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dynahash.c
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1 /*-------------------------------------------------------------------------
2  *
3  * dynahash.c
4  * dynamic chained 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 selected by specifying the
34  * HASH_STRINGS flag to hash_create.
35  *
36  * 2. Arbitrary binary data of size keysize, compared as though by memcmp().
37  * (Caller must ensure there are no undefined padding bits in the keys!)
38  * This is selected by specifying the HASH_BLOBS flag to hash_create.
39  *
40  * 3. More complex key behavior can be selected by specifying user-supplied
41  * hashing, comparison, and/or key-copying functions. At least a hashing
42  * function must be supplied; comparison defaults to memcmp() and key copying
43  * to memcpy() when a user-defined hashing function is selected.
44  *
45  * Compared to simplehash, dynahash has the following benefits:
46  *
47  * - It supports partitioning, which is useful for shared memory access using
48  * locks.
49  * - Shared memory hashes are allocated in a fixed size area at startup and
50  * are discoverable by name from other processes.
51  * - Because entries don't need to be moved in the case of hash conflicts,
52  * dynahash has better performance for large entries.
53  * - Guarantees stable pointers to entries.
54  *
55  * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
56  * Portions Copyright (c) 1994, Regents of the University of California
57  *
58  *
59  * IDENTIFICATION
60  * src/backend/utils/hash/dynahash.c
61  *
62  *-------------------------------------------------------------------------
63  */
64 
65 /*
66  * Original comments:
67  *
68  * Dynamic hashing, after CACM April 1988 pp 446-457, by Per-Ake Larson.
69  * Coded into C, with minor code improvements, and with hsearch(3) interface,
70  * by ejp@ausmelb.oz, Jul 26, 1988: 13:16;
71  * also, hcreate/hdestroy routines added to simulate hsearch(3).
72  *
73  * These routines simulate hsearch(3) and family, with the important
74  * difference that the hash table is dynamic - can grow indefinitely
75  * beyond its original size (as supplied to hcreate()).
76  *
77  * Performance appears to be comparable to that of hsearch(3).
78  * The 'source-code' options referred to in hsearch(3)'s 'man' page
79  * are not implemented; otherwise functionality is identical.
80  *
81  * Compilation controls:
82  * HASH_DEBUG controls some informative traces, mainly for debugging.
83  * HASH_STATISTICS causes HashAccesses and HashCollisions to be maintained;
84  * when combined with HASH_DEBUG, these are displayed by hdestroy().
85  *
86  * Problems & fixes to ejp@ausmelb.oz. WARNING: relies on pre-processor
87  * concatenation property, in probably unnecessary code 'optimization'.
88  *
89  * Modified margo@postgres.berkeley.edu February 1990
90  * added multiple table interface
91  * Modified by sullivan@postgres.berkeley.edu April 1990
92  * changed ctl structure for shared memory
93  */
94 
95 #include "postgres.h"
96 
97 #include <limits.h>
98 
99 #include "access/xact.h"
100 #include "common/hashfn.h"
101 #include "port/pg_bitutils.h"
102 #include "storage/shmem.h"
103 #include "storage/spin.h"
104 #include "utils/dynahash.h"
105 #include "utils/memutils.h"
106 
107 
108 /*
109  * Constants
110  *
111  * A hash table has a top-level "directory", each of whose entries points
112  * to a "segment" of ssize bucket headers. The maximum number of hash
113  * buckets is thus dsize * ssize (but dsize may be expansible). Of course,
114  * the number of records in the table can be larger, but we don't want a
115  * whole lot of records per bucket or performance goes down.
116  *
117  * In a hash table allocated in shared memory, the directory cannot be
118  * expanded because it must stay at a fixed address. The directory size
119  * should be selected using hash_select_dirsize (and you'd better have
120  * a good idea of the maximum number of entries!). For non-shared hash
121  * tables, the initial directory size can be left at the default.
122  */
123 #define DEF_SEGSIZE 256
124 #define DEF_SEGSIZE_SHIFT 8 /* must be log2(DEF_SEGSIZE) */
125 #define DEF_DIRSIZE 256
126 
127 /* Number of freelists to be used for a partitioned hash table. */
128 #define NUM_FREELISTS 32
129 
130 /* A hash bucket is a linked list of HASHELEMENTs */
132 
133 /* A hash segment is an array of bucket headers */
135 
136 /*
137  * Per-freelist data.
138  *
139  * In a partitioned hash table, each freelist is associated with a specific
140  * set of hashcodes, as determined by the FREELIST_IDX() macro below.
141  * nentries tracks the number of live hashtable entries having those hashcodes
142  * (NOT the number of entries in the freelist, as you might expect).
143  *
144  * The coverage of a freelist might be more or less than one partition, so it
145  * needs its own lock rather than relying on caller locking. Relying on that
146  * wouldn't work even if the coverage was the same, because of the occasional
147  * need to "borrow" entries from another freelist; see get_hash_entry().
148  *
149  * Using an array of FreeListData instead of separate arrays of mutexes,
150  * nentries and freeLists helps to reduce sharing of cache lines between
151  * different mutexes.
152  */
153 typedef struct
154 {
155  slock_t mutex; /* spinlock for this freelist */
156  long nentries; /* number of entries in associated buckets */
157  HASHELEMENT *freeList; /* chain of free elements */
158 } FreeListData;
159 
160 /*
161  * Header structure for a hash table --- contains all changeable info
162  *
163  * In a shared-memory hash table, the HASHHDR is in shared memory, while
164  * each backend has a local HTAB struct. For a non-shared table, there isn't
165  * any functional difference between HASHHDR and HTAB, but we separate them
166  * anyway to share code between shared and non-shared tables.
167  */
168 struct HASHHDR
169 {
170  /*
171  * The freelist can become a point of contention in high-concurrency hash
172  * tables, so we use an array of freelists, each with its own mutex and
173  * nentries count, instead of just a single one. Although the freelists
174  * normally operate independently, we will scavenge entries from freelists
175  * other than a hashcode's default freelist when necessary.
176  *
177  * If the hash table is not partitioned, only freeList[0] is used and its
178  * spinlock is not used at all; callers' locking is assumed sufficient.
179  */
181 
182  /* These fields can change, but not in a partitioned table */
183  /* Also, dsize can't change in a shared table, even if unpartitioned */
184  long dsize; /* directory size */
185  long nsegs; /* number of allocated segments (<= dsize) */
186  uint32 max_bucket; /* ID of maximum bucket in use */
187  uint32 high_mask; /* mask to modulo into entire table */
188  uint32 low_mask; /* mask to modulo into lower half of table */
189 
190  /* These fields are fixed at hashtable creation */
191  Size keysize; /* hash key length in bytes */
192  Size entrysize; /* total user element size in bytes */
193  long num_partitions; /* # partitions (must be power of 2), or 0 */
194  long max_dsize; /* 'dsize' limit if directory is fixed size */
195  long ssize; /* segment size --- must be power of 2 */
196  int sshift; /* segment shift = log2(ssize) */
197  int nelem_alloc; /* number of entries to allocate at once */
198 
199 #ifdef HASH_STATISTICS
200 
201  /*
202  * Count statistics here. NB: stats code doesn't bother with mutex, so
203  * counts could be corrupted a bit in a partitioned table.
204  */
205  long accesses;
206  long collisions;
207 #endif
208 };
209 
210 #define IS_PARTITIONED(hctl) ((hctl)->num_partitions != 0)
211 
212 #define FREELIST_IDX(hctl, hashcode) \
213  (IS_PARTITIONED(hctl) ? (hashcode) % NUM_FREELISTS : 0)
214 
215 /*
216  * Top control structure for a hashtable --- in a shared table, each backend
217  * has its own copy (OK since no fields change at runtime)
218  */
219 struct HTAB
220 {
221  HASHHDR *hctl; /* => shared control information */
222  HASHSEGMENT *dir; /* directory of segment starts */
223  HashValueFunc hash; /* hash function */
224  HashCompareFunc match; /* key comparison function */
225  HashCopyFunc keycopy; /* key copying function */
226  HashAllocFunc alloc; /* memory allocator */
227  MemoryContext hcxt; /* memory context if default allocator used */
228  char *tabname; /* table name (for error messages) */
229  bool isshared; /* true if table is in shared memory */
230  bool isfixed; /* if true, don't enlarge */
231 
232  /* freezing a shared table isn't allowed, so we can keep state here */
233  bool frozen; /* true = no more inserts allowed */
234 
235  /* We keep local copies of these fixed values to reduce contention */
236  Size keysize; /* hash key length in bytes */
237  long ssize; /* segment size --- must be power of 2 */
238  int sshift; /* segment shift = log2(ssize) */
239 };
240 
241 /*
242  * Key (also entry) part of a HASHELEMENT
243  */
244 #define ELEMENTKEY(helem) (((char *)(helem)) + MAXALIGN(sizeof(HASHELEMENT)))
245 
246 /*
247  * Obtain element pointer given pointer to key
248  */
249 #define ELEMENT_FROM_KEY(key) \
250  ((HASHELEMENT *) (((char *) (key)) - MAXALIGN(sizeof(HASHELEMENT))))
251 
252 /*
253  * Fast MOD arithmetic, assuming that y is a power of 2 !
