Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * dynahash.c
4 : * dynamic hash tables
5 : *
6 : * dynahash.c supports both local-to-a-backend hash tables and hash tables in
7 : * shared memory. For shared hash tables, it is the caller's responsibility
8 : * to provide appropriate access interlocking. The simplest convention is
9 : * that a single LWLock protects the whole hash table. Searches (HASH_FIND or
10 : * hash_seq_search) need only shared lock, but any update requires exclusive
11 : * lock. For heavily-used shared tables, the single-lock approach creates a
12 : * concurrency bottleneck, so we also support "partitioned" locking wherein
13 : * there are multiple LWLocks guarding distinct subsets of the table. To use
14 : * a hash table in partitioned mode, the HASH_PARTITION flag must be given
15 : * to hash_create. This prevents any attempt to split buckets on-the-fly.
16 : * Therefore, each hash bucket chain operates independently, and no fields
17 : * of the hash header change after init except nentries and freeList.
18 : * (A partitioned table uses multiple copies of those fields, guarded by
19 : * spinlocks, for additional concurrency.)
20 : * This lets any subset of the hash buckets be treated as a separately
21 : * lockable partition. We expect callers to use the low-order bits of a
22 : * lookup key's hash value as a partition number --- this will work because
23 : * of the way calc_bucket() maps hash values to bucket numbers.
24 : *
25 : * For hash tables in shared memory, the memory allocator function should
26 : * match malloc's semantics of returning NULL on failure. For hash tables
27 : * in local memory, we typically use palloc() which will throw error on
28 : * failure. The code in this file has to cope with both cases.
29 : *
30 : * dynahash.c provides support for these types of lookup keys:
31 : *
32 : * 1. Null-terminated C strings (truncated if necessary to fit in keysize),
33 : * compared as though by strcmp(). This is the default behavior.
34 : *
35 : * 2. Arbitrary binary data of size keysize, compared as though by memcmp().
36 : * (Caller must ensure there are no undefined padding bits in the keys!)
37 : * This is selected by specifying HASH_BLOBS flag to hash_create.
38 : *
39 : * 3. More complex key behavior can be selected by specifying user-supplied
40 : * hashing, comparison, and/or key-copying functions. At least a hashing
41 : * function must be supplied; comparison defaults to memcmp() and key copying
42 : * to memcpy() when a user-defined hashing function is selected.
43 : *
44 : * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
45 : * Portions Copyright (c) 1994, Regents of the University of California
46 : *
47 : *
48 : * IDENTIFICATION
49 : * src/backend/utils/hash/dynahash.c
50 : *
51 : *-------------------------------------------------------------------------
52 : */
53 :
54 : /*
55 : * Original comments:
56 : *
57 : * Dynamic hashing, after CACM April 1988 pp 446-457, by Per-Ake Larson.
58 : * Coded into C, with minor code improvements, and with hsearch(3) interface,
59 : * by ejp@ausmelb.oz, Jul 26, 1988: 13:16;
60 : * also, hcreate/hdestroy routines added to simulate hsearch(3).
61 : *
62 : * These routines simulate hsearch(3) and family, with the important
63 : * difference that the hash table is dynamic - can grow indefinitely
64 : * beyond its original size (as supplied to hcreate()).
65 : *
66 : * Performance appears to be comparable to that of hsearch(3).
67 : * The 'source-code' options referred to in hsearch(3)'s 'man' page
68 : * are not implemented; otherwise functionality is identical.
69 : *
70 : * Compilation controls:
71 : * HASH_DEBUG controls some informative traces, mainly for debugging.
72 : * HASH_STATISTICS causes HashAccesses and HashCollisions to be maintained;
73 : * when combined with HASH_DEBUG, these are displayed by hdestroy().
74 : *
75 : * Problems & fixes to ejp@ausmelb.oz. WARNING: relies on pre-processor
76 : * concatenation property, in probably unnecessary code 'optimization'.
77 : *
78 : * Modified margo@postgres.berkeley.edu February 1990
79 : * added multiple table interface
80 : * Modified by sullivan@postgres.berkeley.edu April 1990
81 : * changed ctl structure for shared memory
82 : */
83 :
84 : #include "postgres.h"
85 :
86 : #include <limits.h>
87 :
88 : #include "access/xact.h"
89 : #include "storage/shmem.h"
90 : #include "storage/spin.h"
91 : #include "utils/dynahash.h"
92 : #include "utils/memutils.h"
93 :
94 :
95 : /*
96 : * Constants
97 : *
98 : * A hash table has a top-level "directory", each of whose entries points
99 : * to a "segment" of ssize bucket headers. The maximum number of hash
100 : * buckets is thus dsize * ssize (but dsize may be expansible). Of course,
101 : * the number of records in the table can be larger, but we don't want a
102 : * whole lot of records per bucket or performance goes down.
103 : *
104 : * In a hash table allocated in shared memory, the directory cannot be
105 : * expanded because it must stay at a fixed address. The directory size
106 : * should be selected using hash_select_dirsize (and you'd better have
107 : * a good idea of the maximum number of entries!). For non-shared hash
108 : * tables, the initial directory size can be left at the default.
109 : */
110 : #define DEF_SEGSIZE 256
111 : #define DEF_SEGSIZE_SHIFT 8 /* must be log2(DEF_SEGSIZE) */
112 : #define DEF_DIRSIZE 256
113 : #define DEF_FFACTOR 1 /* default fill factor */
114 :
115 : /* Number of freelists to be used for a partitioned hash table. */
116 : #define NUM_FREELISTS 32
117 :
118 : /* A hash bucket is a linked list of HASHELEMENTs */
119 : typedef HASHELEMENT *HASHBUCKET;
120 :
121 : /* A hash segment is an array of bucket headers */
122 : typedef HASHBUCKET *HASHSEGMENT;
123 :
124 : /*
125 : * Per-freelist data.
126 : *
127 : * In a partitioned hash table, each freelist is associated with a specific
128 : * set of hashcodes, as determined by the FREELIST_IDX() macro below.
129 : * nentries tracks the number of live hashtable entries having those hashcodes
130 : * (NOT the number of entries in the freelist, as you might expect).
131 : *
132 : * The coverage of a freelist might be more or less than one partition, so it
133 : * needs its own lock rather than relying on caller locking. Relying on that
134 : * wouldn't work even if the coverage was the same, because of the occasional
135 : * need to "borrow" entries from another freelist; see get_hash_entry().
136 : *
137 : * Using an array of FreeListData instead of separate arrays of mutexes,
138 : * nentries and freeLists helps to reduce sharing of cache lines between
139 : * different mutexes.
140 : */
141 : typedef struct
142 : {
143 : slock_t mutex; /* spinlock for this freelist */
144 : long nentries; /* number of entries in associated buckets */
145 : HASHELEMENT *freeList; /* chain of free elements */
146 : } FreeListData;
147 :
148 : /*
149 : * Header structure for a hash table --- contains all changeable info
150 : *
151 : * In a shared-memory hash table, the HASHHDR is in shared memory, while
152 : * each backend has a local HTAB struct. For a non-shared table, there isn't
153 : * any functional difference between HASHHDR and HTAB, but we separate them
154 : * anyway to share code between shared and non-shared tables.
155 : */
156 : struct HASHHDR
157 : {
158 : /*
159 : * The freelist can become a point of contention in high-concurrency hash
160 : * tables, so we use an array of freelists, each with its own mutex and
161 : * nentries count, instead of just a single one. Although the freelists
162 : * normally operate independently, we will scavenge entries from freelists
163 : * other than a hashcode's default freelist when necessary.
164 : *
165 : * If the hash table is not partitioned, only freeList[0] is used and its
166 : * spinlock is not used at all; callers' locking is assumed sufficient.
167 : */
168 : FreeListData freeList[NUM_FREELISTS];
169 :
170 : /* These fields can change, but not in a partitioned table */
171 : /* Also, dsize can't change in a shared table, even if unpartitioned */
172 : long dsize; /* directory size */
173 : long nsegs; /* number of allocated segments (<= dsize) */
174 : uint32 max_bucket; /* ID of maximum bucket in use */
175 : uint32 high_mask; /* mask to modulo into entire table */
176 : uint32 low_mask; /* mask to modulo into lower half of table */
177 :
178 : /* These fields are fixed at hashtable creation */
179 : Size keysize; /* hash key length in bytes */
180 : Size entrysize; /* total user element size in bytes */
181 : long num_partitions; /* # partitions (must be power of 2), or 0 */
182 : long ffactor; /* target fill factor */
183 : long max_dsize; /* 'dsize' limit if directory is fixed size */
184 : long ssize; /* segment size --- must be power of 2 */
185 : int sshift; /* segment shift = log2(ssize) */
186 : int nelem_alloc; /* number of entries to allocate at once */
187 :
188 : #ifdef HASH_STATISTICS
189 :
190 : /*
191 : * Count statistics here. NB: stats code doesn't bother with mutex, so
192 : * counts could be corrupted a bit in a partitioned table.
