Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * twophase.c
4 : * Two-phase commit support functions.
5 : *
6 : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : * IDENTIFICATION
10 : * src/backend/access/transam/twophase.c
11 : *
12 : * NOTES
13 : * Each global transaction is associated with a global transaction
14 : * identifier (GID). The client assigns a GID to a postgres
15 : * transaction with the PREPARE TRANSACTION command.
16 : *
17 : * We keep all active global transactions in a shared memory array.
18 : * When the PREPARE TRANSACTION command is issued, the GID is
19 : * reserved for the transaction in the array. This is done before
20 : * a WAL entry is made, because the reservation checks for duplicate
21 : * GIDs and aborts the transaction if there already is a global
22 : * transaction in prepared state with the same GID.
23 : *
24 : * A global transaction (gxact) also has dummy PGPROC; this is what keeps
25 : * the XID considered running by TransactionIdIsInProgress. It is also
26 : * convenient as a PGPROC to hook the gxact's locks to.
27 : *
28 : * Information to recover prepared transactions in case of crash is
29 : * now stored in WAL for the common case. In some cases there will be
30 : * an extended period between preparing a GXACT and commit/abort, in
31 : * which case we need to separately record prepared transaction data
32 : * in permanent storage. This includes locking information, pending
33 : * notifications etc. All that state information is written to the
34 : * per-transaction state file in the pg_twophase directory.
35 : * All prepared transactions will be written prior to shutdown.
36 : *
37 : * Life track of state data is following:
38 : *
39 : * * On PREPARE TRANSACTION backend writes state data only to the WAL and
40 : * stores pointer to the start of the WAL record in
41 : * gxact->prepare_start_lsn.
42 : * * If COMMIT occurs before checkpoint then backend reads data from WAL
43 : * using prepare_start_lsn.
44 : * * On checkpoint state data copied to files in pg_twophase directory and
45 : * fsynced
46 : * * If COMMIT happens after checkpoint then backend reads state data from
47 : * files
48 : *
49 : * During replay and replication, TwoPhaseState also holds information
50 : * about active prepared transactions that haven't been moved to disk yet.
51 : *
52 : * Replay of twophase records happens by the following rules:
53 : *
54 : * * At the beginning of recovery, pg_twophase is scanned once, filling
55 : * TwoPhaseState with entries marked with gxact->inredo and
56 : * gxact->ondisk. Two-phase file data older than the XID horizon of
57 : * the redo position are discarded.
58 : * * On PREPARE redo, the transaction is added to TwoPhaseState->prepXacts.
59 : * gxact->inredo is set to true for such entries.
60 : * * On Checkpoint we iterate through TwoPhaseState->prepXacts entries
61 : * that have gxact->inredo set and are behind the redo_horizon. We
62 : * save them to disk and then switch gxact->ondisk to true.
63 : * * On COMMIT/ABORT we delete the entry from TwoPhaseState->prepXacts.
64 : * If gxact->ondisk is true, the corresponding entry from the disk
65 : * is additionally deleted.
66 : * * RecoverPreparedTransactions(), StandbyRecoverPreparedTransactions()
67 : * and PrescanPreparedTransactions() have been modified to go through
68 : * gxact->inredo entries that have not made it to disk.
69 : *
70 : *-------------------------------------------------------------------------
71 : */
72 : #include "postgres.h"
73 :
74 : #include <fcntl.h>
75 : #include <sys/stat.h>
76 : #include <time.h>
77 : #include <unistd.h>
78 :
79 : #include "access/commit_ts.h"
80 : #include "access/htup_details.h"
81 : #include "access/subtrans.h"
82 : #include "access/transam.h"
83 : #include "access/twophase.h"
84 : #include "access/twophase_rmgr.h"
85 : #include "access/xact.h"
86 : #include "access/xlog.h"
87 : #include "access/xloginsert.h"
88 : #include "access/xlogreader.h"
89 : #include "access/xlogrecovery.h"
90 : #include "access/xlogutils.h"
91 : #include "catalog/pg_type.h"
92 : #include "catalog/storage.h"
93 : #include "funcapi.h"
94 : #include "miscadmin.h"
95 : #include "pg_trace.h"
96 : #include "pgstat.h"
97 : #include "replication/origin.h"
98 : #include "replication/syncrep.h"
99 : #include "storage/fd.h"
100 : #include "storage/ipc.h"
101 : #include "storage/md.h"
102 : #include "storage/predicate.h"
103 : #include "storage/proc.h"
104 : #include "storage/procarray.h"
105 : #include "utils/builtins.h"
106 : #include "utils/injection_point.h"
107 : #include "utils/memutils.h"
108 : #include "utils/timestamp.h"
109 : #include "utils/wait_event.h"
110 :
111 : /*
112 : * Directory where Two-phase commit files reside within PGDATA
113 : */
114 : #define TWOPHASE_DIR "pg_twophase"
115 :
116 : /* GUC variable, can't be changed after startup */
117 : int max_prepared_xacts = 0;
118 :
119 : /*
120 : * This struct describes one global transaction that is in prepared state
121 : * or attempting to become prepared.
122 : *
123 : * The lifecycle of a global transaction is:
124 : *
125 : * 1. After checking that the requested GID is not in use, set up an entry in
126 : * the TwoPhaseState->prepXacts array with the correct GID and valid = false,
127 : * and mark it as locked by my backend.
128 : *
129 : * 2. After successfully completing prepare, set valid = true and enter the
130 : * referenced PGPROC into the global ProcArray.
131 : *
132 : * 3. To begin COMMIT PREPARED or ROLLBACK PREPARED, check that the entry is
133 : * valid and not locked, then mark the entry as locked by storing my current
134 : * proc number into locking_backend. This prevents concurrent attempts to
135 : * commit or rollback the same prepared xact.
136 : *
137 : * 4. On completion of COMMIT PREPARED or ROLLBACK PREPARED, remove the entry
138 : * from the ProcArray and the TwoPhaseState->prepXacts array and return it to
139 : * the freelist.
140 : *
141 : * Note that if the preparing transaction fails between steps 1 and 2, the
142 : * entry must be removed so that the GID and the GlobalTransaction struct
143 : * can be reused. See AtAbort_Twophase().
144 : *
145 : * typedef struct GlobalTransactionData *GlobalTransaction appears in
146 : * twophase.h
147 : */
148 :
149 : typedef struct GlobalTransactionData
150 : {
151 : GlobalTransaction next; /* list link for free list */
152 : int pgprocno; /* ID of associated dummy PGPROC */
153 : TimestampTz prepared_at; /* time of preparation */
154 :
155 : /*
156 : * Note that we need to keep track of two LSNs for each GXACT. We keep
157 : * track of the start LSN because this is the address we must use to read
158 : * state data back from WAL when committing a prepared GXACT. We keep
159 : * track of the end LSN because that is the LSN we need to wait for prior
160 : * to commit.
161 : */
162 : XLogRecPtr prepare_start_lsn; /* XLOG offset of prepare record start */
163 : XLogRecPtr prepare_end_lsn; /* XLOG offset of prepare record end */
164 : FullTransactionId fxid; /* The GXACT full xid */
165 :
166 : Oid owner; /* ID of user that executed the xact */
167 : ProcNumber locking_backend; /* backend currently working on the xact */
168 : bool valid; /* true if PGPROC entry is in proc array */
169 : bool ondisk; /* true if prepare state file is on disk */
170 : bool inredo; /* true if entry was added via xlog_redo */
171 : char gid[GIDSIZE]; /* The GID assigned to the prepared xact */
172 : } GlobalTransactionData;
173 :
174 : /*
175 : * Two Phase Commit shared state. Access to this struct is protected
176 : * by TwoPhaseStateLock.
177 : */
178 : typedef struct TwoPhaseStateData
179 : {
180 : /* Head of linked list of free GlobalTransactionData structs */
181 : GlobalTransaction freeGXacts;
182 :
183 : /* Number of valid prepXacts entries. */
184 : int numPrepXacts;
185 :
186 : /* There are max_prepared_xacts items in this array */
187 : GlobalTransaction prepXacts[FLEXIBLE_ARRAY_MEMBER];
188 : } TwoPhaseStateData;
189 :
190 : static TwoPhaseStateData *TwoPhaseState;
191 :
192 : /*
193 : * Global transaction entry currently locked by us, if any. Note that any
194 : * access to the entry pointed to by this variable must be protected by
195 : * TwoPhaseStateLock, though obviously the pointer itself doesn't need to be
196 : * (since it's just local memory).
197 : */
198 : static GlobalTransaction MyLockedGxact = NULL;
199 :
200 : static bool twophaseExitRegistered = false;
201 :
202 : static void PrepareRedoRemoveFull(FullTransactionId fxid, bool giveWarning);
203 : static void RecordTransactionCommitPrepared(TransactionId xid,
204 : int nchildren,
205 : TransactionId *children,
206 : int nrels,
207 : RelFileLocator *rels,
208 : int nstats,
209 : xl_xact_stats_item *stats,
210 : int ninvalmsgs,
211 : SharedInvalidationMessage *invalmsgs,
212 : bool initfileinval,
213 : const char *gid);
214 : static void RecordTransactionAbortPrepared(TransactionId xid,
215 : int nchildren,
216 : TransactionId *children,
217 : int nrels,
218 : RelFileLocator *rels,
219 : int nstats,
220 : xl_xact_stats_item *stats,
221 : const char *gid);
222 : static void ProcessRecords(char *bufptr, FullTransactionId fxid,
223 : const TwoPhaseCallback callbacks[]);
224 : static void RemoveGXact(GlobalTransaction gxact);
225 :
226 : static void XlogReadTwoPhaseData(XLogRecPtr lsn, char **buf, int *len);
227 : static char *ProcessTwoPhaseBuffer(FullTransactionId fxid,
228 : XLogRecPtr prepare_start_lsn,
229 : bool fromdisk, bool setParent, bool setNextXid);
230 : static void MarkAsPreparingGuts(GlobalTransaction gxact, FullTransactionId fxid,
231 : const char *gid, TimestampTz prepared_at, Oid owner,
232 : Oid databaseid);
233 : static void RemoveTwoPhaseFile(FullTransactionId fxid, bool giveWarning);
234 : static void RecreateTwoPhaseFile(FullTransactionId fxid, void *content, int len);
235 :
236 : /*
237 : * Initialization of shared memory
238 : */
239 : Size
240 3315 : TwoPhaseShmemSize(void)
241 : {
242 : Size size;
243 :
244 : /* Need the fixed struct, the array of pointers, and the GTD structs */
245 3315 : size = offsetof(TwoPhaseStateData, prepXacts);
246 3315 : size = add_size(size, mul_size(max_prepared_xacts,
247 : sizeof(GlobalTransaction)));
248 3315 : size = MAXALIGN(size);
249 3315 : size = add_size(size, mul_size(max_prepared_xacts,
250 : sizeof(GlobalTransactionData)));
251 :
252 3315 : return size;
253 : }
254 :
255 : void
256 1156 : TwoPhaseShmemInit(void)
257 : {
258 : bool found;
259 :
260 1156 : TwoPhaseState = ShmemInitStruct("Prepared Transaction Table",
261 : TwoPhaseShmemSize(),
262 : &found);
263 1156 : if (!IsUnderPostmaster)
264 : {
265 : GlobalTransaction gxacts;
266 : int i;
267 :
268 : Assert(!found);
269 1156 : TwoPhaseState->freeGXacts = NULL;
270 1156 : TwoPhaseState->numPrepXacts = 0;
271 :
272 : /*
273 : * Initialize the linked list of free GlobalTransactionData structs
274 : */
275 1156 : gxacts = (GlobalTransaction)
276 1156 : ((char *) TwoPhaseState +
277 1156 : MAXALIGN(offsetof(TwoPhaseStateData, prepXacts) +
278 : sizeof(GlobalTransaction) * max_prepared_xacts));
279 2024 : for (i = 0; i < max_prepared_xacts; i++)
280 : {
281 : /* insert into linked list */
282 868 : gxacts[i].next = TwoPhaseState->freeGXacts;
283 868 : TwoPhaseState->freeGXacts = &gxacts[i];
284 :
285 : /* associate it with a PGPROC assigned by InitProcGlobal */
286 868 : gxacts[i].pgprocno = GetNumberFromPGProc(&PreparedXactProcs[i]);
287 : }
288 : }
289 : else
290 : Assert(found);
291 1156 : }
292 :
293 : /*
294 : * Exit hook to unlock the global transaction entry we're working on.
295 : */
296 : static void
297 147 : AtProcExit_Twophase(int code, Datum arg)
298 : {
299 : /* same logic as abort */
300 147 : AtAbort_Twophase();
301 147 : }
302 :
303 : /*
304 : * Abort hook to unlock the global transaction entry we're working on.
305 : */
306 : void
307 26760 : AtAbort_Twophase(void)
308 : {
309 26760 : if (MyLockedGxact == NULL)
310 26758 : return;
311 :
312 : /*
313 : * What to do with the locked global transaction entry? If we were in the
314 : * process of preparing the transaction, but haven't written the WAL
315 : * record and state file yet, the transaction must not be considered as
316 : * prepared. Likewise, if we are in the process of finishing an
317 : * already-prepared transaction, and fail after having already written the
318 : * 2nd phase commit or rollback record to the WAL, the transaction should
319 : * not be considered as prepared anymore. In those cases, just remove the
320 : * entry from shared memory.
321 : *
322 : * Otherwise, the entry must be left in place so that the transaction can
323 : * be finished later, so just unlock it.
324 : *
325 : * If we abort during prepare, after having written the WAL record, we
326 : * might not have transferred all locks and other state to the prepared
327 : * transaction yet. Likewise, if we abort during commit or rollback,
328 : * after having written the WAL record, we might not have released all the
329 : * resources held by the transaction yet. In those cases, the in-memory
330 : * state can be wrong, but it's too late to back out.
331 : */
332 2 : LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
333 2 : if (!MyLockedGxact->valid)
334 2 : RemoveGXact(MyLockedGxact);
335 : else
336 0 : MyLockedGxact->locking_backend = INVALID_PROC_NUMBER;
337 2 : LWLockRelease(TwoPhaseStateLock);
338 :
339 2 : MyLockedGxact = NULL;
340 : }
341 :
342 : /*
343 : * This is called after we have finished transferring state to the prepared
344 : * PGPROC entry.
345 : */
346 : void
347 370 : PostPrepare_Twophase(void)
348 : {
349 370 : LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
350 370 : MyLockedGxact->locking_backend = INVALID_PROC_NUMBER;
351 370 : LWLockRelease(TwoPhaseStateLock);
352 :
353 370 : MyLockedGxact = NULL;
354 370 : }
355 :
356 :
357 : /*
358 : * MarkAsPreparing
359 : * Reserve the GID for the given transaction.