254  */
255 #define MOD(x,y) ((x) & ((y)-1))
256 
257 #ifdef HASH_STATISTICS
258 static long hash_accesses,
259  hash_collisions,
260  hash_expansions;
261 #endif
262 
263 /*
264  * Private function prototypes
265  */
266 static void *DynaHashAlloc(Size size);
267 static HASHSEGMENT seg_alloc(HTAB *hashp);
268 static bool element_alloc(HTAB *hashp, int nelem, int freelist_idx);
269 static bool dir_realloc(HTAB *hashp);
270 static bool expand_table(HTAB *hashp);
271 static HASHBUCKET get_hash_entry(HTAB *hashp, int freelist_idx);
272 static void hdefault(HTAB *hashp);
273 static int choose_nelem_alloc(Size entrysize);
274 static bool init_htab(HTAB *hashp, long nelem);
275 static void hash_corrupted(HTAB *hashp);
276 static long next_pow2_long(long num);
277 static int next_pow2_int(long num);
278 static void register_seq_scan(HTAB *hashp);
279 static void deregister_seq_scan(HTAB *hashp);
280 static bool has_seq_scans(HTAB *hashp);
281 
282 
283 /*
284  * memory allocation support
285  */
287 
288 static void *
290 {
294 }
295 
296 
297 /*
298  * HashCompareFunc for string keys
299  *
300  * Because we copy keys with strlcpy(), they will be truncated at keysize-1
301  * bytes, so we can only compare that many ... hence strncmp is almost but
302  * not quite the right thing.
303  */
304 static int
305 string_compare(const char *key1, const char *key2, Size keysize)
306 {
307  return strncmp(key1, key2, keysize - 1);
308 }
309 
310 
311 /************************** CREATE ROUTINES **********************/
312 
313 /*
314  * hash_create -- create a new dynamic hash table
315  *
316  * tabname: a name for the table (for debugging purposes)
317  * nelem: maximum number of elements expected
318  * *info: additional table parameters, as indicated by flags
319  * flags: bitmask indicating which parameters to take from *info
320  *
321  * The flags value *must* include HASH_ELEM. (Formerly, this was nominally
322  * optional, but the default keysize and entrysize values were useless.)
323  * The flags value must also include exactly one of HASH_STRINGS, HASH_BLOBS,
324  * or HASH_FUNCTION, to define the key hashing semantics (C strings,
325  * binary blobs, or custom, respectively). Callers specifying a custom
326  * hash function will likely also want to use HASH_COMPARE, and perhaps
327  * also HASH_KEYCOPY, to control key comparison and copying.
328  * Another often-used flag is HASH_CONTEXT, to allocate the hash table
329  * under info->hcxt rather than under TopMemoryContext; the default
330  * behavior is only suitable for session-lifespan hash tables.
331  * Other flags bits are special-purpose and seldom used, except for those
332  * associated with shared-memory hash tables, for which see ShmemInitHash().
333  *
334  * Fields in *info are read only when the associated flags bit is set.
335  * It is not necessary to initialize other fields of *info.
336  * Neither tabname nor *info need persist after the hash_create() call.
337  *
338  * Note: It is deprecated for callers of hash_create() to explicitly specify
339  * string_hash, tag_hash, uint32_hash, or oid_hash. Just set HASH_STRINGS or
340  * HASH_BLOBS. Use HASH_FUNCTION only when you want something other than
341  * one of these.
342  *
343  * Note: for a shared-memory hashtable, nelem needs to be a pretty good
344  * estimate, since we can't expand the table on the fly. But an unshared
345  * hashtable can be expanded on-the-fly, so it's better for nelem to be
346  * on the small side and let the table grow if it's exceeded. An overly
347  * large nelem will penalize hash_seq_search speed without buying much.
348  */
349 HTAB *
350 hash_create(const char *tabname, long nelem, const HASHCTL *info, int flags)
351 {
352  HTAB *hashp;
353  HASHHDR *hctl;
354 
355  /*
356  * Hash tables now allocate space for key and data, but you have to say
357  * how much space to allocate.
358  */
359  Assert(flags & HASH_ELEM);
360  Assert(info->keysize > 0);
361  Assert(info->entrysize >= info->keysize);
362 
363  /*
364  * For shared hash tables, we have a local hash header (HTAB struct) that
365  * we allocate in TopMemoryContext; all else is in shared memory.
366  *
367  * For non-shared hash tables, everything including the hash header is in
368  * a memory context created specially for the hash table --- this makes
369  * hash_destroy very simple. The memory context is made a child of either
370  * a context specified by the caller, or TopMemoryContext if nothing is
371  * specified.
372  */
373  if (flags & HASH_SHARED_MEM)
374  {
375  /* Set up to allocate the hash header */
377  }
378  else
379  {
380  /* Create the hash table's private memory context */
381  if (flags & HASH_CONTEXT)
382  CurrentDynaHashCxt = info->hcxt;
383  else
386  "dynahash",
388  }
389 
390  /* Initialize the hash header, plus a copy of the table name */
391  hashp = (HTAB *) DynaHashAlloc(sizeof(HTAB) + strlen(tabname) + 1);
392  MemSet(hashp, 0, sizeof(HTAB));
393 
394  hashp->tabname = (char *) (hashp + 1);
395  strcpy(hashp->tabname, tabname);
396 
397  /* If we have a private context, label it with hashtable's name */
398  if (!(flags & HASH_SHARED_MEM))
400 
401  /*
402  * Select the appropriate hash function (see comments at head of file).
403  */
404  if (flags & HASH_FUNCTION)
405  {
406  Assert(!(flags & (HASH_BLOBS | HASH_STRINGS)));
407  hashp->hash = info->hash;
408  }
409  else if (flags & HASH_BLOBS)
410  {
411  Assert(!(flags & HASH_STRINGS));
412  /* We can optimize hashing for common key sizes */
413  if (info->keysize == sizeof(uint32))
414  hashp->hash = uint32_hash;
415  else
416  hashp->hash = tag_hash;
417  }
418  else
419  {
420  /*
421  * string_hash used to be considered the default hash method, and in a
422  * non-assert build it effectively still is. But we now consider it
423  * an assertion error to not say HASH_STRINGS explicitly. To help
424  * catch mistaken usage of HASH_STRINGS, we also insist on a
425  * reasonably long string length: if the keysize is only 4 or 8 bytes,
426  * it's almost certainly an integer or pointer not a string.
427  */
428  Assert(flags & HASH_STRINGS);
429  Assert(info->keysize > 8);
430 
431  hashp->hash = string_hash;
432  }
433 
434  /*
435  * If you don't specify a match function, it defaults to string_compare if
436  * you used string_hash, and to memcmp otherwise.
437  *
438  * Note: explicitly specifying string_hash is deprecated, because this
439  * might not work for callers in loadable modules on some platforms due to
440  * referencing a trampoline instead of the string_hash function proper.
441  * Specify HASH_STRINGS instead.
442  */
443  if (flags & HASH_COMPARE)
444  hashp->match = info->match;
445  else if (hashp->hash == string_hash)
447  else
448  hashp->match = memcmp;
449 
450  /*
451  * Similarly, the key-copying function defaults to strlcpy or memcpy.
452  */
453  if (flags & HASH_KEYCOPY)
454  hashp->keycopy = info->keycopy;
455  else if (hashp->hash == string_hash)
456  {
457  /*
458  * The signature of keycopy is meant for memcpy(), which returns
459  * void*, but strlcpy() returns size_t. Since we never use the return
460  * value of keycopy, and size_t is pretty much always the same size as
461  * void *, this should be safe. The extra cast in the middle is to
462  * avoid warnings from -Wcast-function-type.
463  */
465  }
466  else
467  hashp->keycopy = memcpy;
468 
469  /* And select the entry allocation function, too. */
470  if (flags & HASH_ALLOC)
471  hashp->alloc = info->alloc;
472  else
473  hashp->alloc = DynaHashAlloc;
474 
475  if (flags & HASH_SHARED_MEM)
476  {
477  /*
478  * ctl structure and directory are preallocated for shared memory
479  * tables. Note that HASH_DIRSIZE and HASH_ALLOC had better be set as
480  * well.
481  */
482  hashp->hctl = info->hctl;
483  hashp->dir = (HASHSEGMENT *) (((char *) info->hctl) + sizeof(HASHHDR));
484  hashp->hcxt = NULL;
485  hashp->isshared = true;
486 
487  /* hash table already exists, we're just attaching to it */
488  if (flags & HASH_ATTACH)
489  {
490  /* make local copies of some heavily-used values */
491  hctl = hashp->hctl;
492  hashp->keysize = hctl->keysize;
493  hashp->ssize = hctl->ssize;
494  hashp->sshift = hctl->sshift;
495 
496  return hashp;
497  }
498  }
499  else
500  {
501  /* setup hash table defaults */
502  hashp->hctl = NULL;
503  hashp->dir = NULL;
504  hashp->hcxt = CurrentDynaHashCxt;
505  hashp->isshared = false;
506  }
507 
508  if (!hashp->hctl)
509  {
510  hashp->hctl = (HASHHDR *) hashp->alloc(sizeof(HASHHDR));
511  if (!hashp->hctl)
512  ereport(ERROR,
513  (errcode(ERRCODE_OUT_OF_MEMORY),
514  errmsg("out of memory")));
515  }
516 
517  hashp->frozen = false;
518 
519  hdefault(hashp);
520 
521  hctl = hashp->hctl;
522 
523  if (flags & HASH_PARTITION)
524  {
525  /* Doesn't make sense to partition a local hash table */
526  Assert(flags & HASH_SHARED_MEM);
527 
528  /*
529  * The number of partitions had better be a power of 2. Also, it must
530  * be less than INT_MAX (see init_htab()), so call the int version of
531  * next_pow2.
532  */
534 
535  hctl->num_partitions = info->num_partitions;
536  }
537 
538  if (flags & HASH_SEGMENT)
539  {
540  hctl->ssize = info->ssize;
541  hctl->sshift = my_log2(info->ssize);
542  /* ssize had better be a power of 2 */
543  Assert(hctl->ssize == (1L << hctl->sshift));
544  }
545 
546  /*
547  * SHM hash tables have fixed directory size passed by the caller.
