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equivclass.c
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1 /*-------------------------------------------------------------------------
2  *
3  * equivclass.c
4  * Routines for managing EquivalenceClasses
5  *
6  * See src/backend/optimizer/README for discussion of EquivalenceClasses.
7  *
8  *
9  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
10  * Portions Copyright (c) 1994, Regents of the University of California
11  *
12  * IDENTIFICATION
13  * src/backend/optimizer/path/equivclass.c
14  *
15  *-------------------------------------------------------------------------
16  */
17 #include "postgres.h"
18 
19 #include <limits.h>
20 
21 #include "access/stratnum.h"
22 #include "catalog/pg_type.h"
23 #include "nodes/makefuncs.h"
24 #include "nodes/nodeFuncs.h"
25 #include "optimizer/appendinfo.h"
26 #include "optimizer/clauses.h"
27 #include "optimizer/optimizer.h"
28 #include "optimizer/pathnode.h"
29 #include "optimizer/paths.h"
30 #include "optimizer/planmain.h"
31 #include "optimizer/restrictinfo.h"
32 #include "rewrite/rewriteManip.h"
33 #include "utils/lsyscache.h"
34 
35 
36 static EquivalenceMember *add_eq_member(EquivalenceClass *ec,
37  Expr *expr, Relids relids,
38  JoinDomain *jdomain,
39  EquivalenceMember *parent,
40  Oid datatype);
41 static bool is_exprlist_member(Expr *node, List *exprs);
42 static void generate_base_implied_equalities_const(PlannerInfo *root,
43  EquivalenceClass *ec);
44 static void generate_base_implied_equalities_no_const(PlannerInfo *root,
45  EquivalenceClass *ec);
46 static void generate_base_implied_equalities_broken(PlannerInfo *root,
47  EquivalenceClass *ec);
48 static List *generate_join_implied_equalities_normal(PlannerInfo *root,
49  EquivalenceClass *ec,
50  Relids join_relids,
51  Relids outer_relids,
52  Relids inner_relids);
53 static List *generate_join_implied_equalities_broken(PlannerInfo *root,
54  EquivalenceClass *ec,
55  Relids nominal_join_relids,
56  Relids outer_relids,
57  Relids nominal_inner_relids,
58  RelOptInfo *inner_rel);
59 static Oid select_equality_operator(EquivalenceClass *ec,
60  Oid lefttype, Oid righttype);
61 static RestrictInfo *create_join_clause(PlannerInfo *root,
62  EquivalenceClass *ec, Oid opno,
63  EquivalenceMember *leftem,
64  EquivalenceMember *rightem,
65  EquivalenceClass *parent_ec);
66 static bool reconsider_outer_join_clause(PlannerInfo *root,
67  OuterJoinClauseInfo *ojcinfo,
68  bool outer_on_left);
69 static bool reconsider_full_join_clause(PlannerInfo *root,
70  OuterJoinClauseInfo *ojcinfo);
71 static JoinDomain *find_join_domain(PlannerInfo *root, Relids relids);
72 static Bitmapset *get_eclass_indexes_for_relids(PlannerInfo *root,
73  Relids relids);
74 static Bitmapset *get_common_eclass_indexes(PlannerInfo *root, Relids relids1,
75  Relids relids2);
76 
77 
78 /*
79  * process_equivalence
80  * The given clause has a mergejoinable operator and is not an outer-join
81  * qualification, so its two sides can be considered equal
82  * anywhere they are both computable; moreover that equality can be
83  * extended transitively. Record this knowledge in the EquivalenceClass
84  * data structure, if applicable. Returns true if successful, false if not
85  * (in which case caller should treat the clause as ordinary, not an
86  * equivalence).
87  *
88  * In some cases, although we cannot convert a clause into EquivalenceClass
89  * knowledge, we can still modify it to a more useful form than the original.
90  * Then, *p_restrictinfo will be replaced by a new RestrictInfo, which is what
91  * the caller should use for further processing.
92  *
93  * jdomain is the join domain within which the given clause was found.
94  * This limits the applicability of deductions from the EquivalenceClass,
95  * as described in optimizer/README.
96  *
97  * We reject proposed equivalence clauses if they contain leaky functions
98  * and have security_level above zero. The EC evaluation rules require us to
99  * apply certain tests at certain joining levels, and we can't tolerate
100  * delaying any test on security_level grounds. By rejecting candidate clauses
101  * that might require security delays, we ensure it's safe to apply an EC
102  * clause as soon as it's supposed to be applied.
103  *
104  * On success return, we have also initialized the clause's left_ec/right_ec
105  * fields to point to the EquivalenceClass representing it. This saves lookup
106  * effort later.
107  *
108  * Note: constructing merged EquivalenceClasses is a standard UNION-FIND
109  * problem, for which there exist better data structures than simple lists.
110  * If this code ever proves to be a bottleneck then it could be sped up ---
111  * but for now, simple is beautiful.
112  *
113  * Note: this is only called during planner startup, not during GEQO
114  * exploration, so we need not worry about whether we're in the right
115  * memory context.
116  */
117 bool
118 process_equivalence(PlannerInfo *root,
119  RestrictInfo **p_restrictinfo,
120  JoinDomain *jdomain)
121 {
122  RestrictInfo *restrictinfo = *p_restrictinfo;
123  Expr *clause = restrictinfo->clause;
124  Oid opno,
125  collation,
126  item1_type,
127  item2_type;
128  Expr *item1;
129  Expr *item2;
130  Relids item1_relids,
131  item2_relids;
132  List *opfamilies;
133  EquivalenceClass *ec1,
134  *ec2;
135  EquivalenceMember *em1,
136  *em2;
137  ListCell *lc1;
138  int ec2_idx;
139 
140  /* Should not already be marked as having generated an eclass */
141  Assert(restrictinfo->left_ec == NULL);
142  Assert(restrictinfo->right_ec == NULL);
143 
144  /* Reject if it is potentially postponable by security considerations */
145  if (restrictinfo->security_level > 0 && !restrictinfo->leakproof)
146  return false;
147 
148  /* Extract info from given clause */
149  Assert(is_opclause(clause));
150  opno = ((OpExpr *) clause)->opno;
151  collation = ((OpExpr *) clause)->inputcollid;
152  item1 = (Expr *) get_leftop(clause);
153  item2 = (Expr *) get_rightop(clause);
154  item1_relids = restrictinfo->left_relids;
155  item2_relids = restrictinfo->right_relids;
156 
157  /*
158  * Ensure both input expressions expose the desired collation (their types
159  * should be OK already); see comments for canonicalize_ec_expression.
160  */
161  item1 = canonicalize_ec_expression(item1,
162  exprType((Node *) item1),
163  collation);
164  item2 = canonicalize_ec_expression(item2,
165  exprType((Node *) item2),
166  collation);
167 
168  /*
169  * Clauses of the form X=X cannot be translated into EquivalenceClasses.
170  * We'd either end up with a single-entry EC, losing the knowledge that
171  * the clause was present at all, or else make an EC with duplicate
172  * entries, causing other issues.
173  */
174  if (equal(item1, item2))
175  {
176  /*
177  * If the operator is strict, then the clause can be treated as just
178  * "X IS NOT NULL". (Since we know we are considering a top-level
179  * qual, we can ignore the difference between FALSE and NULL results.)
180  * It's worth making the conversion because we'll typically get a much
181  * better selectivity estimate than we would for X=X.
182  *
183  * If the operator is not strict, we can't be sure what it will do
184  * with NULLs, so don't attempt to optimize it.
185  */
186  set_opfuncid((OpExpr *) clause);
187  if (func_strict(((OpExpr *) clause)->opfuncid))
188  {
189  NullTest *ntest = makeNode(NullTest);
190 
191  ntest->arg = item1;
192  ntest->nulltesttype = IS_NOT_NULL;
193  ntest->argisrow = false; /* correct even if composite arg */
194  ntest->location = -1;
195 
196  *p_restrictinfo =
197  make_restrictinfo(root,
198  (Expr *) ntest,
199  restrictinfo->is_pushed_down,
200  restrictinfo->has_clone,
201  restrictinfo->is_clone,
202  restrictinfo->pseudoconstant,
203  restrictinfo->security_level,
204  NULL,
205  restrictinfo->incompatible_relids,
206  restrictinfo->outer_relids);
207  }
208  return false;
209  }
210 
211  /*
212  * We use the declared input types of the operator, not exprType() of the
213  * inputs, as the nominal datatypes for opfamily lookup. This presumes
214  * that btree operators are always registered with amoplefttype and
215  * amoprighttype equal to their declared input types. We will need this
216  * info anyway to build EquivalenceMember nodes, and by extracting it now
217  * we can use type comparisons to short-circuit some equal() tests.
218  */
219  op_input_types(opno, &item1_type, &item2_type);
220 
221  opfamilies = restrictinfo->mergeopfamilies;
222 
223  /*
224  * Sweep through the existing EquivalenceClasses looking for matches to
225  * item1 and item2. These are the possible outcomes:
226  *
227  * 1. We find both in the same EC. The equivalence is already known, so
228  * there's nothing to do.
229  *
230  * 2. We find both in different ECs. Merge the two ECs together.
231  *
232  * 3. We find just one. Add the other to its EC.
233  *
234  * 4. We find neither. Make a new, two-entry EC.
235  *
236  * Note: since all ECs are built through this process or the similar
237  * search in get_eclass_for_sort_expr(), it's impossible that we'd match
238  * an item in more than one existing nonvolatile EC. So it's okay to stop
239  * at the first match.
240  */
241  ec1 = ec2 = NULL;
242  em1 = em2 = NULL;
243  ec2_idx = -1;
244  foreach(lc1, root->eq_classes)
245  {
246  EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
247  ListCell *lc2;
248 
249  /* Never match to a volatile EC */
250  if (cur_ec->ec_has_volatile)
251  continue;
252 
253  /*
254  * The collation has to match; check this first since it's cheaper
255  * than the opfamily comparison.
256  */
257  if (collation != cur_ec->ec_collation)
258  continue;
259 
260  /*
261  * A "match" requires matching sets of btree opfamilies. Use of
262  * equal() for this test has implications discussed in the comments
263  * for get_mergejoin_opfamilies().
264  */
265  if (!equal(opfamilies, cur_ec->ec_opfamilies))
266  continue;
267 
268  foreach(lc2, cur_ec->ec_members)
269  {
270  EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
271 
272  Assert(!cur_em->em_is_child); /* no children yet */
273 
274  /*
275  * Match constants only within the same JoinDomain (see
276  * optimizer/README).
277  */
278  if (cur_em->em_is_const && cur_em->em_jdomain != jdomain)
279  continue;
280 
281  if (!ec1 &&
282  item1_type == cur_em->em_datatype &&
283  equal(item1, cur_em->em_expr))
284  {
285  ec1 = cur_ec;
286  em1 = cur_em;
287  if (ec2)
288  break;
289  }
290 
291  if (!ec2 &&
292  item2_type == cur_em->em_datatype &&
293  equal(item2, cur_em->em_expr))
294  {
295  ec2 = cur_ec;
296  ec2_idx = foreach_current_index(lc1);
297  em2 = cur_em;
298  if (ec1)
299  break;
300  }
301  }
302 
303  if (ec1 && ec2)
304  break;
305  }
306 
307  /* Sweep finished, what did we find? */
308 
309  if (ec1 && ec2)
310  {
311  /* If case 1, nothing to do, except add to sources */
312  if (ec1 == ec2)
313  {
314  ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo);
315  ec1->ec_min_security = Min(ec1->ec_min_security,
316  restrictinfo->security_level);
317  ec1->ec_max_security = Max(ec1->ec_max_security,
318  restrictinfo->security_level);
319  /* mark the RI as associated with this eclass */
320  restrictinfo->left_ec = ec1;
321  restrictinfo->right_ec = ec1;
322  /* mark the RI as usable with this pair of EMs */
323  restrictinfo->left_em = em1;
324  restrictinfo->right_em = em2;
325  return true;
326  }
327 
328  /*
329  * Case 2: need to merge ec1 and ec2. This should never happen after
330  * the ECs have reached canonical state; otherwise, pathkeys could be
331  * rendered non-canonical by the merge, and relation eclass indexes
332  * would get broken by removal of an eq_classes list entry.
333  */
334  if (root->ec_merging_done)
335  elog(ERROR, "too late to merge equivalence classes");
336 
337  /*
338  * We add ec2's items to ec1, then set ec2's ec_merged link to point
339  * to ec1 and remove ec2 from the eq_classes list. We cannot simply
340  * delete ec2 because that could leave dangling pointers in existing
341  * PathKeys. We leave it behind with a link so that the merged EC can
342  * be found.
343  */
344  ec1->ec_members = list_concat(ec1->ec_members, ec2->ec_members);
345  ec1->ec_sources = list_concat(ec1->ec_sources, ec2->ec_sources);
346  ec1->ec_derives = list_concat(ec1->ec_derives, ec2->ec_derives);
347  ec1->ec_relids = bms_join(ec1->ec_relids, ec2->ec_relids);
348  ec1->ec_has_const |= ec2->ec_has_const;
349  /* can't need to set has_volatile */
350  ec1->ec_min_security = Min(ec1->ec_min_security,
351  ec2->ec_min_security);
352  ec1->ec_max_security = Max(ec1->ec_max_security,
353  ec2->ec_max_security);
354  ec2->ec_merged = ec1;
355  root->eq_classes = list_delete_nth_cell(root->eq_classes, ec2_idx);
356  /* just to avoid debugging confusion w/ dangling pointers: */
357  ec2->ec_members = NIL;
358  ec2->ec_sources = NIL;
359  ec2->ec_derives = NIL;
360  ec2->ec_relids = NULL;
361  ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo);
362  ec1->ec_min_security = Min(ec1->ec_min_security,
363  restrictinfo->security_level);
364  ec1->ec_max_security = Max(ec1->ec_max_security,
365  restrictinfo->security_level);
366  /* mark the RI as associated with this eclass */
367  restrictinfo->left_ec = ec1;
368  restrictinfo->right_ec = ec1;
369  /* mark the RI as usable with this pair of EMs */
370  restrictinfo->left_em = em1;
371  restrictinfo->right_em = em2;
372  }
373  else if (ec1)
374  {
375  /* Case 3: add item2 to ec1 */
376  em2 = add_eq_member(ec1, item2, item2_relids,
377  jdomain, NULL, item2_type);
378  ec1->ec_sources = lappend(ec1->ec_sources, restrictinfo);
379  ec1->ec_min_security = Min(ec1->ec_min_security,
380  restrictinfo->security_level);
381  ec1->ec_max_security = Max(ec1->ec_max_security,
382  restrictinfo->security_level);
383  /* mark the RI as associated with this eclass */
384  restrictinfo->left_ec = ec1;
385  restrictinfo->right_ec = ec1;
386  /* mark the RI as usable with this pair of EMs */
387  restrictinfo->left_em = em1;
388  restrictinfo->right_em = em2;
389  }
390  else if (ec2)
391  {
392  /* Case 3: add item1 to ec2 */
393  em1 = add_eq_member(ec2, item1, item1_relids,
394  jdomain, NULL, item1_type);
395  ec2->ec_sources = lappend(ec2->ec_sources, restrictinfo);
396  ec2->ec_min_security = Min(ec2->ec_min_security,
397  restrictinfo->security_level);
398  ec2->ec_max_security = Max(ec2->ec_max_security,
399  restrictinfo->security_level);
400  /* mark the RI as associated with this eclass */
401  restrictinfo->left_ec = ec2;
402  restrictinfo->right_ec = ec2;
403  /* mark the RI as usable with this pair of EMs */
404  restrictinfo->left_em = em1;
405  restrictinfo->right_em = em2;
406  }
407  else
408  {
409  /* Case 4: make a new, two-entry EC */
410  EquivalenceClass *ec = makeNode(EquivalenceClass);
411 
412  ec->ec_opfamilies = opfamilies;
413  ec->ec_collation = collation;
414  ec->ec_members = NIL;
415  ec->ec_sources = list_make1(restrictinfo);
416  ec->ec_derives = NIL;
417  ec->ec_relids = NULL;
418  ec->ec_has_const = false;
419  ec->ec_has_volatile = false;
420  ec->ec_broken = false;
421  ec->ec_sortref = 0;
422  ec->ec_min_security = restrictinfo->security_level;
423  ec->ec_max_security = restrictinfo->security_level;
424  ec->ec_merged = NULL;
425  em1 = add_eq_member(ec, item1, item1_relids,
426  jdomain, NULL, item1_type);
427  em2 = add_eq_member(ec, item2, item2_relids,
428  jdomain, NULL, item2_type);
429 
430  root->eq_classes = lappend(root->eq_classes, ec);
431 
432  /* mark the RI as associated with this eclass */
433  restrictinfo->left_ec = ec;
434  restrictinfo->right_ec = ec;
435  /* mark the RI as usable with this pair of EMs */
436  restrictinfo->left_em = em1;
437  restrictinfo->right_em = em2;
438  }
439 
440  return true;
441 }
442 
443 /*
444  * canonicalize_ec_expression
445  *
446  * This function ensures that the expression exposes the expected type and
447  * collation, so that it will be equal() to other equivalence-class expressions
448  * that it ought to be equal() to.
