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mvdistinct.c
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1 /*-------------------------------------------------------------------------
2  *
3  * mvdistinct.c
4  * POSTGRES multivariate ndistinct coefficients
5  *
6  * Estimating number of groups in a combination of columns (e.g. for GROUP BY)
7  * is tricky, and the estimation error is often significant.
8 
9  * The multivariate ndistinct coefficients address this by storing ndistinct
10  * estimates for combinations of the user-specified columns. So for example
11  * given a statistics object on three columns (a,b,c), this module estimates
12  * and stores n-distinct for (a,b), (a,c), (b,c) and (a,b,c). The per-column
13  * estimates are already available in pg_statistic.
14  *
15  *
16  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
17  * Portions Copyright (c) 1994, Regents of the University of California
18  *
19  * IDENTIFICATION
20  * src/backend/statistics/mvdistinct.c
21  *
22  *-------------------------------------------------------------------------
23  */
24 #include "postgres.h"
25 
26 #include <math.h>
27 
28 #include "access/htup_details.h"
31 #include "lib/stringinfo.h"
33 #include "statistics/statistics.h"
34 #include "utils/fmgrprotos.h"
35 #include "utils/lsyscache.h"
36 #include "utils/syscache.h"
37 #include "utils/typcache.h"
38 
39 static double ndistinct_for_combination(double totalrows, StatsBuildData *data,
40  int k, int *combination);
41 static double estimate_ndistinct(double totalrows, int numrows, int d, int f1);
42 static int n_choose_k(int n, int k);
43 static int num_combinations(int n);
44 
45 /* size of the struct header fields (magic, type, nitems) */
46 #define SizeOfHeader (3 * sizeof(uint32))
47 
48 /* size of a serialized ndistinct item (coefficient, natts, atts) */
49 #define SizeOfItem(natts) \
50  (sizeof(double) + sizeof(int) + (natts) * sizeof(AttrNumber))
51 
52 /* minimal size of a ndistinct item (with two attributes) */
53 #define MinSizeOfItem SizeOfItem(2)
54 
55 /* minimal size of mvndistinct, when all items are minimal */
56 #define MinSizeOfItems(nitems) \
57  (SizeOfHeader + (nitems) * MinSizeOfItem)
58 
59 /* Combination generator API */
60 
61 /* internal state for generator of k-combinations of n elements */
62 typedef struct CombinationGenerator
63 {
64  int k; /* size of the combination */
65  int n; /* total number of elements */
66  int current; /* index of the next combination to return */
67  int ncombinations; /* number of combinations (size of array) */
68  int *combinations; /* array of pre-built combinations */
70 
71 static CombinationGenerator *generator_init(int n, int k);
75 
76 
77 /*
78  * statext_ndistinct_build
79  * Compute ndistinct coefficient for the combination of attributes.
80  *
81  * This computes the ndistinct estimate using the same estimator used
82  * in analyze.c and then computes the coefficient.
83  *
84  * To handle expressions easily, we treat them as system attributes with
85  * negative attnums, and offset everything by number of expressions to
86  * allow using Bitmapsets.