548  */
549  if (flags & HASH_DIRSIZE)
550  {
551  hctl->max_dsize = info->max_dsize;
552  hctl->dsize = info->dsize;
553  }
554 
555  /* remember the entry sizes, too */
556  hctl->keysize = info->keysize;
557  hctl->entrysize = info->entrysize;
558 
559  /* make local copies of heavily-used constant fields */
560  hashp->keysize = hctl->keysize;
561  hashp->ssize = hctl->ssize;
562  hashp->sshift = hctl->sshift;
563 
564  /* Build the hash directory structure */
565  if (!init_htab(hashp, nelem))
566  elog(ERROR, "failed to initialize hash table \"%s\"", hashp->tabname);
567 
568  /*
569  * For a shared hash table, preallocate the requested number of elements.
570  * This reduces problems with run-time out-of-shared-memory conditions.
571  *
572  * For a non-shared hash table, preallocate the requested number of
573  * elements if it's less than our chosen nelem_alloc. This avoids wasting
574  * space if the caller correctly estimates a small table size.
575  */
576  if ((flags & HASH_SHARED_MEM) ||
577  nelem < hctl->nelem_alloc)
578  {
579  int i,
580  freelist_partitions,
581  nelem_alloc,
582  nelem_alloc_first;
583 
584  /*
585  * If hash table is partitioned, give each freelist an equal share of
586  * the initial allocation. Otherwise only freeList[0] is used.
587  */
588  if (IS_PARTITIONED(hashp->hctl))
589  freelist_partitions = NUM_FREELISTS;
590  else
591  freelist_partitions = 1;
592 
593  nelem_alloc = nelem / freelist_partitions;
594  if (nelem_alloc <= 0)
595  nelem_alloc = 1;
596 
597  /*
598  * Make sure we'll allocate all the requested elements; freeList[0]
599  * gets the excess if the request isn't divisible by NUM_FREELISTS.
600  */
601  if (nelem_alloc * freelist_partitions < nelem)
602  nelem_alloc_first =
603  nelem - nelem_alloc * (freelist_partitions - 1);
604  else
605  nelem_alloc_first = nelem_alloc;
606 
607  for (i = 0; i < freelist_partitions; i++)
608  {
609  int temp = (i == 0) ? nelem_alloc_first : nelem_alloc;
610 
611  if (!element_alloc(hashp, temp, i))
612  ereport(ERROR,
613  (errcode(ERRCODE_OUT_OF_MEMORY),
614  errmsg("out of memory")));
615  }
616  }
617 
618  if (flags & HASH_FIXED_SIZE)
619  hashp->isfixed = true;
620  return hashp;
621 }
622 
623 /*
624  * Set default HASHHDR parameters.
625  */
626 static void
627 hdefault(HTAB *hashp)
628 {
629  HASHHDR *hctl = hashp->hctl;
630 
631  MemSet(hctl, 0, sizeof(HASHHDR));
632 
633  hctl->dsize = DEF_DIRSIZE;
634  hctl->nsegs = 0;
635 
636  hctl->num_partitions = 0; /* not partitioned */
637 
638  /* table has no fixed maximum size */
639  hctl->max_dsize = NO_MAX_DSIZE;
640 
641  hctl->ssize = DEF_SEGSIZE;
642  hctl->sshift = DEF_SEGSIZE_SHIFT;
643 
644 #ifdef HASH_STATISTICS
645  hctl->accesses = hctl->collisions = 0;
646 #endif
647 }
648 
649 /*
650  * Given the user-specified entry size, choose nelem_alloc, ie, how many
651  * elements to add to the hash table when we need more.
652  */
653 static int
655 {
656  int nelem_alloc;
657  Size elementSize;
658  Size allocSize;
659 
660  /* Each element has a HASHELEMENT header plus user data. */
661  /* NB: this had better match element_alloc() */
662  elementSize = MAXALIGN(sizeof(HASHELEMENT)) + MAXALIGN(entrysize);
663 
664  /*
665  * The idea here is to choose nelem_alloc at least 32, but round up so
666  * that the allocation request will be a power of 2 or just less. This
667  * makes little difference for hash tables in shared memory, but for hash
668  * tables managed by palloc, the allocation request will be rounded up to
669  * a power of 2 anyway. If we fail to take this into account, we'll waste
670  * as much as half the allocated space.
671  */
672  allocSize = 32 * 4; /* assume elementSize at least 8 */
673  do
674  {
675  allocSize <<= 1;
676  nelem_alloc = allocSize / elementSize;
677  } while (nelem_alloc < 32);
678 
679  return nelem_alloc;
680 }
681 
682 /*
683  * Compute derived fields of hctl and build the initial directory/segment
684  * arrays
685  */
686 static bool
687 init_htab(HTAB *hashp, long nelem)
688 {
689  HASHHDR *hctl = hashp->hctl;
690  HASHSEGMENT *segp;
691  int nbuckets;
692  int nsegs;
693  int i;
694 
695  /*
696  * initialize mutexes if it's a partitioned table
697  */
698  if (IS_PARTITIONED(hctl))
699  for (i = 0; i < NUM_FREELISTS; i++)
700  SpinLockInit(&(hctl->freeList[i].mutex));
701 
702  /*
703  * Allocate space for the next greater power of two number of buckets,
704  * assuming a desired maximum load factor of 1.
705  */
706  nbuckets = next_pow2_int(nelem);
707 
708  /*
709  * In a partitioned table, nbuckets must be at least equal to
710  * num_partitions; were it less, keys with apparently different partition
711  * numbers would map to the same bucket, breaking partition independence.
712  * (Normally nbuckets will be much bigger; this is just a safety check.)
713  */
714  while (nbuckets < hctl->num_partitions)
715  nbuckets <<= 1;
716 
717  hctl->max_bucket = hctl->low_mask = nbuckets - 1;
718  hctl->high_mask = (nbuckets << 1) - 1;
719 
720  /*
721  * Figure number of directory segments needed, round up to a power of 2
722  */
723  nsegs = (nbuckets - 1) / hctl->ssize + 1;
724  nsegs = next_pow2_int(nsegs);
725 
726  /*
727  * Make sure directory is big enough. If pre-allocated directory is too
728  * small, choke (caller screwed up).
729  */
730  if (nsegs > hctl->dsize)
731  {
732  if (!(hashp->dir))
733  hctl->dsize = nsegs;
734  else
735  return false;
736  }
737 
738  /* Allocate a directory */
739  if (!(hashp->dir))
740  {
741  CurrentDynaHashCxt = hashp->hcxt;
742  hashp->dir = (HASHSEGMENT *)
743  hashp->alloc(hctl->dsize * sizeof(HASHSEGMENT));
744  if (!hashp->dir)
745  return false;
746  }
747 
748  /* Allocate initial segments */
749  for (segp = hashp->dir; hctl->nsegs < nsegs; hctl->nsegs++, segp++)
750  {
751  *segp = seg_alloc(hashp);
752  if (*segp == NULL)
753  return false;
754  }
755 
756  /* Choose number of entries to allocate at a time */
758 
759 #ifdef HASH_DEBUG
760  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",
761  "TABLE POINTER ", hashp,
762  "DIRECTORY SIZE ", hctl->dsize,
763  "SEGMENT SIZE ", hctl->ssize,
764  "SEGMENT SHIFT ", hctl->sshift,
765  "MAX BUCKET ", hctl->max_bucket,
766  "HIGH MASK ", hctl->high_mask,
767  "LOW MASK ", hctl->low_mask,
768  "NSEGS ", hctl->nsegs);
769 #endif
770  return true;
771 }
772 
773 /*
774  * Estimate the space needed for a hashtable containing the given number
775  * of entries of given size.
776  * NOTE: this is used to estimate the footprint of hashtables in shared
777  * memory; therefore it does not count HTAB which is in local memory.
778  * NB: assumes that all hash structure parameters have default values!
779  */
780 Size
781 hash_estimate_size(long num_entries, Size entrysize)
782 {
783  Size size;
784  long nBuckets,
785  nSegments,
786  nDirEntries,
787  nElementAllocs,
788  elementSize,
789  elementAllocCnt;
790 
791  /* estimate number of buckets wanted */
792  nBuckets = next_pow2_long(num_entries);
793  /* # of segments needed for nBuckets */
794  nSegments = next_pow2_long((nBuckets - 1) / DEF_SEGSIZE + 1);
795  /* directory entries */
796  nDirEntries = DEF_DIRSIZE;
797  while (nDirEntries < nSegments)
798  nDirEntries <<= 1; /* dir_alloc doubles dsize at each call */
799 
800  /* fixed control info */
801  size = MAXALIGN(sizeof(HASHHDR)); /* but not HTAB, per above */
802  /* directory */
803  size = add_size(size, mul_size(nDirEntries, sizeof(HASHSEGMENT)));
804  /* segments */
805  size = add_size(size, mul_size(nSegments,
806  MAXALIGN(DEF_SEGSIZE * sizeof(HASHBUCKET))));
807  /* elements --- allocated in groups of choose_nelem_alloc() entries */
808  elementAllocCnt = choose_nelem_alloc(entrysize);
809  nElementAllocs = (num_entries - 1) / elementAllocCnt + 1;
810  elementSize = MAXALIGN(sizeof(HASHELEMENT)) + MAXALIGN(entrysize);
811  size = add_size(size,
812  mul_size(nElementAllocs,
813  mul_size(elementAllocCnt, elementSize)));
814 
815  return size;
816 }
817 
818 /*
819  * Select an appropriate directory size for a hashtable with the given
820  * maximum number of entries.
821  * This is only needed for hashtables in shared memory, whose directories
822  * cannot be expanded dynamically.
823  * NB: assumes that all hash structure parameters have default values!
824  *
825  * XXX this had better agree with the behavior of init_htab()...
