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indxpath.c
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1 /*-------------------------------------------------------------------------
2  *
3  * indxpath.c
4  * Routines to determine which indexes are usable for scanning a
5  * given relation, and create Paths accordingly.
6  *
7  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
8  * Portions Copyright (c) 1994, Regents of the University of California
9  *
10  *
11  * IDENTIFICATION
12  * src/backend/optimizer/path/indxpath.c
13  *
14  *-------------------------------------------------------------------------
15  */
16 #include "postgres.h"
17 
18 #include <math.h>
19 
20 #include "access/stratnum.h"
21 #include "access/sysattr.h"
22 #include "catalog/pg_am.h"
23 #include "catalog/pg_operator.h"
24 #include "catalog/pg_opfamily.h"
25 #include "catalog/pg_type.h"
26 #include "nodes/makefuncs.h"
27 #include "nodes/nodeFuncs.h"
28 #include "nodes/supportnodes.h"
29 #include "optimizer/cost.h"
30 #include "optimizer/optimizer.h"
31 #include "optimizer/pathnode.h"
32 #include "optimizer/paths.h"
33 #include "optimizer/prep.h"
34 #include "optimizer/restrictinfo.h"
35 #include "utils/lsyscache.h"
36 #include "utils/selfuncs.h"
37 
38 
39 /* XXX see PartCollMatchesExprColl */
40 #define IndexCollMatchesExprColl(idxcollation, exprcollation) \
41  ((idxcollation) == InvalidOid || (idxcollation) == (exprcollation))
42 
43 /* Whether we are looking for plain indexscan, bitmap scan, or either */
44 typedef enum
45 {
46  ST_INDEXSCAN, /* must support amgettuple */
47  ST_BITMAPSCAN, /* must support amgetbitmap */
48  ST_ANYSCAN /* either is okay */
49 } ScanTypeControl;
50 
51 /* Data structure for collecting qual clauses that match an index */
52 typedef struct
53 {
54  bool nonempty; /* True if lists are not all empty */
55  /* Lists of IndexClause nodes, one list per index column */
56  List *indexclauses[INDEX_MAX_KEYS];
57 } IndexClauseSet;
58 
59 /* Per-path data used within choose_bitmap_and() */
60 typedef struct
61 {
62  Path *path; /* IndexPath, BitmapAndPath, or BitmapOrPath */
63  List *quals; /* the WHERE clauses it uses */
64  List *preds; /* predicates of its partial index(es) */
65  Bitmapset *clauseids; /* quals+preds represented as a bitmapset */
66  bool unclassifiable; /* has too many quals+preds to process? */
67 } PathClauseUsage;
68 
69 /* Callback argument for ec_member_matches_indexcol */
70 typedef struct
71 {
72  IndexOptInfo *index; /* index we're considering */
73  int indexcol; /* index column we want to match to */
74 } ec_member_matches_arg;
75 
76 
77 static void consider_index_join_clauses(PlannerInfo *root, RelOptInfo *rel,
78  IndexOptInfo *index,
79  IndexClauseSet *rclauseset,
80  IndexClauseSet *jclauseset,
81  IndexClauseSet *eclauseset,
82  List **bitindexpaths);
83 static void consider_index_join_outer_rels(PlannerInfo *root, RelOptInfo *rel,
84  IndexOptInfo *index,
85  IndexClauseSet *rclauseset,
86  IndexClauseSet *jclauseset,
87  IndexClauseSet *eclauseset,
88  List **bitindexpaths,
89  List *indexjoinclauses,
90  int considered_clauses,
91  List **considered_relids);
92 static void get_join_index_paths(PlannerInfo *root, RelOptInfo *rel,
93  IndexOptInfo *index,
94  IndexClauseSet *rclauseset,
95  IndexClauseSet *jclauseset,
96  IndexClauseSet *eclauseset,
97  List **bitindexpaths,
98  Relids relids,
99  List **considered_relids);
100 static bool eclass_already_used(EquivalenceClass *parent_ec, Relids oldrelids,
101  List *indexjoinclauses);
102 static bool bms_equal_any(Relids relids, List *relids_list);
103 static void get_index_paths(PlannerInfo *root, RelOptInfo *rel,
104  IndexOptInfo *index, IndexClauseSet *clauses,
105  List **bitindexpaths);
106 static List *build_index_paths(PlannerInfo *root, RelOptInfo *rel,
107  IndexOptInfo *index, IndexClauseSet *clauses,
108  bool useful_predicate,
109  ScanTypeControl scantype,
110  bool *skip_nonnative_saop,
111  bool *skip_lower_saop);
112 static List *build_paths_for_OR(PlannerInfo *root, RelOptInfo *rel,
113  List *clauses, List *other_clauses);
114 static List *generate_bitmap_or_paths(PlannerInfo *root, RelOptInfo *rel,
115  List *clauses, List *other_clauses);
116 static Path *choose_bitmap_and(PlannerInfo *root, RelOptInfo *rel,
117  List *paths);
118 static int path_usage_comparator(const void *a, const void *b);
119 static Cost bitmap_scan_cost_est(PlannerInfo *root, RelOptInfo *rel,
120  Path *ipath);
121 static Cost bitmap_and_cost_est(PlannerInfo *root, RelOptInfo *rel,
122  List *paths);
123 static PathClauseUsage *classify_index_clause_usage(Path *path,
124  List **clauselist);
125 static void find_indexpath_quals(Path *bitmapqual, List **quals, List **preds);
126 static int find_list_position(Node *node, List **nodelist);
127 static bool check_index_only(RelOptInfo *rel, IndexOptInfo *index);
128 static double get_loop_count(PlannerInfo *root, Index cur_relid, Relids outer_relids);
129 static double adjust_rowcount_for_semijoins(PlannerInfo *root,
130  Index cur_relid,
131  Index outer_relid,
132  double rowcount);
133 static double approximate_joinrel_size(PlannerInfo *root, Relids relids);
134 static void match_restriction_clauses_to_index(PlannerInfo *root,
135  IndexOptInfo *index,
136  IndexClauseSet *clauseset);
137 static void match_join_clauses_to_index(PlannerInfo *root,
138  RelOptInfo *rel, IndexOptInfo *index,
139  IndexClauseSet *clauseset,
140  List **joinorclauses);
141 static void match_eclass_clauses_to_index(PlannerInfo *root,
142  IndexOptInfo *index,
143  IndexClauseSet *clauseset);
144 static void match_clauses_to_index(PlannerInfo *root,
145  List *clauses,
146  IndexOptInfo *index,
147  IndexClauseSet *clauseset);
148 static void match_clause_to_index(PlannerInfo *root,
149  RestrictInfo *rinfo,
150  IndexOptInfo *index,
151  IndexClauseSet *clauseset);
152 static IndexClause *match_clause_to_indexcol(PlannerInfo *root,
153  RestrictInfo *rinfo,
154  int indexcol,
155  IndexOptInfo *index);
156 static IndexClause *match_boolean_index_clause(PlannerInfo *root,
157  RestrictInfo *rinfo,
158  int indexcol, IndexOptInfo *index);
159 static IndexClause *match_opclause_to_indexcol(PlannerInfo *root,
160  RestrictInfo *rinfo,
161  int indexcol,
162  IndexOptInfo *index);
163 static IndexClause *match_funcclause_to_indexcol(PlannerInfo *root,
164  RestrictInfo *rinfo,
165  int indexcol,
166  IndexOptInfo *index);
167 static IndexClause *get_index_clause_from_support(PlannerInfo *root,
168  RestrictInfo *rinfo,
169  Oid funcid,
170  int indexarg,
171  int indexcol,
172  IndexOptInfo *index);
173 static IndexClause *match_saopclause_to_indexcol(PlannerInfo *root,
174  RestrictInfo *rinfo,
175  int indexcol,
176  IndexOptInfo *index);
177 static IndexClause *match_rowcompare_to_indexcol(PlannerInfo *root,
178  RestrictInfo *rinfo,
179  int indexcol,
180  IndexOptInfo *index);
181 static IndexClause *expand_indexqual_rowcompare(PlannerInfo *root,
182  RestrictInfo *rinfo,
183  int indexcol,
184  IndexOptInfo *index,
185  Oid expr_op,
186  bool var_on_left);
187 static void match_pathkeys_to_index(IndexOptInfo *index, List *pathkeys,
188  List **orderby_clauses_p,
189  List **clause_columns_p);
190 static Expr *match_clause_to_ordering_op(IndexOptInfo *index,
191  int indexcol, Expr *clause, Oid pk_opfamily);
192 static bool ec_member_matches_indexcol(PlannerInfo *root, RelOptInfo *rel,
193  EquivalenceClass *ec, EquivalenceMember *em,
194  void *arg);
195 
196 
197 /*
198  * create_index_paths()
199  * Generate all interesting index paths for the given relation.
200  * Candidate paths are added to the rel's pathlist (using add_path).
201  *
202  * To be considered for an index scan, an index must match one or more
203  * restriction clauses or join clauses from the query's qual condition,
204  * or match the query's ORDER BY condition, or have a predicate that
205  * matches the query's qual condition.
206  *
207  * There are two basic kinds of index scans. A "plain" index scan uses
208  * only restriction clauses (possibly none at all) in its indexqual,
209  * so it can be applied in any context. A "parameterized" index scan uses
210  * join clauses (plus restriction clauses, if available) in its indexqual.
211  * When joining such a scan to one of the relations supplying the other
212  * variables used in its indexqual, the parameterized scan must appear as
213  * the inner relation of a nestloop join; it can't be used on the outer side,
214  * nor in a merge or hash join. In that context, values for the other rels'
215  * attributes are available and fixed during any one scan of the indexpath.
216  *
217  * An IndexPath is generated and submitted to add_path() for each plain or
218  * parameterized index scan this routine deems potentially interesting for
219  * the current query.
220  *
221  * 'rel' is the relation for which we want to generate index paths
222  *
223  * Note: check_index_predicates() must have been run previously for this rel.
224  *
225  * Note: in cases involving LATERAL references in the relation's tlist, it's
226  * possible that rel->lateral_relids is nonempty. Currently, we include
227  * lateral_relids into the parameterization reported for each path, but don't
228  * take it into account otherwise. The fact that any such rels *must* be
229  * available as parameter sources perhaps should influence our choices of
230  * index quals ... but for now, it doesn't seem worth troubling over.
231  * In particular, comments below about "unparameterized" paths should be read
232  * as meaning "unparameterized so far as the indexquals are concerned".
233  */
234 void
235 create_index_paths(PlannerInfo *root, RelOptInfo *rel)
236 {
237  List *indexpaths;
238  List *bitindexpaths;
239  List *bitjoinpaths;
240  List *joinorclauses;
241  IndexClauseSet rclauseset;
242  IndexClauseSet jclauseset;
243  IndexClauseSet eclauseset;
244  ListCell *lc;
245 
246  /* Skip the whole mess if no indexes */
247  if (rel->indexlist == NIL)
248  return;
249 
250  /* Bitmap paths are collected and then dealt with at the end */
251  bitindexpaths = bitjoinpaths = joinorclauses = NIL;
252 
253  /* Examine each index in turn */
254  foreach(lc, rel->indexlist)
255  {
256  IndexOptInfo *index = (IndexOptInfo *) lfirst(lc);
257 
258  /* Protect limited-size array in IndexClauseSets */
259  Assert(index->nkeycolumns <= INDEX_MAX_KEYS);
260 
261  /*
262  * Ignore partial indexes that do not match the query.
263  * (generate_bitmap_or_paths() might be able to do something with
264  * them, but that's of no concern here.)
265  */
266  if (index->indpred != NIL && !index->predOK)
267  continue;
268 
269  /*
270  * Identify the restriction clauses that can match the index.
271  */
272  MemSet(&rclauseset, 0, sizeof(rclauseset));
273  match_restriction_clauses_to_index(root, index, &rclauseset);
274 
275  /*
276  * Build index paths from the restriction clauses. These will be
277  * non-parameterized paths. Plain paths go directly to add_path(),
278  * bitmap paths are added to bitindexpaths to be handled below.
279  */
280  get_index_paths(root, rel, index, &rclauseset,
281  &bitindexpaths);
282 
283  /*
284  * Identify the join clauses that can match the index. For the moment
285  * we keep them separate from the restriction clauses. Note that this
286  * step finds only "loose" join clauses that have not been merged into
287  * EquivalenceClasses. Also, collect join OR clauses for later.
288  */
289  MemSet(&jclauseset, 0, sizeof(jclauseset));
290  match_join_clauses_to_index(root, rel, index,
291  &jclauseset, &joinorclauses);
292 
293  /*
294  * Look for EquivalenceClasses that can generate joinclauses matching
295  * the index.
296  */
297  MemSet(&eclauseset, 0, sizeof(eclauseset));
298  match_eclass_clauses_to_index(root, index,
299  &eclauseset);
300 
301  /*
302  * If we found any plain or eclass join clauses, build parameterized
303  * index paths using them.
304  */
305  if (jclauseset.nonempty || eclauseset.nonempty)
306  consider_index_join_clauses(root, rel, index,
307  &rclauseset,
308  &jclauseset,
309  &eclauseset,
310  &bitjoinpaths);
311  }
312 
313  /*
314  * Generate BitmapOrPaths for any suitable OR-clauses present in the
315  * restriction list. Add these to bitindexpaths.
316  */
317  indexpaths = generate_bitmap_or_paths(root, rel,
318  rel->baserestrictinfo, NIL);
319  bitindexpaths = list_concat(bitindexpaths, indexpaths);
320 
321  /*
322  * Likewise, generate BitmapOrPaths for any suitable OR-clauses present in
323  * the joinclause list. Add these to bitjoinpaths.
324  */
325  indexpaths = generate_bitmap_or_paths(root, rel,
326  joinorclauses, rel->baserestrictinfo);
327  bitjoinpaths = list_concat(bitjoinpaths, indexpaths);
328 
329  /*
330  * If we found anything usable, generate a BitmapHeapPath for the most
331  * promising combination of restriction bitmap index paths. Note there
332  * will be only one such path no matter how many indexes exist. This
333  * should be sufficient since there's basically only one figure of merit
334  * (total cost) for such a path.
335  */
336  if (bitindexpaths != NIL)
337  {
338  Path *bitmapqual;
339  BitmapHeapPath *bpath;
340 
341  bitmapqual = choose_bitmap_and(root, rel, bitindexpaths);
342  bpath = create_bitmap_heap_path(root, rel, bitmapqual,
343  rel->lateral_relids, 1.0, 0);
344  add_path(rel, (Path *) bpath);
345 
346  /* create a partial bitmap heap path */
347  if (rel->consider_parallel && rel->lateral_relids == NULL)
348  create_partial_bitmap_paths(root, rel, bitmapqual);
349  }
350 
351  /*
352  * Likewise, if we found anything usable, generate BitmapHeapPaths for the
353  * most promising combinations of join bitmap index paths. Our strategy
354  * is to generate one such path for each distinct parameterization seen
355  * among the available bitmap index paths. This may look pretty
356  * expensive, but usually there won't be very many distinct
357  * parameterizations. (This logic is quite similar to that in
358  * consider_index_join_clauses, but we're working with whole paths not
359  * individual clauses.)
360  */
361  if (bitjoinpaths != NIL)
362  {
363  List *all_path_outers;
364  ListCell *lc;
365 
366  /* Identify each distinct parameterization seen in bitjoinpaths */
367  all_path_outers = NIL;
368  foreach(lc, bitjoinpaths)
369  {
370  Path *path = (Path *) lfirst(lc);
371  Relids required_outer = PATH_REQ_OUTER(path);
372 
373  if (!bms_equal_any(required_outer, all_path_outers))
374  all_path_outers = lappend(all_path_outers, required_outer);
375  }
376 
377  /* Now, for each distinct parameterization set ... */
378  foreach(lc, all_path_outers)
379  {
380  Relids max_outers = (Relids) lfirst(lc);
381  List *this_path_set;
382  Path *bitmapqual;
383  Relids required_outer;
384  double loop_count;
385  BitmapHeapPath *bpath;
386  ListCell *lcp;
387 
388  /* Identify all the bitmap join paths needing no more than that */
389  this_path_set = NIL;
390  foreach(lcp, bitjoinpaths)
391  {
392  Path *path = (Path *) lfirst(lcp);
393 
394  if (bms_is_subset(PATH_REQ_OUTER(path), max_outers))
395  this_path_set = lappend(this_path_set, path);
396  }
397 
398  /*
399  * Add in restriction bitmap paths, since they can be used
400  * together with any join paths.
401  */
402  this_path_set = list_concat(this_path_set, bitindexpaths);
403 
404  /* Select best AND combination for this parameterization */
405  bitmapqual = choose_bitmap_and(root, rel, this_path_set);
406 
407  /* And push that path into the mix */
408  required_outer = PATH_REQ_OUTER(bitmapqual);
409  loop_count = get_loop_count(root, rel->relid, required_outer);
410  bpath = create_bitmap_heap_path(root, rel, bitmapqual,
411  required_outer, loop_count, 0);
412  add_path(rel, (Path *) bpath);
413  }
414  }
415 }
416 
417 /*
418  * consider_index_join_clauses
419  * Given sets of join clauses for an index, decide which parameterized
420  * index paths to build.
421  *
422  * Plain indexpaths are sent directly to add_path, while potential
423  * bitmap indexpaths are added to *bitindexpaths for later processing.
