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) 1996-2020, 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 "common/hashfn.h"
90 : #include "port/pg_bitutils.h"
91 : #include "storage/shmem.h"
92 : #include "storage/spin.h"
93 : #include "utils/dynahash.h"
94 : #include "utils/memutils.h"
95 :
96 :
97 : /*
98 : * Constants
99 : *
100 : * A hash table has a top-level "directory", each of whose entries points
101 : * to a "segment" of ssize bucket headers. The maximum number of hash
102 : * buckets is thus dsize * ssize (but dsize may be expansible). Of course,
103 : * the number of records in the table can be larger, but we don't want a
104 : * whole lot of records per bucket or performance goes down.
105 : *
106 : * In a hash table allocated in shared memory, the directory cannot be
107 : * expanded because it must stay at a fixed address. The directory size
108 : * should be selected using hash_select_dirsize (and you'd better have
109 : * a good idea of the maximum number of entries!). For non-shared hash
110 : * tables, the initial directory size can be left at the default.
111 : */
112 : #define DEF_SEGSIZE 256
113 : #define DEF_SEGSIZE_SHIFT 8 /* must be log2(DEF_SEGSIZE) */
114 : #define DEF_DIRSIZE 256
115 : #define DEF_FFACTOR 1 /* default fill factor */
116 :
117 : /* Number of freelists to be used for a partitioned hash table. */
118 : #define NUM_FREELISTS 32
119 :
120 : /* A hash bucket is a linked list of HASHELEMENTs */
121 : typedef HASHELEMENT *HASHBUCKET;
122 :
123 : /* A hash segment is an array of bucket headers */
124 : typedef HASHBUCKET *HASHSEGMENT;
125 :
126 : /*
127 : * Per-freelist data.
128 : *
129 : * In a partitioned hash table, each freelist is associated with a specific
130 : * set of hashcodes, as determined by the FREELIST_IDX() macro below.
131 : * nentries tracks the number of live hashtable entries having those hashcodes
132 : * (NOT the number of entries in the freelist, as you might expect).
133 : *
134 : * The coverage of a freelist might be more or less than one partition, so it
135 : * needs its own lock rather than relying on caller locking. Relying on that
136 : * wouldn't work even if the coverage was the same, because of the occasional
137 : * need to "borrow" entries from another freelist; see get_hash_entry().
138 : *
139 : * Using an array of FreeListData instead of separate arrays of mutexes,
140 : * nentries and freeLists helps to reduce sharing of cache lines between
141 : * different mutexes.
142 : */
143 : typedef struct
144 : {
145 : slock_t mutex; /* spinlock for this freelist */
146 : long nentries; /* number of entries in associated buckets */
147 : HASHELEMENT *freeList; /* chain of free elements */
148 : } FreeListData;
149 :
150 : /*
151 : * Header structure for a hash table --- contains all changeable info
152 : *
153 : * In a shared-memory hash table, the HASHHDR is in shared memory, while
154 : * each backend has a local HTAB struct. For a non-shared table, there isn't
155 : * any functional difference between HASHHDR and HTAB, but we separate them
156 : * anyway to share code between shared and non-shared tables.
157 : */
158 : struct HASHHDR
159 : {
160 : /*
161 : * The freelist can become a point of contention in high-concurrency hash
162 : * tables, so we use an array of freelists, each with its own mutex and
163 : * nentries count, instead of just a single one. Although the freelists
164 : * normally operate independently, we will scavenge entries from freelists
165 : * other than a hashcode's default freelist when necessary.
166 : *
167 : * If the hash table is not partitioned, only freeList[0] is used and its
168 : * spinlock is not used at all; callers' locking is assumed sufficient.
169 : */
170 : FreeListData freeList[NUM_FREELISTS];
171 :
172 : /* These fields can change, but not in a partitioned table */
173 : /* Also, dsize can't change in a shared table, even if unpartitioned */
174 : long dsize; /* directory size */
175 : long nsegs; /* number of allocated segments (<= dsize) */
176 : uint32 max_bucket; /* ID of maximum bucket in use */
177 : uint32 high_mask; /* mask to modulo into entire table */
178 : uint32 low_mask; /* mask to modulo into lower half of table */
179 :
180 : /* These fields are fixed at hashtable creation */
181 : Size keysize; /* hash key length in bytes */
182 : Size entrysize; /* total user element size in bytes */
183 : long num_partitions; /* # partitions (must be power of 2), or 0 */
184 : long ffactor; /* target fill factor */
185 : long max_dsize; /* 'dsize' limit if directory is fixed size */
186 : long ssize; /* segment size --- must be power of 2 */
187 : int sshift; /* segment shift = log2(ssize) */
188 : int nelem_alloc; /* number of entries to allocate at once */
189 :
190 : #ifdef HASH_STATISTICS
191 :
192 : /*
193 : * Count statistics here. NB: stats code doesn't bother with mutex, so
194 : * counts could be corrupted a bit in a partitioned table.
195 : */
196 : long accesses;
197 : long collisions;
198 : #endif
199 : };
200 :
201 : #define IS_PARTITIONED(hctl) ((hctl)->num_partitions != 0)
202 :
203 : #define FREELIST_IDX(hctl, hashcode) \
204 : (IS_PARTITIONED(hctl) ? (hashcode) % NUM_FREELISTS : 0)
205 :
206 : /*
207 : * Top control structure for a hashtable --- in a shared table, each backend
208 : * has its own copy (OK since no fields change at runtime)
209 : */
210 : struct HTAB
211 : {
212 : HASHHDR *hctl; /* => shared control information */
213 : HASHSEGMENT *dir; /* directory of segment starts */
214 : HashValueFunc hash; /* hash function */
215 : HashCompareFunc match; /* key comparison function */
216 : HashCopyFunc keycopy; /* key copying function */
217 : HashAllocFunc alloc; /* memory allocator */
218 : MemoryContext hcxt; /* memory context if default allocator used */
219 : char *tabname; /* table name (for error messages) */
220 : bool isshared; /* true if table is in shared memory */
221 : bool isfixed; /* if true, don't enlarge */
222 :
223 : /* freezing a shared table isn't allowed, so we can keep state here */
224 : bool frozen; /* true = no more inserts allowed */
225 :
226 : /* We keep local copies of these fixed values to reduce contention */
227 : Size keysize; /* hash key length in bytes */
228 : long ssize; /* segment size --- must be power of 2 */
229 : int sshift; /* segment shift = log2(ssize) */
230 : };
231 :
232 : /*
233 : * Key (also entry) part of a HASHELEMENT
234 : */
235 : #define ELEMENTKEY(helem) (((char *)(helem)) + MAXALIGN(sizeof(HASHELEMENT)))
236 :
237 : /*
238 : * Obtain element pointer given pointer to key
239 : */
240 : #define ELEMENT_FROM_KEY(key) \
241 : ((HASHELEMENT *) (((char *) (key)) - MAXALIGN(sizeof(HASHELEMENT))))
242 :
243 : /*
244 : * Fast MOD arithmetic, assuming that y is a power of 2 !
245 : */
246 : #define MOD(x,y) ((x) & ((y)-1))
247 :
248 : #ifdef HASH_STATISTICS
249 : static long hash_accesses,
250 : hash_collisions,
251 : hash_expansions;
252 : #endif
253 :
254 : /*
255 : * Private function prototypes
256 : */
257 : static void *DynaHashAlloc(Size size);
258 : static HASHSEGMENT seg_alloc(HTAB *hashp);
259 : static bool element_alloc(HTAB *hashp, int nelem, int freelist_idx);
260 : static bool dir_realloc(HTAB *hashp);
261 : static bool expand_table(HTAB *hashp);
262 : static HASHBUCKET get_hash_entry(HTAB *hashp, int freelist_idx);
263 : static void hdefault(HTAB *hashp);
264 : static int choose_nelem_alloc(Size entrysize);
265 : static bool init_htab(HTAB *hashp, long nelem);
266 : static void hash_corrupted(HTAB *hashp);
267 : static long next_pow2_long(long num);
268 : static int next_pow2_int(long num);
269 : static void register_seq_scan(HTAB *hashp);
270 : static void deregister_seq_scan(HTAB *hashp);
271 : static bool has_seq_scans(HTAB *hashp);
272 :
273 :
274 : /*
275 : * memory allocation support
276 : */
277 : static MemoryContext CurrentDynaHashCxt = NULL;
278 :
279 : static void *
280 1497708 : DynaHashAlloc(Size size)
281 : {
282 : Assert(MemoryContextIsValid(CurrentDynaHashCxt));
283 1497708 : return MemoryContextAlloc(CurrentDynaHashCxt, size);
284 : }
285 :
286 :
287 : /*
288 : * HashCompareFunc for string keys
289 : *
290 : * Because we copy keys with strlcpy(), they will be truncated at keysize-1
291 : * bytes, so we can only compare that many ... hence strncmp is almost but
292 : * not quite the right thing.
