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dynahash.c
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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 */
122 
123 /* A hash segment is an array of bucket headers */
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  */
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  */
278 
279 static void *
281 {
282  Assert(MemoryContextIsValid(CurrentDynaHashCxt));
283  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 string_compare(const char *key1, const char *key2, Size keysize)
296 {
297  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 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  if (flags & HASH_SHARED_MEM)
334  {
335  /* Set up to allocate the hash header */
336  CurrentDynaHashCxt = TopMemoryContext;
337  }
338  else
339  {
340  /* Create the hash table's private memory context */
341  if (flags & HASH_CONTEXT)
342  CurrentDynaHashCxt = info->hcxt;
343  else
344  CurrentDynaHashCxt = TopMemoryContext;
345  CurrentDynaHashCxt = AllocSetContextCreate(CurrentDynaHashCxt,
346  "dynahash",
348  }
349 
350  /* Initialize the hash header, plus a copy of the table name */
351  hashp = (HTAB *) DynaHashAlloc(sizeof(HTAB) + strlen(tabname) + 1);
352  MemSet(hashp, 0, sizeof(HTAB));
353 
354  hashp->tabname = (char *) (hashp + 1);
355  strcpy(hashp->tabname, tabname);
356 
357  /* If we have a private context, label it with hashtable's name */
358  if (!(flags & HASH_SHARED_MEM))
359  MemoryContextSetIdentifier(CurrentDynaHashCxt, hashp->tabname);
360 
361  /*
362  * Select the appropriate hash function (see comments at head of file).
363  */
364  if (flags & HASH_FUNCTION)
365  hashp->hash = info->hash;
366  else if (flags & HASH_BLOBS)
367  {
368  /* We can optimize hashing for common key sizes */
369  Assert(flags & HASH_ELEM);
370  if (info->keysize == sizeof(uint32))
371  hashp->hash = uint32_hash;
372  else
373  hashp->hash = tag_hash;
374  }
375  else
376  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  if (flags & HASH_COMPARE)
389  hashp->match = info->match;
390  else if (hashp->hash == string_hash)
392  else
393  hashp->match = memcmp;
394 
395  /*
396  * Similarly, the key-copying function defaults to strlcpy or memcpy.
397  */
398  if (flags & HASH_KEYCOPY)
399  hashp->keycopy = info->keycopy;
400  else if (hashp->hash == string_hash)
401  hashp->keycopy = (HashCopyFunc) strlcpy;
402  else
403  hashp->keycopy = memcpy;
404 
405  /* And select the entry allocation function, too. */
406  if (flags & HASH_ALLOC)
407  hashp->alloc = info->alloc;
408  else
409  hashp->alloc = DynaHashAlloc;
410 
411  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  hashp->hctl = info->hctl;
419  hashp->dir = (HASHSEGMENT *) (((char *) info->hctl) + sizeof(HASHHDR));
420  hashp->hcxt = NULL;
421  hashp->isshared = true;
422 
423  /* hash table already exists, we're just attaching to it */
424  if (flags & HASH_ATTACH)
425  {
426  /* make local copies of some heavily-used values */
427  hctl = hashp->hctl;
428  hashp->keysize = hctl->keysize;
429  hashp->ssize = hctl->ssize;
430  hashp->sshift = hctl->sshift;
431 
432  return hashp;
433  }
434  }
435  else
436  {
437  /* setup hash table defaults */
438  hashp->hctl = NULL;
439  hashp->dir = NULL;
440  hashp->hcxt = CurrentDynaHashCxt;
441  hashp->isshared = false;
442  }
443 
444  if (!hashp->hctl)
445  {
446  hashp->hctl = (HASHHDR *) hashp->alloc(sizeof(HASHHDR));
447  if (!hashp->hctl)
448  ereport(ERROR,
449  (errcode(ERRCODE_OUT_OF_MEMORY),
450  errmsg("out of memory")));
451  }
452 
453  hashp->frozen = false;
454 
455  hdefault(hashp);
456 
457  hctl = hashp->hctl;
458 
459  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  */
470 
471  hctl->num_partitions = info->num_partitions;
472  }
473 
474  if (flags & HASH_SEGMENT)
475  {
476  hctl->ssize = info->ssize;
477  hctl->sshift = my_log2(info->ssize);
478  /* ssize had better be a power of 2 */
479  Assert(hctl->ssize == (1L << hctl->sshift));
480  }
481  if (flags & HASH_FFACTOR)
482  hctl->ffactor = info->ffactor;
483 
484  /*
485  * SHM hash tables have fixed directory size passed by the caller.
486  */
487  if (flags & HASH_DIRSIZE)
488  {
489  hctl->max_dsize = info->max_dsize;
490  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  if (flags & HASH_ELEM)
498  {
499  Assert(info->entrysize >= info->keysize);
500  hctl->keysize = info->keysize;
501  hctl->entrysize = info->entrysize;
502  }
503 
504  /* make local copies of heavily-used constant fields */
505  hashp->keysize = hctl->keysize;
506  hashp->ssize = hctl->ssize;
507  hashp->sshift = hctl->sshift;
508 
509  /* Build the hash directory structure */
510  if (!init_htab(hashp, nelem))
511  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  if ((flags & HASH_SHARED_MEM) ||
522  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  if (IS_PARTITIONED(hashp->hctl))
534  freelist_partitions = NUM_FREELISTS;
535  else
536  freelist_partitions = 1;
537 
538  nelem_alloc = nelem / freelist_partitions;
539  if (nelem_alloc <= 0)
540  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  if (nelem_alloc * freelist_partitions < nelem)
547  nelem_alloc_first =
548  nelem - nelem_alloc * (freelist_partitions - 1);
549  else
550  nelem_alloc_first = nelem_alloc;
551 
552  for (i = 0; i < freelist_partitions; i++)
553  {
554  int temp = (i == 0) ? nelem_alloc_first : nelem_alloc;
555 
556  if (!element_alloc(hashp, temp, i))
557  ereport(ERROR,
558  (errcode(ERRCODE_OUT_OF_MEMORY),
559  errmsg("out of memory")));
560  }
561  }
562 
563  if (flags & HASH_FIXED_SIZE)
564  hashp->isfixed = true;
565  return hashp;
566 }
567 
568 /*
569  * Set default HASHHDR parameters.