424  *
425  * 'rel' is the index's heap relation
426  * 'index' is the index for which we want to generate paths
427  * 'rclauseset' is the collection of indexable restriction clauses
428  * 'jclauseset' is the collection of indexable simple join clauses
429  * 'eclauseset' is the collection of indexable clauses from EquivalenceClasses
430  * '*bitindexpaths' is the list to add bitmap paths to
431  */
432 static void
433 consider_index_join_clauses(PlannerInfo *root, RelOptInfo *rel,
434  IndexOptInfo *index,
435  IndexClauseSet *rclauseset,
436  IndexClauseSet *jclauseset,
437  IndexClauseSet *eclauseset,
438  List **bitindexpaths)
439 {
440  int considered_clauses = 0;
441  List *considered_relids = NIL;
442  int indexcol;
443 
444  /*
445  * The strategy here is to identify every potentially useful set of outer
446  * rels that can provide indexable join clauses. For each such set,
447  * select all the join clauses available from those outer rels, add on all
448  * the indexable restriction clauses, and generate plain and/or bitmap
449  * index paths for that set of clauses. This is based on the assumption
450  * that it's always better to apply a clause as an indexqual than as a
451  * filter (qpqual); which is where an available clause would end up being
452  * applied if we omit it from the indexquals.
453  *
454  * This looks expensive, but in most practical cases there won't be very
455  * many distinct sets of outer rels to consider. As a safety valve when
456  * that's not true, we use a heuristic: limit the number of outer rel sets
457  * considered to a multiple of the number of clauses considered. (We'll
458  * always consider using each individual join clause, though.)
459  *
460  * For simplicity in selecting relevant clauses, we represent each set of
461  * outer rels as a maximum set of clause_relids --- that is, the indexed
462  * relation itself is also included in the relids set. considered_relids
463  * lists all relids sets we've already tried.
464  */
465  for (indexcol = 0; indexcol < index->nkeycolumns; indexcol++)
466  {
467  /* Consider each applicable simple join clause */
468  considered_clauses += list_length(jclauseset->indexclauses[indexcol]);
469  consider_index_join_outer_rels(root, rel, index,
470  rclauseset, jclauseset, eclauseset,
471  bitindexpaths,
472  jclauseset->indexclauses[indexcol],
473  considered_clauses,
474  &considered_relids);
475  /* Consider each applicable eclass join clause */
476  considered_clauses += list_length(eclauseset->indexclauses[indexcol]);
477  consider_index_join_outer_rels(root, rel, index,
478  rclauseset, jclauseset, eclauseset,
479  bitindexpaths,
480  eclauseset->indexclauses[indexcol],
481  considered_clauses,
482  &considered_relids);
483  }
484 }
485 
486 /*
487  * consider_index_join_outer_rels
488  * Generate parameterized paths based on clause relids in the clause list.
489  *
490  * Workhorse for consider_index_join_clauses; see notes therein for rationale.
491  *
492  * 'rel', 'index', 'rclauseset', 'jclauseset', 'eclauseset', and
493  * 'bitindexpaths' as above
494  * 'indexjoinclauses' is a list of IndexClauses for join clauses
495  * 'considered_clauses' is the total number of clauses considered (so far)
496  * '*considered_relids' is a list of all relids sets already considered
497  */
498 static void
499 consider_index_join_outer_rels(PlannerInfo *root, RelOptInfo *rel,
500  IndexOptInfo *index,
501  IndexClauseSet *rclauseset,
502  IndexClauseSet *jclauseset,
503  IndexClauseSet *eclauseset,
504  List **bitindexpaths,
505  List *indexjoinclauses,
506  int considered_clauses,
507  List **considered_relids)
508 {
509  ListCell *lc;
510 
511  /* Examine relids of each joinclause in the given list */
512  foreach(lc, indexjoinclauses)
513  {
514  IndexClause *iclause = (IndexClause *) lfirst(lc);
515  Relids clause_relids = iclause->rinfo->clause_relids;
516  EquivalenceClass *parent_ec = iclause->rinfo->parent_ec;
517  int num_considered_relids;
518 
519  /* If we already tried its relids set, no need to do so again */
520  if (bms_equal_any(clause_relids, *considered_relids))
521  continue;
522 
523  /*
524  * Generate the union of this clause's relids set with each
525  * previously-tried set. This ensures we try this clause along with
526  * every interesting subset of previous clauses. However, to avoid
527  * exponential growth of planning time when there are many clauses,
528  * limit the number of relid sets accepted to 10 * considered_clauses.
529  *
530  * Note: get_join_index_paths appends entries to *considered_relids,
531  * but we do not need to visit such newly-added entries within this
532  * loop, so we don't use foreach() here. No real harm would be done
533  * if we did visit them, since the subset check would reject them; but
534  * it would waste some cycles.
535  */
536  num_considered_relids = list_length(*considered_relids);
537  for (int pos = 0; pos < num_considered_relids; pos++)
538  {
539  Relids oldrelids = (Relids) list_nth(*considered_relids, pos);
540 
541  /*
542  * If either is a subset of the other, no new set is possible.
543  * This isn't a complete test for redundancy, but it's easy and
544  * cheap. get_join_index_paths will check more carefully if we
545  * already generated the same relids set.
546  */
547  if (bms_subset_compare(clause_relids, oldrelids) != BMS_DIFFERENT)
548  continue;
549 
550  /*
551  * If this clause was derived from an equivalence class, the
552  * clause list may contain other clauses derived from the same
553  * eclass. We should not consider that combining this clause with
554  * one of those clauses generates a usefully different
555  * parameterization; so skip if any clause derived from the same
556  * eclass would already have been included when using oldrelids.
557  */
558  if (parent_ec &&
559  eclass_already_used(parent_ec, oldrelids,
560  indexjoinclauses))
561  continue;
562 
563  /*
564  * If the number of relid sets considered exceeds our heuristic
565  * limit, stop considering combinations of clauses. We'll still
566  * consider the current clause alone, though (below this loop).
567  */
568  if (list_length(*considered_relids) >= 10 * considered_clauses)
569  break;
570 
571  /* OK, try the union set */
572  get_join_index_paths(root, rel, index,
573  rclauseset, jclauseset, eclauseset,
574  bitindexpaths,
575  bms_union(clause_relids, oldrelids),
576  considered_relids);
577  }
578 
579  /* Also try this set of relids by itself */
580  get_join_index_paths(root, rel, index,
581  rclauseset, jclauseset, eclauseset,
582  bitindexpaths,
583  clause_relids,
584  considered_relids);
585  }
586 }
587 
588 /*
589  * get_join_index_paths
590  * Generate index paths using clauses from the specified outer relations.
591  * In addition to generating paths, relids is added to *considered_relids
592  * if not already present.
593  *
594  * Workhorse for consider_index_join_clauses; see notes therein for rationale.
595  *
596  * 'rel', 'index', 'rclauseset', 'jclauseset', 'eclauseset',
597  * 'bitindexpaths', 'considered_relids' as above
598  * 'relids' is the current set of relids to consider (the target rel plus
599  * one or more outer rels)
600  */
601 static void
602 get_join_index_paths(PlannerInfo *root, RelOptInfo *rel,
603  IndexOptInfo *index,
604  IndexClauseSet *rclauseset,
605  IndexClauseSet *jclauseset,
606  IndexClauseSet *eclauseset,
607  List **bitindexpaths,
608  Relids relids,
609  List **considered_relids)
610 {
611  IndexClauseSet clauseset;
612  int indexcol;
613 
614  /* If we already considered this relids set, don't repeat the work */
615  if (bms_equal_any(relids, *considered_relids))
616  return;
617 
618  /* Identify indexclauses usable with this relids set */
619  MemSet(&clauseset, 0, sizeof(clauseset));
620 
621  for (indexcol = 0; indexcol < index->nkeycolumns; indexcol++)
622  {
623  ListCell *lc;
624 
625  /* First find applicable simple join clauses */
626  foreach(lc, jclauseset->indexclauses[indexcol])
627  {
628  IndexClause *iclause = (IndexClause *) lfirst(lc);
629 
630  if (bms_is_subset(iclause->rinfo->clause_relids, relids))
631  clauseset.indexclauses[indexcol] =
632  lappend(clauseset.indexclauses[indexcol], iclause);
633  }
634 
635  /*
636  * Add applicable eclass join clauses. The clauses generated for each
637  * column are redundant (cf generate_implied_equalities_for_column),
638  * so we need at most one. This is the only exception to the general
639  * rule of using all available index clauses.
640  */
641  foreach(lc, eclauseset->indexclauses[indexcol])
642  {
643  IndexClause *iclause = (IndexClause *) lfirst(lc);
644 
645  if (bms_is_subset(iclause->rinfo->clause_relids, relids))
646  {
647  clauseset.indexclauses[indexcol] =
648  lappend(clauseset.indexclauses[indexcol], iclause);
649  break;
650  }
651  }
652 
653  /* Add restriction clauses */
654  clauseset.indexclauses[indexcol] =
655  list_concat(clauseset.indexclauses[indexcol],
656  rclauseset->indexclauses[indexcol]);
657 
658  if (clauseset.indexclauses[indexcol] != NIL)
659  clauseset.nonempty = true;
660  }
661 
662  /* We should have found something, else caller passed silly relids */
663  Assert(clauseset.nonempty);
664 
665  /* Build index path(s) using the collected set of clauses */
666  get_index_paths(root, rel, index, &clauseset, bitindexpaths);
667 
668  /*
669  * Remember we considered paths for this set of relids.
670  */
671  *considered_relids = lappend(*considered_relids, relids);
672 }
673 
674 /*
675  * eclass_already_used
676  * True if any join clause usable with oldrelids was generated from
677  * the specified equivalence class.
678  */
679 static bool
680 eclass_already_used(EquivalenceClass *parent_ec, Relids oldrelids,
681  List *indexjoinclauses)
682 {
683  ListCell *lc;
684 
685  foreach(lc, indexjoinclauses)
686  {
687  IndexClause *iclause = (IndexClause *) lfirst(lc);
688  RestrictInfo *rinfo = iclause->rinfo;
689 
690  if (rinfo->parent_ec == parent_ec &&
691  bms_is_subset(rinfo->clause_relids, oldrelids))
692  return true;
693  }
694  return false;
695 }
696 
697 /*
698  * bms_equal_any
699  * True if relids is bms_equal to any member of relids_list
700  *
701  * Perhaps this should be in bitmapset.c someday.
702  */
703 static bool
704 bms_equal_any(Relids relids, List *relids_list)
705 {
706  ListCell *lc;
707 
708  foreach(lc, relids_list)
709  {
710  if (bms_equal(relids, (Relids) lfirst(lc)))
711  return true;
712  }
713  return false;
714 }
715 
716 
717 /*
718  * get_index_paths
719  * Given an index and a set of index clauses for it, construct IndexPaths.
720  *
721  * Plain indexpaths are sent directly to add_path, while potential
722  * bitmap indexpaths are added to *bitindexpaths for later processing.
723  *
724  * This is a fairly simple frontend to build_index_paths(). Its reason for
725  * existence is mainly to handle ScalarArrayOpExpr quals properly. If the
726  * index AM supports them natively, we should just include them in simple
727  * index paths. If not, we should exclude them while building simple index
728  * paths, and then make a separate attempt to include them in bitmap paths.
729  * Furthermore, we should consider excluding lower-order ScalarArrayOpExpr
730  * quals so as to create ordered paths.
731  */
732 static void
733 get_index_paths(PlannerInfo *root, RelOptInfo *rel,
734  IndexOptInfo *index, IndexClauseSet *clauses,
735  List **bitindexpaths)
736 {
737  List *indexpaths;
738  bool skip_nonnative_saop = false;
739  bool skip_lower_saop = false;
740  ListCell *lc;
741 
742  /*
743  * Build simple index paths using the clauses. Allow ScalarArrayOpExpr
744  * clauses only if the index AM supports them natively, and skip any such
745  * clauses for index columns after the first (so that we produce ordered
746  * paths if possible).
747  */
748  indexpaths = build_index_paths(root, rel,
749  index, clauses,
750  index->predOK,
751  ST_ANYSCAN,
752  &skip_nonnative_saop,
753  &skip_lower_saop);
754 
755  /*
756  * If we skipped any lower-order ScalarArrayOpExprs on an index with an AM
757  * that supports them, then try again including those clauses. This will
758  * produce paths with more selectivity but no ordering.
759  */
760  if (skip_lower_saop)
761  {
762  indexpaths = list_concat(indexpaths,
763  build_index_paths(root, rel,
764  index, clauses,
765  index->predOK,
766  ST_ANYSCAN,
767  &skip_nonnative_saop,
768  NULL));
769  }
770 
771  /*
772  * Submit all the ones that can form plain IndexScan plans to add_path. (A
773  * plain IndexPath can represent either a plain IndexScan or an
774  * IndexOnlyScan, but for our purposes here that distinction does not
775  * matter. However, some of the indexes might support only bitmap scans,
776  * and those we mustn't submit to add_path here.)
777  *
778  * Also, pick out the ones that are usable as bitmap scans. For that, we
779  * must discard indexes that don't support bitmap scans, and we also are
780  * only interested in paths that have some selectivity; we should discard
781  * anything that was generated solely for ordering purposes.
782  */
783  foreach(lc, indexpaths)
784  {
785  IndexPath *ipath = (IndexPath *) lfirst(lc);
786 
787  if (index->amhasgettuple)
788  add_path(rel, (Path *) ipath);
789 
790  if (index->amhasgetbitmap &&
791  (ipath->path.pathkeys == NIL ||
792  ipath->indexselectivity < 1.0))
793  *bitindexpaths = lappend(*bitindexpaths, ipath);
794  }
795 
796  /*
797  * If there were ScalarArrayOpExpr clauses that the index can't handle
798  * natively, generate bitmap scan paths relying on executor-managed
799  * ScalarArrayOpExpr.
800  */
801  if (skip_nonnative_saop)
802  {
803  indexpaths = build_index_paths(root, rel,
804  index, clauses,
805  false,
806  ST_BITMAPSCAN,
807  NULL,
808  NULL);
809  *bitindexpaths = list_concat(*bitindexpaths, indexpaths);
810  }
811 }
812 
813 /*
814  * build_index_paths
815  * Given an index and a set of index clauses for it, construct zero
816  * or more IndexPaths. It also constructs zero or more partial IndexPaths.
817  *
818  * We return a list of paths because (1) this routine checks some cases
819  * that should cause us to not generate any IndexPath, and (2) in some
820  * cases we want to consider both a forward and a backward scan, so as
821  * to obtain both sort orders. Note that the paths are just returned
822  * to the caller and not immediately fed to add_path().
823  *
824  * At top level, useful_predicate should be exactly the index's predOK flag
825  * (ie, true if it has a predicate that was proven from the restriction
826  * clauses). When working on an arm of an OR clause, useful_predicate
827  * should be true if the predicate required the current OR list to be proven.
828  * Note that this routine should never be called at all if the index has an
829  * unprovable predicate.
830  *
831  * scantype indicates whether we want to create plain indexscans, bitmap
832  * indexscans, or both. When it's ST_BITMAPSCAN, we will not consider
833  * index ordering while deciding if a Path is worth generating.
834  *
835  * If skip_nonnative_saop is non-NULL, we ignore ScalarArrayOpExpr clauses
836  * unless the index AM supports them directly, and we set *skip_nonnative_saop
837  * to true if we found any such clauses (caller must initialize the variable
838  * to false). If it's NULL, we do not ignore ScalarArrayOpExpr clauses.
839  *
840  * If skip_lower_saop is non-NULL, we ignore ScalarArrayOpExpr clauses for
841  * non-first index columns, and we set *skip_lower_saop to true if we found
842  * any such clauses (caller must initialize the variable to false). If it's
843  * NULL, we do not ignore non-first ScalarArrayOpExpr clauses, but they will
844  * result in considering the scan's output to be unordered.
845  *
846  * 'rel' is the index's heap relation
847  * 'index' is the index for which we want to generate paths
848  * 'clauses' is the collection of indexable clauses (IndexClause nodes)
849  * 'useful_predicate' indicates whether the index has a useful predicate
850  * 'scantype' indicates whether we need plain or bitmap scan support
851  * 'skip_nonnative_saop' indicates whether to accept SAOP if index AM doesn't
852  * 'skip_lower_saop' indicates whether to accept non-first-column SAOP
853  */
854 static List *
855 build_index_paths(PlannerInfo *root, RelOptInfo *rel,
856  IndexOptInfo *index, IndexClauseSet *clauses,
857  bool useful_predicate,
858  ScanTypeControl scantype,
859  bool *skip_nonnative_saop,
860  bool *skip_lower_saop)
861 {
862  List *result = NIL;
863  IndexPath *ipath;
864  List *index_clauses;
865  Relids outer_relids;
866  double loop_count;
867  List *orderbyclauses;
868  List *orderbyclausecols;
869  List *index_pathkeys;
870  List *useful_pathkeys;
871  bool found_lower_saop_clause;
872  bool pathkeys_possibly_useful;
873  bool index_is_ordered;
874  bool index_only_scan;
875  int indexcol;
876 
877  /*
878  * Check that index supports the desired scan type(s)
879  */
880  switch (scantype)
881  {
882  case ST_INDEXSCAN:
883  if (!index->amhasgettuple)
884  return NIL;
885  break;
886  case ST_BITMAPSCAN:
887  if (!index->amhasgetbitmap)
888  return NIL;
889  break;
890  case ST_ANYSCAN:
891  /* either or both are OK */
892  break;
893  }
894 
895  /*
896  * 1. Combine the per-column IndexClause lists into an overall list.
897  *
898  * In the resulting list, clauses are ordered by index key, so that the
899  * column numbers form a nondecreasing sequence. (This order is depended
900  * on by btree and possibly other places.) The list can be empty, if the
901  * index AM allows that.
902  *
903  * found_lower_saop_clause is set true if we accept a ScalarArrayOpExpr
904  * index clause for a non-first index column. This prevents us from
905  * assuming that the scan result is ordered. (Actually, the result is
906  * still ordered if there are equality constraints for all earlier
907  * columns, but it seems too expensive and non-modular for this code to be
908  * aware of that refinement.)
909  *
910  * We also build a Relids set showing which outer rels are required by the
911  * selected clauses. Any lateral_relids are included in that, but not
912  * otherwise accounted for.