293 : */
294 : static int
295 681108 : string_compare(const char *key1, const char *key2, Size keysize)
296 : {
297 681108 : return strncmp(key1, key2, keysize - 1);
298 : }
299 :
300 :
301 : /************************** CREATE ROUTINES **********************/
302 :
303 : /*
304 : * hash_create -- create a new dynamic hash table
305 : *
306 : * tabname: a name for the table (for debugging purposes)
307 : * nelem: maximum number of elements expected
308 : * *info: additional table parameters, as indicated by flags
309 : * flags: bitmask indicating which parameters to take from *info
310 : *
311 : * Note: for a shared-memory hashtable, nelem needs to be a pretty good
312 : * estimate, since we can't expand the table on the fly. But an unshared
313 : * hashtable can be expanded on-the-fly, so it's better for nelem to be
314 : * on the small side and let the table grow if it's exceeded. An overly
315 : * large nelem will penalize hash_seq_search speed without buying much.
316 : */
317 : HTAB *
318 280622 : hash_create(const char *tabname, long nelem, HASHCTL *info, int flags)
319 : {
320 : HTAB *hashp;
321 : HASHHDR *hctl;
322 :
323 : /*
324 : * For shared hash tables, we have a local hash header (HTAB struct) that
325 : * we allocate in TopMemoryContext; all else is in shared memory.
326 : *
327 : * For non-shared hash tables, everything including the hash header is in
328 : * a memory context created specially for the hash table --- this makes
329 : * hash_destroy very simple. The memory context is made a child of either
330 : * a context specified by the caller, or TopMemoryContext if nothing is
331 : * specified.
332 : */
333 280622 : if (flags & HASH_SHARED_MEM)
334 : {
335 : /* Set up to allocate the hash header */
336 15192 : CurrentDynaHashCxt = TopMemoryContext;
337 : }
338 : else
339 : {
340 : /* Create the hash table's private memory context */
341 265430 : if (flags & HASH_CONTEXT)
342 157690 : CurrentDynaHashCxt = info->hcxt;
343 : else
344 107740 : CurrentDynaHashCxt = TopMemoryContext;
345 265430 : CurrentDynaHashCxt = AllocSetContextCreate(CurrentDynaHashCxt,
346 : "dynahash",
347 : ALLOCSET_DEFAULT_SIZES);
348 : }
349 :
350 : /* Initialize the hash header, plus a copy of the table name */
351 280622 : hashp = (HTAB *) DynaHashAlloc(sizeof(HTAB) + strlen(tabname) + 1);
352 3648086 : MemSet(hashp, 0, sizeof(HTAB));
353 :
354 280622 : hashp->tabname = (char *) (hashp + 1);
355 280622 : strcpy(hashp->tabname, tabname);
356 :
357 : /* If we have a private context, label it with hashtable's name */
358 280622 : if (!(flags & HASH_SHARED_MEM))
359 265430 : MemoryContextSetIdentifier(CurrentDynaHashCxt, hashp->tabname);
360 :
361 : /*
362 : * Select the appropriate hash function (see comments at head of file).
363 : */
364 280622 : if (flags & HASH_FUNCTION)
365 13760 : hashp->hash = info->hash;
366 266862 : else if (flags & HASH_BLOBS)
367 : {
368 : /* We can optimize hashing for common key sizes */
369 : Assert(flags & HASH_ELEM);
370 223538 : if (info->keysize == sizeof(uint32))
371 122450 : hashp->hash = uint32_hash;
372 : else
373 101088 : hashp->hash = tag_hash;
374 : }
375 : else
376 43324 : hashp->hash = string_hash; /* default hash function */
377 :
378 : /*
379 : * If you don't specify a match function, it defaults to string_compare if
380 : * you used string_hash (either explicitly or by default) and to memcmp
381 : * otherwise.
382 : *
383 : * Note: explicitly specifying string_hash is deprecated, because this
384 : * might not work for callers in loadable modules on some platforms due to
385 : * referencing a trampoline instead of the string_hash function proper.
386 : * Just let it default, eh?
387 : */
388 280622 : if (flags & HASH_COMPARE)
389 9420 : hashp->match = info->match;
390 271202 : else if (hashp->hash == string_hash)
391 43324 : hashp->match = (HashCompareFunc) string_compare;
392 : else
393 227878 : hashp->match = memcmp;
394 :
395 : /*
396 : * Similarly, the key-copying function defaults to strlcpy or memcpy.
397 : */
398 280622 : if (flags & HASH_KEYCOPY)
399 0 : hashp->keycopy = info->keycopy;
400 280622 : else if (hashp->hash == string_hash)
401 43324 : hashp->keycopy = (HashCopyFunc) strlcpy;
402 : else
403 237298 : hashp->keycopy = memcpy;
404 :
405 : /* And select the entry allocation function, too. */
406 280622 : if (flags & HASH_ALLOC)
407 15192 : hashp->alloc = info->alloc;
408 : else
409 265430 : hashp->alloc = DynaHashAlloc;
410 :
411 280622 : if (flags & HASH_SHARED_MEM)
412 : {
413 : /*
414 : * ctl structure and directory are preallocated for shared memory
415 : * tables. Note that HASH_DIRSIZE and HASH_ALLOC had better be set as
416 : * well.
417 : */
418 15192 : hashp->hctl = info->hctl;
419 15192 : hashp->dir = (HASHSEGMENT *) (((char *) info->hctl) + sizeof(HASHHDR));
420 15192 : hashp->hcxt = NULL;
421 15192 : hashp->isshared = true;
422 :
423 : /* hash table already exists, we're just attaching to it */
424 15192 : if (flags & HASH_ATTACH)
425 : {
426 : /* make local copies of some heavily-used values */
427 0 : hctl = hashp->hctl;
428 0 : hashp->keysize = hctl->keysize;
429 0 : hashp->ssize = hctl->ssize;
430 0 : hashp->sshift = hctl->sshift;
431 :
432 0 : return hashp;
433 : }
434 : }
435 : else
436 : {
437 : /* setup hash table defaults */
438 265430 : hashp->hctl = NULL;
439 265430 : hashp->dir = NULL;
440 265430 : hashp->hcxt = CurrentDynaHashCxt;
441 265430 : hashp->isshared = false;
442 : }
443 :
444 280622 : if (!hashp->hctl)
445 : {
446 265430 : hashp->hctl = (HASHHDR *) hashp->alloc(sizeof(HASHHDR));
447 265430 : if (!hashp->hctl)
448 0 : ereport(ERROR,
449 : (errcode(ERRCODE_OUT_OF_MEMORY),
450 : errmsg("out of memory")));
451 : }
452 :
453 280622 : hashp->frozen = false;
454 :
455 280622 : hdefault(hashp);
456 :
457 280622 : hctl = hashp->hctl;
458 :
459 280622 : if (flags & HASH_PARTITION)
460 : {
461 : /* Doesn't make sense to partition a local hash table */
462 : Assert(flags & HASH_SHARED_MEM);
463 :
464 : /*
465 : * The number of partitions had better be a power of 2. Also, it must
466 : * be less than INT_MAX (see init_htab()), so call the int version of
467 : * next_pow2.
468 : */
469 : Assert(info->num_partitions == next_pow2_int(info->num_partitions));
470 :
471 10850 : hctl->num_partitions = info->num_partitions;
472 : }
473 :
474 280622 : if (flags & HASH_SEGMENT)
475 : {
476 0 : hctl->ssize = info->ssize;
477 0 : hctl->sshift = my_log2(info->ssize);
478 : /* ssize had better be a power of 2 */
479 : Assert(hctl->ssize == (1L << hctl->sshift));
480 : }
481 280622 : if (flags & HASH_FFACTOR)
482 0 : hctl->ffactor = info->ffactor;
483 :
484 : /*
485 : * SHM hash tables have fixed directory size passed by the caller.
486 : */
487 280622 : if (flags & HASH_DIRSIZE)
488 : {
489 15192 : hctl->max_dsize = info->max_dsize;
490 15192 : hctl->dsize = info->dsize;
491 : }
492 :
493 : /*
494 : * hash table now allocates space for key and data but you have to say how
495 : * much space to allocate
496 : */
497 280622 : if (flags & HASH_ELEM)
498 : {
499 : Assert(info->entrysize >= info->keysize);
500 280622 : hctl->keysize = info->keysize;
501 280622 : hctl->entrysize = info->entrysize;
502 : }
503 :
504 : /* make local copies of heavily-used constant fields */
505 280622 : hashp->keysize = hctl->keysize;
506 280622 : hashp->ssize = hctl->ssize;
507 280622 : hashp->sshift = hctl->sshift;
508 :
509 : /* Build the hash directory structure */
510 280622 : if (!init_htab(hashp, nelem))
511 0 : elog(ERROR, "failed to initialize hash table \"%s\"", hashp->tabname);
512 :
513 : /*
514 : * For a shared hash table, preallocate the requested number of elements.
515 : * This reduces problems with run-time out-of-shared-memory conditions.
516 : *
517 : * For a non-shared hash table, preallocate the requested number of
518 : * elements if it's less than our chosen nelem_alloc. This avoids wasting
519 : * space if the caller correctly estimates a small table size.
520 : */
521 280622 : if ((flags & HASH_SHARED_MEM) ||
522 265430 : nelem < hctl->nelem_alloc)
523 : {
524 : int i,
525 : freelist_partitions,
526 : nelem_alloc,
527 : nelem_alloc_first;
528 :
529 : /*
530 : * If hash table is partitioned, give each freelist an equal share of
531 : * the initial allocation. Otherwise only freeList[0] is used.