193 : */
194 : long accesses;
195 : long collisions;
196 : #endif
197 : };
198 :
199 : #define IS_PARTITIONED(hctl) ((hctl)->num_partitions != 0)
200 :
201 : #define FREELIST_IDX(hctl, hashcode) \
202 : (IS_PARTITIONED(hctl) ? (hashcode) % NUM_FREELISTS : 0)
203 :
204 : /*
205 : * Top control structure for a hashtable --- in a shared table, each backend
206 : * has its own copy (OK since no fields change at runtime)
207 : */
208 : struct HTAB
209 : {
210 : HASHHDR *hctl; /* => shared control information */
211 : HASHSEGMENT *dir; /* directory of segment starts */
212 : HashValueFunc hash; /* hash function */
213 : HashCompareFunc match; /* key comparison function */
214 : HashCopyFunc keycopy; /* key copying function */
215 : HashAllocFunc alloc; /* memory allocator */
216 : MemoryContext hcxt; /* memory context if default allocator used */
217 : char *tabname; /* table name (for error messages) */
218 : bool isshared; /* true if table is in shared memory */
219 : bool isfixed; /* if true, don't enlarge */
220 :
221 : /* freezing a shared table isn't allowed, so we can keep state here */
222 : bool frozen; /* true = no more inserts allowed */
223 :
224 : /* We keep local copies of these fixed values to reduce contention */
225 : Size keysize; /* hash key length in bytes */
226 : long ssize; /* segment size --- must be power of 2 */
227 : int sshift; /* segment shift = log2(ssize) */
228 : };
229 :
230 : /*
231 : * Key (also entry) part of a HASHELEMENT
232 : */
233 : #define ELEMENTKEY(helem) (((char *)(helem)) + MAXALIGN(sizeof(HASHELEMENT)))
234 :
235 : /*
236 : * Obtain element pointer given pointer to key
237 : */
238 : #define ELEMENT_FROM_KEY(key) \
239 : ((HASHELEMENT *) (((char *) (key)) - MAXALIGN(sizeof(HASHELEMENT))))
240 :
241 : /*
242 : * Fast MOD arithmetic, assuming that y is a power of 2 !
243 : */
244 : #define MOD(x,y) ((x) & ((y)-1))
245 :
246 : #if HASH_STATISTICS
247 : static long hash_accesses,
248 : hash_collisions,
249 : hash_expansions;
250 : #endif
251 :
252 : /*
253 : * Private function prototypes
254 : */
255 : static void *DynaHashAlloc(Size size);
256 : static HASHSEGMENT seg_alloc(HTAB *hashp);
257 : static bool element_alloc(HTAB *hashp, int nelem, int freelist_idx);
258 : static bool dir_realloc(HTAB *hashp);
259 : static bool expand_table(HTAB *hashp);
260 : static HASHBUCKET get_hash_entry(HTAB *hashp, int freelist_idx);
261 : static void hdefault(HTAB *hashp);
262 : static int choose_nelem_alloc(Size entrysize);
263 : static bool init_htab(HTAB *hashp, long nelem);
264 : static void hash_corrupted(HTAB *hashp);
265 : static long next_pow2_long(long num);
266 : static int next_pow2_int(long num);
267 : static void register_seq_scan(HTAB *hashp);
268 : static void deregister_seq_scan(HTAB *hashp);
269 : static bool has_seq_scans(HTAB *hashp);
270 :
271 :
272 : /*
273 : * memory allocation support
274 : */
275 : static MemoryContext CurrentDynaHashCxt = NULL;
276 :
277 : static void *
278 1318716 : DynaHashAlloc(Size size)
279 : {
280 : Assert(MemoryContextIsValid(CurrentDynaHashCxt));
281 1318716 : return MemoryContextAlloc(CurrentDynaHashCxt, size);
282 : }
283 :
284 :
285 : /*
286 : * HashCompareFunc for string keys
287 : *
288 : * Because we copy keys with strlcpy(), they will be truncated at keysize-1
289 : * bytes, so we can only compare that many ... hence strncmp is almost but
290 : * not quite the right thing.
291 : */
292 : static int
293 636154 : string_compare(const char *key1, const char *key2, Size keysize)
294 : {
295 636154 : return strncmp(key1, key2, keysize - 1);
296 : }
297 :
298 :
299 : /************************** CREATE ROUTINES **********************/
300 :
301 : /*
302 : * hash_create -- create a new dynamic hash table
303 : *
304 : * tabname: a name for the table (for debugging purposes)
305 : * nelem: maximum number of elements expected
306 : * *info: additional table parameters, as indicated by flags
307 : * flags: bitmask indicating which parameters to take from *info
308 : *
309 : * Note: for a shared-memory hashtable, nelem needs to be a pretty good
310 : * estimate, since we can't expand the table on the fly. But an unshared
311 : * hashtable can be expanded on-the-fly, so it's better for nelem to be
312 : * on the small side and let the table grow if it's exceeded. An overly
313 : * large nelem will penalize hash_seq_search speed without buying much.
314 : */
315 : HTAB *
316 244930 : hash_create(const char *tabname, long nelem, HASHCTL *info, int flags)
317 : {
318 : HTAB *hashp;
319 : HASHHDR *hctl;
320 :
321 : /*
322 : * For shared hash tables, we have a local hash header (HTAB struct) that
323 : * we allocate in TopMemoryContext; all else is in shared memory.
324 : *
325 : * For non-shared hash tables, everything including the hash header is in
326 : * a memory context created specially for the hash table --- this makes
327 : * hash_destroy very simple. The memory context is made a child of either
328 : * a context specified by the caller, or TopMemoryContext if nothing is
329 : * specified.
330 : */
331 244930 : if (flags & HASH_SHARED_MEM)
332 : {
333 : /* Set up to allocate the hash header */
334 12994 : CurrentDynaHashCxt = TopMemoryContext;
335 : }
336 : else
337 : {
338 : /* Create the hash table's private memory context */
339 231936 : if (flags & HASH_CONTEXT)
340 135574 : CurrentDynaHashCxt = info->hcxt;
341 : else
342 96362 : CurrentDynaHashCxt = TopMemoryContext;
343 231936 : CurrentDynaHashCxt = AllocSetContextCreate(CurrentDynaHashCxt,
344 : "dynahash",
345 : ALLOCSET_DEFAULT_SIZES);
346 : }
347 :
348 : /* Initialize the hash header, plus a copy of the table name */
349 244930 : hashp = (HTAB *) DynaHashAlloc(sizeof(HTAB) + strlen(tabname) + 1);
350 244930 : MemSet(hashp, 0, sizeof(HTAB));
351 :
352 244930 : hashp->tabname = (char *) (hashp + 1);
353 244930 : strcpy(hashp->tabname, tabname);
354 :
355 : /* If we have a private context, label it with hashtable's name */
356 244930 : if (!(flags & HASH_SHARED_MEM))
357 231936 : MemoryContextSetIdentifier(CurrentDynaHashCxt, hashp->tabname);
358 :
359 : /*
360 : * Select the appropriate hash function (see comments at head of file).
361 : */
362 244930 : if (flags & HASH_FUNCTION)
363 12242 : hashp->hash = info->hash;
364 232688 : else if (flags & HASH_BLOBS)
365 : {
366 : /* We can optimize hashing for common key sizes */
367 : Assert(flags & HASH_ELEM);
368 193648 : if (info->keysize == sizeof(uint32))
369 103906 : hashp->hash = uint32_hash;
370 : else
371 89742 : hashp->hash = tag_hash;
372 : }
373 : else
374 39040 : hashp->hash = string_hash; /* default hash function */
375 :
376 : /*
377 : * If you don't specify a match function, it defaults to string_compare if
378 : * you used string_hash (either explicitly or by default) and to memcmp
379 : * otherwise.
380 : *
381 : * Note: explicitly specifying string_hash is deprecated, because this
382 : * might not work for callers in loadable modules on some platforms due to
383 : * referencing a trampoline instead of the string_hash function proper.
384 : * Just let it default, eh?
385 : */
386 244930 : if (flags & HASH_COMPARE)
387 8530 : hashp->match = info->match;
388 236400 : else if (hashp->hash == string_hash)
389 39040 : hashp->match = (HashCompareFunc) string_compare;
390 : else
391 197360 : hashp->match = memcmp;
392 :
393 : /*
394 : * Similarly, the key-copying function defaults to strlcpy or memcpy.
395 : */
396 244930 : if (flags & HASH_KEYCOPY)
397 0 : hashp->keycopy = info->keycopy;
398 244930 : else if (hashp->hash == string_hash)
399 39040 : hashp->keycopy = (HashCopyFunc) strlcpy;
400 : else
401 205890 : hashp->keycopy = memcpy;
402 :
403 : /* And select the entry allocation function, too. */
404 244930 : if (flags & HASH_ALLOC)
405 12994 : hashp->alloc = info->alloc;
406 : else
407 231936 : hashp->alloc = DynaHashAlloc;
408 :
409 244930 : if (flags & HASH_SHARED_MEM)
410 : {
411 : /*
412 : * ctl structure and directory are preallocated for shared memory
413 : * tables. Note that HASH_DIRSIZE and HASH_ALLOC had better be set as
414 : * well.
415 : */
416 12994 : hashp->hctl = info->hctl;
417 12994 : hashp->dir = (HASHSEGMENT *) (((char *) info->hctl) + sizeof(HASHHDR));
418 12994 : hashp->hcxt = NULL;
419 12994 : hashp->isshared = true;
420 :
421 : /* hash table already exists, we're just attaching to it */
422 12994 : if (flags & HASH_ATTACH)
423 : {
424 : /* make local copies of some heavily-used values */
425 0 : hctl = hashp->hctl;
426 0 : hashp->keysize = hctl->keysize;
427 0 : hashp->ssize = hctl->ssize;
428 0 : hashp->sshift = hctl->sshift;
429 :
430 0 : return hashp;
431 : }
432 : }
433 : else
434 : {
435 : /* setup hash table defaults */
436 231936 : hashp->hctl = NULL;
437 231936 : hashp->dir = NULL;
438 231936 : hashp->hcxt = CurrentDynaHashCxt;
439 231936 : hashp->isshared = false;
440 : }
441 :
442 244930 : if (!hashp->hctl)
443 : {
444 231936 : hashp->hctl = (HASHHDR *) hashp->alloc(sizeof(HASHHDR));
445 231936 : if (!hashp->hctl)
446 0 : ereport(ERROR,
447 : (errcode(ERRCODE_OUT_OF_MEMORY),
448 : errmsg("out of memory")));
449 : }
450 :
451 244930 : hashp->frozen = false;
452 :
453 244930 : hdefault(hashp);
454 :
455 244930 : hctl = hashp->hctl;
456 :
457 244930 : if (flags & HASH_PARTITION)
458 : {
459 : /* Doesn't make sense to partition a local hash table */
460 : Assert(flags & HASH_SHARED_MEM);
461 :
462 : /*
463 : * The number of partitions had better be a power of 2. Also, it must
464 : * be less than INT_MAX (see init_htab()), so call the int version of
465 : * next_pow2.