913  */
914  index_clauses = NIL;
915  found_lower_saop_clause = false;
916  outer_relids = bms_copy(rel->lateral_relids);
917  for (indexcol = 0; indexcol < index->nkeycolumns; indexcol++)
918  {
919  ListCell *lc;
920 
921  foreach(lc, clauses->indexclauses[indexcol])
922  {
923  IndexClause *iclause = (IndexClause *) lfirst(lc);
924  RestrictInfo *rinfo = iclause->rinfo;
925 
926  /* We might need to omit ScalarArrayOpExpr clauses */
927  if (IsA(rinfo->clause, ScalarArrayOpExpr))
928  {
929  if (!index->amsearcharray)
930  {
931  if (skip_nonnative_saop)
932  {
933  /* Ignore because not supported by index */
934  *skip_nonnative_saop = true;
935  continue;
936  }
937  /* Caller had better intend this only for bitmap scan */
938  Assert(scantype == ST_BITMAPSCAN);
939  }
940  if (indexcol > 0)
941  {
942  if (skip_lower_saop)
943  {
944  /* Caller doesn't want to lose index ordering */
945  *skip_lower_saop = true;
946  continue;
947  }
948  found_lower_saop_clause = true;
949  }
950  }
951 
952  /* OK to include this clause */
953  index_clauses = lappend(index_clauses, iclause);
954  outer_relids = bms_add_members(outer_relids,
955  rinfo->clause_relids);
956  }
957 
958  /*
959  * If no clauses match the first index column, check for amoptionalkey
960  * restriction. We can't generate a scan over an index with
961  * amoptionalkey = false unless there's at least one index clause.
962  * (When working on columns after the first, this test cannot fail. It
963  * is always okay for columns after the first to not have any
964  * clauses.)
965  */
966  if (index_clauses == NIL && !index->amoptionalkey)
967  return NIL;
968  }
969 
970  /* We do not want the index's rel itself listed in outer_relids */
971  outer_relids = bms_del_member(outer_relids, rel->relid);
972  /* Enforce convention that outer_relids is exactly NULL if empty */
973  if (bms_is_empty(outer_relids))
974  outer_relids = NULL;
975 
976  /* Compute loop_count for cost estimation purposes */
977  loop_count = get_loop_count(root, rel->relid, outer_relids);
978 
979  /*
980  * 2. Compute pathkeys describing index's ordering, if any, then see how
981  * many of them are actually useful for this query. This is not relevant
982  * if we are only trying to build bitmap indexscans, nor if we have to
983  * assume the scan is unordered.
984  */
985  pathkeys_possibly_useful = (scantype != ST_BITMAPSCAN &&
986  !found_lower_saop_clause &&
987  has_useful_pathkeys(root, rel));
988  index_is_ordered = (index->sortopfamily != NULL);
989  if (index_is_ordered && pathkeys_possibly_useful)
990  {
991  index_pathkeys = build_index_pathkeys(root, index,
992  ForwardScanDirection);
993  useful_pathkeys = truncate_useless_pathkeys(root, rel,
994  index_pathkeys);
995  orderbyclauses = NIL;
996  orderbyclausecols = NIL;
997  }
998  else if (index->amcanorderbyop && pathkeys_possibly_useful)
999  {
1000  /* see if we can generate ordering operators for query_pathkeys */
1001  match_pathkeys_to_index(index, root->query_pathkeys,
1002  &orderbyclauses,
1003  &orderbyclausecols);
1004  if (orderbyclauses)
1005  useful_pathkeys = root->query_pathkeys;
1006  else
1007  useful_pathkeys = NIL;
1008  }
1009  else
1010  {
1011  useful_pathkeys = NIL;
1012  orderbyclauses = NIL;
1013  orderbyclausecols = NIL;
1014  }
1015 
1016  /*
1017  * 3. Check if an index-only scan is possible. If we're not building
1018  * plain indexscans, this isn't relevant since bitmap scans don't support
1019  * index data retrieval anyway.
1020  */
1021  index_only_scan = (scantype != ST_BITMAPSCAN &&
1022  check_index_only(rel, index));
1023 
1024  /*
1025  * 4. Generate an indexscan path if there are relevant restriction clauses
1026  * in the current clauses, OR the index ordering is potentially useful for
1027  * later merging or final output ordering, OR the index has a useful
1028  * predicate, OR an index-only scan is possible.
1029  */
1030  if (index_clauses != NIL || useful_pathkeys != NIL || useful_predicate ||
1031  index_only_scan)
1032  {
1033  ipath = create_index_path(root, index,
1034  index_clauses,
1035  orderbyclauses,
1036  orderbyclausecols,
1037  useful_pathkeys,
1038  index_is_ordered ?
1039  ForwardScanDirection :
1040  NoMovementScanDirection,
1041  index_only_scan,
1042  outer_relids,
1043  loop_count,
1044  false);
1045  result = lappend(result, ipath);
1046 
1047  /*
1048  * If appropriate, consider parallel index scan. We don't allow
1049  * parallel index scan for bitmap index scans.
1050  */
1051  if (index->amcanparallel &&
1052  rel->consider_parallel && outer_relids == NULL &&
1053  scantype != ST_BITMAPSCAN)
1054  {
1055  ipath = create_index_path(root, index,
1056  index_clauses,
1057  orderbyclauses,
1058  orderbyclausecols,
1059  useful_pathkeys,
1060  index_is_ordered ?
1061  ForwardScanDirection :
1062  NoMovementScanDirection,
1063  index_only_scan,
1064  outer_relids,
1065  loop_count,
1066  true);
1067 
1068  /*
1069  * if, after costing the path, we find that it's not worth using
1070  * parallel workers, just free it.
1071  */
1072  if (ipath->path.parallel_workers > 0)
1073  add_partial_path(rel, (Path *) ipath);
1074  else
1075  pfree(ipath);
1076  }
1077  }
1078 
1079  /*
1080  * 5. If the index is ordered, a backwards scan might be interesting.
1081  */
1082  if (index_is_ordered && pathkeys_possibly_useful)
1083  {
1084  index_pathkeys = build_index_pathkeys(root, index,
1085  BackwardScanDirection);
1086  useful_pathkeys = truncate_useless_pathkeys(root, rel,
1087  index_pathkeys);
1088  if (useful_pathkeys != NIL)
1089  {
1090  ipath = create_index_path(root, index,
1091  index_clauses,
1092  NIL,
1093  NIL,
1094  useful_pathkeys,
1095  BackwardScanDirection,
1096  index_only_scan,
1097  outer_relids,
1098  loop_count,
1099  false);
1100  result = lappend(result, ipath);
1101 
1102  /* If appropriate, consider parallel index scan */
1103  if (index->amcanparallel &&
1104  rel->consider_parallel && outer_relids == NULL &&
1105  scantype != ST_BITMAPSCAN)
1106  {
1107  ipath = create_index_path(root, index,
1108  index_clauses,
1109  NIL,
1110  NIL,
1111  useful_pathkeys,
1112  BackwardScanDirection,
1113  index_only_scan,
1114  outer_relids,
1115  loop_count,
1116  true);
1117 
1118  /*
1119  * if, after costing the path, we find that it's not worth
1120  * using parallel workers, just free it.
1121  */
1122  if (ipath->path.parallel_workers > 0)
1123  add_partial_path(rel, (Path *) ipath);
1124  else
1125  pfree(ipath);
1126  }
1127  }
1128  }
1129 
1130  return result;
1131 }
1132 
1133 /*
1134  * build_paths_for_OR
1135  * Given a list of restriction clauses from one arm of an OR clause,
1136  * construct all matching IndexPaths for the relation.
1137  *
1138  * Here we must scan all indexes of the relation, since a bitmap OR tree
1139  * can use multiple indexes.
1140  *
1141  * The caller actually supplies two lists of restriction clauses: some
1142  * "current" ones and some "other" ones. Both lists can be used freely
1143  * to match keys of the index, but an index must use at least one of the
1144  * "current" clauses to be considered usable. The motivation for this is
1145  * examples like
1146  * WHERE (x = 42) AND (... OR (y = 52 AND z = 77) OR ....)
1147  * While we are considering the y/z subclause of the OR, we can use "x = 42"
1148  * as one of the available index conditions; but we shouldn't match the
1149  * subclause to any index on x alone, because such a Path would already have
1150  * been generated at the upper level. So we could use an index on x,y,z
1151  * or an index on x,y for the OR subclause, but not an index on just x.
1152  * When dealing with a partial index, a match of the index predicate to
1153  * one of the "current" clauses also makes the index usable.
1154  *
1155  * 'rel' is the relation for which we want to generate index paths
1156  * 'clauses' is the current list of clauses (RestrictInfo nodes)
1157  * 'other_clauses' is the list of additional upper-level clauses
1158  */
1159 static List *
1160 build_paths_for_OR(PlannerInfo *root, RelOptInfo *rel,
1161  List *clauses, List *other_clauses)
1162 {
1163  List *result = NIL;
1164  List *all_clauses = NIL; /* not computed till needed */
1165  ListCell *lc;
1166 
1167  foreach(lc, rel->indexlist)
1168  {
1169  IndexOptInfo *index = (IndexOptInfo *) lfirst(lc);
1170  IndexClauseSet clauseset;
1171  List *indexpaths;
1172  bool useful_predicate;
1173 
1174  /* Ignore index if it doesn't support bitmap scans */
1175  if (!index->amhasgetbitmap)
1176  continue;
1177 
1178  /*
1179  * Ignore partial indexes that do not match the query. If a partial
1180  * index is marked predOK then we know it's OK. Otherwise, we have to
1181  * test whether the added clauses are sufficient to imply the
1182  * predicate. If so, we can use the index in the current context.
1183  *
1184  * We set useful_predicate to true iff the predicate was proven using
1185  * the current set of clauses. This is needed to prevent matching a
1186  * predOK index to an arm of an OR, which would be a legal but
1187  * pointlessly inefficient plan. (A better plan will be generated by
1188  * just scanning the predOK index alone, no OR.)
1189  */
1190  useful_predicate = false;
1191  if (index->indpred != NIL)
1192  {
1193  if (index->predOK)
1194  {
1195  /* Usable, but don't set useful_predicate */
1196  }
1197  else
1198  {
1199  /* Form all_clauses if not done already */
1200  if (all_clauses == NIL)
1201  all_clauses = list_concat_copy(clauses, other_clauses);
1202 
1203  if (!predicate_implied_by(index->indpred, all_clauses, false))
1204  continue; /* can't use it at all */
1205 
1206  if (!predicate_implied_by(index->indpred, other_clauses, false))
1207  useful_predicate = true;
1208  }
1209  }
1210 
1211  /*
1212  * Identify the restriction clauses that can match the index.
1213  */
1214  MemSet(&clauseset, 0, sizeof(clauseset));
1215  match_clauses_to_index(root, clauses, index, &clauseset);
1216 
1217  /*
1218  * If no matches so far, and the index predicate isn't useful, we
1219  * don't want it.
1220  */
1221  if (!clauseset.nonempty && !useful_predicate)
1222  continue;
1223 
1224  /*
1225  * Add "other" restriction clauses to the clauseset.
1226  */
1227  match_clauses_to_index(root, other_clauses, index, &clauseset);
1228 
1229  /*
1230  * Construct paths if possible.
1231  */
1232  indexpaths = build_index_paths(root, rel,
1233  index, &clauseset,
1234  useful_predicate,
1235  ST_BITMAPSCAN,
1236  NULL,
1237  NULL);
1238  result = list_concat(result, indexpaths);
1239  }
1240 
1241  return result;
1242 }
1243 
1244 /*
1245  * generate_bitmap_or_paths
1246  * Look through the list of clauses to find OR clauses, and generate
1247  * a BitmapOrPath for each one we can handle that way. Return a list
1248  * of the generated BitmapOrPaths.
1249  *
1250  * other_clauses is a list of additional clauses that can be assumed true
1251  * for the purpose of generating indexquals, but are not to be searched for
1252  * ORs. (See build_paths_for_OR() for motivation.)
1253  */
1254 static List *
1255 generate_bitmap_or_paths(PlannerInfo *root, RelOptInfo *rel,
1256  List *clauses, List *other_clauses)
1257 {
1258  List *result = NIL;
1259  List *all_clauses;
1260  ListCell *lc;
1261 
1262  /*
1263  * We can use both the current and other clauses as context for
1264  * build_paths_for_OR; no need to remove ORs from the lists.
1265  */
1266  all_clauses = list_concat_copy(clauses, other_clauses);
1267 
1268  foreach(lc, clauses)
1269  {
1270  RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
1271  List *pathlist;
1272  Path *bitmapqual;
1273  ListCell *j;
1274 
1275  /* Ignore RestrictInfos that aren't ORs */
1276  if (!restriction_is_or_clause(rinfo))
1277  continue;
1278 
1279  /*
1280  * We must be able to match at least one index to each of the arms of
1281  * the OR, else we can't use it.
1282  */
1283  pathlist = NIL;
1284  foreach(j, ((BoolExpr *) rinfo->orclause)->args)
1285  {
1286  Node *orarg = (Node *) lfirst(j);
1287  List *indlist;
1288 
1289  /* OR arguments should be ANDs or sub-RestrictInfos */
1290  if (is_andclause(orarg))
1291  {
1292  List *andargs = ((BoolExpr *) orarg)->args;
1293 
1294  indlist = build_paths_for_OR(root, rel,
1295  andargs,
1296  all_clauses);
1297 
1298  /* Recurse in case there are sub-ORs */
1299  indlist = list_concat(indlist,
1300  generate_bitmap_or_paths(root, rel,
1301  andargs,
1302  all_clauses));
1303  }
1304  else
1305  {
1306  RestrictInfo *rinfo = castNode(RestrictInfo, orarg);
1307  List *orargs;
1308 
1309  Assert(!restriction_is_or_clause(rinfo));
1310  orargs = list_make1(rinfo);
1311 
1312  indlist = build_paths_for_OR(root, rel,
1313  orargs,
1314  all_clauses);
1315  }
1316 
1317  /*
1318  * If nothing matched this arm, we can't do anything with this OR
1319  * clause.
1320  */
1321  if (indlist == NIL)
1322  {
1323  pathlist = NIL;
1324  break;
1325  }
1326 
1327  /*
1328  * OK, pick the most promising AND combination, and add it to
1329  * pathlist.
1330  */
1331  bitmapqual = choose_bitmap_and(root, rel, indlist);
1332  pathlist = lappend(pathlist, bitmapqual);
1333  }
1334 
1335  /*
1336  * If we have a match for every arm, then turn them into a
1337  * BitmapOrPath, and add to result list.
1338  */
1339  if (pathlist != NIL)
1340  {
1341  bitmapqual = (Path *) create_bitmap_or_path(root, rel, pathlist);
1342  result = lappend(result, bitmapqual);
1343  }
1344  }
1345 
1346  return result;
1347 }
1348 
1349 
1350 /*
1351  * choose_bitmap_and
1352  * Given a nonempty list of bitmap paths, AND them into one path.
1353  *
1354  * This is a nontrivial decision since we can legally use any subset of the
1355  * given path set. We want to choose a good tradeoff between selectivity
1356  * and cost of computing the bitmap.
1357  *
1358  * The result is either a single one of the inputs, or a BitmapAndPath
1359  * combining multiple inputs.
1360  */
1361 static Path *
1362 choose_bitmap_and(PlannerInfo *root, RelOptInfo *rel, List *paths)
1363 {
1364  int npaths = list_length(paths);
1365  PathClauseUsage **pathinfoarray;
1366  PathClauseUsage *pathinfo;
1367  List *clauselist;
1368  List *bestpaths = NIL;
1369  Cost bestcost = 0;
1370  int i,
1371  j;
1372  ListCell *l;
1373 
1374  Assert(npaths > 0); /* else caller error */
1375  if (npaths == 1)
1376  return (Path *) linitial(paths); /* easy case */
1377 
1378  /*
1379  * In theory we should consider every nonempty subset of the given paths.
1380  * In practice that seems like overkill, given the crude nature of the
1381  * estimates, not to mention the possible effects of higher-level AND and
1382  * OR clauses. Moreover, it's completely impractical if there are a large
1383  * number of paths, since the work would grow as O(2^N).
1384  *
1385  * As a heuristic, we first check for paths using exactly the same sets of
1386  * WHERE clauses + index predicate conditions, and reject all but the
1387  * cheapest-to-scan in any such group. This primarily gets rid of indexes
1388  * that include the interesting columns but also irrelevant columns. (In
1389  * situations where the DBA has gone overboard on creating variant
1390  * indexes, this can make for a very large reduction in the number of
1391  * paths considered further.)
1392  *
1393  * We then sort the surviving paths with the cheapest-to-scan first, and
1394  * for each path, consider using that path alone as the basis for a bitmap
1395  * scan. Then we consider bitmap AND scans formed from that path plus
1396  * each subsequent (higher-cost) path, adding on a subsequent path if it
1397  * results in a reduction in the estimated total scan cost. This means we
1398  * consider about O(N^2) rather than O(2^N) path combinations, which is
1399  * quite tolerable, especially given than N is usually reasonably small
1400  * because of the prefiltering step. The cheapest of these is returned.
1401  *
1402  * We will only consider AND combinations in which no two indexes use the
1403  * same WHERE clause. This is a bit of a kluge: it's needed because
1404  * costsize.c and clausesel.c aren't very smart about redundant clauses.
1405  * They will usually double-count the redundant clauses, producing a
1406  * too-small selectivity that makes a redundant AND step look like it
1407  * reduces the total cost. Perhaps someday that code will be smarter and
1408  * we can remove this limitation. (But note that this also defends
1409  * against flat-out duplicate input paths, which can happen because
1410  * match_join_clauses_to_index will find the same OR join clauses that
1411  * extract_restriction_or_clauses has pulled OR restriction clauses out
1412  * of.)