570  */
571 static void
572 hdefault(HTAB *hashp)
573 {
574  HASHHDR *hctl = hashp->hctl;
575 
576  MemSet(hctl, 0, sizeof(HASHHDR));
577 
578  hctl->dsize = DEF_DIRSIZE;
579  hctl->nsegs = 0;
580 
581  /* rather pointless defaults for key & entry size */
582  hctl->keysize = sizeof(char *);
583  hctl->entrysize = 2 * sizeof(char *);
584 
585  hctl->num_partitions = 0; /* not partitioned */
586 
587  hctl->ffactor = DEF_FFACTOR;
588 
589  /* table has no fixed maximum size */
590  hctl->max_dsize = NO_MAX_DSIZE;
591 
592  hctl->ssize = DEF_SEGSIZE;
593  hctl->sshift = DEF_SEGSIZE_SHIFT;
594 
595 #ifdef HASH_STATISTICS
596  hctl->accesses = hctl->collisions = 0;
597 #endif
598 }
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
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  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  allocSize = 32 * 4; /* assume elementSize at least 8 */
624  do
625  {
626  allocSize <<= 1;
627  nelem_alloc = allocSize / elementSize;
628  } while (nelem_alloc < 32);
629 
630  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 init_htab(HTAB *hashp, long nelem)
639 {
640  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  if (IS_PARTITIONED(hctl))
650  for (i = 0; i < NUM_FREELISTS; i++)
651  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  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  while (nbuckets < hctl->num_partitions)
667  nbuckets <<= 1;
668 
669  hctl->max_bucket = hctl->low_mask = nbuckets - 1;
670  hctl->high_mask = (nbuckets << 1) - 1;
671 
672  /*
673  * Figure number of directory segments needed, round up to a power of 2
674  */
675  nsegs = (nbuckets - 1) / hctl->ssize + 1;
676  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  if (nsegs > hctl->dsize)
683  {
684  if (!(hashp->dir))
685  hctl->dsize = nsegs;
686  else
687  return false;
688  }
689 
690  /* Allocate a directory */
691  if (!(hashp->dir))
692  {
693  CurrentDynaHashCxt = hashp->hcxt;
694  hashp->dir = (HASHSEGMENT *)
695  hashp->alloc(hctl->dsize * sizeof(HASHSEGMENT));
696  if (!hashp->dir)
697  return false;
698  }
699 
700  /* Allocate initial segments */
701  for (segp = hashp->dir; hctl->nsegs < nsegs; hctl->nsegs++, segp++)
702  {
703  *segp = seg_alloc(hashp);
704  if (*segp == NULL)
705  return false;
706  }
707 
708  /* Choose number of entries to allocate at a time */
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  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
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  nBuckets = next_pow2_long((num_entries - 1) / DEF_FFACTOR + 1);
746  /* # of segments needed for nBuckets */
747  nSegments = next_pow2_long((nBuckets - 1) / DEF_SEGSIZE + 1);
748  /* directory entries */
749  nDirEntries = DEF_DIRSIZE;
750  while (nDirEntries < nSegments)
751  nDirEntries <<= 1; /* dir_alloc doubles dsize at each call */
752 
753  /* fixed control info */
754  size = MAXALIGN(sizeof(HASHHDR)); /* but not HTAB, per above */
755  /* directory */
756  size = add_size(size, mul_size(nDirEntries, sizeof(HASHSEGMENT)));
757  /* segments */
758  size = add_size(size, mul_size(nSegments,
759  MAXALIGN(DEF_SEGSIZE * sizeof(HASHBUCKET))));
760  /* elements --- allocated in groups of choose_nelem_alloc() entries */
761  elementAllocCnt = choose_nelem_alloc(entrysize);
762  nElementAllocs = (num_entries - 1) / elementAllocCnt + 1;
763  elementSize = MAXALIGN(sizeof(HASHELEMENT)) + MAXALIGN(entrysize);
764  size = add_size(size,
765  mul_size(nElementAllocs,
766  mul_size(elementAllocCnt, elementSize)));
767 
768  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 hash_select_dirsize(long num_entries)
782 {
783  long nBuckets,
784  nSegments,
785  nDirEntries;
786 
787  /* estimate number of buckets wanted */
788  nBuckets = next_pow2_long((num_entries - 1) / DEF_FFACTOR + 1);
789  /* # of segments needed for nBuckets */
790  nSegments = next_pow2_long((nBuckets - 1) / DEF_SEGSIZE + 1);
791  /* directory entries */
792  nDirEntries = DEF_DIRSIZE;
793  while (nDirEntries < nSegments)
794  nDirEntries <<= 1; /* dir_alloc doubles dsize at each call */
795 
796  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 hash_get_shared_size(HASHCTL *info, int flags)
806 {
807  Assert(flags & HASH_DIRSIZE);
808  Assert(info->dsize == info->max_dsize);
809  return sizeof(HASHHDR) + info->dsize * sizeof(HASHSEGMENT);
810 }
811 
812 
813 /********************** DESTROY ROUTINES ************************/
814 
815 void
817 {
818  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  hash_stats("destroy", hashp);
826 
827  /*
828  * Free everything by destroying the hash table's memory context.