449  *
450  * The rule for datatypes is that the exposed type should match what it would
451  * be for an input to an operator of the EC's opfamilies; which is usually
452  * the declared input type of the operator, but in the case of polymorphic
453  * operators no relabeling is wanted (compare the behavior of parse_coerce.c).
454  * Expressions coming in from quals will generally have the right type
455  * already, but expressions coming from indexkeys may not (because they are
456  * represented without any explicit relabel in pg_index), and the same problem
457  * occurs for sort expressions (because the parser is likewise cavalier about
458  * putting relabels on them). Such cases will be binary-compatible with the
459  * real operators, so adding a RelabelType is sufficient.
460  *
461  * Also, the expression's exposed collation must match the EC's collation.
462  * This is important because in comparisons like "foo < bar COLLATE baz",
463  * only one of the expressions has the correct exposed collation as we receive
464  * it from the parser. Forcing both of them to have it ensures that all
465  * variant spellings of such a construct behave the same. Again, we can
466  * stick on a RelabelType to force the right exposed collation. (It might
467  * work to not label the collation at all in EC members, but this is risky
468  * since some parts of the system expect exprCollation() to deliver the
469  * right answer for a sort key.)
470  */
471 Expr *
472 canonicalize_ec_expression(Expr *expr, Oid req_type, Oid req_collation)
473 {
474  Oid expr_type = exprType((Node *) expr);
475 
476  /*
477  * For a polymorphic-input-type opclass, just keep the same exposed type.
478  * RECORD opclasses work like polymorphic-type ones for this purpose.
479  */
480  if (IsPolymorphicType(req_type) || req_type == RECORDOID)
481  req_type = expr_type;
482 
483  /*
484  * No work if the expression exposes the right type/collation already.
485  */
486  if (expr_type != req_type ||
487  exprCollation((Node *) expr) != req_collation)
488  {
489  /*
490  * If we have to change the type of the expression, set typmod to -1,
491  * since the new type may not have the same typmod interpretation.
492  * When we only have to change collation, preserve the exposed typmod.
493  */
494  int32 req_typmod;
495 
496  if (expr_type != req_type)
497  req_typmod = -1;
498  else
499  req_typmod = exprTypmod((Node *) expr);
500 
501  /*
502  * Use applyRelabelType so that we preserve const-flatness. This is
503  * important since eval_const_expressions has already been applied.
504  */
505  expr = (Expr *) applyRelabelType((Node *) expr,
506  req_type, req_typmod, req_collation,
507  COERCE_IMPLICIT_CAST, -1, false);
508  }
509 
510  return expr;
511 }
512 
513 /*
514  * add_eq_member - build a new EquivalenceMember and add it to an EC
515  */
516 static EquivalenceMember *
517 add_eq_member(EquivalenceClass *ec, Expr *expr, Relids relids,
518  JoinDomain *jdomain, EquivalenceMember *parent, Oid datatype)
519 {
520  EquivalenceMember *em = makeNode(EquivalenceMember);
521 
522  em->em_expr = expr;
523  em->em_relids = relids;
524  em->em_is_const = false;
525  em->em_is_child = (parent != NULL);
526  em->em_datatype = datatype;
527  em->em_jdomain = jdomain;
528  em->em_parent = parent;
529 
530  if (bms_is_empty(relids))
531  {
532  /*
533  * No Vars, assume it's a pseudoconstant. This is correct for entries
534  * generated from process_equivalence(), because a WHERE clause can't
535  * contain aggregates or SRFs, and non-volatility was checked before
536  * process_equivalence() ever got called. But
537  * get_eclass_for_sort_expr() has to work harder. We put the tests
538  * there not here to save cycles in the equivalence case.
539  */
540  Assert(!parent);
541  em->em_is_const = true;
542  ec->ec_has_const = true;
543  /* it can't affect ec_relids */
544  }
545  else if (!parent) /* child members don't add to ec_relids */
546  {
547  ec->ec_relids = bms_add_members(ec->ec_relids, relids);
548  }
549  ec->ec_members = lappend(ec->ec_members, em);
550 
551  return em;
552 }
553 
554 
555 /*
556  * get_eclass_for_sort_expr
557  * Given an expression and opfamily/collation info, find an existing
558  * equivalence class it is a member of; if none, optionally build a new
559  * single-member EquivalenceClass for it.
560  *
561  * sortref is the SortGroupRef of the originating SortGroupClause, if any,
562  * or zero if not. (It should never be zero if the expression is volatile!)
563  *
564  * If rel is not NULL, it identifies a specific relation we're considering
565  * a path for, and indicates that child EC members for that relation can be
566  * considered. Otherwise child members are ignored. (Note: since child EC
567  * members aren't guaranteed unique, a non-NULL value means that there could
568  * be more than one EC that matches the expression; if so it's order-dependent
569  * which one you get. This is annoying but it only happens in corner cases,
570  * so for now we live with just reporting the first match. See also
571  * generate_implied_equalities_for_column and match_pathkeys_to_index.)
572  *
573  * If create_it is true, we'll build a new EquivalenceClass when there is no
574  * match. If create_it is false, we just return NULL when no match.
575  *
576  * This can be used safely both before and after EquivalenceClass merging;
577  * since it never causes merging it does not invalidate any existing ECs
578  * or PathKeys. However, ECs added after path generation has begun are
579  * of limited usefulness, so usually it's best to create them beforehand.
580  *
581  * Note: opfamilies must be chosen consistently with the way
582  * process_equivalence() would do; that is, generated from a mergejoinable
583  * equality operator. Else we might fail to detect valid equivalences,
584  * generating poor (but not incorrect) plans.
585  */
586 EquivalenceClass *
587 get_eclass_for_sort_expr(PlannerInfo *root,
588  Expr *expr,
589  List *opfamilies,
590  Oid opcintype,
591  Oid collation,
592  Index sortref,
593  Relids rel,
594  bool create_it)
595 {
596  JoinDomain *jdomain;
597  Relids expr_relids;
598  EquivalenceClass *newec;
599  EquivalenceMember *newem;
600  ListCell *lc1;
601  MemoryContext oldcontext;
602 
603  /*
604  * Ensure the expression exposes the correct type and collation.
605  */
606  expr = canonicalize_ec_expression(expr, opcintype, collation);
607 
608  /*
609  * Since SortGroupClause nodes are top-level expressions (GROUP BY, ORDER
610  * BY, etc), they can be presumed to belong to the top JoinDomain.
611  */
612  jdomain = linitial_node(JoinDomain, root->join_domains);
613 
614  /*
615  * Scan through the existing EquivalenceClasses for a match
616  */
617  foreach(lc1, root->eq_classes)
618  {
619  EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
620  ListCell *lc2;
621 
622  /*
623  * Never match to a volatile EC, except when we are looking at another
624  * reference to the same volatile SortGroupClause.
625  */
626  if (cur_ec->ec_has_volatile &&
627  (sortref == 0 || sortref != cur_ec->ec_sortref))
628  continue;
629 
630  if (collation != cur_ec->ec_collation)
631  continue;
632  if (!equal(opfamilies, cur_ec->ec_opfamilies))
633  continue;
634 
635  foreach(lc2, cur_ec->ec_members)
636  {
637  EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
638 
639  /*
640  * Ignore child members unless they match the request.
641  */
642  if (cur_em->em_is_child &&
643  !bms_equal(cur_em->em_relids, rel))
644  continue;
645 
646  /*
647  * Match constants only within the same JoinDomain (see
648  * optimizer/README).
649  */
650  if (cur_em->em_is_const && cur_em->em_jdomain != jdomain)
651  continue;
652 
653  if (opcintype == cur_em->em_datatype &&
654  equal(expr, cur_em->em_expr))
655  {
656  /*
657  * Match!
658  *
659  * Copy the sortref if it wasn't set yet. That may happen if
660  * the ec was constructed from a WHERE clause, i.e. it doesn't
661  * have a target reference at all.
662  */
663  if (cur_ec->ec_sortref == 0 && sortref > 0)
664  cur_ec->ec_sortref = sortref;
665  return cur_ec;
666  }
667  }
668  }
669 
670  /* No match; does caller want a NULL result? */
671  if (!create_it)
672  return NULL;
673 
674  /*
675  * OK, build a new single-member EC
676  *
677  * Here, we must be sure that we construct the EC in the right context.
678  */
679  oldcontext = MemoryContextSwitchTo(root->planner_cxt);
680 
681  newec = makeNode(EquivalenceClass);
682  newec->ec_opfamilies = list_copy(opfamilies);
683  newec->ec_collation = collation;
684  newec->ec_members = NIL;
685  newec->ec_sources = NIL;
686  newec->ec_derives = NIL;
687  newec->ec_relids = NULL;
688  newec->ec_has_const = false;
689  newec->ec_has_volatile = contain_volatile_functions((Node *) expr);
690  newec->ec_broken = false;
691  newec->ec_sortref = sortref;
692  newec->ec_min_security = UINT_MAX;
693  newec->ec_max_security = 0;
694  newec->ec_merged = NULL;
695 
696  if (newec->ec_has_volatile && sortref == 0) /* should not happen */
697  elog(ERROR, "volatile EquivalenceClass has no sortref");
698 
699  /*
700  * Get the precise set of relids appearing in the expression.
701  */
702  expr_relids = pull_varnos(root, (Node *) expr);
703 
704  newem = add_eq_member(newec, copyObject(expr), expr_relids,
705  jdomain, NULL, opcintype);
706 
707  /*
708  * add_eq_member doesn't check for volatile functions, set-returning
709  * functions, aggregates, or window functions, but such could appear in
710  * sort expressions; so we have to check whether its const-marking was
711  * correct.
712  */
713  if (newec->ec_has_const)
714  {
715  if (newec->ec_has_volatile ||
716  expression_returns_set((Node *) expr) ||
717  contain_agg_clause((Node *) expr) ||
718  contain_window_function((Node *) expr))
719  {
720  newec->ec_has_const = false;
721  newem->em_is_const = false;
722  }
723  }
724 
725  root->eq_classes = lappend(root->eq_classes, newec);
726 
727  /*
728  * If EC merging is already complete, we have to mop up by adding the new
729  * EC to the eclass_indexes of the relation(s) mentioned in it.
730  */
731  if (root->ec_merging_done)
732  {
733  int ec_index = list_length(root->eq_classes) - 1;
734  int i = -1;
735 
736  while ((i = bms_next_member(newec->ec_relids, i)) > 0)
737  {
738  RelOptInfo *rel = root->simple_rel_array[i];
739 
740  if (rel == NULL) /* must be an outer join */
741  {
742  Assert(bms_is_member(i, root->outer_join_rels));
743  continue;
744  }
745 
746  Assert(rel->reloptkind == RELOPT_BASEREL);
747 
748  rel->eclass_indexes = bms_add_member(rel->eclass_indexes,
749  ec_index);
750  }
751  }
752 
753  MemoryContextSwitchTo(oldcontext);
754 
755  return newec;
756 }
757 
758 /*
759  * find_ec_member_matching_expr
760  * Locate an EquivalenceClass member matching the given expr, if any;
761  * return NULL if no match.
762  *
763  * "Matching" is defined as "equal after stripping RelabelTypes".
764  * This is used for identifying sort expressions, and we need to allow
765  * binary-compatible relabeling for some cases involving binary-compatible
766  * sort operators.
767  *
768  * Child EC members are ignored unless they belong to given 'relids'.
769  */
770 EquivalenceMember *
771 find_ec_member_matching_expr(EquivalenceClass *ec,
772  Expr *expr,
773  Relids relids)
774 {
775  ListCell *lc;
776 
777  /* We ignore binary-compatible relabeling on both ends */
778  while (expr && IsA(expr, RelabelType))
779  expr = ((RelabelType *) expr)->arg;
780 
781  foreach(lc, ec->ec_members)
782  {
783  EquivalenceMember *em = (EquivalenceMember *) lfirst(lc);
784  Expr *emexpr;
785 
786  /*
787  * We shouldn't be trying to sort by an equivalence class that
788  * contains a constant, so no need to consider such cases any further.
789  */
790  if (em->em_is_const)
791  continue;
792 
793  /*
794  * Ignore child members unless they belong to the requested rel.
795  */
796  if (em->em_is_child &&
797  !bms_is_subset(em->em_relids, relids))
798  continue;
799 
800  /*
801  * Match if same expression (after stripping relabel).
802  */
803  emexpr = em->em_expr;
804  while (emexpr && IsA(emexpr, RelabelType))
805  emexpr = ((RelabelType *) emexpr)->arg;
806 
807  if (equal(emexpr, expr))
808  return em;
809  }
810 
811  return NULL;
812 }
813 
814 /*
815  * find_computable_ec_member
816  * Locate an EquivalenceClass member that can be computed from the
817  * expressions appearing in "exprs"; return NULL if no match.
818  *
819  * "exprs" can be either a list of bare expression trees, or a list of
820  * TargetEntry nodes. Either way, it should contain Vars and possibly
821  * Aggrefs and WindowFuncs, which are matched to the corresponding elements
822  * of the EquivalenceClass's expressions.
823  *
824  * Unlike find_ec_member_matching_expr, there's no special provision here
825  * for binary-compatible relabeling. This is intentional: if we have to
826  * compute an expression in this way, setrefs.c is going to insist on exact
827  * matches of Vars to the source tlist.
828  *
829  * Child EC members are ignored unless they belong to given 'relids'.
830  * Also, non-parallel-safe expressions are ignored if 'require_parallel_safe'.
831  *
832  * Note: some callers pass root == NULL for notational reasons. This is OK
833  * when require_parallel_safe is false.
834  */
835 EquivalenceMember *
836 find_computable_ec_member(PlannerInfo *root,
837  EquivalenceClass *ec,
838  List *exprs,
839  Relids relids,
840  bool require_parallel_safe)
841 {
842  ListCell *lc;
843 
844  foreach(lc, ec->ec_members)
845  {
846  EquivalenceMember *em = (EquivalenceMember *) lfirst(lc);
847  List *exprvars;
848  ListCell *lc2;
849 
850  /*
851  * We shouldn't be trying to sort by an equivalence class that
852  * contains a constant, so no need to consider such cases any further.
853  */
854  if (em->em_is_const)
855  continue;
856 
857  /*
858  * Ignore child members unless they belong to the requested rel.
859  */
860  if (em->em_is_child &&
861  !bms_is_subset(em->em_relids, relids))
862  continue;
863 
864  /*
865  * Match if all Vars and quasi-Vars are available in "exprs".
866  */
867  exprvars = pull_var_clause((Node *) em->em_expr,
868  PVC_INCLUDE_AGGREGATES |
869  PVC_INCLUDE_WINDOWFUNCS |
870  PVC_INCLUDE_PLACEHOLDERS);
871  foreach(lc2, exprvars)
872  {
873  if (!is_exprlist_member(lfirst(lc2), exprs))
874  break;
875  }
876  list_free(exprvars);
877  if (lc2)
878  continue; /* we hit a non-available Var */
879 
880  /*
881  * If requested, reject expressions that are not parallel-safe. We
882  * check this last because it's a rather expensive test.
883  */
884  if (require_parallel_safe &&
885  !is_parallel_safe(root, (Node *) em->em_expr))
886  continue;
887 
888  return em; /* found usable expression */
889  }
890 
891  return NULL;
892 }
893 
894 /*
895  * is_exprlist_member
896  * Subroutine for find_computable_ec_member: is "node" in "exprs"?
897  *
898  * Per the requirements of that function, "exprs" might or might not have
899  * TargetEntry superstructure.
900  */
901 static bool
902 is_exprlist_member(Expr *node, List *exprs)
903 {
904  ListCell *lc;
905 
906  foreach(lc, exprs)
907  {
908  Expr *expr = (Expr *) lfirst(lc);
909 
910  if (expr && IsA(expr, TargetEntry))
911  expr = ((TargetEntry *) expr)->expr;
912 
913  if (equal(node, expr))
914  return true;
915  }
916  return false;
917 }
918 
919 /*
920  * relation_can_be_sorted_early
921  * Can this relation be sorted on this EC before the final output step?
922  *
923  * To succeed, we must find an EC member that prepare_sort_from_pathkeys knows
924  * how to sort on, given the rel's reltarget as input. There are also a few
925  * additional constraints based on the fact that the desired sort will be done
926  * "early", within the scan/join part of the plan. Also, non-parallel-safe
927  * expressions are ignored if 'require_parallel_safe'.
928  *
929  * At some point we might want to return the identified EquivalenceMember,
930  * but for now, callers only want to know if there is one.