1413  *
1414  * For the same reason, we reject AND combinations in which an index
1415  * predicate clause duplicates another clause. Here we find it necessary
1416  * to be even stricter: we'll reject a partial index if any of its
1417  * predicate clauses are implied by the set of WHERE clauses and predicate
1418  * clauses used so far. This covers cases such as a condition "x = 42"
1419  * used with a plain index, followed by a clauseless scan of a partial
1420  * index "WHERE x >= 40 AND x < 50". The partial index has been accepted
1421  * only because "x = 42" was present, and so allowing it would partially
1422  * double-count selectivity. (We could use predicate_implied_by on
1423  * regular qual clauses too, to have a more intelligent, but much more
1424  * expensive, check for redundancy --- but in most cases simple equality
1425  * seems to suffice.)
1426  */
1427 
1428  /*
1429  * Extract clause usage info and detect any paths that use exactly the
1430  * same set of clauses; keep only the cheapest-to-scan of any such groups.
1431  * The surviving paths are put into an array for qsort'ing.
1432  */
1433  pathinfoarray = (PathClauseUsage **)
1434  palloc(npaths * sizeof(PathClauseUsage *));
1435  clauselist = NIL;
1436  npaths = 0;
1437  foreach(l, paths)
1438  {
1439  Path *ipath = (Path *) lfirst(l);
1440 
1441  pathinfo = classify_index_clause_usage(ipath, &clauselist);
1442 
1443  /* If it's unclassifiable, treat it as distinct from all others */
1444  if (pathinfo->unclassifiable)
1445  {
1446  pathinfoarray[npaths++] = pathinfo;
1447  continue;
1448  }
1449 
1450  for (i = 0; i < npaths; i++)
1451  {
1452  if (!pathinfoarray[i]->unclassifiable &&
1453  bms_equal(pathinfo->clauseids, pathinfoarray[i]->clauseids))
1454  break;
1455  }
1456  if (i < npaths)
1457  {
1458  /* duplicate clauseids, keep the cheaper one */
1459  Cost ncost;
1460  Cost ocost;
1461  Selectivity nselec;
1462  Selectivity oselec;
1463 
1464  cost_bitmap_tree_node(pathinfo->path, &ncost, &nselec);
1465  cost_bitmap_tree_node(pathinfoarray[i]->path, &ocost, &oselec);
1466  if (ncost < ocost)
1467  pathinfoarray[i] = pathinfo;
1468  }
1469  else
1470  {
1471  /* not duplicate clauseids, add to array */
1472  pathinfoarray[npaths++] = pathinfo;
1473  }
1474  }
1475 
1476  /* If only one surviving path, we're done */
1477  if (npaths == 1)
1478  return pathinfoarray[0]->path;
1479 
1480  /* Sort the surviving paths by index access cost */
1481  qsort(pathinfoarray, npaths, sizeof(PathClauseUsage *),
1482  path_usage_comparator);
1483 
1484  /*
1485  * For each surviving index, consider it as an "AND group leader", and see
1486  * whether adding on any of the later indexes results in an AND path with
1487  * cheaper total cost than before. Then take the cheapest AND group.
1488  *
1489  * Note: paths that are either clauseless or unclassifiable will have
1490  * empty clauseids, so that they will not be rejected by the clauseids
1491  * filter here, nor will they cause later paths to be rejected by it.
1492  */
1493  for (i = 0; i < npaths; i++)
1494  {
1495  Cost costsofar;
1496  List *qualsofar;
1497  Bitmapset *clauseidsofar;
1498 
1499  pathinfo = pathinfoarray[i];
1500  paths = list_make1(pathinfo->path);
1501  costsofar = bitmap_scan_cost_est(root, rel, pathinfo->path);
1502  qualsofar = list_concat_copy(pathinfo->quals, pathinfo->preds);
1503  clauseidsofar = bms_copy(pathinfo->clauseids);
1504 
1505  for (j = i + 1; j < npaths; j++)
1506  {
1507  Cost newcost;
1508 
1509  pathinfo = pathinfoarray[j];
1510  /* Check for redundancy */
1511  if (bms_overlap(pathinfo->clauseids, clauseidsofar))
1512  continue; /* consider it redundant */
1513  if (pathinfo->preds)
1514  {
1515  bool redundant = false;
1516 
1517  /* we check each predicate clause separately */
1518  foreach(l, pathinfo->preds)
1519  {
1520  Node *np = (Node *) lfirst(l);
1521 
1522  if (predicate_implied_by(list_make1(np), qualsofar, false))
1523  {
1524  redundant = true;
1525  break; /* out of inner foreach loop */
1526  }
1527  }
1528  if (redundant)
1529  continue;
1530  }
1531  /* tentatively add new path to paths, so we can estimate cost */
1532  paths = lappend(paths, pathinfo->path);
1533  newcost = bitmap_and_cost_est(root, rel, paths);
1534  if (newcost < costsofar)
1535  {
1536  /* keep new path in paths, update subsidiary variables */
1537  costsofar = newcost;
1538  qualsofar = list_concat(qualsofar, pathinfo->quals);
1539  qualsofar = list_concat(qualsofar, pathinfo->preds);
1540  clauseidsofar = bms_add_members(clauseidsofar,
1541  pathinfo->clauseids);
1542  }
1543  else
1544  {
1545  /* reject new path, remove it from paths list */
1546  paths = list_truncate(paths, list_length(paths) - 1);
1547  }
1548  }
1549 
1550  /* Keep the cheapest AND-group (or singleton) */
1551  if (i == 0 || costsofar < bestcost)
1552  {
1553  bestpaths = paths;
1554  bestcost = costsofar;
1555  }
1556 
1557  /* some easy cleanup (we don't try real hard though) */
1558  list_free(qualsofar);
1559  }
1560 
1561  if (list_length(bestpaths) == 1)
1562  return (Path *) linitial(bestpaths); /* no need for AND */
1563  return (Path *) create_bitmap_and_path(root, rel, bestpaths);
1564 }
1565 
1566 /* qsort comparator to sort in increasing index access cost order */
1567 static int
1568 path_usage_comparator(const void *a, const void *b)
1569 {
1570  PathClauseUsage *pa = *(PathClauseUsage *const *) a;
1571  PathClauseUsage *pb = *(PathClauseUsage *const *) b;
1572  Cost acost;
1573  Cost bcost;
1574  Selectivity aselec;
1575  Selectivity bselec;
1576 
1577  cost_bitmap_tree_node(pa->path, &acost, &aselec);
1578  cost_bitmap_tree_node(pb->path, &bcost, &bselec);
1579 
1580  /*
1581  * If costs are the same, sort by selectivity.
1582  */
1583  if (acost < bcost)
1584  return -1;
1585  if (acost > bcost)
1586  return 1;
1587 
1588  if (aselec < bselec)
1589  return -1;
1590  if (aselec > bselec)
1591  return 1;
1592 
1593  return 0;
1594 }
1595 
1596 /*
1597  * Estimate the cost of actually executing a bitmap scan with a single
1598  * index path (which could be a BitmapAnd or BitmapOr node).
1599  */
1600 static Cost
1601 bitmap_scan_cost_est(PlannerInfo *root, RelOptInfo *rel, Path *ipath)
1602 {
1603  BitmapHeapPath bpath;
1604 
1605  /* Set up a dummy BitmapHeapPath */
1606  bpath.path.type = T_BitmapHeapPath;
1607  bpath.path.pathtype = T_BitmapHeapScan;
1608  bpath.path.parent = rel;
1609  bpath.path.pathtarget = rel->reltarget;
1610  bpath.path.param_info = ipath->param_info;
1611  bpath.path.pathkeys = NIL;
1612  bpath.bitmapqual = ipath;
1613 
1614  /*
1615  * Check the cost of temporary path without considering parallelism.
1616  * Parallel bitmap heap path will be considered at later stage.
1617  */
1618  bpath.path.parallel_workers = 0;
1619 
1620  /* Now we can do cost_bitmap_heap_scan */
1621  cost_bitmap_heap_scan(&bpath.path, root, rel,
1622  bpath.path.param_info,
1623  ipath,
1624  get_loop_count(root, rel->relid,
1625  PATH_REQ_OUTER(ipath)));
1626 
1627  return bpath.path.total_cost;
1628 }
1629 
1630 /*
1631  * Estimate the cost of actually executing a BitmapAnd scan with the given
1632  * inputs.
1633  */
1634 static Cost
1635 bitmap_and_cost_est(PlannerInfo *root, RelOptInfo *rel, List *paths)
1636 {
1637  BitmapAndPath *apath;
1638 
1639  /*
1640  * Might as well build a real BitmapAndPath here, as the work is slightly
1641  * too complicated to be worth repeating just to save one palloc.
1642  */
1643  apath = create_bitmap_and_path(root, rel, paths);
1644 
1645  return bitmap_scan_cost_est(root, rel, (Path *) apath);
1646 }
1647 
1648 
1649 /*
1650  * classify_index_clause_usage
1651  * Construct a PathClauseUsage struct describing the WHERE clauses and
1652  * index predicate clauses used by the given indexscan path.
1653  * We consider two clauses the same if they are equal().
1654  *
1655  * At some point we might want to migrate this info into the Path data
1656  * structure proper, but for the moment it's only needed within
1657  * choose_bitmap_and().
1658  *
1659  * *clauselist is used and expanded as needed to identify all the distinct
1660  * clauses seen across successive calls. Caller must initialize it to NIL
1661  * before first call of a set.
1662  */
1663 static PathClauseUsage *
1664 classify_index_clause_usage(Path *path, List **clauselist)
1665 {
1666  PathClauseUsage *result;
1667  Bitmapset *clauseids;
1668  ListCell *lc;
1669 
1670  result = (PathClauseUsage *) palloc(sizeof(PathClauseUsage));
1671  result->path = path;
1672 
1673  /* Recursively find the quals and preds used by the path */
1674  result->quals = NIL;
1675  result->preds = NIL;
1676  find_indexpath_quals(path, &result->quals, &result->preds);
1677 
1678  /*
1679  * Some machine-generated queries have outlandish numbers of qual clauses.
1680  * To avoid getting into O(N^2) behavior even in this preliminary
1681  * classification step, we want to limit the number of entries we can
1682  * accumulate in *clauselist. Treat any path with more than 100 quals +
1683  * preds as unclassifiable, which will cause calling code to consider it
1684  * distinct from all other paths.
1685  */
1686  if (list_length(result->quals) + list_length(result->preds) > 100)
1687  {
1688  result->clauseids = NULL;
1689  result->unclassifiable = true;
1690  return result;
1691  }
1692 
1693  /* Build up a bitmapset representing the quals and preds */
1694  clauseids = NULL;
1695  foreach(lc, result->quals)
1696  {
1697  Node *node = (Node *) lfirst(lc);
1698 
1699  clauseids = bms_add_member(clauseids,
1700  find_list_position(node, clauselist));
1701  }
1702  foreach(lc, result->preds)
1703  {
1704  Node *node = (Node *) lfirst(lc);
1705 
1706  clauseids = bms_add_member(clauseids,
1707  find_list_position(node, clauselist));
1708  }
1709  result->clauseids = clauseids;
1710  result->unclassifiable = false;
1711 
1712  return result;
1713 }
1714 
1715 
1716 /*
1717  * find_indexpath_quals
1718  *
1719  * Given the Path structure for a plain or bitmap indexscan, extract lists
1720  * of all the index clauses and index predicate conditions used in the Path.
1721  * These are appended to the initial contents of *quals and *preds (hence
1722  * caller should initialize those to NIL).
1723  *
1724  * Note we are not trying to produce an accurate representation of the AND/OR
1725  * semantics of the Path, but just find out all the base conditions used.
1726  *
1727  * The result lists contain pointers to the expressions used in the Path,
1728  * but all the list cells are freshly built, so it's safe to destructively
1729  * modify the lists (eg, by concat'ing with other lists).
1730  */
1731 static void
1732 find_indexpath_quals(Path *bitmapqual, List **quals, List **preds)
1733 {
1734  if (IsA(bitmapqual, BitmapAndPath))
1735  {
1736  BitmapAndPath *apath = (BitmapAndPath *) bitmapqual;
1737  ListCell *l;
1738 
1739  foreach(l, apath->bitmapquals)
1740  {
1741  find_indexpath_quals((Path *) lfirst(l), quals, preds);
1742  }
1743  }
1744  else if (IsA(bitmapqual, BitmapOrPath))
1745  {
1746  BitmapOrPath *opath = (BitmapOrPath *) bitmapqual;
1747  ListCell *l;
1748 
1749  foreach(l, opath->bitmapquals)
1750  {
1751  find_indexpath_quals((Path *) lfirst(l), quals, preds);
1752  }
1753  }
1754  else if (IsA(bitmapqual, IndexPath))
1755  {
1756  IndexPath *ipath = (IndexPath *) bitmapqual;
1757  ListCell *l;
1758 
1759  foreach(l, ipath->indexclauses)
1760  {
1761  IndexClause *iclause = (IndexClause *) lfirst(l);
1762 
1763  *quals = lappend(*quals, iclause->rinfo->clause);
1764  }
1765  *preds = list_concat(*preds, ipath->indexinfo->indpred);
1766  }
1767  else
1768  elog(ERROR, "unrecognized node type: %d", nodeTag(bitmapqual));
1769 }
1770 
1771 
1772 /*
1773  * find_list_position
1774  * Return the given node's position (counting from 0) in the given
1775  * list of nodes. If it's not equal() to any existing list member,
1776  * add it at the end, and return that position.
1777  */
1778 static int
1779 find_list_position(Node *node, List **nodelist)
1780 {
1781  int i;
1782  ListCell *lc;
1783 
1784  i = 0;
1785  foreach(lc, *nodelist)
1786  {
1787  Node *oldnode = (Node *) lfirst(lc);
1788 
1789  if (equal(node, oldnode))
1790  return i;
1791  i++;
1792  }
1793 
1794  *nodelist = lappend(*nodelist, node);
1795 
1796  return i;
1797 }
1798 
1799 
1800 /*
1801  * check_index_only
1802  * Determine whether an index-only scan is possible for this index.
1803  */
1804 static bool
1805 check_index_only(RelOptInfo *rel, IndexOptInfo *index)
1806 {
1807  bool result;
1808  Bitmapset *attrs_used = NULL;
1809  Bitmapset *index_canreturn_attrs = NULL;
1810  Bitmapset *index_cannotreturn_attrs = NULL;
1811  ListCell *lc;
1812  int i;
1813 
1814  /* Index-only scans must be enabled */
1815  if (!enable_indexonlyscan)
1816  return false;
1817 
1818  /*
1819  * Check that all needed attributes of the relation are available from the
1820  * index.
1821  */
1822 
1823  /*
1824  * First, identify all the attributes needed for joins or final output.
1825  * Note: we must look at rel's targetlist, not the attr_needed data,
1826  * because attr_needed isn't computed for inheritance child rels.
1827  */
1828  pull_varattnos((Node *) rel->reltarget->exprs, rel->relid, &attrs_used);
1829 
1830  /*
1831  * Add all the attributes used by restriction clauses; but consider only
1832  * those clauses not implied by the index predicate, since ones that are
1833  * so implied don't need to be checked explicitly in the plan.
1834  *
1835  * Note: attributes used only in index quals would not be needed at
1836  * runtime either, if we are certain that the index is not lossy. However
1837  * it'd be complicated to account for that accurately, and it doesn't
1838  * matter in most cases, since we'd conclude that such attributes are
1839  * available from the index anyway.
1840  */
1841  foreach(lc, index->indrestrictinfo)
1842  {
1843  RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
1844 
1845  pull_varattnos((Node *) rinfo->clause, rel->relid, &attrs_used);
1846  }
1847 
1848  /*
1849  * Construct a bitmapset of columns that the index can return back in an
1850  * index-only scan. If there are multiple index columns containing the
1851  * same attribute, all of them must be capable of returning the value,
1852  * since we might recheck operators on any of them. (Potentially we could
1853  * be smarter about that, but it's such a weird situation that it doesn't
1854  * seem worth spending a lot of sweat on.)
1855  */
1856  for (i = 0; i < index->ncolumns; i++)
1857  {
1858  int attno = index->indexkeys[i];
1859 
1860  /*
1861  * For the moment, we just ignore index expressions. It might be nice
1862  * to do something with them, later.
1863  */
1864  if (attno == 0)
1865  continue;
1866 
1867  if (index->canreturn[i])
1868  index_canreturn_attrs =
1869  bms_add_member(index_canreturn_attrs,
1870  attno - FirstLowInvalidHeapAttributeNumber);
1871  else
1872  index_cannotreturn_attrs =
1873  bms_add_member(index_cannotreturn_attrs,
1874  attno - FirstLowInvalidHeapAttributeNumber);
1875  }
1876 
1877  index_canreturn_attrs = bms_del_members(index_canreturn_attrs,
1878  index_cannotreturn_attrs);
1879 
1880  /* Do we have all the necessary attributes? */
1881  result = bms_is_subset(attrs_used, index_canreturn_attrs);
1882 
1883  bms_free(attrs_used);
1884  bms_free(index_canreturn_attrs);
1885  bms_free(index_cannotreturn_attrs);
1886 
1887  return result;
1888 }
1889 
1890 /*
1891  * get_loop_count
1892  * Choose the loop count estimate to use for costing a parameterized path
1893  * with the given set of outer relids.
1894  *
1895  * Since we produce parameterized paths before we've begun to generate join
1896  * relations, it's impossible to predict exactly how many times a parameterized
1897  * path will be iterated; we don't know the size of the relation that will be
1898  * on the outside of the nestloop. However, we should try to account for
1899  * multiple iterations somehow in costing the path. The heuristic embodied
1900  * here is to use the rowcount of the smallest other base relation needed in
1901  * the join clauses used by the path. (We could alternatively consider the
1902  * largest one, but that seems too optimistic.) This is of course the right
1903  * answer for single-other-relation cases, and it seems like a reasonable
1904  * zero-order approximation for multiway-join cases.