826  */
827 long
828 hash_select_dirsize(long num_entries)
829 {
830  long nBuckets,
831  nSegments,
832  nDirEntries;
833 
834  /* estimate number of buckets wanted */
835  nBuckets = next_pow2_long(num_entries);
836  /* # of segments needed for nBuckets */
837  nSegments = next_pow2_long((nBuckets - 1) / DEF_SEGSIZE + 1);
838  /* directory entries */
839  nDirEntries = DEF_DIRSIZE;
840  while (nDirEntries < nSegments)
841  nDirEntries <<= 1; /* dir_alloc doubles dsize at each call */
842 
843  return nDirEntries;
844 }
845 
846 /*
847  * Compute the required initial memory allocation for a shared-memory
848  * hashtable with the given parameters. We need space for the HASHHDR
849  * and for the (non expansible) directory.
850  */
851 Size
852 hash_get_shared_size(HASHCTL *info, int flags)
853 {
854  Assert(flags & HASH_DIRSIZE);
855  Assert(info->dsize == info->max_dsize);
856  return sizeof(HASHHDR) + info->dsize * sizeof(HASHSEGMENT);
857 }
858 
859 
860 /********************** DESTROY ROUTINES ************************/
861 
862 void
864 {
865  if (hashp != NULL)
866  {
867  /* allocation method must be one we know how to free, too */
868  Assert(hashp->alloc == DynaHashAlloc);
869  /* so this hashtable must have its own context */
870  Assert(hashp->hcxt != NULL);
871 
872  hash_stats("destroy", hashp);
873 
874  /*
875  * Free everything by destroying the hash table's memory context.
876  */
877  MemoryContextDelete(hashp->hcxt);
878  }
879 }
880 
881 void
882 hash_stats(const char *where, HTAB *hashp)
883 {
884 #ifdef HASH_STATISTICS
885  fprintf(stderr, "%s: this HTAB -- accesses %ld collisions %ld\n",
886  where, hashp->hctl->accesses, hashp->hctl->collisions);
887 
888  fprintf(stderr, "hash_stats: entries %ld keysize %ld maxp %u segmentcount %ld\n",
889  hash_get_num_entries(hashp), (long) hashp->hctl->keysize,
890  hashp->hctl->max_bucket, hashp->hctl->nsegs);
891  fprintf(stderr, "%s: total accesses %ld total collisions %ld\n",
892  where, hash_accesses, hash_collisions);
893  fprintf(stderr, "hash_stats: total expansions %ld\n",
894  hash_expansions);
895 #endif
896 }
897 
898 /*******************************SEARCH ROUTINES *****************************/
899 
900 
901 /*
902  * get_hash_value -- exported routine to calculate a key's hash value
903  *
904  * We export this because for partitioned tables, callers need to compute
905  * the partition number (from the low-order bits of the hash value) before
906  * searching.
907  */
908 uint32
909 get_hash_value(HTAB *hashp, const void *keyPtr)
910 {
911  return hashp->hash(keyPtr, hashp->keysize);
912 }
913 
914 /* Convert a hash value to a bucket number */
915 static inline uint32
916 calc_bucket(HASHHDR *hctl, uint32 hash_val)
917 {
918  uint32 bucket;
919 
920  bucket = hash_val & hctl->high_mask;
921  if (bucket > hctl->max_bucket)
922  bucket = bucket & hctl->low_mask;
923 
924  return bucket;
925 }
926 
927 /*
928  * hash_search -- look up key in table and perform action
929  * hash_search_with_hash_value -- same, with key's hash value already computed
930  *
931  * action is one of:
932  * HASH_FIND: look up key in table
933  * HASH_ENTER: look up key in table, creating entry if not present
934  * HASH_ENTER_NULL: same, but return NULL if out of memory
935  * HASH_REMOVE: look up key in table, remove entry if present
936  *
937  * Return value is a pointer to the element found/entered/removed if any,
938  * or NULL if no match was found. (NB: in the case of the REMOVE action,
939  * the result is a dangling pointer that shouldn't be dereferenced!)
940  *
941  * HASH_ENTER will normally ereport a generic "out of memory" error if
942  * it is unable to create a new entry. The HASH_ENTER_NULL operation is
943  * the same except it will return NULL if out of memory.
944  *
945  * If foundPtr isn't NULL, then *foundPtr is set true if we found an
946  * existing entry in the table, false otherwise. This is needed in the
947  * HASH_ENTER case, but is redundant with the return value otherwise.
948  *
949  * For hash_search_with_hash_value, the hashvalue parameter must have been
950  * calculated with get_hash_value().
951  */
952 void *
954  const void *keyPtr,
956  bool *foundPtr)
957 {
958  return hash_search_with_hash_value(hashp,
959  keyPtr,
960  hashp->hash(keyPtr, hashp->keysize),
961  action,
962  foundPtr);
963 }
964 
965 void *
967  const void *keyPtr,
968  uint32 hashvalue,
970  bool *foundPtr)
971 {
972  HASHHDR *hctl = hashp->hctl;
973  int freelist_idx = FREELIST_IDX(hctl, hashvalue);
974  Size keysize;
975  uint32 bucket;
976  long segment_num;
977  long segment_ndx;
978  HASHSEGMENT segp;
979  HASHBUCKET currBucket;
980  HASHBUCKET *prevBucketPtr;
981  HashCompareFunc match;
982 
983 #ifdef HASH_STATISTICS
984  hash_accesses++;
985  hctl->accesses++;
986 #endif
987 
988  /*
989  * If inserting, check if it is time to split a bucket.
990  *
991  * NOTE: failure to expand table is not a fatal error, it just means we
992  * have to run at higher fill factor than we wanted. However, if we're
993  * using the palloc allocator then it will throw error anyway on
994  * out-of-memory, so we must do this before modifying the table.
995  */
997  {
998  /*
999  * Can't split if running in partitioned mode, nor if frozen, nor if
1000  * table is the subject of any active hash_seq_search scans.
1001  */
1002  if (hctl->freeList[0].nentries > (long) hctl->max_bucket &&
1003  !IS_PARTITIONED(hctl) && !hashp->frozen &&
1004  !has_seq_scans(hashp))
1005  (void) expand_table(hashp);
1006  }
1007 
1008  /*
1009  * Do the initial lookup
1010  */
1011  bucket = calc_bucket(hctl, hashvalue);
1012 
1013  segment_num = bucket >> hashp->sshift;
1014  segment_ndx = MOD(bucket, hashp->ssize);
1015 
1016  segp = hashp->dir[segment_num];
1017 
1018  if (segp == NULL)
1019  hash_corrupted(hashp);
1020 
1021  prevBucketPtr = &segp[segment_ndx];
1022  currBucket = *prevBucketPtr;
1023 
1024  /*
1025  * Follow collision chain looking for matching key
1026  */
1027  match = hashp->match; /* save one fetch in inner loop */
1028  keysize = hashp->keysize; /* ditto */
1029 
1030  while (currBucket != NULL)
1031  {
1032  if (currBucket->hashvalue == hashvalue &&
1033  match(ELEMENTKEY(currBucket), keyPtr, keysize) == 0)
1034  break;
1035  prevBucketPtr = &(currBucket->link);
1036  currBucket = *prevBucketPtr;
1037 #ifdef HASH_STATISTICS
1038  hash_collisions++;
1039  hctl->collisions++;
1040 #endif
1041  }
1042 
1043  if (foundPtr)
1044  *foundPtr = (bool) (currBucket != NULL);
1045 
1046  /*
1047  * OK, now what?
1048  */
1049  switch (action)
1050  {
1051  case HASH_FIND:
1052  if (currBucket != NULL)
1053  return (void *) ELEMENTKEY(currBucket);
1054  return NULL;
1055 
1056  case HASH_REMOVE:
1057  if (currBucket != NULL)
1058  {
1059  /* if partitioned, must lock to touch nentries and freeList */
1060  if (IS_PARTITIONED(hctl))
1061  SpinLockAcquire(&(hctl->freeList[freelist_idx].mutex));
1062 
1063  /* delete the record from the appropriate nentries counter. */
1064  Assert(hctl->freeList[freelist_idx].nentries > 0);
1065  hctl->freeList[freelist_idx].nentries--;
1066 
1067  /* remove record from hash bucket's chain. */
1068  *prevBucketPtr = currBucket->link;
1069 
1070  /* add the record to the appropriate freelist. */
1071  currBucket->link = hctl->freeList[freelist_idx].freeList;
1072  hctl->freeList[freelist_idx].freeList = currBucket;
1073 
1074  if (IS_PARTITIONED(hctl))
1075  SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1076 
1077  /*
1078  * better hope the caller is synchronizing access to this
1079  * element, because someone else is going to reuse it the next
1080  * time something is added to the table
1081  */
1082  return (void *) ELEMENTKEY(currBucket);
1083  }
1084  return NULL;
1085 
1086  case HASH_ENTER:
1087  case HASH_ENTER_NULL:
1088  /* Return existing element if found, else create one */
1089  if (currBucket != NULL)
1090  return (void *) ELEMENTKEY(currBucket);
1091 
1092  /* disallow inserts if frozen */
1093  if (hashp->frozen)
1094  elog(ERROR, "cannot insert into frozen hashtable \"%s\"",
1095  hashp->tabname);
1096 
1097  currBucket = get_hash_entry(hashp, freelist_idx);
1098  if (currBucket == NULL)
1099  {
1100  /* out of memory */
1101  if (action == HASH_ENTER_NULL)
1102  return NULL;
1103  /* report a generic message */
1104  if (hashp->isshared)
1105  ereport(ERROR,
1106  (errcode(ERRCODE_OUT_OF_MEMORY),
1107  errmsg("out of shared memory")));
1108  else
1109  ereport(ERROR,
1110  (errcode(ERRCODE_OUT_OF_MEMORY),
1111  errmsg("out of memory")));
1112  }
1113 
1114  /* link into hashbucket chain */
1115  *prevBucketPtr = currBucket;
1116  currBucket->link = NULL;
1117 
1118  /* copy key into record */
1119  currBucket->hashvalue = hashvalue;
1120  hashp->keycopy(ELEMENTKEY(currBucket), keyPtr, keysize);
1121 
1122  /*
1123  * Caller is expected to fill the data field on return. DO NOT
1124  * insert any code that could possibly throw error here, as doing
1125  * so would leave the table entry incomplete and hence corrupt the
1126  * caller's data structure.