931  */
932 bool
933 relation_can_be_sorted_early(PlannerInfo *root, RelOptInfo *rel,
934  EquivalenceClass *ec, bool require_parallel_safe)
935 {
936  PathTarget *target = rel->reltarget;
937  EquivalenceMember *em;
938  ListCell *lc;
939 
940  /*
941  * Reject volatile ECs immediately; such sorts must always be postponed.
942  */
943  if (ec->ec_has_volatile)
944  return false;
945 
946  /*
947  * Try to find an EM directly matching some reltarget member.
948  */
949  foreach(lc, target->exprs)
950  {
951  Expr *targetexpr = (Expr *) lfirst(lc);
952 
953  em = find_ec_member_matching_expr(ec, targetexpr, rel->relids);
954  if (!em)
955  continue;
956 
957  /*
958  * Reject expressions involving set-returning functions, as those
959  * can't be computed early either. (Note: this test and the following
960  * one are effectively checking properties of targetexpr, so there's
961  * no point in asking whether some other EC member would be better.)
962  */
963  if (expression_returns_set((Node *) em->em_expr))
964  continue;
965 
966  /*
967  * If requested, reject expressions that are not parallel-safe. We
968  * check this last because it's a rather expensive test.
969  */
970  if (require_parallel_safe &&
971  !is_parallel_safe(root, (Node *) em->em_expr))
972  continue;
973 
974  return true;
975  }
976 
977  /*
978  * Try to find an expression computable from the reltarget.
979  */
980  em = find_computable_ec_member(root, ec, target->exprs, rel->relids,
981  require_parallel_safe);
982  if (!em)
983  return false;
984 
985  /*
986  * Reject expressions involving set-returning functions, as those can't be
987  * computed early either. (There's no point in looking for another EC
988  * member in this case; since SRFs can't appear in WHERE, they cannot
989  * belong to multi-member ECs.)
990  */
991  if (expression_returns_set((Node *) em->em_expr))
992  return false;
993 
994  return true;
995 }
996 
997 /*
998  * generate_base_implied_equalities
999  * Generate any restriction clauses that we can deduce from equivalence
1000  * classes.
1001  *
1002  * When an EC contains pseudoconstants, our strategy is to generate
1003  * "member = const1" clauses where const1 is the first constant member, for
1004  * every other member (including other constants). If we are able to do this
1005  * then we don't need any "var = var" comparisons because we've successfully
1006  * constrained all the vars at their points of creation. If we fail to
1007  * generate any of these clauses due to lack of cross-type operators, we fall
1008  * back to the "ec_broken" strategy described below. (XXX if there are
1009  * multiple constants of different types, it's possible that we might succeed
1010  * in forming all the required clauses if we started from a different const
1011  * member; but this seems a sufficiently hokey corner case to not be worth
1012  * spending lots of cycles on.)
1013  *
1014  * For ECs that contain no pseudoconstants, we generate derived clauses
1015  * "member1 = member2" for each pair of members belonging to the same base
1016  * relation (actually, if there are more than two for the same base relation,
1017  * we only need enough clauses to link each to each other). This provides
1018  * the base case for the recursion: each row emitted by a base relation scan
1019  * will constrain all computable members of the EC to be equal. As each
1020  * join path is formed, we'll add additional derived clauses on-the-fly
1021  * to maintain this invariant (see generate_join_implied_equalities).
1022  *
1023  * If the opfamilies used by the EC do not provide complete sets of cross-type
1024  * equality operators, it is possible that we will fail to generate a clause
1025  * that must be generated to maintain the invariant. (An example: given
1026  * "WHERE a.x = b.y AND b.y = a.z", the scheme breaks down if we cannot
1027  * generate "a.x = a.z" as a restriction clause for A.) In this case we mark
1028  * the EC "ec_broken" and fall back to regurgitating its original source
1029  * RestrictInfos at appropriate times. We do not try to retract any derived
1030  * clauses already generated from the broken EC, so the resulting plan could
1031  * be poor due to bad selectivity estimates caused by redundant clauses. But
1032  * the correct solution to that is to fix the opfamilies ...
1033  *
1034  * Equality clauses derived by this function are passed off to
1035  * process_implied_equality (in plan/initsplan.c) to be inserted into the
1036  * restrictinfo datastructures. Note that this must be called after initial
1037  * scanning of the quals and before Path construction begins.
1038  *
1039  * We make no attempt to avoid generating duplicate RestrictInfos here: we
1040  * don't search ec_sources or ec_derives for matches. It doesn't really
1041  * seem worth the trouble to do so.
1042  */
1043 void
1044 generate_base_implied_equalities(PlannerInfo *root)
1045 {
1046  int ec_index;
1047  ListCell *lc;
1048 
1049  /*
1050  * At this point, we're done absorbing knowledge of equivalences in the
1051  * query, so no further EC merging should happen, and ECs remaining in the
1052  * eq_classes list can be considered canonical. (But note that it's still
1053  * possible for new single-member ECs to be added through
1054  * get_eclass_for_sort_expr().)
1055  */
1056  root->ec_merging_done = true;
1057 
1058  ec_index = 0;
1059  foreach(lc, root->eq_classes)
1060  {
1061  EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc);
1062  bool can_generate_joinclause = false;
1063  int i;
1064 
1065  Assert(ec->ec_merged == NULL); /* else shouldn't be in list */
1066  Assert(!ec->ec_broken); /* not yet anyway... */
1067 
1068  /*
1069  * Generate implied equalities that are restriction clauses.
1070  * Single-member ECs won't generate any deductions, either here or at
1071  * the join level.
1072  */
1073  if (list_length(ec->ec_members) > 1)
1074  {
1075  if (ec->ec_has_const)
1076  generate_base_implied_equalities_const(root, ec);
1077  else
1078  generate_base_implied_equalities_no_const(root, ec);
1079 
1080  /* Recover if we failed to generate required derived clauses */
1081  if (ec->ec_broken)
1082  generate_base_implied_equalities_broken(root, ec);
1083 
1084  /* Detect whether this EC might generate join clauses */
1085  can_generate_joinclause =
1086  (bms_membership(ec->ec_relids) == BMS_MULTIPLE);
1087  }
1088 
1089  /*
1090  * Mark the base rels cited in each eclass (which should all exist by
1091  * now) with the eq_classes indexes of all eclasses mentioning them.
1092  * This will let us avoid searching in subsequent lookups. While
1093  * we're at it, we can mark base rels that have pending eclass joins;
1094  * this is a cheap version of has_relevant_eclass_joinclause().
1095  */
1096  i = -1;
1097  while ((i = bms_next_member(ec->ec_relids, i)) > 0)
1098  {
1099  RelOptInfo *rel = root->simple_rel_array[i];
1100 
1101  if (rel == NULL) /* must be an outer join */
1102  {
1103  Assert(bms_is_member(i, root->outer_join_rels));
1104  continue;
1105  }
1106 
1107  Assert(rel->reloptkind == RELOPT_BASEREL);
1108 
1109  rel->eclass_indexes = bms_add_member(rel->eclass_indexes,
1110  ec_index);
1111 
1112  if (can_generate_joinclause)
1113  rel->has_eclass_joins = true;
1114  }
1115 
1116  ec_index++;
1117  }
1118 }
1119 
1120 /*
1121  * generate_base_implied_equalities when EC contains pseudoconstant(s)
1122  */
1123 static void
1124 generate_base_implied_equalities_const(PlannerInfo *root,
1125  EquivalenceClass *ec)
1126 {
1127  EquivalenceMember *const_em = NULL;
1128  ListCell *lc;
1129 
1130  /*
1131  * In the trivial case where we just had one "var = const" clause, push
1132  * the original clause back into the main planner machinery. There is
1133  * nothing to be gained by doing it differently, and we save the effort to
1134  * re-build and re-analyze an equality clause that will be exactly
1135  * equivalent to the old one.
1136  */
1137  if (list_length(ec->ec_members) == 2 &&
1138  list_length(ec->ec_sources) == 1)
1139  {
1140  RestrictInfo *restrictinfo = (RestrictInfo *) linitial(ec->ec_sources);
1141 
1142  distribute_restrictinfo_to_rels(root, restrictinfo);
1143  return;
1144  }
1145 
1146  /*
1147  * Find the constant member to use. We prefer an actual constant to
1148  * pseudo-constants (such as Params), because the constraint exclusion
1149  * machinery might be able to exclude relations on the basis of generated
1150  * "var = const" equalities, but "var = param" won't work for that.
1151  */
1152  foreach(lc, ec->ec_members)
1153  {
1154  EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
1155 
1156  if (cur_em->em_is_const)
1157  {
1158  const_em = cur_em;
1159  if (IsA(cur_em->em_expr, Const))
1160  break;
1161  }
1162  }
1163  Assert(const_em != NULL);
1164 
1165  /* Generate a derived equality against each other member */
1166  foreach(lc, ec->ec_members)
1167  {
1168  EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
1169  Oid eq_op;
1170  RestrictInfo *rinfo;
1171 
1172  Assert(!cur_em->em_is_child); /* no children yet */
1173  if (cur_em == const_em)
1174  continue;
1175  eq_op = select_equality_operator(ec,
1176  cur_em->em_datatype,
1177  const_em->em_datatype);
1178  if (!OidIsValid(eq_op))
1179  {
1180  /* failed... */
1181  ec->ec_broken = true;
1182  break;
1183  }
1184 
1185  /*
1186  * We use the constant's em_jdomain as qualscope, so that if the
1187  * generated clause is variable-free (i.e, both EMs are consts) it
1188  * will be enforced at the join domain level.
1189  */
1190  rinfo = process_implied_equality(root, eq_op, ec->ec_collation,
1191  cur_em->em_expr, const_em->em_expr,
1192  const_em->em_jdomain->jd_relids,
1193  ec->ec_min_security,
1194  cur_em->em_is_const);
1195 
1196  /*
1197  * If the clause didn't degenerate to a constant, fill in the correct
1198  * markings for a mergejoinable clause, and save it in ec_derives. (We
1199  * will not re-use such clauses directly, but selectivity estimation
1200  * may consult the list later. Note that this use of ec_derives does
1201  * not overlap with its use for join clauses, since we never generate
1202  * join clauses from an ec_has_const eclass.)
1203  */
1204  if (rinfo && rinfo->mergeopfamilies)
1205  {
1206  /* it's not redundant, so don't set parent_ec */
1207  rinfo->left_ec = rinfo->right_ec = ec;
1208  rinfo->left_em = cur_em;
1209  rinfo->right_em = const_em;
1210  ec->ec_derives = lappend(ec->ec_derives, rinfo);
1211  }
1212  }
1213 }
1214 
1215 /*
1216  * generate_base_implied_equalities when EC contains no pseudoconstants
1217  */
1218 static void
1219 generate_base_implied_equalities_no_const(PlannerInfo *root,
1220  EquivalenceClass *ec)
1221 {
1222  EquivalenceMember **prev_ems;
1223  ListCell *lc;
1224 
1225  /*
1226  * We scan the EC members once and track the last-seen member for each
1227  * base relation. When we see another member of the same base relation,
1228  * we generate "prev_em = cur_em". This results in the minimum number of
1229  * derived clauses, but it's possible that it will fail when a different
1230  * ordering would succeed. XXX FIXME: use a UNION-FIND algorithm similar
1231  * to the way we build merged ECs. (Use a list-of-lists for each rel.)
1232  */
1233  prev_ems = (EquivalenceMember **)
1234  palloc0(root->simple_rel_array_size * sizeof(EquivalenceMember *));
1235 
1236  foreach(lc, ec->ec_members)
1237  {
1238  EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
1239  int relid;
1240 
1241  Assert(!cur_em->em_is_child); /* no children yet */
1242  if (!bms_get_singleton_member(cur_em->em_relids, &relid))
1243  continue;
1244  Assert(relid < root->simple_rel_array_size);
1245 
1246  if (prev_ems[relid] != NULL)
1247  {
1248  EquivalenceMember *prev_em = prev_ems[relid];
1249  Oid eq_op;
1250  RestrictInfo *rinfo;
1251 
1252  eq_op = select_equality_operator(ec,
1253  prev_em->em_datatype,
1254  cur_em->em_datatype);
1255  if (!OidIsValid(eq_op))
1256  {
1257  /* failed... */
1258  ec->ec_broken = true;
1259  break;
1260  }
1261 
1262  /*
1263  * The expressions aren't constants, so the passed qualscope will
1264  * never be used to place the generated clause. We just need to
1265  * be sure it covers both expressions, which em_relids should do.
1266  */
1267  rinfo = process_implied_equality(root, eq_op, ec->ec_collation,
1268  prev_em->em_expr, cur_em->em_expr,
1269  cur_em->em_relids,
1270  ec->ec_min_security,
1271  false);
1272 
1273  /*
1274  * If the clause didn't degenerate to a constant, fill in the
1275  * correct markings for a mergejoinable clause. We don't put it
1276  * in ec_derives however; we don't currently need to re-find such
1277  * clauses, and we don't want to clutter that list with non-join
1278  * clauses.
1279  */
1280  if (rinfo && rinfo->mergeopfamilies)
1281  {
1282  /* it's not redundant, so don't set parent_ec */
1283  rinfo->left_ec = rinfo->right_ec = ec;
1284  rinfo->left_em = prev_em;
1285  rinfo->right_em = cur_em;
1286  }
1287  }
1288  prev_ems[relid] = cur_em;
1289  }
1290 
1291  pfree(prev_ems);
1292 
1293  /*
1294  * We also have to make sure that all the Vars used in the member clauses
1295  * will be available at any join node we might try to reference them at.
1296  * For the moment we force all the Vars to be available at all join nodes
1297  * for this eclass. Perhaps this could be improved by doing some
1298  * pre-analysis of which members we prefer to join, but it's no worse than
1299  * what happened in the pre-8.3 code.
1300  */
1301  foreach(lc, ec->ec_members)
1302  {
1303  EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
1304  List *vars = pull_var_clause((Node *) cur_em->em_expr,
1305  PVC_RECURSE_AGGREGATES |
1306  PVC_RECURSE_WINDOWFUNCS |
1307  PVC_INCLUDE_PLACEHOLDERS);
1308 
1309  add_vars_to_targetlist(root, vars, ec->ec_relids);
1310  list_free(vars);
1311  }
1312 }
1313 
1314 /*
1315  * generate_base_implied_equalities cleanup after failure
1316  *
1317  * What we must do here is push any zero- or one-relation source RestrictInfos
1318  * of the EC back into the main restrictinfo datastructures. Multi-relation
1319  * clauses will be regurgitated later by generate_join_implied_equalities().
1320  * (We do it this way to maintain continuity with the case that ec_broken
1321  * becomes set only after we've gone up a join level or two.) However, for
1322  * an EC that contains constants, we can adopt a simpler strategy and just
1323  * throw back all the source RestrictInfos immediately; that works because
1324  * we know that such an EC can't become broken later. (This rule justifies
1325  * ignoring ec_has_const ECs in generate_join_implied_equalities, even when
1326  * they are broken.)
1327  */
1328 static void
1329 generate_base_implied_equalities_broken(PlannerInfo *root,
1330  EquivalenceClass *ec)
1331 {
1332  ListCell *lc;
1333 
1334  foreach(lc, ec->ec_sources)
1335  {
1336  RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc);
1337 
1338  if (ec->ec_has_const ||
1339  bms_membership(restrictinfo->required_relids) != BMS_MULTIPLE)
1340  distribute_restrictinfo_to_rels(root, restrictinfo);
1341  }
1342 }
1343 
1344 
1345 /*
1346  * generate_join_implied_equalities
1347  * Generate any join clauses that we can deduce from equivalence classes.
1348  *
1349  * At a join node, we must enforce restriction clauses sufficient to ensure
1350  * that all equivalence-class members computable at that node are equal.
1351  * Since the set of clauses to enforce can vary depending on which subset
1352  * relations are the inputs, we have to compute this afresh for each join
1353  * relation pair. Hence a fresh List of RestrictInfo nodes is built and
1354  * passed back on each call.
1355  *
1356  * In addition to its use at join nodes, this can be applied to generate
1357  * eclass-based join clauses for use in a parameterized scan of a base rel.
1358  * The reason for the asymmetry of specifying the inner rel as a RelOptInfo
1359  * and the outer rel by Relids is that this usage occurs before we have
1360  * built any join RelOptInfos.
1361  *
1362  * An annoying special case for parameterized scans is that the inner rel can
1363  * be an appendrel child (an "other rel"). In this case we must generate
1364  * appropriate clauses using child EC members. add_child_rel_equivalences
1365  * must already have been done for the child rel.
1366  *
1367  * The results are sufficient for use in merge, hash, and plain nestloop join
1368  * methods. We do not worry here about selecting clauses that are optimal
1369  * for use in a parameterized indexscan. indxpath.c makes its own selections
1370  * of clauses to use, and if the ones we pick here are redundant with those,
1371  * the extras will be eliminated at createplan time, using the parent_ec
1372  * markers that we provide (see is_redundant_derived_clause()).