829  */
830  MemoryContextDelete(hashp->hcxt);
831  }
832 }
833 
834 void
835 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 }
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 get_hash_value(HTAB *hashp, const void *keyPtr)
863 {
864  return hashp->hash(keyPtr, hashp->keysize);
865 }
866 
867 /* Convert a hash value to a bucket number */
868 static inline uint32
869 calc_bucket(HASHHDR *hctl, uint32 hash_val)
870 {
871  uint32 bucket;
872 
873  bucket = hash_val & hctl->high_mask;
874  if (bucket > hctl->max_bucket)
875  bucket = bucket & hctl->low_mask;
876 
877  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 *
909  const void *keyPtr,
911  bool *foundPtr)
912 {
913  return hash_search_with_hash_value(hashp,
914  keyPtr,
915  hashp->hash(keyPtr, hashp->keysize),
916  action,
917  foundPtr);
918 }
919 
920 void *
922  const void *keyPtr,
923  uint32 hashvalue,
925  bool *foundPtr)
926 {
927  HASHHDR *hctl = hashp->hctl;
928  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  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  if (!IS_PARTITIONED(hctl) && !hashp->frozen &&
959  hctl->freeList[0].nentries / (long) (hctl->max_bucket + 1) >= hctl->ffactor &&
960  !has_seq_scans(hashp))
961  (void) expand_table(hashp);
962  }
963 
964  /*
965  * Do the initial lookup
966  */
967  bucket = calc_bucket(hctl, hashvalue);
968 
969  segment_num = bucket >> hashp->sshift;
970  segment_ndx = MOD(bucket, hashp->ssize);
971 
972  segp = hashp->dir[segment_num];
973 
974  if (segp == NULL)
975  hash_corrupted(hashp);
976 
977  prevBucketPtr = &segp[segment_ndx];
978  currBucket = *prevBucketPtr;
979 
980  /*
981  * Follow collision chain looking for matching key
982  */
983  match = hashp->match; /* save one fetch in inner loop */
984  keysize = hashp->keysize; /* ditto */
985 
986  while (currBucket != NULL)
987  {
988  if (currBucket->hashvalue == hashvalue &&
989  match(ELEMENTKEY(currBucket), keyPtr, keysize) == 0)
990  break;
991  prevBucketPtr = &(currBucket->link);
992  currBucket = *prevBucketPtr;
993 #ifdef HASH_STATISTICS
994  hash_collisions++;
995  hctl->collisions++;
996 #endif
997  }
998 
999  if (foundPtr)
1000  *foundPtr = (bool) (currBucket != NULL);
1001 
1002  /*
1003  * OK, now what?
1004  */
1005  switch (action)
1006  {
1007  case HASH_FIND:
1008  if (currBucket != NULL)
1009  return (void *) ELEMENTKEY(currBucket);
1010  return NULL;
1011 
1012  case HASH_REMOVE:
1013  if (currBucket != NULL)
1014  {
1015  /* if partitioned, must lock to touch nentries and freeList */
1016  if (IS_PARTITIONED(hctl))
1017  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  hctl->freeList[freelist_idx].nentries--;
1022 
1023  /* remove record from hash bucket's chain. */
1024  *prevBucketPtr = currBucket->link;
1025 
1026  /* add the record to the appropriate freelist. */
1027  currBucket->link = hctl->freeList[freelist_idx].freeList;
1028  hctl->freeList[freelist_idx].freeList = currBucket;
1029 
1030  if (IS_PARTITIONED(hctl))
1031  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  return (void *) ELEMENTKEY(currBucket);
1039  }
1040  return NULL;
1041 
1042  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  if (currBucket != NULL)
1050  return (void *) ELEMENTKEY(currBucket);
1051 
1052  /* disallow inserts if frozen */
1053  if (hashp->frozen)
1054  elog(ERROR, "cannot insert into frozen hashtable \"%s\"",
1055  hashp->tabname);
1056 
1057  currBucket = get_hash_entry(hashp, freelist_idx);
1058  if (currBucket == NULL)
1059  {
1060  /* out of memory */
1061  if (action == HASH_ENTER_NULL)
1062  return NULL;
1063  /* report a generic message */
1064  if (hashp->isshared)
1065  ereport(ERROR,
1066  (errcode(ERRCODE_OUT_OF_MEMORY),
1067  errmsg("out of shared memory")));
1068  else
1069  ereport(ERROR,
1070  (errcode(ERRCODE_OUT_OF_MEMORY),
1071  errmsg("out of memory")));
1072  }
1073 
1074  /* link into hashbucket chain */
1075  *prevBucketPtr = currBucket;
1076  currBucket->link = NULL;
1077 
1078  /* copy key into record */
1079  currBucket->hashvalue = hashvalue;
1080  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  return (void *) ELEMENTKEY(currBucket);
1090  }
1091 
1092  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
1118  void *existingEntry,
1119  const void *newKeyPtr)
1120 {
1121  HASHELEMENT *existingElement = ELEMENT_FROM_KEY(existingEntry);
1122  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  if (hashp->frozen)
1142  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  bucket = calc_bucket(hctl, existingElement->hashvalue);
1151 
1152  segment_num = bucket >> hashp->sshift;
1153  segment_ndx = MOD(bucket, hashp->ssize);
1154 
1155  segp = hashp->dir[segment_num];
1156 
1157  if (segp == NULL)
1158  hash_corrupted(hashp);
1159 
1160  prevBucketPtr = &segp[segment_ndx];
1161  currBucket = *prevBucketPtr;
1162 
1163  while (currBucket != NULL)
1164  {
1165  if (currBucket == existingElement)
1166  break;
1167  prevBucketPtr = &(currBucket->link);
1168  currBucket = *prevBucketPtr;
1169  }
