Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * pathkeys.c
4 : * Utilities for matching and building path keys
5 : *
6 : * See src/backend/optimizer/README for a great deal of information about
7 : * the nature and use of path keys.
8 : *
9 : *
10 : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
11 : * Portions Copyright (c) 1994, Regents of the University of California
12 : *
13 : * IDENTIFICATION
14 : * src/backend/optimizer/path/pathkeys.c
15 : *
16 : *-------------------------------------------------------------------------
17 : */
18 : #include "postgres.h"
19 :
20 : #include "access/stratnum.h"
21 : #include "catalog/pg_opfamily.h"
22 : #include "nodes/nodeFuncs.h"
23 : #include "optimizer/cost.h"
24 : #include "optimizer/optimizer.h"
25 : #include "optimizer/pathnode.h"
26 : #include "optimizer/paths.h"
27 : #include "partitioning/partbounds.h"
28 : #include "rewrite/rewriteManip.h"
29 : #include "utils/lsyscache.h"
30 :
31 : /* Consider reordering of GROUP BY keys? */
32 : bool enable_group_by_reordering = true;
33 :
34 : static bool pathkey_is_redundant(PathKey *new_pathkey, List *pathkeys);
35 : static bool matches_boolean_partition_clause(RestrictInfo *rinfo,
36 : RelOptInfo *partrel,
37 : int partkeycol);
38 : static Var *find_var_for_subquery_tle(RelOptInfo *rel, TargetEntry *tle);
39 : static bool right_merge_direction(PlannerInfo *root, PathKey *pathkey);
40 :
41 :
42 : /****************************************************************************
43 : * PATHKEY CONSTRUCTION AND REDUNDANCY TESTING
44 : ****************************************************************************/
45 :
46 : /*
47 : * make_canonical_pathkey
48 : * Given the parameters for a PathKey, find any pre-existing matching
49 : * pathkey in the query's list of "canonical" pathkeys. Make a new
50 : * entry if there's not one already.
51 : *
52 : * Note that this function must not be used until after we have completed
53 : * merging EquivalenceClasses.
54 : */
55 : PathKey *
56 1201731 : make_canonical_pathkey(PlannerInfo *root,
57 : EquivalenceClass *eclass, Oid opfamily,
58 : CompareType cmptype, bool nulls_first)
59 : {
60 : PathKey *pk;
61 : ListCell *lc;
62 : MemoryContext oldcontext;
63 :
64 : /* Can't make canonical pathkeys if the set of ECs might still change */
65 1201731 : if (!root->ec_merging_done)
66 0 : elog(ERROR, "too soon to build canonical pathkeys");
67 :
68 : /* The passed eclass might be non-canonical, so chase up to the top */
69 1201731 : while (eclass->ec_merged)
70 0 : eclass = eclass->ec_merged;
71 :
72 6139649 : foreach(lc, root->canon_pathkeys)
73 : {
74 5789181 : pk = (PathKey *) lfirst(lc);
75 5789181 : if (eclass == pk->pk_eclass &&
76 1138372 : opfamily == pk->pk_opfamily &&
77 1138372 : cmptype == pk->pk_cmptype &&
78 851293 : nulls_first == pk->pk_nulls_first)
79 851263 : return pk;
80 : }
81 :
82 : /*
83 : * Be sure canonical pathkeys are allocated in the main planning context.
84 : * Not an issue in normal planning, but it is for GEQO.
85 : */
86 350468 : oldcontext = MemoryContextSwitchTo(root->planner_cxt);
87 :
88 350468 : pk = makeNode(PathKey);
89 350468 : pk->pk_eclass = eclass;
90 350468 : pk->pk_opfamily = opfamily;
91 350468 : pk->pk_cmptype = cmptype;
92 350468 : pk->pk_nulls_first = nulls_first;
93 :
94 350468 : root->canon_pathkeys = lappend(root->canon_pathkeys, pk);
95 :
96 350468 : MemoryContextSwitchTo(oldcontext);
97 :
98 350468 : return pk;
99 : }
100 :
101 : /*
102 : * append_pathkeys
103 : * Append all non-redundant PathKeys in 'source' onto 'target' and
104 : * returns the updated 'target' list.