1373  *
1374  * Because the same join clauses are likely to be needed multiple times as
1375  * we consider different join paths, we avoid generating multiple copies:
1376  * whenever we select a particular pair of EquivalenceMembers to join,
1377  * we check to see if the pair matches any original clause (in ec_sources)
1378  * or previously-built clause (in ec_derives). This saves memory and allows
1379  * re-use of information cached in RestrictInfos. We also avoid generating
1380  * commutative duplicates, i.e. if the algorithm selects "a.x = b.y" but
1381  * we already have "b.y = a.x", we return the existing clause.
1382  *
1383  * If we are considering an outer join, sjinfo is the associated OJ info,
1384  * otherwise it can be NULL.
1385  *
1386  * join_relids should always equal bms_union(outer_relids, inner_rel->relids)
1387  * plus whatever add_outer_joins_to_relids() would add. We could simplify
1388  * this function's API by computing it internally, but most callers have the
1389  * value at hand anyway.
1390  */
1391 List *
1392 generate_join_implied_equalities(PlannerInfo *root,
1393  Relids join_relids,
1394  Relids outer_relids,
1395  RelOptInfo *inner_rel,
1396  SpecialJoinInfo *sjinfo)
1397 {
1398  List *result = NIL;
1399  Relids inner_relids = inner_rel->relids;
1400  Relids nominal_inner_relids;
1401  Relids nominal_join_relids;
1402  Bitmapset *matching_ecs;
1403  int i;
1404 
1405  /* If inner rel is a child, extra setup work is needed */
1406  if (IS_OTHER_REL(inner_rel))
1407  {
1408  Assert(!bms_is_empty(inner_rel->top_parent_relids));
1409 
1410  /* Fetch relid set for the topmost parent rel */
1411  nominal_inner_relids = inner_rel->top_parent_relids;
1412  /* ECs will be marked with the parent's relid, not the child's */
1413  nominal_join_relids = bms_union(outer_relids, nominal_inner_relids);
1414  nominal_join_relids = add_outer_joins_to_relids(root,
1415  nominal_join_relids,
1416  sjinfo,
1417  NULL);
1418  }
1419  else
1420  {
1421  nominal_inner_relids = inner_relids;
1422  nominal_join_relids = join_relids;
1423  }
1424 
1425  /*
1426  * Examine all potentially-relevant eclasses.
1427  *
1428  * If we are considering an outer join, we must include "join" clauses
1429  * that mention either input rel plus the outer join's relid; these
1430  * represent post-join filter clauses that have to be applied at this
1431  * join. We don't have infrastructure that would let us identify such
1432  * eclasses cheaply, so just fall back to considering all eclasses
1433  * mentioning anything in nominal_join_relids.
1434  *
1435  * At inner joins, we can be smarter: only consider eclasses mentioning
1436  * both input rels.
1437  */
1438  if (sjinfo && sjinfo->ojrelid != 0)
1439  matching_ecs = get_eclass_indexes_for_relids(root, nominal_join_relids);
1440  else
1441  matching_ecs = get_common_eclass_indexes(root, nominal_inner_relids,
1442  outer_relids);
1443 
1444  i = -1;
1445  while ((i = bms_next_member(matching_ecs, i)) >= 0)
1446  {
1447  EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
1448  List *sublist = NIL;
1449 
1450  /* ECs containing consts do not need any further enforcement */
1451  if (ec->ec_has_const)
1452  continue;
1453 
1454  /* Single-member ECs won't generate any deductions */
1455  if (list_length(ec->ec_members) <= 1)
1456  continue;
1457 
1458  /* Sanity check that this eclass overlaps the join */
1459  Assert(bms_overlap(ec->ec_relids, nominal_join_relids));
1460 
1461  if (!ec->ec_broken)
1462  sublist = generate_join_implied_equalities_normal(root,
1463  ec,
1464  join_relids,
1465  outer_relids,
1466  inner_relids);
1467 
1468  /* Recover if we failed to generate required derived clauses */
1469  if (ec->ec_broken)
1470  sublist = generate_join_implied_equalities_broken(root,
1471  ec,
1472  nominal_join_relids,
1473  outer_relids,
1474  nominal_inner_relids,
1475  inner_rel);
1476 
1477  result = list_concat(result, sublist);
1478  }
1479 
1480  return result;
1481 }
1482 
1483 /*
1484  * generate_join_implied_equalities_for_ecs
1485  * As above, but consider only the listed ECs.
1486  *
1487  * For the sole current caller, we can assume sjinfo == NULL, that is we are
1488  * not interested in outer-join filter clauses. This might need to change
1489  * in future.
1490  */
1491 List *
1492 generate_join_implied_equalities_for_ecs(PlannerInfo *root,
1493  List *eclasses,
1494  Relids join_relids,
1495  Relids outer_relids,
1496  RelOptInfo *inner_rel)
1497 {
1498  List *result = NIL;
1499  Relids inner_relids = inner_rel->relids;
1500  Relids nominal_inner_relids;
1501  Relids nominal_join_relids;
1502  ListCell *lc;
1503 
1504  /* If inner rel is a child, extra setup work is needed */
1505  if (IS_OTHER_REL(inner_rel))
1506  {
1507  Assert(!bms_is_empty(inner_rel->top_parent_relids));
1508 
1509  /* Fetch relid set for the topmost parent rel */
1510  nominal_inner_relids = inner_rel->top_parent_relids;
1511  /* ECs will be marked with the parent's relid, not the child's */
1512  nominal_join_relids = bms_union(outer_relids, nominal_inner_relids);
1513  }
1514  else
1515  {
1516  nominal_inner_relids = inner_relids;
1517  nominal_join_relids = join_relids;
1518  }
1519 
1520  foreach(lc, eclasses)
1521  {
1522  EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc);
1523  List *sublist = NIL;
1524 
1525  /* ECs containing consts do not need any further enforcement */
1526  if (ec->ec_has_const)
1527  continue;
1528 
1529  /* Single-member ECs won't generate any deductions */
1530  if (list_length(ec->ec_members) <= 1)
1531  continue;
1532 
1533  /* We can quickly ignore any that don't overlap the join, too */
1534  if (!bms_overlap(ec->ec_relids, nominal_join_relids))
1535  continue;
1536 
1537  if (!ec->ec_broken)
1538  sublist = generate_join_implied_equalities_normal(root,
1539  ec,
1540  join_relids,
1541  outer_relids,
1542  inner_relids);
1543 
1544  /* Recover if we failed to generate required derived clauses */
1545  if (ec->ec_broken)
1546  sublist = generate_join_implied_equalities_broken(root,
1547  ec,
1548  nominal_join_relids,
1549  outer_relids,
1550  nominal_inner_relids,
1551  inner_rel);
1552 
1553  result = list_concat(result, sublist);
1554  }
1555 
1556  return result;
1557 }
1558 
1559 /*
1560  * generate_join_implied_equalities for a still-valid EC
1561  */
1562 static List *
1563 generate_join_implied_equalities_normal(PlannerInfo *root,
1564  EquivalenceClass *ec,
1565  Relids join_relids,
1566  Relids outer_relids,
1567  Relids inner_relids)
1568 {
1569  List *result = NIL;
1570  List *new_members = NIL;
1571  List *outer_members = NIL;
1572  List *inner_members = NIL;
1573  ListCell *lc1;
1574 
1575  /*
1576  * First, scan the EC to identify member values that are computable at the
1577  * outer rel, at the inner rel, or at this relation but not in either
1578  * input rel. The outer-rel members should already be enforced equal,
1579  * likewise for the inner-rel members. We'll need to create clauses to
1580  * enforce that any newly computable members are all equal to each other
1581  * as well as to at least one input member, plus enforce at least one
1582  * outer-rel member equal to at least one inner-rel member.
1583  */
1584  foreach(lc1, ec->ec_members)
1585  {
1586  EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc1);
1587 
1588  /*
1589  * We don't need to check explicitly for child EC members. This test
1590  * against join_relids will cause them to be ignored except when
1591  * considering a child inner rel, which is what we want.
1592  */
1593  if (!bms_is_subset(cur_em->em_relids, join_relids))
1594  continue; /* not computable yet, or wrong child */
1595 
1596  if (bms_is_subset(cur_em->em_relids, outer_relids))
1597  outer_members = lappend(outer_members, cur_em);
1598  else if (bms_is_subset(cur_em->em_relids, inner_relids))
1599  inner_members = lappend(inner_members, cur_em);
1600  else
1601  new_members = lappend(new_members, cur_em);
1602  }
1603 
1604  /*
1605  * First, select the joinclause if needed. We can equate any one outer
1606  * member to any one inner member, but we have to find a datatype
1607  * combination for which an opfamily member operator exists. If we have
1608  * choices, we prefer simple Var members (possibly with RelabelType) since
1609  * these are (a) cheapest to compute at runtime and (b) most likely to
1610  * have useful statistics. Also, prefer operators that are also
1611  * hashjoinable.
1612  */
1613  if (outer_members && inner_members)
1614  {
1615  EquivalenceMember *best_outer_em = NULL;
1616  EquivalenceMember *best_inner_em = NULL;
1617  Oid best_eq_op = InvalidOid;
1618  int best_score = -1;
1619  RestrictInfo *rinfo;
1620 
1621  foreach(lc1, outer_members)
1622  {
1623  EquivalenceMember *outer_em = (EquivalenceMember *) lfirst(lc1);
1624  ListCell *lc2;
1625 
1626  foreach(lc2, inner_members)
1627  {
1628  EquivalenceMember *inner_em = (EquivalenceMember *) lfirst(lc2);
1629  Oid eq_op;
1630  int score;
1631 
1632  eq_op = select_equality_operator(ec,
1633  outer_em->em_datatype,
1634  inner_em->em_datatype);
1635  if (!OidIsValid(eq_op))
1636  continue;
1637  score = 0;
1638  if (IsA(outer_em->em_expr, Var) ||
1639  (IsA(outer_em->em_expr, RelabelType) &&
1640  IsA(((RelabelType *) outer_em->em_expr)->arg, Var)))
1641  score++;
1642  if (IsA(inner_em->em_expr, Var) ||
1643  (IsA(inner_em->em_expr, RelabelType) &&
1644  IsA(((RelabelType *) inner_em->em_expr)->arg, Var)))
1645  score++;
1646  if (op_hashjoinable(eq_op,
1647  exprType((Node *) outer_em->em_expr)))
1648  score++;
1649  if (score > best_score)
1650  {
1651  best_outer_em = outer_em;
1652  best_inner_em = inner_em;
1653  best_eq_op = eq_op;
1654  best_score = score;
1655  if (best_score == 3)
1656  break; /* no need to look further */
1657  }
1658  }
1659  if (best_score == 3)
1660  break; /* no need to look further */
1661  }
1662  if (best_score < 0)
1663  {
1664  /* failed... */
1665  ec->ec_broken = true;
1666  return NIL;
1667  }
1668 
1669  /*
1670  * Create clause, setting parent_ec to mark it as redundant with other
1671  * joinclauses
1672  */
1673  rinfo = create_join_clause(root, ec, best_eq_op,
1674  best_outer_em, best_inner_em,
1675  ec);
1676 
1677  result = lappend(result, rinfo);
1678  }
1679 
1680  /*
1681  * Now deal with building restrictions for any expressions that involve
1682  * Vars from both sides of the join. We have to equate all of these to
1683  * each other as well as to at least one old member (if any).
1684  *
1685  * XXX as in generate_base_implied_equalities_no_const, we could be a lot
1686  * smarter here to avoid unnecessary failures in cross-type situations.
1687  * For now, use the same left-to-right method used there.
1688  */
1689  if (new_members)
1690  {
1691  List *old_members = list_concat(outer_members, inner_members);
1692  EquivalenceMember *prev_em = NULL;
1693  RestrictInfo *rinfo;
1694 
1695  /* For now, arbitrarily take the first old_member as the one to use */
1696  if (old_members)
1697  new_members = lappend(new_members, linitial(old_members));
1698 
1699  foreach(lc1, new_members)
1700  {
1701  EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc1);
1702 
1703  if (prev_em != NULL)
1704  {
1705  Oid eq_op;
1706 
1707  eq_op = select_equality_operator(ec,
1708  prev_em->em_datatype,
1709  cur_em->em_datatype);
1710  if (!OidIsValid(eq_op))
1711  {
1712  /* failed... */
1713  ec->ec_broken = true;
1714  return NIL;
1715  }
1716  /* do NOT set parent_ec, this qual is not redundant! */
1717  rinfo = create_join_clause(root, ec, eq_op,
1718  prev_em, cur_em,
1719  NULL);
1720 
1721  result = lappend(result, rinfo);
1722  }
1723  prev_em = cur_em;
1724  }
1725  }
1726 
1727  return result;
1728 }
1729 
1730 /*
1731  * generate_join_implied_equalities cleanup after failure
1732  *
1733  * Return any original RestrictInfos that are enforceable at this join.
1734  *
1735  * In the case of a child inner relation, we have to translate the
1736  * original RestrictInfos from parent to child Vars.
1737  */
1738 static List *
1739 generate_join_implied_equalities_broken(PlannerInfo *root,
1740  EquivalenceClass *ec,
1741  Relids nominal_join_relids,
1742  Relids outer_relids,
1743  Relids nominal_inner_relids,
1744  RelOptInfo *inner_rel)
1745 {
1746  List *result = NIL;
1747  ListCell *lc;
1748 
1749  foreach(lc, ec->ec_sources)
1750  {
1751  RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc);
1752  Relids clause_relids = restrictinfo->required_relids;
1753 
1754  if (bms_is_subset(clause_relids, nominal_join_relids) &&
1755  !bms_is_subset(clause_relids, outer_relids) &&
1756  !bms_is_subset(clause_relids, nominal_inner_relids))
1757  result = lappend(result, restrictinfo);
1758  }
1759 
1760  /*
1761  * If we have to translate, just brute-force apply adjust_appendrel_attrs
1762  * to all the RestrictInfos at once. This will result in returning
1763  * RestrictInfos that are not listed in ec_derives, but there shouldn't be
1764  * any duplication, and it's a sufficiently narrow corner case that we
1765  * shouldn't sweat too much over it anyway.
1766  *
1767  * Since inner_rel might be an indirect descendant of the baserel
1768  * mentioned in the ec_sources clauses, we have to be prepared to apply
1769  * multiple levels of Var translation.
1770  */
1771  if (IS_OTHER_REL(inner_rel) && result != NIL)
1772  result = (List *) adjust_appendrel_attrs_multilevel(root,
1773  (Node *) result,
1774  inner_rel,
1775  inner_rel->top_parent);
1776 
1777  return result;
1778 }
1779 
1780 
1781 /*
1782  * select_equality_operator
1783  * Select a suitable equality operator for comparing two EC members
1784  *
1785  * Returns InvalidOid if no operator can be found for this datatype combination
1786  */
1787 static Oid
1788 select_equality_operator(EquivalenceClass *ec, Oid lefttype, Oid righttype)
1789 {
1790  ListCell *lc;
1791 
1792  foreach(lc, ec->ec_opfamilies)
1793  {
1794  Oid opfamily = lfirst_oid(lc);
1795  Oid opno;
1796 
1797  opno = get_opfamily_member(opfamily, lefttype, righttype,
1798  BTEqualStrategyNumber);
1799  if (!OidIsValid(opno))
1800  continue;
1801  /* If no barrier quals in query, don't worry about leaky operators */
1802  if (ec->ec_max_security == 0)
1803  return opno;
1804  /* Otherwise, insist that selected operators be leakproof */
1805  if (get_func_leakproof(get_opcode(opno)))
1806  return opno;
1807  }
1808  return InvalidOid;
1809 }
1810 
1811 
1812 /*
1813  * create_join_clause
1814  * Find or make a RestrictInfo comparing the two given EC members
1815  * with the given operator (or, possibly, its commutator, because
1816  * the ordering of the operands in the result is not guaranteed).
1817  *
1818  * parent_ec is either equal to ec (if the clause is a potentially-redundant
1819  * join clause) or NULL (if not). We have to treat this as part of the
1820  * match requirements --- it's possible that a clause comparing the same two
1821  * EMs is a join clause in one join path and a restriction clause in another.
1822  */
1823 static RestrictInfo *
1824 create_join_clause(PlannerInfo *root,
1825  EquivalenceClass *ec, Oid opno,
1826  EquivalenceMember *leftem,
1827  EquivalenceMember *rightem,
1828  EquivalenceClass *parent_ec)
1829 {
1830  RestrictInfo *rinfo;
1831  RestrictInfo *parent_rinfo = NULL;
1832  ListCell *lc;
1833  MemoryContext oldcontext;
1834 
1835  /*
1836  * Search to see if we already built a RestrictInfo for this pair of
1837  * EquivalenceMembers. We can use either original source clauses or
1838  * previously-derived clauses, and a commutator clause is acceptable.
