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