532 : */
533 82634 : if (IS_PARTITIONED(hashp->hctl))
534 10850 : freelist_partitions = NUM_FREELISTS;
535 : else
536 71784 : freelist_partitions = 1;
537 :
538 82634 : nelem_alloc = nelem / freelist_partitions;
539 82634 : if (nelem_alloc <= 0)
540 0 : nelem_alloc = 1;
541 :
542 : /*
543 : * Make sure we'll allocate all the requested elements; freeList[0]
544 : * gets the excess if the request isn't divisible by NUM_FREELISTS.
545 : */
546 82634 : if (nelem_alloc * freelist_partitions < nelem)
547 362 : nelem_alloc_first =
548 362 : nelem - nelem_alloc * (freelist_partitions - 1);
549 : else
550 82272 : nelem_alloc_first = nelem_alloc;
551 :
552 501618 : for (i = 0; i < freelist_partitions; i++)
553 : {
554 418984 : int temp = (i == 0) ? nelem_alloc_first : nelem_alloc;
555 :
556 418984 : if (!element_alloc(hashp, temp, i))
557 0 : ereport(ERROR,
558 : (errcode(ERRCODE_OUT_OF_MEMORY),
559 : errmsg("out of memory")));
560 : }
561 : }
562 :
563 280622 : if (flags & HASH_FIXED_SIZE)
564 6510 : hashp->isfixed = true;
565 280622 : return hashp;
566 : }
567 :
568 : /*
569 : * Set default HASHHDR parameters.
570 : */
571 : static void
572 280622 : hdefault(HTAB *hashp)
573 : {
574 280622 : HASHHDR *hctl = hashp->hctl;
575 :
576 30307176 : MemSet(hctl, 0, sizeof(HASHHDR));
577 :
578 280622 : hctl->dsize = DEF_DIRSIZE;
579 280622 : hctl->nsegs = 0;
580 :
581 : /* rather pointless defaults for key & entry size */
582 280622 : hctl->keysize = sizeof(char *);
583 280622 : hctl->entrysize = 2 * sizeof(char *);
584 :
585 280622 : hctl->num_partitions = 0; /* not partitioned */
586 :
587 280622 : hctl->ffactor = DEF_FFACTOR;
588 :
589 : /* table has no fixed maximum size */
590 280622 : hctl->max_dsize = NO_MAX_DSIZE;
591 :
592 280622 : hctl->ssize = DEF_SEGSIZE;
593 280622 : hctl->sshift = DEF_SEGSIZE_SHIFT;
594 :
595 : #ifdef HASH_STATISTICS
596 : hctl->accesses = hctl->collisions = 0;
597 : #endif
598 280622 : }
599 :
600 : /*
601 : * Given the user-specified entry size, choose nelem_alloc, ie, how many
602 : * elements to add to the hash table when we need more.
603 : */
604 : static int
605 295842 : choose_nelem_alloc(Size entrysize)
606 : {
607 : int nelem_alloc;
608 : Size elementSize;
609 : Size allocSize;
610 :
611 : /* Each element has a HASHELEMENT header plus user data. */
612 : /* NB: this had better match element_alloc() */
613 295842 : elementSize = MAXALIGN(sizeof(HASHELEMENT)) + MAXALIGN(entrysize);
614 :
615 : /*
616 : * The idea here is to choose nelem_alloc at least 32, but round up so
617 : * that the allocation request will be a power of 2 or just less. This
618 : * makes little difference for hash tables in shared memory, but for hash
619 : * tables managed by palloc, the allocation request will be rounded up to
620 : * a power of 2 anyway. If we fail to take this into account, we'll waste
621 : * as much as half the allocated space.
622 : */
623 295842 : allocSize = 32 * 4; /* assume elementSize at least 8 */
624 : do
625 : {
626 1173996 : allocSize <<= 1;
627 1173996 : nelem_alloc = allocSize / elementSize;
628 1173996 : } while (nelem_alloc < 32);
629 :
630 295842 : return nelem_alloc;
631 : }
632 :
633 : /*
634 : * Compute derived fields of hctl and build the initial directory/segment
635 : * arrays
636 : */
637 : static bool
638 280622 : init_htab(HTAB *hashp, long nelem)
639 : {
640 280622 : HASHHDR *hctl = hashp->hctl;
641 : HASHSEGMENT *segp;
642 : int nbuckets;
643 : int nsegs;
644 : int i;
645 :
646 : /*
647 : * initialize mutexes if it's a partitioned table
648 : */
649 280622 : if (IS_PARTITIONED(hctl))
650 358050 : for (i = 0; i < NUM_FREELISTS; i++)
651 347200 : SpinLockInit(&(hctl->freeList[i].mutex));
652 :
653 : /*
654 : * Divide number of elements by the fill factor to determine a desired
655 : * number of buckets. Allocate space for the next greater power of two
656 : * number of buckets
657 : */
658 280622 : nbuckets = next_pow2_int((nelem - 1) / hctl->ffactor + 1);
659 :
660 : /*
661 : * In a partitioned table, nbuckets must be at least equal to
662 : * num_partitions; were it less, keys with apparently different partition
663 : * numbers would map to the same bucket, breaking partition independence.
664 : * (Normally nbuckets will be much bigger; this is just a safety check.)
665 : */
666 280622 : while (nbuckets < hctl->num_partitions)
667 0 : nbuckets <<= 1;
668 :
669 280622 : hctl->max_bucket = hctl->low_mask = nbuckets - 1;
670 280622 : hctl->high_mask = (nbuckets << 1) - 1;
671 :
672 : /*
673 : * Figure number of directory segments needed, round up to a power of 2
674 : */
675 280622 : nsegs = (nbuckets - 1) / hctl->ssize + 1;
676 280622 : nsegs = next_pow2_int(nsegs);
677 :
678 : /*
679 : * Make sure directory is big enough. If pre-allocated directory is too
680 : * small, choke (caller screwed up).
681 : */
682 280622 : if (nsegs > hctl->dsize)
683 : {
684 0 : if (!(hashp->dir))
685 0 : hctl->dsize = nsegs;
686 : else
687 0 : return false;
688 : }
689 :
690 : /* Allocate a directory */
691 280622 : if (!(hashp->dir))
692 : {
693 265430 : CurrentDynaHashCxt = hashp->hcxt;
694 265430 : hashp->dir = (HASHSEGMENT *)
695 265430 : hashp->alloc(hctl->dsize * sizeof(HASHSEGMENT));
696 265430 : if (!hashp->dir)
697 0 : return false;
698 : }
699 :
700 : /* Allocate initial segments */
701 1092810 : for (segp = hashp->dir; hctl->nsegs < nsegs; hctl->nsegs++, segp++)
702 : {
703 812188 : *segp = seg_alloc(hashp);
704 812188 : if (*segp == NULL)
705 0 : return false;
706 : }
707 :
708 : /* Choose number of entries to allocate at a time */
709 280622 : hctl->nelem_alloc = choose_nelem_alloc(hctl->entrysize);
710 :
711 : #ifdef HASH_DEBUG
712 : 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",
713 : "TABLE POINTER ", hashp,
714 : "DIRECTORY SIZE ", hctl->dsize,
715 : "SEGMENT SIZE ", hctl->ssize,
716 : "SEGMENT SHIFT ", hctl->sshift,
717 : "FILL FACTOR ", hctl->ffactor,
718 : "MAX BUCKET ", hctl->max_bucket,
719 : "HIGH MASK ", hctl->high_mask,
720 : "LOW MASK ", hctl->low_mask,
721 : "NSEGS ", hctl->nsegs);
722 : #endif
723 280622 : return true;
724 : }
725 :
726 : /*
727 : * Estimate the space needed for a hashtable containing the given number
728 : * of entries of given size.
729 : * NOTE: this is used to estimate the footprint of hashtables in shared
730 : * memory; therefore it does not count HTAB which is in local memory.
731 : * NB: assumes that all hash structure parameters have default values!
732 : */
733 : Size
734 15220 : hash_estimate_size(long num_entries, Size entrysize)
735 : {
736 : Size size;
737 : long nBuckets,
738 : nSegments,
739 : nDirEntries,
740 : nElementAllocs,
741 : elementSize,
742 : elementAllocCnt;
743 :
744 : /* estimate number of buckets wanted */
745 15220 : nBuckets = next_pow2_long((num_entries - 1) / DEF_FFACTOR + 1);
746 : /* # of segments needed for nBuckets */
747 15220 : nSegments = next_pow2_long((nBuckets - 1) / DEF_SEGSIZE + 1);
748 : /* directory entries */
749 15220 : nDirEntries = DEF_DIRSIZE;
750 15220 : while (nDirEntries < nSegments)
751 0 : nDirEntries <<= 1; /* dir_alloc doubles dsize at each call */
752 :
753 : /* fixed control info */
754 15220 : size = MAXALIGN(sizeof(HASHHDR)); /* but not HTAB, per above */
755 : /* directory */
756 15220 : size = add_size(size, mul_size(nDirEntries, sizeof(HASHSEGMENT)));
757 : /* segments */
758 15220 : size = add_size(size, mul_size(nSegments,
759 : MAXALIGN(DEF_SEGSIZE * sizeof(HASHBUCKET))));
760 : /* elements --- allocated in groups of choose_nelem_alloc() entries */
761 15220 : elementAllocCnt = choose_nelem_alloc(entrysize);
762 15220 : nElementAllocs = (num_entries - 1) / elementAllocCnt + 1;
763 15220 : elementSize = MAXALIGN(sizeof(HASHELEMENT)) + MAXALIGN(entrysize);
764 15220 : size = add_size(size,
765 : mul_size(nElementAllocs,
766 : mul_size(elementAllocCnt, elementSize)));
767 :
768 15220 : return size;
769 : }
770 :
771 : /*
772 : * Select an appropriate directory size for a hashtable with the given
773 : * maximum number of entries.