360 : */
361 : GlobalTransaction
362 350 : MarkAsPreparing(FullTransactionId fxid, const char *gid,
363 : TimestampTz prepared_at, Oid owner, Oid databaseid)
364 : {
365 : GlobalTransaction gxact;
366 : int i;
367 :
368 350 : if (strlen(gid) >= GIDSIZE)
369 0 : ereport(ERROR,
370 : (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
371 : errmsg("transaction identifier \"%s\" is too long",
372 : gid)));
373 :
374 : /* fail immediately if feature is disabled */
375 350 : if (max_prepared_xacts == 0)
376 9 : ereport(ERROR,
377 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
378 : errmsg("prepared transactions are disabled"),
379 : errhint("Set \"max_prepared_transactions\" to a nonzero value.")));
380 :
381 : /* on first call, register the exit hook */
382 341 : if (!twophaseExitRegistered)
383 : {
384 83 : before_shmem_exit(AtProcExit_Twophase, 0);
385 83 : twophaseExitRegistered = true;
386 : }
387 :
388 341 : LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
389 :
390 : /* Check for conflicting GID */
391 609 : for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
392 : {
393 270 : gxact = TwoPhaseState->prepXacts[i];
394 270 : if (strcmp(gxact->gid, gid) == 0)
395 : {
396 2 : ereport(ERROR,
397 : (errcode(ERRCODE_DUPLICATE_OBJECT),
398 : errmsg("transaction identifier \"%s\" is already in use",
399 : gid)));
400 : }
401 : }
402 :
403 : /* Get a free gxact from the freelist */
404 339 : if (TwoPhaseState->freeGXacts == NULL)
405 0 : ereport(ERROR,
406 : (errcode(ERRCODE_OUT_OF_MEMORY),
407 : errmsg("maximum number of prepared transactions reached"),
408 : errhint("Increase \"max_prepared_transactions\" (currently %d).",
409 : max_prepared_xacts)));
410 339 : gxact = TwoPhaseState->freeGXacts;
411 339 : TwoPhaseState->freeGXacts = gxact->next;
412 :
413 339 : MarkAsPreparingGuts(gxact, fxid, gid, prepared_at, owner, databaseid);
414 :
415 339 : gxact->ondisk = false;
416 :
417 : /* And insert it into the active array */
418 : Assert(TwoPhaseState->numPrepXacts < max_prepared_xacts);
419 339 : TwoPhaseState->prepXacts[TwoPhaseState->numPrepXacts++] = gxact;
420 :
421 339 : LWLockRelease(TwoPhaseStateLock);
422 :
423 339 : return gxact;
424 : }
425 :
426 : /*
427 : * MarkAsPreparingGuts
428 : *
429 : * This uses a gxact struct and puts it into the active array.
430 : * NOTE: this is also used when reloading a gxact after a crash; so avoid
431 : * assuming that we can use very much backend context.
432 : *
433 : * Note: This function should be called with appropriate locks held.
434 : */
435 : static void
436 372 : MarkAsPreparingGuts(GlobalTransaction gxact, FullTransactionId fxid,
437 : const char *gid, TimestampTz prepared_at, Oid owner,
438 : Oid databaseid)
439 : {
440 : PGPROC *proc;
441 : int i;
442 372 : TransactionId xid = XidFromFullTransactionId(fxid);
443 :
444 : Assert(LWLockHeldByMeInMode(TwoPhaseStateLock, LW_EXCLUSIVE));
445 :
446 : Assert(gxact != NULL);
447 372 : proc = GetPGProcByNumber(gxact->pgprocno);
448 :
449 : /* Initialize the PGPROC entry */
450 42036 : MemSet(proc, 0, sizeof(PGPROC));
451 372 : proc->waitStatus = PROC_WAIT_STATUS_OK;
452 372 : if (LocalTransactionIdIsValid(MyProc->vxid.lxid))
453 : {
454 : /* clone VXID, for TwoPhaseGetXidByVirtualXID() to find */
455 339 : proc->vxid.lxid = MyProc->vxid.lxid;
456 339 : proc->vxid.procNumber = MyProcNumber;
457 : }
458 : else
459 : {
460 : Assert(AmStartupProcess() || !IsPostmasterEnvironment);
461 : /* GetLockConflicts() uses this to specify a wait on the XID */
462 33 : proc->vxid.lxid = xid;
463 33 : proc->vxid.procNumber = INVALID_PROC_NUMBER;
464 : }
465 372 : proc->xid = xid;
466 : Assert(proc->xmin == InvalidTransactionId);
467 372 : proc->delayChkptFlags = 0;
468 372 : proc->statusFlags = 0;
469 372 : proc->pid = 0;
470 372 : proc->databaseId = databaseid;
471 372 : proc->roleId = owner;
472 372 : proc->tempNamespaceId = InvalidOid;
473 372 : proc->backendType = B_INVALID;
474 372 : proc->lwWaiting = LW_WS_NOT_WAITING;
475 372 : proc->lwWaitMode = 0;
476 372 : proc->waitLock = NULL;
477 372 : dlist_node_init(&proc->waitLink);
478 372 : proc->waitProcLock = NULL;
479 372 : pg_atomic_init_u64(&proc->waitStart, 0);
480 6324 : for (i = 0; i < NUM_LOCK_PARTITIONS; i++)
481 5952 : dlist_init(&proc->myProcLocks[i]);
482 : /* subxid data must be filled later by GXactLoadSubxactData */
483 372 : proc->subxidStatus.overflowed = false;
484 372 : proc->subxidStatus.count = 0;
485 :
486 372 : gxact->prepared_at = prepared_at;
487 372 : gxact->fxid = fxid;
488 372 : gxact->owner = owner;
489 372 : gxact->locking_backend = MyProcNumber;
490 372 : gxact->valid = false;
491 372 : gxact->inredo = false;
492 372 : strcpy(gxact->gid, gid);
493 :
494 : /*
495 : * Remember that we have this GlobalTransaction entry locked for us. If we
496 : * abort after this, we must release it.
497 : */
498 372 : MyLockedGxact = gxact;
499 372 : }
500 :
501 : /*
502 : * GXactLoadSubxactData
503 : *
504 : * If the transaction being persisted had any subtransactions, this must
505 : * be called before MarkAsPrepared() to load information into the dummy
506 : * PGPROC.
507 : */
508 : static void
509 159 : GXactLoadSubxactData(GlobalTransaction gxact, int nsubxacts,
510 : TransactionId *children)
511 : {
512 159 : PGPROC *proc = GetPGProcByNumber(gxact->pgprocno);
513 :
514 : /* We need no extra lock since the GXACT isn't valid yet */
515 159 : if (nsubxacts > PGPROC_MAX_CACHED_SUBXIDS)
516 : {
517 4 : proc->subxidStatus.overflowed = true;
518 4 : nsubxacts = PGPROC_MAX_CACHED_SUBXIDS;
519 : }
520 159 : if (nsubxacts > 0)
521 : {
522 142 : memcpy(proc->subxids.xids, children,
523 : nsubxacts * sizeof(TransactionId));
524 142 : proc->subxidStatus.count = nsubxacts;
525 : }
526 159 : }
527 :
528 : /*
529 : * MarkAsPrepared
530 : * Mark the GXACT as fully valid, and enter it into the global ProcArray.
531 : *
532 : * lock_held indicates whether caller already holds TwoPhaseStateLock.
533 : */
534 : static void
535 370 : MarkAsPrepared(GlobalTransaction gxact, bool lock_held)
536 : {
537 : /* Lock here may be overkill, but I'm not convinced of that ... */
538 370 : if (!lock_held)
539 337 : LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
540 : Assert(!gxact->valid);
541 370 : gxact->valid = true;
542 370 : if (!lock_held)
543 337 : LWLockRelease(TwoPhaseStateLock);
544 :
545 : /*
546 : * Put it into the global ProcArray so TransactionIdIsInProgress considers
547 : * the XID as still running.
548 : */
549 370 : ProcArrayAdd(GetPGProcByNumber(gxact->pgprocno));
550 370 : }
551 :
552 : /*
553 : * LockGXact
554 : * Locate the prepared transaction and mark it busy for COMMIT or PREPARE.
555 : */
556 : static GlobalTransaction
557 350 : LockGXact(const char *gid, Oid user)
558 : {
559 : int i;
560 :
561 : /* on first call, register the exit hook */
562 350 : if (!twophaseExitRegistered)
563 : {
564 64 : before_shmem_exit(AtProcExit_Twophase, 0);
565 64 : twophaseExitRegistered = true;
566 : }
567 :
568 350 : LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
569 :
570 579 : for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
571 : {
572 572 : GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
573 572 : PGPROC *proc = GetPGProcByNumber(gxact->pgprocno);
574 :
575 : /* Ignore not-yet-valid GIDs */
576 572 : if (!gxact->valid)
577 0 : continue;
578 572 : if (strcmp(gxact->gid, gid) != 0)
579 229 : continue;
580 :
581 : /* Found it, but has someone else got it locked? */
582 343 : if (gxact->locking_backend != INVALID_PROC_NUMBER)
583 0 : ereport(ERROR,
584 : (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
585 : errmsg("prepared transaction with identifier \"%s\" is busy",
586 : gid)));
587 :
588 343 : if (user != gxact->owner && !superuser_arg(user))
589 0 : ereport(ERROR,
590 : (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
591 : errmsg("permission denied to finish prepared transaction"),
592 : errhint("Must be superuser or the user that prepared the transaction.")));
593 :
594 : /*
595 : * Note: it probably would be possible to allow committing from
596 : * another database; but at the moment NOTIFY is known not to work and
597 : * there may be some other issues as well. Hence disallow until
598 : * someone gets motivated to make it work.
599 : */
600 343 : if (MyDatabaseId != proc->databaseId)
601 0 : ereport(ERROR,
602 : (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
603 : errmsg("prepared transaction belongs to another database"),
604 : errhint("Connect to the database where the transaction was prepared to finish it.")));
605 :
606 : /* OK for me to lock it */
607 343 : gxact->locking_backend = MyProcNumber;
608 343 : MyLockedGxact = gxact;
609 :
610 343 : LWLockRelease(TwoPhaseStateLock);
611 :
612 343 : return gxact;
613 : }
614 :
615 7 : LWLockRelease(TwoPhaseStateLock);
616 :
617 7 : ereport(ERROR,
618 : (errcode(ERRCODE_UNDEFINED_OBJECT),
619 : errmsg("prepared transaction with identifier \"%s\" does not exist",
620 : gid)));
621 :
622 : /* NOTREACHED */
623 : return NULL;
624 : }
625 :
626 : /*
627 : * RemoveGXact
628 : * Remove the prepared transaction from the shared memory array.
629 : *
630 : * NB: caller should have already removed it from ProcArray
631 : */
632 : static void
633 407 : RemoveGXact(GlobalTransaction gxact)
634 : {
635 : int i;
636 :
637 : Assert(LWLockHeldByMeInMode(TwoPhaseStateLock, LW_EXCLUSIVE));
638 :
639 633 : for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
640 : {
641 633 : if (gxact == TwoPhaseState->prepXacts[i])
642 : {
643 : /* remove from the active array */
644 407 : TwoPhaseState->numPrepXacts--;
645 407 : TwoPhaseState->prepXacts[i] = TwoPhaseState->prepXacts[TwoPhaseState->numPrepXacts];
646 :
647 : /* and put it back in the freelist */
648 407 : gxact->next = TwoPhaseState->freeGXacts;
649 407 : TwoPhaseState->freeGXacts = gxact;
650 :
651 407 : return;
652 : }
653 : }
654 :
655 0 : elog(ERROR, "failed to find %p in GlobalTransaction array", gxact);
656 : }
657 :
658 : /*
659 : * Returns an array of all prepared transactions for the user-level
660 : * function pg_prepared_xact.
661 : *
662 : * The returned array and all its elements are copies of internal data
663 : * structures, to minimize the time we need to hold the TwoPhaseStateLock.
664 : *
665 : * WARNING -- we return even those transactions that are not fully prepared
666 : * yet. The caller should filter them out if he doesn't want them.
667 : *
668 : * The returned array is palloc'd.
669 : */
670 : static int
671 107 : GetPreparedTransactionList(GlobalTransaction *gxacts)
672 : {
673 : GlobalTransaction array;
674 : int num;
675 : int i;
676 :
677 107 : LWLockAcquire(TwoPhaseStateLock, LW_SHARED);
678 :
679 107 : if (TwoPhaseState->numPrepXacts == 0)
680 : {
681 66 : LWLockRelease(TwoPhaseStateLock);
682 :
683 66 : *gxacts = NULL;
684 66 : return 0;
685 : }
686 :
687 41 : num = TwoPhaseState->numPrepXacts;
688 41 : array = palloc_array(GlobalTransactionData, num);
689 41 : *gxacts = array;
690 87 : for (i = 0; i < num; i++)
691 46 : memcpy(array + i, TwoPhaseState->prepXacts[i],
692 : sizeof(GlobalTransactionData));
693 :
694 41 : LWLockRelease(TwoPhaseStateLock);
695 :
696 41 : return num;
697 : }
698 :
699 :
700 : /* Working status for pg_prepared_xact */
701 : typedef struct
702 : {
703 : GlobalTransaction array;
704 : int ngxacts;
705 : int currIdx;
706 : } Working_State;
707 :
708 : /*
709 : * pg_prepared_xact
710 : * Produce a view with one row per prepared transaction.
711 : *
712 : * This function is here so we don't have to export the
713 : * GlobalTransactionData struct definition.
714 : */
715 : Datum
716 153 : pg_prepared_xact(PG_FUNCTION_ARGS)
717 : {
718 : FuncCallContext *funcctx;
719 : Working_State *status;
720 :
721 153 : if (SRF_IS_FIRSTCALL())
722 : {
723 : TupleDesc tupdesc;
724 : MemoryContext oldcontext;
725 :
726 : /* create a function context for cross-call persistence */
727 107 : funcctx = SRF_FIRSTCALL_INIT();
728 :
729 : /*
730 : * Switch to memory context appropriate for multiple function calls
731 : */
732 107 : oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
733 :
734 : /* build tupdesc for result tuples */
735 : /* this had better match pg_prepared_xacts view in system_views.sql */
736 107 : tupdesc = CreateTemplateTupleDesc(5);
737 107 : TupleDescInitEntry(tupdesc, (AttrNumber) 1, "transaction",
738 : XIDOID, -1, 0);
739 107 : TupleDescInitEntry(tupdesc, (AttrNumber) 2, "gid",
740 : TEXTOID, -1, 0);
741 107 : TupleDescInitEntry(tupdesc, (AttrNumber) 3, "prepared",
742 : TIMESTAMPTZOID, -1, 0);
743 107 : TupleDescInitEntry(tupdesc, (AttrNumber) 4, "ownerid",
744 : OIDOID, -1, 0);
745 107 : TupleDescInitEntry(tupdesc, (AttrNumber) 5, "dbid",
746 : OIDOID, -1, 0);
747 :
748 107 : funcctx->tuple_desc = BlessTupleDesc(tupdesc);
749 :
750 : /*
751 : * Collect all the 2PC status information that we will format and send
752 : * out as a result set.
