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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) 1996-2017, PostgreSQL Global Development Group
45  * Portions Copyright (c) 1994, Regents of the University of California
46  *
47  *
48  * IDENTIFICATION
49  * src/backend/utils/hash/dynahash.c
50  *
51  *-------------------------------------------------------------------------
52  */
53 
54 /*
55  * Original comments:
56  *
57  * Dynamic hashing, after CACM April 1988 pp 446-457, by Per-Ake Larson.
58  * Coded into C, with minor code improvements, and with hsearch(3) interface,
59  * by ejp@ausmelb.oz, Jul 26, 1988: 13:16;
60  * also, hcreate/hdestroy routines added to simulate hsearch(3).
61  *
62  * These routines simulate hsearch(3) and family, with the important
63  * difference that the hash table is dynamic - can grow indefinitely
64  * beyond its original size (as supplied to hcreate()).
65  *
66  * Performance appears to be comparable to that of hsearch(3).
67  * The 'source-code' options referred to in hsearch(3)'s 'man' page
68  * are not implemented; otherwise functionality is identical.
69  *
70  * Compilation controls:
71  * HASH_DEBUG controls some informative traces, mainly for debugging.
72  * HASH_STATISTICS causes HashAccesses and HashCollisions to be maintained;
73  * when combined with HASH_DEBUG, these are displayed by hdestroy().
74  *
75  * Problems & fixes to ejp@ausmelb.oz. WARNING: relies on pre-processor
76  * concatenation property, in probably unnecessary code 'optimization'.
77  *
78  * Modified margo@postgres.berkeley.edu February 1990
79  * added multiple table interface
80  * Modified by sullivan@postgres.berkeley.edu April 1990
81  * changed ctl structure for shared memory
82  */
83 
84 #include "postgres.h"
85 
86 #include <limits.h>
87 
88 #include "access/xact.h"
89 #include "storage/shmem.h"
90 #include "storage/spin.h"
91 #include "utils/dynahash.h"
92 #include "utils/memutils.h"
93 
94 
95 /*
96  * Constants
97  *
98  * A hash table has a top-level "directory", each of whose entries points
99  * to a "segment" of ssize bucket headers. The maximum number of hash
100  * buckets is thus dsize * ssize (but dsize may be expansible). Of course,
101  * the number of records in the table can be larger, but we don't want a
102  * whole lot of records per bucket or performance goes down.
103  *
104  * In a hash table allocated in shared memory, the directory cannot be
105  * expanded because it must stay at a fixed address. The directory size
106  * should be selected using hash_select_dirsize (and you'd better have
107  * a good idea of the maximum number of entries!). For non-shared hash
108  * tables, the initial directory size can be left at the default.
109  */
110 #define DEF_SEGSIZE 256
111 #define DEF_SEGSIZE_SHIFT 8 /* must be log2(DEF_SEGSIZE) */
112 #define DEF_DIRSIZE 256
113 #define DEF_FFACTOR 1 /* default fill factor */
114 
115 /* Number of freelists to be used for a partitioned hash table. */
116 #define NUM_FREELISTS 32
117 
118 /* A hash bucket is a linked list of HASHELEMENTs */
120 
121 /* A hash segment is an array of bucket headers */
123 
124 /*
125  * Per-freelist data.
126  *
127  * In a partitioned hash table, each freelist is associated with a specific
128  * set of hashcodes, as determined by the FREELIST_IDX() macro below.
129  * nentries tracks the number of live hashtable entries having those hashcodes
130  * (NOT the number of entries in the freelist, as you might expect).
131  *
132  * The coverage of a freelist might be more or less than one partition, so it
133  * needs its own lock rather than relying on caller locking. Relying on that
134  * wouldn't work even if the coverage was the same, because of the occasional
135  * need to "borrow" entries from another freelist; see get_hash_entry().
136  *
137  * Using an array of FreeListData instead of separate arrays of mutexes,
138  * nentries and freeLists helps to reduce sharing of cache lines between
139  * different mutexes.
140  */
141 typedef struct
142 {
143  slock_t mutex; /* spinlock for this freelist */
144  long nentries; /* number of entries in associated buckets */
145  HASHELEMENT *freeList; /* chain of free elements */
146 } FreeListData;
147 
148 /*
149  * Header structure for a hash table --- contains all changeable info
150  *
151  * In a shared-memory hash table, the HASHHDR is in shared memory, while
152  * each backend has a local HTAB struct. For a non-shared table, there isn't
153  * any functional difference between HASHHDR and HTAB, but we separate them
154  * anyway to share code between shared and non-shared tables.
155  */
156 struct HASHHDR
157 {
158  /*
159  * The freelist can become a point of contention in high-concurrency hash
160  * tables, so we use an array of freelists, each with its own mutex and
161  * nentries count, instead of just a single one. Although the freelists
162  * normally operate independently, we will scavenge entries from freelists
163  * other than a hashcode's default freelist when necessary.
164  *
165  * If the hash table is not partitioned, only freeList[0] is used and its
166  * spinlock is not used at all; callers' locking is assumed sufficient.
167  */
169 
170  /* These fields can change, but not in a partitioned table */
171  /* Also, dsize can't change in a shared table, even if unpartitioned */
172  long dsize; /* directory size */
173  long nsegs; /* number of allocated segments (<= dsize) */
174  uint32 max_bucket; /* ID of maximum bucket in use */
175  uint32 high_mask; /* mask to modulo into entire table */
176  uint32 low_mask; /* mask to modulo into lower half of table */
177 
178  /* These fields are fixed at hashtable creation */
179  Size keysize; /* hash key length in bytes */
180  Size entrysize; /* total user element size in bytes */
181  long num_partitions; /* # partitions (must be power of 2), or 0 */
182  long ffactor; /* target fill factor */
183  long max_dsize; /* 'dsize' limit if directory is fixed size */
184  long ssize; /* segment size --- must be power of 2 */
185  int sshift; /* segment shift = log2(ssize) */
186  int nelem_alloc; /* number of entries to allocate at once */
187 
188 #ifdef HASH_STATISTICS
189 
190  /*
191  * Count statistics here. NB: stats code doesn't bother with mutex, so
192  * counts could be corrupted a bit in a partitioned table.
193  */
194  long accesses;
195  long collisions;
196 #endif
197 };
198 
199 #define IS_PARTITIONED(hctl) ((hctl)->num_partitions != 0)
200 
201 #define FREELIST_IDX(hctl, hashcode) \
202  (IS_PARTITIONED(hctl) ? (hashcode) % NUM_FREELISTS : 0)
203 
204 /*
205  * Top control structure for a hashtable --- in a shared table, each backend
206  * has its own copy (OK since no fields change at runtime)
207  */
208 struct HTAB
209 {
210  HASHHDR *hctl; /* => shared control information */
211  HASHSEGMENT *dir; /* directory of segment starts */
212  HashValueFunc hash; /* hash function */
213  HashCompareFunc match; /* key comparison function */
214  HashCopyFunc keycopy; /* key copying function */
215  HashAllocFunc alloc; /* memory allocator */
216  MemoryContext hcxt; /* memory context if default allocator used */
217  char *tabname; /* table name (for error messages) */
218  bool isshared; /* true if table is in shared memory */
219  bool isfixed; /* if true, don't enlarge */
220 
221  /* freezing a shared table isn't allowed, so we can keep state here */
222  bool frozen; /* true = no more inserts allowed */
223 
224  /* We keep local copies of these fixed values to reduce contention */
225  Size keysize; /* hash key length in bytes */
226  long ssize; /* segment size --- must be power of 2 */
227  int sshift; /* segment shift = log2(ssize) */
228 };
229 
230 /*
231  * Key (also entry) part of a HASHELEMENT
232  */
233 #define ELEMENTKEY(helem) (((char *)(helem)) + MAXALIGN(sizeof(HASHELEMENT)))
234 
235 /*
236  * Obtain element pointer given pointer to key
237  */
238 #define ELEMENT_FROM_KEY(key) \
239  ((HASHELEMENT *) (((char *) (key)) - MAXALIGN(sizeof(HASHELEMENT))))
240 
241 /*
242  * Fast MOD arithmetic, assuming that y is a power of 2 !
243  */
244 #define MOD(x,y) ((x) & ((y)-1))
245 
246 #if HASH_STATISTICS
247 static long hash_accesses,
248  hash_collisions,
249  hash_expansions;
250 #endif
251 
252 /*
253  * Private function prototypes
254  */
255 static void *DynaHashAlloc(Size size);
256 static HASHSEGMENT seg_alloc(HTAB *hashp);
257 static bool element_alloc(HTAB *hashp, int nelem, int freelist_idx);
258 static bool dir_realloc(HTAB *hashp);
259 static bool expand_table(HTAB *hashp);
260 static HASHBUCKET get_hash_entry(HTAB *hashp, int freelist_idx);
261 static void hdefault(HTAB *hashp);
262 static int choose_nelem_alloc(Size entrysize);
263 static bool init_htab(HTAB *hashp, long nelem);
264 static void hash_corrupted(HTAB *hashp);
265 static long next_pow2_long(long num);
266 static int next_pow2_int(long num);
267 static void register_seq_scan(HTAB *hashp);
268 static void deregister_seq_scan(HTAB *hashp);
269 static bool has_seq_scans(HTAB *hashp);
270 
271 
272 /*
273  * memory allocation support
274  */
276 
277 static void *
279 {
280  Assert(MemoryContextIsValid(CurrentDynaHashCxt));
281  return MemoryContextAlloc(CurrentDynaHashCxt, size);
282 }
283 
284 
285 /*
286  * HashCompareFunc for string keys
287  *
288  * Because we copy keys with strlcpy(), they will be truncated at keysize-1
289  * bytes, so we can only compare that many ... hence strncmp is almost but
290  * not quite the right thing.