1839  *
1840  * We used to verify that opno matches, but that seems redundant: even if
1841  * it's not identical, it'd better have the same effects, or the operator
1842  * families we're using are broken.
1843  */
1844  foreach(lc, ec->ec_sources)
1845  {
1846  rinfo = (RestrictInfo *) lfirst(lc);
1847  if (rinfo->left_em == leftem &&
1848  rinfo->right_em == rightem &&
1849  rinfo->parent_ec == parent_ec)
1850  return rinfo;
1851  if (rinfo->left_em == rightem &&
1852  rinfo->right_em == leftem &&
1853  rinfo->parent_ec == parent_ec)
1854  return rinfo;
1855  }
1856 
1857  foreach(lc, ec->ec_derives)
1858  {
1859  rinfo = (RestrictInfo *) lfirst(lc);
1860  if (rinfo->left_em == leftem &&
1861  rinfo->right_em == rightem &&
1862  rinfo->parent_ec == parent_ec)
1863  return rinfo;
1864  if (rinfo->left_em == rightem &&
1865  rinfo->right_em == leftem &&
1866  rinfo->parent_ec == parent_ec)
1867  return rinfo;
1868  }
1869 
1870  /*
1871  * Not there, so build it, in planner context so we can re-use it. (Not
1872  * important in normal planning, but definitely so in GEQO.)
1873  */
1874  oldcontext = MemoryContextSwitchTo(root->planner_cxt);
1875 
1876  /*
1877  * If either EM is a child, recursively create the corresponding
1878  * parent-to-parent clause, so that we can duplicate its rinfo_serial.
1879  */
1880  if (leftem->em_is_child || rightem->em_is_child)
1881  {
1882  EquivalenceMember *leftp = leftem->em_parent ? leftem->em_parent : leftem;
1883  EquivalenceMember *rightp = rightem->em_parent ? rightem->em_parent : rightem;
1884 
1885  parent_rinfo = create_join_clause(root, ec, opno,
1886  leftp, rightp,
1887  parent_ec);
1888  }
1889 
1890  rinfo = build_implied_join_equality(root,
1891  opno,
1892  ec->ec_collation,
1893  leftem->em_expr,
1894  rightem->em_expr,
1895  bms_union(leftem->em_relids,
1896  rightem->em_relids),
1897  ec->ec_min_security);
1898 
1899  /*
1900  * If either EM is a child, force the clause's clause_relids to include
1901  * the relid(s) of the child rel. In normal cases it would already, but
1902  * not if we are considering appendrel child relations with pseudoconstant
1903  * translated variables (i.e., UNION ALL sub-selects with constant output
1904  * items). We must do this so that join_clause_is_movable_into() will
1905  * think that the clause should be evaluated at the correct place.
1906  */
1907  if (leftem->em_is_child)
1908  rinfo->clause_relids = bms_add_members(rinfo->clause_relids,
1909  leftem->em_relids);
1910  if (rightem->em_is_child)
1911  rinfo->clause_relids = bms_add_members(rinfo->clause_relids,
1912  rightem->em_relids);
1913 
1914  /* If it's a child clause, copy the parent's rinfo_serial */
1915  if (parent_rinfo)
1916  rinfo->rinfo_serial = parent_rinfo->rinfo_serial;
1917 
1918  /* Mark the clause as redundant, or not */
1919  rinfo->parent_ec = parent_ec;
1920 
1921  /*
1922  * We know the correct values for left_ec/right_ec, ie this particular EC,
1923  * so we can just set them directly instead of forcing another lookup.
1924  */
1925  rinfo->left_ec = ec;
1926  rinfo->right_ec = ec;
1927 
1928  /* Mark it as usable with these EMs */
1929  rinfo->left_em = leftem;
1930  rinfo->right_em = rightem;
1931  /* and save it for possible re-use */
1932  ec->ec_derives = lappend(ec->ec_derives, rinfo);
1933 
1934  MemoryContextSwitchTo(oldcontext);
1935 
1936  return rinfo;
1937 }
1938 
1939 
1940 /*
1941  * reconsider_outer_join_clauses
1942  * Re-examine any outer-join clauses that were set aside by
1943  * distribute_qual_to_rels(), and see if we can derive any
1944  * EquivalenceClasses from them. Then, if they were not made
1945  * redundant, push them out into the regular join-clause lists.
1946  *
1947  * When we have mergejoinable clauses A = B that are outer-join clauses,
1948  * we can't blindly combine them with other clauses A = C to deduce B = C,
1949  * since in fact the "equality" A = B won't necessarily hold above the
1950  * outer join (one of the variables might be NULL instead). Nonetheless
1951  * there are cases where we can add qual clauses using transitivity.
1952  *
1953  * One case that we look for here is an outer-join clause OUTERVAR = INNERVAR
1954  * for which there is also an equivalence clause OUTERVAR = CONSTANT.
1955  * It is safe and useful to push a clause INNERVAR = CONSTANT into the
1956  * evaluation of the inner (nullable) relation, because any inner rows not
1957  * meeting this condition will not contribute to the outer-join result anyway.
1958  * (Any outer rows they could join to will be eliminated by the pushed-down
1959  * equivalence clause.)
1960  *
1961  * Note that the above rule does not work for full outer joins; nor is it
1962  * very interesting to consider cases where the generated equivalence clause
1963  * would involve relations outside the outer join, since such clauses couldn't
1964  * be pushed into the inner side's scan anyway. So the restriction to
1965  * outervar = pseudoconstant is not really giving up anything.
1966  *
1967  * For full-join cases, we can only do something useful if it's a FULL JOIN
1968  * USING and a merged column has an equivalence MERGEDVAR = CONSTANT.
1969  * By the time it gets here, the merged column will look like
1970  * COALESCE(LEFTVAR, RIGHTVAR)
1971  * and we will have a full-join clause LEFTVAR = RIGHTVAR that we can match
1972  * the COALESCE expression to. In this situation we can push LEFTVAR = CONSTANT
1973  * and RIGHTVAR = CONSTANT into the input relations, since any rows not
1974  * meeting these conditions cannot contribute to the join result.
1975  *
1976  * Again, there isn't any traction to be gained by trying to deal with
1977  * clauses comparing a mergedvar to a non-pseudoconstant. So we can make
1978  * use of the EquivalenceClasses to search for matching variables that were
1979  * equivalenced to constants. The interesting outer-join clauses were
1980  * accumulated for us by distribute_qual_to_rels.
1981  *
1982  * When we find one of these cases, we implement the changes we want by
1983  * generating a new equivalence clause INNERVAR = CONSTANT (or LEFTVAR, etc)
1984  * and pushing it into the EquivalenceClass structures. This is because we
1985  * may already know that INNERVAR is equivalenced to some other var(s), and
1986  * we'd like the constant to propagate to them too. Note that it would be
1987  * unsafe to merge any existing EC for INNERVAR with the OUTERVAR's EC ---
1988  * that could result in propagating constant restrictions from
1989  * INNERVAR to OUTERVAR, which would be very wrong.
1990  *
1991  * It's possible that the INNERVAR is also an OUTERVAR for some other
1992  * outer-join clause, in which case the process can be repeated. So we repeat
1993  * looping over the lists of clauses until no further deductions can be made.
1994  * Whenever we do make a deduction, we remove the generating clause from the
1995  * lists, since we don't want to make the same deduction twice.
1996  *
1997  * If we don't find any match for a set-aside outer join clause, we must
1998  * throw it back into the regular joinclause processing by passing it to
1999  * distribute_restrictinfo_to_rels(). If we do generate a derived clause,
2000  * however, the outer-join clause is redundant. We must still put some
2001  * clause into the regular processing, because otherwise the join will be
2002  * seen as a clauseless join and avoided during join order searching.
2003  * We handle this by generating a constant-TRUE clause that is marked with
2004  * the same required_relids etc as the removed outer-join clause, thus
2005  * making it a join clause between the correct relations.
2006  */
2007 void
2008 reconsider_outer_join_clauses(PlannerInfo *root)
2009 {
2010  bool found;
2011  ListCell *cell;
2012 
2013  /* Outer loop repeats until we find no more deductions */
2014  do
2015  {
2016  found = false;
2017 
2018  /* Process the LEFT JOIN clauses */
2019  foreach(cell, root->left_join_clauses)
2020  {
2021  OuterJoinClauseInfo *ojcinfo = (OuterJoinClauseInfo *) lfirst(cell);
2022 
2023  if (reconsider_outer_join_clause(root, ojcinfo, true))
2024  {
2025  RestrictInfo *rinfo = ojcinfo->rinfo;
2026 
2027  found = true;
2028  /* remove it from the list */
2029  root->left_join_clauses =
2030  foreach_delete_current(root->left_join_clauses, cell);
2031  /* throw back a dummy replacement clause (see notes above) */
2032  rinfo = make_restrictinfo(root,
2033  (Expr *) makeBoolConst(true, false),
2034  rinfo->is_pushed_down,
2035  rinfo->has_clone,
2036  rinfo->is_clone,
2037  false, /* pseudoconstant */
2038  0, /* security_level */
2039  rinfo->required_relids,
2040  rinfo->incompatible_relids,
2041  rinfo->outer_relids);
2042  distribute_restrictinfo_to_rels(root, rinfo);
2043  }
2044  }
2045 
2046  /* Process the RIGHT JOIN clauses */
2047  foreach(cell, root->right_join_clauses)
2048  {
2049  OuterJoinClauseInfo *ojcinfo = (OuterJoinClauseInfo *) lfirst(cell);
2050 
2051  if (reconsider_outer_join_clause(root, ojcinfo, false))
2052  {
2053  RestrictInfo *rinfo = ojcinfo->rinfo;
2054 
2055  found = true;
2056  /* remove it from the list */
2057  root->right_join_clauses =
2058  foreach_delete_current(root->right_join_clauses, cell);
2059  /* throw back a dummy replacement clause (see notes above) */
2060  rinfo = make_restrictinfo(root,
2061  (Expr *) makeBoolConst(true, false),
2062  rinfo->is_pushed_down,
2063  rinfo->has_clone,
2064  rinfo->is_clone,
2065  false, /* pseudoconstant */
2066  0, /* security_level */
2067  rinfo->required_relids,
2068  rinfo->incompatible_relids,
2069  rinfo->outer_relids);
2070  distribute_restrictinfo_to_rels(root, rinfo);
2071  }
2072  }
2073 
2074  /* Process the FULL JOIN clauses */
2075  foreach(cell, root->full_join_clauses)
2076  {
2077  OuterJoinClauseInfo *ojcinfo = (OuterJoinClauseInfo *) lfirst(cell);
2078 
2079  if (reconsider_full_join_clause(root, ojcinfo))
2080  {
2081  RestrictInfo *rinfo = ojcinfo->rinfo;
2082 
2083  found = true;
2084  /* remove it from the list */
2085  root->full_join_clauses =
2086  foreach_delete_current(root->full_join_clauses, cell);
2087  /* throw back a dummy replacement clause (see notes above) */
2088  rinfo = make_restrictinfo(root,
2089  (Expr *) makeBoolConst(true, false),
2090  rinfo->is_pushed_down,
2091  rinfo->has_clone,
2092  rinfo->is_clone,
2093  false, /* pseudoconstant */
2094  0, /* security_level */
2095  rinfo->required_relids,
2096  rinfo->incompatible_relids,
2097  rinfo->outer_relids);
2098  distribute_restrictinfo_to_rels(root, rinfo);
2099  }
2100  }
2101  } while (found);
2102 
2103  /* Now, any remaining clauses have to be thrown back */
2104  foreach(cell, root->left_join_clauses)
2105  {
2106  OuterJoinClauseInfo *ojcinfo = (OuterJoinClauseInfo *) lfirst(cell);
2107 
2108  distribute_restrictinfo_to_rels(root, ojcinfo->rinfo);
2109  }
2110  foreach(cell, root->right_join_clauses)
2111  {
2112  OuterJoinClauseInfo *ojcinfo = (OuterJoinClauseInfo *) lfirst(cell);
2113 
2114  distribute_restrictinfo_to_rels(root, ojcinfo->rinfo);
2115  }
2116  foreach(cell, root->full_join_clauses)
2117  {
2118  OuterJoinClauseInfo *ojcinfo = (OuterJoinClauseInfo *) lfirst(cell);
2119 
2120  distribute_restrictinfo_to_rels(root, ojcinfo->rinfo);
2121  }
2122 }
2123 
2124 /*
2125  * reconsider_outer_join_clauses for a single LEFT/RIGHT JOIN clause
2126  *
2127  * Returns true if we were able to propagate a constant through the clause.
2128  */
2129 static bool
2130 reconsider_outer_join_clause(PlannerInfo *root, OuterJoinClauseInfo *ojcinfo,
2131  bool outer_on_left)
2132 {
2133  RestrictInfo *rinfo = ojcinfo->rinfo;
2134  SpecialJoinInfo *sjinfo = ojcinfo->sjinfo;
2135  Expr *outervar,
2136  *innervar;
2137  Oid opno,
2138  collation,
2139  left_type,
2140  right_type,
2141  inner_datatype;
2142  Relids inner_relids;
2143  ListCell *lc1;
2144 
2145  Assert(is_opclause(rinfo->clause));
2146  opno = ((OpExpr *) rinfo->clause)->opno;
2147  collation = ((OpExpr *) rinfo->clause)->inputcollid;
2148 
2149  /* Extract needed info from the clause */
2150  op_input_types(opno, &left_type, &right_type);
2151  if (outer_on_left)
2152  {
2153  outervar = (Expr *) get_leftop(rinfo->clause);
2154  innervar = (Expr *) get_rightop(rinfo->clause);
2155  inner_datatype = right_type;
2156  inner_relids = rinfo->right_relids;
2157  }
2158  else
2159  {
2160  outervar = (Expr *) get_rightop(rinfo->clause);
2161  innervar = (Expr *) get_leftop(rinfo->clause);
2162  inner_datatype = left_type;
2163  inner_relids = rinfo->left_relids;
2164  }
2165 
2166  /* Scan EquivalenceClasses for a match to outervar */
2167  foreach(lc1, root->eq_classes)
2168  {
2169  EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
2170  bool match;
2171  ListCell *lc2;
2172 
2173  /* Ignore EC unless it contains pseudoconstants */
2174  if (!cur_ec->ec_has_const)
2175  continue;
2176  /* Never match to a volatile EC */
2177  if (cur_ec->ec_has_volatile)
2178  continue;
2179  /* It has to match the outer-join clause as to semantics, too */
2180  if (collation != cur_ec->ec_collation)
2181  continue;
2182  if (!equal(rinfo->mergeopfamilies, cur_ec->ec_opfamilies))
2183  continue;
2184  /* Does it contain a match to outervar? */
2185  match = false;
2186  foreach(lc2, cur_ec->ec_members)
2187  {
2188  EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
2189 
2190  Assert(!cur_em->em_is_child); /* no children yet */
2191  if (equal(outervar, cur_em->em_expr))
2192  {
2193  match = true;
2194  break;
2195  }
2196  }
2197  if (!match)
2198  continue; /* no match, so ignore this EC */
2199 
2200  /*
2201  * Yes it does! Try to generate a clause INNERVAR = CONSTANT for each
2202  * CONSTANT in the EC. Note that we must succeed with at least one
2203  * constant before we can decide to throw away the outer-join clause.
2204  */
2205  match = false;
2206  foreach(lc2, cur_ec->ec_members)
2207  {
2208  EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
2209  Oid eq_op;
2210  RestrictInfo *newrinfo;
2211  JoinDomain *jdomain;
2212 
2213  if (!cur_em->em_is_const)
2214  continue; /* ignore non-const members */
2215  eq_op = select_equality_operator(cur_ec,
2216  inner_datatype,
2217  cur_em->em_datatype);
2218  if (!OidIsValid(eq_op))
2219  continue; /* can't generate equality */
2220  newrinfo = build_implied_join_equality(root,
2221  eq_op,
2222  cur_ec->ec_collation,
2223  innervar,
2224  cur_em->em_expr,
2225  bms_copy(inner_relids),
2226  cur_ec->ec_min_security);
2227  /* This equality holds within the OJ's child JoinDomain */
2228  jdomain = find_join_domain(root, sjinfo->syn_righthand);
2229  if (process_equivalence(root, &newrinfo, jdomain))
2230  match = true;
2231  }
2232 
2233  /*
2234  * If we were able to equate INNERVAR to any constant, report success.
2235  * Otherwise, fall out of the search loop, since we know the OUTERVAR
2236  * appears in at most one EC.
2237  */
2238  if (match)
2239  return true;
2240  else
2241  break;
2242  }
2243 
2244  return false; /* failed to make any deduction */
2245 }
2246 
2247 /*
2248  * reconsider_outer_join_clauses for a single FULL JOIN clause
2249  *
2250  * Returns true if we were able to propagate a constant through the clause.