753 : */
754 107 : status = palloc_object(Working_State);
755 107 : funcctx->user_fctx = status;
756 :
757 107 : status->ngxacts = GetPreparedTransactionList(&status->array);
758 107 : status->currIdx = 0;
759 :
760 107 : MemoryContextSwitchTo(oldcontext);
761 : }
762 :
763 153 : funcctx = SRF_PERCALL_SETUP();
764 153 : status = (Working_State *) funcctx->user_fctx;
765 :
766 153 : while (status->array != NULL && status->currIdx < status->ngxacts)
767 : {
768 46 : GlobalTransaction gxact = &status->array[status->currIdx++];
769 46 : PGPROC *proc = GetPGProcByNumber(gxact->pgprocno);
770 46 : Datum values[5] = {0};
771 46 : bool nulls[5] = {0};
772 : HeapTuple tuple;
773 : Datum result;
774 :
775 46 : if (!gxact->valid)
776 0 : continue;
777 :
778 : /*
779 : * Form tuple with appropriate data.
780 : */
781 :
782 46 : values[0] = TransactionIdGetDatum(proc->xid);
783 46 : values[1] = CStringGetTextDatum(gxact->gid);
784 46 : values[2] = TimestampTzGetDatum(gxact->prepared_at);
785 46 : values[3] = ObjectIdGetDatum(gxact->owner);
786 46 : values[4] = ObjectIdGetDatum(proc->databaseId);
787 :
788 46 : tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls);
789 46 : result = HeapTupleGetDatum(tuple);
790 46 : SRF_RETURN_NEXT(funcctx, result);
791 : }
792 :
793 107 : SRF_RETURN_DONE(funcctx);
794 : }
795 :
796 : /*
797 : * TwoPhaseGetGXact
798 : * Get the GlobalTransaction struct for a prepared transaction
799 : * specified by XID
800 : *
801 : * If lock_held is set to true, TwoPhaseStateLock will not be taken, so the
802 : * caller had better hold it.
803 : */
804 : static GlobalTransaction
805 1467 : TwoPhaseGetGXact(FullTransactionId fxid, bool lock_held)
806 : {
807 1467 : GlobalTransaction result = NULL;
808 : int i;
809 :
810 : static FullTransactionId cached_fxid = {InvalidTransactionId};
811 : static GlobalTransaction cached_gxact = NULL;
812 :
813 : Assert(!lock_held || LWLockHeldByMe(TwoPhaseStateLock));
814 :
815 : /*
816 : * During a recovery, COMMIT PREPARED, or ABORT PREPARED, we'll be called
817 : * repeatedly for the same XID. We can save work with a simple cache.
818 : */
819 1467 : if (FullTransactionIdEquals(fxid, cached_fxid))
820 1019 : return cached_gxact;
821 :
822 448 : if (!lock_held)
823 370 : LWLockAcquire(TwoPhaseStateLock, LW_SHARED);
824 :
825 720 : for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
826 : {
827 720 : GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
828 :
829 720 : if (FullTransactionIdEquals(gxact->fxid, fxid))
830 : {
831 448 : result = gxact;
832 448 : break;
833 : }
834 : }
835 :
836 448 : if (!lock_held)
837 370 : LWLockRelease(TwoPhaseStateLock);
838 :
839 448 : if (result == NULL) /* should not happen */
840 0 : elog(ERROR, "failed to find GlobalTransaction for xid %u",
841 : XidFromFullTransactionId(fxid));
842 :
843 448 : cached_fxid = fxid;
844 448 : cached_gxact = result;
845 :
846 448 : return result;
847 : }
848 :
849 : /*
850 : * TwoPhaseGetXidByVirtualXID
851 : * Lookup VXID among xacts prepared since last startup.
852 : *
853 : * (This won't find recovered xacts.) If more than one matches, return any
854 : * and set "have_more" to true. To witness multiple matches, a single
855 : * proc number must consume 2^32 LXIDs, with no intervening database restart.
856 : */
857 : TransactionId
858 100 : TwoPhaseGetXidByVirtualXID(VirtualTransactionId vxid,
859 : bool *have_more)
860 : {
861 : int i;
862 100 : TransactionId result = InvalidTransactionId;
863 :
864 : Assert(VirtualTransactionIdIsValid(vxid));
865 100 : LWLockAcquire(TwoPhaseStateLock, LW_SHARED);
866 :
867 178 : for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
868 : {
869 78 : GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
870 : PGPROC *proc;
871 : VirtualTransactionId proc_vxid;
872 :
873 78 : if (!gxact->valid)
874 0 : continue;
875 78 : proc = GetPGProcByNumber(gxact->pgprocno);
876 78 : GET_VXID_FROM_PGPROC(proc_vxid, *proc);
877 78 : if (VirtualTransactionIdEquals(vxid, proc_vxid))
878 : {
879 : /*
880 : * Startup process sets proc->vxid.procNumber to
881 : * INVALID_PROC_NUMBER.
882 : */
883 : Assert(!gxact->inredo);
884 :
885 21 : if (result != InvalidTransactionId)
886 : {
887 0 : *have_more = true;
888 0 : break;
889 : }
890 21 : result = XidFromFullTransactionId(gxact->fxid);
891 : }
892 : }
893 :
894 100 : LWLockRelease(TwoPhaseStateLock);
895 :
896 100 : return result;
897 : }
898 :
899 : /*
900 : * TwoPhaseGetDummyProcNumber
901 : * Get the dummy proc number for prepared transaction
902 : *
903 : * Dummy proc numbers are similar to proc numbers of real backends. They
904 : * start at FIRST_PREPARED_XACT_PROC_NUMBER, and are unique across all
905 : * currently active real backends and prepared transactions. If lock_held is
906 : * set to true, TwoPhaseStateLock will not be taken, so the caller had better
907 : * hold it.
908 : */
909 : ProcNumber
910 148 : TwoPhaseGetDummyProcNumber(FullTransactionId fxid, bool lock_held)
911 : {
912 148 : GlobalTransaction gxact = TwoPhaseGetGXact(fxid, lock_held);
913 :
914 148 : return gxact->pgprocno;
915 : }
916 :
917 : /*
918 : * TwoPhaseGetDummyProc
919 : * Get the PGPROC that represents a prepared transaction
920 : *
921 : * If lock_held is set to true, TwoPhaseStateLock will not be taken, so the
922 : * caller had better hold it.
923 : */
924 : PGPROC *
925 1319 : TwoPhaseGetDummyProc(FullTransactionId fxid, bool lock_held)
926 : {
927 1319 : GlobalTransaction gxact = TwoPhaseGetGXact(fxid, lock_held);
928 :
929 1319 : return GetPGProcByNumber(gxact->pgprocno);
930 : }
931 :
932 : /************************************************************************/
933 : /* State file support */
934 : /************************************************************************/
935 :
936 : /*
937 : * Compute the FullTransactionId for the given TransactionId.
938 : *
939 : * This is safe if the xid has not yet reached COMMIT PREPARED or ROLLBACK
940 : * PREPARED. After those commands, concurrent vac_truncate_clog() may make
941 : * the xid cease to qualify as allowable. XXX Not all callers limit their
942 : * calls accordingly.
943 : */
944 : static inline FullTransactionId
945 287 : AdjustToFullTransactionId(TransactionId xid)
946 : {
947 : Assert(TransactionIdIsValid(xid));
948 287 : return FullTransactionIdFromAllowableAt(ReadNextFullTransactionId(), xid);
949 : }
950 :
951 : static inline int
952 503 : TwoPhaseFilePath(char *path, FullTransactionId fxid)
953 : {
954 1006 : return snprintf(path, MAXPGPATH, TWOPHASE_DIR "/%08X%08X",
955 503 : EpochFromFullTransactionId(fxid),
956 503 : XidFromFullTransactionId(fxid));
957 : }
958 :
959 : /*
960 : * 2PC state file format:
961 : *
962 : * 1. TwoPhaseFileHeader
963 : * 2. TransactionId[] (subtransactions)
964 : * 3. RelFileLocator[] (files to be deleted at commit)
965 : * 4. RelFileLocator[] (files to be deleted at abort)
966 : * 5. SharedInvalidationMessage[] (inval messages to be sent at commit)
967 : * 6. TwoPhaseRecordOnDisk
968 : * 7. ...
969 : * 8. TwoPhaseRecordOnDisk (end sentinel, rmid == TWOPHASE_RM_END_ID)
970 : * 9. checksum (CRC-32C)
971 : *
972 : * Each segment except the final checksum is MAXALIGN'd.
973 : */
974 :
975 : /*
976 : * Header for a 2PC state file
977 : */
978 : #define TWOPHASE_MAGIC 0x57F94534 /* format identifier */
979 :
980 : typedef xl_xact_prepare TwoPhaseFileHeader;
981 :
982 : /*
983 : * Header for each record in a state file
984 : *
985 : * NOTE: len counts only the rmgr data, not the TwoPhaseRecordOnDisk header.
986 : * The rmgr data will be stored starting on a MAXALIGN boundary.
987 : */
988 : typedef struct TwoPhaseRecordOnDisk
989 : {
990 : uint32 len; /* length of rmgr data */
991 : TwoPhaseRmgrId rmid; /* resource manager for this record */
992 : uint16 info; /* flag bits for use by rmgr */
993 : } TwoPhaseRecordOnDisk;
994 :
995 : /*
996 : * During prepare, the state file is assembled in memory before writing it
997 : * to WAL and the actual state file. We use a chain of StateFileChunk blocks
998 : * for that.
999 : */
1000 : typedef struct StateFileChunk
1001 : {
1002 : char *data;
1003 : uint32 len;
1004 : struct StateFileChunk *next;
1005 : } StateFileChunk;
1006 :
1007 : static struct xllist
1008 : {
1009 : StateFileChunk *head; /* first data block in the chain */
1010 : StateFileChunk *tail; /* last block in chain */
1011 : uint32 num_chunks;
1012 : uint32 bytes_free; /* free bytes left in tail block */
1013 : uint32 total_len; /* total data bytes in chain */
1014 : } records;
1015 :
1016 :
1017 : /*
1018 : * Append a block of data to records data structure.
1019 : *
1020 : * NB: each block is padded to a MAXALIGN multiple. This must be
1021 : * accounted for when the file is later read!
1022 : *
1023 : * The data is copied, so the caller is free to modify it afterwards.
1024 : */
1025 : static void
1026 4106 : save_state_data(const void *data, uint32 len)
1027 : {
1028 4106 : uint32 padlen = MAXALIGN(len);
1029 :
1030 4106 : if (padlen > records.bytes_free)
1031 : {
1032 79 : records.tail->next = palloc0_object(StateFileChunk);
1033 79 : records.tail = records.tail->next;
1034 79 : records.tail->len = 0;
1035 79 : records.tail->next = NULL;
1036 79 : records.num_chunks++;
1037 :
1038 79 : records.bytes_free = Max(padlen, 512);
1039 79 : records.tail->data = palloc(records.bytes_free);
1040 : }
1041 :
1042 4106 : memcpy(records.tail->data + records.tail->len, data, len);
1043 4106 : records.tail->len += padlen;
1044 4106 : records.bytes_free -= padlen;
1045 4106 : records.total_len += padlen;
1046 4106 : }
1047 :
1048 : /*
1049 : * Start preparing a state file.
1050 : *
1051 : * Initializes data structure and inserts the 2PC file header record.
1052 : */
1053 : void
1054 339 : StartPrepare(GlobalTransaction gxact)
1055 : {
1056 339 : PGPROC *proc = GetPGProcByNumber(gxact->pgprocno);
1057 339 : TransactionId xid = XidFromFullTransactionId(gxact->fxid);
1058 : TwoPhaseFileHeader hdr;
1059 : TransactionId *children;
1060 : RelFileLocator *commitrels;
1061 : RelFileLocator *abortrels;
1062 339 : xl_xact_stats_item *abortstats = NULL;
1063 339 : xl_xact_stats_item *commitstats = NULL;
1064 : SharedInvalidationMessage *invalmsgs;
1065 :
1066 : /* Initialize linked list */
1067 339 : records.head = palloc0_object(StateFileChunk);
1068 339 : records.head->len = 0;
1069 339 : records.head->next = NULL;
1070 :
1071 339 : records.bytes_free = Max(sizeof(TwoPhaseFileHeader), 512);
1072 339 : records.head->data = palloc(records.bytes_free);
1073 :
1074 339 : records.tail = records.head;
1075 339 : records.num_chunks = 1;
1076 :
1077 339 : records.total_len = 0;
1078 :
1079 : /* Create header */
1080 339 : hdr.magic = TWOPHASE_MAGIC;
1081 339 : hdr.total_len = 0; /* EndPrepare will fill this in */
1082 339 : hdr.xid = xid;
1083 339 : hdr.database = proc->databaseId;
1084 339 : hdr.prepared_at = gxact->prepared_at;
1085 339 : hdr.owner = gxact->owner;
1086 339 : hdr.nsubxacts = xactGetCommittedChildren(&children);
1087 339 : hdr.ncommitrels = smgrGetPendingDeletes(true, &commitrels);
1088 339 : hdr.nabortrels = smgrGetPendingDeletes(false, &abortrels);
1089 339 : hdr.ncommitstats =
1090 339 : pgstat_get_transactional_drops(true, &commitstats);
1091 339 : hdr.nabortstats =
1092 339 : pgstat_get_transactional_drops(false, &abortstats);
1093 339 : hdr.ninvalmsgs = xactGetCommittedInvalidationMessages(&invalmsgs,
1094 : &hdr.initfileinval);
1095 339 : hdr.gidlen = strlen(gxact->gid) + 1; /* Include '\0' */
1096 : /* EndPrepare will fill the origin data, if necessary */
1097 339 : hdr.origin_lsn = InvalidXLogRecPtr;
1098 339 : hdr.origin_timestamp = 0;
1099 :
1100 339 : save_state_data(&hdr, sizeof(TwoPhaseFileHeader));
1101 339 : save_state_data(gxact->gid, hdr.gidlen);
1102 :
1103 : /*
1104 : * Add the additional info about subxacts, deletable files and cache
1105 : * invalidation messages.
