gets a predicate lock at the relation level.
2500 : : * Skip if not in full serializable transaction isolation level.
2501 : : * Skip if this is a temporary table.
2502 : : * Clear any finer-grained predicate locks this session has on the relation.
2503 : : */
2504 : : void
2505 : 472187 : PredicateLockRelation(Relation relation, Snapshot snapshot)
2506 : : {
2507 : : PREDICATELOCKTARGETTAG tag;
2508 : :
2509 [ + + ]: 472187 : if (!SerializationNeededForRead(relation, snapshot))
2510 : 471461 : return;
2511 : :
2512 : 726 : SET_PREDICATELOCKTARGETTAG_RELATION(tag,
2513 : : relation->rd_locator.dbOid,
2514 : : relation->rd_id);
2515 : 726 : PredicateLockAcquire(&tag);
2516 : : }
2517 : :
2518 : : /*
2519 : : * PredicateLockPage
2520 : : *
2521 : : * Gets a predicate lock at the page level.
2522 : : * Skip if not in full serializable transaction isolation level.
2523 : : * Skip if this is a temporary table.
2524 : : * Skip if a coarser predicate lock already covers this page.
2525 : : * Clear any finer-grained predicate locks this session has on the relation.
2526 : : */
2527 : : void
2528 : 13633559 : PredicateLockPage(Relation relation, BlockNumber blkno, Snapshot snapshot)
2529 : : {
2530 : : PREDICATELOCKTARGETTAG tag;
2531 : :
2532 [ + + ]: 13633559 : if (!SerializationNeededForRead(relation, snapshot))
2533 : 13614623 : return;
2534 : :
2535 : 18936 : SET_PREDICATELOCKTARGETTAG_PAGE(tag,
2536 : : relation->rd_locator.dbOid,
2537 : : relation->rd_id,
2538 : : blkno);
2539 : 18936 : PredicateLockAcquire(&tag);
2540 : : }
2541 : :
2542 : : /*
2543 : : * PredicateLockTID
2544 : : *
2545 : : * Gets a predicate lock at the tuple level.
2546 : : * Skip if not in full serializable transaction isolation level.
2547 : : * Skip if this is a temporary table.
2548 : : */
2549 : : void
2550 : 23817009 : PredicateLockTID(Relation relation, const ItemPointerData *tid, Snapshot snapshot,
2551 : : TransactionId tuple_xid)
2552 : : {
2553 : : PREDICATELOCKTARGETTAG tag;
2554 : :
2555 [ + + ]: 23817009 : if (!SerializationNeededForRead(relation, snapshot))
2556 : 23810713 : return;
2557 : :
2558 : : /*
2559 : : * Return if this xact wrote it.
2560 : : */
2561 [ + - ]: 6298 : if (relation->rd_index == NULL)
2562 : : {
2563 : : /* If we wrote it; we already have a write lock. */
2564 [ + + ]: 6298 : if (TransactionIdIsCurrentTransactionId(tuple_xid))
2565 : 2 : return;
2566 : : }
2567 : :
2568 : : /*
2569 : : * Do quick-but-not-definitive test for a relation lock first. This will
2570 : : * never cause a return when the relation is *not* locked, but will
2571 : : * occasionally let the check continue when there really *is* a relation
2572 : : * level lock.
2573 : : */
2574 : 6296 : SET_PREDICATELOCKTARGETTAG_RELATION(tag,
2575 : : relation->rd_locator.dbOid,
2576 : : relation->rd_id);
2577 [ - + ]: 6296 : if (PredicateLockExists(&tag))
2578 : 0 : return;
2579 : :
2580 : 6296 : SET_PREDICATELOCKTARGETTAG_TUPLE(tag,
2581 : : relation->rd_locator.dbOid,
2582 : : relation->rd_id,
2583 : : ItemPointerGetBlockNumber(tid),
2584 : : ItemPointerGetOffsetNumber(tid));
2585 : 6296 : PredicateLockAcquire(&tag);
2586 : : }
2587 : :
2588 : :
2589 : : /*
2590 : : * DeleteLockTarget
2591 : : *
2592 : : * Remove a predicate lock target along with any locks held for it.
2593 : : *
2594 : : * Caller must hold SerializablePredicateListLock and the
2595 : : * appropriate hash partition lock for the target.
2596 : : */
2597 : : static void
2598 : 0 : DeleteLockTarget(PREDICATELOCKTARGET *target, uint32 targettaghash)
2599 : : {
2600 : : dlist_mutable_iter iter;
2601 : :
2602 : : Assert(LWLockHeldByMeInMode(SerializablePredicateListLock,
2603 : : LW_EXCLUSIVE));
2604 : : Assert(LWLockHeldByMe(PredicateLockHashPartitionLock(targettaghash)));
2605 : :
2606 : 0 : LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
2607 : :
2608 [ # # # # ]: 0 : dlist_foreach_modify(iter, &target->predicateLocks)
2609 : : {
2610 : 0 : PREDICATELOCK *predlock =
2611 : 0 : dlist_container(PREDICATELOCK, targetLink, iter.cur);
2612 : : bool found;
2613 : :
2614 : 0 : dlist_delete(&(predlock->xactLink));
2615 : 0 : dlist_delete(&(predlock->targetLink));
2616 : :
2617 : 0 : hash_search_with_hash_value
2618 : : (PredicateLockHash,
2619 : 0 : &predlock->tag,
2620 : 0 : PredicateLockHashCodeFromTargetHashCode(&predlock->tag,
2621 : : targettaghash),
2622 : : HASH_REMOVE, &found);
2623 : : Assert(found);
2624 : : }
2625 : 0 : LWLockRelease(SerializableXactHashLock);
2626 : :
2627 : : /* Remove the target itself, if possible. */
2628 : 0 : RemoveTargetIfNoLongerUsed(target, targettaghash);
2629 : 0 : }
2630 : :
2631 : :
2632 : : /*
2633 : : * TransferPredicateLocksToNewTarget
2634 : : *
2635 : : * Move or copy all the predicate locks for a lock target, for use by
2636 : : * index page splits/combines and other things that create or replace
2637 : : * lock targets. If 'removeOld' is true, the old locks and the target
2638 : : * will be removed.
2639 : : *
2640 : : * Returns true on success, or false if we ran out of shared memory to
2641 : : * allocate the new target or locks. Guaranteed to always succeed if
2642 : : * removeOld is set (by using the scratch entry in PredicateLockTargetHash
2643 : : * for scratch space).
2644 : : *
2645 : : * Warning: the "removeOld" option should be used only with care,
2646 : : * because this function does not (indeed, can not) update other
2647 : : * backends' LocalPredicateLockHash. If we are only adding new
2648 : : * entries, this is not a problem: the local lock table is used only
2649 : : * as a hint, so missing entries for locks that are held are
2650 : : * OK. Having entries for locks that are no longer held, as can happen
2651 : : * when using "removeOld", is not in general OK. We can only use it
2652 : : * safely when replacing a lock with a coarser-granularity lock that
2653 : : * covers it, or if we are absolutely certain that no one will need to
2654 : : * refer to that lock in the future.
2655 : : *
2656 : : * Caller must hold SerializablePredicateListLock exclusively.
2657 : : */
2658 : : static bool
2659 : 27 : TransferPredicateLocksToNewTarget(PREDICATELOCKTARGETTAG oldtargettag,
2660 : : PREDICATELOCKTARGETTAG newtargettag,
2661 : : bool removeOld)
2662 : : {
2663 : : uint32 oldtargettaghash;
2664 : : LWLock *oldpartitionLock;
2665 : : PREDICATELOCKTARGET *oldtarget;
2666 : : uint32 newtargettaghash;
2667 : : LWLock *newpartitionLock;
2668 : : bool found;
2669 : 27 : bool outOfShmem = false;
2670 : :
2671 : : Assert(LWLockHeldByMeInMode(SerializablePredicateListLock,
2672 : : LW_EXCLUSIVE));
2673 : :
2674 : 27 : oldtargettaghash = PredicateLockTargetTagHashCode(&oldtargettag);
2675 : 27 : newtargettaghash = PredicateLockTargetTagHashCode(&newtargettag);
2676 : 27 : oldpartitionLock = PredicateLockHashPartitionLock(oldtargettaghash);
2677 : 27 : newpartitionLock = PredicateLockHashPartitionLock(newtargettaghash);
2678 : :
2679 [ - + ]: 27 : if (removeOld)
2680 : : {
2681 : : /*
2682 : : * Remove the dummy entry to give us scratch space, so we know we'll
2683 : : * be able to create the new lock target.
2684 : : */
2685 : 0 : RemoveScratchTarget(false);
2686 : : }
2687 : :
2688 : : /*
2689 : : * We must get the partition locks in ascending sequence to avoid
2690 : : * deadlocks. If old and new partitions are the same, we must request the
2691 : : * lock only once.
2692 : : */
2693 [ + + ]: 27 : if (oldpartitionLock < newpartitionLock)
2694 : : {
2695 : 14 : LWLockAcquire(oldpartitionLock,
2696 : 14 : (removeOld ? LW_EXCLUSIVE : LW_SHARED));
2697 : 14 : LWLockAcquire(newpartitionLock, LW_EXCLUSIVE);
2698 : : }
2699 [ + + ]: 13 : else if (oldpartitionLock > newpartitionLock)
2700 : : {
2701 : 11 : LWLockAcquire(newpartitionLock, LW_EXCLUSIVE);
2702 : 11 : LWLockAcquire(oldpartitionLock,
2703 : 11 : (removeOld ? LW_EXCLUSIVE : LW_SHARED));
2704 : : }
2705 : : else
2706 : 2 : LWLockAcquire(newpartitionLock, LW_EXCLUSIVE);
2707 : :
2708 : : /*
2709 : : * Look for the old target. If not found, that's OK; no predicate locks
2710 : : * are affected, so we can just clean up and return. If it does exist,
2711 : : * walk its list of predicate locks and move or copy them to the new
2712 : : * target.
2713 : : */
2714 : 27 : oldtarget = hash_search_with_hash_value(PredicateLockTargetHash,
2715 : : &oldtargettag,
2716 : : oldtargettaghash,
2717 : : HASH_FIND, NULL);
2718 : :
2719 [ + - ]: 27 : if (oldtarget)
2720 : : {
2721 : : PREDICATELOCKTARGET *newtarget;
2722 : : PREDICATELOCKTAG newpredlocktag;
2723 : : dlist_mutable_iter iter;
2724 : :
2725 : 0 : newtarget = hash_search_with_hash_value(PredicateLockTargetHash,
2726 : : &newtargettag,
2727 : : newtargettaghash,
2728 : : HASH_ENTER_NULL, &found);
2729 : :
2730 [ # # ]: 0 : if (!newtarget)
2731 : : {
2732 : : /* Failed to allocate due to insufficient shmem */
2733 : 0 : outOfShmem = true;
2734 : 0 : goto exit;
2735 : : }
2736 : :
2737 : : /* If we created a new entry, initialize it */
2738 [ # # ]: 0 : if (!found)
2739 : 0 : dlist_init(&newtarget->predicateLocks);
2740 : :
2741 : 0 : newpredlocktag.myTarget = newtarget;
2742 : :
2743 : : /*
2744 : : * Loop through all the locks on the old target, replacing them with
2745 : : * locks on the new target.
2746 : : */
2747 : 0 : LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
2748 : :
2749 [ # # # # ]: 0 : dlist_foreach_modify(iter, &oldtarget->predicateLocks)
2750 : : {
2751 : 0 : PREDICATELOCK *oldpredlock =
2752 : 0 : dlist_container(PREDICATELOCK, targetLink, iter.cur);
2753 : : PREDICATELOCK *newpredlock;
2754 : 0 : SerCommitSeqNo oldCommitSeqNo = oldpredlock->commitSeqNo;
2755 : :
2756 : 0 : newpredlocktag.myXact = oldpredlock->tag.myXact;
2757 : :
2758 [ # # ]: 0 : if (removeOld)
2759 : : {
2760 : 0 : dlist_delete(&(oldpredlock->xactLink));
2761 : 0 : dlist_delete(&(oldpredlock->targetLink));
2762 : :
2763 : 0 : hash_search_with_hash_value
2764 : : (PredicateLockHash,
2765 : 0 : &oldpredlock->tag,
2766 : 0 : PredicateLockHashCodeFromTargetHashCode(&oldpredlock->tag,
2767 : : oldtargettaghash),
2768 : : HASH_REMOVE, &found);
2769 : : Assert(found);
2770 : : }
2771 : :
2772 : : newpredlock = (PREDICATELOCK *)
2773 : 0 : hash_search_with_hash_value(PredicateLockHash,
2774 : : &newpredlocktag,
2775 : 0 : PredicateLockHashCodeFromTargetHashCode(&newpredlocktag,
2776 : : newtargettaghash),
2777 : : HASH_ENTER_NULL,
2778 : : &found);
2779 [ # # ]: 0 : if (!newpredlock)
2780 : : {
2781 : : /* Out of shared memory. Undo what we've done so far. */
2782 : 0 : LWLockRelease(SerializableXactHashLock);
2783 : 0 : DeleteLockTarget(newtarget, newtargettaghash);
2784 : 0 : outOfShmem = true;
2785 : 0 : goto exit;
2786 : : }
2787 [ # # ]: 0 : if (!found)
2788 : : {
2789 : 0 : dlist_push_tail(&(newtarget->predicateLocks),
2790 : : &(newpredlock->targetLink));
2791 : 0 : dlist_push_tail(&(newpredlocktag.myXact->predicateLocks),
2792 : : &(newpredlock->xactLink));
2793 : 0 : newpredlock->commitSeqNo = oldCommitSeqNo;
2794 : : }
2795 : : else
2796 : : {
2797 [ # # ]: 0 : if (newpredlock->commitSeqNo < oldCommitSeqNo)
2798 : 0 : newpredlock->commitSeqNo = oldCommitSeqNo;
2799 : : }
2800 : :
2801 : : Assert(newpredlock->commitSeqNo != 0);
2802 : : Assert((newpredlock->commitSeqNo == InvalidSerCommitSeqNo)
2803 : : || (newpredlock->tag.myXact == OldCommittedSxact));
2804 : : }
2805 : 0 : LWLockRelease(SerializableXactHashLock);
2806 : :
2807 [ # # ]: 0 : if (removeOld)
2808 : : {
2809 : : Assert(dlist_is_empty(&oldtarget->predicateLocks));
2810 : 0 : RemoveTargetIfNoLongerUsed(oldtarget, oldtargettaghash);
2811 : : }
2812 : : }
2813 : :
2814 : :
2815 : 27 : exit:
2816 : : /* Release partition locks in reverse order of acquisition. */
2817 [ + + ]: 27 : if (oldpartitionLock < newpartitionLock)
2818 : : {
2819 : 14 : LWLockRelease(newpartitionLock);
2820 : 14 : LWLockRelease(oldpartitionLock);
2821 : : }
2822 [ + + ]: 13 : else if (oldpartitionLock > newpartitionLock)
2823 : : {
2824 : 11 : LWLockRelease(oldpartitionLock);
2825 : 11 : LWLockRelease(newpartitionLock);
2826 : : }
2827 : : else
2828 : 2 : LWLockRelease(newpartitionLock);
2829 : :
2830 [ - + ]: 27 : if (removeOld)
2831 : : {
2832 : : /* We shouldn't run out of memory if we're moving locks */
2833 : : Assert(!outOfShmem);
2834 : :
2835 : : /* Put the scratch entry back */
2836 : 0 : RestoreScratchTarget(false);
2837 : : }
2838 : :
2839 : 27 : return !outOfShmem;
2840 : : }
2841 : :
2842 : : /*
2843 : : * Drop all predicate locks of any granularity from the specified relation,
2844 : : * which can be a heap relation or an index relation. If 'transfer' is true,
2845 : : * acquire a relation lock on the heap for any transactions with any lock(s)
2846 : : * on the specified relation.