1170 
1171  if (currBucket == NULL)
1172  elog(ERROR, "hash_update_hash_key argument is not in hashtable \"%s\"",
1173  hashp->tabname);
1174 
1175  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  newhashvalue = hashp->hash(newKeyPtr, hashp->keysize);
1182 
1183  newbucket = calc_bucket(hctl, newhashvalue);
1184 
1185  segment_num = newbucket >> hashp->sshift;
1186  segment_ndx = MOD(newbucket, hashp->ssize);
1187 
1188  segp = hashp->dir[segment_num];
1189 
1190  if (segp == NULL)
1191  hash_corrupted(hashp);
1192 
1193  prevBucketPtr = &segp[segment_ndx];
1194  currBucket = *prevBucketPtr;
1195 
1196  /*
1197  * Follow collision chain looking for matching key
1198  */
1199  match = hashp->match; /* save one fetch in inner loop */
1200  keysize = hashp->keysize; /* ditto */
1201 
1202  while (currBucket != NULL)
1203  {
1204  if (currBucket->hashvalue == newhashvalue &&
1205  match(ELEMENTKEY(currBucket), newKeyPtr, keysize) == 0)
1206  break;
1207  prevBucketPtr = &(currBucket->link);
1208  currBucket = *prevBucketPtr;
1209 #ifdef HASH_STATISTICS
1210  hash_collisions++;
1211  hctl->collisions++;
1212 #endif
1213  }
1214 
1215  if (currBucket != NULL)
1216  return false; /* collision with an existing entry */
1217 
1218  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  if (bucket != newbucket)
1228  {
1229  /* OK to remove record from old hash bucket's chain. */
1230  *oldPrevPtr = currBucket->link;
1231 
1232  /* link into new hashbucket chain */
1233  *prevBucketPtr = currBucket;
1234  currBucket->link = NULL;
1235  }
1236 
1237  /* copy new key into record */
1238  currBucket->hashvalue = newhashvalue;
1239  hashp->keycopy(ELEMENTKEY(currBucket), newKeyPtr, keysize);
1240 
1241  /* rest of record is untouched */
1242 
1243  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 get_hash_entry(HTAB *hashp, int freelist_idx)
1253 {
1254  HASHHDR *hctl = hashp->hctl;
1255  HASHBUCKET newElement;
1256 
1257  for (;;)
1258  {
1259  /* if partitioned, must lock to touch nentries and freeList */
1260  if (IS_PARTITIONED(hctl))
1261  SpinLockAcquire(&hctl->freeList[freelist_idx].mutex);
1262 
1263  /* try to get an entry from the freelist */
1264  newElement = hctl->freeList[freelist_idx].freeList;
1265 
1266  if (newElement != NULL)
1267  break;
1268 
1269  if (IS_PARTITIONED(hctl))
1270  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  if (!element_alloc(hashp, hctl->nelem_alloc, freelist_idx))
1285  {
1286  int borrow_from_idx;
1287 
1288  if (!IS_PARTITIONED(hctl))
1289  return NULL; /* out of memory */
1290 
1291  /* try to borrow element from another freelist */
1292  borrow_from_idx = freelist_idx;
1293  for (;;)
1294  {
1295  borrow_from_idx = (borrow_from_idx + 1) % NUM_FREELISTS;
1296  if (borrow_from_idx == freelist_idx)
1297  break; /* examined all freelists, fail */
1298 
1299  SpinLockAcquire(&(hctl->freeList[borrow_from_idx].mutex));
1300  newElement = hctl->freeList[borrow_from_idx].freeList;
1301 
1302  if (newElement != NULL)
1303  {
1304  hctl->freeList[borrow_from_idx].freeList = newElement->link;
1305  SpinLockRelease(&(hctl->freeList[borrow_from_idx].mutex));
1306 
1307  /* careful: count the new element in its proper freelist */
1308  SpinLockAcquire(&hctl->freeList[freelist_idx].mutex);
1309  hctl->freeList[freelist_idx].nentries++;
1310  SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1311 
1312  return newElement;
1313  }
1314 
1315  SpinLockRelease(&(hctl->freeList[borrow_from_idx].mutex));
1316  }
1317 
1318  /* no elements available to borrow either, so out of memory */
1319  return NULL;
1320  }
1321  }
1322 
1323  /* remove entry from freelist, bump nentries */
1324  hctl->freeList[freelist_idx].freeList = newElement->link;
1325  hctl->freeList[freelist_idx].nentries++;
1326 
1327  if (IS_PARTITIONED(hctl))
1328  SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1329 
1330  return newElement;
1331 }
1332 
1333 /*
1334  * hash_get_num_entries -- get the number of entries in a hashtable
1335  */
1336 long
1338 {
1339  int i;
1340  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  if (IS_PARTITIONED(hashp->hctl))
1348  {
1349  for (i = 1; i < NUM_FREELISTS; i++)
1350  sum += hashp->hctl->freeList[i].nentries;
1351  }
1352 
1353  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
1382 {
1383  status->hashp = hashp;
1384  status->curBucket = 0;
1385  status->curEntry = NULL;
1386  if (!hashp->frozen)
1387  register_seq_scan(hashp);
1388 }
1389 
1390 void *
1392 {
1393  HTAB *hashp;
1394  HASHHDR *hctl;
1396  long ssize;
1397  long segment_num;
1398  long segment_ndx;
1399  HASHSEGMENT segp;
1400  uint32 curBucket;
1401  HASHELEMENT *curElem;
1402 
1403  if ((curElem = status->curEntry) != NULL)
1404  {
1405  /* Continuing scan of curBucket... */
1406  status->curEntry = curElem->link;
1407  if (status->curEntry == NULL) /* end of this bucket */
1408  ++status->curBucket;
1409  return (void *) ELEMENTKEY(curElem);
1410  }
1411 
1412  /*
1413  * Search for next nonempty bucket starting at curBucket.