1127  */
1128 
1129  return (void *) ELEMENTKEY(currBucket);
1130  }
1131 
1132  elog(ERROR, "unrecognized hash action code: %d", (int) action);
1133 
1134  return NULL; /* keep compiler quiet */
1135 }
1136 
1137 /*
1138  * hash_update_hash_key -- change the hash key of an existing table entry
1139  *
1140  * This is equivalent to removing the entry, making a new entry, and copying
1141  * over its data, except that the entry never goes to the table's freelist.
1142  * Therefore this cannot suffer an out-of-memory failure, even if there are
1143  * other processes operating in other partitions of the hashtable.
1144  *
1145  * Returns true if successful, false if the requested new hash key is already
1146  * present. Throws error if the specified entry pointer isn't actually a
1147  * table member.
1148  *
1149  * NB: currently, there is no special case for old and new hash keys being
1150  * identical, which means we'll report false for that situation. This is
1151  * preferable for existing uses.
1152  *
1153  * NB: for a partitioned hashtable, caller must hold lock on both relevant
1154  * partitions, if the new hash key would belong to a different partition.
1155  */
1156 bool
1158  void *existingEntry,
1159  const void *newKeyPtr)
1160 {
1161  HASHELEMENT *existingElement = ELEMENT_FROM_KEY(existingEntry);
1162  HASHHDR *hctl = hashp->hctl;
1163  uint32 newhashvalue;
1164  Size keysize;
1165  uint32 bucket;
1166  uint32 newbucket;
1167  long segment_num;
1168  long segment_ndx;
1169  HASHSEGMENT segp;
1170  HASHBUCKET currBucket;
1171  HASHBUCKET *prevBucketPtr;
1172  HASHBUCKET *oldPrevPtr;
1173  HashCompareFunc match;
1174 
1175 #ifdef HASH_STATISTICS
1176  hash_accesses++;
1177  hctl->accesses++;
1178 #endif
1179 
1180  /* disallow updates if frozen */
1181  if (hashp->frozen)
1182  elog(ERROR, "cannot update in frozen hashtable \"%s\"",
1183  hashp->tabname);
1184 
1185  /*
1186  * Lookup the existing element using its saved hash value. We need to do
1187  * this to be able to unlink it from its hash chain, but as a side benefit
1188  * we can verify the validity of the passed existingEntry pointer.
1189  */
1190  bucket = calc_bucket(hctl, existingElement->hashvalue);
1191 
1192  segment_num = bucket >> hashp->sshift;
1193  segment_ndx = MOD(bucket, hashp->ssize);
1194 
1195  segp = hashp->dir[segment_num];
1196 
1197  if (segp == NULL)
1198  hash_corrupted(hashp);
1199 
1200  prevBucketPtr = &segp[segment_ndx];
1201  currBucket = *prevBucketPtr;
1202 
1203  while (currBucket != NULL)
1204  {
1205  if (currBucket == existingElement)
1206  break;
1207  prevBucketPtr = &(currBucket->link);
1208  currBucket = *prevBucketPtr;
1209  }
1210 
1211  if (currBucket == NULL)
1212  elog(ERROR, "hash_update_hash_key argument is not in hashtable \"%s\"",
1213  hashp->tabname);
1214 
1215  oldPrevPtr = prevBucketPtr;
1216 
1217  /*
1218  * Now perform the equivalent of a HASH_ENTER operation to locate the hash
1219  * chain we want to put the entry into.
1220  */
1221  newhashvalue = hashp->hash(newKeyPtr, hashp->keysize);
1222 
1223  newbucket = calc_bucket(hctl, newhashvalue);
1224 
1225  segment_num = newbucket >> hashp->sshift;
1226  segment_ndx = MOD(newbucket, hashp->ssize);
1227 
1228  segp = hashp->dir[segment_num];
1229 
1230  if (segp == NULL)
1231  hash_corrupted(hashp);
1232 
1233  prevBucketPtr = &segp[segment_ndx];
1234  currBucket = *prevBucketPtr;
1235 
1236  /*
1237  * Follow collision chain looking for matching key
1238  */
1239  match = hashp->match; /* save one fetch in inner loop */
1240  keysize = hashp->keysize; /* ditto */
1241 
1242  while (currBucket != NULL)
1243  {
1244  if (currBucket->hashvalue == newhashvalue &&
1245  match(ELEMENTKEY(currBucket), newKeyPtr, keysize) == 0)
1246  break;
1247  prevBucketPtr = &(currBucket->link);
1248  currBucket = *prevBucketPtr;
1249 #ifdef HASH_STATISTICS
1250  hash_collisions++;
1251  hctl->collisions++;
1252 #endif
1253  }
1254 
1255  if (currBucket != NULL)
1256  return false; /* collision with an existing entry */
1257 
1258  currBucket = existingElement;
1259 
1260  /*
1261  * If old and new hash values belong to the same bucket, we need not
1262  * change any chain links, and indeed should not since this simplistic
1263  * update will corrupt the list if currBucket is the last element. (We
1264  * cannot fall out earlier, however, since we need to scan the bucket to
1265  * check for duplicate keys.)
1266  */
1267  if (bucket != newbucket)
1268  {
1269  /* OK to remove record from old hash bucket's chain. */
1270  *oldPrevPtr = currBucket->link;
1271 
1272  /* link into new hashbucket chain */
1273  *prevBucketPtr = currBucket;
1274  currBucket->link = NULL;
1275  }
1276 
1277  /* copy new key into record */
1278  currBucket->hashvalue = newhashvalue;
1279  hashp->keycopy(ELEMENTKEY(currBucket), newKeyPtr, keysize);
1280 
1281  /* rest of record is untouched */
1282 
1283  return true;
1284 }
1285 
1286 /*
1287  * Allocate a new hashtable entry if possible; return NULL if out of memory.
1288  * (Or, if the underlying space allocator throws error for out-of-memory,
1289  * we won't return at all.)
1290  */
1291 static HASHBUCKET
1292 get_hash_entry(HTAB *hashp, int freelist_idx)
1293 {
1294  HASHHDR *hctl = hashp->hctl;
1295  HASHBUCKET newElement;
1296 
1297  for (;;)
1298  {
1299  /* if partitioned, must lock to touch nentries and freeList */
1300  if (IS_PARTITIONED(hctl))
1301  SpinLockAcquire(&hctl->freeList[freelist_idx].mutex);
1302 
1303  /* try to get an entry from the freelist */
1304  newElement = hctl->freeList[freelist_idx].freeList;
1305 
1306  if (newElement != NULL)
1307  break;
1308 
1309  if (IS_PARTITIONED(hctl))
1310  SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1311 
1312  /*
1313  * No free elements in this freelist. In a partitioned table, there
1314  * might be entries in other freelists, but to reduce contention we
1315  * prefer to first try to get another chunk of buckets from the main
1316  * shmem allocator. If that fails, though, we *MUST* root through all
1317  * the other freelists before giving up. There are multiple callers
1318  * that assume that they can allocate every element in the initially
1319  * requested table size, or that deleting an element guarantees they
1320  * can insert a new element, even if shared memory is entirely full.
1321  * Failing because the needed element is in a different freelist is
1322  * not acceptable.
1323  */
1324  if (!element_alloc(hashp, hctl->nelem_alloc, freelist_idx))
1325  {
1326  int borrow_from_idx;
1327 
1328  if (!IS_PARTITIONED(hctl))
1329  return NULL; /* out of memory */
1330 
1331  /* try to borrow element from another freelist */
1332  borrow_from_idx = freelist_idx;
1333  for (;;)
1334  {
1335  borrow_from_idx = (borrow_from_idx + 1) % NUM_FREELISTS;
1336  if (borrow_from_idx == freelist_idx)
1337  break; /* examined all freelists, fail */
1338 
1339  SpinLockAcquire(&(hctl->freeList[borrow_from_idx].mutex));
1340  newElement = hctl->freeList[borrow_from_idx].freeList;
1341 
1342  if (newElement != NULL)
1343  {
1344  hctl->freeList[borrow_from_idx].freeList = newElement->link;
1345  SpinLockRelease(&(hctl->freeList[borrow_from_idx].mutex));
1346 
1347  /* careful: count the new element in its proper freelist */
1348  SpinLockAcquire(&hctl->freeList[freelist_idx].mutex);
1349  hctl->freeList[freelist_idx].nentries++;
1350  SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1351 
1352  return newElement;
1353  }
1354 
1355  SpinLockRelease(&(hctl->freeList[borrow_from_idx].mutex));
1356  }
1357 
1358  /* no elements available to borrow either, so out of memory */
1359  return NULL;
1360  }
1361  }
1362 
1363  /* remove entry from freelist, bump nentries */
1364  hctl->freeList[freelist_idx].freeList = newElement->link;
1365  hctl->freeList[freelist_idx].nentries++;
1366 
1367  if (IS_PARTITIONED(hctl))
1368  SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1369 
1370  return newElement;
1371 }
1372 
1373 /*
1374  * hash_get_num_entries -- get the number of entries in a hashtable
1375  */
1376 long
1378 {
1379  int i;
1380  long sum = hashp->hctl->freeList[0].nentries;
1381 
1382  /*
1383  * We currently don't bother with acquiring the mutexes; it's only
1384  * sensible to call this function if you've got lock on all partitions of
1385  * the table.