2847 : : *
2848 : : * This requires grabbing a lot of LW locks and scanning the entire lock
2849 : : * target table for matches. That makes this more expensive than most
2850 : : * predicate lock management functions, but it will only be called for DDL
2851 : : * type commands that are expensive anyway, and there are fast returns when
2852 : : * no serializable transactions are active or the relation is temporary.
2853 : : *
2854 : : * We don't use the TransferPredicateLocksToNewTarget function because it
2855 : : * acquires its own locks on the partitions of the two targets involved,
2856 : : * and we'll already be holding all partition locks.
2857 : : *
2858 : : * We can't throw an error from here, because the call could be from a
2859 : : * transaction which is not serializable.
2860 : : *
2861 : : * NOTE: This is currently only called with transfer set to true, but that may
2862 : : * change. If we decide to clean up the locks from a table on commit of a
2863 : : * transaction which executed DROP TABLE, the false condition will be useful.
2864 : : */
2865 : : static void
2866 : 23267 : DropAllPredicateLocksFromTable(Relation relation, bool transfer)
2867 : : {
2868 : : HASH_SEQ_STATUS seqstat;
2869 : : PREDICATELOCKTARGET *oldtarget;
2870 : : PREDICATELOCKTARGET *heaptarget;
2871 : : Oid dbId;
2872 : : Oid relId;
2873 : : Oid heapId;
2874 : : int i;
2875 : : bool isIndex;
2876 : : bool found;
2877 : : uint32 heaptargettaghash;
2878 : :
2879 : : /*
2880 : : * Bail out quickly if there are no serializable transactions running.
2881 : : * It's safe to check this without taking locks because the caller is
2882 : : * holding an ACCESS EXCLUSIVE lock on the relation. No new locks which
2883 : : * would matter here can be acquired while that is held.
2884 : : */
2885 [ + + ]: 23267 : if (!TransactionIdIsValid(PredXact->SxactGlobalXmin))
2886 : 23218 : return;
2887 : :
2888 [ + + ]: 74 : if (!PredicateLockingNeededForRelation(relation))
2889 : 25 : return;
2890 : :
2891 : 49 : dbId = relation->rd_locator.dbOid;
2892 : 49 : relId = relation->rd_id;
2893 [ + + ]: 49 : if (relation->rd_index == NULL)
2894 : : {
2895 : 2 : isIndex = false;
2896 : 2 : heapId = relId;
2897 : : }
2898 : : else
2899 : : {
2900 : 47 : isIndex = true;
2901 : 47 : heapId = relation->rd_index->indrelid;
2902 : : }
2903 : : Assert(heapId != InvalidOid);
2904 : : Assert(transfer || !isIndex); /* index OID only makes sense with
2905 : : * transfer */
2906 : :
2907 : : /* Retrieve first time needed, then keep. */
2908 : 49 : heaptargettaghash = 0;
2909 : 49 : heaptarget = NULL;
2910 : :
2911 : : /* Acquire locks on all lock partitions */
2912 : 49 : LWLockAcquire(SerializablePredicateListLock, LW_EXCLUSIVE);
2913 [ + + ]: 833 : for (i = 0; i < NUM_PREDICATELOCK_PARTITIONS; i++)
2914 : 784 : LWLockAcquire(PredicateLockHashPartitionLockByIndex(i), LW_EXCLUSIVE);
2915 : 49 : LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
2916 : :
2917 : : /*
2918 : : * Remove the dummy entry to give us scratch space, so we know we'll be
2919 : : * able to create the new lock target.
2920 : : */
2921 [ + - ]: 49 : if (transfer)
2922 : 49 : RemoveScratchTarget(true);
2923 : :
2924 : : /* Scan through target map */
2925 : 49 : hash_seq_init(&seqstat, PredicateLockTargetHash);
2926 : :
2927 [ + + ]: 89 : while ((oldtarget = (PREDICATELOCKTARGET *) hash_seq_search(&seqstat)))
2928 : : {
2929 : : dlist_mutable_iter iter;
2930 : :
2931 : : /*
2932 : : * Check whether this is a target which needs attention.
2933 : : */
2934 [ + - ]: 40 : if (GET_PREDICATELOCKTARGETTAG_RELATION(oldtarget->tag) != relId)
2935 : 40 : continue; /* wrong relation id */
2936 [ # # ]: 0 : if (GET_PREDICATELOCKTARGETTAG_DB(oldtarget->tag) != dbId)
2937 : 0 : continue; /* wrong database id */
2938 [ # # # # ]: 0 : if (transfer && !isIndex
2939 [ # # # # ]: 0 : && GET_PREDICATELOCKTARGETTAG_TYPE(oldtarget->tag) == PREDLOCKTAG_RELATION)
2940 : 0 : continue; /* already the right lock */
2941 : :
2942 : : /*
2943 : : * If we made it here, we have work to do. We make sure the heap
2944 : : * relation lock exists, then we walk the list of predicate locks for
2945 : : * the old target we found, moving all locks to the heap relation lock
2946 : : * -- unless they already hold that.
2947 : : */
2948 : :
2949 : : /*
2950 : : * First make sure we have the heap relation target. We only need to
2951 : : * do this once.
2952 : : */
2953 [ # # # # ]: 0 : if (transfer && heaptarget == NULL)
2954 : : {
2955 : : PREDICATELOCKTARGETTAG heaptargettag;
2956 : :
2957 : 0 : SET_PREDICATELOCKTARGETTAG_RELATION(heaptargettag, dbId, heapId);
2958 : 0 : heaptargettaghash = PredicateLockTargetTagHashCode(&heaptargettag);
2959 : 0 : heaptarget = hash_search_with_hash_value(PredicateLockTargetHash,
2960 : : &heaptargettag,
2961 : : heaptargettaghash,
2962 : : HASH_ENTER, &found);
2963 [ # # ]: 0 : if (!found)
2964 : 0 : dlist_init(&heaptarget->predicateLocks);
2965 : : }
2966 : :
2967 : : /*
2968 : : * Loop through all the locks on the old target, replacing them with
2969 : : * locks on the new target.
2970 : : */
2971 [ # # # # ]: 0 : dlist_foreach_modify(iter, &oldtarget->predicateLocks)
2972 : : {
2973 : 0 : PREDICATELOCK *oldpredlock =
2974 : 0 : dlist_container(PREDICATELOCK, targetLink, iter.cur);
2975 : : PREDICATELOCK *newpredlock;
2976 : : SerCommitSeqNo oldCommitSeqNo;
2977 : : SERIALIZABLEXACT *oldXact;
2978 : :
2979 : : /*
2980 : : * Remove the old lock first. This avoids the chance of running
2981 : : * out of lock structure entries for the hash table.
2982 : : */
2983 : 0 : oldCommitSeqNo = oldpredlock->commitSeqNo;
2984 : 0 : oldXact = oldpredlock->tag.myXact;
2985 : :
2986 : 0 : dlist_delete(&(oldpredlock->xactLink));
2987 : :
2988 : : /*
2989 : : * No need for retail delete from oldtarget list, we're removing
2990 : : * the whole target anyway.
2991 : : */
2992 : 0 : hash_search(PredicateLockHash,
2993 : 0 : &oldpredlock->tag,
2994 : : HASH_REMOVE, &found);
2995 : : Assert(found);
2996 : :
2997 [ # # ]: 0 : if (transfer)
2998 : : {
2999 : : PREDICATELOCKTAG newpredlocktag;
3000 : :
3001 : 0 : newpredlocktag.myTarget = heaptarget;
3002 : 0 : newpredlocktag.myXact = oldXact;
3003 : : newpredlock = (PREDICATELOCK *)
3004 : 0 : hash_search_with_hash_value(PredicateLockHash,
3005 : : &newpredlocktag,
3006 : 0 : PredicateLockHashCodeFromTargetHashCode(&newpredlocktag,
3007 : : heaptargettaghash),
3008 : : HASH_ENTER,
3009 : : &found);
3010 [ # # ]: 0 : if (!found)
3011 : : {
3012 : 0 : dlist_push_tail(&(heaptarget->predicateLocks),
3013 : : &(newpredlock->targetLink));
3014 : 0 : dlist_push_tail(&(newpredlocktag.myXact->predicateLocks),
3015 : : &(newpredlock->xactLink));
3016 : 0 : newpredlock->commitSeqNo = oldCommitSeqNo;
3017 : : }
3018 : : else
3019 : : {
3020 [ # # ]: 0 : if (newpredlock->commitSeqNo < oldCommitSeqNo)
3021 : 0 : newpredlock->commitSeqNo = oldCommitSeqNo;
3022 : : }
3023 : :
3024 : : Assert(newpredlock->commitSeqNo != 0);
3025 : : Assert((newpredlock->commitSeqNo == InvalidSerCommitSeqNo)
3026 : : || (newpredlock->tag.myXact == OldCommittedSxact));
3027 : : }
3028 : : }
3029 : :
3030 : 0 : hash_search(PredicateLockTargetHash, &oldtarget->tag, HASH_REMOVE,
3031 : : &found);
3032 : : Assert(found);
3033 : : }
3034 : :
3035 : : /* Put the scratch entry back */
3036 [ + - ]: 49 : if (transfer)
3037 : 49 : RestoreScratchTarget(true);
3038 : :
3039 : : /* Release locks in reverse order */
3040 : 49 : LWLockRelease(SerializableXactHashLock);
3041 [ + + ]: 833 : for (i = NUM_PREDICATELOCK_PARTITIONS - 1; i >= 0; i--)
3042 : 784 : LWLockRelease(PredicateLockHashPartitionLockByIndex(i));
3043 : 49 : LWLockRelease(SerializablePredicateListLock);
3044 : : }
3045 : :
3046 : : /*
3047 : : * TransferPredicateLocksToHeapRelation
3048 : : * For all transactions, transfer all predicate locks for the given
3049 : : * relation to a single relation lock on the heap.
3050 : : */
3051 : : void
3052 : 23267 : TransferPredicateLocksToHeapRelation(Relation relation)
3053 : : {
3054 : 23267 : DropAllPredicateLocksFromTable(relation, true);
3055 : 23267 : }
3056 : :
3057 : :
3058 : : /*
3059 : : * PredicateLockPageSplit
3060 : : *
3061 : : * Copies any predicate locks for the old page to the new page.
3062 : : * Skip if this is a temporary table or toast table.
3063 : : *
3064 : : * NOTE: A page split (or overflow) affects all serializable transactions,
3065 : : * even if it occurs in the context of another transaction isolation level.
3066 : : *
3067 : : * NOTE: This currently leaves the local copy of the locks without
3068 : : * information on the new lock which is in shared memory. This could cause
3069 : : * problems if enough page splits occur on locked pages without the processes
3070 : : * which hold the locks getting in and noticing.
3071 : : */
3072 : : void
3073 : 38751 : PredicateLockPageSplit(Relation relation, BlockNumber oldblkno,
3074 : : BlockNumber newblkno)
3075 : : {
3076 : : PREDICATELOCKTARGETTAG oldtargettag;
3077 : : PREDICATELOCKTARGETTAG newtargettag;
3078 : : bool success;
3079 : :
3080 : : /*
3081 : : * Bail out quickly if there are no serializable transactions running.
3082 : : *
3083 : : * It's safe to do this check without taking any additional locks. Even if
3084 : : * a serializable transaction starts concurrently, we know it can't take
3085 : : * any SIREAD locks on the page being split because the caller is holding
3086 : : * the associated buffer page lock. Memory reordering isn't an issue; the
3087 : : * memory barrier in the LWLock acquisition guarantees that this read
3088 : : * occurs while the buffer page lock is held.
3089 : : */
3090 [ + + ]: 38751 : if (!TransactionIdIsValid(PredXact->SxactGlobalXmin))
3091 : 38724 : return;
3092 : :
3093 [ + + ]: 48 : if (!PredicateLockingNeededForRelation(relation))
3094 : 21 : return;
3095 : :
3096 : : Assert(oldblkno != newblkno);
3097 : : Assert(BlockNumberIsValid(oldblkno));
3098 : : Assert(BlockNumberIsValid(newblkno));
3099 : :
3100 : 27 : SET_PREDICATELOCKTARGETTAG_PAGE(oldtargettag,
3101 : : relation->rd_locator.dbOid,
3102 : : relation->rd_id,
3103 : : oldblkno);
3104 : 27 : SET_PREDICATELOCKTARGETTAG_PAGE(newtargettag,
3105 : : relation->rd_locator.dbOid,
3106 : : relation->rd_id,
3107 : : newblkno);
3108 : :
3109 : 27 : LWLockAcquire(SerializablePredicateListLock, LW_EXCLUSIVE);
3110 : :
3111 : : /*
3112 : : * Try copying the locks over to the new page's tag, creating it if
3113 : : * necessary.
3114 : : */
3115 : 27 : success = TransferPredicateLocksToNewTarget(oldtargettag,
3116 : : newtargettag,
3117 : : false);
3118 : :
3119 [ - + ]: 27 : if (!success)
3120 : : {
3121 : : /*
3122 : : * No more predicate lock entries are available. Failure isn't an
3123 : : * option here, so promote the page lock to a relation lock.
3124 : : */
3125 : :
3126 : : /* Get the parent relation lock's lock tag */
3127 : 0 : success = GetParentPredicateLockTag(&oldtargettag,
3128 : : &newtargettag);
3129 : : Assert(success);
3130 : :
3131 : : /*
3132 : : * Move the locks to the parent. This shouldn't fail.
3133 : : *
3134 : : * Note that here we are removing locks held by other backends,
3135 : : * leading to a possible inconsistency in their local lock hash table.
3136 : : * This is OK because we're replacing it with a lock that covers the
3137 : : * old one.
3138 : : */
3139 : 0 : success = TransferPredicateLocksToNewTarget(oldtargettag,
3140 : : newtargettag,
3141 : : true);
3142 : : Assert(success);
3143 : : }
3144 : :
3145 : 27 : LWLockRelease(SerializablePredicateListLock);
3146 : : }
3147 : :
3148 : : /*
3149 : : * PredicateLockPageCombine
3150 : : *
3151 : : * Combines predicate locks for two existing pages.
3152 : : * Skip if this is a temporary table or toast table.
3153 : : *
3154 : : * NOTE: A page combine affects all serializable transactions, even if it
3155 : : * occurs in the context of another transaction isolation level.