1106 : */
1107 339 : if (hdr.nsubxacts > 0)
1108 : {
1109 126 : save_state_data(children, hdr.nsubxacts * sizeof(TransactionId));
1110 : /* While we have the child-xact data, stuff it in the gxact too */
1111 126 : GXactLoadSubxactData(gxact, hdr.nsubxacts, children);
1112 : }
1113 339 : if (hdr.ncommitrels > 0)
1114 : {
1115 21 : save_state_data(commitrels, hdr.ncommitrels * sizeof(RelFileLocator));
1116 21 : pfree(commitrels);
1117 : }
1118 339 : if (hdr.nabortrels > 0)
1119 : {
1120 29 : save_state_data(abortrels, hdr.nabortrels * sizeof(RelFileLocator));
1121 29 : pfree(abortrels);
1122 : }
1123 339 : if (hdr.ncommitstats > 0)
1124 : {
1125 21 : save_state_data(commitstats,
1126 21 : hdr.ncommitstats * sizeof(xl_xact_stats_item));
1127 21 : pfree(commitstats);
1128 : }
1129 339 : if (hdr.nabortstats > 0)
1130 : {
1131 25 : save_state_data(abortstats,
1132 25 : hdr.nabortstats * sizeof(xl_xact_stats_item));
1133 25 : pfree(abortstats);
1134 : }
1135 339 : if (hdr.ninvalmsgs > 0)
1136 : {
1137 37 : save_state_data(invalmsgs,
1138 37 : hdr.ninvalmsgs * sizeof(SharedInvalidationMessage));
1139 37 : pfree(invalmsgs);
1140 : }
1141 339 : }
1142 :
1143 : /*
1144 : * Finish preparing state data and writing it to WAL.
1145 : */
1146 : void
1147 337 : EndPrepare(GlobalTransaction gxact)
1148 : {
1149 : TwoPhaseFileHeader *hdr;
1150 : StateFileChunk *record;
1151 : bool replorigin;
1152 :
1153 : /* Add the end sentinel to the list of 2PC records */
1154 337 : RegisterTwoPhaseRecord(TWOPHASE_RM_END_ID, 0,
1155 : NULL, 0);
1156 :
1157 : /* Go back and fill in total_len in the file header record */
1158 337 : hdr = (TwoPhaseFileHeader *) records.head->data;
1159 : Assert(hdr->magic == TWOPHASE_MAGIC);
1160 337 : hdr->total_len = records.total_len + sizeof(pg_crc32c);
1161 :
1162 363 : replorigin = (replorigin_xact_state.origin != InvalidReplOriginId &&
1163 26 : replorigin_xact_state.origin != DoNotReplicateId);
1164 :
1165 337 : if (replorigin)
1166 : {
1167 26 : hdr->origin_lsn = replorigin_xact_state.origin_lsn;
1168 26 : hdr->origin_timestamp = replorigin_xact_state.origin_timestamp;
1169 : }
1170 :
1171 : /*
1172 : * If the data size exceeds MaxAllocSize, we won't be able to read it in
1173 : * ReadTwoPhaseFile. Check for that now, rather than fail in the case
1174 : * where we write data to file and then re-read at commit time.
1175 : */
1176 337 : if (hdr->total_len > MaxAllocSize)
1177 0 : ereport(ERROR,
1178 : (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
1179 : errmsg("two-phase state file maximum length exceeded")));
1180 :
1181 : /*
1182 : * Now writing 2PC state data to WAL. We let the WAL's CRC protection
1183 : * cover us, so no need to calculate a separate CRC.
1184 : *
1185 : * We have to set DELAY_CHKPT_START here, too; otherwise a checkpoint
1186 : * starting immediately after the WAL record is inserted could complete
1187 : * without fsync'ing our state file. (This is essentially the same kind
1188 : * of race condition as the COMMIT-to-clog-write case that
1189 : * RecordTransactionCommit uses DELAY_CHKPT_IN_COMMIT for; see notes
1190 : * there.) Note that DELAY_CHKPT_IN_COMMIT is used to find transactions in
1191 : * the critical commit section. We need to know about such transactions
1192 : * for conflict detection in logical replication. See
1193 : * GetOldestActiveTransactionId(true, false) and its use.
1194 : *
1195 : * We save the PREPARE record's location in the gxact for later use by
1196 : * CheckPointTwoPhase.
1197 : */
1198 337 : XLogEnsureRecordSpace(0, records.num_chunks);
1199 :
1200 337 : START_CRIT_SECTION();
1201 :
1202 : Assert((MyProc->delayChkptFlags & DELAY_CHKPT_START) == 0);
1203 337 : MyProc->delayChkptFlags |= DELAY_CHKPT_START;
1204 :
1205 337 : XLogBeginInsert();
1206 753 : for (record = records.head; record != NULL; record = record->next)
1207 416 : XLogRegisterData(record->data, record->len);
1208 :
1209 337 : XLogSetRecordFlags(XLOG_INCLUDE_ORIGIN);
1210 :
1211 337 : gxact->prepare_end_lsn = XLogInsert(RM_XACT_ID, XLOG_XACT_PREPARE);
1212 :
1213 337 : if (replorigin)
1214 : {
1215 : /* Move LSNs forward for this replication origin */
1216 26 : replorigin_session_advance(replorigin_xact_state.origin_lsn,
1217 : gxact->prepare_end_lsn);
1218 : }
1219 :
1220 337 : XLogFlush(gxact->prepare_end_lsn);
1221 :
1222 : /* If we crash now, we have prepared: WAL replay will fix things */
1223 :
1224 : /* Store record's start location to read that later on Commit */
1225 337 : gxact->prepare_start_lsn = ProcLastRecPtr;
1226 :
1227 : /*
1228 : * Mark the prepared transaction as valid. As soon as xact.c marks MyProc
1229 : * as not running our XID (which it will do immediately after this
1230 : * function returns), others can commit/rollback the xact.
1231 : *
1232 : * NB: a side effect of this is to make a dummy ProcArray entry for the
1233 : * prepared XID. This must happen before we clear the XID from MyProc /
1234 : * ProcGlobal->xids[], else there is a window where the XID is not running
1235 : * according to TransactionIdIsInProgress, and onlookers would be entitled
1236 : * to assume the xact crashed. Instead we have a window where the same
1237 : * XID appears twice in ProcArray, which is OK.
1238 : */
1239 337 : MarkAsPrepared(gxact, false);
1240 :
1241 : /*
1242 : * Now we can mark ourselves as out of the commit critical section: a
1243 : * checkpoint starting after this will certainly see the gxact as a
1244 : * candidate for fsyncing.
1245 : */
1246 337 : MyProc->delayChkptFlags &= ~DELAY_CHKPT_START;
1247 :
1248 : /*
1249 : * Remember that we have this GlobalTransaction entry locked for us. If
1250 : * we crash after this point, it's too late to abort, but we must unlock
1251 : * it so that the prepared transaction can be committed or rolled back.
1252 : */
1253 337 : MyLockedGxact = gxact;
1254 :
1255 337 : END_CRIT_SECTION();
1256 :
1257 : /*
1258 : * Wait for synchronous replication, if required.
1259 : *
1260 : * Note that at this stage we have marked the prepare, but still show as
1261 : * running in the procarray (twice!) and continue to hold locks.
1262 : */
1263 337 : SyncRepWaitForLSN(gxact->prepare_end_lsn, false);
1264 :
1265 337 : records.tail = records.head = NULL;
1266 337 : records.num_chunks = 0;
1267 337 : }
1268 :
1269 : /*
1270 : * Register a 2PC record to be written to state file.
1271 : */
1272 : void
1273 1753 : RegisterTwoPhaseRecord(TwoPhaseRmgrId rmid, uint16 info,
1274 : const void *data, uint32 len)
1275 : {
1276 : TwoPhaseRecordOnDisk record;
1277 :
1278 1753 : record.rmid = rmid;
1279 1753 : record.info = info;
1280 1753 : record.len = len;
1281 1753 : save_state_data(&record, sizeof(TwoPhaseRecordOnDisk));
1282 1753 : if (len > 0)
1283 1416 : save_state_data(data, len);
1284 1753 : }
1285 :
1286 :
1287 : /*
1288 : * Read and validate the state file for xid.
1289 : *
1290 : * If it looks OK (has a valid magic number and CRC), return the palloc'd
1291 : * contents of the file, issuing an error when finding corrupted data. If
1292 : * missing_ok is true, which indicates that missing files can be safely
1293 : * ignored, then return NULL. This state can be reached when doing recovery
1294 : * after discarding two-phase files from frozen epochs.
1295 : */
1296 : static char *
1297 364 : ReadTwoPhaseFile(FullTransactionId fxid, bool missing_ok)
1298 : {
1299 : char path[MAXPGPATH];
1300 : char *buf;
1301 : TwoPhaseFileHeader *hdr;
1302 : int fd;
1303 : struct stat stat;
1304 : uint32 crc_offset;
1305 : pg_crc32c calc_crc,
1306 : file_crc;
1307 : int r;
1308 :
1309 364 : TwoPhaseFilePath(path, fxid);
1310 :
1311 364 : fd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
1312 364 : if (fd < 0)
1313 : {
1314 287 : if (missing_ok && errno == ENOENT)
1315 287 : return NULL;
1316 :
1317 0 : ereport(ERROR,
1318 : (errcode_for_file_access(),
1319 : errmsg("could not open file \"%s\": %m", path)));
1320 : }
1321 :
1322 : /*
1323 : * Check file length. We can determine a lower bound pretty easily. We
1324 : * set an upper bound to avoid palloc() failure on a corrupt file, though
1325 : * we can't guarantee that we won't get an out of memory error anyway,
1326 : * even on a valid file.
1327 : */
1328 77 : if (fstat(fd, &stat))
1329 0 : ereport(ERROR,
1330 : (errcode_for_file_access(),
1331 : errmsg("could not stat file \"%s\": %m", path)));
1332 :
1333 77 : if (stat.st_size < (MAXALIGN(sizeof(TwoPhaseFileHeader)) +
1334 : MAXALIGN(sizeof(TwoPhaseRecordOnDisk)) +
1335 77 : sizeof(pg_crc32c)) ||
1336 77 : stat.st_size > MaxAllocSize)
1337 0 : ereport(ERROR,
1338 : (errcode(ERRCODE_DATA_CORRUPTED),
1339 : errmsg_plural("incorrect size of file \"%s\": %lld byte",
1340 : "incorrect size of file \"%s\": %lld bytes",
1341 : (long long int) stat.st_size, path,
1342 : (long long int) stat.st_size)));
1343 :
1344 77 : crc_offset = stat.st_size - sizeof(pg_crc32c);
1345 77 : if (crc_offset != MAXALIGN(crc_offset))
1346 0 : ereport(ERROR,
1347 : (errcode(ERRCODE_DATA_CORRUPTED),
1348 : errmsg("incorrect alignment of CRC offset for file \"%s\"",
1349 : path)));
1350 :
1351 : /*
1352 : * OK, slurp in the file.
1353 : */
1354 77 : buf = (char *) palloc(stat.st_size);
1355 :
1356 77 : pgstat_report_wait_start(WAIT_EVENT_TWOPHASE_FILE_READ);
1357 77 : r = read(fd, buf, stat.st_size);
1358 77 : if (r != stat.st_size)
1359 : {
1360 0 : if (r < 0)
1361 0 : ereport(ERROR,
1362 : (errcode_for_file_access(),
1363 : errmsg("could not read file \"%s\": %m", path)));
1364 : else
1365 0 : ereport(ERROR,
1366 : (errmsg("could not read file \"%s\": read %d of %lld",
1367 : path, r, (long long int) stat.st_size)));
1368 : }
1369 :
1370 77 : pgstat_report_wait_end();
1371 :
1372 77 : if (CloseTransientFile(fd) != 0)
1373 0 : ereport(ERROR,
1374 : (errcode_for_file_access(),
1375 : errmsg("could not close file \"%s\": %m", path)));
1376 :
1377 77 : hdr = (TwoPhaseFileHeader *) buf;
1378 77 : if (hdr->magic != TWOPHASE_MAGIC)
1379 0 : ereport(ERROR,
1380 : (errcode(ERRCODE_DATA_CORRUPTED),
1381 : errmsg("invalid magic number stored in file \"%s\"",
1382 : path)));
1383 :
1384 77 : if (hdr->total_len != stat.st_size)
1385 0 : ereport(ERROR,
1386 : (errcode(ERRCODE_DATA_CORRUPTED),
1387 : errmsg("invalid size stored in file \"%s\"",
1388 : path)));
1389 :
1390 77 : INIT_CRC32C(calc_crc);
1391 77 : COMP_CRC32C(calc_crc, buf, crc_offset);
1392 77 : FIN_CRC32C(calc_crc);
1393 :
1394 77 : file_crc = *((pg_crc32c *) (buf + crc_offset));
1395 :
1396 77 : if (!EQ_CRC32C(calc_crc, file_crc))
1397 0 : ereport(ERROR,
1398 : (errcode(ERRCODE_DATA_CORRUPTED),
1399 : errmsg("calculated CRC checksum does not match value stored in file \"%s\"",
1400 : path)));
1401 :
1402 77 : return buf;
1403 : }
1404 :
1405 :
1406 : /*
1407 : * Reads 2PC data from xlog. During checkpoint this data will be moved to
1408 : * twophase files and ReadTwoPhaseFile should be used instead.
1409 : *
1410 : * Note clearly that this function can access WAL during normal operation,
1411 : * similarly to the way WALSender or Logical Decoding would do.