1905  *
1906  * In addition, we check to see if the other side of each join clause is on
1907  * the inside of some semijoin that the current relation is on the outside of.
1908  * If so, the only way that a parameterized path could be used is if the
1909  * semijoin RHS has been unique-ified, so we should use the number of unique
1910  * RHS rows rather than using the relation's raw rowcount.
1911  *
1912  * Note: for this to work, allpaths.c must establish all baserel size
1913  * estimates before it begins to compute paths, or at least before it
1914  * calls create_index_paths().
1915  */
1916 static double
1917 get_loop_count(PlannerInfo *root, Index cur_relid, Relids outer_relids)
1918 {
1919  double result;
1920  int outer_relid;
1921 
1922  /* For a non-parameterized path, just return 1.0 quickly */
1923  if (outer_relids == NULL)
1924  return 1.0;
1925 
1926  result = 0.0;
1927  outer_relid = -1;
1928  while ((outer_relid = bms_next_member(outer_relids, outer_relid)) >= 0)
1929  {
1930  RelOptInfo *outer_rel;
1931  double rowcount;
1932 
1933  /* Paranoia: ignore bogus relid indexes */
1934  if (outer_relid >= root->simple_rel_array_size)
1935  continue;
1936  outer_rel = root->simple_rel_array[outer_relid];
1937  if (outer_rel == NULL)
1938  continue;
1939  Assert(outer_rel->relid == outer_relid); /* sanity check on array */
1940 
1941  /* Other relation could be proven empty, if so ignore */
1942  if (IS_DUMMY_REL(outer_rel))
1943  continue;
1944 
1945  /* Otherwise, rel's rows estimate should be valid by now */
1946  Assert(outer_rel->rows > 0);
1947 
1948  /* Check to see if rel is on the inside of any semijoins */
1949  rowcount = adjust_rowcount_for_semijoins(root,
1950  cur_relid,
1951  outer_relid,
1952  outer_rel->rows);
1953 
1954  /* Remember smallest row count estimate among the outer rels */
1955  if (result == 0.0 || result > rowcount)
1956  result = rowcount;
1957  }
1958  /* Return 1.0 if we found no valid relations (shouldn't happen) */
1959  return (result > 0.0) ? result : 1.0;
1960 }
1961 
1962 /*
1963  * Check to see if outer_relid is on the inside of any semijoin that cur_relid
1964  * is on the outside of. If so, replace rowcount with the estimated number of
1965  * unique rows from the semijoin RHS (assuming that's smaller, which it might
1966  * not be). The estimate is crude but it's the best we can do at this stage
1967  * of the proceedings.
1968  */
1969 static double
1970 adjust_rowcount_for_semijoins(PlannerInfo *root,
1971  Index cur_relid,
1972  Index outer_relid,
1973  double rowcount)
1974 {
1975  ListCell *lc;
1976 
1977  foreach(lc, root->join_info_list)
1978  {
1979  SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);
1980 
1981  if (sjinfo->jointype == JOIN_SEMI &&
1982  bms_is_member(cur_relid, sjinfo->syn_lefthand) &&
1983  bms_is_member(outer_relid, sjinfo->syn_righthand))
1984  {
1985  /* Estimate number of unique-ified rows */
1986  double nraw;
1987  double nunique;
1988 
1989  nraw = approximate_joinrel_size(root, sjinfo->syn_righthand);
1990  nunique = estimate_num_groups(root,
1991  sjinfo->semi_rhs_exprs,
1992  nraw,
1993  NULL,
1994  NULL);
1995  if (rowcount > nunique)
1996  rowcount = nunique;
1997  }
1998  }
1999  return rowcount;
2000 }
2001 
2002 /*
2003  * Make an approximate estimate of the size of a joinrel.
2004  *
2005  * We don't have enough info at this point to get a good estimate, so we
2006  * just multiply the base relation sizes together. Fortunately, this is
2007  * the right answer anyway for the most common case with a single relation
2008  * on the RHS of a semijoin. Also, estimate_num_groups() has only a weak
2009  * dependency on its input_rows argument (it basically uses it as a clamp).
2010  * So we might be able to get a fairly decent end result even with a severe
2011  * overestimate of the RHS's raw size.
2012  */
2013 static double
2014 approximate_joinrel_size(PlannerInfo *root, Relids relids)
2015 {
2016  double rowcount = 1.0;
2017  int relid;
2018 
2019  relid = -1;
2020  while ((relid = bms_next_member(relids, relid)) >= 0)
2021  {
2022  RelOptInfo *rel;
2023 
2024  /* Paranoia: ignore bogus relid indexes */
2025  if (relid >= root->simple_rel_array_size)
2026  continue;
2027  rel = root->simple_rel_array[relid];
2028  if (rel == NULL)
2029  continue;
2030  Assert(rel->relid == relid); /* sanity check on array */
2031 
2032  /* Relation could be proven empty, if so ignore */
2033  if (IS_DUMMY_REL(rel))
2034  continue;
2035 
2036  /* Otherwise, rel's rows estimate should be valid by now */
2037  Assert(rel->rows > 0);
2038 
2039  /* Accumulate product */
2040  rowcount *= rel->rows;
2041  }
2042  return rowcount;
2043 }
2044 
2045 
2046 /****************************************************************************
2047  * ---- ROUTINES TO CHECK QUERY CLAUSES ----
2048  ****************************************************************************/
2049 
2050 /*
2051  * match_restriction_clauses_to_index
2052  * Identify restriction clauses for the rel that match the index.
2053  * Matching clauses are added to *clauseset.
2054  */
2055 static void
2056 match_restriction_clauses_to_index(PlannerInfo *root,
2057  IndexOptInfo *index,
2058  IndexClauseSet *clauseset)
2059 {
2060  /* We can ignore clauses that are implied by the index predicate */
2061  match_clauses_to_index(root, index->indrestrictinfo, index, clauseset);
2062 }
2063 
2064 /*
2065  * match_join_clauses_to_index
2066  * Identify join clauses for the rel that match the index.
2067  * Matching clauses are added to *clauseset.
2068  * Also, add any potentially usable join OR clauses to *joinorclauses.
2069  */
2070 static void
2071 match_join_clauses_to_index(PlannerInfo *root,
2072  RelOptInfo *rel, IndexOptInfo *index,
2073  IndexClauseSet *clauseset,
2074  List **joinorclauses)
2075 {
2076  ListCell *lc;
2077 
2078  /* Scan the rel's join clauses */
2079  foreach(lc, rel->joininfo)
2080  {
2081  RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
2082 
2083  /* Check if clause can be moved to this rel */
2084  if (!join_clause_is_movable_to(rinfo, rel))
2085  continue;
2086 
2087  /* Potentially usable, so see if it matches the index or is an OR */
2088  if (restriction_is_or_clause(rinfo))
2089  *joinorclauses = lappend(*joinorclauses, rinfo);
2090  else
2091  match_clause_to_index(root, rinfo, index, clauseset);
2092  }
2093 }
2094 
2095 /*
2096  * match_eclass_clauses_to_index
2097  * Identify EquivalenceClass join clauses for the rel that match the index.
2098  * Matching clauses are added to *clauseset.
2099  */
2100 static void
2101 match_eclass_clauses_to_index(PlannerInfo *root, IndexOptInfo *index,
2102  IndexClauseSet *clauseset)
2103 {
2104  int indexcol;
2105 
2106  /* No work if rel is not in any such ECs */
2107  if (!index->rel->has_eclass_joins)
2108  return;
2109 
2110  for (indexcol = 0; indexcol < index->nkeycolumns; indexcol++)
2111  {
2112  ec_member_matches_arg arg;
2113  List *clauses;
2114 
2115  /* Generate clauses, skipping any that join to lateral_referencers */
2116  arg.index = index;
2117  arg.indexcol = indexcol;
2118  clauses = generate_implied_equalities_for_column(root,
2119  index->rel,
2120  ec_member_matches_indexcol,
2121  (void *) &arg,
2122  index->rel->lateral_referencers);
2123 
2124  /*
2125  * We have to check whether the results actually do match the index,
2126  * since for non-btree indexes the EC's equality operators might not
2127  * be in the index opclass (cf ec_member_matches_indexcol).
2128  */
2129  match_clauses_to_index(root, clauses, index, clauseset);
2130  }
2131 }
2132 
2133 /*
2134  * match_clauses_to_index
2135  * Perform match_clause_to_index() for each clause in a list.
2136  * Matching clauses are added to *clauseset.
2137  */
2138 static void
2139 match_clauses_to_index(PlannerInfo *root,
2140  List *clauses,
2141  IndexOptInfo *index,
2142  IndexClauseSet *clauseset)
2143 {
2144  ListCell *lc;
2145 
2146  foreach(lc, clauses)
2147  {
2148  RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
2149 
2150  match_clause_to_index(root, rinfo, index, clauseset);
2151  }
2152 }
2153 
2154 /*
2155  * match_clause_to_index
2156  * Test whether a qual clause can be used with an index.
2157  *
2158  * If the clause is usable, add an IndexClause entry for it to the appropriate
2159  * list in *clauseset. (*clauseset must be initialized to zeroes before first
2160  * call.)
2161  *
2162  * Note: in some circumstances we may find the same RestrictInfos coming from
2163  * multiple places. Defend against redundant outputs by refusing to add a
2164  * clause twice (pointer equality should be a good enough check for this).
2165  *
2166  * Note: it's possible that a badly-defined index could have multiple matching
2167  * columns. We always select the first match if so; this avoids scenarios
2168  * wherein we get an inflated idea of the index's selectivity by using the
2169  * same clause multiple times with different index columns.
2170  */
2171 static void
2172 match_clause_to_index(PlannerInfo *root,
2173  RestrictInfo *rinfo,
2174  IndexOptInfo *index,
2175  IndexClauseSet *clauseset)
2176 {
2177  int indexcol;
2178 
2179  /*
2180  * Never match pseudoconstants to indexes. (Normally a match could not
2181  * happen anyway, since a pseudoconstant clause couldn't contain a Var,
2182  * but what if someone builds an expression index on a constant? It's not
2183  * totally unreasonable to do so with a partial index, either.)
2184  */
2185  if (rinfo->pseudoconstant)
2186  return;
2187 
2188  /*
2189  * If clause can't be used as an indexqual because it must wait till after
2190  * some lower-security-level restriction clause, reject it.
2191  */
2192  if (!restriction_is_securely_promotable(rinfo, index->rel))
2193  return;
2194 
2195  /* OK, check each index key column for a match */
2196  for (indexcol = 0; indexcol < index->nkeycolumns; indexcol++)
2197  {
2198  IndexClause *iclause;
2199  ListCell *lc;
2200 
2201  /* Ignore duplicates */
2202  foreach(lc, clauseset->indexclauses[indexcol])
2203  {
2204  IndexClause *iclause = (IndexClause *) lfirst(lc);
2205 
2206  if (iclause->rinfo == rinfo)
2207  return;
2208  }
2209 
2210  /* OK, try to match the clause to the index column */
2211  iclause = match_clause_to_indexcol(root,
2212  rinfo,
2213  indexcol,
2214  index);
2215  if (iclause)
2216  {
2217  /* Success, so record it */
2218  clauseset->indexclauses[indexcol] =
2219  lappend(clauseset->indexclauses[indexcol], iclause);
2220  clauseset->nonempty = true;
2221  return;
2222  }
2223  }
2224 }
2225 
2226 /*
2227  * match_clause_to_indexcol()
2228  * Determine whether a restriction clause matches a column of an index,
2229  * and if so, build an IndexClause node describing the details.
2230  *
2231  * To match an index normally, an operator clause:
2232  *
2233  * (1) must be in the form (indexkey op const) or (const op indexkey);
2234  * and
2235  * (2) must contain an operator which is in the index's operator family
2236  * for this column; and
2237  * (3) must match the collation of the index, if collation is relevant.
2238  *
2239  * Our definition of "const" is exceedingly liberal: we allow anything that
2240  * doesn't involve a volatile function or a Var of the index's relation.
2241  * In particular, Vars belonging to other relations of the query are
2242  * accepted here, since a clause of that form can be used in a
2243  * parameterized indexscan. It's the responsibility of higher code levels
2244  * to manage restriction and join clauses appropriately.
2245  *
2246  * Note: we do need to check for Vars of the index's relation on the
2247  * "const" side of the clause, since clauses like (a.f1 OP (b.f2 OP a.f3))
2248  * are not processable by a parameterized indexscan on a.f1, whereas
2249  * something like (a.f1 OP (b.f2 OP c.f3)) is.
2250  *
2251  * Presently, the executor can only deal with indexquals that have the
2252  * indexkey on the left, so we can only use clauses that have the indexkey
2253  * on the right if we can commute the clause to put the key on the left.
2254  * We handle that by generating an IndexClause with the correctly-commuted
2255  * opclause as a derived indexqual.
2256  *
2257  * If the index has a collation, the clause must have the same collation.
2258  * For collation-less indexes, we assume it doesn't matter; this is
2259  * necessary for cases like "hstore ? text", wherein hstore's operators
2260  * don't care about collation but the clause will get marked with a
2261  * collation anyway because of the text argument. (This logic is
2262  * embodied in the macro IndexCollMatchesExprColl.)
2263  *
2264  * It is also possible to match RowCompareExpr clauses to indexes (but
2265  * currently, only btree indexes handle this).
2266  *
2267  * It is also possible to match ScalarArrayOpExpr clauses to indexes, when
2268  * the clause is of the form "indexkey op ANY (arrayconst)".
2269  *
2270  * For boolean indexes, it is also possible to match the clause directly
2271  * to the indexkey; or perhaps the clause is (NOT indexkey).
2272  *
2273  * And, last but not least, some operators and functions can be processed
2274  * to derive (typically lossy) indexquals from a clause that isn't in
2275  * itself indexable. If we see that any operand of an OpExpr or FuncExpr
2276  * matches the index key, and the function has a planner support function
2277  * attached to it, we'll invoke the support function to see if such an
2278  * indexqual can be built.
2279  *
2280  * 'rinfo' is the clause to be tested (as a RestrictInfo node).
2281  * 'indexcol' is a column number of 'index' (counting from 0).
2282  * 'index' is the index of interest.
2283  *
2284  * Returns an IndexClause if the clause can be used with this index key,
2285  * or NULL if not.
2286  *
2287  * NOTE: returns NULL if clause is an OR or AND clause; it is the
2288  * responsibility of higher-level routines to cope with those.
2289  */
2290 static IndexClause *
2291 match_clause_to_indexcol(PlannerInfo *root,
2292  RestrictInfo *rinfo,
2293  int indexcol,
2294  IndexOptInfo *index)
2295 {
2296  IndexClause *iclause;
2297  Expr *clause = rinfo->clause;
2298  Oid opfamily;
2299 
2300  Assert(indexcol < index->nkeycolumns);
2301 
2302  /*
2303  * Historically this code has coped with NULL clauses. That's probably
2304  * not possible anymore, but we might as well continue to cope.
2305  */
2306  if (clause == NULL)
2307  return NULL;
2308 
2309  /* First check for boolean-index cases. */
2310  opfamily = index->opfamily[indexcol];
2311  if (IsBooleanOpfamily(opfamily))
2312  {
2313  iclause = match_boolean_index_clause(root, rinfo, indexcol, index);
2314  if (iclause)
2315  return iclause;
2316  }
2317 
2318  /*
2319  * Clause must be an opclause, funcclause, ScalarArrayOpExpr, or
2320  * RowCompareExpr. Or, if the index supports it, we can handle IS
2321  * NULL/NOT NULL clauses.
2322  */
2323  if (IsA(clause, OpExpr))
2324  {
2325  return match_opclause_to_indexcol(root, rinfo, indexcol, index);
2326  }
2327  else if (IsA(clause, FuncExpr))
2328  {
2329  return match_funcclause_to_indexcol(root, rinfo, indexcol, index);
2330  }
2331  else if (IsA(clause, ScalarArrayOpExpr))
2332  {
2333  return match_saopclause_to_indexcol(root, rinfo, indexcol, index);
2334  }
2335  else if (IsA(clause, RowCompareExpr))
2336  {
2337  return match_rowcompare_to_indexcol(root, rinfo, indexcol, index);
2338  }
2339  else if (index->amsearchnulls && IsA(clause, NullTest))
2340  {
2341  NullTest *nt = (NullTest *) clause;
2342 
2343  if (!nt->argisrow &&
2344  match_index_to_operand((Node *) nt->arg, indexcol, index))
2345  {
2346  iclause = makeNode(IndexClause);
2347  iclause->rinfo = rinfo;
2348  iclause->indexquals = list_make1(rinfo);
2349  iclause->lossy = false;
2350  iclause->indexcol = indexcol;
2351  iclause->indexcols = NIL;
2352  return iclause;
2353  }
2354  }
2355 
2356  return NULL;
2357 }
2358 
2359 /*
2360  * match_boolean_index_clause
2361  * Recognize restriction clauses that can be matched to a boolean index.
2362  *
2363  * The idea here is that, for an index on a boolean column that supports the
2364  * BooleanEqualOperator, we can transform a plain reference to the indexkey
2365  * into "indexkey = true", or "NOT indexkey" into "indexkey = false", etc,
2366  * so as to make the expression indexable using the index's "=" operator.
2367  * Since Postgres 8.1, we must do this because constant simplification does
2368  * the reverse transformation; without this code there'd be no way to use
2369  * such an index at all.
2370  *
2371  * This should be called only when IsBooleanOpfamily() recognizes the
2372  * index's operator family. We check to see if the clause matches the
2373  * index's key, and if so, build a suitable IndexClause.