291  */
292 static int
293 string_compare(const char *key1, const char *key2, Size keysize)
294 {
295  return strncmp(key1, key2, keysize - 1);
296 }
297 
298 
299 /************************** CREATE ROUTINES **********************/
300 
301 /*
302  * hash_create -- create a new dynamic hash table
303  *
304  * tabname: a name for the table (for debugging purposes)
305  * nelem: maximum number of elements expected
306  * *info: additional table parameters, as indicated by flags
307  * flags: bitmask indicating which parameters to take from *info
308  *
309  * Note: for a shared-memory hashtable, nelem needs to be a pretty good
310  * estimate, since we can't expand the table on the fly. But an unshared
311  * hashtable can be expanded on-the-fly, so it's better for nelem to be
312  * on the small side and let the table grow if it's exceeded. An overly
313  * large nelem will penalize hash_seq_search speed without buying much.
314  */
315 HTAB *
316 hash_create(const char *tabname, long nelem, HASHCTL *info, int flags)
317 {
318  HTAB *hashp;
319  HASHHDR *hctl;
320 
321  /*
322  * For shared hash tables, we have a local hash header (HTAB struct) that
323  * we allocate in TopMemoryContext; all else is in shared memory.
324  *
325  * For non-shared hash tables, everything including the hash header is in
326  * a memory context created specially for the hash table --- this makes
327  * hash_destroy very simple. The memory context is made a child of either
328  * a context specified by the caller, or TopMemoryContext if nothing is
329  * specified.
330  */
331  if (flags & HASH_SHARED_MEM)
332  {
333  /* Set up to allocate the hash header */
334  CurrentDynaHashCxt = TopMemoryContext;
335  }
336  else
337  {
338  /* Create the hash table's private memory context */
339  if (flags & HASH_CONTEXT)
340  CurrentDynaHashCxt = info->hcxt;
341  else
342  CurrentDynaHashCxt = TopMemoryContext;
343  CurrentDynaHashCxt = AllocSetContextCreate(CurrentDynaHashCxt,
344  tabname,
346  }
347 
348  /* Initialize the hash header, plus a copy of the table name */
349  hashp = (HTAB *) DynaHashAlloc(sizeof(HTAB) + strlen(tabname) + 1);
350  MemSet(hashp, 0, sizeof(HTAB));
351 
352  hashp->tabname = (char *) (hashp + 1);
353  strcpy(hashp->tabname, tabname);
354 
355  /*
356  * Select the appropriate hash function (see comments at head of file).
357  */
358  if (flags & HASH_FUNCTION)
359  hashp->hash = info->hash;
360  else if (flags & HASH_BLOBS)
361  {
362  /* We can optimize hashing for common key sizes */
363  Assert(flags & HASH_ELEM);
364  if (info->keysize == sizeof(uint32))
365  hashp->hash = uint32_hash;
366  else
367  hashp->hash = tag_hash;
368  }
369  else
370  hashp->hash = string_hash; /* default hash function */
371 
372  /*
373  * If you don't specify a match function, it defaults to string_compare if
374  * you used string_hash (either explicitly or by default) and to memcmp
375  * otherwise.
376  *
377  * Note: explicitly specifying string_hash is deprecated, because this
378  * might not work for callers in loadable modules on some platforms due to
379  * referencing a trampoline instead of the string_hash function proper.
380  * Just let it default, eh?
381  */
382  if (flags & HASH_COMPARE)
383  hashp->match = info->match;
384  else if (hashp->hash == string_hash)
386  else
387  hashp->match = memcmp;
388 
389  /*
390  * Similarly, the key-copying function defaults to strlcpy or memcpy.
391  */
392  if (flags & HASH_KEYCOPY)
393  hashp->keycopy = info->keycopy;
394  else if (hashp->hash == string_hash)
395  hashp->keycopy = (HashCopyFunc) strlcpy;
396  else
397  hashp->keycopy = memcpy;
398 
399  /* And select the entry allocation function, too. */
400  if (flags & HASH_ALLOC)
401  hashp->alloc = info->alloc;
402  else
403  hashp->alloc = DynaHashAlloc;
404 
405  if (flags & HASH_SHARED_MEM)
406  {
407  /*
408  * ctl structure and directory are preallocated for shared memory
409  * tables. Note that HASH_DIRSIZE and HASH_ALLOC had better be set as
410  * well.
411  */
412  hashp->hctl = info->hctl;
413  hashp->dir = (HASHSEGMENT *) (((char *) info->hctl) + sizeof(HASHHDR));
414  hashp->hcxt = NULL;
415  hashp->isshared = true;
416 
417  /* hash table already exists, we're just attaching to it */
418  if (flags & HASH_ATTACH)
419  {
420  /* make local copies of some heavily-used values */
421  hctl = hashp->hctl;
422  hashp->keysize = hctl->keysize;
423  hashp->ssize = hctl->ssize;
424  hashp->sshift = hctl->sshift;
425 
426  return hashp;
427  }
428  }
429  else
430  {
431  /* setup hash table defaults */
432  hashp->hctl = NULL;
433  hashp->dir = NULL;
434  hashp->hcxt = CurrentDynaHashCxt;
435  hashp->isshared = false;
436  }
437 
438  if (!hashp->hctl)
439  {
440  hashp->hctl = (HASHHDR *) hashp->alloc(sizeof(HASHHDR));
441  if (!hashp->hctl)
442  ereport(ERROR,
443  (errcode(ERRCODE_OUT_OF_MEMORY),
444  errmsg("out of memory")));
445  }
446 
447  hashp->frozen = false;
448 
449  hdefault(hashp);
450 
451  hctl = hashp->hctl;
452 
453  if (flags & HASH_PARTITION)
454  {
455  /* Doesn't make sense to partition a local hash table */
456  Assert(flags & HASH_SHARED_MEM);
457 
458  /*
459  * The number of partitions had better be a power of 2. Also, it must
460  * be less than INT_MAX (see init_htab()), so call the int version of
461  * next_pow2.
462  */
464 
465  hctl->num_partitions = info->num_partitions;
466  }
467 
468  if (flags & HASH_SEGMENT)
469  {
470  hctl->ssize = info->ssize;
471  hctl->sshift = my_log2(info->ssize);
472  /* ssize had better be a power of 2 */
473  Assert(hctl->ssize == (1L << hctl->sshift));
474  }
475  if (flags & HASH_FFACTOR)
476  hctl->ffactor = info->ffactor;
477 
478  /*
479  * SHM hash tables have fixed directory size passed by the caller.
480  */
481  if (flags & HASH_DIRSIZE)
482  {
483  hctl->max_dsize = info->max_dsize;
484  hctl->dsize = info->dsize;
485  }
486 
487  /*
488  * hash table now allocates space for key and data but you have to say how
489  * much space to allocate
490  */
491  if (flags & HASH_ELEM)
492  {
493  Assert(info->entrysize >= info->keysize);
494  hctl->keysize = info->keysize;
495  hctl->entrysize = info->entrysize;
496  }
497 
498  /* make local copies of heavily-used constant fields */
499  hashp->keysize = hctl->keysize;
500  hashp->ssize = hctl->ssize;
501  hashp->sshift = hctl->sshift;
502 
503  /* Build the hash directory structure */
504  if (!init_htab(hashp, nelem))
505  elog(ERROR, "failed to initialize hash table \"%s\"", hashp->tabname);
506 
507  /*
508  * For a shared hash table, preallocate the requested number of elements.
509  * This reduces problems with run-time out-of-shared-memory conditions.
510  *
511  * For a non-shared hash table, preallocate the requested number of
512  * elements if it's less than our chosen nelem_alloc. This avoids wasting
513  * space if the caller correctly estimates a small table size.
514  */
515  if ((flags & HASH_SHARED_MEM) ||
516  nelem < hctl->nelem_alloc)
517  {
518  int i,
519  freelist_partitions,
520  nelem_alloc,
521  nelem_alloc_first;
522 
523  /*
524  * If hash table is partitioned, give each freelist an equal share of
525  * the initial allocation. Otherwise only freeList[0] is used.
526  */
527  if (IS_PARTITIONED(hashp->hctl))
528  freelist_partitions = NUM_FREELISTS;
529  else
530  freelist_partitions = 1;
531 
532  nelem_alloc = nelem / freelist_partitions;
533  if (nelem_alloc <= 0)
534  nelem_alloc = 1;
535 
536  /*
537  * Make sure we'll allocate all the requested elements; freeList[0]
538  * gets the excess if the request isn't divisible by NUM_FREELISTS.