87  */
89 statext_ndistinct_build(double totalrows, StatsBuildData *data)
90 {
91  MVNDistinct *result;
92  int k;
93  int itemcnt;
94  int numattrs = data->nattnums;
95  int numcombs = num_combinations(numattrs);
96 
97  result = palloc(offsetof(MVNDistinct, items) +
98  numcombs * sizeof(MVNDistinctItem));
99  result->magic = STATS_NDISTINCT_MAGIC;
101  result->nitems = numcombs;
102 
103  itemcnt = 0;
104  for (k = 2; k <= numattrs; k++)
105  {
106  int *combination;
108 
109  /* generate combinations of K out of N elements */
110  generator = generator_init(numattrs, k);
111 
112  while ((combination = generator_next(generator)))
113  {
114  MVNDistinctItem *item = &result->items[itemcnt];
115  int j;
116 
117  item->attributes = palloc(sizeof(AttrNumber) * k);
118  item->nattributes = k;
119 
120  /* translate the indexes to attnums */
121  for (j = 0; j < k; j++)
122  {
123  item->attributes[j] = data->attnums[combination[j]];
124 
126  }
127 
128  item->ndistinct =
129  ndistinct_for_combination(totalrows, data, k, combination);
130 
131  itemcnt++;
132  Assert(itemcnt <= result->nitems);
133  }
134 
135  generator_free(generator);
136  }
137 
138  /* must consume exactly the whole output array */
139  Assert(itemcnt == result->nitems);
140 
141  return result;
142 }
143 
144 /*
145  * statext_ndistinct_load
146  * Load the ndistinct value for the indicated pg_statistic_ext tuple
147  */
148 MVNDistinct *
150 {
151  MVNDistinct *result;
152  bool isnull;
153  Datum ndist;
154  HeapTuple htup;
155 
157  if (!HeapTupleIsValid(htup))
158  elog(ERROR, "cache lookup failed for statistics object %u", mvoid);
159 
160  ndist = SysCacheGetAttr(STATEXTDATASTXOID, htup,
161  Anum_pg_statistic_ext_data_stxdndistinct, &isnull);
162  if (isnull)
163  elog(ERROR,
164  "requested statistics kind \"%c\" is not yet built for statistics object %u",
165  STATS_EXT_NDISTINCT, mvoid);
166 
168 
169  ReleaseSysCache(htup);
170 
171  return result;
172 }
173 
174 /*
175  * statext_ndistinct_serialize
176  * serialize ndistinct to the on-disk bytea format
177  */
178 bytea *
180 {
181  int i;
182  bytea *output;
183  char *tmp;
184  Size len;
185 
186  Assert(ndistinct->magic == STATS_NDISTINCT_MAGIC);
187  Assert(ndistinct->type == STATS_NDISTINCT_TYPE_BASIC);
188 
189  /*
190  * Base size is size of scalar fields in the struct, plus one base struct
191  * for each item, including number of items for each.
192  */
193  len = VARHDRSZ + SizeOfHeader;
194 
195  /* and also include space for the actual attribute numbers */
196  for (i = 0; i < ndistinct->nitems; i++)
197  {
198  int nmembers;
199 
200  nmembers = ndistinct->items[i].nattributes;
201  Assert(nmembers >= 2);
202 
203  len += SizeOfItem(nmembers);
204  }
205 
206  output = (bytea *) palloc(len);
207  SET_VARSIZE(output, len);
208 
209  tmp = VARDATA(output);
210 
211  /* Store the base struct values (magic, type, nitems) */
212  memcpy(tmp, &ndistinct->magic, sizeof(uint32));
213  tmp += sizeof(uint32);
214  memcpy(tmp, &ndistinct->type, sizeof(uint32));
215  tmp += sizeof(uint32);
216  memcpy(tmp, &ndistinct->nitems, sizeof(uint32));
217  tmp += sizeof(uint32);
218 
219  /*
220  * store number of attributes and attribute numbers for each entry
221  */
222  for (i = 0; i < ndistinct->nitems; i++)
223  {
224  MVNDistinctItem item = ndistinct->items[i];
225  int nmembers = item.nattributes;
226 
227  memcpy(tmp, &item.ndistinct, sizeof(double));
228  tmp += sizeof(double);
229  memcpy(tmp, &nmembers, sizeof(int));
230  tmp += sizeof(int);
231 
232  memcpy(tmp, item.attributes, sizeof(AttrNumber) * nmembers);
233  tmp += nmembers * sizeof(AttrNumber);