466 : */
467 : Assert(info->num_partitions == next_pow2_int(info->num_partitions));
468 :
469 9280 : hctl->num_partitions = info->num_partitions;
470 : }
471 :
472 244930 : if (flags & HASH_SEGMENT)
473 : {
474 0 : hctl->ssize = info->ssize;
475 0 : hctl->sshift = my_log2(info->ssize);
476 : /* ssize had better be a power of 2 */
477 : Assert(hctl->ssize == (1L << hctl->sshift));
478 : }
479 244930 : if (flags & HASH_FFACTOR)
480 0 : hctl->ffactor = info->ffactor;
481 :
482 : /*
483 : * SHM hash tables have fixed directory size passed by the caller.
484 : */
485 244930 : if (flags & HASH_DIRSIZE)
486 : {
487 12994 : hctl->max_dsize = info->max_dsize;
488 12994 : hctl->dsize = info->dsize;
489 : }
490 :
491 : /*
492 : * hash table now allocates space for key and data but you have to say how
493 : * much space to allocate
494 : */
495 244930 : if (flags & HASH_ELEM)
496 : {
497 : Assert(info->entrysize >= info->keysize);
498 244930 : hctl->keysize = info->keysize;
499 244930 : hctl->entrysize = info->entrysize;
500 : }
501 :
502 : /* make local copies of heavily-used constant fields */
503 244930 : hashp->keysize = hctl->keysize;
504 244930 : hashp->ssize = hctl->ssize;
505 244930 : hashp->sshift = hctl->sshift;
506 :
507 : /* Build the hash directory structure */
508 244930 : if (!init_htab(hashp, nelem))
509 0 : elog(ERROR, "failed to initialize hash table \"%s\"", hashp->tabname);
510 :
511 : /*
512 : * For a shared hash table, preallocate the requested number of elements.
513 : * This reduces problems with run-time out-of-shared-memory conditions.
514 : *
515 : * For a non-shared hash table, preallocate the requested number of
516 : * elements if it's less than our chosen nelem_alloc. This avoids wasting
517 : * space if the caller correctly estimates a small table size.
518 : */
519 476866 : if ((flags & HASH_SHARED_MEM) ||
520 231936 : nelem < hctl->nelem_alloc)
521 : {
522 : int i,
523 : freelist_partitions,
524 : nelem_alloc,
525 : nelem_alloc_first;
526 :
527 : /*
528 : * If hash table is partitioned, give each freelist an equal share of
529 : * the initial allocation. Otherwise only freeList[0] is used.
530 : */
531 68182 : if (IS_PARTITIONED(hashp->hctl))
532 9280 : freelist_partitions = NUM_FREELISTS;
533 : else
534 58902 : freelist_partitions = 1;
535 :
536 68182 : nelem_alloc = nelem / freelist_partitions;
537 68182 : if (nelem_alloc <= 0)
538 0 : nelem_alloc = 1;
539 :
540 : /*
541 : * Make sure we'll allocate all the requested elements; freeList[0]
542 : * gets the excess if the request isn't divisible by NUM_FREELISTS.
543 : */
544 68182 : if (nelem_alloc * freelist_partitions < nelem)
545 324 : nelem_alloc_first =
546 324 : nelem - nelem_alloc * (freelist_partitions - 1);
547 : else
548 67858 : nelem_alloc_first = nelem_alloc;
549 :
550 424044 : for (i = 0; i < freelist_partitions; i++)
551 : {
552 355862 : int temp = (i == 0) ? nelem_alloc_first : nelem_alloc;
553 :
554 355862 : if (!element_alloc(hashp, temp, i))
555 0 : ereport(ERROR,
556 : (errcode(ERRCODE_OUT_OF_MEMORY),
557 : errmsg("out of memory")));
558 : }
559 : }
560 :
561 244930 : if (flags & HASH_FIXED_SIZE)
562 5568 : hashp->isfixed = true;
563 244930 : return hashp;
564 : }
565 :
566 : /*
567 : * Set default HASHHDR parameters.
568 : */
569 : static void
570 244930 : hdefault(HTAB *hashp)
571 : {
572 244930 : HASHHDR *hctl = hashp->hctl;
573 :
574 244930 : MemSet(hctl, 0, sizeof(HASHHDR));
575 :
576 244930 : hctl->dsize = DEF_DIRSIZE;
577 244930 : hctl->nsegs = 0;
578 :
579 : /* rather pointless defaults for key & entry size */
580 244930 : hctl->keysize = sizeof(char *);
581 244930 : hctl->entrysize = 2 * sizeof(char *);
582 :
583 244930 : hctl->num_partitions = 0; /* not partitioned */
584 :
585 244930 : hctl->ffactor = DEF_FFACTOR;
586 :
587 : /* table has no fixed maximum size */
588 244930 : hctl->max_dsize = NO_MAX_DSIZE;
589 :
590 244930 : hctl->ssize = DEF_SEGSIZE;
591 244930 : hctl->sshift = DEF_SEGSIZE_SHIFT;
592 :
593 : #ifdef HASH_STATISTICS
594 : hctl->accesses = hctl->collisions = 0;
595 : #endif
596 244930 : }
597 :
598 : /*
599 : * Given the user-specified entry size, choose nelem_alloc, ie, how many
600 : * elements to add to the hash table when we need more.
601 : */
602 : static int
603 257952 : choose_nelem_alloc(Size entrysize)
604 : {
605 : int nelem_alloc;
606 : Size elementSize;
607 : Size allocSize;
608 :
609 : /* Each element has a HASHELEMENT header plus user data. */
610 : /* NB: this had better match element_alloc() */
611 257952 : elementSize = MAXALIGN(sizeof(HASHELEMENT)) + MAXALIGN(entrysize);
612 :
613 : /*
614 : * The idea here is to choose nelem_alloc at least 32, but round up so
615 : * that the allocation request will be a power of 2 or just less. This
616 : * makes little difference for hash tables in shared memory, but for hash
617 : * tables managed by palloc, the allocation request will be rounded up to
618 : * a power of 2 anyway. If we fail to take this into account, we'll waste
619 : * as much as half the allocated space.
620 : */
621 257952 : allocSize = 32 * 4; /* assume elementSize at least 8 */
622 : do
623 : {
624 1029778 : allocSize <<= 1;
625 1029778 : nelem_alloc = allocSize / elementSize;
626 1029778 : } while (nelem_alloc < 32);
627 :
628 257952 : return nelem_alloc;
629 : }
630 :
631 : /*
632 : * Compute derived fields of hctl and build the initial directory/segment
633 : * arrays
634 : */
635 : static bool
636 244930 : init_htab(HTAB *hashp, long nelem)
637 : {
638 244930 : HASHHDR *hctl = hashp->hctl;
639 : HASHSEGMENT *segp;
640 : int nbuckets;
641 : int nsegs;
642 : int i;
643 :
644 : /*
645 : * initialize mutexes if it's a partitioned table
646 : */
647 244930 : if (IS_PARTITIONED(hctl))
648 306240 : for (i = 0; i < NUM_FREELISTS; i++)
649 296960 : SpinLockInit(&(hctl->freeList[i].mutex));
650 :
651 : /*
652 : * Divide number of elements by the fill factor to determine a desired
653 : * number of buckets. Allocate space for the next greater power of two
654 : * number of buckets
655 : */
656 244930 : nbuckets = next_pow2_int((nelem - 1) / hctl->ffactor + 1);
657 :
658 : /*
659 : * In a partitioned table, nbuckets must be at least equal to
660 : * num_partitions; were it less, keys with apparently different partition
661 : * numbers would map to the same bucket, breaking partition independence.
662 : * (Normally nbuckets will be much bigger; this is just a safety check.)
663 : */
664 489860 : while (nbuckets < hctl->num_partitions)
665 0 : nbuckets <<= 1;
666 :
667 244930 : hctl->max_bucket = hctl->low_mask = nbuckets - 1;
668 244930 : hctl->high_mask = (nbuckets << 1) - 1;
669 :
670 : /*
671 : * Figure number of directory segments needed, round up to a power of 2
672 : */
673 244930 : nsegs = (nbuckets - 1) / hctl->ssize + 1;
674 244930 : nsegs = next_pow2_int(nsegs);
675 :
676 : /*
677 : * Make sure directory is big enough. If pre-allocated directory is too
678 : * small, choke (caller screwed up).