539  */
540  if (nelem_alloc * freelist_partitions < nelem)
541  nelem_alloc_first =
542  nelem - nelem_alloc * (freelist_partitions - 1);
543  else
544  nelem_alloc_first = nelem_alloc;
545 
546  for (i = 0; i < freelist_partitions; i++)
547  {
548  int temp = (i == 0) ? nelem_alloc_first : nelem_alloc;
549 
550  if (!element_alloc(hashp, temp, i))
551  ereport(ERROR,
552  (errcode(ERRCODE_OUT_OF_MEMORY),
553  errmsg("out of memory")));
554  }
555  }
556 
557  if (flags & HASH_FIXED_SIZE)
558  hashp->isfixed = true;
559  return hashp;
560 }
561 
562 /*
563  * Set default HASHHDR parameters.
564  */
565 static void
566 hdefault(HTAB *hashp)
567 {
568  HASHHDR *hctl = hashp->hctl;
569 
570  MemSet(hctl, 0, sizeof(HASHHDR));
571 
572  hctl->dsize = DEF_DIRSIZE;
573  hctl->nsegs = 0;
574 
575  /* rather pointless defaults for key & entry size */
576  hctl->keysize = sizeof(char *);
577  hctl->entrysize = 2 * sizeof(char *);
578 
579  hctl->num_partitions = 0; /* not partitioned */
580 
581  hctl->ffactor = DEF_FFACTOR;
582 
583  /* table has no fixed maximum size */
584  hctl->max_dsize = NO_MAX_DSIZE;
585 
586  hctl->ssize = DEF_SEGSIZE;
587  hctl->sshift = DEF_SEGSIZE_SHIFT;
588 
589 #ifdef HASH_STATISTICS
590  hctl->accesses = hctl->collisions = 0;
591 #endif
592 }
593 
594 /*
595  * Given the user-specified entry size, choose nelem_alloc, ie, how many
596  * elements to add to the hash table when we need more.
597  */
598 static int
600 {
601  int nelem_alloc;
602  Size elementSize;
603  Size allocSize;
604 
605  /* Each element has a HASHELEMENT header plus user data. */
606  /* NB: this had better match element_alloc() */
607  elementSize = MAXALIGN(sizeof(HASHELEMENT)) + MAXALIGN(entrysize);
608 
609  /*
610  * The idea here is to choose nelem_alloc at least 32, but round up so
611  * that the allocation request will be a power of 2 or just less. This
612  * makes little difference for hash tables in shared memory, but for hash
613  * tables managed by palloc, the allocation request will be rounded up to
614  * a power of 2 anyway. If we fail to take this into account, we'll waste
615  * as much as half the allocated space.
616  */
617  allocSize = 32 * 4; /* assume elementSize at least 8 */
618  do
619  {
620  allocSize <<= 1;
621  nelem_alloc = allocSize / elementSize;
622  } while (nelem_alloc < 32);
623 
624  return nelem_alloc;
625 }
626 
627 /*
628  * Compute derived fields of hctl and build the initial directory/segment
629  * arrays
630  */
631 static bool
632 init_htab(HTAB *hashp, long nelem)
633 {
634  HASHHDR *hctl = hashp->hctl;
635  HASHSEGMENT *segp;
636  int nbuckets;
637  int nsegs;
638  int i;
639 
640  /*
641  * initialize mutexes if it's a partitioned table
642  */
643  if (IS_PARTITIONED(hctl))
644  for (i = 0; i < NUM_FREELISTS; i++)
645  SpinLockInit(&(hctl->freeList[i].mutex));
646 
647  /*
648  * Divide number of elements by the fill factor to determine a desired
649  * number of buckets. Allocate space for the next greater power of two
650  * number of buckets
651  */
652  nbuckets = next_pow2_int((nelem - 1) / hctl->ffactor + 1);
653 
654  /*
655  * In a partitioned table, nbuckets must be at least equal to
656  * num_partitions; were it less, keys with apparently different partition
657  * numbers would map to the same bucket, breaking partition independence.
658  * (Normally nbuckets will be much bigger; this is just a safety check.)
659  */
660  while (nbuckets < hctl->num_partitions)
661  nbuckets <<= 1;
662 
663  hctl->max_bucket = hctl->low_mask = nbuckets - 1;
664  hctl->high_mask = (nbuckets << 1) - 1;
665 
666  /*
667  * Figure number of directory segments needed, round up to a power of 2
668  */
669  nsegs = (nbuckets - 1) / hctl->ssize + 1;
670  nsegs = next_pow2_int(nsegs);
671 
672  /*
673  * Make sure directory is big enough. If pre-allocated directory is too
674  * small, choke (caller screwed up).
675  */
676  if (nsegs > hctl->dsize)
677  {
678  if (!(hashp->dir))
679  hctl->dsize = nsegs;
680  else
681  return false;
682  }
683 
684  /* Allocate a directory */
685  if (!(hashp->dir))
686  {
687  CurrentDynaHashCxt = hashp->hcxt;
688  hashp->dir = (HASHSEGMENT *)
689  hashp->alloc(hctl->dsize * sizeof(HASHSEGMENT));
690  if (!hashp->dir)
691  return false;
692  }
693 
694  /* Allocate initial segments */
695  for (segp = hashp->dir; hctl->nsegs < nsegs; hctl->nsegs++, segp++)
696  {
697  *segp = seg_alloc(hashp);
698  if (*segp == NULL)
699  return false;
700  }
701 
702  /* Choose number of entries to allocate at a time */
704 
705 #if HASH_DEBUG
706  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",
707  "TABLE POINTER ", hashp,
708  "DIRECTORY SIZE ", hctl->dsize,
709  "SEGMENT SIZE ", hctl->ssize,
710  "SEGMENT SHIFT ", hctl->sshift,
711  "FILL FACTOR ", hctl->ffactor,
712  "MAX BUCKET ", hctl->max_bucket,
713  "HIGH MASK ", hctl->high_mask,
714  "LOW MASK ", hctl->low_mask,
715  "NSEGS ", hctl->nsegs);
716 #endif
717  return true;
718 }
719 
720 /*
721  * Estimate the space needed for a hashtable containing the given number
722  * of entries of given size.
723  * NOTE: this is used to estimate the footprint of hashtables in shared
724  * memory; therefore it does not count HTAB which is in local memory.
725  * NB: assumes that all hash structure parameters have default values!
726  */
727 Size
729 {
730  Size size;
731  long nBuckets,
732  nSegments,
733  nDirEntries,
734  nElementAllocs,
735  elementSize,
736  elementAllocCnt;
737 
738  /* estimate number of buckets wanted */
739  nBuckets = next_pow2_long((num_entries - 1) / DEF_FFACTOR + 1);
740  /* # of segments needed for nBuckets */
741  nSegments = next_pow2_long((nBuckets - 1) / DEF_SEGSIZE + 1);
742  /* directory entries */
743  nDirEntries = DEF_DIRSIZE;
744  while (nDirEntries < nSegments)
745  nDirEntries <<= 1; /* dir_alloc doubles dsize at each call */
746 
747  /* fixed control info */
748  size = MAXALIGN(sizeof(HASHHDR)); /* but not HTAB, per above */
749  /* directory */
750  size = add_size(size, mul_size(nDirEntries, sizeof(HASHSEGMENT)));
751  /* segments */
752  size = add_size(size, mul_size(nSegments,
753  MAXALIGN(DEF_SEGSIZE * sizeof(HASHBUCKET))));
754  /* elements --- allocated in groups of choose_nelem_alloc() entries */
755  elementAllocCnt = choose_nelem_alloc(entrysize);
756  nElementAllocs = (num_entries - 1) / elementAllocCnt + 1;
757  elementSize = MAXALIGN(sizeof(HASHELEMENT)) + MAXALIGN(entrysize);
758  size = add_size(size,
759  mul_size(nElementAllocs,
760  mul_size(elementAllocCnt, elementSize)));
761 
762  return size;
763 }
764 
765 /*
766  * Select an appropriate directory size for a hashtable with the given
767  * maximum number of entries.
768  * This is only needed for hashtables in shared memory, whose directories
769  * cannot be expanded dynamically.
770  * NB: assumes that all hash structure parameters have default values!
771  *
772  * XXX this had better agree with the behavior of init_htab()...
773  */
774 long
775 hash_select_dirsize(long num_entries)
776 {
777  long nBuckets,
778  nSegments,
779  nDirEntries;
780 
781  /* estimate number of buckets wanted */
782  nBuckets = next_pow2_long((num_entries - 1) / DEF_FFACTOR + 1);
783  /* # of segments needed for nBuckets */
784  nSegments = next_pow2_long((nBuckets - 1) / DEF_SEGSIZE + 1);
785  /* directory entries */
786  nDirEntries = DEF_DIRSIZE;
787  while (nDirEntries < nSegments)
788  nDirEntries <<= 1; /* dir_alloc doubles dsize at each call */
789 
790  return nDirEntries;
791 }
792 
793 /*
794  * Compute the required initial memory allocation for a shared-memory
795  * hashtable with the given parameters. We need space for the HASHHDR
796  * and for the (non expansible) directory.