2374  */
2375 static IndexClause *
2376 match_boolean_index_clause(PlannerInfo *root,
2377  RestrictInfo *rinfo,
2378  int indexcol,
2379  IndexOptInfo *index)
2380 {
2381  Node *clause = (Node *) rinfo->clause;
2382  Expr *op = NULL;
2383 
2384  /* Direct match? */
2385  if (match_index_to_operand(clause, indexcol, index))
2386  {
2387  /* convert to indexkey = TRUE */
2388  op = make_opclause(BooleanEqualOperator, BOOLOID, false,
2389  (Expr *) clause,
2390  (Expr *) makeBoolConst(true, false),
2391  InvalidOid, InvalidOid);
2392  }
2393  /* NOT clause? */
2394  else if (is_notclause(clause))
2395  {
2396  Node *arg = (Node *) get_notclausearg((Expr *) clause);
2397 
2398  if (match_index_to_operand(arg, indexcol, index))
2399  {
2400  /* convert to indexkey = FALSE */
2401  op = make_opclause(BooleanEqualOperator, BOOLOID, false,
2402  (Expr *) arg,
2403  (Expr *) makeBoolConst(false, false),
2404  InvalidOid, InvalidOid);
2405  }
2406  }
2407 
2408  /*
2409  * Since we only consider clauses at top level of WHERE, we can convert
2410  * indexkey IS TRUE and indexkey IS FALSE to index searches as well. The
2411  * different meaning for NULL isn't important.
2412  */
2413  else if (clause && IsA(clause, BooleanTest))
2414  {
2415  BooleanTest *btest = (BooleanTest *) clause;
2416  Node *arg = (Node *) btest->arg;
2417 
2418  if (btest->booltesttype == IS_TRUE &&
2419  match_index_to_operand(arg, indexcol, index))
2420  {
2421  /* convert to indexkey = TRUE */
2422  op = make_opclause(BooleanEqualOperator, BOOLOID, false,
2423  (Expr *) arg,
2424  (Expr *) makeBoolConst(true, false),
2425  InvalidOid, InvalidOid);
2426  }
2427  else if (btest->booltesttype == IS_FALSE &&
2428  match_index_to_operand(arg, indexcol, index))
2429  {
2430  /* convert to indexkey = FALSE */
2431  op = make_opclause(BooleanEqualOperator, BOOLOID, false,
2432  (Expr *) arg,
2433  (Expr *) makeBoolConst(false, false),
2434  InvalidOid, InvalidOid);
2435  }
2436  }
2437 
2438  /*
2439  * If we successfully made an operator clause from the given qual, we must
2440  * wrap it in an IndexClause. It's not lossy.
2441  */
2442  if (op)
2443  {
2444  IndexClause *iclause = makeNode(IndexClause);
2445 
2446  iclause->rinfo = rinfo;
2447  iclause->indexquals = list_make1(make_simple_restrictinfo(root, op));
2448  iclause->lossy = false;
2449  iclause->indexcol = indexcol;
2450  iclause->indexcols = NIL;
2451  return iclause;
2452  }
2453 
2454  return NULL;
2455 }
2456 
2457 /*
2458  * match_opclause_to_indexcol()
2459  * Handles the OpExpr case for match_clause_to_indexcol(),
2460  * which see for comments.
2461  */
2462 static IndexClause *
2463 match_opclause_to_indexcol(PlannerInfo *root,
2464  RestrictInfo *rinfo,
2465  int indexcol,
2466  IndexOptInfo *index)
2467 {
2468  IndexClause *iclause;
2469  OpExpr *clause = (OpExpr *) rinfo->clause;
2470  Node *leftop,
2471  *rightop;
2472  Oid expr_op;
2473  Oid expr_coll;
2474  Index index_relid;
2475  Oid opfamily;
2476  Oid idxcollation;
2477 
2478  /*
2479  * Only binary operators need apply. (In theory, a planner support
2480  * function could do something with a unary operator, but it seems
2481  * unlikely to be worth the cycles to check.)
2482  */
2483  if (list_length(clause->args) != 2)
2484  return NULL;
2485 
2486  leftop = (Node *) linitial(clause->args);
2487  rightop = (Node *) lsecond(clause->args);
2488  expr_op = clause->opno;
2489  expr_coll = clause->inputcollid;
2490 
2491  index_relid = index->rel->relid;
2492  opfamily = index->opfamily[indexcol];
2493  idxcollation = index->indexcollations[indexcol];
2494 
2495  /*
2496  * Check for clauses of the form: (indexkey operator constant) or
2497  * (constant operator indexkey). See match_clause_to_indexcol's notes
2498  * about const-ness.
2499  *
2500  * Note that we don't ask the support function about clauses that don't
2501  * have one of these forms. Again, in principle it might be possible to
2502  * do something, but it seems unlikely to be worth the cycles to check.
2503  */
2504  if (match_index_to_operand(leftop, indexcol, index) &&
2505  !bms_is_member(index_relid, rinfo->right_relids) &&
2506  !contain_volatile_functions(rightop))
2507  {
2508  if (IndexCollMatchesExprColl(idxcollation, expr_coll) &&
2509  op_in_opfamily(expr_op, opfamily))
2510  {
2511  iclause = makeNode(IndexClause);
2512  iclause->rinfo = rinfo;
2513  iclause->indexquals = list_make1(rinfo);
2514  iclause->lossy = false;
2515  iclause->indexcol = indexcol;
2516  iclause->indexcols = NIL;
2517  return iclause;
2518  }
2519 
2520  /*
2521  * If we didn't find a member of the index's opfamily, try the support
2522  * function for the operator's underlying function.
2523  */
2524  set_opfuncid(clause); /* make sure we have opfuncid */
2525  return get_index_clause_from_support(root,
2526  rinfo,
2527  clause->opfuncid,
2528  0, /* indexarg on left */
2529  indexcol,
2530  index);
2531  }
2532 
2533  if (match_index_to_operand(rightop, indexcol, index) &&
2534  !bms_is_member(index_relid, rinfo->left_relids) &&
2535  !contain_volatile_functions(leftop))
2536  {
2537  if (IndexCollMatchesExprColl(idxcollation, expr_coll))
2538  {
2539  Oid comm_op = get_commutator(expr_op);
2540 
2541  if (OidIsValid(comm_op) &&
2542  op_in_opfamily(comm_op, opfamily))
2543  {
2544  RestrictInfo *commrinfo;
2545 
2546  /* Build a commuted OpExpr and RestrictInfo */
2547  commrinfo = commute_restrictinfo(rinfo, comm_op);
2548 
2549  /* Make an IndexClause showing that as a derived qual */
2550  iclause = makeNode(IndexClause);
2551  iclause->rinfo = rinfo;
2552  iclause->indexquals = list_make1(commrinfo);
2553  iclause->lossy = false;
2554  iclause->indexcol = indexcol;
2555  iclause->indexcols = NIL;
2556  return iclause;
2557  }
2558  }
2559 
2560  /*
2561  * If we didn't find a member of the index's opfamily, try the support
2562  * function for the operator's underlying function.
2563  */
2564  set_opfuncid(clause); /* make sure we have opfuncid */
2565  return get_index_clause_from_support(root,
2566  rinfo,
2567  clause->opfuncid,
2568  1, /* indexarg on right */
2569  indexcol,
2570  index);
2571  }
2572 
2573  return NULL;
2574 }
2575 
2576 /*
2577  * match_funcclause_to_indexcol()
2578  * Handles the FuncExpr case for match_clause_to_indexcol(),
2579  * which see for comments.
2580  */
2581 static IndexClause *
2582 match_funcclause_to_indexcol(PlannerInfo *root,
2583  RestrictInfo *rinfo,
2584  int indexcol,
2585  IndexOptInfo *index)
2586 {
2587  FuncExpr *clause = (FuncExpr *) rinfo->clause;
2588  int indexarg;
2589  ListCell *lc;
2590 
2591  /*
2592  * We have no built-in intelligence about function clauses, but if there's
2593  * a planner support function, it might be able to do something. But, to
2594  * cut down on wasted planning cycles, only call the support function if
2595  * at least one argument matches the target index column.
2596  *
2597  * Note that we don't insist on the other arguments being pseudoconstants;
2598  * the support function has to check that. This is to allow cases where
2599  * only some of the other arguments need to be included in the indexqual.
2600  */
2601  indexarg = 0;
2602  foreach(lc, clause->args)
2603  {
2604  Node *op = (Node *) lfirst(lc);
2605 
2606  if (match_index_to_operand(op, indexcol, index))
2607  {
2608  return get_index_clause_from_support(root,
2609  rinfo,
2610  clause->funcid,
2611  indexarg,
2612  indexcol,
2613  index);
2614  }
2615 
2616  indexarg++;
2617  }
2618 
2619  return NULL;
2620 }
2621 
2622 /*
2623  * get_index_clause_from_support()
2624  * If the function has a planner support function, try to construct
2625  * an IndexClause using indexquals created by the support function.
2626  */
2627 static IndexClause *
2628 get_index_clause_from_support(PlannerInfo *root,
2629  RestrictInfo *rinfo,
2630  Oid funcid,
2631  int indexarg,
2632  int indexcol,
2633  IndexOptInfo *index)
2634 {
2635  Oid prosupport = get_func_support(funcid);
2636  SupportRequestIndexCondition req;
2637  List *sresult;
2638 
2639  if (!OidIsValid(prosupport))
2640  return NULL;
2641 
2642  req.type = T_SupportRequestIndexCondition;
2643  req.root = root;
2644  req.funcid = funcid;
2645  req.node = (Node *) rinfo->clause;
2646  req.indexarg = indexarg;
2647  req.index = index;
2648  req.indexcol = indexcol;
2649  req.opfamily = index->opfamily[indexcol];
2650  req.indexcollation = index->indexcollations[indexcol];
2651 
2652  req.lossy = true; /* default assumption */
2653 
2654  sresult = (List *)
2655  DatumGetPointer(OidFunctionCall1(prosupport,
2656  PointerGetDatum(&req)));
2657 
2658  if (sresult != NIL)
2659  {
2660  IndexClause *iclause = makeNode(IndexClause);
2661  List *indexquals = NIL;
2662  ListCell *lc;
2663 
2664  /*
2665  * The support function API says it should just give back bare
2666  * clauses, so here we must wrap each one in a RestrictInfo.
2667  */
2668  foreach(lc, sresult)
2669  {
2670  Expr *clause = (Expr *) lfirst(lc);
2671 
2672  indexquals = lappend(indexquals,
2673  make_simple_restrictinfo(root, clause));
2674  }
2675 
2676  iclause->rinfo = rinfo;
2677  iclause->indexquals = indexquals;
2678  iclause->lossy = req.lossy;
2679  iclause->indexcol = indexcol;
2680  iclause->indexcols = NIL;
2681 
2682  return iclause;
2683  }
2684 
2685  return NULL;
2686 }
2687 
2688 /*
2689  * match_saopclause_to_indexcol()
2690  * Handles the ScalarArrayOpExpr case for match_clause_to_indexcol(),
2691  * which see for comments.
2692  */
2693 static IndexClause *
2694 match_saopclause_to_indexcol(PlannerInfo *root,
2695  RestrictInfo *rinfo,
2696  int indexcol,
2697  IndexOptInfo *index)
2698 {
2699  ScalarArrayOpExpr *saop = (ScalarArrayOpExpr *) rinfo->clause;
2700  Node *leftop,
2701  *rightop;
2702  Relids right_relids;
2703  Oid expr_op;
2704  Oid expr_coll;
2705  Index index_relid;
2706  Oid opfamily;
2707  Oid idxcollation;
2708 
2709  /* We only accept ANY clauses, not ALL */
2710  if (!saop->useOr)
2711  return NULL;
2712  leftop = (Node *) linitial(saop->args);
2713  rightop = (Node *) lsecond(saop->args);
2714  right_relids = pull_varnos(root, rightop);
2715  expr_op = saop->opno;
2716  expr_coll = saop->inputcollid;
2717 
2718  index_relid = index->rel->relid;
2719  opfamily = index->opfamily[indexcol];
2720  idxcollation = index->indexcollations[indexcol];
2721 
2722  /*
2723  * We must have indexkey on the left and a pseudo-constant array argument.
2724  */
2725  if (match_index_to_operand(leftop, indexcol, index) &&
2726  !bms_is_member(index_relid, right_relids) &&
2727  !contain_volatile_functions(rightop))
2728  {
2729  if (IndexCollMatchesExprColl(idxcollation, expr_coll) &&
2730  op_in_opfamily(expr_op, opfamily))
2731  {
2732  IndexClause *iclause = makeNode(IndexClause);
2733 
2734  iclause->rinfo = rinfo;
2735  iclause->indexquals = list_make1(rinfo);
2736  iclause->lossy = false;
2737  iclause->indexcol = indexcol;
2738  iclause->indexcols = NIL;
2739  return iclause;
2740  }
2741 
2742  /*
2743  * We do not currently ask support functions about ScalarArrayOpExprs,
2744  * though in principle we could.
2745  */
2746  }
2747 
2748  return NULL;
2749 }
2750 
2751 /*
2752  * match_rowcompare_to_indexcol()
2753  * Handles the RowCompareExpr case for match_clause_to_indexcol(),
2754  * which see for comments.
2755  *
2756  * In this routine we check whether the first column of the row comparison
2757  * matches the target index column. This is sufficient to guarantee that some
2758  * index condition can be constructed from the RowCompareExpr --- the rest
2759  * is handled by expand_indexqual_rowcompare().
2760  */
2761 static IndexClause *
2762 match_rowcompare_to_indexcol(PlannerInfo *root,
2763  RestrictInfo *rinfo,
2764  int indexcol,
2765  IndexOptInfo *index)
2766 {
2767  RowCompareExpr *clause = (RowCompareExpr *) rinfo->clause;
2768  Index index_relid;
2769  Oid opfamily;
2770  Oid idxcollation;
2771  Node *leftop,
2772  *rightop;
2773  bool var_on_left;
2774  Oid expr_op;
2775  Oid expr_coll;
2776 
2777  /* Forget it if we're not dealing with a btree index */
2778  if (index->relam != BTREE_AM_OID)
2779  return NULL;
2780 
2781  index_relid = index->rel->relid;
2782  opfamily = index->opfamily[indexcol];
2783  idxcollation = index->indexcollations[indexcol];
2784 
2785  /*
2786  * We could do the matching on the basis of insisting that the opfamily
2787  * shown in the RowCompareExpr be the same as the index column's opfamily,
2788  * but that could fail in the presence of reverse-sort opfamilies: it'd be
2789  * a matter of chance whether RowCompareExpr had picked the forward or
2790  * reverse-sort family. So look only at the operator, and match if it is
2791  * a member of the index's opfamily (after commutation, if the indexkey is
2792  * on the right). We'll worry later about whether any additional
2793  * operators are matchable to the index.
2794  */
2795  leftop = (Node *) linitial(clause->largs);
2796  rightop = (Node *) linitial(clause->rargs);
2797  expr_op = linitial_oid(clause->opnos);
2798  expr_coll = linitial_oid(clause->inputcollids);
2799 
2800  /* Collations must match, if relevant */
2801  if (!IndexCollMatchesExprColl(idxcollation, expr_coll))
2802  return NULL;
2803 
2804  /*
2805  * These syntactic tests are the same as in match_opclause_to_indexcol()
2806  */
2807  if (match_index_to_operand(leftop, indexcol, index) &&
2808  !bms_is_member(index_relid, pull_varnos(root, rightop)) &&
2809  !contain_volatile_functions(rightop))
2810  {
2811  /* OK, indexkey is on left */
2812  var_on_left = true;
2813  }
2814  else if (match_index_to_operand(rightop, indexcol, index) &&
2815  !bms_is_member(index_relid, pull_varnos(root, leftop)) &&
2816  !contain_volatile_functions(leftop))
2817  {
2818  /* indexkey is on right, so commute the operator */
2819  expr_op = get_commutator(expr_op);
2820  if (expr_op == InvalidOid)
2821  return NULL;
2822  var_on_left = false;
2823  }
2824  else
2825  return NULL;
2826 
2827  /* We're good if the operator is the right type of opfamily member */
2828  switch (get_op_opfamily_strategy(expr_op, opfamily))
2829  {
2830  case BTLessStrategyNumber:
2831  case BTLessEqualStrategyNumber:
2832  case BTGreaterEqualStrategyNumber:
2833  case BTGreaterStrategyNumber:
2834  return expand_indexqual_rowcompare(root,
2835  rinfo,
2836  indexcol,
2837  index,
2838  expr_op,
2839  var_on_left);
2840  }
2841 
2842  return NULL;
2843 }
2844 
2845 /*
2846  * expand_indexqual_rowcompare --- expand a single indexqual condition
2847  * that is a RowCompareExpr
2848  *
2849  * It's already known that the first column of the row comparison matches
2850  * the specified column of the index. We can use additional columns of the
2851  * row comparison as index qualifications, so long as they match the index
2852  * in the "same direction", ie, the indexkeys are all on the same side of the
2853  * clause and the operators are all the same-type members of the opfamilies.
2854  *
2855  * If all the columns of the RowCompareExpr match in this way, we just use it
2856  * as-is, except for possibly commuting it to put the indexkeys on the left.
2857  *
2858  * Otherwise, we build a shortened RowCompareExpr (if more than one
2859  * column matches) or a simple OpExpr (if the first-column match is all
2860  * there is). In these cases the modified clause is always "<=" or ">="
2861  * even when the original was "<" or ">" --- this is necessary to match all
2862  * the rows that could match the original. (We are building a lossy version
2863  * of the row comparison when we do this, so we set lossy = true.)
2864  *
2865  * Note: this is really just the last half of match_rowcompare_to_indexcol,
2866  * but we split it out for comprehensibility.