774 : * This is only needed for hashtables in shared memory, whose directories
775 : * cannot be expanded dynamically.
776 : * NB: assumes that all hash structure parameters have default values!
777 : *
778 : * XXX this had better agree with the behavior of init_htab()...
779 : */
780 : long
781 15192 : hash_select_dirsize(long num_entries)
782 : {
783 : long nBuckets,
784 : nSegments,
785 : nDirEntries;
786 :
787 : /* estimate number of buckets wanted */
788 15192 : nBuckets = next_pow2_long((num_entries - 1) / DEF_FFACTOR + 1);
789 : /* # of segments needed for nBuckets */
790 15192 : nSegments = next_pow2_long((nBuckets - 1) / DEF_SEGSIZE + 1);
791 : /* directory entries */
792 15192 : nDirEntries = DEF_DIRSIZE;
793 15192 : while (nDirEntries < nSegments)
794 0 : nDirEntries <<= 1; /* dir_alloc doubles dsize at each call */
795 :
796 15192 : return nDirEntries;
797 : }
798 :
799 : /*
800 : * Compute the required initial memory allocation for a shared-memory
801 : * hashtable with the given parameters. We need space for the HASHHDR
802 : * and for the (non expansible) directory.
803 : */
804 : Size
805 15192 : hash_get_shared_size(HASHCTL *info, int flags)
806 : {
807 : Assert(flags & HASH_DIRSIZE);
808 : Assert(info->dsize == info->max_dsize);
809 15192 : return sizeof(HASHHDR) + info->dsize * sizeof(HASHSEGMENT);
810 : }
811 :
812 :
813 : /********************** DESTROY ROUTINES ************************/
814 :
815 : void
816 63252 : hash_destroy(HTAB *hashp)
817 : {
818 63252 : if (hashp != NULL)
819 : {
820 : /* allocation method must be one we know how to free, too */
821 : Assert(hashp->alloc == DynaHashAlloc);
822 : /* so this hashtable must have its own context */
823 : Assert(hashp->hcxt != NULL);
824 :
825 63252 : hash_stats("destroy", hashp);
826 :
827 : /*
828 : * Free everything by destroying the hash table's memory context.
829 : */
830 63252 : MemoryContextDelete(hashp->hcxt);
831 : }
832 63252 : }
833 :
834 : void
835 63252 : hash_stats(const char *where, HTAB *hashp)
836 : {
837 : #ifdef HASH_STATISTICS
838 : fprintf(stderr, "%s: this HTAB -- accesses %ld collisions %ld\n",
839 : where, hashp->hctl->accesses, hashp->hctl->collisions);
840 :
841 : fprintf(stderr, "hash_stats: entries %ld keysize %ld maxp %u segmentcount %ld\n",
842 : hash_get_num_entries(hashp), (long) hashp->hctl->keysize,
843 : hashp->hctl->max_bucket, hashp->hctl->nsegs);
844 : fprintf(stderr, "%s: total accesses %ld total collisions %ld\n",
845 : where, hash_accesses, hash_collisions);
846 : fprintf(stderr, "hash_stats: total expansions %ld\n",
847 : hash_expansions);
848 : #endif
849 63252 : }
850 :
851 : /*******************************SEARCH ROUTINES *****************************/
852 :
853 :
854 : /*
855 : * get_hash_value -- exported routine to calculate a key's hash value
856 : *
857 : * We export this because for partitioned tables, callers need to compute
858 : * the partition number (from the low-order bits of the hash value) before
859 : * searching.
860 : */
861 : uint32
862 122124554 : get_hash_value(HTAB *hashp, const void *keyPtr)
863 : {
864 122124554 : return hashp->hash(keyPtr, hashp->keysize);
865 : }
866 :
867 : /* Convert a hash value to a bucket number */
868 : static inline uint32
869 244957522 : calc_bucket(HASHHDR *hctl, uint32 hash_val)
870 : {
871 : uint32 bucket;
872 :
873 244957522 : bucket = hash_val & hctl->high_mask;
874 244957522 : if (bucket > hctl->max_bucket)
875 104315546 : bucket = bucket & hctl->low_mask;
876 :
877 244957522 : return bucket;
878 : }
879 :
880 : /*
881 : * hash_search -- look up key in table and perform action
882 : * hash_search_with_hash_value -- same, with key's hash value already computed
883 : *
884 : * action is one of:
885 : * HASH_FIND: look up key in table
886 : * HASH_ENTER: look up key in table, creating entry if not present
887 : * HASH_ENTER_NULL: same, but return NULL if out of memory
888 : * HASH_REMOVE: look up key in table, remove entry if present
889 : *
890 : * Return value is a pointer to the element found/entered/removed if any,
891 : * or NULL if no match was found. (NB: in the case of the REMOVE action,
892 : * the result is a dangling pointer that shouldn't be dereferenced!)
893 : *
894 : * HASH_ENTER will normally ereport a generic "out of memory" error if
895 : * it is unable to create a new entry. The HASH_ENTER_NULL operation is
896 : * the same except it will return NULL if out of memory. Note that
897 : * HASH_ENTER_NULL cannot be used with the default palloc-based allocator,
898 : * since palloc internally ereports on out-of-memory.
899 : *
900 : * If foundPtr isn't NULL, then *foundPtr is set true if we found an
901 : * existing entry in the table, false otherwise. This is needed in the
902 : * HASH_ENTER case, but is redundant with the return value otherwise.
903 : *
904 : * For hash_search_with_hash_value, the hashvalue parameter must have been
905 : * calculated with get_hash_value().
906 : */
907 : void *
908 138504480 : hash_search(HTAB *hashp,
909 : const void *keyPtr,
910 : HASHACTION action,
911 : bool *foundPtr)
912 : {
913 138504480 : return hash_search_with_hash_value(hashp,
914 : keyPtr,
915 138504480 : hashp->hash(keyPtr, hashp->keysize),
916 : action,
917 : foundPtr);
918 : }
919 :
920 : void *
921 244064112 : hash_search_with_hash_value(HTAB *hashp,
922 : const void *keyPtr,
923 : uint32 hashvalue,
924 : HASHACTION action,
925 : bool *foundPtr)
926 : {
927 244064112 : HASHHDR *hctl = hashp->hctl;
928 244064112 : int freelist_idx = FREELIST_IDX(hctl, hashvalue);
929 : Size keysize;
930 : uint32 bucket;
931 : long segment_num;
932 : long segment_ndx;
933 : HASHSEGMENT segp;
934 : HASHBUCKET currBucket;
935 : HASHBUCKET *prevBucketPtr;
936 : HashCompareFunc match;
937 :
938 : #ifdef HASH_STATISTICS
939 : hash_accesses++;
940 : hctl->accesses++;
941 : #endif
942 :
943 : /*
944 : * If inserting, check if it is time to split a bucket.
945 : *
946 : * NOTE: failure to expand table is not a fatal error, it just means we
947 : * have to run at higher fill factor than we wanted. However, if we're
948 : * using the palloc allocator then it will throw error anyway on
949 : * out-of-memory, so we must do this before modifying the table.
950 : */
951 244064112 : if (action == HASH_ENTER || action == HASH_ENTER_NULL)
952 : {
953 : /*
954 : * Can't split if running in partitioned mode, nor if frozen, nor if
955 : * table is the subject of any active hash_seq_search scans. Strange
956 : * order of these tests is to try to check cheaper conditions first.
957 : */
958 50172898 : if (!IS_PARTITIONED(hctl) && !hashp->frozen &&
959 43297850 : hctl->freeList[0].nentries / (long) (hctl->max_bucket + 1) >= hctl->ffactor &&
960 666400 : !has_seq_scans(hashp))
961 666400 : (void) expand_table(hashp);
962 : }
963 :
964 : /*
965 : * Do the initial lookup
966 : */
967 244064112 : bucket = calc_bucket(hctl, hashvalue);
968 :
969 244064112 : segment_num = bucket >> hashp->sshift;
970 244064112 : segment_ndx = MOD(bucket, hashp->ssize);
971 :
972 244064112 : segp = hashp->dir[segment_num];
973 :
974 244064112 : if (segp == NULL)
975 0 : hash_corrupted(hashp);
976 :
977 244064112 : prevBucketPtr = &segp[segment_ndx];
978 244064112 : currBucket = *prevBucketPtr;
979 :
980 : /*
981 : * Follow collision chain looking for matching key
982 : */
983 244064112 : match = hashp->match; /* save one fetch in inner loop */
984 244064112 : keysize = hashp->keysize; /* ditto */
985 :
986 284507784 : while (currBucket != NULL)
987 : {
988 437838168 : if (currBucket->hashvalue == hashvalue &&
989 198700404 : match(ELEMENTKEY(currBucket), keyPtr, keysize) == 0)
990 198694092 : break;
991 40443672 : prevBucketPtr = &(currBucket->link);
992 40443672 : currBucket = *prevBucketPtr;
993 : #ifdef HASH_STATISTICS
994 : hash_collisions++;
995 : hctl->collisions++;
996 : #endif
997 : }
998 :
999 244064112 : if (foundPtr)
1000 49697354 : *foundPtr = (bool) (currBucket != NULL);
1001 :
1002 : /*
1003 : * OK, now what?