1412 : */
1413 : static void
1414 421 : XlogReadTwoPhaseData(XLogRecPtr lsn, char **buf, int *len)
1415 : {
1416 : XLogRecord *record;
1417 : XLogReaderState *xlogreader;
1418 : char *errormsg;
1419 :
1420 421 : xlogreader = XLogReaderAllocate(wal_segment_size, NULL,
1421 421 : XL_ROUTINE(.page_read = &read_local_xlog_page,
1422 : .segment_open = &wal_segment_open,
1423 : .segment_close = &wal_segment_close),
1424 : NULL);
1425 421 : if (!xlogreader)
1426 0 : ereport(ERROR,
1427 : (errcode(ERRCODE_OUT_OF_MEMORY),
1428 : errmsg("out of memory"),
1429 : errdetail("Failed while allocating a WAL reading processor.")));
1430 :
1431 421 : XLogBeginRead(xlogreader, lsn);
1432 421 : record = XLogReadRecord(xlogreader, &errormsg);
1433 :
1434 421 : if (record == NULL)
1435 : {
1436 0 : if (errormsg)
1437 0 : ereport(ERROR,
1438 : (errcode_for_file_access(),
1439 : errmsg("could not read two-phase state from WAL at %X/%08X: %s",
1440 : LSN_FORMAT_ARGS(lsn), errormsg)));
1441 : else
1442 0 : ereport(ERROR,
1443 : (errcode_for_file_access(),
1444 : errmsg("could not read two-phase state from WAL at %X/%08X",
1445 : LSN_FORMAT_ARGS(lsn))));
1446 : }
1447 :
1448 421 : if (XLogRecGetRmid(xlogreader) != RM_XACT_ID ||
1449 421 : (XLogRecGetInfo(xlogreader) & XLOG_XACT_OPMASK) != XLOG_XACT_PREPARE)
1450 0 : ereport(ERROR,
1451 : (errcode_for_file_access(),
1452 : errmsg("expected two-phase state data is not present in WAL at %X/%08X",
1453 : LSN_FORMAT_ARGS(lsn))));
1454 :
1455 421 : if (len != NULL)
1456 26 : *len = XLogRecGetDataLen(xlogreader);
1457 :
1458 421 : *buf = palloc_array(char, XLogRecGetDataLen(xlogreader));
1459 421 : memcpy(*buf, XLogRecGetData(xlogreader), sizeof(char) * XLogRecGetDataLen(xlogreader));
1460 :
1461 421 : XLogReaderFree(xlogreader);
1462 421 : }
1463 :
1464 :
1465 : /*
1466 : * Confirms an xid is prepared, during recovery
1467 : */
1468 : bool
1469 287 : StandbyTransactionIdIsPrepared(TransactionId xid)
1470 : {
1471 : char *buf;
1472 : TwoPhaseFileHeader *hdr;
1473 : bool result;
1474 : FullTransactionId fxid;
1475 :
1476 : Assert(TransactionIdIsValid(xid));
1477 :
1478 287 : if (max_prepared_xacts <= 0)
1479 0 : return false; /* nothing to do */
1480 :
1481 : /* Read and validate file */
1482 287 : fxid = AdjustToFullTransactionId(xid);
1483 287 : buf = ReadTwoPhaseFile(fxid, true);
1484 287 : if (buf == NULL)
1485 287 : return false;
1486 :
1487 : /* Check header also */
1488 0 : hdr = (TwoPhaseFileHeader *) buf;
1489 0 : result = TransactionIdEquals(hdr->xid, xid);
1490 0 : pfree(buf);
1491 :
1492 0 : return result;
1493 : }
1494 :
1495 : /*
1496 : * FinishPreparedTransaction: execute COMMIT PREPARED or ROLLBACK PREPARED
1497 : */
1498 : void
1499 350 : FinishPreparedTransaction(const char *gid, bool isCommit)
1500 : {
1501 : GlobalTransaction gxact;
1502 : PGPROC *proc;
1503 : FullTransactionId fxid;
1504 : TransactionId xid;
1505 : bool ondisk;
1506 : char *buf;
1507 : char *bufptr;
1508 : TwoPhaseFileHeader *hdr;
1509 : TransactionId latestXid;
1510 : TransactionId *children;
1511 : RelFileLocator *commitrels;
1512 : RelFileLocator *abortrels;
1513 : RelFileLocator *delrels;
1514 : int ndelrels;
1515 : xl_xact_stats_item *commitstats;
1516 : xl_xact_stats_item *abortstats;
1517 : SharedInvalidationMessage *invalmsgs;
1518 :
1519 : /*
1520 : * Validate the GID, and lock the GXACT to ensure that two backends do not
1521 : * try to commit the same GID at once.
1522 : */
1523 350 : gxact = LockGXact(gid, GetUserId());
1524 343 : proc = GetPGProcByNumber(gxact->pgprocno);
1525 343 : fxid = gxact->fxid;
1526 343 : xid = XidFromFullTransactionId(fxid);
1527 :
1528 : /*
1529 : * Read and validate 2PC state data. State data will typically be stored
1530 : * in WAL files if the LSN is after the last checkpoint record, or moved
1531 : * to disk if for some reason they have lived for a long time.
1532 : */
1533 343 : if (gxact->ondisk)
1534 27 : buf = ReadTwoPhaseFile(fxid, false);
1535 : else
1536 316 : XlogReadTwoPhaseData(gxact->prepare_start_lsn, &buf, NULL);
1537 :
1538 :
1539 : /*
1540 : * Disassemble the header area
1541 : */
1542 343 : hdr = (TwoPhaseFileHeader *) buf;
1543 : Assert(TransactionIdEquals(hdr->xid, xid));
1544 343 : bufptr = buf + MAXALIGN(sizeof(TwoPhaseFileHeader));
1545 343 : bufptr += MAXALIGN(hdr->gidlen);
1546 343 : children = (TransactionId *) bufptr;
1547 343 : bufptr += MAXALIGN(hdr->nsubxacts * sizeof(TransactionId));
1548 343 : commitrels = (RelFileLocator *) bufptr;
1549 343 : bufptr += MAXALIGN(hdr->ncommitrels * sizeof(RelFileLocator));
1550 343 : abortrels = (RelFileLocator *) bufptr;
1551 343 : bufptr += MAXALIGN(hdr->nabortrels * sizeof(RelFileLocator));
1552 343 : commitstats = (xl_xact_stats_item *) bufptr;
1553 343 : bufptr += MAXALIGN(hdr->ncommitstats * sizeof(xl_xact_stats_item));
1554 343 : abortstats = (xl_xact_stats_item *) bufptr;
1555 343 : bufptr += MAXALIGN(hdr->nabortstats * sizeof(xl_xact_stats_item));
1556 343 : invalmsgs = (SharedInvalidationMessage *) bufptr;
1557 343 : bufptr += MAXALIGN(hdr->ninvalmsgs * sizeof(SharedInvalidationMessage));
1558 :
1559 : /* compute latestXid among all children */
1560 343 : latestXid = TransactionIdLatest(xid, hdr->nsubxacts, children);
1561 :
1562 : /* Prevent cancel/die interrupt while cleaning up */
1563 343 : HOLD_INTERRUPTS();
1564 :
1565 : /*
1566 : * The order of operations here is critical: make the XLOG entry for
1567 : * commit or abort, then mark the transaction committed or aborted in
1568 : * pg_xact, then remove its PGPROC from the global ProcArray (which means
1569 : * TransactionIdIsInProgress will stop saying the prepared xact is in
1570 : * progress), then run the post-commit or post-abort callbacks. The
1571 : * callbacks will release the locks the transaction held.
1572 : */
1573 343 : if (isCommit)
1574 294 : RecordTransactionCommitPrepared(xid,
1575 : hdr->nsubxacts, children,
1576 : hdr->ncommitrels, commitrels,
1577 : hdr->ncommitstats,
1578 : commitstats,
1579 : hdr->ninvalmsgs, invalmsgs,
1580 294 : hdr->initfileinval, gid);
1581 : else
1582 49 : RecordTransactionAbortPrepared(xid,
1583 : hdr->nsubxacts, children,
1584 : hdr->nabortrels, abortrels,
1585 : hdr->nabortstats,
1586 : abortstats,
1587 : gid);
1588 :
1589 343 : ProcArrayRemove(proc, latestXid);
1590 :
1591 : /*
1592 : * In case we fail while running the callbacks, mark the gxact invalid so
1593 : * no one else will try to commit/rollback, and so it will be recycled if
1594 : * we fail after this point. It is still locked by our backend so it
1595 : * won't go away yet.
1596 : *
1597 : * (We assume it's safe to do this without taking TwoPhaseStateLock.)
1598 : */
1599 343 : gxact->valid = false;
1600 :
1601 : /*
1602 : * We have to remove any files that were supposed to be dropped. For
1603 : * consistency with the regular xact.c code paths, must do this before
1604 : * releasing locks, so do it before running the callbacks.
1605 : *
1606 : * NB: this code knows that we couldn't be dropping any temp rels ...
1607 : */
1608 343 : if (isCommit)
1609 : {
1610 294 : delrels = commitrels;
1611 294 : ndelrels = hdr->ncommitrels;
1612 : }
1613 : else
1614 : {
1615 49 : delrels = abortrels;
1616 49 : ndelrels = hdr->nabortrels;
1617 : }
1618 :
1619 : /* Make sure files supposed to be dropped are dropped */
1620 343 : DropRelationFiles(delrels, ndelrels, false);
1621 :
1622 343 : if (isCommit)
1623 294 : pgstat_execute_transactional_drops(hdr->ncommitstats, commitstats, false);
1624 : else
1625 49 : pgstat_execute_transactional_drops(hdr->nabortstats, abortstats, false);
1626 :
1627 : /*
1628 : * Handle cache invalidation messages.
1629 : *
1630 : * Relcache init file invalidation requires processing both before and
1631 : * after we send the SI messages, only when committing. See
1632 : * AtEOXact_Inval().
1633 : */
1634 343 : if (isCommit)
1635 : {
1636 294 : if (hdr->initfileinval)
1637 0 : RelationCacheInitFilePreInvalidate();
1638 294 : SendSharedInvalidMessages(invalmsgs, hdr->ninvalmsgs);
1639 294 : if (hdr->initfileinval)
1640 0 : RelationCacheInitFilePostInvalidate();
1641 : }
1642 :
1643 : /*
1644 : * Acquire the two-phase lock. We want to work on the two-phase callbacks
1645 : * while holding it to avoid potential conflicts with other transactions
1646 : * attempting to use the same GID, so the lock is released once the shared
1647 : * memory state is cleared.
1648 : */
1649 343 : LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
1650 :
1651 : /* And now do the callbacks */
1652 343 : if (isCommit)
1653 294 : ProcessRecords(bufptr, fxid, twophase_postcommit_callbacks);
1654 : else
1655 49 : ProcessRecords(bufptr, fxid, twophase_postabort_callbacks);
1656 :
1657 343 : PredicateLockTwoPhaseFinish(fxid, isCommit);
1658 :
1659 : /*
1660 : * Read this value while holding the two-phase lock, as the on-disk 2PC
1661 : * file is physically removed after the lock is released.
1662 : */
1663 343 : ondisk = gxact->ondisk;
1664 :
1665 : /* Clear shared memory state */
1666 343 : RemoveGXact(gxact);
1667 :
1668 : /*
1669 : * Release the lock as all callbacks are called and shared memory cleanup
1670 : * is done.
1671 : */
1672 343 : LWLockRelease(TwoPhaseStateLock);
1673 :
1674 : /* Count the prepared xact as committed or aborted */
1675 343 : AtEOXact_PgStat(isCommit, false);
1676 :
1677 : /*
1678 : * And now we can clean up any files we may have left.
1679 : */
1680 343 : if (ondisk)
1681 27 : RemoveTwoPhaseFile(fxid, true);
1682 :
1683 343 : MyLockedGxact = NULL;
1684 :
1685 343 : RESUME_INTERRUPTS();
1686 :
1687 343 : pfree(buf);
1688 343 : }
1689 :
1690 : /*
1691 : * Scan 2PC state data in memory and call the indicated callbacks for each 2PC record.
1692 : */
1693 : static void
1694 376 : ProcessRecords(char *bufptr, FullTransactionId fxid,
1695 : const TwoPhaseCallback callbacks[])
1696 : {
1697 : for (;;)
1698 1609 : {
1699 1985 : TwoPhaseRecordOnDisk *record = (TwoPhaseRecordOnDisk *) bufptr;
1700 :
1701 : Assert(record->rmid <= TWOPHASE_RM_MAX_ID);
1702 1985 : if (record->rmid == TWOPHASE_RM_END_ID)
1703 376 : break;
1704 :
1705 1609 : bufptr += MAXALIGN(sizeof(TwoPhaseRecordOnDisk));
1706 :
1707 1609 : if (callbacks[record->rmid] != NULL)
1708 1530 : callbacks[record->rmid] (fxid, record->info, bufptr, record->len);
1709 :
1710 1609 : bufptr += MAXALIGN(record->len);
1711 : }
1712 376 : }
1713 :
1714 : /*
1715 : * Remove the 2PC file.
1716 : *
1717 : * If giveWarning is false, do not complain about file-not-present;
1718 : * this is an expected case during WAL replay.
1719 : *
1720 : * This routine is used at early stages at recovery where future and
1721 : * past orphaned files are checked, hence the FullTransactionId to build
1722 : * a complete file name fit for the removal.
1723 : */
1724 : static void
1725 32 : RemoveTwoPhaseFile(FullTransactionId fxid, bool giveWarning)
1726 : {
1727 : char path[MAXPGPATH];
1728 :
1729 32 : TwoPhaseFilePath(path, fxid);
1730 32 : if (unlink(path))
1731 0 : if (errno != ENOENT || giveWarning)
1732 0 : ereport(WARNING,
1733 : (errcode_for_file_access(),
1734 : errmsg("could not remove file \"%s\": %m", path)));
1735 32 : }
1736 :
1737 : /*
1738 : * Recreates a state file. This is used in WAL replay and during
1739 : * checkpoint creation.
1740 : *
1741 : * Note: content and len don't include CRC.
1742 : */
1743 : static void
1744 26 : RecreateTwoPhaseFile(FullTransactionId fxid, void *content, int len)
1745 : {
1746 : char path[MAXPGPATH];
1747 : pg_crc32c statefile_crc;
1748 : int fd;
1749 :
1750 : /* Recompute CRC */
1751 26 : INIT_CRC32C(statefile_crc);
1752 26 : COMP_CRC32C(statefile_crc, content, len);
1753 26 : FIN_CRC32C(statefile_crc);
1754 :
1755 26 : TwoPhaseFilePath(path, fxid);
1756 :
1757 26 : fd = OpenTransientFile(path,
1758 : O_CREAT | O_TRUNC | O_WRONLY | PG_BINARY);
1759 26 : if (fd < 0)
1760 0 : ereport(ERROR,
1761 : (errcode_for_file_access(),
1762 : errmsg("could not recreate file \"%s\": %m", path)));
1763 :
1764 : /* Write content and CRC */
1765 26 : errno = 0;
1766 26 : pgstat_report_wait_start(WAIT_EVENT_TWOPHASE_FILE_WRITE);
1767 26 : if (write(fd, content, len) != len)
1768 : {
1769 : /* if write didn't set errno, assume problem is no disk space */
1770 0 : if (errno == 0)
1771 0 : errno = ENOSPC;
1772 0 : ereport(ERROR,
1773 : (errcode_for_file_access(),
1774 : errmsg("could not write file \"%s\": %m", path)));
1775 : }
1776 26 : if (write(fd, &statefile_crc, sizeof(pg_crc32c)) != sizeof(pg_crc32c))
1777 : {
1778 : /* if write didn't set errno, assume problem is no disk space */
1779 0 : if (errno == 0)
1780 0 : errno = ENOSPC;
1781 0 : ereport(ERROR,
1782 : (errcode_for_file_access(),
1783 : errmsg("could not write file \"%s\": %m", path)));
1784 : }
1785 26 : pgstat_report_wait_end();
1786 :
1787 : /*
1788 : * We must fsync the file because the end-of-replay checkpoint will not do
1789 : * so, there being no GXACT in shared memory yet to tell it to.
1790 : */
1791 26 : pgstat_report_wait_start(WAIT_EVENT_TWOPHASE_FILE_SYNC);
1792 26 : if (pg_fsync(fd) != 0)
1793 0 : ereport(ERROR,
1794 : (errcode_for_file_access(),
1795 : errmsg("could not fsync file \"%s\": %m", path)));
1796 26 : pgstat_report_wait_end();
1797 :
1798 26 : if (CloseTransientFile(fd) != 0)
1799 0 : ereport(ERROR,
1800 : (errcode_for_file_access(),
1801 : errmsg("could not close file \"%s\": %m", path)));
1802 26 : }
1803 :
1804 : /*
1805 : * CheckPointTwoPhase -- handle 2PC component of checkpointing.