105 : */
106 : List *
107 755 : append_pathkeys(List *target, List *source)
108 : {
109 : ListCell *lc;
110 :
111 : Assert(target != NIL);
112 :
113 1543 : foreach(lc, source)
114 : {
115 788 : PathKey *pk = lfirst_node(PathKey, lc);
116 :
117 788 : if (!pathkey_is_redundant(pk, target))
118 701 : target = lappend(target, pk);
119 : }
120 755 : return target;
121 : }
122 :
123 : /*
124 : * pathkey_is_redundant
125 : * Is a pathkey redundant with one already in the given list?
126 : *
127 : * We detect two cases:
128 : *
129 : * 1. If the new pathkey's equivalence class contains a constant, and isn't
130 : * below an outer join, then we can disregard it as a sort key. An example:
131 : * SELECT ... WHERE x = 42 ORDER BY x, y;
132 : * We may as well just sort by y. Note that because of opfamily matching,
133 : * this is semantically correct: we know that the equality constraint is one
134 : * that actually binds the variable to a single value in the terms of any
135 : * ordering operator that might go with the eclass. This rule not only lets
136 : * us simplify (or even skip) explicit sorts, but also allows matching index
137 : * sort orders to a query when there are don't-care index columns.
138 : *
139 : * 2. If the new pathkey's equivalence class is the same as that of any
140 : * existing member of the pathkey list, then it is redundant. Some examples:
141 : * SELECT ... ORDER BY x, x;
142 : * SELECT ... ORDER BY x, x DESC;
143 : * SELECT ... WHERE x = y ORDER BY x, y;
144 : * In all these cases the second sort key cannot distinguish values that are
145 : * considered equal by the first, and so there's no point in using it.
146 : * Note in particular that we need not compare opfamily (all the opfamilies
147 : * of the EC have the same notion of equality) nor sort direction.
148 : *
149 : * Both the given pathkey and the list members must be canonical for this
150 : * to work properly, but that's okay since we no longer ever construct any
151 : * non-canonical pathkeys. (Note: the notion of a pathkey *list* being
152 : * canonical includes the additional requirement of no redundant entries,
153 : * which is exactly what we are checking for here.)
154 : *
155 : * Because the equivclass.c machinery forms only one copy of any EC per query,
156 : * pointer comparison is enough to decide whether canonical ECs are the same.
157 : */
158 : static bool
159 1396332 : pathkey_is_redundant(PathKey *new_pathkey, List *pathkeys)
160 : {
161 1396332 : EquivalenceClass *new_ec = new_pathkey->pk_eclass;
162 : ListCell *lc;
163 :
164 : /* Check for EC containing a constant --- unconditionally redundant */
165 1396332 : if (EC_MUST_BE_REDUNDANT(new_ec))
166 172971 : return true;
167 :
168 : /* If same EC already used in list, then redundant */
169 1476880 : foreach(lc, pathkeys)
170 : {
171 253992 : PathKey *old_pathkey = (PathKey *) lfirst(lc);
172 :
173 253992 : if (new_ec == old_pathkey->pk_eclass)
174 473 : return true;
175 : }
176 :
177 1222888 : return false;
178 : }
179 :
180 : /*
181 : * make_pathkey_from_sortinfo
182 : * Given an expression and sort-order information, create a PathKey.
183 : * The result is always a "canonical" PathKey, but it might be redundant.
184 : *
185 : * If the PathKey is being generated from a SortGroupClause, sortref should be
186 : * the SortGroupClause's SortGroupRef; otherwise zero.
187 : *
188 : * If rel is not NULL, it identifies a specific relation we're considering
189 : * a path for, and indicates that child EC members for that relation can be
190 : * considered. Otherwise child members are ignored. (See the comments for
191 : * get_eclass_for_sort_expr.)
192 : *
193 : * create_it is true if we should create any missing EquivalenceClass
194 : * needed to represent the sort key. If it's false, we return NULL if the
195 : * sort key isn't already present in any EquivalenceClass.