1004 : */
1005 244064112 : switch (action)
1006 : {
1007 159155504 : case HASH_FIND:
1008 159155504 : if (currBucket != NULL)
1009 154523840 : return (void *) ELEMENTKEY(currBucket);
1010 4631664 : return NULL;
1011 :
1012 34735710 : case HASH_REMOVE:
1013 34735710 : if (currBucket != NULL)
1014 : {
1015 : /* if partitioned, must lock to touch nentries and freeList */
1016 34656668 : if (IS_PARTITIONED(hctl))
1017 5052850 : SpinLockAcquire(&(hctl->freeList[freelist_idx].mutex));
1018 :
1019 : /* delete the record from the appropriate nentries counter. */
1020 : Assert(hctl->freeList[freelist_idx].nentries > 0);
1021 34656668 : hctl->freeList[freelist_idx].nentries--;
1022 :
1023 : /* remove record from hash bucket's chain. */
1024 34656668 : *prevBucketPtr = currBucket->link;
1025 :
1026 : /* add the record to the appropriate freelist. */
1027 34656668 : currBucket->link = hctl->freeList[freelist_idx].freeList;
1028 34656668 : hctl->freeList[freelist_idx].freeList = currBucket;
1029 :
1030 34656668 : if (IS_PARTITIONED(hctl))
1031 5052850 : SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1032 :
1033 : /*
1034 : * better hope the caller is synchronizing access to this
1035 : * element, because someone else is going to reuse it the next
1036 : * time something is added to the table
1037 : */
1038 34656668 : return (void *) ELEMENTKEY(currBucket);
1039 : }
1040 79042 : return NULL;
1041 :
1042 50172898 : case HASH_ENTER_NULL:
1043 : /* ENTER_NULL does not work with palloc-based allocator */
1044 : Assert(hashp->alloc != DynaHashAlloc);
1045 : /* FALL THRU */
1046 :
1047 : case HASH_ENTER:
1048 : /* Return existing element if found, else create one */
1049 50172898 : if (currBucket != NULL)
1050 9513584 : return (void *) ELEMENTKEY(currBucket);
1051 :
1052 : /* disallow inserts if frozen */
1053 40659314 : if (hashp->frozen)
1054 0 : elog(ERROR, "cannot insert into frozen hashtable \"%s\"",
1055 : hashp->tabname);
1056 :
1057 40659314 : currBucket = get_hash_entry(hashp, freelist_idx);
1058 40659314 : if (currBucket == NULL)
1059 : {
1060 : /* out of memory */
1061 0 : if (action == HASH_ENTER_NULL)
1062 0 : return NULL;
1063 : /* report a generic message */
1064 0 : if (hashp->isshared)
1065 0 : ereport(ERROR,
1066 : (errcode(ERRCODE_OUT_OF_MEMORY),
1067 : errmsg("out of shared memory")));
1068 : else
1069 0 : ereport(ERROR,
1070 : (errcode(ERRCODE_OUT_OF_MEMORY),
1071 : errmsg("out of memory")));
1072 : }
1073 :
1074 : /* link into hashbucket chain */
1075 40659314 : *prevBucketPtr = currBucket;
1076 40659314 : currBucket->link = NULL;
1077 :
1078 : /* copy key into record */
1079 40659314 : currBucket->hashvalue = hashvalue;
1080 40659314 : hashp->keycopy(ELEMENTKEY(currBucket), keyPtr, keysize);
1081 :
1082 : /*
1083 : * Caller is expected to fill the data field on return. DO NOT
1084 : * insert any code that could possibly throw error here, as doing
1085 : * so would leave the table entry incomplete and hence corrupt the
1086 : * caller's data structure.
1087 : */
1088 :
1089 40659314 : return (void *) ELEMENTKEY(currBucket);
1090 : }
1091 :
1092 0 : elog(ERROR, "unrecognized hash action code: %d", (int) action);
1093 :
1094 : return NULL; /* keep compiler quiet */
1095 : }
1096 :
1097 : /*
1098 : * hash_update_hash_key -- change the hash key of an existing table entry
1099 : *
1100 : * This is equivalent to removing the entry, making a new entry, and copying
1101 : * over its data, except that the entry never goes to the table's freelist.
1102 : * Therefore this cannot suffer an out-of-memory failure, even if there are
1103 : * other processes operating in other partitions of the hashtable.
1104 : *
1105 : * Returns true if successful, false if the requested new hash key is already
1106 : * present. Throws error if the specified entry pointer isn't actually a
1107 : * table member.
1108 : *
1109 : * NB: currently, there is no special case for old and new hash keys being
1110 : * identical, which means we'll report false for that situation. This is
1111 : * preferable for existing uses.
1112 : *
1113 : * NB: for a partitioned hashtable, caller must hold lock on both relevant
1114 : * partitions, if the new hash key would belong to a different partition.
1115 : */
1116 : bool
1117 196 : hash_update_hash_key(HTAB *hashp,
1118 : void *existingEntry,
1119 : const void *newKeyPtr)
1120 : {
1121 196 : HASHELEMENT *existingElement = ELEMENT_FROM_KEY(existingEntry);
1122 196 : HASHHDR *hctl = hashp->hctl;
1123 : uint32 newhashvalue;
1124 : Size keysize;
1125 : uint32 bucket;
1126 : uint32 newbucket;
1127 : long segment_num;
1128 : long segment_ndx;
1129 : HASHSEGMENT segp;
1130 : HASHBUCKET currBucket;
1131 : HASHBUCKET *prevBucketPtr;
1132 : HASHBUCKET *oldPrevPtr;
1133 : HashCompareFunc match;
1134 :
1135 : #ifdef HASH_STATISTICS
1136 : hash_accesses++;
1137 : hctl->accesses++;
1138 : #endif
1139 :
1140 : /* disallow updates if frozen */
1141 196 : if (hashp->frozen)
1142 0 : elog(ERROR, "cannot update in frozen hashtable \"%s\"",
1143 : hashp->tabname);
1144 :
1145 : /*
1146 : * Lookup the existing element using its saved hash value. We need to do
1147 : * this to be able to unlink it from its hash chain, but as a side benefit
1148 : * we can verify the validity of the passed existingEntry pointer.
1149 : */
1150 196 : bucket = calc_bucket(hctl, existingElement->hashvalue);
1151 :
1152 196 : segment_num = bucket >> hashp->sshift;
1153 196 : segment_ndx = MOD(bucket, hashp->ssize);
1154 :
1155 196 : segp = hashp->dir[segment_num];
1156 :
1157 196 : if (segp == NULL)
1158 0 : hash_corrupted(hashp);
1159 :
1160 196 : prevBucketPtr = &segp[segment_ndx];
1161 196 : currBucket = *prevBucketPtr;
1162 :
1163 196 : while (currBucket != NULL)
1164 : {
1165 196 : if (currBucket == existingElement)
1166 196 : break;
1167 0 : prevBucketPtr = &(currBucket->link);
1168 0 : currBucket = *prevBucketPtr;
1169 : }
1170 :
1171 196 : if (currBucket == NULL)
1172 0 : elog(ERROR, "hash_update_hash_key argument is not in hashtable \"%s\"",
1173 : hashp->tabname);
1174 :
1175 196 : oldPrevPtr = prevBucketPtr;
1176 :
1177 : /*
1178 : * Now perform the equivalent of a HASH_ENTER operation to locate the hash
1179 : * chain we want to put the entry into.
1180 : */
1181 196 : newhashvalue = hashp->hash(newKeyPtr, hashp->keysize);
1182 :
1183 196 : newbucket = calc_bucket(hctl, newhashvalue);
1184 :
1185 196 : segment_num = newbucket >> hashp->sshift;
1186 196 : segment_ndx = MOD(newbucket, hashp->ssize);
1187 :
1188 196 : segp = hashp->dir[segment_num];
1189 :
1190 196 : if (segp == NULL)
1191 0 : hash_corrupted(hashp);
1192 :
1193 196 : prevBucketPtr = &segp[segment_ndx];
1194 196 : currBucket = *prevBucketPtr;
1195 :
1196 : /*
1197 : * Follow collision chain looking for matching key
1198 : */
1199 196 : match = hashp->match; /* save one fetch in inner loop */
1200 196 : keysize = hashp->keysize; /* ditto */
1201 :
1202 196 : while (currBucket != NULL)
1203 : {
1204 0 : if (currBucket->hashvalue == newhashvalue &&
1205 0 : match(ELEMENTKEY(currBucket), newKeyPtr, keysize) == 0)
1206 0 : break;
1207 0 : prevBucketPtr = &(currBucket->link);
1208 0 : currBucket = *prevBucketPtr;
1209 : #ifdef HASH_STATISTICS
1210 : hash_collisions++;
1211 : hctl->collisions++;
1212 : #endif
1213 : }
1214 :
1215 196 : if (currBucket != NULL)
1216 0 : return false; /* collision with an existing entry */
1217 :
1218 196 : currBucket = existingElement;
1219 :
1220 : /*
1221 : * If old and new hash values belong to the same bucket, we need not
1222 : * change any chain links, and indeed should not since this simplistic
1223 : * update will corrupt the list if currBucket is the last element. (We
1224 : * cannot fall out earlier, however, since we need to scan the bucket to
1225 : * check for duplicate keys.)