1806 : *
1807 : * We must fsync the state file of any GXACT that is valid or has been
1808 : * generated during redo and has a PREPARE LSN <= the checkpoint's redo
1809 : * horizon. (If the gxact isn't valid yet, has not been generated in
1810 : * redo, or has a later LSN, this checkpoint is not responsible for
1811 : * fsyncing it.)
1812 : *
1813 : * This is deliberately run as late as possible in the checkpoint sequence,
1814 : * because GXACTs ordinarily have short lifespans, and so it is quite
1815 : * possible that GXACTs that were valid at checkpoint start will no longer
1816 : * exist if we wait a little bit. With typical checkpoint settings this
1817 : * will be about 3 minutes for an online checkpoint, so as a result we
1818 : * expect that there will be no GXACTs that need to be copied to disk.
1819 : *
1820 : * If a GXACT remains valid across multiple checkpoints, it will already
1821 : * be on disk so we don't bother to repeat that write.
1822 : */
1823 : void
1824 1807 : CheckPointTwoPhase(XLogRecPtr redo_horizon)
1825 : {
1826 : int i;
1827 1807 : int serialized_xacts = 0;
1828 :
1829 1807 : if (max_prepared_xacts <= 0)
1830 1265 : return; /* nothing to do */
1831 :
1832 : TRACE_POSTGRESQL_TWOPHASE_CHECKPOINT_START();
1833 :
1834 : /*
1835 : * We are expecting there to be zero GXACTs that need to be copied to
1836 : * disk, so we perform all I/O while holding TwoPhaseStateLock for
1837 : * simplicity. This prevents any new xacts from preparing while this
1838 : * occurs, which shouldn't be a problem since the presence of long-lived
1839 : * prepared xacts indicates the transaction manager isn't active.
1840 : *
1841 : * It's also possible to move I/O out of the lock, but on every error we
1842 : * should check whether somebody committed our transaction in different
1843 : * backend. Let's leave this optimization for future, if somebody will
1844 : * spot that this place cause bottleneck.
1845 : *
1846 : * Note that it isn't possible for there to be a GXACT with a
1847 : * prepare_end_lsn set prior to the last checkpoint yet is marked invalid,
1848 : * because of the efforts with delayChkptFlags.
1849 : */
1850 542 : LWLockAcquire(TwoPhaseStateLock, LW_SHARED);
1851 577 : for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
1852 : {
1853 : /*
1854 : * Note that we are using gxact not PGPROC so this works in recovery
1855 : * also
1856 : */
1857 35 : GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
1858 :
1859 35 : if ((gxact->valid || gxact->inredo) &&
1860 34 : !gxact->ondisk &&
1861 30 : gxact->prepare_end_lsn <= redo_horizon)
1862 : {
1863 : char *buf;
1864 : int len;
1865 :
1866 26 : XlogReadTwoPhaseData(gxact->prepare_start_lsn, &buf, &len);
1867 26 : RecreateTwoPhaseFile(gxact->fxid, buf, len);
1868 26 : gxact->ondisk = true;
1869 26 : gxact->prepare_start_lsn = InvalidXLogRecPtr;
1870 26 : gxact->prepare_end_lsn = InvalidXLogRecPtr;
1871 26 : pfree(buf);
1872 26 : serialized_xacts++;
1873 : }
1874 : }
1875 542 : LWLockRelease(TwoPhaseStateLock);
1876 :
1877 : /*
1878 : * Flush unconditionally the parent directory to make any information
1879 : * durable on disk. Two-phase files could have been removed and those
1880 : * removals need to be made persistent as well as any files newly created
1881 : * previously since the last checkpoint.
1882 : */
1883 542 : fsync_fname(TWOPHASE_DIR, true);
1884 :
1885 : TRACE_POSTGRESQL_TWOPHASE_CHECKPOINT_DONE();
1886 :
1887 542 : if (log_checkpoints && serialized_xacts > 0)
1888 22 : ereport(LOG,
1889 : (errmsg_plural("%u two-phase state file was written "
1890 : "for a long-running prepared transaction",
1891 : "%u two-phase state files were written "
1892 : "for long-running prepared transactions",
1893 : serialized_xacts,
1894 : serialized_xacts)));
1895 : }
1896 :
1897 : /*
1898 : * restoreTwoPhaseData
1899 : *
1900 : * Scan pg_twophase and fill TwoPhaseState depending on the on-disk data.
1901 : * This is called once at the beginning of recovery, saving any extra
1902 : * lookups in the future. Two-phase files that are newer than the
1903 : * minimum XID horizon are discarded on the way.
1904 : */
1905 : void
1906 1008 : restoreTwoPhaseData(void)
1907 : {
1908 : DIR *cldir;
1909 : struct dirent *clde;
1910 :
1911 1008 : LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
1912 1008 : cldir = AllocateDir(TWOPHASE_DIR);
1913 3040 : while ((clde = ReadDir(cldir, TWOPHASE_DIR)) != NULL)
1914 : {
1915 2032 : if (strlen(clde->d_name) == 16 &&
1916 16 : strspn(clde->d_name, "0123456789ABCDEF") == 16)
1917 : {
1918 : FullTransactionId fxid;
1919 : char *buf;
1920 :
1921 16 : fxid = FullTransactionIdFromU64(strtou64(clde->d_name, NULL, 16));
1922 :
1923 16 : buf = ProcessTwoPhaseBuffer(fxid, InvalidXLogRecPtr,
1924 : true, false, false);
1925 16 : if (buf == NULL)
1926 0 : continue;
1927 :
1928 16 : PrepareRedoAdd(fxid, buf, InvalidXLogRecPtr,
1929 : InvalidXLogRecPtr, InvalidReplOriginId);
1930 : }
1931 : }
1932 1008 : LWLockRelease(TwoPhaseStateLock);
1933 1008 : FreeDir(cldir);
1934 1008 : }
1935 :
1936 : /*
1937 : * PrescanPreparedTransactions
1938 : *
1939 : * Scan the shared memory entries of TwoPhaseState and determine the range
1940 : * of valid XIDs present. This is run during database startup, after we
1941 : * have completed reading WAL. TransamVariables->nextXid has been set to
1942 : * one more than the highest XID for which evidence exists in WAL.
1943 : *
1944 : * We throw away any prepared xacts with main XID beyond nextXid --- if any
1945 : * are present, it suggests that the DBA has done a PITR recovery to an
1946 : * earlier point in time without cleaning out pg_twophase. We dare not
1947 : * try to recover such prepared xacts since they likely depend on database
1948 : * state that doesn't exist now.
1949 : *
1950 : * However, we will advance nextXid beyond any subxact XIDs belonging to
1951 : * valid prepared xacts. We need to do this since subxact commit doesn't
1952 : * write a WAL entry, and so there might be no evidence in WAL of those
1953 : * subxact XIDs.
1954 : *
1955 : * On corrupted two-phase files, fail immediately. Keeping around broken
1956 : * entries and let replay continue causes harm on the system, and a new
1957 : * backup should be rolled in.
1958 : *
1959 : * Our other responsibility is to determine and return the oldest valid XID
1960 : * among the prepared xacts (if none, return TransamVariables->nextXid).
1961 : * This is needed to synchronize pg_subtrans startup properly.
1962 : *
1963 : * If xids_p and nxids_p are not NULL, pointer to a palloc'd array of all
1964 : * top-level xids is stored in *xids_p. The number of entries in the array
1965 : * is returned in *nxids_p.
1966 : */
1967 : TransactionId
1968 1013 : PrescanPreparedTransactions(TransactionId **xids_p, int *nxids_p)
1969 : {
1970 1013 : FullTransactionId nextXid = TransamVariables->nextXid;
1971 1013 : TransactionId origNextXid = XidFromFullTransactionId(nextXid);
1972 1013 : TransactionId result = origNextXid;
1973 1013 : TransactionId *xids = NULL;
1974 1013 : int nxids = 0;
1975 1013 : int allocsize = 0;
1976 : int i;
1977 :
1978 1013 : LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
1979 1067 : for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
1980 : {
1981 : TransactionId xid;
1982 : char *buf;
1983 54 : GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
1984 :
1985 : Assert(gxact->inredo);
1986 :
1987 54 : buf = ProcessTwoPhaseBuffer(gxact->fxid,
1988 : gxact->prepare_start_lsn,
1989 54 : gxact->ondisk, false, true);
1990 :
1991 54 : if (buf == NULL)
1992 0 : continue;
1993 :
1994 : /*
1995 : * OK, we think this file is valid. Incorporate xid into the
1996 : * running-minimum result.
1997 : */
1998 54 : xid = XidFromFullTransactionId(gxact->fxid);
1999 54 : if (TransactionIdPrecedes(xid, result))
2000 46 : result = xid;
2001 :
2002 54 : if (xids_p)
2003 : {
2004 21 : if (nxids == allocsize)
2005 : {
2006 17 : if (nxids == 0)
2007 : {
2008 17 : allocsize = 10;
2009 17 : xids = palloc(allocsize * sizeof(TransactionId));
2010 : }
2011 : else
2012 : {
2013 0 : allocsize = allocsize * 2;
2014 0 : xids = repalloc(xids, allocsize * sizeof(TransactionId));
2015 : }
2016 : }
2017 21 : xids[nxids++] = xid;
2018 : }
2019 :
2020 54 : pfree(buf);
2021 : }
2022 1013 : LWLockRelease(TwoPhaseStateLock);
2023 :
2024 1013 : if (xids_p)
2025 : {
2026 66 : *xids_p = xids;
2027 66 : *nxids_p = nxids;
2028 : }
2029 :
2030 1013 : return result;
2031 : }
2032 :
2033 : /*
2034 : * StandbyRecoverPreparedTransactions
2035 : *
2036 : * Scan the shared memory entries of TwoPhaseState and setup all the required
2037 : * information to allow standby queries to treat prepared transactions as still
2038 : * active.
2039 : *
2040 : * This is never called at the end of recovery - we use
2041 : * RecoverPreparedTransactions() at that point.
2042 : *
2043 : * This updates pg_subtrans, so that any subtransactions will be correctly
2044 : * seen as in-progress in snapshots taken during recovery.
2045 : */
2046 : void
2047 66 : StandbyRecoverPreparedTransactions(void)
2048 : {
2049 : int i;
2050 :
2051 66 : LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
2052 87 : for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
2053 : {
2054 : char *buf;
2055 21 : GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
2056 :
2057 : Assert(gxact->inredo);
2058 :
2059 21 : buf = ProcessTwoPhaseBuffer(gxact->fxid,
2060 : gxact->prepare_start_lsn,
2061 21 : gxact->ondisk, true, false);
2062 21 : if (buf != NULL)
2063 21 : pfree(buf);
2064 : }
2065 66 : LWLockRelease(TwoPhaseStateLock);
2066 66 : }
2067 :
2068 : /*
2069 : * RecoverPreparedTransactions
2070 : *
2071 : * Scan the shared memory entries of TwoPhaseState and reload the state for
2072 : * each prepared transaction (reacquire locks, etc).
2073 : *
2074 : * This is run at the end of recovery, but before we allow backends to write
2075 : * WAL.
2076 : *
2077 : * At the end of recovery the way we take snapshots will change. We now need
2078 : * to mark all running transactions with their full SubTransSetParent() info
2079 : * to allow normal snapshots to work correctly if snapshots overflow.
2080 : * We do this here because by definition prepared transactions are the only
2081 : * type of write transaction still running, so this is necessary and
2082 : * complete.
2083 : */
2084 : void
2085 947 : RecoverPreparedTransactions(void)
2086 : {
2087 : int i;
2088 :
2089 947 : LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
2090 980 : for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
2091 : {
2092 : char *buf;
2093 33 : GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
2094 33 : FullTransactionId fxid = gxact->fxid;
2095 : char *bufptr;
2096 : TwoPhaseFileHeader *hdr;
2097 : TransactionId *subxids;
2098 : const char *gid;
2099 :
2100 : /*
2101 : * Reconstruct subtrans state for the transaction --- needed because
2102 : * pg_subtrans is not preserved over a restart. Note that we are
2103 : * linking all the subtransactions directly to the top-level XID;
2104 : * there may originally have been a more complex hierarchy, but
2105 : * there's no need to restore that exactly. It's possible that
2106 : * SubTransSetParent has been set before, if the prepared transaction
2107 : * generated xid assignment records.
2108 : */
2109 33 : buf = ProcessTwoPhaseBuffer(gxact->fxid,
2110 : gxact->prepare_start_lsn,
2111 33 : gxact->ondisk, true, false);
2112 33 : if (buf == NULL)
2113 0 : continue;
2114 :
2115 33 : ereport(LOG,
2116 : (errmsg("recovering prepared transaction %u of epoch %u from shared memory",
2117 : XidFromFullTransactionId(gxact->fxid),
2118 : EpochFromFullTransactionId(gxact->fxid))));
2119 :
2120 33 : hdr = (TwoPhaseFileHeader *) buf;
2121 : Assert(TransactionIdEquals(hdr->xid,
2122 : XidFromFullTransactionId(gxact->fxid)));
2123 33 : bufptr = buf + MAXALIGN(sizeof(TwoPhaseFileHeader));
2124 33 : gid = (const char *) bufptr;
2125 33 : bufptr += MAXALIGN(hdr->gidlen);
2126 33 : subxids = (TransactionId *) bufptr;
2127 33 : bufptr += MAXALIGN(hdr->nsubxacts * sizeof(TransactionId));
2128 33 : bufptr += MAXALIGN(hdr->ncommitrels * sizeof(RelFileLocator));
2129 33 : bufptr += MAXALIGN(hdr->nabortrels * sizeof(RelFileLocator));
2130 33 : bufptr += MAXALIGN(hdr->ncommitstats * sizeof(xl_xact_stats_item));
2131 33 : bufptr += MAXALIGN(hdr->nabortstats * sizeof(xl_xact_stats_item));
2132 33 : bufptr += MAXALIGN(hdr->ninvalmsgs * sizeof(SharedInvalidationMessage));
2133 :
2134 : /*
2135 : * Recreate its GXACT and dummy PGPROC. But, check whether it was
2136 : * added in redo and already has a shmem entry for it.
2137 : */
2138 33 : MarkAsPreparingGuts(gxact, gxact->fxid, gid,
2139 : hdr->prepared_at,
2140 : hdr->owner, hdr->database);
2141 :
2142 : /* recovered, so reset the flag for entries generated by redo */
2143 33 : gxact->inredo = false;
2144 :
2145 33 : GXactLoadSubxactData(gxact, hdr->nsubxacts, subxids);
2146 33 : MarkAsPrepared(gxact, true);
2147 :
2148 33 : LWLockRelease(TwoPhaseStateLock);
2149 :
2150 : /*
2151 : * Recover other state (notably locks) using resource managers.
