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