797  */
798 Size
799 hash_get_shared_size(HASHCTL *info, int flags)
800 {
801  Assert(flags & HASH_DIRSIZE);
802  Assert(info->dsize == info->max_dsize);
803  return sizeof(HASHHDR) + info->dsize * sizeof(HASHSEGMENT);
804 }
805 
806 
807 /********************** DESTROY ROUTINES ************************/
808 
809 void
811 {
812  if (hashp != NULL)
813  {
814  /* allocation method must be one we know how to free, too */
815  Assert(hashp->alloc == DynaHashAlloc);
816  /* so this hashtable must have it's own context */
817  Assert(hashp->hcxt != NULL);
818 
819  hash_stats("destroy", hashp);
820 
821  /*
822  * Free everything by destroying the hash table's memory context.
823  */
824  MemoryContextDelete(hashp->hcxt);
825  }
826 }
827 
828 void
829 hash_stats(const char *where, HTAB *hashp)
830 {
831 #if HASH_STATISTICS
832  fprintf(stderr, "%s: this HTAB -- accesses %ld collisions %ld\n",
833  where, hashp->hctl->accesses, hashp->hctl->collisions);
834 
835  fprintf(stderr, "hash_stats: entries %ld keysize %ld maxp %u segmentcount %ld\n",
836  hash_get_num_entries(hashp), (long) hashp->hctl->keysize,
837  hashp->hctl->max_bucket, hashp->hctl->nsegs);
838  fprintf(stderr, "%s: total accesses %ld total collisions %ld\n",
839  where, hash_accesses, hash_collisions);
840  fprintf(stderr, "hash_stats: total expansions %ld\n",
841  hash_expansions);
842 #endif
843 }
844 
845 /*******************************SEARCH ROUTINES *****************************/
846 
847 
848 /*
849  * get_hash_value -- exported routine to calculate a key's hash value
850  *
851  * We export this because for partitioned tables, callers need to compute
852  * the partition number (from the low-order bits of the hash value) before
853  * searching.
854  */
855 uint32
856 get_hash_value(HTAB *hashp, const void *keyPtr)
857 {
858  return hashp->hash(keyPtr, hashp->keysize);
859 }
860 
861 /* Convert a hash value to a bucket number */
862 static inline uint32
863 calc_bucket(HASHHDR *hctl, uint32 hash_val)
864 {
865  uint32 bucket;
866 
867  bucket = hash_val & hctl->high_mask;
868  if (bucket > hctl->max_bucket)
869  bucket = bucket & hctl->low_mask;
870 
871  return bucket;
872 }
873 
874 /*
875  * hash_search -- look up key in table and perform action
876  * hash_search_with_hash_value -- same, with key's hash value already computed
877  *
878  * action is one of:
879  * HASH_FIND: look up key in table
880  * HASH_ENTER: look up key in table, creating entry if not present
881  * HASH_ENTER_NULL: same, but return NULL if out of memory
882  * HASH_REMOVE: look up key in table, remove entry if present
883  *
884  * Return value is a pointer to the element found/entered/removed if any,
885  * or NULL if no match was found. (NB: in the case of the REMOVE action,
886  * the result is a dangling pointer that shouldn't be dereferenced!)
887  *
888  * HASH_ENTER will normally ereport a generic "out of memory" error if
889  * it is unable to create a new entry. The HASH_ENTER_NULL operation is
890  * the same except it will return NULL if out of memory. Note that
891  * HASH_ENTER_NULL cannot be used with the default palloc-based allocator,
892  * since palloc internally ereports on out-of-memory.
893  *
894  * If foundPtr isn't NULL, then *foundPtr is set true if we found an
895  * existing entry in the table, false otherwise. This is needed in the
896  * HASH_ENTER case, but is redundant with the return value otherwise.
897  *
898  * For hash_search_with_hash_value, the hashvalue parameter must have been
899  * calculated with get_hash_value().
900  */
901 void *
903  const void *keyPtr,
905  bool *foundPtr)
906 {
907  return hash_search_with_hash_value(hashp,
908  keyPtr,
909  hashp->hash(keyPtr, hashp->keysize),
910  action,
911  foundPtr);
912 }
913 
914 void *
916  const void *keyPtr,
917  uint32 hashvalue,
919  bool *foundPtr)
920 {
921  HASHHDR *hctl = hashp->hctl;
922  int freelist_idx = FREELIST_IDX(hctl, hashvalue);
923  Size keysize;
924  uint32 bucket;
925  long segment_num;
926  long segment_ndx;
927  HASHSEGMENT segp;
928  HASHBUCKET currBucket;
929  HASHBUCKET *prevBucketPtr;
930  HashCompareFunc match;
931 
932 #if HASH_STATISTICS
933  hash_accesses++;
934  hctl->accesses++;
935 #endif
936 
937  /*
938  * If inserting, check if it is time to split a bucket.
939  *
940  * NOTE: failure to expand table is not a fatal error, it just means we
941  * have to run at higher fill factor than we wanted. However, if we're
942  * using the palloc allocator then it will throw error anyway on
943  * out-of-memory, so we must do this before modifying the table.
944  */
945  if (action == HASH_ENTER || action == HASH_ENTER_NULL)
946  {
947  /*
948  * Can't split if running in partitioned mode, nor if frozen, nor if
949  * table is the subject of any active hash_seq_search scans. Strange
950  * order of these tests is to try to check cheaper conditions first.
951  */
952  if (!IS_PARTITIONED(hctl) && !hashp->frozen &&
953  hctl->freeList[0].nentries / (long) (hctl->max_bucket + 1) >= hctl->ffactor &&
954  !has_seq_scans(hashp))
955  (void) expand_table(hashp);
956  }
957 
958  /*
959  * Do the initial lookup
960  */
961  bucket = calc_bucket(hctl, hashvalue);
962 
963  segment_num = bucket >> hashp->sshift;
964  segment_ndx = MOD(bucket, hashp->ssize);
965 
966  segp = hashp->dir[segment_num];
967 
968  if (segp == NULL)
969  hash_corrupted(hashp);
970 
971  prevBucketPtr = &segp[segment_ndx];
972  currBucket = *prevBucketPtr;
973 
974  /*
975  * Follow collision chain looking for matching key
976  */
977  match = hashp->match; /* save one fetch in inner loop */
978  keysize = hashp->keysize; /* ditto */
979 
980  while (currBucket != NULL)
981  {
982  if (currBucket->hashvalue == hashvalue &&
983  match(ELEMENTKEY(currBucket), keyPtr, keysize) == 0)
984  break;
985  prevBucketPtr = &(currBucket->link);
986  currBucket = *prevBucketPtr;
987 #if HASH_STATISTICS
988  hash_collisions++;
989  hctl->collisions++;
990 #endif
991  }
992 
993  if (foundPtr)
994  *foundPtr = (bool) (currBucket != NULL);
995 
996  /*
997  * OK, now what?
998  */
999  switch (action)
1000  {
1001  case HASH_FIND:
1002  if (currBucket != NULL)
1003  return (void *) ELEMENTKEY(currBucket);
1004  return NULL;
1005 
1006  case HASH_REMOVE:
1007  if (currBucket != NULL)
1008  {
1009  /* if partitioned, must lock to touch nentries and freeList */
1010  if (IS_PARTITIONED(hctl))
1011  SpinLockAcquire(&(hctl->freeList[freelist_idx].mutex));
1012 
1013  /* delete the record from the appropriate nentries counter. */
1014  Assert(hctl->freeList[freelist_idx].nentries > 0);
1015  hctl->freeList[freelist_idx].nentries--;
1016 
1017  /* remove record from hash bucket's chain. */
1018  *prevBucketPtr = currBucket->link;
1019 
1020  /* add the record to the appropriate freelist. */
1021  currBucket->link = hctl->freeList[freelist_idx].freeList;
1022  hctl->freeList[freelist_idx].freeList = currBucket;
1023 
1024  if (IS_PARTITIONED(hctl))
1025  SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1026 
1027  /*
1028  * better hope the caller is synchronizing access to this
1029  * element, because someone else is going to reuse it the next
1030  * time something is added to the table
1031  */
1032  return (void *) ELEMENTKEY(currBucket);
1033  }
1034  return NULL;
1035 
1036  case HASH_ENTER_NULL:
1037  /* ENTER_NULL does not work with palloc-based allocator */
1038  Assert(hashp->alloc != DynaHashAlloc);
1039  /* FALL THRU */
1040 
1041  case HASH_ENTER:
1042  /* Return existing element if found, else create one */
1043  if (currBucket != NULL)
1044  return (void *) ELEMENTKEY(currBucket);
1045 
1046  /* disallow inserts if frozen */
1047  if (hashp->frozen)
1048  elog(ERROR, "cannot insert into frozen hashtable \"%s\"",
1049  hashp->tabname);
1050 
1051  currBucket = get_hash_entry(hashp, freelist_idx);
1052  if (currBucket == NULL)
1053  {
1054  /* out of memory */
1055  if (action == HASH_ENTER_NULL)
1056  return NULL;
1057  /* report a generic message */
1058  if (hashp->isshared)
1059  ereport(ERROR,
1060  (errcode(ERRCODE_OUT_OF_MEMORY),
1061  errmsg("out of shared memory")));
1062  else
1063  ereport(ERROR,
1064  (errcode(ERRCODE_OUT_OF_MEMORY),
1065  errmsg("out of memory")));
1066  }
1067 
1068  /* link into hashbucket chain */
1069  *prevBucketPtr = currBucket;
1070  currBucket->link = NULL;
1071 
1072  /* copy key into record */
1073  currBucket->hashvalue = hashvalue;
1074  hashp->keycopy(ELEMENTKEY(currBucket), keyPtr, keysize);
1075 
1076  /*
1077  * Caller is expected to fill the data field on return. DO NOT
1078  * insert any code that could possibly throw error here, as doing
1079  * so would leave the table entry incomplete and hence corrupt the
1080  * caller's data structure.