1386  */
1387  if (IS_PARTITIONED(hashp->hctl))
1388  {
1389  for (i = 1; i < NUM_FREELISTS; i++)
1390  sum += hashp->hctl->freeList[i].nentries;
1391  }
1392 
1393  return sum;
1394 }
1395 
1396 /*
1397  * hash_seq_init/_search/_term
1398  * Sequentially search through hash table and return
1399  * all the elements one by one, return NULL when no more.
1400  *
1401  * hash_seq_term should be called if and only if the scan is abandoned before
1402  * completion; if hash_seq_search returns NULL then it has already done the
1403  * end-of-scan cleanup.
1404  *
1405  * NOTE: caller may delete the returned element before continuing the scan.
1406  * However, deleting any other element while the scan is in progress is
1407  * UNDEFINED (it might be the one that curIndex is pointing at!). Also,
1408  * if elements are added to the table while the scan is in progress, it is
1409  * unspecified whether they will be visited by the scan or not.
1410  *
1411  * NOTE: it is possible to use hash_seq_init/hash_seq_search without any
1412  * worry about hash_seq_term cleanup, if the hashtable is first locked against
1413  * further insertions by calling hash_freeze.
1414  *
1415  * NOTE: to use this with a partitioned hashtable, caller had better hold
1416  * at least shared lock on all partitions of the table throughout the scan!
1417  * We can cope with insertions or deletions by our own backend, but *not*
1418  * with concurrent insertions or deletions by another.
1419  */
1420 void
1422 {
1423  status->hashp = hashp;
1424  status->curBucket = 0;
1425  status->curEntry = NULL;
1426  if (!hashp->frozen)
1427  register_seq_scan(hashp);
1428 }
1429 
1430 void *
1432 {
1433  HTAB *hashp;
1434  HASHHDR *hctl;
1435  uint32 max_bucket;
1436  long ssize;
1437  long segment_num;
1438  long segment_ndx;
1439  HASHSEGMENT segp;
1440  uint32 curBucket;
1441  HASHELEMENT *curElem;
1442 
1443  if ((curElem = status->curEntry) != NULL)
1444  {
1445  /* Continuing scan of curBucket... */
1446  status->curEntry = curElem->link;
1447  if (status->curEntry == NULL) /* end of this bucket */
1448  ++status->curBucket;
1449  return (void *) ELEMENTKEY(curElem);
1450  }
1451 
1452  /*
1453  * Search for next nonempty bucket starting at curBucket.
1454  */
1455  curBucket = status->curBucket;
1456  hashp = status->hashp;
1457  hctl = hashp->hctl;
1458  ssize = hashp->ssize;
1459  max_bucket = hctl->max_bucket;
1460 
1461  if (curBucket > max_bucket)
1462  {
1464  return NULL; /* search is done */
1465  }
1466 
1467  /*
1468  * first find the right segment in the table directory.
1469  */
1470  segment_num = curBucket >> hashp->sshift;
1471  segment_ndx = MOD(curBucket, ssize);
1472 
1473  segp = hashp->dir[segment_num];
1474 
1475  /*
1476  * Pick up the first item in this bucket's chain. If chain is not empty
1477  * we can begin searching it. Otherwise we have to advance to find the
1478  * next nonempty bucket. We try to optimize that case since searching a
1479  * near-empty hashtable has to iterate this loop a lot.
1480  */
1481  while ((curElem = segp[segment_ndx]) == NULL)
1482  {
1483  /* empty bucket, advance to next */
1484  if (++curBucket > max_bucket)
1485  {
1486  status->curBucket = curBucket;
1488  return NULL; /* search is done */
1489  }
1490  if (++segment_ndx >= ssize)
1491  {
1492  segment_num++;
1493  segment_ndx = 0;
1494  segp = hashp->dir[segment_num];
1495  }
1496  }
1497 
1498  /* Begin scan of curBucket... */
1499  status->curEntry = curElem->link;
1500  if (status->curEntry == NULL) /* end of this bucket */
1501  ++curBucket;
1502  status->curBucket = curBucket;
1503  return (void *) ELEMENTKEY(curElem);
1504 }
1505 
1506 void
1508 {
1509  if (!status->hashp->frozen)
1510  deregister_seq_scan(status->hashp);
1511 }
1512 
1513 /*
1514  * hash_freeze
1515  * Freeze a hashtable against future insertions (deletions are
1516  * still allowed)
1517  *
1518  * The reason for doing this is that by preventing any more bucket splits,
1519  * we no longer need to worry about registering hash_seq_search scans,
1520  * and thus caller need not be careful about ensuring hash_seq_term gets
1521  * called at the right times.
1522  *
1523  * Multiple calls to hash_freeze() are allowed, but you can't freeze a table
1524  * with active scans (since hash_seq_term would then do the wrong thing).
1525  */
1526 void
1528 {
1529  if (hashp->isshared)
1530  elog(ERROR, "cannot freeze shared hashtable \"%s\"", hashp->tabname);
1531  if (!hashp->frozen && has_seq_scans(hashp))
1532  elog(ERROR, "cannot freeze hashtable \"%s\" because it has active scans",
1533  hashp->tabname);
1534  hashp->frozen = true;
1535 }
1536 
1537 
1538 /********************************* UTILITIES ************************/
1539 
1540 /*
1541  * Expand the table by adding one more hash bucket.
1542  */
1543 static bool
1545 {
1546  HASHHDR *hctl = hashp->hctl;
1547  HASHSEGMENT old_seg,
1548  new_seg;
1549  long old_bucket,
1550  new_bucket;
1551  long new_segnum,
1552  new_segndx;
1553  long old_segnum,
1554  old_segndx;
1555  HASHBUCKET *oldlink,
1556  *newlink;
1557  HASHBUCKET currElement,
1558  nextElement;
1559 
1560  Assert(!IS_PARTITIONED(hctl));
1561 
1562 #ifdef HASH_STATISTICS
1563  hash_expansions++;
1564 #endif
1565 
1566  new_bucket = hctl->max_bucket + 1;
1567  new_segnum = new_bucket >> hashp->sshift;
1568  new_segndx = MOD(new_bucket, hashp->ssize);
1569 
1570  if (new_segnum >= hctl->nsegs)
1571  {
1572  /* Allocate new segment if necessary -- could fail if dir full */
1573  if (new_segnum >= hctl->dsize)
1574  if (!dir_realloc(hashp))
1575  return false;
1576  if (!(hashp->dir[new_segnum] = seg_alloc(hashp)))
1577  return false;
1578  hctl->nsegs++;
1579  }
1580 
1581  /* OK, we created a new bucket */
1582  hctl->max_bucket++;
1583 
1584  /*
1585  * *Before* changing masks, find old bucket corresponding to same hash
1586  * values; values in that bucket may need to be relocated to new bucket.
1587  * Note that new_bucket is certainly larger than low_mask at this point,
1588  * so we can skip the first step of the regular hash mask calc.
1589  */
1590  old_bucket = (new_bucket & hctl->low_mask);
1591 
1592  /*
1593  * If we crossed a power of 2, readjust masks.
1594  */
1595  if ((uint32) new_bucket > hctl->high_mask)
1596  {
1597  hctl->low_mask = hctl->high_mask;
1598  hctl->high_mask = (uint32) new_bucket | hctl->low_mask;
1599  }
1600 
1601  /*
1602  * Relocate records to the new bucket. NOTE: because of the way the hash
1603  * masking is done in calc_bucket, only one old bucket can need to be
1604  * split at this point. With a different way of reducing the hash value,
1605  * that might not be true!