3156 : : */
3157 : : void
3158 : 3645 : PredicateLockPageCombine(Relation relation, BlockNumber oldblkno,
3159 : : BlockNumber newblkno)
3160 : : {
3161 : : /*
3162 : : * Page combines differ from page splits in that we ought to be able to
3163 : : * remove the locks on the old page after transferring them to the new
3164 : : * page, instead of duplicating them. However, because we can't edit other
3165 : : * backends' local lock tables, removing the old lock would leave them
3166 : : * with an entry in their LocalPredicateLockHash for a lock they're not
3167 : : * holding, which isn't acceptable. So we wind up having to do the same
3168 : : * work as a page split, acquiring a lock on the new page and keeping the
3169 : : * old page locked too. That can lead to some false positives, but should
3170 : : * be rare in practice.
3171 : : */
3172 : 3645 : PredicateLockPageSplit(relation, oldblkno, newblkno);
3173 : 3645 : }
3174 : :
3175 : : /*
3176 : : * Walk the list of in-progress serializable transactions and find the new
3177 : : * xmin.
3178 : : */
3179 : : static void
3180 : 897 : SetNewSxactGlobalXmin(void)
3181 : : {
3182 : : dlist_iter iter;
3183 : :
3184 : : Assert(LWLockHeldByMe(SerializableXactHashLock));
3185 : :
3186 : 897 : PredXact->SxactGlobalXmin = InvalidTransactionId;
3187 : 897 : PredXact->SxactGlobalXminCount = 0;
3188 : :
3189 [ + - + + ]: 3378 : dlist_foreach(iter, &PredXact->activeList)
3190 : : {
3191 : 2481 : SERIALIZABLEXACT *sxact =
3192 : 2481 : dlist_container(SERIALIZABLEXACT, xactLink, iter.cur);
3193 : :
3194 [ + + ]: 2481 : if (!SxactIsRolledBack(sxact)
3195 [ + + ]: 2180 : && !SxactIsCommitted(sxact)
3196 [ + - ]: 17 : && sxact != OldCommittedSxact)
3197 : : {
3198 : : Assert(sxact->xmin != InvalidTransactionId);
3199 [ - + ]: 17 : if (!TransactionIdIsValid(PredXact->SxactGlobalXmin)
3200 [ # # ]: 0 : || TransactionIdPrecedes(sxact->xmin,
3201 : 0 : PredXact->SxactGlobalXmin))
3202 : : {
3203 : 17 : PredXact->SxactGlobalXmin = sxact->xmin;
3204 : 17 : PredXact->SxactGlobalXminCount = 1;
3205 : : }
3206 [ # # ]: 0 : else if (TransactionIdEquals(sxact->xmin,
3207 : : PredXact->SxactGlobalXmin))
3208 : 0 : PredXact->SxactGlobalXminCount++;
3209 : : }
3210 : : }
3211 : :
3212 : 897 : SerialSetActiveSerXmin(PredXact->SxactGlobalXmin);
3213 : 897 : }
3214 : :
3215 : : /*
3216 : : * ReleasePredicateLocks
3217 : : *
3218 : : * Releases predicate locks based on completion of the current transaction,
3219 : : * whether committed or rolled back. It can also be called for a read only
3220 : : * transaction when it becomes impossible for the transaction to become
3221 : : * part of a dangerous structure.
3222 : : *
3223 : : * We do nothing unless this is a serializable transaction.
3224 : : *
3225 : : * This method must ensure that shared memory hash tables are cleaned
3226 : : * up in some relatively timely fashion.
3227 : : *
3228 : : * If this transaction is committing and is holding any predicate locks,
3229 : : * it must be added to a list of completed serializable transactions still
3230 : : * holding locks.
3231 : : *
3232 : : * If isReadOnlySafe is true, then predicate locks are being released before
3233 : : * the end of the transaction because MySerializableXact has been determined
3234 : : * to be RO_SAFE. In non-parallel mode we can release it completely, but it
3235 : : * in parallel mode we partially release the SERIALIZABLEXACT and keep it
3236 : : * around until the end of the transaction, allowing each backend to clear its
3237 : : * MySerializableXact variable and benefit from the optimization in its own
3238 : : * time.
3239 : : */
3240 : : void
3241 : 668881 : ReleasePredicateLocks(bool isCommit, bool isReadOnlySafe)
3242 : : {
3243 : 668881 : bool partiallyReleasing = false;
3244 : : bool needToClear;
3245 : : SERIALIZABLEXACT *roXact;
3246 : : dlist_mutable_iter iter;
3247 : :
3248 : : /*
3249 : : * We can't trust XactReadOnly here, because a transaction which started
3250 : : * as READ WRITE can show as READ ONLY later, e.g., within
3251 : : * subtransactions. We want to flag a transaction as READ ONLY if it
3252 : : * commits without writing so that de facto READ ONLY transactions get the
3253 : : * benefit of some RO optimizations, so we will use this local variable to
3254 : : * get some cleanup logic right which is based on whether the transaction
3255 : : * was declared READ ONLY at the top level.
3256 : : */
3257 : : bool topLevelIsDeclaredReadOnly;
3258 : :
3259 : : /* We can't be both committing and releasing early due to RO_SAFE. */
3260 : : Assert(!(isCommit && isReadOnlySafe));
3261 : :
3262 : : /* Are we at the end of a transaction, that is, a commit or abort? */
3263 [ + + ]: 668881 : if (!isReadOnlySafe)
3264 : : {
3265 : : /*
3266 : : * Parallel workers mustn't release predicate locks at the end of
3267 : : * their transaction. The leader will do that at the end of its
3268 : : * transaction.
3269 : : */
3270 [ + + ]: 668847 : if (IsParallelWorker())
3271 : : {
3272 : 6033 : ReleasePredicateLocksLocal();
3273 : 667303 : return;
3274 : : }
3275 : :
3276 : : /*
3277 : : * By the time the leader in a parallel query reaches end of
3278 : : * transaction, it has waited for all workers to exit.
3279 : : */
3280 : : Assert(!ParallelContextActive());
3281 : :
3282 : : /*
3283 : : * If the leader in a parallel query earlier stashed a partially
3284 : : * released SERIALIZABLEXACT for final clean-up at end of transaction
3285 : : * (because workers might still have been accessing it), then it's
3286 : : * time to restore it.
3287 : : */
3288 [ + + ]: 662814 : if (SavedSerializableXact != InvalidSerializableXact)
3289 : : {
3290 : : Assert(MySerializableXact == InvalidSerializableXact);
3291 : 1 : MySerializableXact = SavedSerializableXact;
3292 : 1 : SavedSerializableXact = InvalidSerializableXact;
3293 : : Assert(SxactIsPartiallyReleased(MySerializableXact));
3294 : : }
3295 : : }
3296 : :
3297 [ + + ]: 662848 : if (MySerializableXact == InvalidSerializableXact)
3298 : : {
3299 : : Assert(LocalPredicateLockHash == NULL);
3300 : 661267 : return;
3301 : : }
3302 : :
3303 : 1581 : LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
3304 : :
3305 : : /*
3306 : : * If the transaction is committing, but it has been partially released
3307 : : * already, then treat this as a roll back. It was marked as rolled back.
3308 : : */
3309 [ + + + + ]: 1581 : if (isCommit && SxactIsPartiallyReleased(MySerializableXact))
3310 : 2 : isCommit = false;
3311 : :
3312 : : /*
3313 : : * If we're called in the middle of a transaction because we discovered
3314 : : * that the SXACT_FLAG_RO_SAFE flag was set, then we'll partially release
3315 : : * it (that is, release the predicate locks and conflicts, but not the
3316 : : * SERIALIZABLEXACT itself) if we're the first backend to have noticed.
3317 : : */
3318 [ + + + + ]: 1581 : if (isReadOnlySafe && IsInParallelMode())
3319 : : {
3320 : : /*
3321 : : * The leader needs to stash a pointer to it, so that it can
3322 : : * completely release it at end-of-transaction.
3323 : : */
3324 [ + + ]: 5 : if (!IsParallelWorker())
3325 : 1 : SavedSerializableXact = MySerializableXact;
3326 : :
3327 : : /*
3328 : : * The first backend to reach this condition will partially release
3329 : : * the SERIALIZABLEXACT. All others will just clear their
3330 : : * backend-local state so that they stop doing SSI checks for the rest
3331 : : * of the transaction.
3332 : : */
3333 [ + + ]: 5 : if (SxactIsPartiallyReleased(MySerializableXact))
3334 : : {
3335 : 3 : LWLockRelease(SerializableXactHashLock);
3336 : 3 : ReleasePredicateLocksLocal();
3337 : 3 : return;
3338 : : }
3339 : : else
3340 : : {
3341 : 2 : MySerializableXact->flags |= SXACT_FLAG_PARTIALLY_RELEASED;
3342 : 2 : partiallyReleasing = true;
3343 : : /* ... and proceed to perform the partial release below. */
3344 : : }
3345 : : }
3346 : : Assert(!isCommit || SxactIsPrepared(MySerializableXact));
3347 : : Assert(!isCommit || !SxactIsDoomed(MySerializableXact));
3348 : : Assert(!SxactIsCommitted(MySerializableXact));
3349 : : Assert(SxactIsPartiallyReleased(MySerializableXact)
3350 : : || !SxactIsRolledBack(MySerializableXact));
3351 : :
3352 : : /* may not be serializable during COMMIT/ROLLBACK PREPARED */
3353 : : Assert(MySerializableXact->pid == 0 || IsolationIsSerializable());
3354 : :
3355 : : /* We'd better not already be on the cleanup list. */
3356 : : Assert(!SxactIsOnFinishedList(MySerializableXact));
3357 : :
3358 : 1578 : topLevelIsDeclaredReadOnly = SxactIsReadOnly(MySerializableXact);
3359 : :
3360 : : /*
3361 : : * We don't hold XidGenLock lock here, assuming that TransactionId is
3362 : : * atomic!
3363 : : *
3364 : : * If this value is changing, we don't care that much whether we get the
3365 : : * old or new value -- it is just used to determine how far
3366 : : * SxactGlobalXmin must advance before this transaction can be fully
3367 : : * cleaned up. The worst that could happen is we wait for one more
3368 : : * transaction to complete before freeing some RAM; correctness of visible
3369 : : * behavior is not affected.
3370 : : */
3371 : 1578 : MySerializableXact->finishedBefore = XidFromFullTransactionId(TransamVariables->nextXid);
3372 : :
3373 : : /*
3374 : : * If it's not a commit it's either a rollback or a read-only transaction
3375 : : * flagged SXACT_FLAG_RO_SAFE, and we can clear our locks immediately.
3376 : : */
3377 [ + + ]: 1578 : if (isCommit)
3378 : : {
3379 : 1248 : MySerializableXact->flags |= SXACT_FLAG_COMMITTED;
3380 : 1248 : MySerializableXact->commitSeqNo = ++(PredXact->LastSxactCommitSeqNo);
3381 : : /* Recognize implicit read-only transaction (commit without write). */
3382 [ + + ]: 1248 : if (!MyXactDidWrite)
3383 : 239 : MySerializableXact->flags |= SXACT_FLAG_READ_ONLY;
3384 : : }
3385 : : else
3386 : : {
3387 : : /*
3388 : : * The DOOMED flag indicates that we intend to roll back this
3389 : : * transaction and so it should not cause serialization failures for
3390 : : * other transactions that conflict with it. Note that this flag might
3391 : : * already be set, if another backend marked this transaction for
3392 : : * abort.
3393 : : *
3394 : : * The ROLLED_BACK flag further indicates that ReleasePredicateLocks
3395 : : * has been called, and so the SerializableXact is eligible for
3396 : : * cleanup. This means it should not be considered when calculating
3397 : : * SxactGlobalXmin.
3398 : : */
3399 : 330 : MySerializableXact->flags |= SXACT_FLAG_DOOMED;
3400 : 330 : MySerializableXact->flags |= SXACT_FLAG_ROLLED_BACK;
3401 : :
3402 : : /*
3403 : : * If the transaction was previously prepared, but is now failing due
3404 : : * to a ROLLBACK PREPARED or (hopefully very rare) error after the
3405 : : * prepare, clear the prepared flag. This simplifies conflict
3406 : : * checking.
3407 : : */
3408 : 330 : MySerializableXact->flags &= ~SXACT_FLAG_PREPARED;
3409 : : }
3410 : :
3411 [ + + ]: 1578 : if (!topLevelIsDeclaredReadOnly)
3412 : : {
3413 : : Assert(PredXact->WritableSxactCount > 0);
3414 [ + + ]: 1469 : if (--(PredXact->WritableSxactCount) == 0)
3415 : : {
3416 : : /*
3417 : : * Release predicate locks and rw-conflicts in for all committed
3418 : : * transactions. There are no longer any transactions which might
3419 : : * conflict with the locks and no chance for new transactions to
3420 : : * overlap. Similarly, existing conflicts in can't cause pivots,
3421 : : * and any conflicts in which could have completed a dangerous
3422 : : * structure would already have caused a rollback, so any
3423 : : * remaining ones must be benign.
3424 : : */
3425 : 890 : PredXact->CanPartialClearThrough = PredXact->LastSxactCommitSeqNo;
3426 : : }
3427 : : }
3428 : : else
3429 : : {
3430 : : /*
3431 : : * Read-only transactions: clear the list of transactions that might
3432 : : * make us unsafe. Note that we use 'inLink' for the iteration as
3433 : : * opposed to 'outLink' for the r/w xacts.
3434 : : */
3435 [ + - + + ]: 151 : dlist_foreach_modify(iter, &MySerializableXact->possibleUnsafeConflicts)
3436 : : {
3437 : 42 : RWConflict possibleUnsafeConflict =
3438 : 42 : dlist_container(RWConflictData, inLink, iter.cur);
3439 : :
3440 : : Assert(!SxactIsReadOnly(possibleUnsafeConflict->sxactOut));
3441 : : Assert(MySerializableXact == possibleUnsafeConflict->sxactIn);
3442 : :
3443 : 42 : ReleaseRWConflict(possibleUnsafeConflict);
3444 : : }
3445 : : }
3446 : :
3447 : : /* Check for conflict out to old committed transactions. */
3448 [ + + ]: 1578 : if (isCommit
3449 [ + + ]: 1248 : && !SxactIsReadOnly(MySerializableXact)
3450 [ - + ]: 1009 : && SxactHasSummaryConflictOut(MySerializableXact))
3451 : : {
3452 : : /*
3453 : : * we don't know which old committed transaction we conflicted with,
3454 : : * so be conservative and use FirstNormalSerCommitSeqNo here
3455 : : */
3456 : 0 : MySerializableXact->SeqNo.earliestOutConflictCommit =
3457 : : FirstNormalSerCommitSeqNo;
3458 : 0 : MySerializableXact->flags |= SXACT_FLAG_CONFLICT_OUT;
3459 : : }
3460 : :
3461 : : /*
3462 : : * Release all outConflicts to committed transactions. If we're rolling
3463 : : * back clear them all. Set SXACT_FLAG_CONFLICT_OUT if any point to
3464 : : * previously committed transactions.