679 : */
680 244930 : if (nsegs > hctl->dsize)
681 : {
682 0 : if (!(hashp->dir))
683 0 : hctl->dsize = nsegs;
684 : else
685 0 : return false;
686 : }
687 :
688 : /* Allocate a directory */
689 244930 : if (!(hashp->dir))
690 : {
691 231936 : CurrentDynaHashCxt = hashp->hcxt;
692 231936 : hashp->dir = (HASHSEGMENT *)
693 231936 : hashp->alloc(hctl->dsize * sizeof(HASHSEGMENT));
694 231936 : if (!hashp->dir)
695 0 : return false;
696 : }
697 :
698 : /* Allocate initial segments */
699 954542 : for (segp = hashp->dir; hctl->nsegs < nsegs; hctl->nsegs++, segp++)
700 : {
701 709612 : *segp = seg_alloc(hashp);
702 709612 : if (*segp == NULL)
703 0 : return false;
704 : }
705 :
706 : /* Choose number of entries to allocate at a time */
707 244930 : hctl->nelem_alloc = choose_nelem_alloc(hctl->entrysize);
708 :
709 : #if HASH_DEBUG
710 : fprintf(stderr, "init_htab:\n%s%p\n%s%ld\n%s%ld\n%s%d\n%s%ld\n%s%u\n%s%x\n%s%x\n%s%ld\n",
711 : "TABLE POINTER ", hashp,
712 : "DIRECTORY SIZE ", hctl->dsize,
713 : "SEGMENT SIZE ", hctl->ssize,
714 : "SEGMENT SHIFT ", hctl->sshift,
715 : "FILL FACTOR ", hctl->ffactor,
716 : "MAX BUCKET ", hctl->max_bucket,
717 : "HIGH MASK ", hctl->high_mask,
718 : "LOW MASK ", hctl->low_mask,
719 : "NSEGS ", hctl->nsegs);
720 : #endif
721 244930 : return true;
722 : }
723 :
724 : /*
725 : * Estimate the space needed for a hashtable containing the given number
726 : * of entries of given size.
727 : * NOTE: this is used to estimate the footprint of hashtables in shared
728 : * memory; therefore it does not count HTAB which is in local memory.
729 : * NB: assumes that all hash structure parameters have default values!
730 : */
731 : Size
732 13022 : hash_estimate_size(long num_entries, Size entrysize)
733 : {
734 : Size size;
735 : long nBuckets,
736 : nSegments,
737 : nDirEntries,
738 : nElementAllocs,
739 : elementSize,
740 : elementAllocCnt;
741 :
742 : /* estimate number of buckets wanted */
743 13022 : nBuckets = next_pow2_long((num_entries - 1) / DEF_FFACTOR + 1);
744 : /* # of segments needed for nBuckets */
745 13022 : nSegments = next_pow2_long((nBuckets - 1) / DEF_SEGSIZE + 1);
746 : /* directory entries */
747 13022 : nDirEntries = DEF_DIRSIZE;
748 26044 : while (nDirEntries < nSegments)
749 0 : nDirEntries <<= 1; /* dir_alloc doubles dsize at each call */
750 :
751 : /* fixed control info */
752 13022 : size = MAXALIGN(sizeof(HASHHDR)); /* but not HTAB, per above */
753 : /* directory */
754 13022 : size = add_size(size, mul_size(nDirEntries, sizeof(HASHSEGMENT)));
755 : /* segments */
756 13022 : size = add_size(size, mul_size(nSegments,
757 : MAXALIGN(DEF_SEGSIZE * sizeof(HASHBUCKET))));
758 : /* elements --- allocated in groups of choose_nelem_alloc() entries */
759 13022 : elementAllocCnt = choose_nelem_alloc(entrysize);
760 13022 : nElementAllocs = (num_entries - 1) / elementAllocCnt + 1;
761 13022 : elementSize = MAXALIGN(sizeof(HASHELEMENT)) + MAXALIGN(entrysize);
762 13022 : size = add_size(size,
763 : mul_size(nElementAllocs,
764 : mul_size(elementAllocCnt, elementSize)));
765 :
766 13022 : return size;
767 : }
768 :
769 : /*
770 : * Select an appropriate directory size for a hashtable with the given
771 : * maximum number of entries.
772 : * This is only needed for hashtables in shared memory, whose directories
773 : * cannot be expanded dynamically.
774 : * NB: assumes that all hash structure parameters have default values!
775 : *
776 : * XXX this had better agree with the behavior of init_htab()...
777 : */
778 : long
779 12994 : hash_select_dirsize(long num_entries)
780 : {
781 : long nBuckets,
782 : nSegments,
783 : nDirEntries;
784 :
785 : /* estimate number of buckets wanted */
786 12994 : nBuckets = next_pow2_long((num_entries - 1) / DEF_FFACTOR + 1);
787 : /* # of segments needed for nBuckets */
788 12994 : nSegments = next_pow2_long((nBuckets - 1) / DEF_SEGSIZE + 1);
789 : /* directory entries */
790 12994 : nDirEntries = DEF_DIRSIZE;
791 25988 : while (nDirEntries < nSegments)
792 0 : nDirEntries <<= 1; /* dir_alloc doubles dsize at each call */
793 :
794 12994 : return nDirEntries;
795 : }
796 :
797 : /*
798 : * Compute the required initial memory allocation for a shared-memory
799 : * hashtable with the given parameters. We need space for the HASHHDR
800 : * and for the (non expansible) directory.
801 : */
802 : Size
803 12994 : hash_get_shared_size(HASHCTL *info, int flags)
804 : {
805 : Assert(flags & HASH_DIRSIZE);
806 : Assert(info->dsize == info->max_dsize);
807 12994 : return sizeof(HASHHDR) + info->dsize * sizeof(HASHSEGMENT);
808 : }
809 :
810 :
811 : /********************** DESTROY ROUTINES ************************/
812 :
813 : void
814 53220 : hash_destroy(HTAB *hashp)
815 : {
816 53220 : if (hashp != NULL)
817 : {
818 : /* allocation method must be one we know how to free, too */
819 : Assert(hashp->alloc == DynaHashAlloc);
820 : /* so this hashtable must have its own context */
821 : Assert(hashp->hcxt != NULL);
822 :
823 53220 : hash_stats("destroy", hashp);
824 :
825 : /*
826 : * Free everything by destroying the hash table's memory context.
827 : */
828 53220 : MemoryContextDelete(hashp->hcxt);
829 : }
830 53220 : }
831 :
832 : void
833 53220 : hash_stats(const char *where, HTAB *hashp)
834 : {
835 : #if HASH_STATISTICS
836 : fprintf(stderr, "%s: this HTAB -- accesses %ld collisions %ld\n",
837 : where, hashp->hctl->accesses, hashp->hctl->collisions);
838 :
839 : fprintf(stderr, "hash_stats: entries %ld keysize %ld maxp %u segmentcount %ld\n",
840 : hash_get_num_entries(hashp), (long) hashp->hctl->keysize,
841 : hashp->hctl->max_bucket, hashp->hctl->nsegs);
842 : fprintf(stderr, "%s: total accesses %ld total collisions %ld\n",
843 : where, hash_accesses, hash_collisions);
844 : fprintf(stderr, "hash_stats: total expansions %ld\n",
845 : hash_expansions);
846 : #endif
847 53220 : }
848 :
849 : /*******************************SEARCH ROUTINES *****************************/
850 :
851 :
852 : /*
853 : * get_hash_value -- exported routine to calculate a key's hash value
854 : *
855 : * We export this because for partitioned tables, callers need to compute
856 : * the partition number (from the low-order bits of the hash value) before
857 : * searching.
858 : */
859 : uint32
860 105637772 : get_hash_value(HTAB *hashp, const void *keyPtr)
861 : {
862 105637772 : return hashp->hash(keyPtr, hashp->keysize);
863 : }
864 :
865 : /* Convert a hash value to a bucket number */
866 : static inline uint32
867 217716682 : calc_bucket(HASHHDR *hctl, uint32 hash_val)
868 : {
869 : uint32 bucket;
870 :
871 217716682 : bucket = hash_val & hctl->high_mask;
872 217716682 : if (bucket > hctl->max_bucket)
873 90287234 : bucket = bucket & hctl->low_mask;
874 :
875 217716682 : return bucket;
876 : }
877 :
878 : /*
879 : * hash_search -- look up key in table and perform action
880 : * hash_search_with_hash_value -- same, with key's hash value already computed
881 : *
882 : * action is one of:
883 : * HASH_FIND: look up key in table
884 : * HASH_ENTER: look up key in table, creating entry if not present
885 : * HASH_ENTER_NULL: same, but return NULL if out of memory
886 : * HASH_REMOVE: look up key in table, remove entry if present
887 : *
888 : * Return value is a pointer to the element found/entered/removed if any,
889 : * or NULL if no match was found. (NB: in the case of the REMOVE action,
890 : * the result is a dangling pointer that shouldn't be dereferenced!)
891 : *
892 : * HASH_ENTER will normally ereport a generic "out of memory" error if
893 : * it is unable to create a new entry. The HASH_ENTER_NULL operation is
894 : * the same except it will return NULL if out of memory. Note that
895 : * HASH_ENTER_NULL cannot be used with the default palloc-based allocator,
896 : * since palloc internally ereports on out-of-memory.
897 : *
898 : * If foundPtr isn't NULL, then *foundPtr is set true if we found an
899 : * existing entry in the table, false otherwise. This is needed in the
900 : * HASH_ENTER case, but is redundant with the return value otherwise.
901 : *
902 : * For hash_search_with_hash_value, the hashvalue parameter must have been
903 : * calculated with get_hash_value().
904 : */
905 : void *
906 125982132 : hash_search(HTAB *hashp,
907 : const void *keyPtr,
908 : HASHACTION action,
909 : bool *foundPtr)
910 : {
911 125982132 : return hash_search_with_hash_value(hashp,
912 : keyPtr,
913 125982132 : hashp->hash(keyPtr, hashp->keysize),
914 : action,
915 : foundPtr);
916 : }
917 :
918 : void *
919 216762508 : hash_search_with_hash_value(HTAB *hashp,
920 : const void *keyPtr,
921 : uint32 hashvalue,
922 : HASHACTION action,
923 : bool *foundPtr)
924 : {
925 216762508 : HASHHDR *hctl = hashp->hctl;
926 216762508 : int freelist_idx = FREELIST_IDX(hctl, hashvalue);
927 : Size keysize;
928 : uint32 bucket;
929 : long segment_num;
930 : long segment_ndx;
931 : HASHSEGMENT segp;
932 : HASHBUCKET currBucket;
933 : HASHBUCKET *prevBucketPtr;
934 : HashCompareFunc match;
935 :
936 : #if HASH_STATISTICS
937 : hash_accesses++;
938 : hctl->accesses++;
939 : #endif
940 :
941 : /*
942 : * If inserting, check if it is time to split a bucket.