1226 : */
1227 196 : if (bucket != newbucket)
1228 : {
1229 : /* OK to remove record from old hash bucket's chain. */
1230 196 : *oldPrevPtr = currBucket->link;
1231 :
1232 : /* link into new hashbucket chain */
1233 196 : *prevBucketPtr = currBucket;
1234 196 : currBucket->link = NULL;
1235 : }
1236 :
1237 : /* copy new key into record */
1238 196 : currBucket->hashvalue = newhashvalue;
1239 196 : hashp->keycopy(ELEMENTKEY(currBucket), newKeyPtr, keysize);
1240 :
1241 : /* rest of record is untouched */
1242 :
1243 196 : return true;
1244 : }
1245 :
1246 : /*
1247 : * Allocate a new hashtable entry if possible; return NULL if out of memory.
1248 : * (Or, if the underlying space allocator throws error for out-of-memory,
1249 : * we won't return at all.)
1250 : */
1251 : static HASHBUCKET
1252 40659314 : get_hash_entry(HTAB *hashp, int freelist_idx)
1253 : {
1254 40659314 : HASHHDR *hctl = hashp->hctl;
1255 : HASHBUCKET newElement;
1256 :
1257 : for (;;)
1258 : {
1259 : /* if partitioned, must lock to touch nentries and freeList */
1260 40944496 : if (IS_PARTITIONED(hctl))
1261 5746856 : SpinLockAcquire(&hctl->freeList[freelist_idx].mutex);
1262 :
1263 : /* try to get an entry from the freelist */
1264 40944496 : newElement = hctl->freeList[freelist_idx].freeList;
1265 :
1266 40944496 : if (newElement != NULL)
1267 40659314 : break;
1268 :
1269 285182 : if (IS_PARTITIONED(hctl))
1270 588 : SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1271 :
1272 : /*
1273 : * No free elements in this freelist. In a partitioned table, there
1274 : * might be entries in other freelists, but to reduce contention we
1275 : * prefer to first try to get another chunk of buckets from the main
1276 : * shmem allocator. If that fails, though, we *MUST* root through all
1277 : * the other freelists before giving up. There are multiple callers
1278 : * that assume that they can allocate every element in the initially
1279 : * requested table size, or that deleting an element guarantees they
1280 : * can insert a new element, even if shared memory is entirely full.
1281 : * Failing because the needed element is in a different freelist is
1282 : * not acceptable.
1283 : */
1284 285182 : if (!element_alloc(hashp, hctl->nelem_alloc, freelist_idx))
1285 : {
1286 : int borrow_from_idx;
1287 :
1288 0 : if (!IS_PARTITIONED(hctl))
1289 0 : return NULL; /* out of memory */
1290 :
1291 : /* try to borrow element from another freelist */
1292 0 : borrow_from_idx = freelist_idx;
1293 : for (;;)
1294 : {
1295 0 : borrow_from_idx = (borrow_from_idx + 1) % NUM_FREELISTS;
1296 0 : if (borrow_from_idx == freelist_idx)
1297 0 : break; /* examined all freelists, fail */
1298 :
1299 0 : SpinLockAcquire(&(hctl->freeList[borrow_from_idx].mutex));
1300 0 : newElement = hctl->freeList[borrow_from_idx].freeList;
1301 :
1302 0 : if (newElement != NULL)
1303 : {
1304 0 : hctl->freeList[borrow_from_idx].freeList = newElement->link;
1305 0 : SpinLockRelease(&(hctl->freeList[borrow_from_idx].mutex));
1306 :
1307 : /* careful: count the new element in its proper freelist */
1308 0 : SpinLockAcquire(&hctl->freeList[freelist_idx].mutex);
1309 0 : hctl->freeList[freelist_idx].nentries++;
1310 0 : SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1311 :
1312 0 : return newElement;
1313 : }
1314 :
1315 0 : SpinLockRelease(&(hctl->freeList[borrow_from_idx].mutex));
1316 : }
1317 :
1318 : /* no elements available to borrow either, so out of memory */
1319 0 : return NULL;
1320 : }
1321 : }
1322 :
1323 : /* remove entry from freelist, bump nentries */
1324 40659314 : hctl->freeList[freelist_idx].freeList = newElement->link;
1325 40659314 : hctl->freeList[freelist_idx].nentries++;
1326 :
1327 40659314 : if (IS_PARTITIONED(hctl))
1328 5746268 : SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1329 :
1330 40659314 : return newElement;
1331 : }
1332 :
1333 : /*
1334 : * hash_get_num_entries -- get the number of entries in a hashtable
1335 : */
1336 : long
1337 11286 : hash_get_num_entries(HTAB *hashp)
1338 : {
1339 : int i;
1340 11286 : long sum = hashp->hctl->freeList[0].nentries;
1341 :
1342 : /*
1343 : * We currently don't bother with acquiring the mutexes; it's only
1344 : * sensible to call this function if you've got lock on all partitions of
1345 : * the table.
1346 : */
1347 11286 : if (IS_PARTITIONED(hashp->hctl))
1348 : {
1349 87488 : for (i = 1; i < NUM_FREELISTS; i++)
1350 84754 : sum += hashp->hctl->freeList[i].nentries;
1351 : }
1352 :
1353 11286 : return sum;
1354 : }
1355 :
1356 : /*
1357 : * hash_seq_init/_search/_term
1358 : * Sequentially search through hash table and return
1359 : * all the elements one by one, return NULL when no more.
1360 : *
1361 : * hash_seq_term should be called if and only if the scan is abandoned before
1362 : * completion; if hash_seq_search returns NULL then it has already done the
1363 : * end-of-scan cleanup.
1364 : *
1365 : * NOTE: caller may delete the returned element before continuing the scan.
1366 : * However, deleting any other element while the scan is in progress is
1367 : * UNDEFINED (it might be the one that curIndex is pointing at!). Also,
1368 : * if elements are added to the table while the scan is in progress, it is
1369 : * unspecified whether they will be visited by the scan or not.
1370 : *
1371 : * NOTE: it is possible to use hash_seq_init/hash_seq_search without any
1372 : * worry about hash_seq_term cleanup, if the hashtable is first locked against
1373 : * further insertions by calling hash_freeze.
1374 : *
1375 : * NOTE: to use this with a partitioned hashtable, caller had better hold
1376 : * at least shared lock on all partitions of the table throughout the scan!
1377 : * We can cope with insertions or deletions by our own backend, but *not*
1378 : * with concurrent insertions or deletions by another.
1379 : */
1380 : void
1381 3370638 : hash_seq_init(HASH_SEQ_STATUS *status, HTAB *hashp)
1382 : {
1383 3370638 : status->hashp = hashp;
1384 3370638 : status->curBucket = 0;
1385 3370638 : status->curEntry = NULL;
1386 3370638 : if (!hashp->frozen)
1387 3370638 : register_seq_scan(hashp);
1388 3370638 : }
1389 :
1390 : void *
1391 32055814 : hash_seq_search(HASH_SEQ_STATUS *status)
1392 : {
1393 : HTAB *hashp;
1394 : HASHHDR *hctl;
1395 : uint32 max_bucket;
1396 : long ssize;
1397 : long segment_num;
1398 : long segment_ndx;
1399 : HASHSEGMENT segp;
1400 : uint32 curBucket;
1401 : HASHELEMENT *curElem;
1402 :
1403 32055814 : if ((curElem = status->curEntry) != NULL)
1404 : {
1405 : /* Continuing scan of curBucket... */
1406 5947820 : status->curEntry = curElem->link;
1407 5947820 : if (status->curEntry == NULL) /* end of this bucket */
1408 4554106 : ++status->curBucket;
1409 5947820 : return (void *) ELEMENTKEY(curElem);
1410 : }
1411 :
1412 : /*
1413 : * Search for next nonempty bucket starting at curBucket.
1414 : */
1415 26107994 : curBucket = status->curBucket;
1416 26107994 : hashp = status->hashp;
1417 26107994 : hctl = hashp->hctl;
1418 26107994 : ssize = hashp->ssize;
1419 26107994 : max_bucket = hctl->max_bucket;
1420 :
1421 26107994 : if (curBucket > max_bucket)
1422 : {
1423 120714 : hash_seq_term(status);
1424 120714 : return NULL; /* search is done */
1425 : }
1426 :
1427 : /*
1428 : * first find the right segment in the table directory.