3465 : : */
3466 [ + - + + ]: 2265 : dlist_foreach_modify(iter, &MySerializableXact->outConflicts)
3467 : : {
3468 : 687 : RWConflict conflict =
3469 : : dlist_container(RWConflictData, outLink, iter.cur);
3470 : :
3471 [ + + ]: 687 : if (isCommit
3472 [ + + ]: 455 : && !SxactIsReadOnly(MySerializableXact)
3473 [ + + ]: 347 : && SxactIsCommitted(conflict->sxactIn))
3474 : : {
3475 [ - + ]: 96 : if ((MySerializableXact->flags & SXACT_FLAG_CONFLICT_OUT) == 0
3476 [ # # ]: 0 : || conflict->sxactIn->prepareSeqNo < MySerializableXact->SeqNo.earliestOutConflictCommit)
3477 : 96 : MySerializableXact->SeqNo.earliestOutConflictCommit = conflict->sxactIn->prepareSeqNo;
3478 : 96 : MySerializableXact->flags |= SXACT_FLAG_CONFLICT_OUT;
3479 : : }
3480 : :
3481 [ + + ]: 687 : if (!isCommit
3482 [ + + ]: 455 : || SxactIsCommitted(conflict->sxactIn)
3483 [ - + ]: 337 : || (conflict->sxactIn->SeqNo.lastCommitBeforeSnapshot >= PredXact->LastSxactCommitSeqNo))
3484 : 350 : ReleaseRWConflict(conflict);
3485 : : }
3486 : :
3487 : : /*
3488 : : * Release all inConflicts from committed and read-only transactions. If
3489 : : * we're rolling back, clear them all.
3490 : : */
3491 [ + - + + ]: 2358 : dlist_foreach_modify(iter, &MySerializableXact->inConflicts)
3492 : : {
3493 : 780 : RWConflict conflict =
3494 : 780 : dlist_container(RWConflictData, inLink, iter.cur);
3495 : :
3496 [ + + ]: 780 : if (!isCommit
3497 [ + + ]: 603 : || SxactIsCommitted(conflict->sxactOut)
3498 [ + + ]: 418 : || SxactIsReadOnly(conflict->sxactOut))
3499 : 442 : ReleaseRWConflict(conflict);
3500 : : }
3501 : :
3502 [ + + ]: 1578 : if (!topLevelIsDeclaredReadOnly)
3503 : : {
3504 : : /*
3505 : : * Remove ourselves from the list of possible conflicts for concurrent
3506 : : * READ ONLY transactions, flagging them as unsafe if we have a
3507 : : * conflict out. If any are waiting DEFERRABLE transactions, wake them
3508 : : * up if they are known safe or known unsafe.
3509 : : */
3510 [ + - + + ]: 1560 : dlist_foreach_modify(iter, &MySerializableXact->possibleUnsafeConflicts)
3511 : : {
3512 : 91 : RWConflict possibleUnsafeConflict =
3513 : : dlist_container(RWConflictData, outLink, iter.cur);
3514 : :
3515 : 91 : roXact = possibleUnsafeConflict->sxactIn;
3516 : : Assert(MySerializableXact == possibleUnsafeConflict->sxactOut);
3517 : : Assert(SxactIsReadOnly(roXact));
3518 : :
3519 : : /* Mark conflicted if necessary. */
3520 [ + + ]: 91 : if (isCommit
3521 [ + + ]: 88 : && MyXactDidWrite
3522 [ + + ]: 83 : && SxactHasConflictOut(MySerializableXact)
3523 : 13 : && (MySerializableXact->SeqNo.earliestOutConflictCommit
3524 [ + + ]: 13 : <= roXact->SeqNo.lastCommitBeforeSnapshot))
3525 : : {
3526 : : /*
3527 : : * This releases possibleUnsafeConflict (as well as all other
3528 : : * possible conflicts for roXact)
3529 : : */
3530 : 3 : FlagSxactUnsafe(roXact);
3531 : : }
3532 : : else
3533 : : {
3534 : 88 : ReleaseRWConflict(possibleUnsafeConflict);
3535 : :
3536 : : /*
3537 : : * If we were the last possible conflict, flag it safe. The
3538 : : * transaction can now safely release its predicate locks (but
3539 : : * that transaction's backend has to do that itself).
3540 : : */
3541 [ + + ]: 88 : if (dlist_is_empty(&roXact->possibleUnsafeConflicts))
3542 : 66 : roXact->flags |= SXACT_FLAG_RO_SAFE;
3543 : : }
3544 : :
3545 : : /*
3546 : : * Wake up the process for a waiting DEFERRABLE transaction if we
3547 : : * now know it's either safe or conflicted.
3548 : : */
3549 [ + + ]: 91 : if (SxactIsDeferrableWaiting(roXact) &&
3550 [ + + + - ]: 2 : (SxactIsROUnsafe(roXact) || SxactIsROSafe(roXact)))
3551 : 2 : ProcSendSignal(roXact->pgprocno);
3552 : : }
3553 : : }
3554 : :
3555 : : /*
3556 : : * Check whether it's time to clean up old transactions. This can only be
3557 : : * done when the last serializable transaction with the oldest xmin among
3558 : : * serializable transactions completes. We then find the "new oldest"
3559 : : * xmin and purge any transactions which finished before this transaction
3560 : : * was launched.
3561 : : *
3562 : : * For parallel queries in read-only transactions, it might run twice. We
3563 : : * only release the reference on the first call.
3564 : : */
3565 : 1578 : needToClear = false;
3566 [ + + ]: 1578 : if ((partiallyReleasing ||
3567 [ + + ]: 1576 : !SxactIsPartiallyReleased(MySerializableXact)) &&
3568 [ + + ]: 1576 : TransactionIdEquals(MySerializableXact->xmin,
3569 : : PredXact->SxactGlobalXmin))
3570 : : {
3571 : : Assert(PredXact->SxactGlobalXminCount > 0);
3572 [ + + ]: 1557 : if (--(PredXact->SxactGlobalXminCount) == 0)
3573 : : {
3574 : 897 : SetNewSxactGlobalXmin();
3575 : 897 : needToClear = true;
3576 : : }
3577 : : }
3578 : :
3579 : 1578 : LWLockRelease(SerializableXactHashLock);
3580 : :
3581 : 1578 : LWLockAcquire(SerializableFinishedListLock, LW_EXCLUSIVE);
3582 : :
3583 : : /* Add this to the list of transactions to check for later cleanup. */
3584 [ + + ]: 1578 : if (isCommit)
3585 : 1248 : dlist_push_tail(FinishedSerializableTransactions,
3586 : 1248 : &MySerializableXact->finishedLink);
3587 : :
3588 : : /*
3589 : : * If we're releasing a RO_SAFE transaction in parallel mode, we'll only
3590 : : * partially release it. That's necessary because other backends may have
3591 : : * a reference to it. The leader will release the SERIALIZABLEXACT itself
3592 : : * at the end of the transaction after workers have stopped running.
3593 : : */
3594 [ + + ]: 1578 : if (!isCommit)
3595 : 330 : ReleaseOneSerializableXact(MySerializableXact,
3596 [ + + + + ]: 330 : isReadOnlySafe && IsInParallelMode(),
3597 : 330 : false);
3598 : :
3599 : 1578 : LWLockRelease(SerializableFinishedListLock);
3600 : :
3601 [ + + ]: 1578 : if (needToClear)
3602 : 897 : ClearOldPredicateLocks();
3603 : :
3604 : 1578 : ReleasePredicateLocksLocal();
3605 : : }
3606 : :
3607 : : static void
3608 : 7614 : ReleasePredicateLocksLocal(void)
3609 : : {
3610 : 7614 : MySerializableXact = InvalidSerializableXact;
3611 : 7614 : MyXactDidWrite = false;
3612 : :
3613 : : /* Delete per-transaction lock table */
3614 [ + + ]: 7614 : if (LocalPredicateLockHash != NULL)
3615 : : {
3616 : 1577 : hash_destroy(LocalPredicateLockHash);
3617 : 1577 : LocalPredicateLockHash = NULL;
3618 : : }
3619 : 7614 : }
3620 : :
3621 : : /*
3622 : : * Clear old predicate locks, belonging to committed transactions that are no
3623 : : * longer interesting to any in-progress transaction.
3624 : : */
3625 : : static void
3626 : 897 : ClearOldPredicateLocks(void)
3627 : : {
3628 : : dlist_mutable_iter iter;
3629 : :
3630 : : /*
3631 : : * Loop through finished transactions. They are in commit order, so we can
3632 : : * stop as soon as we find one that's still interesting.
3633 : : */
3634 : 897 : LWLockAcquire(SerializableFinishedListLock, LW_EXCLUSIVE);
3635 : 897 : LWLockAcquire(SerializableXactHashLock, LW_SHARED);
3636 [ + - + + ]: 2152 : dlist_foreach_modify(iter, FinishedSerializableTransactions)
3637 : : {
3638 : 1263 : SERIALIZABLEXACT *finishedSxact =
3639 : 1263 : dlist_container(SERIALIZABLEXACT, finishedLink, iter.cur);
3640 : :
3641 [ + + ]: 1263 : if (!TransactionIdIsValid(PredXact->SxactGlobalXmin)
3642 [ + + ]: 25 : || TransactionIdPrecedesOrEquals(finishedSxact->finishedBefore,
3643 : 25 : PredXact->SxactGlobalXmin))
3644 : : {
3645 : : /*
3646 : : * This transaction committed before any in-progress transaction
3647 : : * took its snapshot. It's no longer interesting.
3648 : : */
3649 : 1248 : LWLockRelease(SerializableXactHashLock);
3650 : 1248 : dlist_delete_thoroughly(&finishedSxact->finishedLink);
3651 : 1248 : ReleaseOneSerializableXact(finishedSxact, false, false);
3652 : 1248 : LWLockAcquire(SerializableXactHashLock, LW_SHARED);
3653 : : }
3654 [ + - ]: 15 : else if (finishedSxact->commitSeqNo > PredXact->HavePartialClearedThrough
3655 [ + + ]: 15 : && finishedSxact->commitSeqNo <= PredXact->CanPartialClearThrough)
3656 : : {
3657 : : /*
3658 : : * Any active transactions that took their snapshot before this
3659 : : * transaction committed are read-only, so we can clear part of
3660 : : * its state.
3661 : : */
3662 : 7 : LWLockRelease(SerializableXactHashLock);
3663 : :
3664 [ - + ]: 7 : if (SxactIsReadOnly(finishedSxact))
3665 : : {
3666 : : /* A read-only transaction can be removed entirely */
3667 : 0 : dlist_delete_thoroughly(&(finishedSxact->finishedLink));
3668 : 0 : ReleaseOneSerializableXact(finishedSxact, false, false);
3669 : : }
3670 : : else
3671 : : {
3672 : : /*
3673 : : * A read-write transaction can only be partially cleared. We
3674 : : * need to keep the SERIALIZABLEXACT but can release the
3675 : : * SIREAD locks and conflicts in.
3676 : : */
3677 : 7 : ReleaseOneSerializableXact(finishedSxact, true, false);
3678 : : }
3679 : :
3680 : 7 : PredXact->HavePartialClearedThrough = finishedSxact->commitSeqNo;
3681 : 7 : LWLockAcquire(SerializableXactHashLock, LW_SHARED);
3682 : : }
3683 : : else
3684 : : {
3685 : : /* Still interesting. */
3686 : : break;
3687 : : }
3688 : : }
3689 : 897 : LWLockRelease(SerializableXactHashLock);
3690 : :
3691 : : /*
3692 : : * Loop through predicate locks on dummy transaction for summarized data.
3693 : : */
3694 : 897 : LWLockAcquire(SerializablePredicateListLock, LW_SHARED);
3695 [ + - - + ]: 897 : dlist_foreach_modify(iter, &OldCommittedSxact->predicateLocks)
3696 : : {
3697 : 0 : PREDICATELOCK *predlock =
3698 : 0 : dlist_container(PREDICATELOCK, xactLink, iter.cur);
3699 : : bool canDoPartialCleanup;
3700 : :
3701 : 0 : LWLockAcquire(SerializableXactHashLock, LW_SHARED);
3702 : : Assert(predlock->commitSeqNo != 0);
3703 : : Assert(predlock->commitSeqNo != InvalidSerCommitSeqNo);
3704 : 0 : canDoPartialCleanup = (predlock->commitSeqNo <= PredXact->CanPartialClearThrough);
3705 : 0 : LWLockRelease(SerializableXactHashLock);
3706 : :
3707 : : /*
3708 : : * If this lock originally belonged to an old enough transaction, we
3709 : : * can release it.
3710 : : */
3711 [ # # ]: 0 : if (canDoPartialCleanup)
3712 : : {
3713 : : PREDICATELOCKTAG tag;
3714 : : PREDICATELOCKTARGET *target;
3715 : : PREDICATELOCKTARGETTAG targettag;
3716 : : uint32 targettaghash;
3717 : : LWLock *partitionLock;
3718 : :
3719 : 0 : tag = predlock->tag;
3720 : 0 : target = tag.myTarget;
3721 : 0 : targettag = target->tag;
3722 : 0 : targettaghash = PredicateLockTargetTagHashCode(&targettag);
3723 : 0 : partitionLock = PredicateLockHashPartitionLock(targettaghash);
3724 : :
3725 : 0 : LWLockAcquire(partitionLock, LW_EXCLUSIVE);
3726 : :
3727 : 0 : dlist_delete(&(predlock->targetLink));
3728 : 0 : dlist_delete(&(predlock->xactLink));
3729 : :
3730 : 0 : hash_search_with_hash_value(PredicateLockHash, &tag,
3731 : 0 : PredicateLockHashCodeFromTargetHashCode(&tag,
3732 : : targettaghash),
3733 : : HASH_REMOVE, NULL);
3734 : 0 : RemoveTargetIfNoLongerUsed(target, targettaghash);
3735 : :
3736 : 0 : LWLockRelease(partitionLock);
3737 : : }
3738 : : }
3739 : :
3740 : 897 : LWLockRelease(SerializablePredicateListLock);
3741 : 897 : LWLockRelease(SerializableFinishedListLock);
3742 : 897 : }
3743 : :
3744 : : /*
3745 : : * This is the normal way to delete anything from any of the predicate
3746 : : * locking hash tables. Given a transaction which we know can be deleted:
3747 : : * delete all predicate locks held by that transaction and any predicate
3748 : : * lock targets which are now unreferenced by a lock; delete all conflicts
3749 : : * for the transaction; delete all xid values for the transaction; then
3750 : : * delete the transaction.
3751 : : *
3752 : : * When the partial flag is set, we can release all predicate locks and
3753 : : * in-conflict information -- we've established that there are no longer
3754 : : * any overlapping read write transactions for which this transaction could
3755 : : * matter -- but keep the transaction entry itself and any outConflicts.
3756 : : *
3757 : : * When the summarize flag is set, we've run short of room for sxact data
3758 : : * and must summarize to the SLRU. Predicate locks are transferred to a
3759 : : * dummy "old" transaction, with duplicate locks on a single target
3760 : : * collapsing to a single lock with the "latest" commitSeqNo from among
3761 : : * the conflicting locks..