1414  */
1415  curBucket = status->curBucket;
1416  hashp = status->hashp;
1417  hctl = hashp->hctl;
1418  ssize = hashp->ssize;
1419  max_bucket = hctl->max_bucket;
1420 
1421  if (curBucket > max_bucket)
1422  {
1423  hash_seq_term(status);
1424  return NULL; /* search is done */
1425  }
1426 
1427  /*
1428  * first find the right segment in the table directory.
1429  */
1430  segment_num = curBucket >> hashp->sshift;
1431  segment_ndx = MOD(curBucket, ssize);
1432 
1433  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  while ((curElem = segp[segment_ndx]) == NULL)
1442  {
1443  /* empty bucket, advance to next */
1444  if (++curBucket > max_bucket)
1445  {
1446  status->curBucket = curBucket;
1447  hash_seq_term(status);
1448  return NULL; /* search is done */
1449  }
1450  if (++segment_ndx >= ssize)
1451  {
1452  segment_num++;
1453  segment_ndx = 0;
1454  segp = hashp->dir[segment_num];
1455  }
1456  }
1457 
1458  /* Begin scan of curBucket... */
1459  status->curEntry = curElem->link;
1460  if (status->curEntry == NULL) /* end of this bucket */
1461  ++curBucket;
1462  status->curBucket = curBucket;
1463  return (void *) ELEMENTKEY(curElem);
1464 }
1465 
1466 void
1468 {
1469  if (!status->hashp->frozen)
1470  deregister_seq_scan(status->hashp);
1471 }
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
1488 {
1489  if (hashp->isshared)
1490  elog(ERROR, "cannot freeze shared hashtable \"%s\"", hashp->tabname);
1491  if (!hashp->frozen && has_seq_scans(hashp))
1492  elog(ERROR, "cannot freeze hashtable \"%s\" because it has active scans",
1493  hashp->tabname);
1494  hashp->frozen = true;
1495 }
1496 
1497 
1498 /********************************* UTILITIES ************************/
1499 
1500 /*
1501  * Expand the table by adding one more hash bucket.
1502  */
1503 static bool
1505 {
1506  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  new_bucket = hctl->max_bucket + 1;
1527  new_segnum = new_bucket >> hashp->sshift;
1528  new_segndx = MOD(new_bucket, hashp->ssize);
1529 
1530  if (new_segnum >= hctl->nsegs)
1531  {
1532  /* Allocate new segment if necessary -- could fail if dir full */
1533  if (new_segnum >= hctl->dsize)
1534  if (!dir_realloc(hashp))
1535  return false;
1536  if (!(hashp->dir[new_segnum] = seg_alloc(hashp)))
1537  return false;
1538  hctl->nsegs++;
1539  }
1540 
1541  /* OK, we created a new bucket */
1542  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  old_bucket = (new_bucket & hctl->low_mask);
1551 
1552  /*
1553  * If we crossed a power of 2, readjust masks.