1429 : */
1430 25987280 : segment_num = curBucket >> hashp->sshift;
1431 25987280 : segment_ndx = MOD(curBucket, ssize);
1432 :
1433 25987280 : segp = hashp->dir[segment_num];
1434 :
1435 : /*
1436 : * Pick up the first item in this bucket's chain. If chain is not empty
1437 : * we can begin searching it. Otherwise we have to advance to find the
1438 : * next nonempty bucket. We try to optimize that case since searching a
1439 : * near-empty hashtable has to iterate this loop a lot.
1440 : */
1441 252765698 : while ((curElem = segp[segment_ndx]) == NULL)
1442 : {
1443 : /* empty bucket, advance to next */
1444 229995668 : if (++curBucket > max_bucket)
1445 : {
1446 3217250 : status->curBucket = curBucket;
1447 3217250 : hash_seq_term(status);
1448 3217250 : return NULL; /* search is done */
1449 : }
1450 226778418 : if (++segment_ndx >= ssize)
1451 : {
1452 159414 : segment_num++;
1453 159414 : segment_ndx = 0;
1454 159414 : segp = hashp->dir[segment_num];
1455 : }
1456 : }
1457 :
1458 : /* Begin scan of curBucket... */
1459 22770030 : status->curEntry = curElem->link;
1460 22770030 : if (status->curEntry == NULL) /* end of this bucket */
1461 18215900 : ++curBucket;
1462 22770030 : status->curBucket = curBucket;
1463 22770030 : return (void *) ELEMENTKEY(curElem);
1464 : }
1465 :
1466 : void
1467 3370630 : hash_seq_term(HASH_SEQ_STATUS *status)
1468 : {
1469 3370630 : if (!status->hashp->frozen)
1470 3370630 : deregister_seq_scan(status->hashp);
1471 3370630 : }
1472 :
1473 : /*
1474 : * hash_freeze
1475 : * Freeze a hashtable against future insertions (deletions are
1476 : * still allowed)
1477 : *
1478 : * The reason for doing this is that by preventing any more bucket splits,
1479 : * we no longer need to worry about registering hash_seq_search scans,
1480 : * and thus caller need not be careful about ensuring hash_seq_term gets
1481 : * called at the right times.
1482 : *
1483 : * Multiple calls to hash_freeze() are allowed, but you can't freeze a table
1484 : * with active scans (since hash_seq_term would then do the wrong thing).
1485 : */
1486 : void
1487 0 : hash_freeze(HTAB *hashp)
1488 : {
1489 0 : if (hashp->isshared)
1490 0 : elog(ERROR, "cannot freeze shared hashtable \"%s\"", hashp->tabname);
1491 0 : if (!hashp->frozen && has_seq_scans(hashp))
1492 0 : elog(ERROR, "cannot freeze hashtable \"%s\" because it has active scans",
1493 : hashp->tabname);
1494 0 : hashp->frozen = true;
1495 0 : }
1496 :
1497 :
1498 : /********************************* UTILITIES ************************/
1499 :
1500 : /*
1501 : * Expand the table by adding one more hash bucket.
1502 : */
1503 : static bool
1504 666400 : expand_table(HTAB *hashp)
1505 : {
1506 666400 : HASHHDR *hctl = hashp->hctl;
1507 : HASHSEGMENT old_seg,
1508 : new_seg;
1509 : long old_bucket,
1510 : new_bucket;
1511 : long new_segnum,
1512 : new_segndx;
1513 : long old_segnum,
1514 : old_segndx;
1515 : HASHBUCKET *oldlink,
1516 : *newlink;
1517 : HASHBUCKET currElement,
1518 : nextElement;
1519 :
1520 : Assert(!IS_PARTITIONED(hctl));
1521 :
1522 : #ifdef HASH_STATISTICS
1523 : hash_expansions++;
1524 : #endif
1525 :
1526 666400 : new_bucket = hctl->max_bucket + 1;
1527 666400 : new_segnum = new_bucket >> hashp->sshift;
1528 666400 : new_segndx = MOD(new_bucket, hashp->ssize);
1529 :
1530 666400 : if (new_segnum >= hctl->nsegs)
1531 : {
1532 : /* Allocate new segment if necessary -- could fail if dir full */
1533 2998 : if (new_segnum >= hctl->dsize)
1534 0 : if (!dir_realloc(hashp))
1535 0 : return false;
1536 2998 : if (!(hashp->dir[new_segnum] = seg_alloc(hashp)))
1537 0 : return false;
1538 2998 : hctl->nsegs++;
1539 : }
1540 :
1541 : /* OK, we created a new bucket */
1542 666400 : hctl->max_bucket++;
1543 :
1544 : /*
1545 : * *Before* changing masks, find old bucket corresponding to same hash
1546 : * values; values in that bucket may need to be relocated to new bucket.
1547 : * Note that new_bucket is certainly larger than low_mask at this point,
1548 : * so we can skip the first step of the regular hash mask calc.
1549 : */
1550 666400 : old_bucket = (new_bucket & hctl->low_mask);
1551 :
1552 : /*
1553 : * If we crossed a power of 2, readjust masks.
1554 : */
1555 666400 : if ((uint32) new_bucket > hctl->high_mask)
1556 : {
1557 3772 : hctl->low_mask = hctl->high_mask;
1558 3772 : hctl->high_mask = (uint32) new_bucket | hctl->low_mask;
1559 : }
1560 :
1561 : /*
1562 : * Relocate records to the new bucket. NOTE: because of the way the hash
1563 : * masking is done in calc_bucket, only one old bucket can need to be
1564 : * split at this point. With a different way of reducing the hash value,
1565 : * that might not be true!
1566 : */
1567 666400 : old_segnum = old_bucket >> hashp->sshift;
1568 666400 : old_segndx = MOD(old_bucket, hashp->ssize);
1569 :
1570 666400 : old_seg = hashp->dir[old_segnum];
1571 666400 : new_seg = hashp->dir[new_segnum];
1572 :
1573 666400 : oldlink = &old_seg[old_segndx];
1574 666400 : newlink = &new_seg[new_segndx];
1575 :
1576 1559418 : for (currElement = *oldlink;
1577 : currElement != NULL;
1578 893018 : currElement = nextElement)
1579 : {
1580 893018 : nextElement = currElement->link;
1581 893018 : if ((long) calc_bucket(hctl, currElement->hashvalue) == old_bucket)
1582 : {
1583 457424 : *oldlink = currElement;
1584 457424 : oldlink = &currElement->link;
1585 : }
1586 : else
1587 : {
1588 435594 : *newlink = currElement;
1589 435594 : newlink = &currElement->link;
1590 : }
1591 : }
1592 : /* don't forget to terminate the rebuilt hash chains... */
1593 666400 : *oldlink = NULL;
1594 666400 : *newlink = NULL;
1595 :
1596 666400 : return true;
1597 : }
1598 :
1599 :
1600 : static bool
1601 0 : dir_realloc(HTAB *hashp)
1602 : {
1603 : HASHSEGMENT *p;
1604 : HASHSEGMENT *old_p;
1605 : long new_dsize;
1606 : long old_dirsize;
1607 : long new_dirsize;
1608 :
1609 0 : if (hashp->hctl->max_dsize != NO_MAX_DSIZE)
1610 0 : return false;
1611 :
1612 : /* Reallocate directory */
1613 0 : new_dsize = hashp->hctl->dsize << 1;
1614 0 : old_dirsize = hashp->hctl->dsize * sizeof(HASHSEGMENT);
1615 0 : new_dirsize = new_dsize * sizeof(HASHSEGMENT);
1616 :
1617 0 : old_p = hashp->dir;
1618 0 : CurrentDynaHashCxt = hashp->hcxt;
1619 0 : p = (HASHSEGMENT *) hashp->alloc((Size) new_dirsize);
1620 :
1621 0 : if (p != NULL)
1622 : {
1623 0 : memcpy(p, old_p, old_dirsize);
1624 0 : MemSet(((char *) p) + old_dirsize, 0, new_dirsize - old_dirsize);
1625 0 : hashp->dir = p;
1626 0 : hashp->hctl->dsize = new_dsize;
1627 :
1628 : /* XXX assume the allocator is palloc, so we know how to free */
1629 : Assert(hashp->alloc == DynaHashAlloc);
1630 0 : pfree(old_p);
1631 :
1632 0 : return true;
1633 : }
1634 :
1635 0 : return false;
1636 : }
1637 :
1638 :
1639 : static HASHSEGMENT
1640 815186 : seg_alloc(HTAB *hashp)
1641 : {
1642 : HASHSEGMENT segp;
1643 :
1644 815186 : CurrentDynaHashCxt = hashp->hcxt;
1645 815186 : segp = (HASHSEGMENT) hashp->alloc(sizeof(HASHBUCKET) * hashp->ssize);
1646 :
1647 815186 : if (!segp)
1648 0 : return NULL;
1649 :
1650 815186 : MemSet(segp, 0, sizeof(HASHBUCKET) * hashp->ssize);
1651 :
1652 815186 : return segp;
1653 : }
1654 :
1655 : /*
1656 : * allocate some new elements and link them into the indicated free list
1657 : */
1658 : static bool
1659 704166 : element_alloc(HTAB *hashp, int nelem, int freelist_idx)
1660 : {
1661 704166 : HASHHDR *hctl = hashp->hctl;
1662 : Size elementSize;
1663 : HASHELEMENT *firstElement;
1664 : HASHELEMENT *tmpElement;
1665 : HASHELEMENT *prevElement;
1666 : int i;
1667 :
1668 704166 : if (hashp->isfixed)
1669 0 : return false;
1670 :
1671 : /* Each element has a HASHELEMENT header plus user data. */
1672 704166 : elementSize = MAXALIGN(sizeof(HASHELEMENT)) + MAXALIGN(hctl->entrysize);
1673 :
1674 704166 : CurrentDynaHashCxt = hashp->hcxt;
1675 704166 : firstElement = (HASHELEMENT *) hashp->alloc(nelem * elementSize);
1676 :
1677 704166 : if (!firstElement)
1678 0 : return false;
1679 :
1680 : /* prepare to link all the new entries into the freelist */
1681 704166 : prevElement = NULL;
1682 704166 : tmpElement = firstElement;
1683 104971188 : for (i = 0; i < nelem; i++)
1684 : {
1685 104267022 : tmpElement->link = prevElement;
1686 104267022 : prevElement = tmpElement;
1687 104267022 : tmpElement = (HASHELEMENT *) (((char *) tmpElement) + elementSize);
1688 : }
1689 :
1690 : /* if partitioned, must lock to touch freeList */
1691 704166 : if (IS_PARTITIONED(hctl))
1692 347788 : SpinLockAcquire(&hctl->freeList[freelist_idx].mutex);
1693 :
1694 : /* freelist could be nonempty if two backends did this concurrently */
1695 704166 : firstElement->link = hctl->freeList[freelist_idx].freeList;
1696 704166 : hctl->freeList[freelist_idx].freeList = prevElement;
1697 :
1698 704166 : if (IS_PARTITIONED(hctl))
1699 347788 : SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1700 :
1701 704166 : return true;
1702 : }
1703 :
1704 : /* complain when we have detected a corrupted hashtable */
1705 : static void
1706 0 : hash_corrupted(HTAB *hashp)
1707 : {
1708 : /*
1709 : * If the corruption is in a shared hashtable, we'd better force a
1710 : * systemwide restart. Otherwise, just shut down this one backend.