3762 : : */
3763 : : static void
3764 : 1585 : ReleaseOneSerializableXact(SERIALIZABLEXACT *sxact, bool partial,
3765 : : bool summarize)
3766 : : {
3767 : : SERIALIZABLEXIDTAG sxidtag;
3768 : : dlist_mutable_iter iter;
3769 : :
3770 : : Assert(sxact != NULL);
3771 : : Assert(SxactIsRolledBack(sxact) || SxactIsCommitted(sxact));
3772 : : Assert(partial || !SxactIsOnFinishedList(sxact));
3773 : : Assert(LWLockHeldByMe(SerializableFinishedListLock));
3774 : :
3775 : : /*
3776 : : * First release all the predicate locks held by this xact (or transfer
3777 : : * them to OldCommittedSxact if summarize is true)
3778 : : */
3779 : 1585 : LWLockAcquire(SerializablePredicateListLock, LW_SHARED);
3780 [ + + ]: 1585 : if (IsInParallelMode())
3781 : 3 : LWLockAcquire(&sxact->perXactPredicateListLock, LW_EXCLUSIVE);
3782 [ + - + + ]: 4453 : dlist_foreach_modify(iter, &sxact->predicateLocks)
3783 : : {
3784 : 2868 : PREDICATELOCK *predlock =
3785 : 2868 : dlist_container(PREDICATELOCK, xactLink, iter.cur);
3786 : : PREDICATELOCKTAG tag;
3787 : : PREDICATELOCKTARGET *target;
3788 : : PREDICATELOCKTARGETTAG targettag;
3789 : : uint32 targettaghash;
3790 : : LWLock *partitionLock;
3791 : :
3792 : 2868 : tag = predlock->tag;
3793 : 2868 : target = tag.myTarget;
3794 : 2868 : targettag = target->tag;
3795 : 2868 : targettaghash = PredicateLockTargetTagHashCode(&targettag);
3796 : 2868 : partitionLock = PredicateLockHashPartitionLock(targettaghash);
3797 : :
3798 : 2868 : LWLockAcquire(partitionLock, LW_EXCLUSIVE);
3799 : :
3800 : 2868 : dlist_delete(&predlock->targetLink);
3801 : :
3802 : 2868 : hash_search_with_hash_value(PredicateLockHash, &tag,
3803 : 2868 : PredicateLockHashCodeFromTargetHashCode(&tag,
3804 : : targettaghash),
3805 : : HASH_REMOVE, NULL);
3806 [ - + ]: 2868 : if (summarize)
3807 : : {
3808 : : bool found;
3809 : :
3810 : : /* Fold into dummy transaction list. */
3811 : 0 : tag.myXact = OldCommittedSxact;
3812 : 0 : predlock = hash_search_with_hash_value(PredicateLockHash, &tag,
3813 : 0 : PredicateLockHashCodeFromTargetHashCode(&tag,
3814 : : targettaghash),
3815 : : HASH_ENTER_NULL, &found);
3816 [ # # ]: 0 : if (!predlock)
3817 [ # # ]: 0 : ereport(ERROR,
3818 : : (errcode(ERRCODE_OUT_OF_MEMORY),
3819 : : errmsg("out of shared memory"),
3820 : : errhint("You might need to increase \"%s\".", "max_pred_locks_per_transaction")));
3821 [ # # ]: 0 : if (found)
3822 : : {
3823 : : Assert(predlock->commitSeqNo != 0);
3824 : : Assert(predlock->commitSeqNo != InvalidSerCommitSeqNo);
3825 [ # # ]: 0 : if (predlock->commitSeqNo < sxact->commitSeqNo)
3826 : 0 : predlock->commitSeqNo = sxact->commitSeqNo;
3827 : : }
3828 : : else
3829 : : {
3830 : 0 : dlist_push_tail(&target->predicateLocks,
3831 : : &predlock->targetLink);
3832 : 0 : dlist_push_tail(&OldCommittedSxact->predicateLocks,
3833 : : &predlock->xactLink);
3834 : 0 : predlock->commitSeqNo = sxact->commitSeqNo;
3835 : : }
3836 : : }
3837 : : else
3838 : 2868 : RemoveTargetIfNoLongerUsed(target, targettaghash);
3839 : :
3840 : 2868 : LWLockRelease(partitionLock);
3841 : : }
3842 : :
3843 : : /*
3844 : : * Rather than retail removal, just re-init the head after we've run
3845 : : * through the list.
3846 : : */
3847 : 1585 : dlist_init(&sxact->predicateLocks);
3848 : :
3849 [ + + ]: 1585 : if (IsInParallelMode())
3850 : 3 : LWLockRelease(&sxact->perXactPredicateListLock);
3851 : 1585 : LWLockRelease(SerializablePredicateListLock);
3852 : :
3853 : 1585 : sxidtag.xid = sxact->topXid;
3854 : 1585 : LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
3855 : :
3856 : : /* Release all outConflicts (unless 'partial' is true) */
3857 [ + + ]: 1585 : if (!partial)
3858 : : {
3859 [ + - - + ]: 1576 : dlist_foreach_modify(iter, &sxact->outConflicts)
3860 : : {
3861 : 0 : RWConflict conflict =
3862 : : dlist_container(RWConflictData, outLink, iter.cur);
3863 : :
3864 [ # # ]: 0 : if (summarize)
3865 : 0 : conflict->sxactIn->flags |= SXACT_FLAG_SUMMARY_CONFLICT_IN;
3866 : 0 : ReleaseRWConflict(conflict);
3867 : : }
3868 : : }
3869 : :
3870 : : /* Release all inConflicts. */
3871 [ + - - + ]: 1585 : dlist_foreach_modify(iter, &sxact->inConflicts)
3872 : : {
3873 : 0 : RWConflict conflict =
3874 : 0 : dlist_container(RWConflictData, inLink, iter.cur);
3875 : :
3876 [ # # ]: 0 : if (summarize)
3877 : 0 : conflict->sxactOut->flags |= SXACT_FLAG_SUMMARY_CONFLICT_OUT;
3878 : 0 : ReleaseRWConflict(conflict);
3879 : : }
3880 : :
3881 : : /* Finally, get rid of the xid and the record of the transaction itself. */
3882 [ + + ]: 1585 : if (!partial)
3883 : : {
3884 [ + + ]: 1576 : if (sxidtag.xid != InvalidTransactionId)
3885 : 1302 : hash_search(SerializableXidHash, &sxidtag, HASH_REMOVE, NULL);
3886 : 1576 : ReleasePredXact(sxact);
3887 : : }
3888 : :
3889 : 1585 : LWLockRelease(SerializableXactHashLock);
3890 : 1585 : }
3891 : :
3892 : : /*
3893 : : * Tests whether the given top level transaction is concurrent with
3894 : : * (overlaps) our current transaction.
3895 : : *
3896 : : * We need to identify the top level transaction for SSI, anyway, so pass
3897 : : * that to this function to save the overhead of checking the snapshot's
3898 : : * subxip array.
3899 : : */
3900 : : static bool
3901 : 536 : XidIsConcurrent(TransactionId xid)
3902 : : {
3903 : : Snapshot snap;
3904 : :
3905 : : Assert(TransactionIdIsValid(xid));
3906 : : Assert(!TransactionIdEquals(xid, GetTopTransactionIdIfAny()));
3907 : :
3908 : 536 : snap = GetTransactionSnapshot();
3909 : :
3910 [ - + ]: 536 : if (TransactionIdPrecedes(xid, snap->xmin))
3911 : 0 : return false;
3912 : :
3913 [ + + ]: 536 : if (TransactionIdFollowsOrEquals(xid, snap->xmax))
3914 : 524 : return true;
3915 : :
3916 : 12 : return pg_lfind32(xid, snap->xip, snap->xcnt);
3917 : : }
3918 : :
3919 : : bool
3920 : 46008036 : CheckForSerializableConflictOutNeeded(Relation relation, Snapshot snapshot)
3921 : : {
3922 [ + + ]: 46008036 : if (!SerializationNeededForRead(relation, snapshot))
3923 : 45999460 : return false;
3924 : :
3925 : : /* Check if someone else has already decided that we need to die */
3926 [ - + ]: 8576 : if (SxactIsDoomed(MySerializableXact))
3927 : : {
3928 [ # # ]: 0 : ereport(ERROR,
3929 : : (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
3930 : : errmsg("could not serialize access due to read/write dependencies among transactions"),
3931 : : errdetail_internal("Reason code: Canceled on identification as a pivot, during conflict out checking."),
3932 : : errhint("The transaction might succeed if retried.")));
3933 : : }
3934 : :
3935 : 8576 : return true;
3936 : : }
3937 : :
3938 : : /*
3939 : : * CheckForSerializableConflictOut
3940 : : * A table AM is reading a tuple that has been modified. If it determines
3941 : : * that the tuple version it is reading is not visible to us, it should
3942 : : * pass in the top level xid of the transaction that created it.
3943 : : * Otherwise, if it determines that it is visible to us but it has been
3944 : : * deleted or there is a newer version available due to an update, it
3945 : : * should pass in the top level xid of the modifying transaction.
3946 : : *
3947 : : * This function will check for overlap with our own transaction. If the given
3948 : : * xid is also serializable and the transactions overlap (i.e., they cannot see
3949 : : * each other's writes), then we have a conflict out.
3950 : : */
3951 : : void
3952 : 567 : CheckForSerializableConflictOut(Relation relation, TransactionId xid, Snapshot snapshot)
3953 : : {
3954 : : SERIALIZABLEXIDTAG sxidtag;
3955 : : SERIALIZABLEXID *sxid;
3956 : : SERIALIZABLEXACT *sxact;
3957 : :
3958 [ - + ]: 567 : if (!SerializationNeededForRead(relation, snapshot))
3959 : 200 : return;
3960 : :
3961 : : /* Check if someone else has already decided that we need to die */
3962 [ - + ]: 567 : if (SxactIsDoomed(MySerializableXact))
3963 : : {
3964 [ # # ]: 0 : ereport(ERROR,
3965 : : (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
3966 : : errmsg("could not serialize access due to read/write dependencies among transactions"),
3967 : : errdetail_internal("Reason code: Canceled on identification as a pivot, during conflict out checking."),
3968 : : errhint("The transaction might succeed if retried.")));
3969 : : }
3970 : : Assert(TransactionIdIsValid(xid));
3971 : :
3972 [ - + ]: 567 : if (TransactionIdEquals(xid, GetTopTransactionIdIfAny()))
3973 : 0 : return;
3974 : :
3975 : : /*
3976 : : * Find sxact or summarized info for the top level xid.
3977 : : */
3978 : 567 : sxidtag.xid = xid;
3979 : 567 : LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
3980 : : sxid = (SERIALIZABLEXID *)
3981 : 567 : hash_search(SerializableXidHash, &sxidtag, HASH_FIND, NULL);
3982 [ + + ]: 567 : if (!sxid)
3983 : : {
3984 : : /*
3985 : : * Transaction not found in "normal" SSI structures. Check whether it
3986 : : * got pushed out to SLRU storage for "old committed" transactions.
3987 : : */
3988 : : SerCommitSeqNo conflictCommitSeqNo;
3989 : :
3990 : 21 : conflictCommitSeqNo = SerialGetMinConflictCommitSeqNo(xid);
3991 [ - + ]: 21 : if (conflictCommitSeqNo != 0)
3992 : : {
3993 [ # # ]: 0 : if (conflictCommitSeqNo != InvalidSerCommitSeqNo
3994 [ # # ]: 0 : && (!SxactIsReadOnly(MySerializableXact)
3995 : 0 : || conflictCommitSeqNo
3996 [ # # ]: 0 : <= MySerializableXact->SeqNo.lastCommitBeforeSnapshot))
3997 [ # # ]: 0 : ereport(ERROR,
3998 : : (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
3999 : : errmsg("could not serialize access due to read/write dependencies among transactions"),
4000 : : errdetail_internal("Reason code: Canceled on conflict out to old pivot %u.", xid),
4001 : : errhint("The transaction might succeed if retried.")));
4002 : :
4003 [ # # ]: 0 : if (SxactHasSummaryConflictIn(MySerializableXact)
4004 [ # # ]: 0 : || !dlist_is_empty(&MySerializableXact->inConflicts))
4005 [ # # ]: 0 : ereport(ERROR,
4006 : : (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
4007 : : errmsg("could not serialize access due to read/write dependencies among transactions"),
4008 : : errdetail_internal("Reason code: Canceled on identification as a pivot, with conflict out to old committed transaction %u.", xid),
4009 : : errhint("The transaction might succeed if retried.")));
4010 : :
4011 : 0 : MySerializableXact->flags |= SXACT_FLAG_SUMMARY_CONFLICT_OUT;
4012 : : }
4013 : :
4014 : : /* It's not serializable or otherwise not important. */
4015 : 21 : LWLockRelease(SerializableXactHashLock);
4016 : 21 : return;
4017 : : }
4018 : 546 : sxact = sxid->myXact;
4019 : : Assert(TransactionIdEquals(sxact->topXid, xid));
4020 [ + - + + ]: 546 : if (sxact == MySerializableXact || SxactIsDoomed(sxact))
4021 : : {
4022 : : /* Can't conflict with ourself or a transaction that will roll back. */
4023 : 4 : LWLockRelease(SerializableXactHashLock);
4024 : 4 : return;
4025 : : }
4026 : :
4027 : : /*
4028 : : * We have a conflict out to a transaction which has a conflict out to a
4029 : : * summarized transaction. That summarized transaction must have
4030 : : * committed first, and we can't tell when it committed in relation to our
4031 : : * snapshot acquisition, so something needs to be canceled.
4032 : : */
4033 [ - + ]: 542 : if (SxactHasSummaryConflictOut(sxact))
4034 : : {
4035 [ # # ]: 0 : if (!SxactIsPrepared(sxact))
4036 : : {
4037 : 0 : sxact->flags |= SXACT_FLAG_DOOMED;
4038 : 0 : LWLockRelease(SerializableXactHashLock);
4039 : 0 : return;
4040 : : }
4041 : : else
4042 : : {
4043 : 0 : LWLockRelease(SerializableXactHashLock);
4044 [ # # ]: 0 : ereport(ERROR,
4045 : : (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
4046 : : errmsg("could not serialize access due to read/write dependencies among transactions"),
4047 : : errdetail_internal("Reason code: Canceled on conflict out to old pivot."),
4048 : : errhint("The transaction might succeed if retried.")));
4049 : : }
4050 : : }
4051 : :
4052 : : /*
4053 : : * If this is a read-only transaction and the writing transaction has
4054 : : * committed, and it doesn't have a rw-conflict to a transaction which
4055 : : * committed before it, no conflict.