2867  */
2868 static IndexClause *
2869 expand_indexqual_rowcompare(PlannerInfo *root,
2870  RestrictInfo *rinfo,
2871  int indexcol,
2872  IndexOptInfo *index,
2873  Oid expr_op,
2874  bool var_on_left)
2875 {
2876  IndexClause *iclause = makeNode(IndexClause);
2877  RowCompareExpr *clause = (RowCompareExpr *) rinfo->clause;
2878  int op_strategy;
2879  Oid op_lefttype;
2880  Oid op_righttype;
2881  int matching_cols;
2882  List *expr_ops;
2883  List *opfamilies;
2884  List *lefttypes;
2885  List *righttypes;
2886  List *new_ops;
2887  List *var_args;
2888  List *non_var_args;
2889 
2890  iclause->rinfo = rinfo;
2891  iclause->indexcol = indexcol;
2892 
2893  if (var_on_left)
2894  {
2895  var_args = clause->largs;
2896  non_var_args = clause->rargs;
2897  }
2898  else
2899  {
2900  var_args = clause->rargs;
2901  non_var_args = clause->largs;
2902  }
2903 
2904  get_op_opfamily_properties(expr_op, index->opfamily[indexcol], false,
2905  &op_strategy,
2906  &op_lefttype,
2907  &op_righttype);
2908 
2909  /* Initialize returned list of which index columns are used */
2910  iclause->indexcols = list_make1_int(indexcol);
2911 
2912  /* Build lists of ops, opfamilies and operator datatypes in case needed */
2913  expr_ops = list_make1_oid(expr_op);
2914  opfamilies = list_make1_oid(index->opfamily[indexcol]);
2915  lefttypes = list_make1_oid(op_lefttype);
2916  righttypes = list_make1_oid(op_righttype);
2917 
2918  /*
2919  * See how many of the remaining columns match some index column in the
2920  * same way. As in match_clause_to_indexcol(), the "other" side of any
2921  * potential index condition is OK as long as it doesn't use Vars from the
2922  * indexed relation.
2923  */
2924  matching_cols = 1;
2925 
2926  while (matching_cols < list_length(var_args))
2927  {
2928  Node *varop = (Node *) list_nth(var_args, matching_cols);
2929  Node *constop = (Node *) list_nth(non_var_args, matching_cols);
2930  int i;
2931 
2932  expr_op = list_nth_oid(clause->opnos, matching_cols);
2933  if (!var_on_left)
2934  {
2935  /* indexkey is on right, so commute the operator */
2936  expr_op = get_commutator(expr_op);
2937  if (expr_op == InvalidOid)
2938  break; /* operator is not usable */
2939  }
2940  if (bms_is_member(index->rel->relid, pull_varnos(root, constop)))
2941  break; /* no good, Var on wrong side */
2942  if (contain_volatile_functions(constop))
2943  break; /* no good, volatile comparison value */
2944 
2945  /*
2946  * The Var side can match any key column of the index.
2947  */
2948  for (i = 0; i < index->nkeycolumns; i++)
2949  {
2950  if (match_index_to_operand(varop, i, index) &&
2951  get_op_opfamily_strategy(expr_op,
2952  index->opfamily[i]) == op_strategy &&
2953  IndexCollMatchesExprColl(index->indexcollations[i],
2954  list_nth_oid(clause->inputcollids,
2955  matching_cols)))
2956  break;
2957  }
2958  if (i >= index->nkeycolumns)
2959  break; /* no match found */
2960 
2961  /* Add column number to returned list */
2962  iclause->indexcols = lappend_int(iclause->indexcols, i);
2963 
2964  /* Add operator info to lists */
2965  get_op_opfamily_properties(expr_op, index->opfamily[i], false,
2966  &op_strategy,
2967  &op_lefttype,
2968  &op_righttype);
2969  expr_ops = lappend_oid(expr_ops, expr_op);
2970  opfamilies = lappend_oid(opfamilies, index->opfamily[i]);
2971  lefttypes = lappend_oid(lefttypes, op_lefttype);
2972  righttypes = lappend_oid(righttypes, op_righttype);
2973 
2974  /* This column matches, keep scanning */
2975  matching_cols++;
2976  }
2977 
2978  /* Result is non-lossy if all columns are usable as index quals */
2979  iclause->lossy = (matching_cols != list_length(clause->opnos));
2980 
2981  /*
2982  * We can use rinfo->clause as-is if we have var on left and it's all
2983  * usable as index quals.
2984  */
2985  if (var_on_left && !iclause->lossy)
2986  iclause->indexquals = list_make1(rinfo);
2987  else
2988  {
2989  /*
2990  * We have to generate a modified rowcompare (possibly just one
2991  * OpExpr). The painful part of this is changing < to <= or > to >=,
2992  * so deal with that first.
2993  */
2994  if (!iclause->lossy)
2995  {
2996  /* very easy, just use the commuted operators */
2997  new_ops = expr_ops;
2998  }
2999  else if (op_strategy == BTLessEqualStrategyNumber ||
3000  op_strategy == BTGreaterEqualStrategyNumber)
3001  {
3002  /* easy, just use the same (possibly commuted) operators */
3003  new_ops = list_truncate(expr_ops, matching_cols);
3004  }
3005  else
3006  {
3007  ListCell *opfamilies_cell;
3008  ListCell *lefttypes_cell;
3009  ListCell *righttypes_cell;
3010 
3011  if (op_strategy == BTLessStrategyNumber)
3012  op_strategy = BTLessEqualStrategyNumber;
3013  else if (op_strategy == BTGreaterStrategyNumber)
3014  op_strategy = BTGreaterEqualStrategyNumber;
3015  else
3016  elog(ERROR, "unexpected strategy number %d", op_strategy);
3017  new_ops = NIL;
3018  forthree(opfamilies_cell, opfamilies,
3019  lefttypes_cell, lefttypes,
3020  righttypes_cell, righttypes)
3021  {
3022  Oid opfam = lfirst_oid(opfamilies_cell);
3023  Oid lefttype = lfirst_oid(lefttypes_cell);
3024  Oid righttype = lfirst_oid(righttypes_cell);
3025 
3026  expr_op = get_opfamily_member(opfam, lefttype, righttype,
3027  op_strategy);
3028  if (!OidIsValid(expr_op)) /* should not happen */
3029  elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
3030  op_strategy, lefttype, righttype, opfam);
3031  new_ops = lappend_oid(new_ops, expr_op);
3032  }
3033  }
3034 
3035  /* If we have more than one matching col, create a subset rowcompare */
3036  if (matching_cols > 1)
3037  {
3038  RowCompareExpr *rc = makeNode(RowCompareExpr);
3039 
3040  rc->rctype = (RowCompareType) op_strategy;
3041  rc->opnos = new_ops;
3042  rc->opfamilies = list_truncate(list_copy(clause->opfamilies),
3043  matching_cols);
3044  rc->inputcollids = list_truncate(list_copy(clause->inputcollids),
3045  matching_cols);
3046  rc->largs = list_truncate(copyObject(var_args),
3047  matching_cols);
3048  rc->rargs = list_truncate(copyObject(non_var_args),
3049  matching_cols);
3050  iclause->indexquals = list_make1(make_simple_restrictinfo(root,
3051  (Expr *) rc));
3052  }
3053  else
3054  {
3055  Expr *op;
3056 
3057  /* We don't report an index column list in this case */
3058  iclause->indexcols = NIL;
3059 
3060  op = make_opclause(linitial_oid(new_ops), BOOLOID, false,
3061  copyObject(linitial(var_args)),
3062  copyObject(linitial(non_var_args)),
3063  InvalidOid,
3064  linitial_oid(clause->inputcollids));
3065  iclause->indexquals = list_make1(make_simple_restrictinfo(root, op));
3066  }
3067  }
3068 
3069  return iclause;
3070 }
3071 
3072 
3073 /****************************************************************************
3074  * ---- ROUTINES TO CHECK ORDERING OPERATORS ----
3075  ****************************************************************************/
3076 
3077 /*
3078  * match_pathkeys_to_index
3079  * Test whether an index can produce output ordered according to the
3080  * given pathkeys using "ordering operators".
3081  *
3082  * If it can, return a list of suitable ORDER BY expressions, each of the form
3083  * "indexedcol operator pseudoconstant", along with an integer list of the
3084  * index column numbers (zero based) that each clause would be used with.
3085  * NIL lists are returned if the ordering is not achievable this way.
3086  *
3087  * On success, the result list is ordered by pathkeys, and in fact is
3088  * one-to-one with the requested pathkeys.
3089  */
3090 static void
3091 match_pathkeys_to_index(IndexOptInfo *index, List *pathkeys,
3092  List **orderby_clauses_p,
3093  List **clause_columns_p)
3094 {
3095  List *orderby_clauses = NIL;
3096  List *clause_columns = NIL;
3097  ListCell *lc1;
3098 
3099  *orderby_clauses_p = NIL; /* set default results */
3100  *clause_columns_p = NIL;
3101 
3102  /* Only indexes with the amcanorderbyop property are interesting here */
3103  if (!index->amcanorderbyop)
3104  return;
3105 
3106  foreach(lc1, pathkeys)
3107  {
3108  PathKey *pathkey = (PathKey *) lfirst(lc1);
3109  bool found = false;
3110  ListCell *lc2;
3111 
3112  /*
3113  * Note: for any failure to match, we just return NIL immediately.
3114  * There is no value in matching just some of the pathkeys.
3115  */
3116 
3117  /* Pathkey must request default sort order for the target opfamily */
3118  if (pathkey->pk_strategy != BTLessStrategyNumber ||
3119  pathkey->pk_nulls_first)
3120  return;
3121 
3122  /* If eclass is volatile, no hope of using an indexscan */
3123  if (pathkey->pk_eclass->ec_has_volatile)
3124  return;
3125 
3126  /*
3127  * Try to match eclass member expression(s) to index. Note that child
3128  * EC members are considered, but only when they belong to the target
3129  * relation. (Unlike regular members, the same expression could be a
3130  * child member of more than one EC. Therefore, the same index could
3131  * be considered to match more than one pathkey list, which is OK
3132  * here. See also get_eclass_for_sort_expr.)
3133  */
3134  foreach(lc2, pathkey->pk_eclass->ec_members)
3135  {
3136  EquivalenceMember *member = (EquivalenceMember *) lfirst(lc2);
3137  int indexcol;
3138 
3139  /* No possibility of match if it references other relations */
3140  if (!bms_equal(member->em_relids, index->rel->relids))
3141  continue;
3142 
3143  /*
3144  * We allow any column of the index to match each pathkey; they
3145  * don't have to match left-to-right as you might expect. This is
3146  * correct for GiST, and it doesn't matter for SP-GiST because
3147  * that doesn't handle multiple columns anyway, and no other
3148  * existing AMs support amcanorderbyop. We might need different
3149  * logic in future for other implementations.
3150  */
3151  for (indexcol = 0; indexcol < index->nkeycolumns; indexcol++)
3152  {
3153  Expr *expr;
3154 
3155  expr = match_clause_to_ordering_op(index,
3156  indexcol,
3157  member->em_expr,
3158  pathkey->pk_opfamily);
3159  if (expr)
3160  {
3161  orderby_clauses = lappend(orderby_clauses, expr);
3162  clause_columns = lappend_int(clause_columns, indexcol);
3163  found = true;
3164  break;
3165  }
3166  }
3167 
3168  if (found) /* don't want to look at remaining members */
3169  break;
3170  }
3171 
3172  if (!found) /* fail if no match for this pathkey */
3173  return;
3174  }
3175 
3176  *orderby_clauses_p = orderby_clauses; /* success! */
3177  *clause_columns_p = clause_columns;
3178 }
3179 
3180 /*
3181  * match_clause_to_ordering_op
3182  * Determines whether an ordering operator expression matches an
3183  * index column.
3184  *
3185  * This is similar to, but simpler than, match_clause_to_indexcol.
3186  * We only care about simple OpExpr cases. The input is a bare
3187  * expression that is being ordered by, which must be of the form
3188  * (indexkey op const) or (const op indexkey) where op is an ordering
3189  * operator for the column's opfamily.
3190  *
3191  * 'index' is the index of interest.
3192  * 'indexcol' is a column number of 'index' (counting from 0).
3193  * 'clause' is the ordering expression to be tested.
3194  * 'pk_opfamily' is the btree opfamily describing the required sort order.
3195  *
3196  * Note that we currently do not consider the collation of the ordering
3197  * operator's result. In practical cases the result type will be numeric
3198  * and thus have no collation, and it's not very clear what to match to
3199  * if it did have a collation. The index's collation should match the
3200  * ordering operator's input collation, not its result.
3201  *
3202  * If successful, return 'clause' as-is if the indexkey is on the left,
3203  * otherwise a commuted copy of 'clause'. If no match, return NULL.
3204  */
3205 static Expr *
3206 match_clause_to_ordering_op(IndexOptInfo *index,
3207  int indexcol,
3208  Expr *clause,
3209  Oid pk_opfamily)
3210 {
3211  Oid opfamily;
3212  Oid idxcollation;
3213  Node *leftop,
3214  *rightop;
3215  Oid expr_op;
3216  Oid expr_coll;
3217  Oid sortfamily;
3218  bool commuted;
3219 
3220  Assert(indexcol < index->nkeycolumns);
3221 
3222  opfamily = index->opfamily[indexcol];
3223  idxcollation = index->indexcollations[indexcol];
3224 
3225  /*
3226  * Clause must be a binary opclause.
3227  */
3228  if (!is_opclause(clause))
3229  return NULL;
3230  leftop = get_leftop(clause);
3231  rightop = get_rightop(clause);
3232  if (!leftop || !rightop)
3233  return NULL;
3234  expr_op = ((OpExpr *) clause)->opno;
3235  expr_coll = ((OpExpr *) clause)->inputcollid;
3236 
3237  /*
3238  * We can forget the whole thing right away if wrong collation.
3239  */
3240  if (!IndexCollMatchesExprColl(idxcollation, expr_coll))
3241  return NULL;
3242 
3243  /*
3244  * Check for clauses of the form: (indexkey operator constant) or
3245  * (constant operator indexkey).
3246  */
3247  if (match_index_to_operand(leftop, indexcol, index) &&
3248  !contain_var_clause(rightop) &&
3249  !contain_volatile_functions(rightop))
3250  {
3251  commuted = false;
3252  }
3253  else if (match_index_to_operand(rightop, indexcol, index) &&
3254  !contain_var_clause(leftop) &&
3255  !contain_volatile_functions(leftop))
3256  {
3257  /* Might match, but we need a commuted operator */
3258  expr_op = get_commutator(expr_op);
3259  if (expr_op == InvalidOid)
3260  return NULL;
3261  commuted = true;
3262  }
3263  else
3264  return NULL;
3265 
3266  /*
3267  * Is the (commuted) operator an ordering operator for the opfamily? And
3268  * if so, does it yield the right sorting semantics?
3269  */
3270  sortfamily = get_op_opfamily_sortfamily(expr_op, opfamily);
3271  if (sortfamily != pk_opfamily)
3272  return NULL;
3273 
3274  /* We have a match. Return clause or a commuted version thereof. */
3275  if (commuted)
3276  {
3277  OpExpr *newclause = makeNode(OpExpr);
3278 
3279  /* flat-copy all the fields of clause */
3280  memcpy(newclause, clause, sizeof(OpExpr));
3281 
3282  /* commute it */
3283  newclause->opno = expr_op;
3284  newclause->opfuncid = InvalidOid;
3285  newclause->args = list_make2(rightop, leftop);
3286 
3287  clause = (Expr *) newclause;
3288  }
3289 
3290  return clause;
3291 }
3292 
3293 
3294 /****************************************************************************
3295  * ---- ROUTINES TO DO PARTIAL INDEX PREDICATE TESTS ----
3296  ****************************************************************************/
3297 
3298 /*
3299  * check_index_predicates
3300  * Set the predicate-derived IndexOptInfo fields for each index
3301  * of the specified relation.
3302  *
3303  * predOK is set true if the index is partial and its predicate is satisfied
3304  * for this query, ie the query's WHERE clauses imply the predicate.
3305  *
3306  * indrestrictinfo is set to the relation's baserestrictinfo list less any
3307  * conditions that are implied by the index's predicate. (Obviously, for a
3308  * non-partial index, this is the same as baserestrictinfo.) Such conditions
3309  * can be dropped from the plan when using the index, in certain cases.
3310  *
3311  * At one time it was possible for this to get re-run after adding more
3312  * restrictions to the rel, thus possibly letting us prove more indexes OK.
3313  * That doesn't happen any more (at least not in the core code's usage),
3314  * but this code still supports it in case extensions want to mess with the
3315  * baserestrictinfo list. We assume that adding more restrictions can't make
3316  * an index not predOK. We must recompute indrestrictinfo each time, though,
3317  * to make sure any newly-added restrictions get into it if needed.
3318  */
3319 void
3320 check_index_predicates(PlannerInfo *root, RelOptInfo *rel)
3321 {
3322  List *clauselist;
3323  bool have_partial;
3324  bool is_target_rel;
3325  Relids otherrels;
3326  ListCell *lc;
3327 
3328  /* Indexes are available only on base or "other" member relations. */
3329  Assert(IS_SIMPLE_REL(rel));
3330 
3331  /*
3332  * Initialize the indrestrictinfo lists to be identical to
3333  * baserestrictinfo, and check whether there are any partial indexes. If
3334  * not, this is all we need to do.
3335  */
3336  have_partial = false;
3337  foreach(lc, rel->indexlist)
3338  {
3339  IndexOptInfo *index = (IndexOptInfo *) lfirst(lc);
3340 
3341  index->indrestrictinfo = rel->baserestrictinfo;
3342  if (index->indpred)
3343  have_partial = true;
3344  }
3345  if (!have_partial)
3346  return;
3347 
3348  /*
3349  * Construct a list of clauses that we can assume true for the purpose of
3350  * proving the index(es) usable. Restriction clauses for the rel are
3351  * always usable, and so are any join clauses that are "movable to" this
3352  * rel. Also, we can consider any EC-derivable join clauses (which must
3353  * be "movable to" this rel, by definition).