1711 : */
1712 0 : if (hashp->isshared)
1713 0 : elog(PANIC, "hash table \"%s\" corrupted", hashp->tabname);
1714 : else
1715 0 : elog(FATAL, "hash table \"%s\" corrupted", hashp->tabname);
1716 : }
1717 :
1718 : /* calculate ceil(log base 2) of num */
1719 : int
1720 2028518 : my_log2(long num)
1721 : {
1722 : /*
1723 : * guard against too-large input, which would be invalid for
1724 : * pg_ceil_log2_*()
1725 : */
1726 2028518 : if (num > LONG_MAX / 2)
1727 0 : num = LONG_MAX / 2;
1728 :
1729 : #if SIZEOF_LONG < 8
1730 : return pg_ceil_log2_32(num);
1731 : #else
1732 2028518 : return pg_ceil_log2_64(num);
1733 : #endif
1734 : }
1735 :
1736 : /* calculate first power of 2 >= num, bounded to what will fit in a long */
1737 : static long
1738 60824 : next_pow2_long(long num)
1739 : {
1740 : /* my_log2's internal range check is sufficient */
1741 60824 : return 1L << my_log2(num);
1742 : }
1743 :
1744 : /* calculate first power of 2 >= num, bounded to what will fit in an int */
1745 : static int
1746 561244 : next_pow2_int(long num)
1747 : {
1748 561244 : if (num > INT_MAX / 2)
1749 0 : num = INT_MAX / 2;
1750 561244 : return 1 << my_log2(num);
1751 : }
1752 :
1753 :
1754 : /************************* SEQ SCAN TRACKING ************************/
1755 :
1756 : /*
1757 : * We track active hash_seq_search scans here. The need for this mechanism
1758 : * comes from the fact that a scan will get confused if a bucket split occurs
1759 : * while it's in progress: it might visit entries twice, or even miss some
1760 : * entirely (if it's partway through the same bucket that splits). Hence
1761 : * we want to inhibit bucket splits if there are any active scans on the
1762 : * table being inserted into. This is a fairly rare case in current usage,
1763 : * so just postponing the split until the next insertion seems sufficient.
1764 : *
1765 : * Given present usages of the function, only a few scans are likely to be
1766 : * open concurrently; so a finite-size stack of open scans seems sufficient,
1767 : * and we don't worry that linear search is too slow. Note that we do
1768 : * allow multiple scans of the same hashtable to be open concurrently.
1769 : *
1770 : * This mechanism can support concurrent scan and insertion in a shared
1771 : * hashtable if it's the same backend doing both. It would fail otherwise,
1772 : * but locking reasons seem to preclude any such scenario anyway, so we don't
1773 : * worry.
1774 : *
1775 : * This arrangement is reasonably robust if a transient hashtable is deleted
1776 : * without notifying us. The absolute worst case is we might inhibit splits
1777 : * in another table created later at exactly the same address. We will give
1778 : * a warning at transaction end for reference leaks, so any bugs leading to
1779 : * lack of notification should be easy to catch.
1780 : */
1781 :
1782 : #define MAX_SEQ_SCANS 100
1783 :
1784 : static HTAB *seq_scan_tables[MAX_SEQ_SCANS]; /* tables being scanned */
1785 : static int seq_scan_level[MAX_SEQ_SCANS]; /* subtransaction nest level */
1786 : static int num_seq_scans = 0;
1787 :
1788 :
1789 : /* Register a table as having an active hash_seq_search scan */
1790 : static void
1791 3370638 : register_seq_scan(HTAB *hashp)
1792 : {
1793 3370638 : if (num_seq_scans >= MAX_SEQ_SCANS)
1794 0 : elog(ERROR, "too many active hash_seq_search scans, cannot start one on \"%s\"",
1795 : hashp->tabname);
1796 3370638 : seq_scan_tables[num_seq_scans] = hashp;
1797 3370638 : seq_scan_level[num_seq_scans] = GetCurrentTransactionNestLevel();
1798 3370638 : num_seq_scans++;
1799 3370638 : }
1800 :
1801 : /* Deregister an active scan */
1802 : static void
1803 3370630 : deregister_seq_scan(HTAB *hashp)
1804 : {
1805 : int i;
1806 :
1807 : /* Search backward since it's most likely at the stack top */
1808 3370630 : for (i = num_seq_scans - 1; i >= 0; i--)
1809 : {
1810 3370630 : if (seq_scan_tables[i] == hashp)
1811 : {
1812 3370630 : seq_scan_tables[i] = seq_scan_tables[num_seq_scans - 1];
1813 3370630 : seq_scan_level[i] = seq_scan_level[num_seq_scans - 1];
1814 3370630 : num_seq_scans--;
1815 3370630 : return;
1816 : }
1817 : }
1818 0 : elog(ERROR, "no hash_seq_search scan for hash table \"%s\"",
1819 : hashp->tabname);
1820 : }
1821 :
1822 : /* Check if a table has any active scan */
1823 : static bool
1824 666400 : has_seq_scans(HTAB *hashp)
1825 : {
1826 : int i;
1827 :
1828 666400 : for (i = 0; i < num_seq_scans; i++)
1829 : {
1830 0 : if (seq_scan_tables[i] == hashp)
1831 0 : return true;
1832 : }
1833 666400 : return false;
1834 : }
1835 :
1836 : /* Clean up any open scans at end of transaction */
1837 : void
1838 494980 : AtEOXact_HashTables(bool isCommit)
1839 : {
1840 : /*
1841 : * During abort cleanup, open scans are expected; just silently clean 'em
1842 : * out. An open scan at commit means someone forgot a hash_seq_term()
1843 : * call, so complain.
1844 : *
1845 : * Note: it's tempting to try to print the tabname here, but refrain for
1846 : * fear of touching deallocated memory. This isn't a user-facing message
1847 : * anyway, so it needn't be pretty.
1848 : */
1849 494980 : if (isCommit)
1850 : {
1851 : int i;
1852 :
1853 474638 : for (i = 0; i < num_seq_scans; i++)
1854 : {
1855 0 : elog(WARNING, "leaked hash_seq_search scan for hash table %p",
1856 : seq_scan_tables[i]);
1857 : }
1858 : }
1859 494980 : num_seq_scans = 0;
1860 494980 : }
1861 :
1862 : /* Clean up any open scans at end of subtransaction */
1863 : void
1864 7664 : AtEOSubXact_HashTables(bool isCommit, int nestDepth)
1865 : {
1866 : int i;
1867 :
1868 : /*
1869 : * Search backward to make cleanup easy. Note we must check all entries,
1870 : * not only those at the end of the array, because deletion technique
1871 : * doesn't keep them in order.
1872 : */
1873 7664 : for (i = num_seq_scans - 1; i >= 0; i--)
1874 : {
1875 0 : if (seq_scan_level[i] >= nestDepth)
1876 : {
1877 0 : if (isCommit)
1878 0 : elog(WARNING, "leaked hash_seq_search scan for hash table %p",
1879 : seq_scan_tables[i]);
1880 0 : seq_scan_tables[i] = seq_scan_tables[num_seq_scans - 1];
1881 0 : seq_scan_level[i] = seq_scan_level[num_seq_scans - 1];
1882 0 : num_seq_scans--;
1883 : }
1884 : }
1885 7664 : }
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