4056 : : */
4057 [ + + ]: 542 : if (SxactIsReadOnly(MySerializableXact)
4058 [ + + ]: 119 : && SxactIsCommitted(sxact)
4059 [ + - ]: 8 : && !SxactHasSummaryConflictOut(sxact)
4060 [ + + ]: 8 : && (!SxactHasConflictOut(sxact)
4061 [ - + ]: 2 : || MySerializableXact->SeqNo.lastCommitBeforeSnapshot < sxact->SeqNo.earliestOutConflictCommit))
4062 : : {
4063 : : /* Read-only transaction will appear to run first. No conflict. */
4064 : 6 : LWLockRelease(SerializableXactHashLock);
4065 : 6 : return;
4066 : : }
4067 : :
4068 [ - + ]: 536 : if (!XidIsConcurrent(xid))
4069 : : {
4070 : : /* This write was already in our snapshot; no conflict. */
4071 : 0 : LWLockRelease(SerializableXactHashLock);
4072 : 0 : return;
4073 : : }
4074 : :
4075 [ + + ]: 536 : if (RWConflictExists(MySerializableXact, sxact))
4076 : : {
4077 : : /* We don't want duplicate conflict records in the list. */
4078 : 169 : LWLockRelease(SerializableXactHashLock);
4079 : 169 : return;
4080 : : }
4081 : :
4082 : : /*
4083 : : * Flag the conflict. But first, if this conflict creates a dangerous
4084 : : * structure, ereport an error.
4085 : : */
4086 : 367 : FlagRWConflict(MySerializableXact, sxact);
4087 : 354 : LWLockRelease(SerializableXactHashLock);
4088 : : }
4089 : :
4090 : : /*
4091 : : * Check a particular target for rw-dependency conflict in. A subroutine of
4092 : : * CheckForSerializableConflictIn().
4093 : : */
4094 : : static void
4095 : 7616 : CheckTargetForConflictsIn(PREDICATELOCKTARGETTAG *targettag)
4096 : : {
4097 : : uint32 targettaghash;
4098 : : LWLock *partitionLock;
4099 : : PREDICATELOCKTARGET *target;
4100 : 7616 : PREDICATELOCK *mypredlock = NULL;
4101 : : PREDICATELOCKTAG mypredlocktag;
4102 : : dlist_mutable_iter iter;
4103 : :
4104 : : Assert(MySerializableXact != InvalidSerializableXact);
4105 : :
4106 : : /*
4107 : : * The same hash and LW lock apply to the lock target and the lock itself.
4108 : : */
4109 : 7616 : targettaghash = PredicateLockTargetTagHashCode(targettag);
4110 : 7616 : partitionLock = PredicateLockHashPartitionLock(targettaghash);
4111 : 7616 : LWLockAcquire(partitionLock, LW_SHARED);
4112 : : target = (PREDICATELOCKTARGET *)
4113 : 7616 : hash_search_with_hash_value(PredicateLockTargetHash,
4114 : : targettag, targettaghash,
4115 : : HASH_FIND, NULL);
4116 [ + + ]: 7616 : if (!target)
4117 : : {
4118 : : /* Nothing has this target locked; we're done here. */
4119 : 5711 : LWLockRelease(partitionLock);
4120 : 5711 : return;
4121 : : }
4122 : :
4123 : : /*
4124 : : * Each lock for an overlapping transaction represents a conflict: a
4125 : : * rw-dependency in to this transaction.
4126 : : */
4127 : 1905 : LWLockAcquire(SerializableXactHashLock, LW_SHARED);
4128 : :
4129 [ + - + + ]: 4290 : dlist_foreach_modify(iter, &target->predicateLocks)
4130 : : {
4131 : 2452 : PREDICATELOCK *predlock =
4132 : 2452 : dlist_container(PREDICATELOCK, targetLink, iter.cur);
4133 : 2452 : SERIALIZABLEXACT *sxact = predlock->tag.myXact;
4134 : :
4135 [ + + ]: 2452 : if (sxact == MySerializableXact)
4136 : : {
4137 : : /*
4138 : : * If we're getting a write lock on a tuple, we don't need a
4139 : : * predicate (SIREAD) lock on the same tuple. We can safely remove
4140 : : * our SIREAD lock, but we'll defer doing so until after the loop
4141 : : * because that requires upgrading to an exclusive partition lock.
4142 : : *
4143 : : * We can't use this optimization within a subtransaction because
4144 : : * the subtransaction could roll back, and we would be left
4145 : : * without any lock at the top level.
4146 : : */
4147 [ + - ]: 1594 : if (!IsSubTransaction()
4148 [ + + ]: 1594 : && GET_PREDICATELOCKTARGETTAG_OFFSET(*targettag))
4149 : : {
4150 : 401 : mypredlock = predlock;
4151 : 401 : mypredlocktag = predlock->tag;
4152 : : }
4153 : : }
4154 [ + - ]: 858 : else if (!SxactIsDoomed(sxact)
4155 [ + + ]: 858 : && (!SxactIsCommitted(sxact)
4156 [ + + ]: 87 : || TransactionIdPrecedes(GetTransactionSnapshot()->xmin,
4157 : : sxact->finishedBefore))
4158 [ + + ]: 849 : && !RWConflictExists(sxact, MySerializableXact))
4159 : : {
4160 : 505 : LWLockRelease(SerializableXactHashLock);
4161 : 505 : LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
4162 : :
4163 : : /*
4164 : : * Re-check after getting exclusive lock because the other
4165 : : * transaction may have flagged a conflict.
4166 : : */
4167 [ + - ]: 505 : if (!SxactIsDoomed(sxact)
4168 [ + + ]: 505 : && (!SxactIsCommitted(sxact)
4169 [ + - ]: 77 : || TransactionIdPrecedes(GetTransactionSnapshot()->xmin,
4170 : : sxact->finishedBefore))
4171 [ + - ]: 505 : && !RWConflictExists(sxact, MySerializableXact))
4172 : : {
4173 : 505 : FlagRWConflict(sxact, MySerializableXact);
4174 : : }
4175 : :
4176 : 438 : LWLockRelease(SerializableXactHashLock);
4177 : 438 : LWLockAcquire(SerializableXactHashLock, LW_SHARED);
4178 : : }
4179 : : }
4180 : 1838 : LWLockRelease(SerializableXactHashLock);
4181 : 1838 : LWLockRelease(partitionLock);
4182 : :
4183 : : /*
4184 : : * If we found one of our own SIREAD locks to remove, remove it now.
4185 : : *
4186 : : * At this point our transaction already has a RowExclusiveLock on the
4187 : : * relation, so we are OK to drop the predicate lock on the tuple, if
4188 : : * found, without fearing that another write against the tuple will occur
4189 : : * before the MVCC information makes it to the buffer.
4190 : : */
4191 [ + + ]: 1838 : if (mypredlock != NULL)
4192 : : {
4193 : : uint32 predlockhashcode;
4194 : : PREDICATELOCK *rmpredlock;
4195 : :
4196 : 394 : LWLockAcquire(SerializablePredicateListLock, LW_SHARED);
4197 [ - + ]: 394 : if (IsInParallelMode())
4198 : 0 : LWLockAcquire(&MySerializableXact->perXactPredicateListLock, LW_EXCLUSIVE);
4199 : 394 : LWLockAcquire(partitionLock, LW_EXCLUSIVE);
4200 : 394 : LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
4201 : :
4202 : : /*
4203 : : * Remove the predicate lock from shared memory, if it wasn't removed
4204 : : * while the locks were released. One way that could happen is from
4205 : : * autovacuum cleaning up an index.
4206 : : */
4207 : 394 : predlockhashcode = PredicateLockHashCodeFromTargetHashCode
4208 : : (&mypredlocktag, targettaghash);
4209 : : rmpredlock = (PREDICATELOCK *)
4210 : 394 : hash_search_with_hash_value(PredicateLockHash,
4211 : : &mypredlocktag,
4212 : : predlockhashcode,
4213 : : HASH_FIND, NULL);
4214 [ + - ]: 394 : if (rmpredlock != NULL)
4215 : : {
4216 : : Assert(rmpredlock == mypredlock);
4217 : :
4218 : 394 : dlist_delete(&(mypredlock->targetLink));
4219 : 394 : dlist_delete(&(mypredlock->xactLink));
4220 : :
4221 : : rmpredlock = (PREDICATELOCK *)
4222 : 394 : hash_search_with_hash_value(PredicateLockHash,
4223 : : &mypredlocktag,
4224 : : predlockhashcode,
4225 : : HASH_REMOVE, NULL);
4226 : : Assert(rmpredlock == mypredlock);
4227 : :
4228 : 394 : RemoveTargetIfNoLongerUsed(target, targettaghash);
4229 : : }
4230 : :
4231 : 394 : LWLockRelease(SerializableXactHashLock);
4232 : 394 : LWLockRelease(partitionLock);
4233 [ - + ]: 394 : if (IsInParallelMode())
4234 : 0 : LWLockRelease(&MySerializableXact->perXactPredicateListLock);
4235 : 394 : LWLockRelease(SerializablePredicateListLock);
4236 : :
4237 [ + - ]: 394 : if (rmpredlock != NULL)
4238 : : {
4239 : : /*
4240 : : * Remove entry in local lock table if it exists. It's OK if it
4241 : : * doesn't exist; that means the lock was transferred to a new
4242 : : * target by a different backend.
4243 : : */
4244 : 394 : hash_search_with_hash_value(LocalPredicateLockHash,
4245 : : targettag, targettaghash,
4246 : : HASH_REMOVE, NULL);
4247 : :
4248 : 394 : DecrementParentLocks(targettag);
4249 : : }
4250 : : }
4251 : : }
4252 : :
4253 : : /*
4254 : : * CheckForSerializableConflictIn
4255 : : * We are writing the given tuple. If that indicates a rw-conflict
4256 : : * in from another serializable transaction, take appropriate action.
4257 : : *
4258 : : * Skip checking for any granularity for which a parameter is missing.
4259 : : *
4260 : : * A tuple update or delete is in conflict if we have a predicate lock
4261 : : * against the relation or page in which the tuple exists, or against the
4262 : : * tuple itself.
4263 : : */
4264 : : void
4265 : 25222628 : CheckForSerializableConflictIn(Relation relation, const ItemPointerData *tid, BlockNumber blkno)
4266 : : {
4267 : : PREDICATELOCKTARGETTAG targettag;
4268 : :
4269 [ + + ]: 25222628 : if (!SerializationNeededForWrite(relation))
4270 : 25218122 : return;
4271 : :
4272 : : /* Check if someone else has already decided that we need to die */
4273 [ + + ]: 4506 : if (SxactIsDoomed(MySerializableXact))
4274 [ + - ]: 1 : ereport(ERROR,
4275 : : (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
4276 : : errmsg("could not serialize access due to read/write dependencies among transactions"),
4277 : : errdetail_internal("Reason code: Canceled on identification as a pivot, during conflict in checking."),
4278 : : errhint("The transaction might succeed if retried.")));
4279 : :
4280 : : /*
4281 : : * We're doing a write which might cause rw-conflicts now or later.
4282 : : * Memorize that fact.
4283 : : */
4284 : 4505 : MyXactDidWrite = true;
4285 : :
4286 : : /*
4287 : : * It is important that we check for locks from the finest granularity to
4288 : : * the coarsest granularity, so that granularity promotion doesn't cause
4289 : : * us to miss a lock. The new (coarser) lock will be acquired before the
4290 : : * old (finer) locks are released.
4291 : : *
4292 : : * It is not possible to take and hold a lock across the checks for all
4293 : : * granularities because each target could be in a separate partition.
4294 : : */
4295 [ + + ]: 4505 : if (tid != NULL)
4296 : : {
4297 : 657 : SET_PREDICATELOCKTARGETTAG_TUPLE(targettag,
4298 : : relation->rd_locator.dbOid,
4299 : : relation->rd_id,
4300 : : ItemPointerGetBlockNumber(tid),
4301 : : ItemPointerGetOffsetNumber(tid));
4302 : 657 : CheckTargetForConflictsIn(&targettag);
4303 : : }
4304 : :
4305 [ + + ]: 4482 : if (blkno != InvalidBlockNumber)
4306 : : {
4307 : 2507 : SET_PREDICATELOCKTARGETTAG_PAGE(targettag,
4308 : : relation->rd_locator.dbOid,
4309 : : relation->rd_id,
4310 : : blkno);
4311 : 2507 : CheckTargetForConflictsIn(&targettag);
4312 : : }
4313 : :
4314 : 4452 : SET_PREDICATELOCKTARGETTAG_RELATION(targettag,
4315 : : relation->rd_locator.dbOid,
4316 : : relation->rd_id);
4317 : 4452 : CheckTargetForConflictsIn(&targettag);
4318 : : }
4319 : :
4320 : : /*
4321 : : * CheckTableForSerializableConflictIn
4322 : : * The entire table is going through a DDL-style logical mass delete
4323 : : * like TRUNCATE or DROP TABLE. If that causes a rw-conflict in from
4324 : : * another serializable transaction, take appropriate action.
4325 : : *
4326 : : * While these operations do not operate entirely within the bounds of
4327 : : * snapshot isolation, they can occur inside a serializable transaction, and
4328 : : * will logically occur after any reads which saw rows which were destroyed
4329 : : * by these operations, so we do what we can to serialize properly under
4330 : : * SSI.
4331 : : *
4332 : : * The relation passed in must be a heap relation. Any predicate lock of any
4333 : : * granularity on the heap will cause a rw-conflict in to this transaction.
4334 : : * Predicate locks on indexes do not matter because they only exist to guard
4335 : : * against conflicting inserts into the index, and this is a mass *delete*.
4336 : : * When a table is truncated or dropped, the index will also be truncated
4337 : : * or dropped, and we'll deal with locks on the index when that happens.
4338 : : *
4339 : : * Dropping or truncating a table also needs to drop any existing predicate
4340 : : * locks on heap tuples or pages, because they're about to go away. This
4341 : : * should be done before altering the predicate locks because the transaction
4342 : : * could be rolled back because of a conflict, in which case the lock changes
4343 : : * are not needed. (At the moment, we don't actually bother to drop the
4344 : : * existing locks on a dropped or truncated table at the moment. That might
4345 : : * lead to some false positives, but it doesn't seem worth the trouble.)
4346 : : */
4347 : : void
4348 : 36178 : CheckTableForSerializableConflictIn(Relation relation)
4349 : : {
4350 : : HASH_SEQ_STATUS seqstat;
4351 : : PREDICATELOCKTARGET *target;
4352 : : Oid dbId;
4353 : : Oid heapId;
4354 : : int i;
4355 : :
4356 : : /*
4357 : : * Bail out quickly if there are no serializable transactions running.
4358 : : * It's safe to check this without taking locks because the caller is
4359 : : * holding an ACCESS EXCLUSIVE lock on the relation. No new locks which
4360 : : * would matter here can be acquired while that is held.
4361 : : */
4362 [ + + ]: 36178 : if (!TransactionIdIsValid(PredXact->SxactGlobalXmin))
4363 : 36158 : return;
4364 : :
4365 [ + + ]: 152 : if (!SerializationNeededForWrite(relation))
4366 : 132 : return;
4367 : :
4368 : : /*
4369 : : * We're doing a write which might cause rw-conflicts now or later.
4370 : : * Memorize that fact.