943 : *
944 : * NOTE: failure to expand table is not a fatal error, it just means we
945 : * have to run at higher fill factor than we wanted. However, if we're
946 : * using the palloc allocator then it will throw error anyway on
947 : * out-of-memory, so we must do this before modifying the table.
948 : */
949 216762508 : if (action == HASH_ENTER || action == HASH_ENTER_NULL)
950 : {
951 : /*
952 : * Can't split if running in partitioned mode, nor if frozen, nor if
953 : * table is the subject of any active hash_seq_search scans. Strange
954 : * order of these tests is to try to check cheaper conditions first.
955 : */
956 84621734 : if (!IS_PARTITIONED(hctl) && !hashp->frozen &&
957 39844748 : hctl->freeList[0].nentries / (long) (hctl->max_bucket + 1) >= hctl->ffactor &&
958 688472 : !has_seq_scans(hashp))
959 688472 : (void) expand_table(hashp);
960 : }
961 :
962 : /*
963 : * Do the initial lookup
964 : */
965 216762508 : bucket = calc_bucket(hctl, hashvalue);
966 :
967 216762508 : segment_num = bucket >> hashp->sshift;
968 216762508 : segment_ndx = MOD(bucket, hashp->ssize);
969 :
970 216762508 : segp = hashp->dir[segment_num];
971 :
972 216762508 : if (segp == NULL)
973 0 : hash_corrupted(hashp);
974 :
975 216762508 : prevBucketPtr = &segp[segment_ndx];
976 216762508 : currBucket = *prevBucketPtr;
977 :
978 : /*
979 : * Follow collision chain looking for matching key
980 : */
981 216762508 : match = hashp->match; /* save one fetch in inner loop */
982 216762508 : keysize = hashp->keysize; /* ditto */
983 :
984 469718604 : while (currBucket != NULL)
985 : {
986 387120268 : if (currBucket->hashvalue == hashvalue &&
987 175466992 : match(ELEMENTKEY(currBucket), keyPtr, keysize) == 0)
988 175459688 : break;
989 36193588 : prevBucketPtr = &(currBucket->link);
990 36193588 : currBucket = *prevBucketPtr;
991 : #if HASH_STATISTICS
992 : hash_collisions++;
993 : hctl->collisions++;
994 : #endif
995 : }
996 :
997 216762508 : if (foundPtr)
998 45210682 : *foundPtr = (bool) (currBucket != NULL);
999 :
1000 : /*
1001 : * OK, now what?
1002 : */
1003 216762508 : switch (action)
1004 : {
1005 : case HASH_FIND:
1006 139826152 : if (currBucket != NULL)
1007 135712818 : return (void *) ELEMENTKEY(currBucket);
1008 4113334 : return NULL;
1009 :
1010 : case HASH_REMOVE:
1011 31470898 : if (currBucket != NULL)
1012 : {
1013 : /* if partitioned, must lock to touch nentries and freeList */
1014 31394540 : if (IS_PARTITIONED(hctl))
1015 4680434 : SpinLockAcquire(&(hctl->freeList[freelist_idx].mutex));
1016 :
1017 : /* delete the record from the appropriate nentries counter. */
1018 : Assert(hctl->freeList[freelist_idx].nentries > 0);
1019 31394540 : hctl->freeList[freelist_idx].nentries--;
1020 :
1021 : /* remove record from hash bucket's chain. */
1022 31394540 : *prevBucketPtr = currBucket->link;
1023 :
1024 : /* add the record to the appropriate freelist. */
1025 31394540 : currBucket->link = hctl->freeList[freelist_idx].freeList;
1026 31394540 : hctl->freeList[freelist_idx].freeList = currBucket;
1027 :
1028 31394540 : if (IS_PARTITIONED(hctl))
1029 4680434 : SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1030 :
1031 : /*
1032 : * better hope the caller is synchronizing access to this
1033 : * element, because someone else is going to reuse it the next
1034 : * time something is added to the table
1035 : */
1036 31394540 : return (void *) ELEMENTKEY(currBucket);
1037 : }
1038 76358 : return NULL;
1039 :
1040 : case HASH_ENTER_NULL:
1041 : /* ENTER_NULL does not work with palloc-based allocator */
1042 : Assert(hashp->alloc != DynaHashAlloc);
1043 : /* FALL THRU */
1044 :
1045 : case HASH_ENTER:
1046 : /* Return existing element if found, else create one */
1047 45465458 : if (currBucket != NULL)
1048 8352330 : return (void *) ELEMENTKEY(currBucket);
1049 :
1050 : /* disallow inserts if frozen */
1051 37113128 : if (hashp->frozen)
1052 0 : elog(ERROR, "cannot insert into frozen hashtable \"%s\"",
1053 : hashp->tabname);
1054 :
1055 37113128 : currBucket = get_hash_entry(hashp, freelist_idx);
1056 37113128 : if (currBucket == NULL)
1057 : {
1058 : /* out of memory */
1059 0 : if (action == HASH_ENTER_NULL)
1060 0 : return NULL;
1061 : /* report a generic message */
1062 0 : if (hashp->isshared)
1063 0 : ereport(ERROR,
1064 : (errcode(ERRCODE_OUT_OF_MEMORY),
1065 : errmsg("out of shared memory")));
1066 : else
1067 0 : ereport(ERROR,
1068 : (errcode(ERRCODE_OUT_OF_MEMORY),
1069 : errmsg("out of memory")));
1070 : }
1071 :
1072 : /* link into hashbucket chain */
1073 37113128 : *prevBucketPtr = currBucket;
1074 37113128 : currBucket->link = NULL;
1075 :
1076 : /* copy key into record */
1077 37113128 : currBucket->hashvalue = hashvalue;
1078 37113128 : hashp->keycopy(ELEMENTKEY(currBucket), keyPtr, keysize);
1079 :
1080 : /*
1081 : * Caller is expected to fill the data field on return. DO NOT
1082 : * insert any code that could possibly throw error here, as doing
1083 : * so would leave the table entry incomplete and hence corrupt the
1084 : * caller's data structure.
1085 : */
1086 :
1087 37113128 : return (void *) ELEMENTKEY(currBucket);
1088 : }
1089 :
1090 0 : elog(ERROR, "unrecognized hash action code: %d", (int) action);
1091 :
1092 : return NULL; /* keep compiler quiet */
1093 : }
1094 :
1095 : /*
1096 : * hash_update_hash_key -- change the hash key of an existing table entry
1097 : *
1098 : * This is equivalent to removing the entry, making a new entry, and copying
1099 : * over its data, except that the entry never goes to the table's freelist.
1100 : * Therefore this cannot suffer an out-of-memory failure, even if there are
1101 : * other processes operating in other partitions of the hashtable.
1102 : *
1103 : * Returns true if successful, false if the requested new hash key is already
1104 : * present. Throws error if the specified entry pointer isn't actually a
1105 : * table member.
1106 : *
1107 : * NB: currently, there is no special case for old and new hash keys being
1108 : * identical, which means we'll report false for that situation. This is
1109 : * preferable for existing uses.
1110 : *
1111 : * NB: for a partitioned hashtable, caller must hold lock on both relevant
1112 : * partitions, if the new hash key would belong to a different partition.
1113 : */
1114 : bool
1115 176 : hash_update_hash_key(HTAB *hashp,
1116 : void *existingEntry,
1117 : const void *newKeyPtr)
1118 : {
1119 176 : HASHELEMENT *existingElement = ELEMENT_FROM_KEY(existingEntry);
1120 176 : HASHHDR *hctl = hashp->hctl;
1121 : uint32 newhashvalue;
1122 : Size keysize;
1123 : uint32 bucket;
1124 : uint32 newbucket;
1125 : long segment_num;
1126 : long segment_ndx;
1127 : HASHSEGMENT segp;
1128 : HASHBUCKET currBucket;
1129 : HASHBUCKET *prevBucketPtr;
1130 : HASHBUCKET *oldPrevPtr;
1131 : HashCompareFunc match;
1132 :
1133 : #if HASH_STATISTICS
1134 : hash_accesses++;
1135 : hctl->accesses++;
1136 : #endif
1137 :
1138 : /* disallow updates if frozen */
1139 176 : if (hashp->frozen)
1140 0 : elog(ERROR, "cannot update in frozen hashtable \"%s\"",
1141 : hashp->tabname);
1142 :
1143 : /*
1144 : * Lookup the existing element using its saved hash value. We need to do
1145 : * this to be able to unlink it from its hash chain, but as a side benefit
1146 : * we can verify the validity of the passed existingEntry pointer.
1147 : */
1148 176 : bucket = calc_bucket(hctl, existingElement->hashvalue);
1149 :
1150 176 : segment_num = bucket >> hashp->sshift;
1151 176 : segment_ndx = MOD(bucket, hashp->ssize);
1152 :
1153 176 : segp = hashp->dir[segment_num];
1154 :
1155 176 : if (segp == NULL)
1156 0 : hash_corrupted(hashp);
1157 :
1158 176 : prevBucketPtr = &segp[segment_ndx];
1159 176 : currBucket = *prevBucketPtr;
1160 :
1161 352 : while (currBucket != NULL)
1162 : {
1163 176 : if (currBucket == existingElement)
1164 176 : break;
1165 0 : prevBucketPtr = &(currBucket->link);
1166 0 : currBucket = *prevBucketPtr;
1167 : }
1168 :
1169 176 : if (currBucket == NULL)
1170 0 : elog(ERROR, "hash_update_hash_key argument is not in hashtable \"%s\"",
1171 : hashp->tabname);
1172 :
1173 176 : oldPrevPtr = prevBucketPtr;
1174 :
1175 : /*
1176 : * Now perform the equivalent of a HASH_ENTER operation to locate the hash
1177 : * chain we want to put the entry into.