2152 : */
2153 33 : ProcessRecords(bufptr, fxid, twophase_recover_callbacks);
2154 :
2155 : /*
2156 : * Release locks held by the standby process after we process each
2157 : * prepared transaction. As a result, we don't need too many
2158 : * additional locks at any one time.
2159 : */
2160 33 : if (InHotStandby)
2161 7 : StandbyReleaseLockTree(hdr->xid, hdr->nsubxacts, subxids);
2162 :
2163 : /*
2164 : * We're done with recovering this transaction. Clear MyLockedGxact,
2165 : * like we do in PrepareTransaction() during normal operation.
2166 : */
2167 33 : PostPrepare_Twophase();
2168 :
2169 33 : pfree(buf);
2170 :
2171 33 : LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE);
2172 : }
2173 :
2174 947 : LWLockRelease(TwoPhaseStateLock);
2175 947 : }
2176 :
2177 : /*
2178 : * ProcessTwoPhaseBuffer
2179 : *
2180 : * Given a FullTransactionId, read it either from disk or read it directly
2181 : * via shmem xlog record pointer using the provided "prepare_start_lsn".
2182 : *
2183 : * If setParent is true, set up subtransaction parent linkages.
2184 : *
2185 : * If setNextXid is true, set TransamVariables->nextXid to the newest
2186 : * value scanned.
2187 : */
2188 : static char *
2189 124 : ProcessTwoPhaseBuffer(FullTransactionId fxid,
2190 : XLogRecPtr prepare_start_lsn,
2191 : bool fromdisk,
2192 : bool setParent, bool setNextXid)
2193 : {
2194 124 : FullTransactionId nextXid = TransamVariables->nextXid;
2195 : TransactionId *subxids;
2196 : char *buf;
2197 : TwoPhaseFileHeader *hdr;
2198 : int i;
2199 :
2200 : Assert(LWLockHeldByMeInMode(TwoPhaseStateLock, LW_EXCLUSIVE));
2201 :
2202 124 : if (!fromdisk)
2203 : Assert(XLogRecPtrIsValid(prepare_start_lsn));
2204 :
2205 : /* Already processed? */
2206 248 : if (TransactionIdDidCommit(XidFromFullTransactionId(fxid)) ||
2207 124 : TransactionIdDidAbort(XidFromFullTransactionId(fxid)))
2208 : {
2209 0 : if (fromdisk)
2210 : {
2211 0 : ereport(WARNING,
2212 : (errmsg("removing stale two-phase state file for transaction %u of epoch %u",
2213 : XidFromFullTransactionId(fxid),
2214 : EpochFromFullTransactionId(fxid))));
2215 0 : RemoveTwoPhaseFile(fxid, true);
2216 : }
2217 : else
2218 : {
2219 0 : ereport(WARNING,
2220 : (errmsg("removing stale two-phase state from memory for transaction %u of epoch %u",
2221 : XidFromFullTransactionId(fxid),
2222 : EpochFromFullTransactionId(fxid))));
2223 0 : PrepareRedoRemoveFull(fxid, true);
2224 : }
2225 0 : return NULL;
2226 : }
2227 :
2228 : /* Reject XID if too new */
2229 124 : if (FullTransactionIdFollowsOrEquals(fxid, nextXid))
2230 : {
2231 0 : if (fromdisk)
2232 : {
2233 0 : ereport(WARNING,
2234 : (errmsg("removing future two-phase state file for transaction %u of epoch %u",
2235 : XidFromFullTransactionId(fxid),
2236 : EpochFromFullTransactionId(fxid))));
2237 0 : RemoveTwoPhaseFile(fxid, true);
2238 : }
2239 : else
2240 : {
2241 0 : ereport(WARNING,
2242 : (errmsg("removing future two-phase state from memory for transaction %u of epoch %u",
2243 : XidFromFullTransactionId(fxid),
2244 : EpochFromFullTransactionId(fxid))));
2245 0 : PrepareRedoRemoveFull(fxid, true);
2246 : }
2247 0 : return NULL;
2248 : }
2249 :
2250 124 : if (fromdisk)
2251 : {
2252 : /* Read and validate file */
2253 50 : buf = ReadTwoPhaseFile(fxid, false);
2254 : }
2255 : else
2256 : {
2257 : /* Read xlog data */
2258 74 : XlogReadTwoPhaseData(prepare_start_lsn, &buf, NULL);
2259 : }
2260 :
2261 : /* Deconstruct header */
2262 124 : hdr = (TwoPhaseFileHeader *) buf;
2263 124 : if (!TransactionIdEquals(hdr->xid, XidFromFullTransactionId(fxid)))
2264 : {
2265 0 : if (fromdisk)
2266 0 : ereport(ERROR,
2267 : (errcode(ERRCODE_DATA_CORRUPTED),
2268 : errmsg("corrupted two-phase state file for transaction %u of epoch %u",
2269 : XidFromFullTransactionId(fxid),
2270 : EpochFromFullTransactionId(fxid))));
2271 : else
2272 0 : ereport(ERROR,
2273 : (errcode(ERRCODE_DATA_CORRUPTED),
2274 : errmsg("corrupted two-phase state in memory for transaction %u of epoch %u",
2275 : XidFromFullTransactionId(fxid),
2276 : EpochFromFullTransactionId(fxid))));
2277 : }
2278 :
2279 : /*
2280 : * Examine subtransaction XIDs ... they should all follow main XID, and
2281 : * they may force us to advance nextXid.
2282 : */
2283 124 : subxids = (TransactionId *) (buf +
2284 124 : MAXALIGN(sizeof(TwoPhaseFileHeader)) +
2285 124 : MAXALIGN(hdr->gidlen));
2286 1911 : for (i = 0; i < hdr->nsubxacts; i++)
2287 : {
2288 1787 : TransactionId subxid = subxids[i];
2289 :
2290 : Assert(TransactionIdFollows(subxid, XidFromFullTransactionId(fxid)));
2291 :
2292 : /* update nextXid if needed */
2293 1787 : if (setNextXid)
2294 823 : AdvanceNextFullTransactionIdPastXid(subxid);
2295 :
2296 1787 : if (setParent)
2297 823 : SubTransSetParent(subxid, XidFromFullTransactionId(fxid));
2298 : }
2299 :
2300 124 : return buf;
2301 : }
2302 :
2303 :
2304 : /*
2305 : * RecordTransactionCommitPrepared
2306 : *
2307 : * This is basically the same as RecordTransactionCommit (q.v. if you change
2308 : * this function): in particular, we must set DELAY_CHKPT_IN_COMMIT to avoid a
2309 : * race condition.
2310 : *
2311 : * We know the transaction made at least one XLOG entry (its PREPARE),
2312 : * so it is never possible to optimize out the commit record.
2313 : */
2314 : static void
2315 294 : RecordTransactionCommitPrepared(TransactionId xid,
2316 : int nchildren,
2317 : TransactionId *children,
2318 : int nrels,
2319 : RelFileLocator *rels,
2320 : int nstats,
2321 : xl_xact_stats_item *stats,
2322 : int ninvalmsgs,
2323 : SharedInvalidationMessage *invalmsgs,
2324 : bool initfileinval,
2325 : const char *gid)
2326 : {
2327 : XLogRecPtr recptr;
2328 : TimestampTz committs;
2329 : bool replorigin;
2330 :
2331 : /*
2332 : * Are we using the replication origins feature? Or, in other words, are
2333 : * we replaying remote actions?
2334 : */
2335 317 : replorigin = (replorigin_xact_state.origin != InvalidReplOriginId &&
2336 23 : replorigin_xact_state.origin != DoNotReplicateId);
2337 :
2338 : /* Load the injection point before entering the critical section */
2339 294 : INJECTION_POINT_LOAD("commit-after-delay-checkpoint");
2340 :
2341 294 : START_CRIT_SECTION();
2342 :
2343 : /* See notes in RecordTransactionCommit */
2344 : Assert((MyProc->delayChkptFlags & DELAY_CHKPT_IN_COMMIT) == 0);
2345 294 : MyProc->delayChkptFlags |= DELAY_CHKPT_IN_COMMIT;
2346 :
2347 294 : INJECTION_POINT_CACHED("commit-after-delay-checkpoint", NULL);
2348 :
2349 : /*
2350 : * Ensures the DELAY_CHKPT_IN_COMMIT flag write is globally visible before
2351 : * commit time is written.
2352 : */
2353 294 : pg_write_barrier();
2354 :
2355 : /*
2356 : * Note it is important to set committs value after marking ourselves as
2357 : * in the commit critical section (DELAY_CHKPT_IN_COMMIT). This is because
2358 : * we want to ensure all transactions that have acquired commit timestamp
2359 : * are finished before we allow the logical replication client to advance
2360 : * its xid which is used to hold back dead rows for conflict detection.
2361 : * See comments atop worker.c.
2362 : */
2363 294 : committs = GetCurrentTimestamp();
2364 :
2365 : /*
2366 : * Emit the XLOG commit record. Note that we mark 2PC commits as
2367 : * potentially having AccessExclusiveLocks since we don't know whether or
2368 : * not they do.
2369 : */
2370 294 : recptr = XactLogCommitRecord(committs,
2371 : nchildren, children, nrels, rels,
2372 : nstats, stats,
2373 : ninvalmsgs, invalmsgs,
2374 : initfileinval,
2375 294 : MyXactFlags | XACT_FLAGS_ACQUIREDACCESSEXCLUSIVELOCK,
2376 : xid, gid);
2377 :
2378 :
2379 294 : if (replorigin)
2380 : /* Move LSNs forward for this replication origin */
2381 23 : replorigin_session_advance(replorigin_xact_state.origin_lsn,
2382 : XactLastRecEnd);
2383 :
2384 : /*
2385 : * Record commit timestamp. The value comes from plain commit timestamp
2386 : * if replorigin is not enabled, or replorigin already set a value for us
2387 : * in replorigin_xact_state.origin_timestamp otherwise.
2388 : *
2389 : * We don't need to WAL-log anything here, as the commit record written
2390 : * above already contains the data.
2391 : */
2392 294 : if (!replorigin || replorigin_xact_state.origin_timestamp == 0)
2393 271 : replorigin_xact_state.origin_timestamp = committs;
2394 :
2395 294 : TransactionTreeSetCommitTsData(xid, nchildren, children,
2396 : replorigin_xact_state.origin_timestamp,
2397 294 : replorigin_xact_state.origin);
2398 :
2399 : /*
2400 : * We don't currently try to sleep before flush here ... nor is there any
2401 : * support for async commit of a prepared xact (the very idea is probably
2402 : * a contradiction)
2403 : */
2404 :
2405 : /* Flush XLOG to disk */
2406 294 : XLogFlush(recptr);
2407 :
2408 : /* Mark the transaction committed in pg_xact */
2409 294 : TransactionIdCommitTree(xid, nchildren, children);
2410 :
2411 : /* Checkpoint can proceed now */
2412 294 : MyProc->delayChkptFlags &= ~DELAY_CHKPT_IN_COMMIT;
2413 :
2414 294 : END_CRIT_SECTION();
2415 :
2416 : /*
2417 : * Wait for synchronous replication, if required.
2418 : *
2419 : * Note that at this stage we have marked clog, but still show as running
2420 : * in the procarray and continue to hold locks.
2421 : */
2422 294 : SyncRepWaitForLSN(recptr, true);
2423 294 : }
2424 :
2425 : /*
2426 : * RecordTransactionAbortPrepared
2427 : *
2428 : * This is basically the same as RecordTransactionAbort.
2429 : *
2430 : * We know the transaction made at least one XLOG entry (its PREPARE),
2431 : * so it is never possible to optimize out the abort record.
2432 : */
2433 : static void
2434 49 : RecordTransactionAbortPrepared(TransactionId xid,
2435 : int nchildren,
2436 : TransactionId *children,
2437 : int nrels,
2438 : RelFileLocator *rels,
2439 : int nstats,
2440 : xl_xact_stats_item *stats,
2441 : const char *gid)
2442 : {
2443 : XLogRecPtr recptr;
2444 : bool replorigin;
2445 :
2446 : /*
2447 : * Are we using the replication origins feature? Or, in other words, are
2448 : * we replaying remote actions?
2449 : */
2450 55 : replorigin = (replorigin_xact_state.origin != InvalidReplOriginId &&
2451 6 : replorigin_xact_state.origin != DoNotReplicateId);
2452 :
2453 : /*
2454 : * Catch the scenario where we aborted partway through
2455 : * RecordTransactionCommitPrepared ...
2456 : */
2457 49 : if (TransactionIdDidCommit(xid))
2458 0 : elog(PANIC, "cannot abort transaction %u, it was already committed",
2459 : xid);
2460 :
2461 49 : START_CRIT_SECTION();
2462 :
2463 : /*
2464 : * Emit the XLOG commit record. Note that we mark 2PC aborts as
2465 : * potentially having AccessExclusiveLocks since we don't know whether or
2466 : * not they do.
2467 : */
2468 49 : recptr = XactLogAbortRecord(GetCurrentTimestamp(),
2469 : nchildren, children,
2470 : nrels, rels,
2471 : nstats, stats,
2472 49 : MyXactFlags | XACT_FLAGS_ACQUIREDACCESSEXCLUSIVELOCK,
2473 : xid, gid);
2474 :
2475 49 : if (replorigin)
2476 : /* Move LSNs forward for this replication origin */
2477 6 : replorigin_session_advance(replorigin_xact_state.origin_lsn,
2478 : XactLastRecEnd);
2479 :
2480 : /* Always flush, since we're about to remove the 2PC state file */
2481 49 : XLogFlush(recptr);
2482 :
2483 : /*
2484 : * Mark the transaction aborted in clog. This is not absolutely necessary
2485 : * but we may as well do it while we are here.
2486 : */
2487 49 : TransactionIdAbortTree(xid, nchildren, children);
2488 :
2489 49 : END_CRIT_SECTION();
2490 :
2491 : /*
2492 : * Wait for synchronous replication, if required.
2493 : *
2494 : * Note that at this stage we have marked clog, but still show as running
2495 : * in the procarray and continue to hold locks.
2496 : */
2497 49 : SyncRepWaitForLSN(recptr, false);
2498 49 : }
2499 :
2500 : /*
2501 : * PrepareRedoAdd
2502 : *
2503 : * Store pointers to the start/end of the WAL record along with the xid in
2504 : * a gxact entry in shared memory TwoPhaseState structure. If caller
2505 : * specifies InvalidXLogRecPtr as WAL location to fetch the two-phase
2506 : * data, the entry is marked as located on disk.