1554  */
1555  if ((uint32) new_bucket > hctl->high_mask)
1556  {
1557  hctl->low_mask = hctl->high_mask;
1558  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  old_segnum = old_bucket >> hashp->sshift;
1568  old_segndx = MOD(old_bucket, hashp->ssize);
1569 
1570  old_seg = hashp->dir[old_segnum];
1571  new_seg = hashp->dir[new_segnum];
1572 
1573  oldlink = &old_seg[old_segndx];
1574  newlink = &new_seg[new_segndx];
1575 
1576  for (currElement = *oldlink;
1577  currElement != NULL;
1578  currElement = nextElement)
1579  {
1580  nextElement = currElement->link;
1581  if ((long) calc_bucket(hctl, currElement->hashvalue) == old_bucket)
1582  {
1583  *oldlink = currElement;
1584  oldlink = &currElement->link;
1585  }
1586  else
1587  {
1588  *newlink = currElement;
1589  newlink = &currElement->link;
1590  }
1591  }
1592  /* don't forget to terminate the rebuilt hash chains... */
1593  *oldlink = NULL;
1594  *newlink = NULL;
1595 
1596  return true;
1597 }
1598 
1599 
1600 static bool
1602 {
1603  HASHSEGMENT *p;
1604  HASHSEGMENT *old_p;
1605  long new_dsize;
1606  long old_dirsize;
1607  long new_dirsize;
1608 
1609  if (hashp->hctl->max_dsize != NO_MAX_DSIZE)
1610  return false;
1611 
1612  /* Reallocate directory */
1613  new_dsize = hashp->hctl->dsize << 1;
1614  old_dirsize = hashp->hctl->dsize * sizeof(HASHSEGMENT);
1615  new_dirsize = new_dsize * sizeof(HASHSEGMENT);
1616 
1617  old_p = hashp->dir;
1618  CurrentDynaHashCxt = hashp->hcxt;
1619  p = (HASHSEGMENT *) hashp->alloc((Size) new_dirsize);
1620 
1621  if (p != NULL)
1622  {
1623  memcpy(p, old_p, old_dirsize);
1624  MemSet(((char *) p) + old_dirsize, 0, new_dirsize - old_dirsize);
1625  hashp->dir = p;
1626  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  pfree(old_p);
1631 
1632  return true;
1633  }
1634 
1635  return false;
1636 }
1637 
1638 
1639 static HASHSEGMENT
1641 {
1642  HASHSEGMENT segp;
1643 
1644  CurrentDynaHashCxt = hashp->hcxt;
1645  segp = (HASHSEGMENT) hashp->alloc(sizeof(HASHBUCKET) * hashp->ssize);
1646 
1647  if (!segp)
1648  return NULL;
1649 
1650  MemSet(segp, 0, sizeof(HASHBUCKET) * hashp->ssize);
1651 
1652  return segp;
1653 }
1654 
1655 /*
1656  * allocate some new elements and link them into the indicated free list
1657  */
1658 static bool
1659 element_alloc(HTAB *hashp, int nelem, int freelist_idx)
1660 {
1661  HASHHDR *hctl = hashp->hctl;
1662  Size elementSize;
1663  HASHELEMENT *firstElement;
1664  HASHELEMENT *tmpElement;
1665  HASHELEMENT *prevElement;
1666  int i;
1667 
1668  if (hashp->isfixed)
1669  return false;
1670 
1671  /* Each element has a HASHELEMENT header plus user data. */
1672  elementSize = MAXALIGN(sizeof(HASHELEMENT)) + MAXALIGN(hctl->entrysize);
1673 
1674  CurrentDynaHashCxt = hashp->hcxt;
1675  firstElement = (HASHELEMENT *) hashp->alloc(nelem * elementSize);
1676 
1677  if (!firstElement)
1678  return false;
1679 
1680  /* prepare to link all the new entries into the freelist */
1681  prevElement = NULL;
1682  tmpElement = firstElement;
1683  for (i = 0; i < nelem; i++)
1684  {
1685  tmpElement->link = prevElement;
1686  prevElement = tmpElement;
1687  tmpElement = (HASHELEMENT *) (((char *) tmpElement) + elementSize);
1688  }
1689 
1690  /* if partitioned, must lock to touch freeList */
1691  if (IS_PARTITIONED(hctl))
1692  SpinLockAcquire(&hctl->freeList[freelist_idx].mutex);
1693 
1694  /* freelist could be nonempty if two backends did this concurrently */
1695  firstElement->link = hctl->freeList[freelist_idx].freeList;
1696  hctl->freeList[freelist_idx].freeList = prevElement;
1697 
1698  if (IS_PARTITIONED(hctl))
1699  SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1700 
1701  return true;
1702 }
1703 
1704 /* complain when we have detected a corrupted hashtable */
1705 static void
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  if (hashp->isshared)
1713  elog(PANIC, "hash table \"%s\" corrupted", hashp->tabname);
1714  else
1715  elog(FATAL, "hash table \"%s\" corrupted", hashp->tabname);
1716 }
1717 
1718 /* calculate ceil(log base 2) of num */
1719 int
1720 my_log2(long num)
1721 {
1722  /*
1723  * guard against too-large input, which would be invalid for
1724  * pg_ceil_log2_*()
1725  */
1726  if (num > LONG_MAX / 2)
1727  num = LONG_MAX / 2;
1728 
1729 #if SIZEOF_LONG < 8
1730  return pg_ceil_log2_32(num);
1731 #else
1732  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
1739 {
1740  /* my_log2's internal range check is sufficient */
1741  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 next_pow2_int(long num)
1747 {
1748  if (num > INT_MAX / 2)
1749  num = INT_MAX / 2;
1750  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
1792 {
1794  elog(ERROR, "too many active hash_seq_search scans, cannot start one on \"%s\"",
1795  hashp->tabname);
1796  seq_scan_tables[num_seq_scans] = hashp;
1798  num_seq_scans++;
1799 }
1800 
1801 /* Deregister an active scan */
1802 static void
1804 {
1805  int i;
1806 
1807  /* Search backward since it's most likely at the stack top */
1808  for (i = num_seq_scans - 1; i >= 0; i--)
1809  {
1810  if (seq_scan_tables[i] == hashp)
1811  {
1812  seq_scan_tables[i] = seq_scan_tables[num_seq_scans - 1];
1814  num_seq_scans--;
1815  return;
1816  }
1817  }
1818  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
1825 {
1826  int i;
1827 
1828  for (i = 0; i < num_seq_scans; i++)
1829  {
1830  if (seq_scan_tables[i] == hashp)
1831  return true;
1832  }
1833  return false;
1834 }
1835 
1836 /* Clean up any open scans at end of transaction */
1837 void
1838 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  if (isCommit)
1850  {
1851  int i;
1852 
1853  for (i = 0; i < num_seq_scans; i++)
1854  {
1855  elog(WARNING, "leaked hash_seq_search scan for hash table %p",
1856  seq_scan_tables[i]);
1857  }
1858  }
1859  num_seq_scans = 0;
1860 }
1861 
1862 /* Clean up any open scans at end of subtransaction */
1863 void
1864 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  for (i = num_seq_scans - 1; i >= 0; i--)
1874  {
1875  if (seq_scan_level[i] >= nestDepth)
1876  {
1877  if (isCommit)
1878  elog(WARNING, "leaked hash_seq_search scan for hash table %p",
1879  seq_scan_tables[i]);
1880  seq_scan_tables[i] = seq_scan_tables[num_seq_scans - 1];
1882  num_seq_scans--;
1883  }
1884  }
1885 }