1081  */
1082 
1083  return (void *) ELEMENTKEY(currBucket);
1084  }
1085 
1086  elog(ERROR, "unrecognized hash action code: %d", (int) action);
1087 
1088  return NULL; /* keep compiler quiet */
1089 }
1090 
1091 /*
1092  * hash_update_hash_key -- change the hash key of an existing table entry
1093  *
1094  * This is equivalent to removing the entry, making a new entry, and copying
1095  * over its data, except that the entry never goes to the table's freelist.
1096  * Therefore this cannot suffer an out-of-memory failure, even if there are
1097  * other processes operating in other partitions of the hashtable.
1098  *
1099  * Returns true if successful, false if the requested new hash key is already
1100  * present. Throws error if the specified entry pointer isn't actually a
1101  * table member.
1102  *
1103  * NB: currently, there is no special case for old and new hash keys being
1104  * identical, which means we'll report false for that situation. This is
1105  * preferable for existing uses.
1106  *
1107  * NB: for a partitioned hashtable, caller must hold lock on both relevant
1108  * partitions, if the new hash key would belong to a different partition.
1109  */
1110 bool
1112  void *existingEntry,
1113  const void *newKeyPtr)
1114 {
1115  HASHELEMENT *existingElement = ELEMENT_FROM_KEY(existingEntry);
1116  HASHHDR *hctl = hashp->hctl;
1117  uint32 newhashvalue;
1118  Size keysize;
1119  uint32 bucket;
1120  uint32 newbucket;
1121  long segment_num;
1122  long segment_ndx;
1123  HASHSEGMENT segp;
1124  HASHBUCKET currBucket;
1125  HASHBUCKET *prevBucketPtr;
1126  HASHBUCKET *oldPrevPtr;
1127  HashCompareFunc match;
1128 
1129 #if HASH_STATISTICS
1130  hash_accesses++;
1131  hctl->accesses++;
1132 #endif
1133 
1134  /* disallow updates if frozen */
1135  if (hashp->frozen)
1136  elog(ERROR, "cannot update in frozen hashtable \"%s\"",
1137  hashp->tabname);
1138 
1139  /*
1140  * Lookup the existing element using its saved hash value. We need to do
1141  * this to be able to unlink it from its hash chain, but as a side benefit
1142  * we can verify the validity of the passed existingEntry pointer.
1143  */
1144  bucket = calc_bucket(hctl, existingElement->hashvalue);
1145 
1146  segment_num = bucket >> hashp->sshift;
1147  segment_ndx = MOD(bucket, hashp->ssize);
1148 
1149  segp = hashp->dir[segment_num];
1150 
1151  if (segp == NULL)
1152  hash_corrupted(hashp);
1153 
1154  prevBucketPtr = &segp[segment_ndx];
1155  currBucket = *prevBucketPtr;
1156 
1157  while (currBucket != NULL)
1158  {
1159  if (currBucket == existingElement)
1160  break;
1161  prevBucketPtr = &(currBucket->link);
1162  currBucket = *prevBucketPtr;
1163  }
1164 
1165  if (currBucket == NULL)
1166  elog(ERROR, "hash_update_hash_key argument is not in hashtable \"%s\"",
1167  hashp->tabname);
1168 
1169  oldPrevPtr = prevBucketPtr;
1170 
1171  /*
1172  * Now perform the equivalent of a HASH_ENTER operation to locate the hash
1173  * chain we want to put the entry into.
1174  */
1175  newhashvalue = hashp->hash(newKeyPtr, hashp->keysize);
1176 
1177  newbucket = calc_bucket(hctl, newhashvalue);
1178 
1179  segment_num = newbucket >> hashp->sshift;
1180  segment_ndx = MOD(newbucket, hashp->ssize);
1181 
1182  segp = hashp->dir[segment_num];
1183 
1184  if (segp == NULL)
1185  hash_corrupted(hashp);
1186 
1187  prevBucketPtr = &segp[segment_ndx];
1188  currBucket = *prevBucketPtr;
1189 
1190  /*
1191  * Follow collision chain looking for matching key
1192  */
1193  match = hashp->match; /* save one fetch in inner loop */
1194  keysize = hashp->keysize; /* ditto */
1195 
1196  while (currBucket != NULL)
1197  {
1198  if (currBucket->hashvalue == newhashvalue &&
1199  match(ELEMENTKEY(currBucket), newKeyPtr, keysize) == 0)
1200  break;
1201  prevBucketPtr = &(currBucket->link);
1202  currBucket = *prevBucketPtr;
1203 #if HASH_STATISTICS
1204  hash_collisions++;
1205  hctl->collisions++;
1206 #endif
1207  }
1208 
1209  if (currBucket != NULL)
1210  return false; /* collision with an existing entry */
1211 
1212  currBucket = existingElement;
1213 
1214  /*
1215  * If old and new hash values belong to the same bucket, we need not
1216  * change any chain links, and indeed should not since this simplistic
1217  * update will corrupt the list if currBucket is the last element. (We
1218  * cannot fall out earlier, however, since we need to scan the bucket to
1219  * check for duplicate keys.)
1220  */
1221  if (bucket != newbucket)
1222  {
1223  /* OK to remove record from old hash bucket's chain. */
1224  *oldPrevPtr = currBucket->link;
1225 
1226  /* link into new hashbucket chain */
1227  *prevBucketPtr = currBucket;
1228  currBucket->link = NULL;
1229  }
1230 
1231  /* copy new key into record */
1232  currBucket->hashvalue = newhashvalue;
1233  hashp->keycopy(ELEMENTKEY(currBucket), newKeyPtr, keysize);
1234 
1235  /* rest of record is untouched */
1236 
1237  return true;
1238 }
1239 
1240 /*
1241  * Allocate a new hashtable entry if possible; return NULL if out of memory.
1242  * (Or, if the underlying space allocator throws error for out-of-memory,
1243  * we won't return at all.)
1244  */
1245 static HASHBUCKET
1246 get_hash_entry(HTAB *hashp, int freelist_idx)
1247 {
1248  HASHHDR *hctl = hashp->hctl;
1249  HASHBUCKET newElement;
1250 
1251  for (;;)
1252  {
1253  /* if partitioned, must lock to touch nentries and freeList */
1254  if (IS_PARTITIONED(hctl))
1255  SpinLockAcquire(&hctl->freeList[freelist_idx].mutex);
1256 
1257  /* try to get an entry from the freelist */
1258  newElement = hctl->freeList[freelist_idx].freeList;
1259 
1260  if (newElement != NULL)
1261  break;
1262 
1263  if (IS_PARTITIONED(hctl))
1264  SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1265 
1266  /*
1267  * No free elements in this freelist. In a partitioned table, there
1268  * might be entries in other freelists, but to reduce contention we
1269  * prefer to first try to get another chunk of buckets from the main
1270  * shmem allocator. If that fails, though, we *MUST* root through all
1271  * the other freelists before giving up. There are multiple callers
1272  * that assume that they can allocate every element in the initially
1273  * requested table size, or that deleting an element guarantees they
1274  * can insert a new element, even if shared memory is entirely full.
1275  * Failing because the needed element is in a different freelist is
1276  * not acceptable.
1277  */
1278  if (!element_alloc(hashp, hctl->nelem_alloc, freelist_idx))
1279  {
1280  int borrow_from_idx;
1281 
1282  if (!IS_PARTITIONED(hctl))
1283  return NULL; /* out of memory */
1284 
1285  /* try to borrow element from another freelist */
1286  borrow_from_idx = freelist_idx;
1287  for (;;)
1288  {
1289  borrow_from_idx = (borrow_from_idx + 1) % NUM_FREELISTS;
1290  if (borrow_from_idx == freelist_idx)
1291  break; /* examined all freelists, fail */
1292 
1293  SpinLockAcquire(&(hctl->freeList[borrow_from_idx].mutex));
1294  newElement = hctl->freeList[borrow_from_idx].freeList;
1295 
1296  if (newElement != NULL)
1297  {
1298  hctl->freeList[borrow_from_idx].freeList = newElement->link;
1299  SpinLockRelease(&(hctl->freeList[borrow_from_idx].mutex));
1300 
1301  /* careful: count the new element in its proper freelist */
1302  SpinLockAcquire(&hctl->freeList[freelist_idx].mutex);
1303  hctl->freeList[freelist_idx].nentries++;
1304  SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1305 
1306  return newElement;
1307  }
1308 
1309  SpinLockRelease(&(hctl->freeList[borrow_from_idx].mutex));
1310  }
1311 
1312  /* no elements available to borrow either, so out of memory */
1313  return NULL;
1314  }
1315  }
1316 
1317  /* remove entry from freelist, bump nentries */
1318  hctl->freeList[freelist_idx].freeList = newElement->link;
1319  hctl->freeList[freelist_idx].nentries++;
1320 
1321  if (IS_PARTITIONED(hctl))
1322  SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1323 
1324  return newElement;
1325 }
1326 
1327 /*
1328  * hash_get_num_entries -- get the number of entries in a hashtable
1329  */
1330 long
1332 {
1333  int i;
1334  long sum = hashp->hctl->freeList[0].nentries;
1335 
1336  /*
1337  * We currently don't bother with acquiring the mutexes; it's only
1338  * sensible to call this function if you've got lock on all partitions of
1339  * the table.