234 
235  /* protect against overflows */
236  Assert(tmp <= ((char *) output + len));
237  }
238 
239  /* check we used exactly the expected space */
240  Assert(tmp == ((char *) output + len));
241 
242  return output;
243 }
244 
245 /*
246  * statext_ndistinct_deserialize
247  * Read an on-disk bytea format MVNDistinct to in-memory format
248  */
249 MVNDistinct *
251 {
252  int i;
253  Size minimum_size;
254  MVNDistinct ndist;
255  MVNDistinct *ndistinct;
256  char *tmp;
257 
258  if (data == NULL)
259  return NULL;
260 
261  /* we expect at least the basic fields of MVNDistinct struct */
262  if (VARSIZE_ANY_EXHDR(data) < SizeOfHeader)
263  elog(ERROR, "invalid MVNDistinct size %zd (expected at least %zd)",
265 
266  /* initialize pointer to the data part (skip the varlena header) */
267  tmp = VARDATA_ANY(data);
268 
269  /* read the header fields and perform basic sanity checks */
270  memcpy(&ndist.magic, tmp, sizeof(uint32));
271  tmp += sizeof(uint32);
272  memcpy(&ndist.type, tmp, sizeof(uint32));
273  tmp += sizeof(uint32);
274  memcpy(&ndist.nitems, tmp, sizeof(uint32));
275  tmp += sizeof(uint32);
276 
277  if (ndist.magic != STATS_NDISTINCT_MAGIC)
278  elog(ERROR, "invalid ndistinct magic %08x (expected %08x)",
280  if (ndist.type != STATS_NDISTINCT_TYPE_BASIC)
281  elog(ERROR, "invalid ndistinct type %d (expected %d)",
283  if (ndist.nitems == 0)
284  elog(ERROR, "invalid zero-length item array in MVNDistinct");
285 
286  /* what minimum bytea size do we expect for those parameters */
287  minimum_size = MinSizeOfItems(ndist.nitems);
288  if (VARSIZE_ANY_EXHDR(data) < minimum_size)
289  elog(ERROR, "invalid MVNDistinct size %zd (expected at least %zd)",
290  VARSIZE_ANY_EXHDR(data), minimum_size);
291 
292  /*
293  * Allocate space for the ndistinct items (no space for each item's
294  * attnos: those live in bitmapsets allocated separately)
295  */
296  ndistinct = palloc0(MAXALIGN(offsetof(MVNDistinct, items)) +
297  (ndist.nitems * sizeof(MVNDistinctItem)));
298  ndistinct->magic = ndist.magic;
299  ndistinct->type = ndist.type;
300  ndistinct->nitems = ndist.nitems;
301 
302  for (i = 0; i < ndistinct->nitems; i++)
303  {
304  MVNDistinctItem *item = &ndistinct->items[i];
305 
306  /* ndistinct value */
307  memcpy(&item->ndistinct, tmp, sizeof(double));
308  tmp += sizeof(double);
309 
310  /* number of attributes */
311  memcpy(&item->nattributes, tmp, sizeof(int));
312  tmp += sizeof(int);
313  Assert((item->nattributes >= 2) && (item->nattributes <= STATS_MAX_DIMENSIONS));
314 
315  item->attributes
316  = (AttrNumber *) palloc(item->nattributes * sizeof(AttrNumber));
317 
318  memcpy(item->attributes, tmp, sizeof(AttrNumber) * item->nattributes);
319  tmp += sizeof(AttrNumber) * item->nattributes;
320 
321  /* still within the bytea */
322  Assert(tmp <= ((char *) data + VARSIZE_ANY(data)));
323  }
324 
325  /* we should have consumed the whole bytea exactly */
326  Assert(tmp == ((char *) data + VARSIZE_ANY(data)));
327 
328  return ndistinct;
329 }
330 
331 /*
332  * pg_ndistinct_in
333  * input routine for type pg_ndistinct
334  *
335  * pg_ndistinct is real enough to be a table column, but it has no
336  * operations of its own, and disallows input (just like pg_node_tree).
337  */
338 Datum
340 {
341  ereport(ERROR,
342  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
343  errmsg("cannot accept a value of type %s", "pg_ndistinct")));
344 
345  PG_RETURN_VOID(); /* keep compiler quiet */
346 }
347 
348 /*
349  * pg_ndistinct
350  * output routine for type pg_ndistinct
351  *
352  * Produces a human-readable representation of the value.