4371 : : */
4372 : 20 : MyXactDidWrite = true;
4373 : :
4374 : : Assert(relation->rd_index == NULL); /* not an index relation */
4375 : :
4376 : 20 : dbId = relation->rd_locator.dbOid;
4377 : 20 : heapId = relation->rd_id;
4378 : :
4379 : 20 : LWLockAcquire(SerializablePredicateListLock, LW_EXCLUSIVE);
4380 [ + + ]: 340 : for (i = 0; i < NUM_PREDICATELOCK_PARTITIONS; i++)
4381 : 320 : LWLockAcquire(PredicateLockHashPartitionLockByIndex(i), LW_SHARED);
4382 : 20 : LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
4383 : :
4384 : : /* Scan through target list */
4385 : 20 : hash_seq_init(&seqstat, PredicateLockTargetHash);
4386 : :
4387 [ + + ]: 70 : while ((target = (PREDICATELOCKTARGET *) hash_seq_search(&seqstat)))
4388 : : {
4389 : : dlist_mutable_iter iter;
4390 : :
4391 : : /*
4392 : : * Check whether this is a target which needs attention.
4393 : : */
4394 [ + + ]: 50 : if (GET_PREDICATELOCKTARGETTAG_RELATION(target->tag) != heapId)
4395 : 41 : continue; /* wrong relation id */
4396 [ - + ]: 9 : if (GET_PREDICATELOCKTARGETTAG_DB(target->tag) != dbId)
4397 : 0 : continue; /* wrong database id */
4398 : :
4399 : : /*
4400 : : * Loop through locks for this target and flag conflicts.
4401 : : */
4402 [ + - + + ]: 18 : dlist_foreach_modify(iter, &target->predicateLocks)
4403 : : {
4404 : 9 : PREDICATELOCK *predlock =
4405 : 9 : dlist_container(PREDICATELOCK, targetLink, iter.cur);
4406 : :
4407 [ - + ]: 9 : if (predlock->tag.myXact != MySerializableXact
4408 [ # # ]: 0 : && !RWConflictExists(predlock->tag.myXact, MySerializableXact))
4409 : : {
4410 : 0 : FlagRWConflict(predlock->tag.myXact, MySerializableXact);
4411 : : }
4412 : : }
4413 : : }
4414 : :
4415 : : /* Release locks in reverse order */
4416 : 20 : LWLockRelease(SerializableXactHashLock);
4417 [ + + ]: 340 : for (i = NUM_PREDICATELOCK_PARTITIONS - 1; i >= 0; i--)
4418 : 320 : LWLockRelease(PredicateLockHashPartitionLockByIndex(i));
4419 : 20 : LWLockRelease(SerializablePredicateListLock);
4420 : : }
4421 : :
4422 : :
4423 : : /*
4424 : : * Flag a rw-dependency between two serializable transactions.
4425 : : *
4426 : : * The caller is responsible for ensuring that we have a LW lock on
4427 : : * the transaction hash table.
4428 : : */
4429 : : static void
4430 : 872 : FlagRWConflict(SERIALIZABLEXACT *reader, SERIALIZABLEXACT *writer)
4431 : : {
4432 : : Assert(reader != writer);
4433 : :
4434 : : /* First, see if this conflict causes failure. */
4435 : 872 : OnConflict_CheckForSerializationFailure(reader, writer);
4436 : :
4437 : : /* Actually do the conflict flagging. */
4438 [ - + ]: 792 : if (reader == OldCommittedSxact)
4439 : 0 : writer->flags |= SXACT_FLAG_SUMMARY_CONFLICT_IN;
4440 [ - + ]: 792 : else if (writer == OldCommittedSxact)
4441 : 0 : reader->flags |= SXACT_FLAG_SUMMARY_CONFLICT_OUT;
4442 : : else
4443 : 792 : SetRWConflict(reader, writer);
4444 : 792 : }
4445 : :
4446 : : /*----------------------------------------------------------------------------
4447 : : * We are about to add a RW-edge to the dependency graph - check that we don't
4448 : : * introduce a dangerous structure by doing so, and abort one of the
4449 : : * transactions if so.
4450 : : *
4451 : : * A serialization failure can only occur if there is a dangerous structure
4452 : : * in the dependency graph:
4453 : : *
4454 : : * Tin ------> Tpivot ------> Tout
4455 : : * rw rw
4456 : : *
4457 : : * Furthermore, Tout must commit first.
4458 : : *
4459 : : * One more optimization is that if Tin is declared READ ONLY (or commits
4460 : : * without writing), we can only have a problem if Tout committed before Tin
4461 : : * acquired its snapshot.
4462 : : *----------------------------------------------------------------------------
4463 : : */
4464 : : static void
4465 : 872 : OnConflict_CheckForSerializationFailure(const SERIALIZABLEXACT *reader,
4466 : : SERIALIZABLEXACT *writer)
4467 : : {
4468 : : bool failure;
4469 : :
4470 : : Assert(LWLockHeldByMe(SerializableXactHashLock));
4471 : :
4472 : 872 : failure = false;
4473 : :
4474 : : /*------------------------------------------------------------------------
4475 : : * Check for already-committed writer with rw-conflict out flagged
4476 : : * (conflict-flag on W means that T2 committed before W):
4477 : : *
4478 : : * R ------> W ------> T2
4479 : : * rw rw
4480 : : *
4481 : : * That is a dangerous structure, so we must abort. (Since the writer
4482 : : * has already committed, we must be the reader)
4483 : : *------------------------------------------------------------------------
4484 : : */
4485 [ + + ]: 872 : if (SxactIsCommitted(writer)
4486 [ + + - + ]: 18 : && (SxactHasConflictOut(writer) || SxactHasSummaryConflictOut(writer)))
4487 : 2 : failure = true;
4488 : :
4489 : : /*------------------------------------------------------------------------
4490 : : * Check whether the writer has become a pivot with an out-conflict
4491 : : * committed transaction (T2), and T2 committed first:
4492 : : *
4493 : : * R ------> W ------> T2
4494 : : * rw rw
4495 : : *
4496 : : * Because T2 must've committed first, there is no anomaly if:
4497 : : * - the reader committed before T2
4498 : : * - the writer committed before T2
4499 : : * - the reader is a READ ONLY transaction and the reader was concurrent
4500 : : * with T2 (= reader acquired its snapshot before T2 committed)
4501 : : *
4502 : : * We also handle the case that T2 is prepared but not yet committed
4503 : : * here. In that case T2 has already checked for conflicts, so if it
4504 : : * commits first, making the above conflict real, it's too late for it
4505 : : * to abort.
4506 : : *------------------------------------------------------------------------
4507 : : */
4508 [ + + - + ]: 872 : if (!failure && SxactHasSummaryConflictOut(writer))
4509 : 0 : failure = true;
4510 [ + + ]: 872 : else if (!failure)
4511 : : {
4512 : : dlist_iter iter;
4513 : :
4514 [ + - + + ]: 1087 : dlist_foreach(iter, &writer->outConflicts)
4515 : : {
4516 : 292 : RWConflict conflict =
4517 : : dlist_container(RWConflictData, outLink, iter.cur);
4518 : 292 : SERIALIZABLEXACT *t2 = conflict->sxactIn;
4519 : :
4520 [ + + ]: 292 : if (SxactIsPrepared(t2)
4521 [ + + ]: 81 : && (!SxactIsCommitted(reader)
4522 [ + - ]: 65 : || t2->prepareSeqNo <= reader->commitSeqNo)
4523 [ - + ]: 81 : && (!SxactIsCommitted(writer)
4524 [ # # ]: 0 : || t2->prepareSeqNo <= writer->commitSeqNo)
4525 [ + + ]: 81 : && (!SxactIsReadOnly(reader)
4526 [ + + ]: 12 : || t2->prepareSeqNo <= reader->SeqNo.lastCommitBeforeSnapshot))
4527 : : {
4528 : 75 : failure = true;
4529 : 75 : break;
4530 : : }
4531 : : }
4532 : : }
4533 : :
4534 : : /*------------------------------------------------------------------------
4535 : : * Check whether the reader has become a pivot with a writer
4536 : : * that's committed (or prepared):
4537 : : *
4538 : : * T0 ------> R ------> W
4539 : : * rw rw
4540 : : *
4541 : : * Because W must've committed first for an anomaly to occur, there is no
4542 : : * anomaly if:
4543 : : * - T0 committed before the writer
4544 : : * - T0 is READ ONLY, and overlaps the writer
4545 : : *------------------------------------------------------------------------
4546 : : */
4547 [ + + + + : 872 : if (!failure && SxactIsPrepared(writer) && !SxactIsReadOnly(reader))
+ - ]
4548 : : {
4549 [ - + ]: 18 : if (SxactHasSummaryConflictIn(reader))
4550 : : {
4551 : 0 : failure = true;
4552 : : }
4553 : : else
4554 : : {
4555 : : dlist_iter iter;
4556 : :
4557 : : /*
4558 : : * The unconstify is needed as we have no const version of
4559 : : * dlist_foreach().
4560 : : */
4561 [ + - + + ]: 18 : dlist_foreach(iter, &unconstify(SERIALIZABLEXACT *, reader)->inConflicts)
4562 : : {
4563 : 11 : const RWConflict conflict =
4564 : 11 : dlist_container(RWConflictData, inLink, iter.cur);
4565 : 11 : const SERIALIZABLEXACT *t0 = conflict->sxactOut;
4566 : :
4567 [ + - ]: 11 : if (!SxactIsDoomed(t0)
4568 [ + - ]: 11 : && (!SxactIsCommitted(t0)
4569 [ + - ]: 11 : || t0->commitSeqNo >= writer->prepareSeqNo)
4570 [ - + ]: 11 : && (!SxactIsReadOnly(t0)
4571 [ # # ]: 0 : || t0->SeqNo.lastCommitBeforeSnapshot >= writer->prepareSeqNo))
4572 : : {
4573 : 11 : failure = true;
4574 : 11 : break;
4575 : : }
4576 : : }
4577 : : }
4578 : : }
4579 : :
4580 [ + + ]: 872 : if (failure)
4581 : : {
4582 : : /*
4583 : : * We have to kill a transaction to avoid a possible anomaly from
4584 : : * occurring. If the writer is us, we can just ereport() to cause a
4585 : : * transaction abort. Otherwise we flag the writer for termination,
4586 : : * causing it to abort when it tries to commit. However, if the writer
4587 : : * is a prepared transaction, already prepared, we can't abort it
4588 : : * anymore, so we have to kill the reader instead.
4589 : : */
4590 [ + + ]: 88 : if (MySerializableXact == writer)
4591 : : {
4592 : 67 : LWLockRelease(SerializableXactHashLock);
4593 [ + - ]: 67 : ereport(ERROR,
4594 : : (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
4595 : : errmsg("could not serialize access due to read/write dependencies among transactions"),
4596 : : errdetail_internal("Reason code: Canceled on identification as a pivot, during write."),
4597 : : errhint("The transaction might succeed if retried.")));
4598 : : }
4599 [ + + ]: 21 : else if (SxactIsPrepared(writer))
4600 : : {
4601 : 13 : LWLockRelease(SerializableXactHashLock);
4602 : :
4603 : : /* if we're not the writer, we have to be the reader */
4604 : : Assert(MySerializableXact == reader);
4605 [ + - ]: 13 : ereport(ERROR,
4606 : : (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
4607 : : errmsg("could not serialize access due to read/write dependencies among transactions"),
4608 : : errdetail_internal("Reason code: Canceled on conflict out to pivot %u, during read.", writer->topXid),
4609 : : errhint("The transaction might succeed if retried.")));
4610 : : }
4611 : 8 : writer->flags |= SXACT_FLAG_DOOMED;
4612 : : }
4613 : 792 : }
4614 : :
4615 : : /*
4616 : : * PreCommit_CheckForSerializationFailure
4617 : : * Check for dangerous structures in a serializable transaction
4618 : : * at commit.
4619 : : *
4620 : : * We're checking for a dangerous structure as each conflict is recorded.
4621 : : * The only way we could have a problem at commit is if this is the "out"
4622 : : * side of a pivot, and neither the "in" side nor the pivot has yet
4623 : : * committed.
4624 : : *
4625 : : * If a dangerous structure is found, the pivot (the near conflict) is
4626 : : * marked for death, because rolling back another transaction might mean
4627 : : * that we fail without ever making progress. This transaction is
4628 : : * committing writes, so letting it commit ensures progress. If we
4629 : : * canceled the far conflict, it might immediately fail again on retry.
4630 : : */
4631 : : void
4632 : 631044 : PreCommit_CheckForSerializationFailure(void)
4633 : : {
4634 : : dlist_iter near_iter;
4635 : :
4636 [ + + ]: 631044 : if (MySerializableXact == InvalidSerializableXact)
4637 : 629632 : return;
4638 : :
4639 : : Assert(IsolationIsSerializable());
4640 : :
4641 : 1412 : LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
4642 : :
4643 : : /*
4644 : : * Check if someone else has already decided that we need to die. Since
4645 : : * we set our own DOOMED flag when partially releasing, ignore in that
4646 : : * case.
4647 : : */
4648 [ + + ]: 1412 : if (SxactIsDoomed(MySerializableXact) &&
4649 [ + + ]: 156 : !SxactIsPartiallyReleased(MySerializableXact))
4650 : : {
4651 : 155 : LWLockRelease(SerializableXactHashLock);
4652 [ + - ]: 155 : ereport(ERROR,
4653 : : (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
4654 : : errmsg("could not serialize access due to read/write dependencies among transactions"),
4655 : : errdetail_internal("Reason code: Canceled on identification as a pivot, during commit attempt."),
4656 : : errhint("The transaction might succeed if retried.")));
4657 : : }
4658 : :
4659 [ + - + + ]: 1863 : dlist_foreach(near_iter, &MySerializableXact->inConflicts)
4660 : : {
4661 : 606 : RWConflict nearConflict =
4662 : 606 : dlist_container(RWConflictData, inLink, near_iter.cur);
4663 : :
4664 [ + + ]: 606 : if (!SxactIsCommitted(nearConflict->sxactOut)
4665 [ + - ]: 421 : && !SxactIsDoomed(nearConflict->sxactOut))
4666 : : {
4667 : : dlist_iter far_iter;
4668 : :
4669 [ + - + + ]: 451 : dlist_foreach(far_iter, &nearConflict->sxactOut->inConflicts)
4670 : : {
4671 : 182 : RWConflict farConflict =
4672 : 182 : dlist_container(RWConflictData, inLink, far_iter.cur);
4673 : :
4674 [ + + ]: 182 : if (farConflict->sxactOut == MySerializableXact
4675 [ + + ]: 42 : || (!SxactIsCommitted(farConflict->sxactOut)
4676 [ + + ]: 24 : && !SxactIsReadOnly(farConflict->sxactOut)
4677 [ + - ]: 12 : && !SxactIsDoomed(farConflict->sxactOut)))
4678 : : {
4679 : : /*
4680 : : * Normally, we kill the pivot transaction to make sure we
4681 : : * make progress if the failing transaction is retried.
4682 : : * However, we can't kill it if it's already prepared, so
4683 : : * in that case we commit suicide instead.