1340  */
1341  if (IS_PARTITIONED(hashp->hctl))
1342  {
1343  for (i = 1; i < NUM_FREELISTS; i++)
1344  sum += hashp->hctl->freeList[i].nentries;
1345  }
1346 
1347  return sum;
1348 }
1349 
1350 /*
1351  * hash_seq_init/_search/_term
1352  * Sequentially search through hash table and return
1353  * all the elements one by one, return NULL when no more.
1354  *
1355  * hash_seq_term should be called if and only if the scan is abandoned before
1356  * completion; if hash_seq_search returns NULL then it has already done the
1357  * end-of-scan cleanup.
1358  *
1359  * NOTE: caller may delete the returned element before continuing the scan.
1360  * However, deleting any other element while the scan is in progress is
1361  * UNDEFINED (it might be the one that curIndex is pointing at!). Also,
1362  * if elements are added to the table while the scan is in progress, it is
1363  * unspecified whether they will be visited by the scan or not.
1364  *
1365  * NOTE: it is possible to use hash_seq_init/hash_seq_search without any
1366  * worry about hash_seq_term cleanup, if the hashtable is first locked against
1367  * further insertions by calling hash_freeze.
1368  *
1369  * NOTE: to use this with a partitioned hashtable, caller had better hold
1370  * at least shared lock on all partitions of the table throughout the scan!
1371  * We can cope with insertions or deletions by our own backend, but *not*
1372  * with concurrent insertions or deletions by another.
1373  */
1374 void
1376 {
1377  status->hashp = hashp;
1378  status->curBucket = 0;
1379  status->curEntry = NULL;
1380  if (!hashp->frozen)
1381  register_seq_scan(hashp);
1382 }
1383 
1384 void *
1386 {
1387  HTAB *hashp;
1388  HASHHDR *hctl;
1390  long ssize;
1391  long segment_num;
1392  long segment_ndx;
1393  HASHSEGMENT segp;
1394  uint32 curBucket;
1395  HASHELEMENT *curElem;
1396 
1397  if ((curElem = status->curEntry) != NULL)
1398  {
1399  /* Continuing scan of curBucket... */
1400  status->curEntry = curElem->link;
1401  if (status->curEntry == NULL) /* end of this bucket */
1402  ++status->curBucket;
1403  return (void *) ELEMENTKEY(curElem);
1404  }
1405 
1406  /*
1407  * Search for next nonempty bucket starting at curBucket.
1408  */
1409  curBucket = status->curBucket;
1410  hashp = status->hashp;
1411  hctl = hashp->hctl;
1412  ssize = hashp->ssize;
1413  max_bucket = hctl->max_bucket;
1414 
1415  if (curBucket > max_bucket)
1416  {
1417  hash_seq_term(status);
1418  return NULL; /* search is done */
1419  }
1420 
1421  /*
1422  * first find the right segment in the table directory.
1423  */
1424  segment_num = curBucket >> hashp->sshift;
1425  segment_ndx = MOD(curBucket, ssize);
1426 
1427  segp = hashp->dir[segment_num];
1428 
1429  /*
1430  * Pick up the first item in this bucket's chain. If chain is not empty
1431  * we can begin searching it. Otherwise we have to advance to find the
1432  * next nonempty bucket. We try to optimize that case since searching a
1433  * near-empty hashtable has to iterate this loop a lot.
1434  */
1435  while ((curElem = segp[segment_ndx]) == NULL)
1436  {
1437  /* empty bucket, advance to next */
1438  if (++curBucket > max_bucket)
1439  {
1440  status->curBucket = curBucket;
1441  hash_seq_term(status);
1442  return NULL; /* search is done */
1443  }
1444  if (++segment_ndx >= ssize)
1445  {
1446  segment_num++;
1447  segment_ndx = 0;
1448  segp = hashp->dir[segment_num];
1449  }
1450  }
1451 
1452  /* Begin scan of curBucket... */
1453  status->curEntry = curElem->link;
1454  if (status->curEntry == NULL) /* end of this bucket */
1455  ++curBucket;
1456  status->curBucket = curBucket;
1457  return (void *) ELEMENTKEY(curElem);
1458 }
1459 
1460 void
1462 {
1463  if (!status->hashp->frozen)
1464  deregister_seq_scan(status->hashp);
1465 }
1466 
1467 /*
1468  * hash_freeze
1469  * Freeze a hashtable against future insertions (deletions are
1470  * still allowed)
1471  *
1472  * The reason for doing this is that by preventing any more bucket splits,
1473  * we no longer need to worry about registering hash_seq_search scans,
1474  * and thus caller need not be careful about ensuring hash_seq_term gets
1475  * called at the right times.
1476  *
1477  * Multiple calls to hash_freeze() are allowed, but you can't freeze a table
1478  * with active scans (since hash_seq_term would then do the wrong thing).
1479  */
1480 void
1482 {
1483  if (hashp->isshared)
1484  elog(ERROR, "cannot freeze shared hashtable \"%s\"", hashp->tabname);
1485  if (!hashp->frozen && has_seq_scans(hashp))
1486  elog(ERROR, "cannot freeze hashtable \"%s\" because it has active scans",
1487  hashp->tabname);
1488  hashp->frozen = true;
1489 }
1490 
1491 
1492 /********************************* UTILITIES ************************/
1493 
1494 /*
1495  * Expand the table by adding one more hash bucket.
1496  */
1497 static bool
1499 {
1500  HASHHDR *hctl = hashp->hctl;
1501  HASHSEGMENT old_seg,
1502  new_seg;
1503  long old_bucket,
1504  new_bucket;
1505  long new_segnum,
1506  new_segndx;
1507  long old_segnum,
1508  old_segndx;
1509  HASHBUCKET *oldlink,
1510  *newlink;
1511  HASHBUCKET currElement,
1512  nextElement;
1513 
1514  Assert(!IS_PARTITIONED(hctl));
1515 
1516 #ifdef HASH_STATISTICS
1517  hash_expansions++;
1518 #endif
1519 
1520  new_bucket = hctl->max_bucket + 1;
1521  new_segnum = new_bucket >> hashp->sshift;
1522  new_segndx = MOD(new_bucket, hashp->ssize);
1523 
1524  if (new_segnum >= hctl->nsegs)
1525  {
1526  /* Allocate new segment if necessary -- could fail if dir full */
1527  if (new_segnum >= hctl->dsize)
1528  if (!dir_realloc(hashp))
1529  return false;
1530  if (!(hashp->dir[new_segnum] = seg_alloc(hashp)))
1531  return false;
1532  hctl->nsegs++;
1533  }
1534 
1535  /* OK, we created a new bucket */
1536  hctl->max_bucket++;
1537 
1538  /*
1539  * *Before* changing masks, find old bucket corresponding to same hash
1540  * values; values in that bucket may need to be relocated to new bucket.
1541  * Note that new_bucket is certainly larger than low_mask at this point,
1542  * so we can skip the first step of the regular hash mask calc.
1543  */
1544  old_bucket = (new_bucket & hctl->low_mask);
1545 
1546  /*
1547  * If we crossed a power of 2, readjust masks.
1548  */
1549  if ((uint32) new_bucket > hctl->high_mask)
1550  {
1551  hctl->low_mask = hctl->high_mask;
1552  hctl->high_mask = (uint32) new_bucket | hctl->low_mask;
1553  }
1554 
1555  /*
1556  * Relocate records to the new bucket. NOTE: because of the way the hash
1557  * masking is done in calc_bucket, only one old bucket can need to be
1558  * split at this point. With a different way of reducing the hash value,
1559  * that might not be true!