2251  */
2252 static bool
2253 reconsider_full_join_clause(PlannerInfo *root, OuterJoinClauseInfo *ojcinfo)
2254 {
2255  RestrictInfo *rinfo = ojcinfo->rinfo;
2256  SpecialJoinInfo *sjinfo = ojcinfo->sjinfo;
2257  Relids fjrelids = bms_make_singleton(sjinfo->ojrelid);
2258  Expr *leftvar;
2259  Expr *rightvar;
2260  Oid opno,
2261  collation,
2262  left_type,
2263  right_type;
2264  Relids left_relids,
2265  right_relids;
2266  ListCell *lc1;
2267 
2268  /* Extract needed info from the clause */
2269  Assert(is_opclause(rinfo->clause));
2270  opno = ((OpExpr *) rinfo->clause)->opno;
2271  collation = ((OpExpr *) rinfo->clause)->inputcollid;
2272  op_input_types(opno, &left_type, &right_type);
2273  leftvar = (Expr *) get_leftop(rinfo->clause);
2274  rightvar = (Expr *) get_rightop(rinfo->clause);
2275  left_relids = rinfo->left_relids;
2276  right_relids = rinfo->right_relids;
2277 
2278  foreach(lc1, root->eq_classes)
2279  {
2280  EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
2281  EquivalenceMember *coal_em = NULL;
2282  bool match;
2283  bool matchleft;
2284  bool matchright;
2285  ListCell *lc2;
2286  int coal_idx = -1;
2287 
2288  /* Ignore EC unless it contains pseudoconstants */
2289  if (!cur_ec->ec_has_const)
2290  continue;
2291  /* Never match to a volatile EC */
2292  if (cur_ec->ec_has_volatile)
2293  continue;
2294  /* It has to match the outer-join clause as to semantics, too */
2295  if (collation != cur_ec->ec_collation)
2296  continue;
2297  if (!equal(rinfo->mergeopfamilies, cur_ec->ec_opfamilies))
2298  continue;
2299 
2300  /*
2301  * Does it contain a COALESCE(leftvar, rightvar) construct?
2302  *
2303  * We can assume the COALESCE() inputs are in the same order as the
2304  * join clause, since both were automatically generated in the cases
2305  * we care about.
2306  *
2307  * XXX currently this may fail to match in cross-type cases because
2308  * the COALESCE will contain typecast operations while the join clause
2309  * may not (if there is a cross-type mergejoin operator available for
2310  * the two column types). Is it OK to strip implicit coercions from
2311  * the COALESCE arguments?
2312  */
2313  match = false;
2314  foreach(lc2, cur_ec->ec_members)
2315  {
2316  coal_em = (EquivalenceMember *) lfirst(lc2);
2317  Assert(!coal_em->em_is_child); /* no children yet */
2318  if (IsA(coal_em->em_expr, CoalesceExpr))
2319  {
2320  CoalesceExpr *cexpr = (CoalesceExpr *) coal_em->em_expr;
2321  Node *cfirst;
2322  Node *csecond;
2323 
2324  if (list_length(cexpr->args) != 2)
2325  continue;
2326  cfirst = (Node *) linitial(cexpr->args);
2327  csecond = (Node *) lsecond(cexpr->args);
2328 
2329  /*
2330  * The COALESCE arguments will be marked as possibly nulled by
2331  * the full join, while we wish to generate clauses that apply
2332  * to the join's inputs. So we must strip the join from the
2333  * nullingrels fields of cfirst/csecond before comparing them
2334  * to leftvar/rightvar. (Perhaps with a less hokey
2335  * representation for FULL JOIN USING output columns, this
2336  * wouldn't be needed?)
2337  */
2338  cfirst = remove_nulling_relids(cfirst, fjrelids, NULL);
2339  csecond = remove_nulling_relids(csecond, fjrelids, NULL);
2340 
2341  if (equal(leftvar, cfirst) && equal(rightvar, csecond))
2342  {
2343  coal_idx = foreach_current_index(lc2);
2344  match = true;
2345  break;
2346  }
2347  }
2348  }
2349  if (!match)
2350  continue; /* no match, so ignore this EC */
2351 
2352  /*
2353  * Yes it does! Try to generate clauses LEFTVAR = CONSTANT and
2354  * RIGHTVAR = CONSTANT for each CONSTANT in the EC. Note that we must
2355  * succeed with at least one constant for each var before we can
2356  * decide to throw away the outer-join clause.
2357  */
2358  matchleft = matchright = false;
2359  foreach(lc2, cur_ec->ec_members)
2360  {
2361  EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc2);
2362  Oid eq_op;
2363  RestrictInfo *newrinfo;
2364  JoinDomain *jdomain;
2365 
2366  if (!cur_em->em_is_const)
2367  continue; /* ignore non-const members */
2368  eq_op = select_equality_operator(cur_ec,
2369  left_type,
2370  cur_em->em_datatype);
2371  if (OidIsValid(eq_op))
2372  {
2373  newrinfo = build_implied_join_equality(root,
2374  eq_op,
2375  cur_ec->ec_collation,
2376  leftvar,
2377  cur_em->em_expr,
2378  bms_copy(left_relids),
2379  cur_ec->ec_min_security);
2380  /* This equality holds within the lefthand child JoinDomain */
2381  jdomain = find_join_domain(root, sjinfo->syn_lefthand);
2382  if (process_equivalence(root, &newrinfo, jdomain))
2383  matchleft = true;
2384  }
2385  eq_op = select_equality_operator(cur_ec,
2386  right_type,
2387  cur_em->em_datatype);
2388  if (OidIsValid(eq_op))
2389  {
2390  newrinfo = build_implied_join_equality(root,
2391  eq_op,
2392  cur_ec->ec_collation,
2393  rightvar,
2394  cur_em->em_expr,
2395  bms_copy(right_relids),
2396  cur_ec->ec_min_security);
2397  /* This equality holds within the righthand child JoinDomain */
2398  jdomain = find_join_domain(root, sjinfo->syn_righthand);
2399  if (process_equivalence(root, &newrinfo, jdomain))
2400  matchright = true;
2401  }
2402  }
2403 
2404  /*
2405  * If we were able to equate both vars to constants, we're done, and
2406  * we can throw away the full-join clause as redundant. Moreover, we
2407  * can remove the COALESCE entry from the EC, since the added
2408  * restrictions ensure it will always have the expected value. (We
2409  * don't bother trying to update ec_relids or ec_sources.)
2410  */
2411  if (matchleft && matchright)
2412  {
2413  cur_ec->ec_members = list_delete_nth_cell(cur_ec->ec_members, coal_idx);
2414  return true;
2415  }
2416 
2417  /*
2418  * Otherwise, fall out of the search loop, since we know the COALESCE
2419  * appears in at most one EC (XXX might stop being true if we allow
2420  * stripping of coercions above?)
2421  */
2422  break;
2423  }
2424 
2425  return false; /* failed to make any deduction */
2426 }
2427 
2428 /*
2429  * find_join_domain
2430  * Find the highest JoinDomain enclosed within the given relid set.
2431  *
2432  * (We could avoid this search at the cost of complicating APIs elsewhere,
2433  * which doesn't seem worth it.)
2434  */
2435 static JoinDomain *
2436 find_join_domain(PlannerInfo *root, Relids relids)
2437 {
2438  ListCell *lc;
2439 
2440  foreach(lc, root->join_domains)
2441  {
2442  JoinDomain *jdomain = (JoinDomain *) lfirst(lc);
2443 
2444  if (bms_is_subset(jdomain->jd_relids, relids))
2445  return jdomain;
2446  }
2447  elog(ERROR, "failed to find appropriate JoinDomain");
2448  return NULL; /* keep compiler quiet */
2449 }
2450 
2451 
2452 /*
2453  * exprs_known_equal
2454  * Detect whether two expressions are known equal due to equivalence
2455  * relationships.
2456  *
2457  * Actually, this only shows that the expressions are equal according
2458  * to some opfamily's notion of equality --- but we only use it for
2459  * selectivity estimation, so a fuzzy idea of equality is OK.
2460  *
2461  * Note: does not bother to check for "equal(item1, item2)"; caller must
2462  * check that case if it's possible to pass identical items.
2463  */
2464 bool
2465 exprs_known_equal(PlannerInfo *root, Node *item1, Node *item2)
2466 {
2467  ListCell *lc1;
2468 
2469  foreach(lc1, root->eq_classes)
2470  {
2471  EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc1);
2472  bool item1member = false;
2473  bool item2member = false;
2474  ListCell *lc2;
2475 
2476  /* Never match to a volatile EC */
2477  if (ec->ec_has_volatile)
2478  continue;
2479 
2480  foreach(lc2, ec->ec_members)
2481  {
2482  EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2);
2483 
2484  if (em->em_is_child)
2485  continue; /* ignore children here */
2486  if (equal(item1, em->em_expr))
2487  item1member = true;
2488  else if (equal(item2, em->em_expr))
2489  item2member = true;
2490  /* Exit as soon as equality is proven */
2491  if (item1member && item2member)
2492  return true;
2493  }
2494  }
2495  return false;
2496 }
2497 
2498 
2499 /*
2500  * match_eclasses_to_foreign_key_col
2501  * See whether a foreign key column match is proven by any eclass.
2502  *
2503  * If the referenced and referencing Vars of the fkey's colno'th column are
2504  * known equal due to any eclass, return that eclass; otherwise return NULL.
2505  * (In principle there might be more than one matching eclass if multiple
2506  * collations are involved, but since collation doesn't matter for equality,
2507  * we ignore that fine point here.) This is much like exprs_known_equal,
2508  * except that we insist on the comparison operator matching the eclass, so
2509  * that the result is definite not approximate.
2510  *
2511  * On success, we also set fkinfo->eclass[colno] to the matching eclass,
2512  * and set fkinfo->fk_eclass_member[colno] to the eclass member for the
2513  * referencing Var.
2514  */
2515 EquivalenceClass *
2516 match_eclasses_to_foreign_key_col(PlannerInfo *root,
2517  ForeignKeyOptInfo *fkinfo,
2518  int colno)
2519 {
2520  Index var1varno = fkinfo->con_relid;
2521  AttrNumber var1attno = fkinfo->conkey[colno];
2522  Index var2varno = fkinfo->ref_relid;
2523  AttrNumber var2attno = fkinfo->confkey[colno];
2524  Oid eqop = fkinfo->conpfeqop[colno];
2525  RelOptInfo *rel1 = root->simple_rel_array[var1varno];
2526  RelOptInfo *rel2 = root->simple_rel_array[var2varno];
2527  List *opfamilies = NIL; /* compute only if needed */
2528  Bitmapset *matching_ecs;
2529  int i;
2530 
2531  /* Consider only eclasses mentioning both relations */
2532  Assert(root->ec_merging_done);
2533  Assert(IS_SIMPLE_REL(rel1));
2534  Assert(IS_SIMPLE_REL(rel2));
2535  matching_ecs = bms_intersect(rel1->eclass_indexes,
2536  rel2->eclass_indexes);
2537 
2538  i = -1;
2539  while ((i = bms_next_member(matching_ecs, i)) >= 0)
2540  {
2541  EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes,
2542  i);
2543  EquivalenceMember *item1_em = NULL;
2544  EquivalenceMember *item2_em = NULL;
2545  ListCell *lc2;
2546 
2547  /* Never match to a volatile EC */
2548  if (ec->ec_has_volatile)
2549  continue;
2550  /* Note: it seems okay to match to "broken" eclasses here */
2551 
2552  foreach(lc2, ec->ec_members)
2553  {
2554  EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2);
2555  Var *var;
2556 
2557  if (em->em_is_child)
2558  continue; /* ignore children here */
2559 
2560  /* EM must be a Var, possibly with RelabelType */
2561  var = (Var *) em->em_expr;
2562  while (var && IsA(var, RelabelType))
2563  var = (Var *) ((RelabelType *) var)->arg;
2564  if (!(var && IsA(var, Var)))
2565  continue;
2566 
2567  /* Match? */
2568  if (var->varno == var1varno && var->varattno == var1attno)
2569  item1_em = em;
2570  else if (var->varno == var2varno && var->varattno == var2attno)
2571  item2_em = em;
2572 
2573  /* Have we found both PK and FK column in this EC? */
2574  if (item1_em && item2_em)
2575  {
2576  /*
2577  * Succeed if eqop matches EC's opfamilies. We could test
2578  * this before scanning the members, but it's probably cheaper
2579  * to test for member matches first.
2580  */
2581  if (opfamilies == NIL) /* compute if we didn't already */
2582  opfamilies = get_mergejoin_opfamilies(eqop);
2583  if (equal(opfamilies, ec->ec_opfamilies))
2584  {
2585  fkinfo->eclass[colno] = ec;
2586  fkinfo->fk_eclass_member[colno] = item2_em;
2587  return ec;
2588  }
2589  /* Otherwise, done with this EC, move on to the next */
2590  break;
2591  }
2592  }
2593  }
2594  return NULL;
2595 }
2596 
2597 /*
2598  * find_derived_clause_for_ec_member
2599  * Search for a previously-derived clause mentioning the given EM.
2600  *
2601  * The eclass should be an ec_has_const EC, of which the EM is a non-const
2602  * member. This should ensure there is just one derived clause mentioning
2603  * the EM (and equating it to a constant).
2604  * Returns NULL if no such clause can be found.
2605  */
2606 RestrictInfo *
2607 find_derived_clause_for_ec_member(EquivalenceClass *ec,
2608  EquivalenceMember *em)
2609 {
2610  ListCell *lc;
2611 
2612  Assert(ec->ec_has_const);
2613  Assert(!em->em_is_const);
2614  foreach(lc, ec->ec_derives)
2615  {
2616  RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
2617 
2618  /*
2619  * generate_base_implied_equalities_const will have put non-const
2620  * members on the left side of derived clauses.
2621  */
2622  if (rinfo->left_em == em)
2623  return rinfo;
2624  }
2625  return NULL;
2626 }
2627 
2628 
2629 /*
2630  * add_child_rel_equivalences
2631  * Search for EC members that reference the root parent of child_rel, and
2632  * add transformed members referencing the child_rel.
2633  *
2634  * Note that this function won't be called at all unless we have at least some
2635  * reason to believe that the EC members it generates will be useful.
2636  *
2637  * parent_rel and child_rel could be derived from appinfo, but since the
2638  * caller has already computed them, we might as well just pass them in.
2639  *
2640  * The passed-in AppendRelInfo is not used when the parent_rel is not a
2641  * top-level baserel, since it shows the mapping from the parent_rel but
2642  * we need to translate EC expressions that refer to the top-level parent.
2643  * Using it is faster than using adjust_appendrel_attrs_multilevel(), though,
2644  * so we prefer it when we can.
2645  */
2646 void
2647 add_child_rel_equivalences(PlannerInfo *root,
2648  AppendRelInfo *appinfo,
2649  RelOptInfo *parent_rel,
2650  RelOptInfo *child_rel)
2651 {
2652  Relids top_parent_relids = child_rel->top_parent_relids;
2653  Relids child_relids = child_rel->relids;
2654  int i;
2655 
2656  /*
2657  * EC merging should be complete already, so we can use the parent rel's
2658  * eclass_indexes to avoid searching all of root->eq_classes.
2659  */
2660  Assert(root->ec_merging_done);
2661  Assert(IS_SIMPLE_REL(parent_rel));
2662 
2663  i = -1;
2664  while ((i = bms_next_member(parent_rel->eclass_indexes, i)) >= 0)
2665  {
2666  EquivalenceClass *cur_ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
2667  int num_members;
2668 
2669  /*
2670  * If this EC contains a volatile expression, then generating child
2671  * EMs would be downright dangerous, so skip it. We rely on a
2672  * volatile EC having only one EM.
2673  */
2674  if (cur_ec->ec_has_volatile)
2675  continue;
2676 
2677  /* Sanity check eclass_indexes only contain ECs for parent_rel */
2678  Assert(bms_is_subset(top_parent_relids, cur_ec->ec_relids));
2679 
2680  /*
2681  * We don't use foreach() here because there's no point in scanning
2682  * newly-added child members, so we can stop after the last
2683  * pre-existing EC member.
2684  */
2685  num_members = list_length(cur_ec->ec_members);
2686  for (int pos = 0; pos < num_members; pos++)
2687  {
2688  EquivalenceMember *cur_em = (EquivalenceMember *) list_nth(cur_ec->ec_members, pos);
2689 
2690  if (cur_em->em_is_const)
2691  continue; /* ignore consts here */
2692 
2693  /*
2694  * We consider only original EC members here, not
2695  * already-transformed child members. Otherwise, if some original
2696  * member expression references more than one appendrel, we'd get
2697  * an O(N^2) explosion of useless derived expressions for
2698  * combinations of children. (But add_child_join_rel_equivalences
2699  * may add targeted combinations for partitionwise-join purposes.)