1606  */
1607  old_segnum = old_bucket >> hashp->sshift;
1608  old_segndx = MOD(old_bucket, hashp->ssize);
1609 
1610  old_seg = hashp->dir[old_segnum];
1611  new_seg = hashp->dir[new_segnum];
1612 
1613  oldlink = &old_seg[old_segndx];
1614  newlink = &new_seg[new_segndx];
1615 
1616  for (currElement = *oldlink;
1617  currElement != NULL;
1618  currElement = nextElement)
1619  {
1620  nextElement = currElement->link;
1621  if ((long) calc_bucket(hctl, currElement->hashvalue) == old_bucket)
1622  {
1623  *oldlink = currElement;
1624  oldlink = &currElement->link;
1625  }
1626  else
1627  {
1628  *newlink = currElement;
1629  newlink = &currElement->link;
1630  }
1631  }
1632  /* don't forget to terminate the rebuilt hash chains... */
1633  *oldlink = NULL;
1634  *newlink = NULL;
1635 
1636  return true;
1637 }
1638 
1639 
1640 static bool
1642 {
1643  HASHSEGMENT *p;
1644  HASHSEGMENT *old_p;
1645  long new_dsize;
1646  long old_dirsize;
1647  long new_dirsize;
1648 
1649  if (hashp->hctl->max_dsize != NO_MAX_DSIZE)
1650  return false;
1651 
1652  /* Reallocate directory */
1653  new_dsize = hashp->hctl->dsize << 1;
1654  old_dirsize = hashp->hctl->dsize * sizeof(HASHSEGMENT);
1655  new_dirsize = new_dsize * sizeof(HASHSEGMENT);
1656 
1657  old_p = hashp->dir;
1658  CurrentDynaHashCxt = hashp->hcxt;
1659  p = (HASHSEGMENT *) hashp->alloc((Size) new_dirsize);
1660 
1661  if (p != NULL)
1662  {
1663  memcpy(p, old_p, old_dirsize);
1664  MemSet(((char *) p) + old_dirsize, 0, new_dirsize - old_dirsize);
1665  hashp->dir = p;
1666  hashp->hctl->dsize = new_dsize;
1667 
1668  /* XXX assume the allocator is palloc, so we know how to free */
1669  Assert(hashp->alloc == DynaHashAlloc);
1670  pfree(old_p);
1671 
1672  return true;
1673  }
1674 
1675  return false;
1676 }
1677 
1678 
1679 static HASHSEGMENT
1681 {
1682  HASHSEGMENT segp;
1683 
1684  CurrentDynaHashCxt = hashp->hcxt;
1685  segp = (HASHSEGMENT) hashp->alloc(sizeof(HASHBUCKET) * hashp->ssize);
1686 
1687  if (!segp)
1688  return NULL;
1689 
1690  MemSet(segp, 0, sizeof(HASHBUCKET) * hashp->ssize);
1691 
1692  return segp;
1693 }
1694 
1695 /*
1696  * allocate some new elements and link them into the indicated free list
1697  */
1698 static bool
1699 element_alloc(HTAB *hashp, int nelem, int freelist_idx)
1700 {
1701  HASHHDR *hctl = hashp->hctl;
1702  Size elementSize;
1703  HASHELEMENT *firstElement;
1704  HASHELEMENT *tmpElement;
1705  HASHELEMENT *prevElement;
1706  int i;
1707 
1708  if (hashp->isfixed)
1709  return false;
1710 
1711  /* Each element has a HASHELEMENT header plus user data. */
1712  elementSize = MAXALIGN(sizeof(HASHELEMENT)) + MAXALIGN(hctl->entrysize);
1713 
1714  CurrentDynaHashCxt = hashp->hcxt;
1715  firstElement = (HASHELEMENT *) hashp->alloc(nelem * elementSize);
1716 
1717  if (!firstElement)
1718  return false;
1719 
1720  /* prepare to link all the new entries into the freelist */
1721  prevElement = NULL;
1722  tmpElement = firstElement;
1723  for (i = 0; i < nelem; i++)
1724  {
1725  tmpElement->link = prevElement;
1726  prevElement = tmpElement;
1727  tmpElement = (HASHELEMENT *) (((char *) tmpElement) + elementSize);
1728  }
1729 
1730  /* if partitioned, must lock to touch freeList */
1731  if (IS_PARTITIONED(hctl))
1732  SpinLockAcquire(&hctl->freeList[freelist_idx].mutex);
1733 
1734  /* freelist could be nonempty if two backends did this concurrently */
1735  firstElement->link = hctl->freeList[freelist_idx].freeList;
1736  hctl->freeList[freelist_idx].freeList = prevElement;
1737 
1738  if (IS_PARTITIONED(hctl))
1739  SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1740 
1741  return true;
1742 }
1743 
1744 /* complain when we have detected a corrupted hashtable */
1745 static void
1747 {
1748  /*
1749  * If the corruption is in a shared hashtable, we'd better force a
1750  * systemwide restart. Otherwise, just shut down this one backend.
1751  */
1752  if (hashp->isshared)
1753  elog(PANIC, "hash table \"%s\" corrupted", hashp->tabname);
1754  else
1755  elog(FATAL, "hash table \"%s\" corrupted", hashp->tabname);
1756 }
1757 
1758 /* calculate ceil(log base 2) of num */
1759 int
1760 my_log2(long num)
1761 {
1762  /*
1763  * guard against too-large input, which would be invalid for
1764  * pg_ceil_log2_*()
1765  */
1766  if (num > LONG_MAX / 2)
1767  num = LONG_MAX / 2;
1768 
1769 #if SIZEOF_LONG < 8
1770  return pg_ceil_log2_32(num);
1771 #else
1772  return pg_ceil_log2_64(num);
1773 #endif
1774 }
1775 
1776 /* calculate first power of 2 >= num, bounded to what will fit in a long */
1777 static long
1779 {
1780  /* my_log2's internal range check is sufficient */
1781  return 1L << my_log2(num);
1782 }
1783 
1784 /* calculate first power of 2 >= num, bounded to what will fit in an int */
1785 static int
1786 next_pow2_int(long num)
1787 {
1788  if (num > INT_MAX / 2)
1789  num = INT_MAX / 2;
1790  return 1 << my_log2(num);
1791 }
1792 
1793 
1794 /************************* SEQ SCAN TRACKING ************************/
1795 
1796 /*
1797  * We track active hash_seq_search scans here. The need for this mechanism
1798  * comes from the fact that a scan will get confused if a bucket split occurs
1799  * while it's in progress: it might visit entries twice, or even miss some
1800  * entirely (if it's partway through the same bucket that splits). Hence
1801  * we want to inhibit bucket splits if there are any active scans on the
1802  * table being inserted into. This is a fairly rare case in current usage,
1803  * so just postponing the split until the next insertion seems sufficient.
1804  *
1805  * Given present usages of the function, only a few scans are likely to be
1806  * open concurrently; so a finite-size stack of open scans seems sufficient,
1807  * and we don't worry that linear search is too slow. Note that we do
1808  * allow multiple scans of the same hashtable to be open concurrently.
1809  *
1810  * This mechanism can support concurrent scan and insertion in a shared
1811  * hashtable if it's the same backend doing both. It would fail otherwise,
1812  * but locking reasons seem to preclude any such scenario anyway, so we don't
1813  * worry.
1814  *
1815  * This arrangement is reasonably robust if a transient hashtable is deleted
1816  * without notifying us. The absolute worst case is we might inhibit splits
1817  * in another table created later at exactly the same address. We will give
1818  * a warning at transaction end for reference leaks, so any bugs leading to
1819  * lack of notification should be easy to catch.
1820  */
1821 
1822 #define MAX_SEQ_SCANS 100
1823 
1824 static HTAB *seq_scan_tables[MAX_SEQ_SCANS]; /* tables being scanned */
1825 static int seq_scan_level[MAX_SEQ_SCANS]; /* subtransaction nest level */
1826 static int num_seq_scans = 0;
1827 
1828 
1829 /* Register a table as having an active hash_seq_search scan */
1830 static void
1832 {
1834  elog(ERROR, "too many active hash_seq_search scans, cannot start one on \"%s\"",
1835  hashp->tabname);
1836  seq_scan_tables[num_seq_scans] = hashp;
1838  num_seq_scans++;
1839 }
1840 
1841 /* Deregister an active scan */
1842 static void
1844 {
1845  int i;
1846 
1847  /* Search backward since it's most likely at the stack top */
1848  for (i = num_seq_scans - 1; i >= 0; i--)
1849  {
1850  if (seq_scan_tables[i] == hashp)
1851  {
1854  num_seq_scans--;
1855  return;
1856  }
1857  }
1858  elog(ERROR, "no hash_seq_search scan for hash table \"%s\"",
1859  hashp->tabname);
1860 }
1861 
1862 /* Check if a table has any active scan */
1863 static bool
1865 {
1866  int i;
1867 
1868  for (i = 0; i < num_seq_scans; i++)
1869  {
1870  if (seq_scan_tables[i] == hashp)
1871  return true;
1872  }
1873  return false;
1874 }
1875 
1876 /* Clean up any open scans at end of transaction */
1877 void
1878 AtEOXact_HashTables(bool isCommit)
1879 {
1880  /*
1881  * During abort cleanup, open scans are expected; just silently clean 'em
1882  * out. An open scan at commit means someone forgot a hash_seq_term()
1883  * call, so complain.
1884  *
1885  * Note: it's tempting to try to print the tabname here, but refrain for
1886  * fear of touching deallocated memory. This isn't a user-facing message
1887  * anyway, so it needn't be pretty.
1888  */
1889  if (isCommit)
1890  {
1891  int i;
1892 
1893  for (i = 0; i < num_seq_scans; i++)
1894  {
1895  elog(WARNING, "leaked hash_seq_search scan for hash table %p",
1896  seq_scan_tables[i]);
1897  }
1898  }
1899  num_seq_scans = 0;
1900 }
1901 
1902 /* Clean up any open scans at end of subtransaction */
1903 void
1904 AtEOSubXact_HashTables(bool isCommit, int nestDepth)
1905 {
1906  int i;
1907 
1908  /*
1909  * Search backward to make cleanup easy. Note we must check all entries,
1910  * not only those at the end of the array, because deletion technique
1911  * doesn't keep them in order.