1560  */
1561  old_segnum = old_bucket >> hashp->sshift;
1562  old_segndx = MOD(old_bucket, hashp->ssize);
1563 
1564  old_seg = hashp->dir[old_segnum];
1565  new_seg = hashp->dir[new_segnum];
1566 
1567  oldlink = &old_seg[old_segndx];
1568  newlink = &new_seg[new_segndx];
1569 
1570  for (currElement = *oldlink;
1571  currElement != NULL;
1572  currElement = nextElement)
1573  {
1574  nextElement = currElement->link;
1575  if ((long) calc_bucket(hctl, currElement->hashvalue) == old_bucket)
1576  {
1577  *oldlink = currElement;
1578  oldlink = &currElement->link;
1579  }
1580  else
1581  {
1582  *newlink = currElement;
1583  newlink = &currElement->link;
1584  }
1585  }
1586  /* don't forget to terminate the rebuilt hash chains... */
1587  *oldlink = NULL;
1588  *newlink = NULL;
1589 
1590  return true;
1591 }
1592 
1593 
1594 static bool
1596 {
1597  HASHSEGMENT *p;
1598  HASHSEGMENT *old_p;
1599  long new_dsize;
1600  long old_dirsize;
1601  long new_dirsize;
1602 
1603  if (hashp->hctl->max_dsize != NO_MAX_DSIZE)
1604  return false;
1605 
1606  /* Reallocate directory */
1607  new_dsize = hashp->hctl->dsize << 1;
1608  old_dirsize = hashp->hctl->dsize * sizeof(HASHSEGMENT);
1609  new_dirsize = new_dsize * sizeof(HASHSEGMENT);
1610 
1611  old_p = hashp->dir;
1612  CurrentDynaHashCxt = hashp->hcxt;
1613  p = (HASHSEGMENT *) hashp->alloc((Size) new_dirsize);
1614 
1615  if (p != NULL)
1616  {
1617  memcpy(p, old_p, old_dirsize);
1618  MemSet(((char *) p) + old_dirsize, 0, new_dirsize - old_dirsize);
1619  hashp->dir = p;
1620  hashp->hctl->dsize = new_dsize;
1621 
1622  /* XXX assume the allocator is palloc, so we know how to free */
1623  Assert(hashp->alloc == DynaHashAlloc);
1624  pfree(old_p);
1625 
1626  return true;
1627  }
1628 
1629  return false;
1630 }
1631 
1632 
1633 static HASHSEGMENT
1635 {
1636  HASHSEGMENT segp;
1637 
1638  CurrentDynaHashCxt = hashp->hcxt;
1639  segp = (HASHSEGMENT) hashp->alloc(sizeof(HASHBUCKET) * hashp->ssize);
1640 
1641  if (!segp)
1642  return NULL;
1643 
1644  MemSet(segp, 0, sizeof(HASHBUCKET) * hashp->ssize);
1645 
1646  return segp;
1647 }
1648 
1649 /*
1650  * allocate some new elements and link them into the indicated free list
1651  */
1652 static bool
1653 element_alloc(HTAB *hashp, int nelem, int freelist_idx)
1654 {
1655  HASHHDR *hctl = hashp->hctl;
1656  Size elementSize;
1657  HASHELEMENT *firstElement;
1658  HASHELEMENT *tmpElement;
1659  HASHELEMENT *prevElement;
1660  int i;
1661 
1662  if (hashp->isfixed)
1663  return false;
1664 
1665  /* Each element has a HASHELEMENT header plus user data. */
1666  elementSize = MAXALIGN(sizeof(HASHELEMENT)) + MAXALIGN(hctl->entrysize);
1667 
1668  CurrentDynaHashCxt = hashp->hcxt;
1669  firstElement = (HASHELEMENT *) hashp->alloc(nelem * elementSize);
1670 
1671  if (!firstElement)
1672  return false;
1673 
1674  /* prepare to link all the new entries into the freelist */
1675  prevElement = NULL;
1676  tmpElement = firstElement;
1677  for (i = 0; i < nelem; i++)
1678  {
1679  tmpElement->link = prevElement;
1680  prevElement = tmpElement;
1681  tmpElement = (HASHELEMENT *) (((char *) tmpElement) + elementSize);
1682  }
1683 
1684  /* if partitioned, must lock to touch freeList */
1685  if (IS_PARTITIONED(hctl))
1686  SpinLockAcquire(&hctl->freeList[freelist_idx].mutex);
1687 
1688  /* freelist could be nonempty if two backends did this concurrently */
1689  firstElement->link = hctl->freeList[freelist_idx].freeList;
1690  hctl->freeList[freelist_idx].freeList = prevElement;
1691 
1692  if (IS_PARTITIONED(hctl))
1693  SpinLockRelease(&hctl->freeList[freelist_idx].mutex);
1694 
1695  return true;
1696 }
1697 
1698 /* complain when we have detected a corrupted hashtable */
1699 static void
1701 {
1702  /*
1703  * If the corruption is in a shared hashtable, we'd better force a
1704  * systemwide restart. Otherwise, just shut down this one backend.
1705  */
1706  if (hashp->isshared)
1707  elog(PANIC, "hash table \"%s\" corrupted", hashp->tabname);
1708  else
1709  elog(FATAL, "hash table \"%s\" corrupted", hashp->tabname);
1710 }
1711 
1712 /* calculate ceil(log base 2) of num */
1713 int
1714 my_log2(long num)
1715 {
1716  int i;
1717  long limit;
1718 
1719  /* guard against too-large input, which would put us into infinite loop */
1720  if (num > LONG_MAX / 2)
1721  num = LONG_MAX / 2;
1722 
1723  for (i = 0, limit = 1; limit < num; i++, limit <<= 1)
1724  ;
1725  return i;
1726 }
1727 
1728 /* calculate first power of 2 >= num, bounded to what will fit in a long */
1729 static long
1731 {
1732  /* my_log2's internal range check is sufficient */
1733  return 1L << my_log2(num);
1734 }
1735 
1736 /* calculate first power of 2 >= num, bounded to what will fit in an int */
1737 static int
1738 next_pow2_int(long num)
1739 {
1740  if (num > INT_MAX / 2)
1741  num = INT_MAX / 2;
1742  return 1 << my_log2(num);
1743 }
1744 
1745 
1746 /************************* SEQ SCAN TRACKING ************************/
1747 
1748 /*
1749  * We track active hash_seq_search scans here. The need for this mechanism
1750  * comes from the fact that a scan will get confused if a bucket split occurs
1751  * while it's in progress: it might visit entries twice, or even miss some
1752  * entirely (if it's partway through the same bucket that splits). Hence
1753  * we want to inhibit bucket splits if there are any active scans on the
1754  * table being inserted into. This is a fairly rare case in current usage,
1755  * so just postponing the split until the next insertion seems sufficient.
1756  *
1757  * Given present usages of the function, only a few scans are likely to be
1758  * open concurrently; so a finite-size stack of open scans seems sufficient,
1759  * and we don't worry that linear search is too slow. Note that we do
1760  * allow multiple scans of the same hashtable to be open concurrently.
1761  *
1762  * This mechanism can support concurrent scan and insertion in a shared
1763  * hashtable if it's the same backend doing both. It would fail otherwise,
1764  * but locking reasons seem to preclude any such scenario anyway, so we don't
1765  * worry.
1766  *
1767  * This arrangement is reasonably robust if a transient hashtable is deleted
1768  * without notifying us. The absolute worst case is we might inhibit splits
1769  * in another table created later at exactly the same address. We will give
1770  * a warning at transaction end for reference leaks, so any bugs leading to
1771  * lack of notification should be easy to catch.
1772  */
1773 
1774 #define MAX_SEQ_SCANS 100
1775 
1776 static HTAB *seq_scan_tables[MAX_SEQ_SCANS]; /* tables being scanned */
1777 static int seq_scan_level[MAX_SEQ_SCANS]; /* subtransaction nest level */
1778 static int num_seq_scans = 0;
1779 
1780 
1781 /* Register a table as having an active hash_seq_search scan */
1782 static void
1784 {
1786  elog(ERROR, "too many active hash_seq_search scans, cannot start one on \"%s\"",
1787  hashp->tabname);
1788  seq_scan_tables[num_seq_scans] = hashp;
1790  num_seq_scans++;
1791 }
1792 
1793 /* Deregister an active scan */
1794 static void
1796 {
1797  int i;
1798 
1799  /* Search backward since it's most likely at the stack top */
1800  for (i = num_seq_scans - 1; i >= 0; i--)
1801  {
1802  if (seq_scan_tables[i] == hashp)
1803  {
1804  seq_scan_tables[i] = seq_scan_tables[num_seq_scans - 1];
1806  num_seq_scans--;
1807  return;
1808  }
1809  }
1810  elog(ERROR, "no hash_seq_search scan for hash table \"%s\"",
1811  hashp->tabname);
1812 }
1813 
1814 /* Check if a table has any active scan */
1815 static bool
1817 {
1818  int i;
1819 
1820  for (i = 0; i < num_seq_scans; i++)
1821  {
1822  if (seq_scan_tables[i] == hashp)
1823  return true;
1824  }
1825  return false;
1826 }
1827 
1828 /* Clean up any open scans at end of transaction */
1829 void
1830 AtEOXact_HashTables(bool isCommit)
1831 {
1832  /*
1833  * During abort cleanup, open scans are expected; just silently clean 'em
1834  * out. An open scan at commit means someone forgot a hash_seq_term()
1835  * call, so complain.
1836  *
1837  * Note: it's tempting to try to print the tabname here, but refrain for
1838  * fear of touching deallocated memory. This isn't a user-facing message
1839  * anyway, so it needn't be pretty.
1840  */
1841  if (isCommit)
1842  {
1843  int i;
1844 
1845  for (i = 0; i < num_seq_scans; i++)
1846  {
1847  elog(WARNING, "leaked hash_seq_search scan for hash table %p",
1848  seq_scan_tables[i]);
1849  }
1850  }
1851  num_seq_scans = 0;
1852 }
1853 
1854 /* Clean up any open scans at end of subtransaction */
1855 void
1856 AtEOSubXact_HashTables(bool isCommit, int nestDepth)
1857 {
1858  int i;
1859 
1860  /*
1861  * Search backward to make cleanup easy. Note we must check all entries,
1862  * not only those at the end of the array, because deletion technique
1863  * doesn't keep them in order.