353  */
354 Datum
356 {
357  bytea *data = PG_GETARG_BYTEA_PP(0);
359  int i;
361 
362  initStringInfo(&str);
363  appendStringInfoChar(&str, '{');
364 
365  for (i = 0; i < ndist->nitems; i++)
366  {
367  int j;
368  MVNDistinctItem item = ndist->items[i];
369 
370  if (i > 0)
371  appendStringInfoString(&str, ", ");
372 
373  for (j = 0; j < item.nattributes; j++)
374  {
375  AttrNumber attnum = item.attributes[j];
376 
377  appendStringInfo(&str, "%s%d", (j == 0) ? "\"" : ", ", attnum);
378  }
379  appendStringInfo(&str, "\": %d", (int) item.ndistinct);
380  }
381 
382  appendStringInfoChar(&str, '}');
383 
384  PG_RETURN_CSTRING(str.data);
385 }
386 
387 /*
388  * pg_ndistinct_recv
389  * binary input routine for type pg_ndistinct
390  */
391 Datum
393 {
394  ereport(ERROR,
395  (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
396  errmsg("cannot accept a value of type %s", "pg_ndistinct")));
397 
398  PG_RETURN_VOID(); /* keep compiler quiet */
399 }
400 
401 /*
402  * pg_ndistinct_send
403  * binary output routine for type pg_ndistinct
404  *
405  * n-distinct is serialized into a bytea value, so let's send that.
406  */
407 Datum
409 {
410  return byteasend(fcinfo);
411 }
412 
413 /*
414  * ndistinct_for_combination
415  * Estimates number of distinct values in a combination of columns.
416  *
417  * This uses the same ndistinct estimator as compute_scalar_stats() in
418  * ANALYZE, i.e.,
419  * n*d / (n - f1 + f1*n/N)
420  *
421  * except that instead of values in a single column we are dealing with
422  * combination of multiple columns.
423  */
424 static double
426  int k, int *combination)
427 {
428  int i,
429  j;
430  int f1,
431  cnt,
432  d;
433  bool *isnull;
434  Datum *values;
435  SortItem *items;
436  MultiSortSupport mss;
437  int numrows = data->numrows;
438 
439  mss = multi_sort_init(k);
440 
441  /*
442  * In order to determine the number of distinct elements, create separate
443  * values[]/isnull[] arrays with all the data we have, then sort them
444  * using the specified column combination as dimensions. We could try to
445  * sort in place, but it'd probably be more complex and bug-prone.
446  */
447  items = (SortItem *) palloc(numrows * sizeof(SortItem));
448  values = (Datum *) palloc0(sizeof(Datum) * numrows * k);
449  isnull = (bool *) palloc0(sizeof(bool) * numrows * k);
450 
451  for (i = 0; i < numrows; i++)
452  {
453  items[i].values = &values[i * k];
454  items[i].isnull = &isnull[i * k];
455  }
456 
457  /*
458  * For each dimension, set up sort-support and fill in the values from the
459  * sample data.
460  *
461  * We use the column data types' default sort operators and collations;
462  * perhaps at some point it'd be worth using column-specific collations?