1912  */
1913  for (i = num_seq_scans - 1; i >= 0; i--)
1914  {
1915  if (seq_scan_level[i] >= nestDepth)
1916  {
1917  if (isCommit)
1918  elog(WARNING, "leaked hash_seq_search scan for hash table %p",
1919  seq_scan_tables[i]);
1922  num_seq_scans--;
1923  }
1924  }
1925 }
unsigned int uint32
Definition: c.h:442
#define MAXALIGN(LEN)
Definition: c.h:747
unsigned char bool
Definition: c.h:392
#define MemSet(start, val, len)
Definition: c.h:953
void(* pg_funcptr_t)(void)
Definition: c.h:352
size_t Size
Definition: c.h:541
static HTAB * seq_scan_tables[MAX_SEQ_SCANS]
Definition: dynahash.c:1824
static int seq_scan_level[MAX_SEQ_SCANS]
Definition: dynahash.c:1825
#define ELEMENT_FROM_KEY(key)
Definition: dynahash.c:249
#define DEF_DIRSIZE
Definition: dynahash.c:125
static void * DynaHashAlloc(Size size)
Definition: dynahash.c:289
static bool element_alloc(HTAB *hashp, int nelem, int freelist_idx)
Definition: dynahash.c:1699
void AtEOXact_HashTables(bool isCommit)
Definition: dynahash.c:1878
static bool init_htab(HTAB *hashp, long nelem)
Definition: dynahash.c:687
static HASHSEGMENT seg_alloc(HTAB *hashp)
Definition: dynahash.c:1680
#define MAX_SEQ_SCANS
Definition: dynahash.c:1822
static MemoryContext CurrentDynaHashCxt
Definition: dynahash.c:286
static int choose_nelem_alloc(Size entrysize)
Definition: dynahash.c:654
static int next_pow2_int(long num)
Definition: dynahash.c:1786
Size hash_get_shared_size(HASHCTL *info, int flags)
Definition: dynahash.c:852
static void register_seq_scan(HTAB *hashp)
Definition: dynahash.c:1831
#define MOD(x, y)
Definition: dynahash.c:255
#define IS_PARTITIONED(hctl)
Definition: dynahash.c:210
#define DEF_SEGSIZE_SHIFT
Definition: dynahash.c:124
void AtEOSubXact_HashTables(bool isCommit, int nestDepth)
Definition: dynahash.c:1904
static HASHBUCKET get_hash_entry(HTAB *hashp, int freelist_idx)
Definition: dynahash.c:1292
#define NUM_FREELISTS
Definition: dynahash.c:128
void hash_destroy(HTAB *hashp)
Definition: dynahash.c:863
static int string_compare(const char *key1, const char *key2, Size keysize)
Definition: dynahash.c:305
void * hash_search(HTAB *hashp, const void *keyPtr, HASHACTION action, bool *foundPtr)
Definition: dynahash.c:953
static bool expand_table(HTAB *hashp)
Definition: dynahash.c:1544
static void hdefault(HTAB *hashp)
Definition: dynahash.c:627
static void deregister_seq_scan(HTAB *hashp)
Definition: dynahash.c:1843
#define ELEMENTKEY(helem)
Definition: dynahash.c:244
void hash_seq_term(HASH_SEQ_STATUS *status)
Definition: dynahash.c:1507
#define DEF_SEGSIZE
Definition: dynahash.c:123
static int num_seq_scans
Definition: dynahash.c:1826
int my_log2(long num)
Definition: dynahash.c:1760
HTAB * hash_create(const char *tabname, long nelem, const HASHCTL *info, int flags)
Definition: dynahash.c:350
#define FREELIST_IDX(hctl, hashcode)
Definition: dynahash.c:212
long hash_get_num_entries(HTAB *hashp)
Definition: dynahash.c:1377
long hash_select_dirsize(long num_entries)
Definition: dynahash.c:828
static void hash_corrupted(HTAB *hashp)
Definition: dynahash.c:1746
Size hash_estimate_size(long num_entries, Size entrysize)
Definition: dynahash.c:781
void hash_stats(const char *where, HTAB *hashp)
Definition: dynahash.c:882
void hash_freeze(HTAB *hashp)
Definition: dynahash.c:1527
static bool dir_realloc(HTAB *hashp)
Definition: dynahash.c:1641
bool hash_update_hash_key(HTAB *hashp, void *existingEntry, const void *newKeyPtr)
Definition: dynahash.c:1157
HASHELEMENT * HASHBUCKET
Definition: dynahash.c:131
uint32 get_hash_value(HTAB *hashp, const void *keyPtr)
Definition: dynahash.c:909
static uint32 calc_bucket(HASHHDR *hctl, uint32 hash_val)
Definition: dynahash.c:916
static bool has_seq_scans(HTAB *hashp)
Definition: dynahash.c:1864
static long next_pow2_long(long num)
Definition: dynahash.c:1778
void * hash_search_with_hash_value(HTAB *hashp, const void *keyPtr, uint32 hashvalue, HASHACTION action, bool *foundPtr)
Definition: dynahash.c:966
void * hash_seq_search(HASH_SEQ_STATUS *status)
Definition: dynahash.c:1431
void hash_seq_init(HASH_SEQ_STATUS *status, HTAB *hashp)
Definition: dynahash.c:1421
HASHBUCKET * HASHSEGMENT
Definition: dynahash.c:134
int errcode(int sqlerrcode)
Definition: elog.c:695
int errmsg(const char *fmt,...)
Definition: elog.c:906
#define FATAL
Definition: elog.h:37
#define WARNING
Definition: elog.h:32
#define PANIC
Definition: elog.h:38
#define ERROR
Definition: elog.h:35
#define ereport(elevel,...)
Definition: elog.h:145
#define MCXT_ALLOC_NO_OOM
Definition: fe_memutils.h:17
uint32 tag_hash(const void *key, Size keysize)
Definition: hashfn.c:677
uint32 uint32_hash(const void *key, Size keysize)
Definition: hashfn.c:688
uint32 string_hash(const void *key, Size keysize)
Definition: hashfn.c:660
#define HASH_KEYCOPY
Definition: hsearch.h:100
#define HASH_STRINGS
Definition: hsearch.h:96
int(* HashCompareFunc)(const void *key1, const void *key2, Size keysize)
Definition: hsearch.h:29
HASHACTION
Definition: hsearch.h:112
@ HASH_FIND
Definition: hsearch.h:113
@ HASH_REMOVE
Definition: hsearch.h:115
@ HASH_ENTER
Definition: hsearch.h:114
@ HASH_ENTER_NULL
Definition: hsearch.h:116
#define HASH_CONTEXT
Definition: hsearch.h:102
#define NO_MAX_DSIZE
Definition: hsearch.h:108
#define HASH_ELEM
Definition: hsearch.h:95
#define HASH_ALLOC
Definition: hsearch.h:101
#define HASH_DIRSIZE
Definition: hsearch.h:94
uint32(* HashValueFunc)(const void *key, Size keysize)
Definition: hsearch.h:21
void *(* HashAllocFunc)(Size request)
Definition: hsearch.h:44
#define HASH_SEGMENT
Definition: hsearch.h:93
#define HASH_ATTACH
Definition: hsearch.h:104
#define HASH_COMPARE
Definition: hsearch.h:99
struct HASHHDR HASHHDR
Definition: hsearch.h:58
#define HASH_FUNCTION
Definition: hsearch.h:98
#define HASH_BLOBS
Definition: hsearch.h:97
#define HASH_SHARED_MEM
Definition: hsearch.h:103
#define HASH_FIXED_SIZE
Definition: hsearch.h:105
#define HASH_PARTITION
Definition: hsearch.h:92
void *(* HashCopyFunc)(void *dest, const void *src, Size keysize)
Definition: hsearch.h:37
int i
Definition: isn.c:73
Assert(fmt[strlen(fmt) - 1] !='\n')
void pfree(void *pointer)
Definition: mcxt.c:1306
MemoryContext TopMemoryContext
Definition: mcxt.c:130
void * MemoryContextAllocExtended(MemoryContext context, Size size, int flags)
Definition: mcxt.c:1110
void MemoryContextDelete(MemoryContext context)
Definition: mcxt.c:376
void MemoryContextSetIdentifier(MemoryContext context, const char *id)
Definition: mcxt.c:494
#define MemoryContextIsValid(context)
Definition: memnodes.h:107
#define AllocSetContextCreate
Definition: memutils.h:129
#define ALLOCSET_DEFAULT_SIZES
Definition: memutils.h:153
static uint64 pg_ceil_log2_64(uint64 num)
Definition: pg_bitutils.h:222
static uint32 pg_ceil_log2_32(uint32 num)
Definition: pg_bitutils.h:209
static void static void status(const char *fmt,...) pg_attribute_printf(1
Definition: pg_regress.c:225
#define fprintf
Definition: port.h:242
size_t strlcpy(char *dst, const char *src, size_t siz)
Definition: strlcpy.c:45
int slock_t
Definition: s_lock.h:754
Size add_size(Size s1, Size s2)
Definition: shmem.c:502
Size mul_size(Size s1, Size s2)
Definition: shmem.c:519
#define SpinLockInit(lock)
Definition: spin.h:60
#define SpinLockRelease(lock)
Definition: spin.h:64
#define SpinLockAcquire(lock)
Definition: spin.h:62
slock_t mutex
Definition: dynahash.c:155
HASHELEMENT * freeList
Definition: dynahash.c:157
long nentries
Definition: dynahash.c:156
long ssize
Definition: hsearch.h:70
HashAllocFunc alloc
Definition: hsearch.h:84
Size keysize
Definition: hsearch.h:75
HashValueFunc hash
Definition: hsearch.h:78
Size entrysize
Definition: hsearch.h:76
long dsize
Definition: hsearch.h:72
HashCompareFunc match
Definition: hsearch.h:80
HASHHDR * hctl
Definition: hsearch.h:88
MemoryContext hcxt
Definition: hsearch.h:86
long num_partitions
Definition: hsearch.h:68
HashCopyFunc keycopy
Definition: hsearch.h:82
long max_dsize
Definition: hsearch.h:73
struct HASHELEMENT * link
Definition: hsearch.h:53
uint32 hashvalue
Definition: hsearch.h:54
long max_dsize
Definition: dynahash.c:194
long nsegs
Definition: dynahash.c:185
uint32 high_mask
Definition: dynahash.c:187
long num_partitions
Definition: dynahash.c:193
FreeListData freeList[NUM_FREELISTS]
Definition: dynahash.c:180
Size entrysize
Definition: dynahash.c:192
uint32 max_bucket
Definition: dynahash.c:186
Size keysize
Definition: dynahash.c:191
int nelem_alloc
Definition: dynahash.c:197
uint32 low_mask
Definition: dynahash.c:188
int sshift
Definition: dynahash.c:196
long ssize
Definition: dynahash.c:195
long dsize
Definition: dynahash.c:184
Definition: dynahash.c:220
bool isfixed
Definition: dynahash.c:230
bool isshared
Definition: dynahash.c:229
HashCompareFunc match
Definition: dynahash.c:224
char * tabname
Definition: dynahash.c:228
HASHHDR * hctl
Definition: dynahash.c:221
MemoryContext hcxt
Definition: dynahash.c:227
HashAllocFunc alloc
Definition: dynahash.c:226
HashValueFunc hash
Definition: dynahash.c:223
long ssize
Definition: dynahash.c:237
HASHSEGMENT * dir
Definition: dynahash.c:222
Size keysize
Definition: dynahash.c:236
int sshift
Definition: dynahash.c:238
HashCopyFunc keycopy
Definition: dynahash.c:225
bool frozen
Definition: dynahash.c:233
int GetCurrentTransactionNestLevel(void)
Definition: xact.c:913