1864  */
1865  for (i = num_seq_scans - 1; i >= 0; i--)
1866  {
1867  if (seq_scan_level[i] >= nestDepth)
1868  {
1869  if (isCommit)
1870  elog(WARNING, "leaked hash_seq_search scan for hash table %p",
1871  seq_scan_tables[i]);
1872  seq_scan_tables[i] = seq_scan_tables[num_seq_scans - 1];
1874  num_seq_scans--;
1875  }
1876  }
1877 }
void * hash_search_with_hash_value(HTAB *hashp, const void *keyPtr, uint32 hashvalue, HASHACTION action, bool *foundPtr)
Definition: dynahash.c:915
static int seq_scan_level[MAX_SEQ_SCANS]
Definition: dynahash.c:1777
int(* HashCompareFunc)(const void *key1, const void *key2, Size keysize)
Definition: hsearch.h:29
Size keysize
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int slock_t
Definition: s_lock.h:888
Size keysize
Definition: dynahash.c:225
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Definition: dynahash.c:172
uint32(* HashValueFunc)(const void *key, Size keysize)
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uint32 curBucket
Definition: hsearch.h:115
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Definition: dynahash.c:810
void MemoryContextDelete(MemoryContext context)
Definition: mcxt.c:200
#define HASH_CONTEXT
Definition: hsearch.h:93
#define HASH_ELEM
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uint32 max_bucket
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MemoryContext hcxt
Definition: hsearch.h:78
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HashCopyFunc keycopy
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Size entrysize
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static uint32 calc_bucket(HASHHDR *hctl, uint32 hash_val)
Definition: dynahash.c:863
#define IS_PARTITIONED(hctl)
Definition: dynahash.c:199
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Definition: hashfn.c:34
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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:181
void AtEOSubXact_HashTables(bool isCommit, int nestDepth)
Definition: dynahash.c:1856
Size entrysize
Definition: hsearch.h:73
#define NUM_FREELISTS
Definition: dynahash.c:116
void hash_stats(const char *where, HTAB *hashp)
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HashAllocFunc alloc
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HASHELEMENT * curEntry
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Definition: dynahash.c:143
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Definition: dynahash.c:176
void * hash_search(HTAB *hashp, const void *keyPtr, HASHACTION action, bool *foundPtr)
Definition: dynahash.c:902
#define HASH_SHARED_MEM
Definition: hsearch.h:94
static int string_compare(const char *key1, const char *key2, Size keysize)
Definition: dynahash.c:293
static HASHBUCKET get_hash_entry(HTAB *hashp, int freelist_idx)
Definition: dynahash.c:1246
long dsize
Definition: hsearch.h:69
#define PANIC
Definition: elog.h:53
uint32 uint32_hash(const void *key, Size keysize)
Definition: hashfn.c:64
#define HASH_PARTITION
Definition: hsearch.h:83
#define HASH_ATTACH
Definition: hsearch.h:95
char bool
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Definition: dynahash.c:212
#define SpinLockAcquire(lock)
Definition: spin.h:62
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Definition: dynahash.c:856
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Definition: hsearch.h:70
void pfree(void *pointer)
Definition: mcxt.c:949
HASHBUCKET * HASHSEGMENT
Definition: dynahash.c:122
long ssize
Definition: dynahash.c:226
#define ERROR
Definition: elog.h:43
long num_partitions
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#define FATAL
Definition: elog.h:52
int sshift
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Definition: memutils.h:165
#define DEF_SEGSIZE_SHIFT
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HashAllocFunc alloc
Definition: hsearch.h:77
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Definition: dynahash.c:210
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Definition: dynahash.c:1700
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Definition: dynahash.c:1816
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Definition: hsearch.h:58
unsigned int uint32
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HASHELEMENT * HASHBUCKET
Definition: dynahash.c:119
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Definition: hsearch.h:114
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Definition: dynahash.c:175
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Definition: dynahash.c:144
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Definition: elog.h:122
MemoryContext TopMemoryContext
Definition: mcxt.c:43
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Definition: dynahash.c:1714
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HashCompareFunc match
Definition: dynahash.c:213
Size hash_estimate_size(long num_entries, Size entrysize)
Definition: dynahash.c:728
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Definition: dynahash.c:1738
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Definition: dynahash.c:218
#define SpinLockRelease(lock)
Definition: spin.h:64
#define MAX_SEQ_SCANS
Definition: dynahash.c:1774
#define HASH_BLOBS
Definition: hsearch.h:88
bool frozen
Definition: dynahash.c:222
Size mul_size(Size s1, Size s2)
Definition: shmem.c:492
MemoryContext AllocSetContextCreate(MemoryContext parent, const char *name, Size minContextSize, Size initBlockSize, Size maxBlockSize)
Definition: aset.c:322
static int num_seq_scans
Definition: dynahash.c:1778
static HTAB * seq_scan_tables[MAX_SEQ_SCANS]
Definition: dynahash.c:1776
uint32 tag_hash(const void *key, Size keysize)
Definition: hashfn.c:52
HTAB * hash_create(const char *tabname, long nelem, HASHCTL *info, int flags)
Definition: dynahash.c:316
long ssize
Definition: dynahash.c:184
Size add_size(Size s1, Size s2)
Definition: shmem.c:475
FreeListData freeList[NUM_FREELISTS]
Definition: dynahash.c:168
static void deregister_seq_scan(HTAB *hashp)
Definition: dynahash.c:1795
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:216
long hash_select_dirsize(long num_entries)
Definition: dynahash.c:775
HashCopyFunc keycopy
Definition: dynahash.c:214
#define HASH_SEGMENT
Definition: hsearch.h:84
int GetCurrentTransactionNestLevel(void)
Definition: xact.c:754
size_t strlcpy(char *dst, const char *src, size_t siz)
Definition: strlcpy.c:45
#define MemoryContextIsValid(context)
Definition: memnodes.h:97
static void register_seq_scan(HTAB *hashp)
Definition: dynahash.c:1783
#define Assert(condition)
Definition: c.h:670
int nelem_alloc
Definition: dynahash.c:186
void *(* HashAllocFunc)(Size request)
Definition: hsearch.h:44
#define HASH_COMPARE
Definition: hsearch.h:90
size_t Size
Definition: c.h:404
void hash_freeze(HTAB *hashp)
Definition: dynahash.c:1481
static HASHSEGMENT seg_alloc(HTAB *hashp)
Definition: dynahash.c:1634
#define MAXALIGN(LEN)
Definition: c.h:623
Size hash_get_shared_size(HASHCTL *info, int flags)
Definition: dynahash.c:799
static bool expand_table(HTAB *hashp)
Definition: dynahash.c:1498
bool hash_update_hash_key(HTAB *hashp, void *existingEntry, const void *newKeyPtr)
Definition: dynahash.c:1111
HASHHDR * hctl
Definition: hsearch.h:79
void * hash_seq_search(HASH_SEQ_STATUS *status)
Definition: dynahash.c:1385
long ffactor
Definition: hsearch.h:71
void hash_seq_init(HASH_SEQ_STATUS *status, HTAB *hashp)
Definition: dynahash.c:1375
char * tabname
Definition: dynahash.c:217
#define HASH_FIXED_SIZE
Definition: hsearch.h:96
bool isfixed
Definition: dynahash.c:219
#define HASH_FFACTOR
Definition: hsearch.h:86
static void * DynaHashAlloc(Size size)
Definition: dynahash.c:278
#define HASH_DIRSIZE
Definition: hsearch.h:85
int errmsg(const char *fmt,...)
Definition: elog.c:797
void * MemoryContextAlloc(MemoryContext context, Size size)
Definition: mcxt.c:706
struct HASHELEMENT * link
Definition: hsearch.h:53
static int choose_nelem_alloc(Size entrysize)
Definition: dynahash.c:599
static MemoryContext CurrentDynaHashCxt
Definition: dynahash.c:275
int i
#define HASH_ALLOC
Definition: hsearch.h:92
HASHELEMENT * freeList
Definition: dynahash.c:145
HASHSEGMENT * dir
Definition: dynahash.c:211
#define elog
Definition: elog.h:219
static bool element_alloc(HTAB *hashp, int nelem, int freelist_idx)
Definition: dynahash.c:1653
#define FREELIST_IDX(hctl, hashcode)
Definition: dynahash.c:201
void AtEOXact_HashTables(bool isCommit)
Definition: dynahash.c:1830
static void static void status(const char *fmt,...) pg_attribute_printf(1
Definition: pg_regress.c:225
int sshift
Definition: dynahash.c:185
static bool dir_realloc(HTAB *hashp)
Definition: dynahash.c:1595
#define DEF_FFACTOR
Definition: dynahash.c:113
#define DEF_SEGSIZE
Definition: dynahash.c:110
void hash_seq_term(HASH_SEQ_STATUS *status)
Definition: dynahash.c:1461
uint32 hashvalue
Definition: hsearch.h:54
HASHACTION
Definition: hsearch.h:103
HashValueFunc hash
Definition: hsearch.h:74
#define HASH_FUNCTION
Definition: hsearch.h:89
#define DEF_DIRSIZE
Definition: dynahash.c:112
long nsegs
Definition: dynahash.c:173