1178 : */
1179 176 : newhashvalue = hashp->hash(newKeyPtr, hashp->keysize);
1180 :
1181 176 : newbucket = calc_bucket(hctl, newhashvalue);
1182 :
1183 176 : segment_num = newbucket >> hashp->sshift;
1184 176 : segment_ndx = MOD(newbucket, hashp->ssize);
1185 :
1186 176 : segp = hashp->dir[segment_num];
1187 :
1188 176 : if (segp == NULL)
1189 0 : hash_corrupted(hashp);
1190 :
1191 176 : prevBucketPtr = &segp[segment_ndx];
1192 176 : currBucket = *prevBucketPtr;
1193 :
1194 : /*
1195 : * Follow collision chain looking for matching key
1196 : */
1197 176 : match = hashp->match; /* save one fetch in inner loop */
1198 176 : keysize = hashp->keysize; /* ditto */
1199 :
1200 356 : while (currBucket != NULL)
1201 : {
1202 4 : if (currBucket->hashvalue == newhashvalue &&
1203 0 : match(ELEMENTKEY(currBucket), newKeyPtr, keysize) == 0)
1204 0 : break;
1205 4 : prevBucketPtr = &(currBucket->link);
1206 4 : currBucket = *prevBucketPtr;
1207 : #if HASH_STATISTICS
1208 : hash_collisions++;
1209 : hctl->collisions++;
1210 : #endif
1211 : }
1212 :
1213 176 : if (currBucket != NULL)
1214 0 : return false; /* collision with an existing entry */
1215 :
1216 176 : currBucket = existingElement;
1217 :
1218 : /*
1219 : * If old and new hash values belong to the same bucket, we need not
1220 : * change any chain links, and indeed should not since this simplistic
1221 : * update will corrupt the list if currBucket is the last element. (We
1222 : * cannot fall out earlier, however, since we need to scan the bucket to
1223 : * check for duplicate keys.)
1224 : */
1225 176 : if (bucket != newbucket)
1226 : {
1227 : /* OK to remove record from old hash bucket's chain. */
1228 176 : *oldPrevPtr = currBucket->link;
1229 :
1230 : /* link into new hashbucket chain */
1231 176 : *prevBucketPtr = currBucket;
1232 176 : currBucket->link = NULL;
1233 : }
1234 :
1235 : /* copy new key into record */
1236 176 : currBucket->hashvalue = newhashvalue;
1237 176 : hashp->keycopy(ELEMENTKEY(currBucket), newKeyPtr, keysize);
1238 :
1239 : /* rest of record is untouched */
1240 :
1241 176 : return true;
1242 : }
1243 :
1244 : /*
1245 : * Allocate a new hashtable entry if possible; return NULL if out of memory.
1246 : * (Or, if the underlying space allocator throws error for out-of-memory,
1247 : * we won't return at all.)
1248 : */
1249 : static HASHBUCKET
1250 37113128 : get_hash_entry(HTAB *hashp, int freelist_idx)
1251 : {
1252 37113128 : HASHHDR *hctl = hashp->hctl;
1253 : HASHBUCKET newElement;
1254 :
1255 : for (;;)
1256 : {
1257 : /* if partitioned, must lock to touch nentries and freeList */
1258 37631536 : if (IS_PARTITIONED(hctl))
1259 5288378 : SpinLockAcquire(&hctl->freeList[freelist_idx].mutex);
1260 :
1261 : /* try to get an entry from the freelist */
1262 37372332 : newElement = hctl->freeList[freelist_idx].freeList;
1263 :
1264 37372332 : if (newElement != NULL)
1265 37113128 : break;
1266 :
1267 259204 : if (IS_PARTITIONED(hctl))
1268 542 : SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1269 :
1270 : /*
1271 : * No free elements in this freelist. In a partitioned table, there
1272 : * might be entries in other freelists, but to reduce contention we
1273 : * prefer to first try to get another chunk of buckets from the main
1274 : * shmem allocator. If that fails, though, we *MUST* root through all
1275 : * the other freelists before giving up. There are multiple callers
1276 : * that assume that they can allocate every element in the initially
1277 : * requested table size, or that deleting an element guarantees they
1278 : * can insert a new element, even if shared memory is entirely full.
1279 : * Failing because the needed element is in a different freelist is
1280 : * not acceptable.
1281 : */
1282 259204 : if (!element_alloc(hashp, hctl->nelem_alloc, freelist_idx))
1283 : {
1284 : int borrow_from_idx;
1285 :
1286 0 : if (!IS_PARTITIONED(hctl))
1287 0 : return NULL; /* out of memory */
1288 :
1289 : /* try to borrow element from another freelist */
1290 0 : borrow_from_idx = freelist_idx;
1291 : for (;;)
1292 : {
1293 0 : borrow_from_idx = (borrow_from_idx + 1) % NUM_FREELISTS;
1294 0 : if (borrow_from_idx == freelist_idx)
1295 0 : break; /* examined all freelists, fail */
1296 :
1297 0 : SpinLockAcquire(&(hctl->freeList[borrow_from_idx].mutex));
1298 0 : newElement = hctl->freeList[borrow_from_idx].freeList;
1299 :
1300 0 : if (newElement != NULL)
1301 : {
1302 0 : hctl->freeList[borrow_from_idx].freeList = newElement->link;
1303 0 : SpinLockRelease(&(hctl->freeList[borrow_from_idx].mutex));
1304 :
1305 : /* careful: count the new element in its proper freelist */
1306 0 : SpinLockAcquire(&hctl->freeList[freelist_idx].mutex);
1307 0 : hctl->freeList[freelist_idx].nentries++;
1308 0 : SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1309 :
1310 0 : return newElement;
1311 : }
1312 :
1313 0 : SpinLockRelease(&(hctl->freeList[borrow_from_idx].mutex));
1314 : }
1315 :
1316 : /* no elements available to borrow either, so out of memory */
1317 0 : return NULL;
1318 : }
1319 : }
1320 :
1321 : /* remove entry from freelist, bump nentries */
1322 37113128 : hctl->freeList[freelist_idx].freeList = newElement->link;
1323 37113128 : hctl->freeList[freelist_idx].nentries++;
1324 :
1325 37113128 : if (IS_PARTITIONED(hctl))
1326 5287836 : SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1327 :
1328 37113128 : return newElement;
1329 : }
1330 :
1331 : /*
1332 : * hash_get_num_entries -- get the number of entries in a hashtable
1333 : */
1334 : long
1335 10290 : hash_get_num_entries(HTAB *hashp)
1336 : {
1337 : int i;
1338 10290 : long sum = hashp->hctl->freeList[0].nentries;
1339 :
1340 : /*
1341 : * We currently don't bother with acquiring the mutexes; it's only
1342 : * sensible to call this function if you've got lock on all partitions of
1343 : * the table.
1344 : */
1345 10290 : if (IS_PARTITIONED(hashp->hctl))
1346 : {
1347 81536 : for (i = 1; i < NUM_FREELISTS; i++)
1348 78988 : sum += hashp->hctl->freeList[i].nentries;
1349 : }
1350 :
1351 10290 : return sum;
1352 : }
1353 :
1354 : /*
1355 : * hash_seq_init/_search/_term
1356 : * Sequentially search through hash table and return
1357 : * all the elements one by one, return NULL when no more.
1358 : *
1359 : * hash_seq_term should be called if and only if the scan is abandoned before
1360 : * completion; if hash_seq_search returns NULL then it has already done the
1361 : * end-of-scan cleanup.
1362 : *
1363 : * NOTE: caller may delete the returned element before continuing the scan.
1364 : * However, deleting any other element while the scan is in progress is
1365 : * UNDEFINED (it might be the one that curIndex is pointing at!). Also,
1366 : * if elements are added to the table while the scan is in progress, it is
1367 : * unspecified whether they will be visited by the scan or not.
1368 : *
1369 : * NOTE: it is possible to use hash_seq_init/hash_seq_search without any
1370 : * worry about hash_seq_term cleanup, if the hashtable is first locked against
1371 : * further insertions by calling hash_freeze.
1372 : *
1373 : * NOTE: to use this with a partitioned hashtable, caller had better hold
1374 : * at least shared lock on all partitions of the table throughout the scan!
1375 : * We can cope with insertions or deletions by our own backend, but *not*
1376 : * with concurrent insertions or deletions by another.
1377 : */
1378 : void
1379 2691598 : hash_seq_init(HASH_SEQ_STATUS *status, HTAB *hashp)
1380 : {
1381 2691598 : status->hashp = hashp;
1382 2691598 : status->curBucket = 0;
1383 2691598 : status->curEntry = NULL;
1384 2691598 : if (!hashp->frozen)
1385 2691598 : register_seq_scan(hashp);
1386 2691598 : }
1387 :
1388 : void *
1389 25225332 : hash_seq_search(HASH_SEQ_STATUS *status)
1390 : {
1391 : HTAB *hashp;
1392 : HASHHDR *hctl;
1393 : uint32 max_bucket;
1394 : long ssize;
1395 : long segment_num;
1396 : long segment_ndx;
1397 : HASHSEGMENT segp;
1398 : uint32 curBucket;
1399 : HASHELEMENT *curElem;
1400 :
1401 25225332 : if ((curElem = status->curEntry) != NULL)
1402 : {
1403 : /* Continuing scan of curBucket... */
1404 4734926 : status->curEntry = curElem->link;
1405 4734926 : if (status->curEntry == NULL) /* end of this bucket */
1406 3496330 : ++status->curBucket;
1407 4734926 : return (void *) ELEMENTKEY(curElem);
1408 : }
1409 :
1410 : /*
1411 : * Search for next nonempty bucket starting at curBucket.