3354  */
3355  clauselist = list_copy(rel->baserestrictinfo);
3356 
3357  /* Scan the rel's join clauses */
3358  foreach(lc, rel->joininfo)
3359  {
3360  RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
3361 
3362  /* Check if clause can be moved to this rel */
3363  if (!join_clause_is_movable_to(rinfo, rel))
3364  continue;
3365 
3366  clauselist = lappend(clauselist, rinfo);
3367  }
3368 
3369  /*
3370  * Add on any equivalence-derivable join clauses. Computing the correct
3371  * relid sets for generate_join_implied_equalities is slightly tricky
3372  * because the rel could be a child rel rather than a true baserel, and in
3373  * that case we must remove its parents' relid(s) from all_baserels.
3374  */
3375  if (rel->reloptkind == RELOPT_OTHER_MEMBER_REL)
3376  otherrels = bms_difference(root->all_baserels,
3377  find_childrel_parents(root, rel));
3378  else
3379  otherrels = bms_difference(root->all_baserels, rel->relids);
3380 
3381  if (!bms_is_empty(otherrels))
3382  clauselist =
3383  list_concat(clauselist,
3384  generate_join_implied_equalities(root,
3385  bms_union(rel->relids,
3386  otherrels),
3387  otherrels,
3388  rel));
3389 
3390  /*
3391  * Normally we remove quals that are implied by a partial index's
3392  * predicate from indrestrictinfo, indicating that they need not be
3393  * checked explicitly by an indexscan plan using this index. However, if
3394  * the rel is a target relation of UPDATE/DELETE/SELECT FOR UPDATE, we
3395  * cannot remove such quals from the plan, because they need to be in the
3396  * plan so that they will be properly rechecked by EvalPlanQual testing.
3397  * Some day we might want to remove such quals from the main plan anyway
3398  * and pass them through to EvalPlanQual via a side channel; but for now,
3399  * we just don't remove implied quals at all for target relations.
3400  */
3401  is_target_rel = (bms_is_member(rel->relid, root->all_result_relids) ||
3402  get_plan_rowmark(root->rowMarks, rel->relid) != NULL);
3403 
3404  /*
3405  * Now try to prove each index predicate true, and compute the
3406  * indrestrictinfo lists for partial indexes. Note that we compute the
3407  * indrestrictinfo list even for non-predOK indexes; this might seem
3408  * wasteful, but we may be able to use such indexes in OR clauses, cf
3409  * generate_bitmap_or_paths().
3410  */
3411  foreach(lc, rel->indexlist)
3412  {
3413  IndexOptInfo *index = (IndexOptInfo *) lfirst(lc);
3414  ListCell *lcr;
3415 
3416  if (index->indpred == NIL)
3417  continue; /* ignore non-partial indexes here */
3418 
3419  if (!index->predOK) /* don't repeat work if already proven OK */
3420  index->predOK = predicate_implied_by(index->indpred, clauselist,
3421  false);
3422 
3423  /* If rel is an update target, leave indrestrictinfo as set above */
3424  if (is_target_rel)
3425  continue;
3426 
3427  /* Else compute indrestrictinfo as the non-implied quals */
3428  index->indrestrictinfo = NIL;
3429  foreach(lcr, rel->baserestrictinfo)
3430  {
3431  RestrictInfo *rinfo = (RestrictInfo *) lfirst(lcr);
3432 
3433  /* predicate_implied_by() assumes first arg is immutable */
3434  if (contain_mutable_functions((Node *) rinfo->clause) ||
3435  !predicate_implied_by(list_make1(rinfo->clause),
3436  index->indpred, false))
3437  index->indrestrictinfo = lappend(index->indrestrictinfo, rinfo);
3438  }
3439  }
3440 }
3441 
3442 /****************************************************************************
3443  * ---- ROUTINES TO CHECK EXTERNALLY-VISIBLE CONDITIONS ----
3444  ****************************************************************************/
3445 
3446 /*
3447  * ec_member_matches_indexcol
3448  * Test whether an EquivalenceClass member matches an index column.
3449  *
3450  * This is a callback for use by generate_implied_equalities_for_column.
3451  */
3452 static bool
3453 ec_member_matches_indexcol(PlannerInfo *root, RelOptInfo *rel,
3454  EquivalenceClass *ec, EquivalenceMember *em,
3455  void *arg)
3456 {
3457  IndexOptInfo *index = ((ec_member_matches_arg *) arg)->index;
3458  int indexcol = ((ec_member_matches_arg *) arg)->indexcol;
3459  Oid curFamily;
3460  Oid curCollation;
3461 
3462  Assert(indexcol < index->nkeycolumns);
3463 
3464  curFamily = index->opfamily[indexcol];
3465  curCollation = index->indexcollations[indexcol];
3466 
3467  /*
3468  * If it's a btree index, we can reject it if its opfamily isn't
3469  * compatible with the EC, since no clause generated from the EC could be
3470  * used with the index. For non-btree indexes, we can't easily tell
3471  * whether clauses generated from the EC could be used with the index, so
3472  * don't check the opfamily. This might mean we return "true" for a
3473  * useless EC, so we have to recheck the results of
3474  * generate_implied_equalities_for_column; see
3475  * match_eclass_clauses_to_index.
3476  */
3477  if (index->relam == BTREE_AM_OID &&
3478  !list_member_oid(ec->ec_opfamilies, curFamily))
3479  return false;
3480 
3481  /* We insist on collation match for all index types, though */
3482  if (!IndexCollMatchesExprColl(curCollation, ec->ec_collation))
3483  return false;
3484 
3485  return match_index_to_operand((Node *) em->em_expr, indexcol, index);
3486 }
3487 
3488 /*
3489  * relation_has_unique_index_for
3490  * Determine whether the relation provably has at most one row satisfying
3491  * a set of equality conditions, because the conditions constrain all
3492  * columns of some unique index.
3493  *
3494  * The conditions can be represented in either or both of two ways:
3495  * 1. A list of RestrictInfo nodes, where the caller has already determined
3496  * that each condition is a mergejoinable equality with an expression in
3497  * this relation on one side, and an expression not involving this relation
3498  * on the other. The transient outer_is_left flag is used to identify which
3499  * side we should look at: left side if outer_is_left is false, right side
3500  * if it is true.
3501  * 2. A list of expressions in this relation, and a corresponding list of
3502  * equality operators. The caller must have already checked that the operators
3503  * represent equality. (Note: the operators could be cross-type; the
3504  * expressions should correspond to their RHS inputs.)
3505  *
3506  * The caller need only supply equality conditions arising from joins;
3507  * this routine automatically adds in any usable baserestrictinfo clauses.
3508  * (Note that the passed-in restrictlist will be destructively modified!)
3509  */
3510 bool
3511 relation_has_unique_index_for(PlannerInfo *root, RelOptInfo *rel,
3512  List *restrictlist,
3513  List *exprlist, List *oprlist)
3514 {
3515  ListCell *ic;
3516 
3517  Assert(list_length(exprlist) == list_length(oprlist));
3518 
3519  /* Short-circuit if no indexes... */
3520  if (rel->indexlist == NIL)
3521  return false;
3522 
3523  /*
3524  * Examine the rel's restriction clauses for usable var = const clauses
3525  * that we can add to the restrictlist.
3526  */
3527  foreach(ic, rel->baserestrictinfo)
3528  {
3529  RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(ic);
3530 
3531  /*
3532  * Note: can_join won't be set for a restriction clause, but
3533  * mergeopfamilies will be if it has a mergejoinable operator and
3534  * doesn't contain volatile functions.
3535  */
3536  if (restrictinfo->mergeopfamilies == NIL)
3537  continue; /* not mergejoinable */
3538 
3539  /*
3540  * The clause certainly doesn't refer to anything but the given rel.
3541  * If either side is pseudoconstant then we can use it.
3542  */
3543  if (bms_is_empty(restrictinfo->left_relids))
3544  {
3545  /* righthand side is inner */
3546  restrictinfo->outer_is_left = true;
3547  }
3548  else if (bms_is_empty(restrictinfo->right_relids))
3549  {
3550  /* lefthand side is inner */
3551  restrictinfo->outer_is_left = false;
3552  }
3553  else
3554  continue;
3555 
3556  /* OK, add to list */
3557  restrictlist = lappend(restrictlist, restrictinfo);
3558  }
3559 
3560  /* Short-circuit the easy case */
3561  if (restrictlist == NIL && exprlist == NIL)
3562  return false;
3563 
3564  /* Examine each index of the relation ... */
3565  foreach(ic, rel->indexlist)
3566  {
3567  IndexOptInfo *ind = (IndexOptInfo *) lfirst(ic);
3568  int c;
3569 
3570  /*
3571  * If the index is not unique, or not immediately enforced, or if it's
3572  * a partial index that doesn't match the query, it's useless here.
3573  */
3574  if (!ind->unique || !ind->immediate ||
3575  (ind->indpred != NIL && !ind->predOK))
3576  continue;
3577 
3578  /*
3579  * Try to find each index column in the lists of conditions. This is
3580  * O(N^2) or worse, but we expect all the lists to be short.
3581  */
3582  for (c = 0; c < ind->nkeycolumns; c++)
3583  {
3584  bool matched = false;
3585  ListCell *lc;
3586  ListCell *lc2;
3587 
3588  foreach(lc, restrictlist)
3589  {
3590  RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
3591  Node *rexpr;
3592 
3593  /*
3594  * The condition's equality operator must be a member of the
3595  * index opfamily, else it is not asserting the right kind of
3596  * equality behavior for this index. We check this first
3597  * since it's probably cheaper than match_index_to_operand().
3598  */
3599  if (!list_member_oid(rinfo->mergeopfamilies, ind->opfamily[c]))
3600  continue;
3601 
3602  /*
3603  * XXX at some point we may need to check collations here too.
3604  * For the moment we assume all collations reduce to the same
3605  * notion of equality.
3606  */
3607 
3608  /* OK, see if the condition operand matches the index key */
3609  if (rinfo->outer_is_left)
3610  rexpr = get_rightop(rinfo->clause);
3611  else
3612  rexpr = get_leftop(rinfo->clause);
3613 
3614  if (match_index_to_operand(rexpr, c, ind))
3615  {
3616  matched = true; /* column is unique */
3617  break;
3618  }
3619  }
3620 
3621  if (matched)
3622  continue;
3623 
3624  forboth(lc, exprlist, lc2, oprlist)
3625  {
3626  Node *expr = (Node *) lfirst(lc);
3627  Oid opr = lfirst_oid(lc2);
3628 
3629  /* See if the expression matches the index key */
3630  if (!match_index_to_operand(expr, c, ind))
3631  continue;
3632 
3633  /*
3634  * The equality operator must be a member of the index
3635  * opfamily, else it is not asserting the right kind of
3636  * equality behavior for this index. We assume the caller
3637  * determined it is an equality operator, so we don't need to
3638  * check any more tightly than this.
3639  */
3640  if (!op_in_opfamily(opr, ind->opfamily[c]))
3641  continue;
3642 
3643  /*
3644  * XXX at some point we may need to check collations here too.
3645  * For the moment we assume all collations reduce to the same
3646  * notion of equality.
3647  */
3648 
3649  matched = true; /* column is unique */
3650  break;
3651  }
3652 
3653  if (!matched)
3654  break; /* no match; this index doesn't help us */
3655  }
3656 
3657  /* Matched all key columns of this index? */
3658  if (c == ind->nkeycolumns)
3659  return true;
3660  }
3661 
3662  return false;
3663 }
3664 
3665 /*
3666  * indexcol_is_bool_constant_for_query
3667  *
3668  * If an index column is constrained to have a constant value by the query's
3669  * WHERE conditions, then it's irrelevant for sort-order considerations.
3670  * Usually that means we have a restriction clause WHERE indexcol = constant,
3671  * which gets turned into an EquivalenceClass containing a constant, which
3672  * is recognized as redundant by build_index_pathkeys(). But if the index
3673  * column is a boolean variable (or expression), then we are not going to
3674  * see WHERE indexcol = constant, because expression preprocessing will have
3675  * simplified that to "WHERE indexcol" or "WHERE NOT indexcol". So we are not
3676  * going to have a matching EquivalenceClass (unless the query also contains
3677  * "ORDER BY indexcol"). To allow such cases to work the same as they would
3678  * for non-boolean values, this function is provided to detect whether the
3679  * specified index column matches a boolean restriction clause.
3680  */
3681 bool
3682 indexcol_is_bool_constant_for_query(PlannerInfo *root,
3683  IndexOptInfo *index,
3684  int indexcol)
3685 {
3686  ListCell *lc;
3687 
3688  /* If the index isn't boolean, we can't possibly get a match */
3689  if (!IsBooleanOpfamily(index->opfamily[indexcol]))
3690  return false;
3691 
3692  /* Check each restriction clause for the index's rel */
3693  foreach(lc, index->rel->baserestrictinfo)
3694  {
3695  RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
3696 
3697  /*
3698  * As in match_clause_to_indexcol, never match pseudoconstants to
3699  * indexes. (It might be semantically okay to do so here, but the
3700  * odds of getting a match are negligible, so don't waste the cycles.)
3701  */
3702  if (rinfo->pseudoconstant)
3703  continue;
3704 
3705  /* See if we can match the clause's expression to the index column */
3706  if (match_boolean_index_clause(root, rinfo, indexcol, index))
3707  return true;
3708  }
3709 
3710  return false;
3711 }
3712 
3713 
3714 /****************************************************************************
3715  * ---- ROUTINES TO CHECK OPERANDS ----
3716  ****************************************************************************/
3717 
3718 /*
3719  * match_index_to_operand()
3720  * Generalized test for a match between an index's key
3721  * and the operand on one side of a restriction or join clause.
3722  *
3723  * operand: the nodetree to be compared to the index
3724  * indexcol: the column number of the index (counting from 0)
3725  * index: the index of interest
3726  *
3727  * Note that we aren't interested in collations here; the caller must check
3728  * for a collation match, if it's dealing with an operator where that matters.
3729  *
3730  * This is exported for use in selfuncs.c.
3731  */
3732 bool
3733 match_index_to_operand(Node *operand,
3734  int indexcol,
3735  IndexOptInfo *index)
3736 {
3737  int indkey;
3738 
3739  /*
3740  * Ignore any RelabelType node above the operand. This is needed to be
3741  * able to apply indexscanning in binary-compatible-operator cases. Note:
3742  * we can assume there is at most one RelabelType node;
3743  * eval_const_expressions() will have simplified if more than one.
3744  */
3745  if (operand && IsA(operand, RelabelType))
3746  operand = (Node *) ((RelabelType *) operand)->arg;
3747 
3748  indkey = index->indexkeys[indexcol];
3749  if (indkey != 0)
3750  {
3751  /*
3752  * Simple index column; operand must be a matching Var.
3753  */
3754  if (operand && IsA(operand, Var) &&
3755  index->rel->relid == ((Var *) operand)->varno &&
3756  indkey == ((Var *) operand)->varattno)
3757  return true;
3758  }
3759  else
3760  {
3761  /*
3762  * Index expression; find the correct expression. (This search could
3763  * be avoided, at the cost of complicating all the callers of this
3764  * routine; doesn't seem worth it.)
3765  */
3766  ListCell *indexpr_item;
3767  int i;
3768  Node *indexkey;
3769 
3770  indexpr_item = list_head(index->indexprs);
3771  for (i = 0; i < indexcol; i++)
3772  {
3773  if (index->indexkeys[i] == 0)
3774  {
3775  if (indexpr_item == NULL)
3776  elog(ERROR, "wrong number of index expressions");
3777  indexpr_item = lnext(index->indexprs, indexpr_item);
3778  }
3779  }
3780  if (indexpr_item == NULL)
3781  elog(ERROR, "wrong number of index expressions");
3782  indexkey = (Node *) lfirst(indexpr_item);
3783 
3784  /*
3785  * Does it match the operand? Again, strip any relabeling.
3786  */
3787  if (indexkey && IsA(indexkey, RelabelType))
3788  indexkey = (Node *) ((RelabelType *) indexkey)->arg;
3789 
3790  if (equal(indexkey, operand))
3791  return true;
3792  }
3793 
3794  return false;
3795 }
3796 
3797 /*
3798  * is_pseudo_constant_for_index()
3799  * Test whether the given expression can be used as an indexscan
3800  * comparison value.
3801  *
3802  * An indexscan comparison value must not contain any volatile functions,
3803  * and it can't contain any Vars of the index's own table. Vars of
3804  * other tables are okay, though; in that case we'd be producing an
3805  * indexqual usable in a parameterized indexscan. This is, therefore,
3806  * a weaker condition than is_pseudo_constant_clause().
3807  *
3808  * This function is exported for use by planner support functions,
3809  * which will have available the IndexOptInfo, but not any RestrictInfo
3810  * infrastructure. It is making the same test made by functions above
3811  * such as match_opclause_to_indexcol(), but those rely where possible
3812  * on RestrictInfo information about variable membership.
3813  *
3814  * expr: the nodetree to be checked
3815  * index: the index of interest
3816  */
3817 bool
3818 is_pseudo_constant_for_index(PlannerInfo *root, Node *expr, IndexOptInfo *index)
3819 {
3820  /* pull_varnos is cheaper than volatility check, so do that first */
3821  if (bms_is_member(index->rel->relid, pull_varnos(root, expr)))
3822  return false; /* no good, contains Var of table */
3823  if (contain_volatile_functions(expr))
3824  return false; /* no good, volatile comparison value */
3825  return true;
3826 }
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Definition: nodes.h:670
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Definition: indxpath.c:433