void * hash_search_with_hash_value(HTAB *hashp, const void *keyPtr, uint32 hashvalue, HASHACTION action, bool *foundPtr)
Definition: dynahash.c:921
static int seq_scan_level[MAX_SEQ_SCANS]
Definition: dynahash.c:1785
int(* HashCompareFunc)(const void *key1, const void *key2, Size keysize)
Definition: hsearch.h:29
Size keysize
Definition: dynahash.c:181
int slock_t
Definition: s_lock.h:934
Size keysize
Definition: dynahash.c:227
long dsize
Definition: dynahash.c:174
uint32(* HashValueFunc)(const void *key, Size keysize)
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uint32 curBucket
Definition: hsearch.h:115
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Definition: dynahash.c:816
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Definition: mcxt.c:211
#define AllocSetContextCreate
Definition: memutils.h:170
#define HASH_CONTEXT
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#define HASH_ELEM
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uint32 max_bucket
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MemoryContext hcxt
Definition: hsearch.h:78
long ssize
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static long next_pow2_long(long num)
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HashCopyFunc keycopy
Definition: hsearch.h:76
Size entrysize
Definition: dynahash.c:182
static uint32 calc_bucket(HASHHDR *hctl, uint32 hash_val)
Definition: dynahash.c:869
#define IS_PARTITIONED(hctl)
Definition: dynahash.c:201
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Definition: hashfn.c:660
#define SpinLockInit(lock)
Definition: spin.h:60
#define NO_MAX_DSIZE
Definition: hsearch.h:100
#define ELEMENTKEY(helem)
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long num_partitions
Definition: dynahash.c:183
void AtEOSubXact_HashTables(bool isCommit, int nestDepth)
Definition: dynahash.c:1864
Size entrysize
Definition: hsearch.h:73
#define NUM_FREELISTS
Definition: dynahash.c:118
void hash_stats(const char *where, HTAB *hashp)
Definition: dynahash.c:835
#define ELEMENT_FROM_KEY(key)
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HashAllocFunc alloc
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#define MemSet(start, val, len)
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HASHELEMENT * curEntry
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Definition: dynahash.c:1337
slock_t mutex
Definition: dynahash.c:145
uint32 low_mask
Definition: dynahash.c:178
void * hash_search(HTAB *hashp, const void *keyPtr, HASHACTION action, bool *foundPtr)
Definition: dynahash.c:908
#define HASH_SHARED_MEM
Definition: hsearch.h:94
static int string_compare(const char *key1, const char *key2, Size keysize)
Definition: dynahash.c:295
static HASHBUCKET get_hash_entry(HTAB *hashp, int freelist_idx)
Definition: dynahash.c:1252
#define fprintf
Definition: port.h:197
long dsize
Definition: hsearch.h:69
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uint32 uint32_hash(const void *key, Size keysize)
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#define HASH_ATTACH
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Definition: pg_bitutils.h:202
long ffactor
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HashValueFunc hash
Definition: dynahash.c:214
#define SpinLockAcquire(lock)
Definition: spin.h:62
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uint32 get_hash_value(HTAB *hashp, const void *keyPtr)
Definition: dynahash.c:862
long max_dsize
Definition: hsearch.h:70
void pfree(void *pointer)
Definition: mcxt.c:1056
HASHBUCKET * HASHSEGMENT
Definition: dynahash.c:124
long ssize
Definition: dynahash.c:228
#define ERROR
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long num_partitions
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#define FATAL
Definition: elog.h:52
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Definition: pg_bitutils.h:189
int sshift
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#define ALLOCSET_DEFAULT_SIZES
Definition: memutils.h:192
#define DEF_SEGSIZE_SHIFT
Definition: dynahash.c:113
#define MOD(x, y)
Definition: dynahash.c:246
HashAllocFunc alloc
Definition: hsearch.h:77
#define HASH_KEYCOPY
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Definition: dynahash.c:572
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Definition: dynahash.c:212
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Definition: dynahash.c:1706
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Definition: dynahash.c:1824
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Definition: hsearch.h:58
unsigned int uint32
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HASHELEMENT * HASHBUCKET
Definition: dynahash.c:121
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Definition: hsearch.h:114
static bool init_htab(HTAB *hashp, long nelem)
Definition: dynahash.c:638
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Definition: dynahash.c:177
long nentries
Definition: dynahash.c:146
MemoryContext TopMemoryContext
Definition: mcxt.c:44
int my_log2(long num)
Definition: dynahash.c:1720
#define WARNING
Definition: elog.h:40
HashCompareFunc match
Definition: dynahash.c:215
Size hash_estimate_size(long num_entries, Size entrysize)
Definition: dynahash.c:734
static int next_pow2_int(long num)
Definition: dynahash.c:1746
bool isshared
Definition: dynahash.c:220
#define SpinLockRelease(lock)
Definition: spin.h:64
#define MAX_SEQ_SCANS
Definition: dynahash.c:1782
#define HASH_BLOBS
Definition: hsearch.h:88
bool frozen
Definition: dynahash.c:224
Size mul_size(Size s1, Size s2)
Definition: shmem.c:515
static int num_seq_scans
Definition: dynahash.c:1786
static HTAB * seq_scan_tables[MAX_SEQ_SCANS]
Definition: dynahash.c:1784
uint32 tag_hash(const void *key, Size keysize)
Definition: hashfn.c:677
HTAB * hash_create(const char *tabname, long nelem, HASHCTL *info, int flags)
Definition: dynahash.c:318
long ssize
Definition: dynahash.c:186
Size add_size(Size s1, Size s2)
Definition: shmem.c:498
FreeListData freeList[NUM_FREELISTS]
Definition: dynahash.c:170
static void deregister_seq_scan(HTAB *hashp)
Definition: dynahash.c:1803
Size keysize
Definition: hsearch.h:72
void *(* HashCopyFunc)(void *dest, const void *src, Size keysize)
Definition: hsearch.h:37
HashCompareFunc match
Definition: hsearch.h:75
MemoryContext hcxt
Definition: dynahash.c:218
#define ereport(elevel,...)