2507 : */
2508 : void
2509 97 : PrepareRedoAdd(FullTransactionId fxid, char *buf,
2510 : XLogRecPtr start_lsn, XLogRecPtr end_lsn,
2511 : ReplOriginId origin_id)
2512 : {
2513 97 : TwoPhaseFileHeader *hdr = (TwoPhaseFileHeader *) buf;
2514 : char *bufptr;
2515 : const char *gid;
2516 : GlobalTransaction gxact;
2517 :
2518 : Assert(LWLockHeldByMeInMode(TwoPhaseStateLock, LW_EXCLUSIVE));
2519 : Assert(RecoveryInProgress());
2520 :
2521 97 : if (!FullTransactionIdIsValid(fxid))
2522 : {
2523 : Assert(InRecovery);
2524 81 : fxid = FullTransactionIdFromAllowableAt(TransamVariables->nextXid,
2525 : hdr->xid);
2526 : }
2527 :
2528 97 : bufptr = buf + MAXALIGN(sizeof(TwoPhaseFileHeader));
2529 97 : gid = (const char *) bufptr;
2530 :
2531 : /*
2532 : * Reserve the GID for the given transaction in the redo code path.
2533 : *
2534 : * This creates a gxact struct and puts it into the active array.
2535 : *
2536 : * In redo, this struct is mainly used to track PREPARE/COMMIT entries in
2537 : * shared memory. Hence, we only fill up the bare minimum contents here.
2538 : * The gxact also gets marked with gxact->inredo set to true to indicate
2539 : * that it got added in the redo phase
2540 : */
2541 :
2542 : /*
2543 : * In the event of a crash while a checkpoint was running, it may be
2544 : * possible that some two-phase data found its way to disk while its
2545 : * corresponding record needs to be replayed in the follow-up recovery. As
2546 : * the 2PC data was on disk, it has already been restored at the beginning
2547 : * of recovery with restoreTwoPhaseData(), so skip this record to avoid
2548 : * duplicates in TwoPhaseState. If a consistent state has been reached,
2549 : * the record is added to TwoPhaseState and it should have no
2550 : * corresponding file in pg_twophase.
2551 : */
2552 97 : if (XLogRecPtrIsValid(start_lsn))
2553 : {
2554 : char path[MAXPGPATH];
2555 :
2556 : Assert(InRecovery);
2557 81 : TwoPhaseFilePath(path, fxid);
2558 :
2559 81 : if (access(path, F_OK) == 0)
2560 : {
2561 0 : ereport(reachedConsistency ? ERROR : WARNING,
2562 : (errmsg("could not recover two-phase state file for transaction %u",
2563 : hdr->xid),
2564 : errdetail("Two-phase state file has been found in WAL record %X/%08X, but this transaction has already been restored from disk.",
2565 : LSN_FORMAT_ARGS(start_lsn))));
2566 0 : return;
2567 : }
2568 :
2569 81 : if (errno != ENOENT)
2570 0 : ereport(ERROR,
2571 : (errcode_for_file_access(),
2572 : errmsg("could not access file \"%s\": %m", path)));
2573 : }
2574 :
2575 : /* Get a free gxact from the freelist */
2576 97 : if (TwoPhaseState->freeGXacts == NULL)
2577 0 : ereport(ERROR,
2578 : (errcode(ERRCODE_OUT_OF_MEMORY),
2579 : errmsg("maximum number of prepared transactions reached"),
2580 : errhint("Increase \"max_prepared_transactions\" (currently %d).",
2581 : max_prepared_xacts)));
2582 97 : gxact = TwoPhaseState->freeGXacts;
2583 97 : TwoPhaseState->freeGXacts = gxact->next;
2584 :
2585 97 : gxact->prepared_at = hdr->prepared_at;
2586 97 : gxact->prepare_start_lsn = start_lsn;
2587 97 : gxact->prepare_end_lsn = end_lsn;
2588 97 : gxact->fxid = fxid;
2589 97 : gxact->owner = hdr->owner;
2590 97 : gxact->locking_backend = INVALID_PROC_NUMBER;
2591 97 : gxact->valid = false;
2592 97 : gxact->ondisk = !XLogRecPtrIsValid(start_lsn);
2593 97 : gxact->inredo = true; /* yes, added in redo */
2594 97 : strcpy(gxact->gid, gid);
2595 :
2596 : /* And insert it into the active array */
2597 : Assert(TwoPhaseState->numPrepXacts < max_prepared_xacts);
2598 97 : TwoPhaseState->prepXacts[TwoPhaseState->numPrepXacts++] = gxact;
2599 :
2600 97 : if (origin_id != InvalidReplOriginId)
2601 : {
2602 : /* recover apply progress */
2603 13 : replorigin_advance(origin_id, hdr->origin_lsn, end_lsn,
2604 : false /* backward */ , false /* WAL */ );
2605 : }
2606 :
2607 97 : elog(DEBUG2, "added 2PC data in shared memory for transaction %u of epoch %u",
2608 : XidFromFullTransactionId(gxact->fxid),
2609 : EpochFromFullTransactionId(gxact->fxid));
2610 : }
2611 :
2612 : /*
2613 : * PrepareRedoRemoveFull
2614 : *
2615 : * Remove the corresponding gxact entry from TwoPhaseState. Also remove
2616 : * the 2PC file if a prepared transaction was saved via an earlier checkpoint.
2617 : *
2618 : * Caller must hold TwoPhaseStateLock in exclusive mode, because TwoPhaseState
2619 : * is updated.
2620 : */
2621 : static void
2622 71 : PrepareRedoRemoveFull(FullTransactionId fxid, bool giveWarning)
2623 : {
2624 71 : GlobalTransaction gxact = NULL;
2625 : int i;
2626 71 : bool found = false;
2627 :
2628 : Assert(LWLockHeldByMeInMode(TwoPhaseStateLock, LW_EXCLUSIVE));
2629 : Assert(RecoveryInProgress());
2630 :
2631 71 : for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
2632 : {
2633 62 : gxact = TwoPhaseState->prepXacts[i];
2634 :
2635 62 : if (FullTransactionIdEquals(gxact->fxid, fxid))
2636 : {
2637 : Assert(gxact->inredo);
2638 62 : found = true;
2639 62 : break;
2640 : }
2641 : }
2642 :
2643 : /*
2644 : * Just leave if there is nothing, this is expected during WAL replay.
2645 : */
2646 71 : if (!found)
2647 9 : return;
2648 :
2649 : /*
2650 : * And now we can clean up any files we may have left.
2651 : */
2652 62 : elog(DEBUG2, "removing 2PC data for transaction %u of epoch %u ",
2653 : XidFromFullTransactionId(fxid),
2654 : EpochFromFullTransactionId(fxid));
2655 :
2656 62 : if (gxact->ondisk)
2657 5 : RemoveTwoPhaseFile(fxid, giveWarning);
2658 :
2659 62 : RemoveGXact(gxact);
2660 : }
2661 :
2662 : /*
2663 : * Wrapper of PrepareRedoRemoveFull(), for TransactionIds.
2664 : */
2665 : void
2666 71 : PrepareRedoRemove(TransactionId xid, bool giveWarning)
2667 : {
2668 : FullTransactionId fxid =
2669 71 : FullTransactionIdFromAllowableAt(TransamVariables->nextXid, xid);
2670 :
2671 71 : PrepareRedoRemoveFull(fxid, giveWarning);
2672 71 : }
2673 :
2674 : /*
2675 : * LookupGXact
2676 : * Check if the prepared transaction with the given GID, lsn and timestamp
2677 : * exists.
2678 : *
2679 : * Note that we always compare with the LSN where prepare ends because that is
2680 : * what is stored as origin_lsn in the 2PC file.
2681 : *
2682 : * This function is primarily used to check if the prepared transaction
2683 : * received from the upstream (remote node) already exists. Checking only GID
2684 : * is not sufficient because a different prepared xact with the same GID can
2685 : * exist on the same node. So, we are ensuring to match origin_lsn and
2686 : * origin_timestamp of prepared xact to avoid the possibility of a match of
2687 : * prepared xact from two different nodes.
2688 : */
2689 : bool
2690 5 : LookupGXact(const char *gid, XLogRecPtr prepare_end_lsn,
2691 : TimestampTz origin_prepare_timestamp)
2692 : {
2693 : int i;
2694 5 : bool found = false;
2695 :
2696 5 : LWLockAcquire(TwoPhaseStateLock, LW_SHARED);
2697 5 : for (i = 0; i < TwoPhaseState->numPrepXacts; i++)
2698 : {
2699 5 : GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
2700 :
2701 : /* Ignore not-yet-valid GIDs. */
2702 5 : if (gxact->valid && strcmp(gxact->gid, gid) == 0)
2703 : {
2704 : char *buf;
2705 : TwoPhaseFileHeader *hdr;
2706 :
2707 : /*
2708 : * We are not expecting collisions of GXACTs (same gid) between
2709 : * publisher and subscribers, so we perform all I/O while holding
2710 : * TwoPhaseStateLock for simplicity.
2711 : *
2712 : * To move the I/O out of the lock, we need to ensure that no
2713 : * other backend commits the prepared xact in the meantime. We can
2714 : * do this optimization if we encounter many collisions in GID
2715 : * between publisher and subscriber.
2716 : */
2717 5 : if (gxact->ondisk)
2718 0 : buf = ReadTwoPhaseFile(gxact->fxid, false);
2719 : else
2720 : {
2721 : Assert(gxact->prepare_start_lsn);
2722 5 : XlogReadTwoPhaseData(gxact->prepare_start_lsn, &buf, NULL);
2723 : }
2724 :
2725 5 : hdr = (TwoPhaseFileHeader *) buf;
2726 :
2727 5 : if (hdr->origin_lsn == prepare_end_lsn &&
2728 5 : hdr->origin_timestamp == origin_prepare_timestamp)
2729 : {
2730 5 : found = true;
2731 5 : pfree(buf);
2732 5 : break;
2733 : }
2734 :
2735 0 : pfree(buf);
2736 : }
2737 : }
2738 5 : LWLockRelease(TwoPhaseStateLock);
2739 5 : return found;
2740 : }
2741 :
2742 : /*
2743 : * TwoPhaseTransactionGid
2744 : * Form the prepared transaction GID for two_phase transactions.
2745 : *
2746 : * Return the GID in the supplied buffer.
2747 : */
2748 : void
2749 53 : TwoPhaseTransactionGid(Oid subid, TransactionId xid, char *gid_res, int szgid)
2750 : {
2751 : Assert(OidIsValid(subid));
2752 :
2753 53 : if (!TransactionIdIsValid(xid))
2754 0 : ereport(ERROR,
2755 : (errcode(ERRCODE_PROTOCOL_VIOLATION),
2756 : errmsg_internal("invalid two-phase transaction ID")));
2757 :
2758 53 : snprintf(gid_res, szgid, "pg_gid_%u_%u", subid, xid);
2759 53 : }
2760 :
2761 : /*
2762 : * IsTwoPhaseTransactionGidForSubid
2763 : * Check whether the given GID (as formed by TwoPhaseTransactionGid) is
2764 : * for the specified 'subid'.
2765 : */
2766 : static bool
2767 0 : IsTwoPhaseTransactionGidForSubid(Oid subid, char *gid)
2768 : {
2769 : int ret;
2770 : Oid subid_from_gid;
2771 : TransactionId xid_from_gid;
2772 : char gid_tmp[GIDSIZE];
2773 :
2774 : /* Extract the subid and xid from the given GID */
2775 0 : ret = sscanf(gid, "pg_gid_%u_%u", &subid_from_gid, &xid_from_gid);
2776 :
2777 : /*
2778 : * Check that the given GID has expected format, and at least the subid
2779 : * matches.
2780 : */
2781 0 : if (ret != 2 || subid != subid_from_gid)
2782 0 : return false;
2783 :
2784 : /*
2785 : * Reconstruct a temporary GID based on the subid and xid extracted from
2786 : * the given GID and check whether the temporary GID and the given GID
2787 : * match.
2788 : */
2789 0 : TwoPhaseTransactionGid(subid, xid_from_gid, gid_tmp, sizeof(gid_tmp));
2790 :
2791 0 : return strcmp(gid, gid_tmp) == 0;
2792 : }
2793 :
2794 : /*
2795 : * LookupGXactBySubid
2796 : * Check if the prepared transaction done by apply worker exists.
2797 : */
2798 : bool
2799 1 : LookupGXactBySubid(Oid subid)
2800 : {
2801 1 : bool found = false;
2802 :
2803 1 : LWLockAcquire(TwoPhaseStateLock, LW_SHARED);
2804 1 : for (int i = 0; i < TwoPhaseState->numPrepXacts; i++)
2805 : {
2806 0 : GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
2807 :
2808 : /* Ignore not-yet-valid GIDs. */
2809 0 : if (gxact->valid &&
2810 0 : IsTwoPhaseTransactionGidForSubid(subid, gxact->gid))
2811 : {
2812 0 : found = true;
2813 0 : break;
2814 : }
2815 : }
2816 1 : LWLockRelease(TwoPhaseStateLock);
2817 :
2818 1 : return found;
2819 : }
2820 :
2821 : /*
2822 : * TwoPhaseGetOldestXidInCommit
2823 : * Return the oldest transaction ID from prepared transactions that are
2824 : * currently in the commit critical section.
2825 : *
2826 : * This function only considers transactions in the currently connected
2827 : * database. If no matching transactions are found, it returns
2828 : * InvalidTransactionId.
2829 : */
2830 : TransactionId
2831 7240 : TwoPhaseGetOldestXidInCommit(void)
2832 : {
2833 7240 : TransactionId oldestRunningXid = InvalidTransactionId;
2834 :
2835 7240 : LWLockAcquire(TwoPhaseStateLock, LW_SHARED);
2836 :
2837 14071 : for (int i = 0; i < TwoPhaseState->numPrepXacts; i++)
2838 : {
2839 6831 : GlobalTransaction gxact = TwoPhaseState->prepXacts[i];
2840 : PGPROC *commitproc;
2841 : TransactionId xid;
2842 :
2843 6831 : if (!gxact->valid)
2844 0 : continue;
2845 :
2846 6831 : if (gxact->locking_backend == INVALID_PROC_NUMBER)
2847 0 : continue;
2848 :
2849 : /*
2850 : * Get the backend that is handling the transaction. It's safe to
2851 : * access this backend while holding TwoPhaseStateLock, as the backend
2852 : * can only be destroyed after either removing or unlocking the
2853 : * current global transaction, both of which require an exclusive
2854 : * TwoPhaseStateLock.
2855 : */
2856 6831 : commitproc = GetPGProcByNumber(gxact->locking_backend);
2857 :
2858 6831 : if (MyDatabaseId != commitproc->databaseId)
2859 0 : continue;
2860 :
2861 6831 : if ((commitproc->delayChkptFlags & DELAY_CHKPT_IN_COMMIT) == 0)
2862 0 : continue;
2863 :
2864 6831 : xid = XidFromFullTransactionId(gxact->fxid);
2865 :
2866 6831 : if (!TransactionIdIsValid(oldestRunningXid) ||
2867 0 : TransactionIdPrecedes(xid, oldestRunningXid))
2868 6831 : oldestRunningXid = xid;
2869 : }
2870 :
2871 7240 : LWLockRelease(TwoPhaseStateLock);
2872 :
2873 7240 : return oldestRunningXid;
2874 : }
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