2700  */
2701  if (cur_em->em_is_child)
2702  continue; /* ignore children here */
2703 
2704  /*
2705  * Consider only members that reference and can be computed at
2706  * child's topmost parent rel. In particular we want to exclude
2707  * parent-rel Vars that have nonempty varnullingrels. Translating
2708  * those might fail, if the transformed expression wouldn't be a
2709  * simple Var; and in any case it wouldn't produce a member that
2710  * has any use in creating plans for the child rel.
2711  */
2712  if (bms_is_subset(cur_em->em_relids, top_parent_relids) &&
2713  !bms_is_empty(cur_em->em_relids))
2714  {
2715  /* OK, generate transformed child version */
2716  Expr *child_expr;
2717  Relids new_relids;
2718 
2719  if (parent_rel->reloptkind == RELOPT_BASEREL)
2720  {
2721  /* Simple single-level transformation */
2722  child_expr = (Expr *)
2723  adjust_appendrel_attrs(root,
2724  (Node *) cur_em->em_expr,
2725  1, &appinfo);
2726  }
2727  else
2728  {
2729  /* Must do multi-level transformation */
2730  child_expr = (Expr *)
2731  adjust_appendrel_attrs_multilevel(root,
2732  (Node *) cur_em->em_expr,
2733  child_rel,
2734  child_rel->top_parent);
2735  }
2736 
2737  /*
2738  * Transform em_relids to match. Note we do *not* do
2739  * pull_varnos(child_expr) here, as for example the
2740  * transformation might have substituted a constant, but we
2741  * don't want the child member to be marked as constant.
2742  */
2743  new_relids = bms_difference(cur_em->em_relids,
2744  top_parent_relids);
2745  new_relids = bms_add_members(new_relids, child_relids);
2746 
2747  (void) add_eq_member(cur_ec, child_expr, new_relids,
2748  cur_em->em_jdomain,
2749  cur_em, cur_em->em_datatype);
2750 
2751  /* Record this EC index for the child rel */
2752  child_rel->eclass_indexes = bms_add_member(child_rel->eclass_indexes, i);
2753  }
2754  }
2755  }
2756 }
2757 
2758 /*
2759  * add_child_join_rel_equivalences
2760  * Like add_child_rel_equivalences(), but for joinrels
2761  *
2762  * Here we find the ECs relevant to the top parent joinrel and add transformed
2763  * member expressions that refer to this child joinrel.
2764  *
2765  * Note that this function won't be called at all unless we have at least some
2766  * reason to believe that the EC members it generates will be useful.
2767  */
2768 void
2769 add_child_join_rel_equivalences(PlannerInfo *root,
2770  int nappinfos, AppendRelInfo **appinfos,
2771  RelOptInfo *parent_joinrel,
2772  RelOptInfo *child_joinrel)
2773 {
2774  Relids top_parent_relids = child_joinrel->top_parent_relids;
2775  Relids child_relids = child_joinrel->relids;
2776  Bitmapset *matching_ecs;
2777  MemoryContext oldcontext;
2778  int i;
2779 
2780  Assert(IS_JOIN_REL(child_joinrel) && IS_JOIN_REL(parent_joinrel));
2781 
2782  /* We need consider only ECs that mention the parent joinrel */
2783  matching_ecs = get_eclass_indexes_for_relids(root, top_parent_relids);
2784 
2785  /*
2786  * If we're being called during GEQO join planning, we still have to
2787  * create any new EC members in the main planner context, to avoid having
2788  * a corrupt EC data structure after the GEQO context is reset. This is
2789  * problematic since we'll leak memory across repeated GEQO cycles. For
2790  * now, though, bloat is better than crash. If it becomes a real issue
2791  * we'll have to do something to avoid generating duplicate EC members.
2792  */
2793  oldcontext = MemoryContextSwitchTo(root->planner_cxt);
2794 
2795  i = -1;
2796  while ((i = bms_next_member(matching_ecs, i)) >= 0)
2797  {
2798  EquivalenceClass *cur_ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
2799  int num_members;
2800 
2801  /*
2802  * If this EC contains a volatile expression, then generating child
2803  * EMs would be downright dangerous, so skip it. We rely on a
2804  * volatile EC having only one EM.
2805  */
2806  if (cur_ec->ec_has_volatile)
2807  continue;
2808 
2809  /* Sanity check on get_eclass_indexes_for_relids result */
2810  Assert(bms_overlap(top_parent_relids, cur_ec->ec_relids));
2811 
2812  /*
2813  * We don't use foreach() here because there's no point in scanning
2814  * newly-added child members, so we can stop after the last
2815  * pre-existing EC member.
2816  */
2817  num_members = list_length(cur_ec->ec_members);
2818  for (int pos = 0; pos < num_members; pos++)
2819  {
2820  EquivalenceMember *cur_em = (EquivalenceMember *) list_nth(cur_ec->ec_members, pos);
2821 
2822  if (cur_em->em_is_const)
2823  continue; /* ignore consts here */
2824 
2825  /*
2826  * We consider only original EC members here, not
2827  * already-transformed child members.
2828  */
2829  if (cur_em->em_is_child)
2830  continue; /* ignore children here */
2831 
2832  /*
2833  * We may ignore expressions that reference a single baserel,
2834  * because add_child_rel_equivalences should have handled them.
2835  */
2836  if (bms_membership(cur_em->em_relids) != BMS_MULTIPLE)
2837  continue;
2838 
2839  /* Does this member reference child's topmost parent rel? */
2840  if (bms_overlap(cur_em->em_relids, top_parent_relids))
2841  {
2842  /* Yes, generate transformed child version */
2843  Expr *child_expr;
2844  Relids new_relids;
2845 
2846  if (parent_joinrel->reloptkind == RELOPT_JOINREL)
2847  {
2848  /* Simple single-level transformation */
2849  child_expr = (Expr *)
2850  adjust_appendrel_attrs(root,
2851  (Node *) cur_em->em_expr,
2852  nappinfos, appinfos);
2853  }
2854  else
2855  {
2856  /* Must do multi-level transformation */
2857  Assert(parent_joinrel->reloptkind == RELOPT_OTHER_JOINREL);
2858  child_expr = (Expr *)
2859  adjust_appendrel_attrs_multilevel(root,
2860  (Node *) cur_em->em_expr,
2861  child_joinrel,
2862  child_joinrel->top_parent);
2863  }
2864 
2865  /*
2866  * Transform em_relids to match. Note we do *not* do
2867  * pull_varnos(child_expr) here, as for example the
2868  * transformation might have substituted a constant, but we
2869  * don't want the child member to be marked as constant.
2870  */
2871  new_relids = bms_difference(cur_em->em_relids,
2872  top_parent_relids);
2873  new_relids = bms_add_members(new_relids, child_relids);
2874 
2875  (void) add_eq_member(cur_ec, child_expr, new_relids,
2876  cur_em->em_jdomain,
2877  cur_em, cur_em->em_datatype);
2878  }
2879  }
2880  }
2881 
2882  MemoryContextSwitchTo(oldcontext);
2883 }
2884 
2885 /*
2886  * add_setop_child_rel_equivalences
2887  * Add equivalence members for each non-resjunk target in 'child_tlist'
2888  * to the EquivalenceClass in the corresponding setop_pathkey's pk_eclass.
2889  *
2890  * 'root' is the PlannerInfo belonging to the top-level set operation.
2891  * 'child_rel' is the RelOptInfo of the child relation we're adding
2892  * EquivalenceMembers for.
2893  * 'child_tlist' is the target list for the setop child relation. The target
2894  * list expressions are what we add as EquivalenceMembers.
2895  * 'setop_pathkeys' is a list of PathKeys which must contain an entry for each
2896  * non-resjunk target in 'child_tlist'.
2897  */
2898 void
2899 add_setop_child_rel_equivalences(PlannerInfo *root, RelOptInfo *child_rel,
2900  List *child_tlist, List *setop_pathkeys)
2901 {
2902  ListCell *lc;
2903  ListCell *lc2 = list_head(setop_pathkeys);
2904 
2905  foreach(lc, child_tlist)
2906  {
2907  TargetEntry *tle = lfirst_node(TargetEntry, lc);
2908  EquivalenceMember *parent_em;
2909  PathKey *pk;
2910 
2911  if (tle->resjunk)
2912  continue;
2913 
2914  if (lc2 == NULL)
2915  elog(ERROR, "too few pathkeys for set operation");
2916 
2917  pk = lfirst_node(PathKey, lc2);
2918  parent_em = linitial(pk->pk_eclass->ec_members);
2919 
2920  /*
2921  * We can safely pass the parent member as the first member in the
2922  * ec_members list as this is added first in generate_union_paths,
2923  * likewise, the JoinDomain can be that of the initial member of the
2924  * Pathkey's EquivalenceClass.
2925  */
2926  add_eq_member(pk->pk_eclass,
2927  tle->expr,
2928  child_rel->relids,
2929  parent_em->em_jdomain,
2930  parent_em,
2931  exprType((Node *) tle->expr));
2932 
2933  lc2 = lnext(setop_pathkeys, lc2);
2934  }
2935 
2936  /*
2937  * transformSetOperationStmt() ensures that the targetlist never contains
2938  * any resjunk columns, so all eclasses that exist in 'root' must have
2939  * received a new member in the loop above. Add them to the child_rel's
2940  * eclass_indexes.
2941  */
2942  child_rel->eclass_indexes = bms_add_range(child_rel->eclass_indexes, 0,
2943  list_length(root->eq_classes) - 1);
2944 }
2945 
2946 
2947 /*
2948  * generate_implied_equalities_for_column
2949  * Create EC-derived joinclauses usable with a specific column.
2950  *
2951  * This is used by indxpath.c to extract potentially indexable joinclauses
2952  * from ECs, and can be used by foreign data wrappers for similar purposes.
2953  * We assume that only expressions in Vars of a single table are of interest,
2954  * but the caller provides a callback function to identify exactly which
2955  * such expressions it would like to know about.
2956  *
2957  * We assume that any given table/index column could appear in only one EC.
2958  * (This should be true in all but the most pathological cases, and if it
2959  * isn't, we stop on the first match anyway.) Therefore, what we return
2960  * is a redundant list of clauses equating the table/index column to each of
2961  * the other-relation values it is known to be equal to. Any one of
2962  * these clauses can be used to create a parameterized path, and there
2963  * is no value in using more than one. (But it *is* worthwhile to create
2964  * a separate parameterized path for each one, since that leads to different
2965  * join orders.)
2966  *
2967  * The caller can pass a Relids set of rels we aren't interested in joining
2968  * to, so as to save the work of creating useless clauses.
2969  */
2970 List *
2971 generate_implied_equalities_for_column(PlannerInfo *root,
2972  RelOptInfo *rel,
2973  ec_matches_callback_type callback,
2974  void *callback_arg,
2975  Relids prohibited_rels)
2976 {
2977  List *result = NIL;
2978  bool is_child_rel = (rel->reloptkind == RELOPT_OTHER_MEMBER_REL);
2979  Relids parent_relids;
2980  int i;
2981 
2982  /* Should be OK to rely on eclass_indexes */
2983  Assert(root->ec_merging_done);
2984 
2985  /* Indexes are available only on base or "other" member relations. */
2986  Assert(IS_SIMPLE_REL(rel));
2987 
2988  /* If it's a child rel, we'll need to know what its parent(s) are */
2989  if (is_child_rel)
2990  parent_relids = find_childrel_parents(root, rel);
2991  else
2992  parent_relids = NULL; /* not used, but keep compiler quiet */
2993 
2994  i = -1;
2995  while ((i = bms_next_member(rel->eclass_indexes, i)) >= 0)
2996  {
2997  EquivalenceClass *cur_ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
2998  EquivalenceMember *cur_em;
2999  ListCell *lc2;
3000 
3001  /* Sanity check eclass_indexes only contain ECs for rel */
3002  Assert(is_child_rel || bms_is_subset(rel->relids, cur_ec->ec_relids));
3003 
3004  /*
3005  * Won't generate joinclauses if const or single-member (the latter
3006  * test covers the volatile case too)
3007  */
3008  if (cur_ec->ec_has_const || list_length(cur_ec->ec_members) <= 1)
3009  continue;
3010 
3011  /*
3012  * Scan members, looking for a match to the target column. Note that
3013  * child EC members are considered, but only when they belong to the
3014  * target relation. (Unlike regular members, the same expression
3015  * could be a child member of more than one EC. Therefore, it's
3016  * potentially order-dependent which EC a child relation's target
3017  * column gets matched to. This is annoying but it only happens in
3018  * corner cases, so for now we live with just reporting the first
3019  * match. See also get_eclass_for_sort_expr.)
3020  */
3021  cur_em = NULL;
3022  foreach(lc2, cur_ec->ec_members)
3023  {
3024  cur_em = (EquivalenceMember *) lfirst(lc2);
3025  if (bms_equal(cur_em->em_relids, rel->relids) &&
3026  callback(root, rel, cur_ec, cur_em, callback_arg))
3027  break;
3028  cur_em = NULL;
3029  }
3030 
3031  if (!cur_em)
3032  continue;
3033 
3034  /*
3035  * Found our match. Scan the other EC members and attempt to generate
3036  * joinclauses.
3037  */
3038  foreach(lc2, cur_ec->ec_members)
3039  {
3040  EquivalenceMember *other_em = (EquivalenceMember *) lfirst(lc2);
3041  Oid eq_op;
3042  RestrictInfo *rinfo;
3043 
3044  if (other_em->em_is_child)
3045  continue; /* ignore children here */
3046 
3047  /* Make sure it'll be a join to a different rel */
3048  if (other_em == cur_em ||
3049  bms_overlap(other_em->em_relids, rel->relids))
3050  continue;
3051 
3052  /* Forget it if caller doesn't want joins to this rel */
3053  if (bms_overlap(other_em->em_relids, prohibited_rels))
3054  continue;
3055 
3056  /*
3057  * Also, if this is a child rel, avoid generating a useless join
3058  * to its parent rel(s).
3059  */
3060  if (is_child_rel &&
3061  bms_overlap(parent_relids, other_em->em_relids))
3062  continue;
3063 
3064  eq_op = select_equality_operator(cur_ec,
3065  cur_em->em_datatype,
3066  other_em->em_datatype);
3067  if (!OidIsValid(eq_op))
3068  continue;
3069 
3070  /* set parent_ec to mark as redundant with other joinclauses */
3071  rinfo = create_join_clause(root, cur_ec, eq_op,
3072  cur_em, other_em,
3073  cur_ec);
3074 
3075  result = lappend(result, rinfo);
3076  }
3077 
3078  /*
3079  * If somehow we failed to create any join clauses, we might as well
3080  * keep scanning the ECs for another match. But if we did make any,
3081  * we're done, because we don't want to return non-redundant clauses.
3082  */
3083  if (result)
3084  break;
3085  }
3086 
3087  return result;
3088 }
3089 
3090 /*
3091  * have_relevant_eclass_joinclause
3092  * Detect whether there is an EquivalenceClass that could produce
3093  * a joinclause involving the two given relations.
3094  *
3095  * This is essentially a very cut-down version of
3096  * generate_join_implied_equalities(). Note it's OK to occasionally say "yes"
3097  * incorrectly. Hence we don't bother with details like whether the lack of a
3098  * cross-type operator might prevent the clause from actually being generated.
3099  * False negatives are not always fatal either: they will discourage, but not
3100  * completely prevent, investigation of particular join pathways.
3101  */
3102 bool
3103 have_relevant_eclass_joinclause(PlannerInfo *root,
3104  RelOptInfo *rel1, RelOptInfo *rel2)
3105 {
3106  Bitmapset *matching_ecs;
3107  int i;
3108 
3109  /*
3110  * Examine only eclasses mentioning both rel1 and rel2.
3111  *
3112  * Note that we do not consider the possibility of an eclass generating
3113  * "join" clauses that mention just one of the rels plus an outer join
3114  * that could be formed from them. Although such clauses must be
3115  * correctly enforced when we form the outer join, they don't seem like
3116  * sufficient reason to prioritize this join over other ones. The join
3117  * ordering rules will force the join to be made when necessary.
3118  */
3119  matching_ecs = get_common_eclass_indexes(root, rel1->relids,
3120  rel2->relids);
3121 
3122  i = -1;
3123  while ((i = bms_next_member(matching_ecs, i)) >= 0)
3124  {
3125  EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes,
3126  i);
3127 
3128  /*
3129  * Sanity check that get_common_eclass_indexes gave only ECs
3130  * containing both rels.