1412 : */
1413 20490406 : curBucket = status->curBucket;
1414 20490406 : hashp = status->hashp;
1415 20490406 : hctl = hashp->hctl;
1416 20490406 : ssize = hashp->ssize;
1417 20490406 : max_bucket = hctl->max_bucket;
1418 :
1419 20490406 : if (curBucket > max_bucket)
1420 : {
1421 70018 : hash_seq_term(status);
1422 70018 : return NULL; /* search is done */
1423 : }
1424 :
1425 : /*
1426 : * first find the right segment in the table directory.
1427 : */
1428 20420388 : segment_num = curBucket >> hashp->sshift;
1429 20420388 : segment_ndx = MOD(curBucket, ssize);
1430 :
1431 20420388 : segp = hashp->dir[segment_num];
1432 :
1433 : /*
1434 : * Pick up the first item in this bucket's chain. If chain is not empty
1435 : * we can begin searching it. Otherwise we have to advance to find the
1436 : * next nonempty bucket. We try to optimize that case since searching a
1437 : * near-empty hashtable has to iterate this loop a lot.
1438 : */
1439 215571302 : while ((curElem = segp[segment_ndx]) == NULL)
1440 : {
1441 : /* empty bucket, advance to next */
1442 177321186 : if (++curBucket > max_bucket)
1443 : {
1444 2590660 : status->curBucket = curBucket;
1445 2590660 : hash_seq_term(status);
1446 2590660 : return NULL; /* search is done */
1447 : }
1448 174730526 : if (++segment_ndx >= ssize)
1449 : {
1450 138164 : segment_num++;
1451 138164 : segment_ndx = 0;
1452 138164 : segp = hashp->dir[segment_num];
1453 : }
1454 : }
1455 :
1456 : /* Begin scan of curBucket... */
1457 17829728 : status->curEntry = curElem->link;
1458 17829728 : if (status->curEntry == NULL) /* end of this bucket */
1459 14333378 : ++curBucket;
1460 17829728 : status->curBucket = curBucket;
1461 17829728 : return (void *) ELEMENTKEY(curElem);
1462 : }
1463 :
1464 : void
1465 2691592 : hash_seq_term(HASH_SEQ_STATUS *status)
1466 : {
1467 2691592 : if (!status->hashp->frozen)
1468 2691592 : deregister_seq_scan(status->hashp);
1469 2691592 : }
1470 :
1471 : /*
1472 : * hash_freeze
1473 : * Freeze a hashtable against future insertions (deletions are
1474 : * still allowed)
1475 : *
1476 : * The reason for doing this is that by preventing any more bucket splits,
1477 : * we no longer need to worry about registering hash_seq_search scans,
1478 : * and thus caller need not be careful about ensuring hash_seq_term gets
1479 : * called at the right times.
1480 : *
1481 : * Multiple calls to hash_freeze() are allowed, but you can't freeze a table
1482 : * with active scans (since hash_seq_term would then do the wrong thing).
1483 : */
1484 : void
1485 0 : hash_freeze(HTAB *hashp)
1486 : {
1487 0 : if (hashp->isshared)
1488 0 : elog(ERROR, "cannot freeze shared hashtable \"%s\"", hashp->tabname);
1489 0 : if (!hashp->frozen && has_seq_scans(hashp))
1490 0 : elog(ERROR, "cannot freeze hashtable \"%s\" because it has active scans",
1491 : hashp->tabname);
1492 0 : hashp->frozen = true;
1493 0 : }
1494 :
1495 :
1496 : /********************************* UTILITIES ************************/
1497 :
1498 : /*
1499 : * Expand the table by adding one more hash bucket.
1500 : */
1501 : static bool
1502 688472 : expand_table(HTAB *hashp)
1503 : {
1504 688472 : HASHHDR *hctl = hashp->hctl;
1505 : HASHSEGMENT old_seg,
1506 : new_seg;
1507 : long old_bucket,
1508 : new_bucket;
1509 : long new_segnum,
1510 : new_segndx;
1511 : long old_segnum,
1512 : old_segndx;
1513 : HASHBUCKET *oldlink,
1514 : *newlink;
1515 : HASHBUCKET currElement,
1516 : nextElement;
1517 :
1518 : Assert(!IS_PARTITIONED(hctl));
1519 :
1520 : #ifdef HASH_STATISTICS
1521 : hash_expansions++;
1522 : #endif
1523 :
1524 688472 : new_bucket = hctl->max_bucket + 1;
1525 688472 : new_segnum = new_bucket >> hashp->sshift;
1526 688472 : new_segndx = MOD(new_bucket, hashp->ssize);
1527 :
1528 688472 : if (new_segnum >= hctl->nsegs)
1529 : {
1530 : /* Allocate new segment if necessary -- could fail if dir full */
1531 3054 : if (new_segnum >= hctl->dsize)
1532 0 : if (!dir_realloc(hashp))
1533 0 : return false;
1534 3054 : if (!(hashp->dir[new_segnum] = seg_alloc(hashp)))
1535 0 : return false;
1536 3054 : hctl->nsegs++;
1537 : }
1538 :
1539 : /* OK, we created a new bucket */
1540 688472 : hctl->max_bucket++;
1541 :
1542 : /*
1543 : * *Before* changing masks, find old bucket corresponding to same hash
1544 : * values; values in that bucket may need to be relocated to new bucket.
1545 : * Note that new_bucket is certainly larger than low_mask at this point,
1546 : * so we can skip the first step of the regular hash mask calc.
1547 : */
1548 688472 : old_bucket = (new_bucket & hctl->low_mask);
1549 :
1550 : /*
1551 : * If we crossed a power of 2, readjust masks.
1552 : */
1553 688472 : if ((uint32) new_bucket > hctl->high_mask)
1554 : {
1555 3622 : hctl->low_mask = hctl->high_mask;
1556 3622 : hctl->high_mask = (uint32) new_bucket | hctl->low_mask;
1557 : }
1558 :
1559 : /*
1560 : * Relocate records to the new bucket. NOTE: because of the way the hash
1561 : * masking is done in calc_bucket, only one old bucket can need to be
1562 : * split at this point. With a different way of reducing the hash value,
1563 : * that might not be true!
1564 : */
1565 688472 : old_segnum = old_bucket >> hashp->sshift;
1566 688472 : old_segndx = MOD(old_bucket, hashp->ssize);
1567 :
1568 688472 : old_seg = hashp->dir[old_segnum];
1569 688472 : new_seg = hashp->dir[new_segnum];
1570 :
1571 688472 : oldlink = &old_seg[old_segndx];
1572 688472 : newlink = &new_seg[new_segndx];
1573 :
1574 2330766 : for (currElement = *oldlink;
1575 : currElement != NULL;
1576 953822 : currElement = nextElement)
1577 : {
1578 953822 : nextElement = currElement->link;
1579 953822 : if ((long) calc_bucket(hctl, currElement->hashvalue) == old_bucket)
1580 : {
1581 480992 : *oldlink = currElement;
1582 480992 : oldlink = &currElement->link;
1583 : }
1584 : else
1585 : {
1586 472830 : *newlink = currElement;
1587 472830 : newlink = &currElement->link;
1588 : }
1589 : }
1590 : /* don't forget to terminate the rebuilt hash chains... */
1591 688472 : *oldlink = NULL;
1592 688472 : *newlink = NULL;
1593 :
1594 688472 : return true;
1595 : }
1596 :
1597 :
1598 : static bool
1599 0 : dir_realloc(HTAB *hashp)
1600 : {
1601 : HASHSEGMENT *p;
1602 : HASHSEGMENT *old_p;
1603 : long new_dsize;
1604 : long old_dirsize;
1605 : long new_dirsize;
1606 :
1607 0 : if (hashp->hctl->max_dsize != NO_MAX_DSIZE)
1608 0 : return false;
1609 :
1610 : /* Reallocate directory */
1611 0 : new_dsize = hashp->hctl->dsize << 1;
1612 0 : old_dirsize = hashp->hctl->dsize * sizeof(HASHSEGMENT);
1613 0 : new_dirsize = new_dsize * sizeof(HASHSEGMENT);
1614 :
1615 0 : old_p = hashp->dir;
1616 0 : CurrentDynaHashCxt = hashp->hcxt;
1617 0 : p = (HASHSEGMENT *) hashp->alloc((Size) new_dirsize);
1618 :
1619 0 : if (p != NULL)
1620 : {
1621 0 : memcpy(p, old_p, old_dirsize);
1622 0 : MemSet(((char *) p) + old_dirsize, 0, new_dirsize - old_dirsize);
1623 0 : hashp->dir = p;
1624 0 : hashp->hctl->dsize = new_dsize;
1625 :
1626 : /* XXX assume the allocator is palloc, so we know how to free */
1627 : Assert(hashp->alloc == DynaHashAlloc);
1628 0 : pfree(old_p);
1629 :
1630 0 : return true;
1631 : }
1632 :
1633 0 : return false;
1634 : }
1635 :
1636 :
1637 : static HASHSEGMENT
1638 712666 : seg_alloc(HTAB *hashp)
1639 : {
1640 : HASHSEGMENT segp;
1641 :
1642 712666 : CurrentDynaHashCxt = hashp->hcxt;
1643 712666 : segp = (HASHSEGMENT) hashp->alloc(sizeof(HASHBUCKET) * hashp->ssize);
1644 :
1645 712666 : if (!segp)
1646 0 : return NULL;
1647 :
1648 712666 : MemSet(segp, 0, sizeof(HASHBUCKET) * hashp->ssize);
1649 :
1650 712666 : return segp;
1651 : }
1652 :
1653 : /*
1654 : * allocate some new elements and link them into the indicated free list
1655 : */
1656 : static bool
1657 615066 : element_alloc(HTAB *hashp, int nelem, int freelist_idx)
1658 : {
1659 615066 : HASHHDR *hctl = hashp->hctl;
1660 : Size elementSize;
1661 : HASHELEMENT *firstElement;
1662 : HASHELEMENT *tmpElement;
1663 : HASHELEMENT *prevElement;
1664 : int i;
1665 :
1666 615066 : if (hashp->isfixed)
1667 0 : return false;
1668 :
1669 : /* Each element has a HASHELEMENT header plus user data. */
1670 615066 : elementSize = MAXALIGN(sizeof(HASHELEMENT)) + MAXALIGN(hctl->entrysize);
1671 :
1672 615066 : CurrentDynaHashCxt = hashp->hcxt;
1673 615066 : firstElement = (HASHELEMENT *) hashp->alloc(nelem * elementSize);
1674 :
1675 615066 : if (!firstElement)
1676 0 : return false;
1677 :
1678 : /* prepare to link all the new entries into the freelist */
1679 615066 : prevElement = NULL;
1680 615066 : tmpElement = firstElement;
1681 91464984 : for (i = 0; i < nelem; i++)
1682 : {
1683 90849918 : tmpElement->link = prevElement;
1684 90849918 : prevElement = tmpElement;
1685 90849918 : tmpElement = (HASHELEMENT *) (((char *) tmpElement) + elementSize);
1686 : }
1687 :
1688 : /* if partitioned, must lock to touch freeList */
1689 615066 : if (IS_PARTITIONED(hctl))
1690 297502 : SpinLockAcquire(&hctl->freeList[freelist_idx].mutex);
1691 :
1692 : /* freelist could be nonempty if two backends did this concurrently */
1693 615066 : firstElement->link = hctl->freeList[freelist_idx].freeList;
1694 615066 : hctl->freeList[freelist_idx].freeList = prevElement;
1695 :
1696 615066 : if (IS_PARTITIONED(hctl))
1697 297502 : SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1698 :
1699 615066 : return true;
1700 : }
1701 :
1702 : /* complain when we have detected a corrupted hashtable */
1703 : static void
1704 0 : hash_corrupted(HTAB *hashp)
1705 : {
1706 : /*
1707 : * If the corruption is in a shared hashtable, we'd better force a
1708 : * systemwide restart. Otherwise, just shut down this one backend.