463  */
464  for (i = 0; i < k; i++)
465  {
466  Oid typid;
468  Oid collid = InvalidOid;
469  VacAttrStats *colstat = data->stats[combination[i]];
470 
471  typid = colstat->attrtypid;
472  collid = colstat->attrcollid;
473 
474  type = lookup_type_cache(typid, TYPECACHE_LT_OPR);
475  if (type->lt_opr == InvalidOid) /* shouldn't happen */
476  elog(ERROR, "cache lookup failed for ordering operator for type %u",
477  typid);
478 
479  /* prepare the sort function for this dimension */
480  multi_sort_add_dimension(mss, i, type->lt_opr, collid);
481 
482  /* accumulate all the data for this dimension into the arrays */
483  for (j = 0; j < numrows; j++)
484  {
485  items[j].values[i] = data->values[combination[i]][j];
486  items[j].isnull[i] = data->nulls[combination[i]][j];
487  }
488  }
489 
490  /* We can sort the array now ... */
491  qsort_arg((void *) items, numrows, sizeof(SortItem),
492  multi_sort_compare, mss);
493 
494  /* ... and count the number of distinct combinations */
495 
496  f1 = 0;
497  cnt = 1;
498  d = 1;
499  for (i = 1; i < numrows; i++)
500  {
501  if (multi_sort_compare(&items[i], &items[i - 1], mss) != 0)
502  {
503  if (cnt == 1)
504  f1 += 1;
505 
506  d++;
507  cnt = 0;
508  }
509 
510  cnt += 1;
511  }
512 
513  if (cnt == 1)
514  f1 += 1;
515 
516  return estimate_ndistinct(totalrows, numrows, d, f1);
517 }
518 
519 /* The Duj1 estimator (already used in analyze.c). */
520 static double
521 estimate_ndistinct(double totalrows, int numrows, int d, int f1)
522 {
523  double numer,
524  denom,
525  ndistinct;
526 
527  numer = (double) numrows * (double) d;
528 
529  denom = (double) (numrows - f1) +
530  (double) f1 * (double) numrows / totalrows;
531 
532  ndistinct = numer / denom;
533 
534  /* Clamp to sane range in case of roundoff error */
535  if (ndistinct < (double) d)
536  ndistinct = (double) d;
537 
538  if (ndistinct > totalrows)
539  ndistinct = totalrows;
540 
541  return floor(ndistinct + 0.5);
542 }
543 
544 /*
545  * n_choose_k
546  * computes binomial coefficients using an algorithm that is both
547  * efficient and prevents overflows
548  */
549 static int
550 n_choose_k(int n, int k)
551 {
552  int d,
553  r;
554 
555  Assert((k > 0) && (n >= k));
556 
557  /* use symmetry of the binomial coefficients */
558  k = Min(k, n - k);
559 
560  r = 1;
561  for (d = 1; d <= k; ++d)
562  {
563  r *= n--;
564  r /= d;
565  }
566 
567  return r;
568 }
569 
570 /*
571  * num_combinations
572  * number of combinations, excluding single-value combinations
573  */
574 static int
576 {
577  return (1 << n) - (n + 1);
578 }
579 
580 /*
581  * generator_init
582  * initialize the generator of combinations
583  *
584  * The generator produces combinations of K elements in the interval (0..N).
585  * We prebuild all the combinations in this method, which is simpler than
586  * generating them on the fly.
587  */
588 static CombinationGenerator *
589 generator_init(int n, int k)
590 {
592 
593  Assert((n >= k) && (k > 0));
594 
595  /* allocate the generator state as a single chunk of memory */
596  state = (CombinationGenerator *) palloc(sizeof(CombinationGenerator));
597 
598  state->ncombinations = n_choose_k(n, k);
599 
600  /* pre-allocate space for all combinations */
601  state->combinations = (int *) palloc(sizeof(int) * k * state->ncombinations);
602 
603  state->current = 0;
604  state->k = k;
605  state->n = n;
606 
607  /* now actually pre-generate all the combinations of K elements */
608  generate_combinations(state);
609 
610  /* make sure we got the expected number of combinations */
611  Assert(state->current == state->ncombinations);
612 
613  /* reset the number, so we start with the first one */
614  state->current = 0;
615 
616  return state;
617 }
618 
619 /*
620  * generator_next
621  * returns the next combination from the prebuilt list
622  *
623  * Returns a combination of K array indexes (0 .. N), as specified to
624  * generator_init), or NULL when there are no more combination.
625  */
626 static int *
628 {
629  if (state->current == state->ncombinations)
630  return NULL;
631 
632  return &state->combinations[state->k * state->current++];
633 }
634 
635 /*
636  * generator_free
637  * free the internal state of the generator
638  *
639  * Releases the generator internal state (pre-built combinations).