Definition: elog.h:144
long hash_select_dirsize(long num_entries)
Definition: dynahash.c:781
HashCopyFunc keycopy
Definition: dynahash.c:216
#define HASH_SEGMENT
Definition: hsearch.h:84
int GetCurrentTransactionNestLevel(void)
Definition: xact.c:842
size_t strlcpy(char *dst, const char *src, size_t siz)
Definition: strlcpy.c:45
#define MemoryContextIsValid(context)
Definition: memnodes.h:102
static void register_seq_scan(HTAB *hashp)
Definition: dynahash.c:1791
#define Assert(condition)
Definition: c.h:738
int nelem_alloc
Definition: dynahash.c:188
void *(* HashAllocFunc)(Size request)
Definition: hsearch.h:44
#define HASH_COMPARE
Definition: hsearch.h:90
size_t Size
Definition: c.h:466
void hash_freeze(HTAB *hashp)
Definition: dynahash.c:1487
static HASHSEGMENT seg_alloc(HTAB *hashp)
Definition: dynahash.c:1640
#define MAXALIGN(LEN)
Definition: c.h:691
void MemoryContextSetIdentifier(MemoryContext context, const char *id)
Definition: mcxt.c:329
Size hash_get_shared_size(HASHCTL *info, int flags)
Definition: dynahash.c:805
static bool expand_table(HTAB *hashp)
Definition: dynahash.c:1504
bool hash_update_hash_key(HTAB *hashp, void *existingEntry, const void *newKeyPtr)
Definition: dynahash.c:1117
HASHHDR * hctl
Definition: hsearch.h:79
void * hash_seq_search(HASH_SEQ_STATUS *status)
Definition: dynahash.c:1391
long ffactor
Definition: hsearch.h:71
void hash_seq_init(HASH_SEQ_STATUS *status, HTAB *hashp)
Definition: dynahash.c:1381
char * tabname
Definition: dynahash.c:219
#define HASH_FIXED_SIZE
Definition: hsearch.h:96
bool isfixed
Definition: dynahash.c:221
#define HASH_FFACTOR
Definition: hsearch.h:86
static void * DynaHashAlloc(Size size)
Definition: dynahash.c:280
#define HASH_DIRSIZE
Definition: hsearch.h:85
int errmsg(const char *fmt,...)
Definition: elog.c:824
void * MemoryContextAlloc(MemoryContext context, Size size)
Definition: mcxt.c:796
struct HASHELEMENT * link
Definition: hsearch.h:53
static int choose_nelem_alloc(Size entrysize)
Definition: dynahash.c:605
#define elog(elevel,...)
Definition: elog.h:214
static MemoryContext CurrentDynaHashCxt
Definition: dynahash.c:277
int i
#define HASH_ALLOC
Definition: hsearch.h:92
HASHELEMENT * freeList
Definition: dynahash.c:147
HASHSEGMENT * dir
Definition: dynahash.c:213
static bool element_alloc(HTAB *hashp, int nelem, int freelist_idx)
Definition: dynahash.c:1659
#define FREELIST_IDX(hctl, hashcode)
Definition: dynahash.c:203
void AtEOXact_HashTables(bool isCommit)
Definition: dynahash.c:1838
static void static void status(const char *fmt,...) pg_attribute_printf(1
Definition: pg_regress.c:225
int sshift
Definition: dynahash.c:187
static bool dir_realloc(HTAB *hashp)
Definition: dynahash.c:1601
#define DEF_FFACTOR
Definition: dynahash.c:115
#define DEF_SEGSIZE
Definition: dynahash.c:112
void hash_seq_term(HASH_SEQ_STATUS *status)
Definition: dynahash.c:1467
uint32 hashvalue
Definition: hsearch.h:54
HASHACTION
Definition: hsearch.h:103
HashValueFunc hash
Definition: hsearch.h:74
#define HASH_FUNCTION
Definition: hsearch.h:89
unsigned char bool
Definition: c.h:317
#define DEF_DIRSIZE
Definition: dynahash.c:114
long nsegs
Definition: dynahash.c:175