4684 : : */
4685 [ - + ]: 152 : if (SxactIsPrepared(nearConflict->sxactOut))
4686 : : {
4687 : 0 : LWLockRelease(SerializableXactHashLock);
4688 [ # # ]: 0 : ereport(ERROR,
4689 : : (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
4690 : : errmsg("could not serialize access due to read/write dependencies among transactions"),
4691 : : errdetail_internal("Reason code: Canceled on commit attempt with conflict in from prepared pivot."),
4692 : : errhint("The transaction might succeed if retried.")));
4693 : : }
4694 : 152 : nearConflict->sxactOut->flags |= SXACT_FLAG_DOOMED;
4695 : 152 : break;
4696 : : }
4697 : : }
4698 : : }
4699 : : }
4700 : :
4701 : 1257 : MySerializableXact->prepareSeqNo = ++(PredXact->LastSxactCommitSeqNo);
4702 : 1257 : MySerializableXact->flags |= SXACT_FLAG_PREPARED;
4703 : :
4704 : 1257 : LWLockRelease(SerializableXactHashLock);
4705 : : }
4706 : :
4707 : : /*------------------------------------------------------------------------*/
4708 : :
4709 : : /*
4710 : : * Two-phase commit support
4711 : : */
4712 : :
4713 : : /*
4714 : : * AtPrepare_Locks
4715 : : * Do the preparatory work for a PREPARE: make 2PC state file
4716 : : * records for all predicate locks currently held.
4717 : : */
4718 : : void
4719 : 317 : AtPrepare_PredicateLocks(void)
4720 : : {
4721 : : SERIALIZABLEXACT *sxact;
4722 : : TwoPhasePredicateRecord record;
4723 : : TwoPhasePredicateXactRecord *xactRecord;
4724 : : TwoPhasePredicateLockRecord *lockRecord;
4725 : : dlist_iter iter;
4726 : :
4727 : 317 : sxact = MySerializableXact;
4728 : 317 : xactRecord = &(record.data.xactRecord);
4729 : 317 : lockRecord = &(record.data.lockRecord);
4730 : :
4731 [ + + ]: 317 : if (MySerializableXact == InvalidSerializableXact)
4732 : 305 : return;
4733 : :
4734 : : /* Generate an xact record for our SERIALIZABLEXACT */
4735 : 12 : record.type = TWOPHASEPREDICATERECORD_XACT;
4736 : 12 : xactRecord->xmin = MySerializableXact->xmin;
4737 : 12 : xactRecord->flags = MySerializableXact->flags;
4738 : :
4739 : : /*
4740 : : * Note that we don't include the list of conflicts in our out in the
4741 : : * statefile, because new conflicts can be added even after the
4742 : : * transaction prepares. We'll just make a conservative assumption during
4743 : : * recovery instead.
4744 : : */
4745 : :
4746 : 12 : RegisterTwoPhaseRecord(TWOPHASE_RM_PREDICATELOCK_ID, 0,
4747 : : &record, sizeof(record));
4748 : :
4749 : : /*
4750 : : * Generate a lock record for each lock.
4751 : : *
4752 : : * To do this, we need to walk the predicate lock list in our sxact rather
4753 : : * than using the local predicate lock table because the latter is not
4754 : : * guaranteed to be accurate.
4755 : : */
4756 : 12 : LWLockAcquire(SerializablePredicateListLock, LW_SHARED);
4757 : :
4758 : : /*
4759 : : * No need to take sxact->perXactPredicateListLock in parallel mode
4760 : : * because there cannot be any parallel workers running while we are
4761 : : * preparing a transaction.
4762 : : */
4763 : : Assert(!IsParallelWorker() && !ParallelContextActive());
4764 : :
4765 [ + - + + ]: 22 : dlist_foreach(iter, &sxact->predicateLocks)
4766 : : {
4767 : 10 : PREDICATELOCK *predlock =
4768 : 10 : dlist_container(PREDICATELOCK, xactLink, iter.cur);
4769 : :
4770 : 10 : record.type = TWOPHASEPREDICATERECORD_LOCK;
4771 : 10 : lockRecord->target = predlock->tag.myTarget->tag;
4772 : :
4773 : 10 : RegisterTwoPhaseRecord(TWOPHASE_RM_PREDICATELOCK_ID, 0,
4774 : : &record, sizeof(record));
4775 : : }
4776 : :
4777 : 12 : LWLockRelease(SerializablePredicateListLock);
4778 : : }
4779 : :
4780 : : /*
4781 : : * PostPrepare_Locks
4782 : : * Clean up after successful PREPARE. Unlike the non-predicate
4783 : : * lock manager, we do not need to transfer locks to a dummy
4784 : : * PGPROC because our SERIALIZABLEXACT will stay around
4785 : : * anyway. We only need to clean up our local state.
4786 : : */
4787 : : void
4788 : 317 : PostPrepare_PredicateLocks(FullTransactionId fxid)
4789 : : {
4790 [ + + ]: 317 : if (MySerializableXact == InvalidSerializableXact)
4791 : 305 : return;
4792 : :
4793 : : Assert(SxactIsPrepared(MySerializableXact));
4794 : :
4795 : 12 : MySerializableXact->pid = 0;
4796 : 12 : MySerializableXact->pgprocno = INVALID_PROC_NUMBER;
4797 : :
4798 : 12 : hash_destroy(LocalPredicateLockHash);
4799 : 12 : LocalPredicateLockHash = NULL;
4800 : :
4801 : 12 : MySerializableXact = InvalidSerializableXact;
4802 : 12 : MyXactDidWrite = false;
4803 : : }
4804 : :
4805 : : /*
4806 : : * PredicateLockTwoPhaseFinish
4807 : : * Release a prepared transaction's predicate locks once it
4808 : : * commits or aborts.
4809 : : */
4810 : : void
4811 : 321 : PredicateLockTwoPhaseFinish(FullTransactionId fxid, bool isCommit)
4812 : : {
4813 : : SERIALIZABLEXID *sxid;
4814 : : SERIALIZABLEXIDTAG sxidtag;
4815 : :
4816 : 321 : sxidtag.xid = XidFromFullTransactionId(fxid);
4817 : :
4818 : 321 : LWLockAcquire(SerializableXactHashLock, LW_SHARED);
4819 : : sxid = (SERIALIZABLEXID *)
4820 : 321 : hash_search(SerializableXidHash, &sxidtag, HASH_FIND, NULL);
4821 : 321 : LWLockRelease(SerializableXactHashLock);
4822 : :
4823 : : /* xid will not be found if it wasn't a serializable transaction */
4824 [ + + ]: 321 : if (sxid == NULL)
4825 : 309 : return;
4826 : :
4827 : : /* Release its locks */
4828 : 12 : MySerializableXact = sxid->myXact;
4829 : 12 : MyXactDidWrite = true; /* conservatively assume that we wrote
4830 : : * something */
4831 : 12 : ReleasePredicateLocks(isCommit, false);
4832 : : }
4833 : :
4834 : : /*
4835 : : * Re-acquire a predicate lock belonging to a transaction that was prepared.
4836 : : */
4837 : : void
4838 : 0 : predicatelock_twophase_recover(FullTransactionId fxid, uint16 info,
4839 : : void *recdata, uint32 len)
4840 : : {
4841 : : TwoPhasePredicateRecord *record;
4842 : 0 : TransactionId xid = XidFromFullTransactionId(fxid);
4843 : :
4844 : : Assert(len == sizeof(TwoPhasePredicateRecord));
4845 : :
4846 : 0 : record = (TwoPhasePredicateRecord *) recdata;
4847 : :
4848 : : Assert((record->type == TWOPHASEPREDICATERECORD_XACT) ||
4849 : : (record->type == TWOPHASEPREDICATERECORD_LOCK));
4850 : :
4851 [ # # ]: 0 : if (record->type == TWOPHASEPREDICATERECORD_XACT)
4852 : : {
4853 : : /* Per-transaction record. Set up a SERIALIZABLEXACT. */
4854 : : TwoPhasePredicateXactRecord *xactRecord;
4855 : : SERIALIZABLEXACT *sxact;
4856 : : SERIALIZABLEXID *sxid;
4857 : : SERIALIZABLEXIDTAG sxidtag;
4858 : : bool found;
4859 : :
4860 : 0 : xactRecord = (TwoPhasePredicateXactRecord *) &record->data.xactRecord;
4861 : :
4862 : 0 : LWLockAcquire(SerializableXactHashLock, LW_EXCLUSIVE);
4863 : 0 : sxact = CreatePredXact();
4864 [ # # ]: 0 : if (!sxact)
4865 [ # # ]: 0 : ereport(ERROR,
4866 : : (errcode(ERRCODE_OUT_OF_MEMORY),
4867 : : errmsg("out of shared memory")));
4868 : :
4869 : : /* vxid for a prepared xact is INVALID_PROC_NUMBER/xid; no pid */
4870 : 0 : sxact->vxid.procNumber = INVALID_PROC_NUMBER;
4871 : 0 : sxact->vxid.localTransactionId = (LocalTransactionId) xid;
4872 : 0 : sxact->pid = 0;
4873 : 0 : sxact->pgprocno = INVALID_PROC_NUMBER;
4874 : :
4875 : : /* a prepared xact hasn't committed yet */
4876 : 0 : sxact->prepareSeqNo = RecoverySerCommitSeqNo;
4877 : 0 : sxact->commitSeqNo = InvalidSerCommitSeqNo;
4878 : 0 : sxact->finishedBefore = InvalidTransactionId;
4879 : :
4880 : 0 : sxact->SeqNo.lastCommitBeforeSnapshot = RecoverySerCommitSeqNo;
4881 : :
4882 : : /*
4883 : : * Don't need to track this; no transactions running at the time the
4884 : : * recovered xact started are still active, except possibly other
4885 : : * prepared xacts and we don't care whether those are RO_SAFE or not.
4886 : : */
4887 : 0 : dlist_init(&(sxact->possibleUnsafeConflicts));
4888 : :
4889 : 0 : dlist_init(&(sxact->predicateLocks));
4890 : 0 : dlist_node_init(&sxact->finishedLink);
4891 : :
4892 : 0 : sxact->topXid = xid;
4893 : 0 : sxact->xmin = xactRecord->xmin;
4894 : 0 : sxact->flags = xactRecord->flags;
4895 : : Assert(SxactIsPrepared(sxact));
4896 [ # # ]: 0 : if (!SxactIsReadOnly(sxact))
4897 : : {
4898 : 0 : ++(PredXact->WritableSxactCount);
4899 : : Assert(PredXact->WritableSxactCount <=
4900 : : (MaxBackends + max_prepared_xacts));
4901 : : }
4902 : :
4903 : : /*
4904 : : * We don't know whether the transaction had any conflicts or not, so
4905 : : * we'll conservatively assume that it had both a conflict in and a
4906 : : * conflict out, and represent that with the summary conflict flags.
4907 : : */
4908 : 0 : dlist_init(&(sxact->outConflicts));
4909 : 0 : dlist_init(&(sxact->inConflicts));
4910 : 0 : sxact->flags |= SXACT_FLAG_SUMMARY_CONFLICT_IN;
4911 : 0 : sxact->flags |= SXACT_FLAG_SUMMARY_CONFLICT_OUT;
4912 : :
4913 : : /* Register the transaction's xid */
4914 : 0 : sxidtag.xid = xid;
4915 : 0 : sxid = (SERIALIZABLEXID *) hash_search(SerializableXidHash,
4916 : : &sxidtag,
4917 : : HASH_ENTER, &found);
4918 : : Assert(sxid != NULL);
4919 : : Assert(!found);
4920 : 0 : sxid->myXact = sxact;
4921 : :
4922 : : /*
4923 : : * Update global xmin. Note that this is a special case compared to
4924 : : * registering a normal transaction, because the global xmin might go
4925 : : * backwards. That's OK, because until recovery is over we're not
4926 : : * going to complete any transactions or create any non-prepared
4927 : : * transactions, so there's no danger of throwing away.
4928 : : */
4929 [ # # # # ]: 0 : if ((!TransactionIdIsValid(PredXact->SxactGlobalXmin)) ||
4930 : 0 : (TransactionIdFollows(PredXact->SxactGlobalXmin, sxact->xmin)))
4931 : : {
4932 : 0 : PredXact->SxactGlobalXmin = sxact->xmin;
4933 : 0 : PredXact->SxactGlobalXminCount = 1;
4934 : 0 : SerialSetActiveSerXmin(sxact->xmin);
4935 : : }
4936 [ # # ]: 0 : else if (TransactionIdEquals(sxact->xmin, PredXact->SxactGlobalXmin))
4937 : : {
4938 : : Assert(PredXact->SxactGlobalXminCount > 0);
4939 : 0 : PredXact->SxactGlobalXminCount++;
4940 : : }
4941 : :
4942 : 0 : LWLockRelease(SerializableXactHashLock);
4943 : : }
4944 [ # # ]: 0 : else if (record->type == TWOPHASEPREDICATERECORD_LOCK)
4945 : : {
4946 : : /* Lock record. Recreate the PREDICATELOCK */
4947 : : TwoPhasePredicateLockRecord *lockRecord;
4948 : : SERIALIZABLEXID *sxid;
4949 : : SERIALIZABLEXACT *sxact;
4950 : : SERIALIZABLEXIDTAG sxidtag;
4951 : : uint32 targettaghash;
4952 : :
4953 : 0 : lockRecord = (TwoPhasePredicateLockRecord *) &record->data.lockRecord;
4954 : 0 : targettaghash = PredicateLockTargetTagHashCode(&lockRecord->target);
4955 : :
4956 : 0 : LWLockAcquire(SerializableXactHashLock, LW_SHARED);
4957 : 0 : sxidtag.xid = xid;
4958 : : sxid = (SERIALIZABLEXID *)
4959 : 0 : hash_search(SerializableXidHash, &sxidtag, HASH_FIND, NULL);
4960 : 0 : LWLockRelease(SerializableXactHashLock);
4961 : :
4962 : : Assert(sxid != NULL);
4963 : 0 : sxact = sxid->myXact;
4964 : : Assert(sxact != InvalidSerializableXact);
4965 : :
4966 : 0 : CreatePredicateLock(&lockRecord->target, targettaghash, sxact);
4967 : : }
4968 : 0 : }
4969 : :
4970 : : /*
4971 : : * Prepare to share the current SERIALIZABLEXACT with parallel workers.
4972 : : * Return a handle object that can be used by AttachSerializableXact() in a
4973 : : * parallel worker.
4974 : : */
4975 : : SerializableXactHandle
4976 : 681 : ShareSerializableXact(void)
4977 : : {
4978 : 681 : return MySerializableXact;
4979 : : }
4980 : :
4981 : : /*
4982 : : * Allow parallel workers to import the leader's SERIALIZABLEXACT.
4983 : : */
4984 : : void
4985 : 2011 : AttachSerializableXact(SerializableXactHandle handle)
4986 : : {
4987 : :
4988 : : Assert(MySerializableXact == InvalidSerializableXact);
4989 : :
4990 : 2011 : MySerializableXact = (SERIALIZABLEXACT *) handle;
4991 [ + + ]: 2011 : if (MySerializableXact != InvalidSerializableXact)
4992 : 13 : CreateLocalPredicateLockHash();
4993 : 2011 : }
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