640  */
641 static void
643 {
644  pfree(state->combinations);
645  pfree(state);
646 }
647 
648 /*
649  * generate_combinations_recurse
650  * given a prefix, generate all possible combinations
651  *
652  * Given a prefix (first few elements of the combination), generate following
653  * elements recursively. We generate the combinations in lexicographic order,
654  * which eliminates permutations of the same combination.
655  */
656 static void
658  int index, int start, int *current)
659 {
660  /* If we haven't filled all the elements, simply recurse. */
661  if (index < state->k)
662  {
663  int i;
664 
665  /*
666  * The values have to be in ascending order, so make sure we start
667  * with the value passed by parameter.
668  */
669 
670  for (i = start; i < state->n; i++)
671  {
672  current[index] = i;
673  generate_combinations_recurse(state, (index + 1), (i + 1), current);
674  }
675 
676  return;
677  }
678  else
679  {
680  /* we got a valid combination, add it to the array */
681  memcpy(&state->combinations[(state->k * state->current)],
682  current, state->k * sizeof(int));
683  state->current++;
684  }
685 }
686 
687 /*
688  * generate_combinations
689  * generate all k-combinations of N elements
690  */
691 static void
693 {
694  int *current = (int *) palloc0(sizeof(int) * state->k);
695 
696  generate_combinations_recurse(state, 0, 0, current);
697 
698  pfree(current);
699 }
#define MinSizeOfItems(nitems)
Definition: mvdistinct.c:56
#define VARDATA_ANY(PTR)
Definition: postgres.h:361
#define VARDATA(PTR)
Definition: postgres.h:315
Datum pg_ndistinct_in(PG_FUNCTION_ARGS)
Definition: mvdistinct.c:339
Datum pg_ndistinct_recv(PG_FUNCTION_ARGS)
Definition: mvdistinct.c:392
MVNDistinctItem items[FLEXIBLE_ARRAY_MEMBER]
Definition: statistics.h:39
MVNDistinct * statext_ndistinct_deserialize(bytea *data)
Definition: mvdistinct.c:250
static void output(uint64 loop_count)
#define VARHDRSZ
Definition: c.h:627
#define Min(x, y)
Definition: c.h:986
double ndistinct
Definition: statistics.h:28
static int * generator_next(CombinationGenerator *state)
Definition: mvdistinct.c:627
int errcode(int sqlerrcode)
Definition: elog.c:698
#define DatumGetByteaPP(X)
Definition: fmgr.h:291
int f1[ARRAY_SZIE]
Definition: sql-declare.c:113
struct CombinationGenerator CombinationGenerator
unsigned int Oid
Definition: postgres_ext.h:31
static double ndistinct_for_combination(double totalrows, StatsBuildData *data, int k, int *combination)
Definition: mvdistinct.c:425
Definition: type.h:89
#define STATS_NDISTINCT_TYPE_BASIC
Definition: statistics.h:23
static void generate_combinations(CombinationGenerator *state)
Definition: mvdistinct.c:692
void pfree(void *pointer)
Definition: mcxt.c:1169
void appendStringInfo(StringInfo str, const char *fmt,...)