3131  */
3132  Assert(bms_overlap(rel1->relids, ec->ec_relids));
3133  Assert(bms_overlap(rel2->relids, ec->ec_relids));
3134 
3135  /*
3136  * Won't generate joinclauses if single-member (this test covers the
3137  * volatile case too)
3138  */
3139  if (list_length(ec->ec_members) <= 1)
3140  continue;
3141 
3142  /*
3143  * We do not need to examine the individual members of the EC, because
3144  * all that we care about is whether each rel overlaps the relids of
3145  * at least one member, and get_common_eclass_indexes() and the single
3146  * member check above are sufficient to prove that. (As with
3147  * have_relevant_joinclause(), it is not necessary that the EC be able
3148  * to form a joinclause relating exactly the two given rels, only that
3149  * it be able to form a joinclause mentioning both, and this will
3150  * surely be true if both of them overlap ec_relids.)
3151  *
3152  * Note we don't test ec_broken; if we did, we'd need a separate code
3153  * path to look through ec_sources. Checking the membership anyway is
3154  * OK as a possibly-overoptimistic heuristic.
3155  *
3156  * We don't test ec_has_const either, even though a const eclass won't
3157  * generate real join clauses. This is because if we had "WHERE a.x =
3158  * b.y and a.x = 42", it is worth considering a join between a and b,
3159  * since the join result is likely to be small even though it'll end
3160  * up being an unqualified nestloop.
3161  */
3162 
3163  return true;
3164  }
3165 
3166  return false;
3167 }
3168 
3169 
3170 /*
3171  * has_relevant_eclass_joinclause
3172  * Detect whether there is an EquivalenceClass that could produce
3173  * a joinclause involving the given relation and anything else.
3174  *
3175  * This is the same as have_relevant_eclass_joinclause with the other rel
3176  * implicitly defined as "everything else in the query".
3177  */
3178 bool
3179 has_relevant_eclass_joinclause(PlannerInfo *root, RelOptInfo *rel1)
3180 {
3181  Bitmapset *matched_ecs;
3182  int i;
3183 
3184  /* Examine only eclasses mentioning rel1 */
3185  matched_ecs = get_eclass_indexes_for_relids(root, rel1->relids);
3186 
3187  i = -1;
3188  while ((i = bms_next_member(matched_ecs, i)) >= 0)
3189  {
3190  EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes,
3191  i);
3192 
3193  /*
3194  * Won't generate joinclauses if single-member (this test covers the
3195  * volatile case too)
3196  */
3197  if (list_length(ec->ec_members) <= 1)
3198  continue;
3199 
3200  /*
3201  * Per the comment in have_relevant_eclass_joinclause, it's sufficient
3202  * to find an EC that mentions both this rel and some other rel.
3203  */
3204  if (!bms_is_subset(ec->ec_relids, rel1->relids))
3205  return true;
3206  }
3207 
3208  return false;
3209 }
3210 
3211 
3212 /*
3213  * eclass_useful_for_merging
3214  * Detect whether the EC could produce any mergejoinable join clauses
3215  * against the specified relation.
3216  *
3217  * This is just a heuristic test and doesn't have to be exact; it's better
3218  * to say "yes" incorrectly than "no". Hence we don't bother with details
3219  * like whether the lack of a cross-type operator might prevent the clause
3220  * from actually being generated.
3221  */
3222 bool
3223 eclass_useful_for_merging(PlannerInfo *root,
3224  EquivalenceClass *eclass,
3225  RelOptInfo *rel)
3226 {
3227  Relids relids;
3228  ListCell *lc;
3229 
3230  Assert(!eclass->ec_merged);
3231 
3232  /*
3233  * Won't generate joinclauses if const or single-member (the latter test
3234  * covers the volatile case too)
3235  */
3236  if (eclass->ec_has_const || list_length(eclass->ec_members) <= 1)
3237  return false;
3238 
3239  /*
3240  * Note we don't test ec_broken; if we did, we'd need a separate code path
3241  * to look through ec_sources. Checking the members anyway is OK as a
3242  * possibly-overoptimistic heuristic.
3243  */
3244 
3245  /* If specified rel is a child, we must consider the topmost parent rel */
3246  if (IS_OTHER_REL(rel))
3247  {
3248  Assert(!bms_is_empty(rel->top_parent_relids));
3249  relids = rel->top_parent_relids;
3250  }
3251  else
3252  relids = rel->relids;
3253 
3254  /* If rel already includes all members of eclass, no point in searching */
3255  if (bms_is_subset(eclass->ec_relids, relids))
3256  return false;
3257 
3258  /* To join, we need a member not in the given rel */
3259  foreach(lc, eclass->ec_members)
3260  {
3261  EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
3262 
3263  if (cur_em->em_is_child)
3264  continue; /* ignore children here */
3265 
3266  if (!bms_overlap(cur_em->em_relids, relids))
3267  return true;
3268  }
3269 
3270  return false;
3271 }
3272 
3273 
3274 /*
3275  * is_redundant_derived_clause
3276  * Test whether rinfo is derived from same EC as any clause in clauselist;
3277  * if so, it can be presumed to represent a condition that's redundant
3278  * with that member of the list.
3279  */
3280 bool
3281 is_redundant_derived_clause(RestrictInfo *rinfo, List *clauselist)
3282 {
3283  EquivalenceClass *parent_ec = rinfo->parent_ec;
3284  ListCell *lc;
3285 
3286  /* Fail if it's not a potentially-redundant clause from some EC */
3287  if (parent_ec == NULL)
3288  return false;
3289 
3290  foreach(lc, clauselist)
3291  {
3292  RestrictInfo *otherrinfo = (RestrictInfo *) lfirst(lc);
3293 
3294  if (otherrinfo->parent_ec == parent_ec)
3295  return true;
3296  }
3297 
3298  return false;
3299 }
3300 
3301 /*
3302  * is_redundant_with_indexclauses
3303  * Test whether rinfo is redundant with any clause in the IndexClause
3304  * list. Here, for convenience, we test both simple identity and
3305  * whether it is derived from the same EC as any member of the list.
3306  */
3307 bool
3308 is_redundant_with_indexclauses(RestrictInfo *rinfo, List *indexclauses)
3309 {
3310  EquivalenceClass *parent_ec = rinfo->parent_ec;
3311  ListCell *lc;
3312 
3313  foreach(lc, indexclauses)
3314  {
3315  IndexClause *iclause = lfirst_node(IndexClause, lc);
3316  RestrictInfo *otherrinfo = iclause->rinfo;
3317 
3318  /* If indexclause is lossy, it won't enforce the condition exactly */
3319  if (iclause->lossy)
3320  continue;
3321 
3322  /* Match if it's same clause (pointer equality should be enough) */
3323  if (rinfo == otherrinfo)
3324  return true;
3325  /* Match if derived from same EC */
3326  if (parent_ec && otherrinfo->parent_ec == parent_ec)
3327  return true;
3328 
3329  /*
3330  * No need to look at the derived clauses in iclause->indexquals; they
3331  * couldn't match if the parent clause didn't.
3332  */
3333  }
3334 
3335  return false;
3336 }
3337 
3338 /*
3339  * get_eclass_indexes_for_relids
3340  * Build and return a Bitmapset containing the indexes into root's
3341  * eq_classes list for all eclasses that mention any of these relids
3342  */
3343 static Bitmapset *
3344 get_eclass_indexes_for_relids(PlannerInfo *root, Relids relids)
3345 {
3346  Bitmapset *ec_indexes = NULL;
3347  int i = -1;
3348 
3349  /* Should be OK to rely on eclass_indexes */
3350  Assert(root->ec_merging_done);
3351 
3352  while ((i = bms_next_member(relids, i)) > 0)
3353  {
3354  RelOptInfo *rel = root->simple_rel_array[i];
3355 
3356  if (rel == NULL) /* must be an outer join */
3357  {
3358  Assert(bms_is_member(i, root->outer_join_rels));
3359  continue;
3360  }
3361 
3362  ec_indexes = bms_add_members(ec_indexes, rel->eclass_indexes);
3363  }
3364  return ec_indexes;
3365 }
3366 
3367 /*
3368  * get_common_eclass_indexes
3369  * Build and return a Bitmapset containing the indexes into root's
3370  * eq_classes list for all eclasses that mention rels in both
3371  * relids1 and relids2.
3372  */
3373 static Bitmapset *
3374 get_common_eclass_indexes(PlannerInfo *root, Relids relids1, Relids relids2)
3375 {
3376  Bitmapset *rel1ecs;
3377  Bitmapset *rel2ecs;
3378  int relid;
3379 
3380  rel1ecs = get_eclass_indexes_for_relids(root, relids1);
3381 
3382  /*
3383  * We can get away with just using the relation's eclass_indexes directly
3384  * when relids2 is a singleton set.
3385  */
3386  if (bms_get_singleton_member(relids2, &relid))
3387  rel2ecs = root->simple_rel_array[relid]->eclass_indexes;
3388  else
3389  rel2ecs = get_eclass_indexes_for_relids(root, relids2);
3390 
3391  /* Calculate and return the common EC indexes, recycling the left input. */
3392  return bms_int_members(rel1ecs, rel2ecs);
3393 }
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Definition: appendinfo.c:196
adjust_appendrel_attrs_multilevel
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Definition: appendinfo.c:521
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Definition: attnum.h:21
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void set_opfuncid(OpExpr *opexpr)
Definition: nodeFuncs.c:1868
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static bool is_opclause(const void *clause)
Definition: nodeFuncs.h:74
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static Node * get_rightop(const void *clause)
Definition: nodeFuncs.h:93
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static Node * get_leftop(const void *clause)
Definition: nodeFuncs.h:81
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#define IsA(nodeptr, _type_)
Definition: nodes.h:158
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#define copyObject(obj)
Definition: nodes.h:224
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#define makeNode(_type_)
Definition: nodes.h:155
PVC_RECURSE_AGGREGATES
#define PVC_RECURSE_AGGREGATES
Definition: optimizer.h:187
PVC_RECURSE_WINDOWFUNCS
#define PVC_RECURSE_WINDOWFUNCS
Definition: optimizer.h:189
PVC_INCLUDE_WINDOWFUNCS
#define PVC_INCLUDE_WINDOWFUNCS
Definition: optimizer.h:188
PVC_INCLUDE_PLACEHOLDERS
#define PVC_INCLUDE_PLACEHOLDERS
Definition: optimizer.h:190
PVC_INCLUDE_AGGREGATES
#define PVC_INCLUDE_AGGREGATES
Definition: optimizer.h:186
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#define IS_SIMPLE_REL(rel)
Definition: pathnodes.h:829
IS_JOIN_REL
#define IS_JOIN_REL(rel)
Definition: pathnodes.h:834
RELOPT_BASEREL
@ RELOPT_BASEREL
Definition: pathnodes.h:817
RELOPT_OTHER_MEMBER_REL
@ RELOPT_OTHER_MEMBER_REL
Definition: pathnodes.h:819
RELOPT_JOINREL
@ RELOPT_JOINREL
Definition: pathnodes.h:818
RELOPT_OTHER_JOINREL
@ RELOPT_OTHER_JOINREL
Definition: pathnodes.h:820
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#define IS_OTHER_REL(rel)
Definition: pathnodes.h:844
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bool(* ec_matches_callback_type)(PlannerInfo *root, RelOptInfo *rel, EquivalenceClass *ec, EquivalenceMember *em, void *arg)
Definition: paths.h:122
arg
void * arg
Definition: pg_backup_utils.c:27
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while(p+4<=pend)
Definition: pg_crc32c_sse42.c:54
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#define lfirst(lc)
Definition: pg_list.h:172
lfirst_node
#define lfirst_node(type, lc)
Definition: pg_list.h:176
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static int list_length(const List *l)
Definition: pg_list.h:152
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#define linitial_node(type, l)
Definition: pg_list.h:181
NIL
#define NIL
Definition: pg_list.h:68
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#define foreach_current_index(var_or_cell)
Definition: pg_list.h:403
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#define foreach_delete_current(lst, var_or_cell)
Definition: pg_list.h:391
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#define list_make1(x1)
Definition: pg_list.h:212
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static ListCell * list_head(const List *l)
Definition: pg_list.h:128
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#define linitial(l)
Definition: pg_list.h:178
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#define lsecond(l)
Definition: pg_list.h:183
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static void * list_nth(const List *list, int n)
Definition: pg_list.h:299
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static ListCell * lnext(const List *l, const ListCell *c)
Definition: pg_list.h:343
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#define lfirst_oid(lc)
Definition: pg_list.h:174
pg_type.h
InvalidOid
#define InvalidOid
Definition: postgres_ext.h:36
Oid
unsigned int Oid
Definition: postgres_ext.h:31
COERCE_IMPLICIT_CAST
@ COERCE_IMPLICIT_CAST
Definition: primnodes.h:706
IS_NOT_NULL
@ IS_NOT_NULL
Definition: primnodes.h:1924
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root
tree ctl root
Definition: radixtree.h:1880
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static struct cvec * eclass(struct vars *v, chr c, int cases)
Definition: regc_locale.c:500
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Relids find_childrel_parents(PlannerInfo *root, RelOptInfo *rel)
Definition: relnode.c:1521
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RestrictInfo * make_restrictinfo(PlannerInfo *root, Expr *clause, bool is_pushed_down, bool has_clone, bool is_clone, bool pseudoconstant, Index security_level, Relids required_relids, Relids incompatible_relids, Relids outer_relids)
Definition: restrictinfo.c:63
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Node * remove_nulling_relids(Node *node, const Bitmapset *removable_relids, const Bitmapset *except_relids)
Definition: rewriteManip.c:1234
BTEqualStrategyNumber
#define BTEqualStrategyNumber
Definition: stratnum.h:31
CoalesceExpr::args
List * args
Definition: primnodes.h:1462
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Index ec_min_security
Definition: pathnodes.h:1390
EquivalenceClass::ec_opfamilies
List * ec_opfamilies
Definition: pathnodes.h:1379
EquivalenceClass::ec_merged
struct EquivalenceClass * ec_merged
Definition: pathnodes.h:1392
EquivalenceClass::ec_max_security
Index ec_max_security
Definition: pathnodes.h:1391
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JoinDomain * em_jdomain
Definition: pathnodes.h:1435
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struct EquivalenceClass * eclass[INDEX_MAX_KEYS]
Definition: pathnodes.h:1246
ForeignKeyOptInfo::fk_eclass_member
struct EquivalenceMember * fk_eclass_member[INDEX_MAX_KEYS]
Definition: pathnodes.h:1248
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struct RestrictInfo * rinfo
Definition: pathnodes.h:1747
JoinDomain::jd_relids
Relids jd_relids
Definition: pathnodes.h:1317
List
Definition: pg_list.h:54
Node
Definition: nodes.h:129
NullTest::nulltesttype
NullTestType nulltesttype
Definition: primnodes.h:1931
NullTest::location
ParseLoc location
Definition: primnodes.h:1934
NullTest::arg
Expr * arg
Definition: primnodes.h:1930
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RestrictInfo * rinfo
Definition: pathnodes.h:2911
OuterJoinClauseInfo::sjinfo
SpecialJoinInfo * sjinfo
Definition: pathnodes.h:2912
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List * exprs
Definition: pathnodes.h:1522
RelOptInfo::relids
Relids relids
Definition: pathnodes.h:861
RelOptInfo::reltarget
struct PathTarget * reltarget
Definition: pathnodes.h:883
RelOptInfo::top_parent_relids
Relids top_parent_relids
Definition: pathnodes.h:999
RelOptInfo::reloptkind
RelOptKind reloptkind
Definition: pathnodes.h:855
RelOptInfo::eclass_indexes
Bitmapset * eclass_indexes
Definition: pathnodes.h:942
RelOptInfo::has_eclass_joins
bool has_eclass_joins
Definition: pathnodes.h:983
RestrictInfo::is_pushed_down
bool is_pushed_down
Definition: pathnodes.h:2555
RestrictInfo::security_level
Index security_level
Definition: pathnodes.h:2574
RestrictInfo::required_relids
Relids required_relids
Definition: pathnodes.h:2583
RestrictInfo::rinfo_serial
int rinfo_serial
Definition: pathnodes.h:2624
RestrictInfo::outer_relids
Relids outer_relids
Definition: pathnodes.h:2589
RestrictInfo::incompatible_relids
Relids incompatible_relids
Definition: pathnodes.h:2586
RestrictInfo::clause
Expr * clause
Definition: pathnodes.h:2552
RestrictInfo::has_clone
bool has_clone
Definition: pathnodes.h:2564
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Relids syn_lefthand
Definition: pathnodes.h:2884
SpecialJoinInfo::syn_righthand
Relids syn_righthand
Definition: pathnodes.h:2885
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Expr * expr
Definition: primnodes.h:2162
Var
Definition: primnodes.h:248
Var::varattno
AttrNumber varattno
Definition: primnodes.h:260
Var::varno
int varno
Definition: primnodes.h:255
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Definition: regcomp.c:281
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static void callback(struct sockaddr *addr, struct sockaddr *mask, void *unused)
Definition: test_ifaddrs.c:46
pull_var_clause
List * pull_var_clause(Node *node, int flags)
Definition: var.c:607
pull_varnos
Relids pull_varnos(PlannerInfo *root, Node *node)
Definition: var.c:108