1709 : */
1710 0 : if (hashp->isshared)
1711 0 : elog(PANIC, "hash table \"%s\" corrupted", hashp->tabname);
1712 : else
1713 0 : elog(FATAL, "hash table \"%s\" corrupted", hashp->tabname);
1714 : }
1715 :
1716 : /* calculate ceil(log base 2) of num */
1717 : int
1718 1852312 : my_log2(long num)
1719 : {
1720 : int i;
1721 : long limit;
1722 :
1723 : /* guard against too-large input, which would put us into infinite loop */
1724 1852312 : if (num > LONG_MAX / 2)
1725 0 : num = LONG_MAX / 2;
1726 :
1727 1852312 : for (i = 0, limit = 1; limit < num; i++, limit <<= 1)
1728 : ;
1729 1852312 : return i;
1730 : }
1731 :
1732 : /* calculate first power of 2 >= num, bounded to what will fit in a long */
1733 : static long
1734 52032 : next_pow2_long(long num)
1735 : {
1736 : /* my_log2's internal range check is sufficient */
1737 52032 : return 1L << my_log2(num);
1738 : }
1739 :
1740 : /* calculate first power of 2 >= num, bounded to what will fit in an int */
1741 : static int
1742 489860 : next_pow2_int(long num)
1743 : {
1744 489860 : if (num > INT_MAX / 2)
1745 0 : num = INT_MAX / 2;
1746 489860 : return 1 << my_log2(num);
1747 : }
1748 :
1749 :
1750 : /************************* SEQ SCAN TRACKING ************************/
1751 :
1752 : /*
1753 : * We track active hash_seq_search scans here. The need for this mechanism
1754 : * comes from the fact that a scan will get confused if a bucket split occurs
1755 : * while it's in progress: it might visit entries twice, or even miss some
1756 : * entirely (if it's partway through the same bucket that splits). Hence
1757 : * we want to inhibit bucket splits if there are any active scans on the
1758 : * table being inserted into. This is a fairly rare case in current usage,
1759 : * so just postponing the split until the next insertion seems sufficient.
1760 : *
1761 : * Given present usages of the function, only a few scans are likely to be
1762 : * open concurrently; so a finite-size stack of open scans seems sufficient,
1763 : * and we don't worry that linear search is too slow. Note that we do
1764 : * allow multiple scans of the same hashtable to be open concurrently.
1765 : *
1766 : * This mechanism can support concurrent scan and insertion in a shared
1767 : * hashtable if it's the same backend doing both. It would fail otherwise,
1768 : * but locking reasons seem to preclude any such scenario anyway, so we don't
1769 : * worry.
1770 : *
1771 : * This arrangement is reasonably robust if a transient hashtable is deleted
1772 : * without notifying us. The absolute worst case is we might inhibit splits
1773 : * in another table created later at exactly the same address. We will give
1774 : * a warning at transaction end for reference leaks, so any bugs leading to
1775 : * lack of notification should be easy to catch.
1776 : */
1777 :
1778 : #define MAX_SEQ_SCANS 100
1779 :
1780 : static HTAB *seq_scan_tables[MAX_SEQ_SCANS]; /* tables being scanned */
1781 : static int seq_scan_level[MAX_SEQ_SCANS]; /* subtransaction nest level */
1782 : static int num_seq_scans = 0;
1783 :
1784 :
1785 : /* Register a table as having an active hash_seq_search scan */
1786 : static void
1787 2691598 : register_seq_scan(HTAB *hashp)
1788 : {
1789 2691598 : if (num_seq_scans >= MAX_SEQ_SCANS)
1790 0 : elog(ERROR, "too many active hash_seq_search scans, cannot start one on \"%s\"",
1791 : hashp->tabname);
1792 2691598 : seq_scan_tables[num_seq_scans] = hashp;
1793 2691598 : seq_scan_level[num_seq_scans] = GetCurrentTransactionNestLevel();
1794 2691598 : num_seq_scans++;
1795 2691598 : }
1796 :
1797 : /* Deregister an active scan */
1798 : static void
1799 2691592 : deregister_seq_scan(HTAB *hashp)
1800 : {
1801 : int i;
1802 :
1803 : /* Search backward since it's most likely at the stack top */
1804 2691592 : for (i = num_seq_scans - 1; i >= 0; i--)
1805 : {
1806 2691592 : if (seq_scan_tables[i] == hashp)
1807 : {
1808 2691592 : seq_scan_tables[i] = seq_scan_tables[num_seq_scans - 1];
1809 2691592 : seq_scan_level[i] = seq_scan_level[num_seq_scans - 1];
1810 2691592 : num_seq_scans--;
1811 2691592 : return;
1812 : }
1813 : }
1814 0 : elog(ERROR, "no hash_seq_search scan for hash table \"%s\"",
1815 : hashp->tabname);
1816 : }
1817 :
1818 : /* Check if a table has any active scan */
1819 : static bool
1820 688472 : has_seq_scans(HTAB *hashp)
1821 : {
1822 : int i;
1823 :
1824 688472 : for (i = 0; i < num_seq_scans; i++)
1825 : {
1826 0 : if (seq_scan_tables[i] == hashp)
1827 0 : return true;
1828 : }
1829 688472 : return false;
1830 : }
1831 :
1832 : /* Clean up any open scans at end of transaction */
1833 : void
1834 460098 : AtEOXact_HashTables(bool isCommit)
1835 : {
1836 : /*
1837 : * During abort cleanup, open scans are expected; just silently clean 'em
1838 : * out. An open scan at commit means someone forgot a hash_seq_term()
1839 : * call, so complain.
1840 : *
1841 : * Note: it's tempting to try to print the tabname here, but refrain for
1842 : * fear of touching deallocated memory. This isn't a user-facing message
1843 : * anyway, so it needn't be pretty.
1844 : */
1845 460098 : if (isCommit)
1846 : {
1847 : int i;
1848 :
1849 440984 : for (i = 0; i < num_seq_scans; i++)
1850 : {
1851 0 : elog(WARNING, "leaked hash_seq_search scan for hash table %p",
1852 : seq_scan_tables[i]);
1853 : }
1854 : }
1855 460098 : num_seq_scans = 0;
1856 460098 : }
1857 :
1858 : /* Clean up any open scans at end of subtransaction */
1859 : void
1860 7364 : AtEOSubXact_HashTables(bool isCommit, int nestDepth)
1861 : {
1862 : int i;
1863 :
1864 : /*
1865 : * Search backward to make cleanup easy. Note we must check all entries,
1866 : * not only those at the end of the array, because deletion technique
1867 : * doesn't keep them in order.
1868 : */
1869 7364 : for (i = num_seq_scans - 1; i >= 0; i--)
1870 : {
1871 0 : if (seq_scan_level[i] >= nestDepth)
1872 : {
1873 0 : if (isCommit)
1874 0 : elog(WARNING, "leaked hash_seq_search scan for hash table %p",
1875 : seq_scan_tables[i]);
1876 0 : seq_scan_tables[i] = seq_scan_tables[num_seq_scans - 1];
1877 0 : seq_scan_level[i] = seq_scan_level[num_seq_scans - 1];
1878 0 : num_seq_scans--;
1879 : }
1880 : }
1881 7364 : }
|