Definition: stringinfo.c:91
Oid attrtypid
Definition: vacuum.h:124
#define ObjectIdGetDatum(X)
Definition: postgres.h:551
#define ERROR
Definition: elog.h:46
void multi_sort_add_dimension(MultiSortSupport mss, int sortdim, Oid oper, Oid collation)
static int n_choose_k(int n, int k)
Definition: mvdistinct.c:550
void appendStringInfoString(StringInfo str, const char *s)
Definition: stringinfo.c:176
#define SizeOfItem(natts)
Definition: mvdistinct.c:49
unsigned int uint32
Definition: c.h:441
uint32 nitems
Definition: statistics.h:38
MultiSortSupport multi_sort_init(int ndims)
void appendStringInfoChar(StringInfo str, char ch)
Definition: stringinfo.c:188
void initStringInfo(StringInfo str)
Definition: stringinfo.c:59
void qsort_arg(void *base, size_t nel, size_t elsize, qsort_arg_comparator cmp, void *arg)
Datum byteasend(PG_FUNCTION_ARGS)
Definition: varlena.c:500
uint32 magic
Definition: statistics.h:36
HeapTuple SearchSysCache1(int cacheId, Datum key1)
Definition: syscache.c:1127
#define AttributeNumberIsValid(attributeNumber)
Definition: attnum.h:34
static void generator_free(CombinationGenerator *state)
Definition: mvdistinct.c:642
static double estimate_ndistinct(double totalrows, int numrows, int d, int f1)
Definition: mvdistinct.c:521
void * palloc0(Size size)
Definition: mcxt.c:1093
uintptr_t Datum
Definition: postgres.h:411
void ReleaseSysCache(HeapTuple tuple)
Definition: syscache.c:1175
AttrNumber * attributes
Definition: statistics.h:30
Datum SysCacheGetAttr(int cacheId, HeapTuple tup, AttrNumber attributeNumber, bool *isNull)
Definition: syscache.c:1388
bytea * statext_ndistinct_serialize(MVNDistinct *ndistinct)
Definition: mvdistinct.c:179
Datum pg_ndistinct_send(PG_FUNCTION_ARGS)
Definition: mvdistinct.c:408
MVNDistinct * statext_ndistinct_build(double totalrows, StatsBuildData *data)
Definition: mvdistinct.c:89
VacAttrStats ** stats
#define VARSIZE_ANY(PTR)
Definition: postgres.h:348
TypeCacheEntry * lookup_type_cache(Oid type_id, int flags)
Definition: typcache.c:338
#define InvalidOid
Definition: postgres_ext.h:36
int16 attnum
Definition: pg_attribute.h:83
#define ereport(elevel,...)
Definition: elog.h:157
#define PG_RETURN_VOID()
Definition: fmgr.h:349
uint32 type
Definition: statistics.h:37
#define HeapTupleIsValid(tuple)
Definition: htup.h:78
#define SizeOfHeader
Definition: mvdistinct.c:46
#define Assert(condition)
Definition: c.h:804
Definition: regguts.h:317
int multi_sort_compare(const void *a, const void *b, void *arg)
#define PG_RETURN_CSTRING(x)
Definition: fmgr.h:362
size_t Size
Definition: c.h:540
#define STATS_NDISTINCT_MAGIC
Definition: statistics.h:22
#define PG_GETARG_BYTEA_PP(n)
Definition: fmgr.h:308
#define MAXALIGN(LEN)
Definition: c.h:757
Oid attrcollid
Definition: vacuum.h:127
static void generate_combinations_recurse(CombinationGenerator *state, int index, int start, int *current)
Definition: mvdistinct.c:657
static Datum values[MAXATTR]
Definition: bootstrap.c:166
#define STATS_MAX_DIMENSIONS
Definition: statistics.h:19
#define VARSIZE_ANY_EXHDR(PTR)
Definition: postgres.h:354
void * palloc(Size size)
Definition: mcxt.c:1062
int errmsg(const char *fmt,...)
Definition: elog.c:909
#define elog(elevel,...)
Definition: elog.h:232
int i
#define TYPECACHE_LT_OPR
Definition: typcache.h:137
Definition: c.h:621
#define PG_FUNCTION_ARGS
Definition: fmgr.h:193
#define SET_VARSIZE(PTR, len)
Definition: postgres.h:342
static int num_combinations(int n)
Definition: mvdistinct.c:575
MVNDistinct * statext_ndistinct_load(Oid mvoid)
Definition: mvdistinct.c:149
Datum pg_ndistinct_out(PG_FUNCTION_ARGS)
Definition: mvdistinct.c:355
int16 AttrNumber
Definition: attnum.h:21
static CombinationGenerator * generator_init(int n, int k)
Definition: mvdistinct.c:589
#define offsetof(type, field)
Definition: c.h:727