196 : */
197 : static PathKey *
198 1019711 : make_pathkey_from_sortinfo(PlannerInfo *root,
199 : Expr *expr,
200 : Oid opfamily,
201 : Oid opcintype,
202 : Oid collation,
203 : bool reverse_sort,
204 : bool nulls_first,
205 : Index sortref,
206 : Relids rel,
207 : bool create_it)
208 : {
209 : CompareType cmptype;
210 : Oid equality_op;
211 : List *opfamilies;
212 : EquivalenceClass *eclass;
213 :
214 1019711 : cmptype = reverse_sort ? COMPARE_GT : COMPARE_LT;
215 :
216 : /*
217 : * EquivalenceClasses need to contain opfamily lists based on the family
218 : * membership of mergejoinable equality operators, which could belong to
219 : * more than one opfamily. So we have to look up the opfamily's equality
220 : * operator and get its membership.
221 : */
222 1019711 : equality_op = get_opfamily_member_for_cmptype(opfamily,
223 : opcintype,
224 : opcintype,
225 : COMPARE_EQ);
226 1019711 : if (!OidIsValid(equality_op)) /* shouldn't happen */
227 0 : elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
228 : COMPARE_EQ, opcintype, opcintype, opfamily);
229 1019711 : opfamilies = get_mergejoin_opfamilies(equality_op);
230 1019711 : if (!opfamilies) /* certainly should find some */
231 0 : elog(ERROR, "could not find opfamilies for equality operator %u",
232 : equality_op);
233 :
234 : /* Now find or (optionally) create a matching EquivalenceClass */
235 1019711 : eclass = get_eclass_for_sort_expr(root, expr,
236 : opfamilies, opcintype, collation,
237 : sortref, rel, create_it);
238 :
239 : /* Fail if no EC and !create_it */
240 1019711 : if (!eclass)
241 345243 : return NULL;
242 :
243 : /* And finally we can find or create a PathKey node */
244 674468 : return make_canonical_pathkey(root, eclass, opfamily,
245 : cmptype, nulls_first);
246 : }
247 :
248 : /*
249 : * make_pathkey_from_sortop
250 : * Like make_pathkey_from_sortinfo, but work from a sort operator.
251 : *
252 : * This should eventually go away, but we need to restructure SortGroupClause
253 : * first.
254 : */
255 : static PathKey *
256 100191 : make_pathkey_from_sortop(PlannerInfo *root,
257 : Expr *expr,
258 : Oid ordering_op,
259 : bool reverse_sort,
260 : bool nulls_first,
261 : Index sortref,
262 : bool create_it)
263 : {
264 : Oid opfamily,
265 : opcintype,
266 : collation;
267 : CompareType cmptype;
268 :
269 : /* Find the operator in pg_amop --- failure shouldn't happen */
270 100191 : if (!get_ordering_op_properties(ordering_op,
271 : &opfamily, &opcintype, &cmptype))
272 0 : elog(ERROR, "operator %u is not a valid ordering operator",
273 : ordering_op);
274 :
275 : /* Because SortGroupClause doesn't carry collation, consult the expr */
276 100191 : collation = exprCollation((Node *) expr);
277 :
278 100191 : return make_pathkey_from_sortinfo(root,
279 : expr,
280 : opfamily,
281 : opcintype,
282 : collation,
283 : reverse_sort,
284 : nulls_first,
285 : sortref,
286 : NULL,
287 : create_it);
288 : }
289 :
290 :
291 : /****************************************************************************
292 : * PATHKEY COMPARISONS
293 : ****************************************************************************/
294 :
295 : /*
296 : * compare_pathkeys
297 : * Compare two pathkeys to see if they are equivalent, and if not whether
298 : * one is "better" than the other.
299 : *
300 : * We assume the pathkeys are canonical, and so they can be checked for
301 : * equality by simple pointer comparison.
302 : */
303 : PathKeysComparison
304 7014117 : compare_pathkeys(List *keys1, List *keys2)
305 : {
306 : ListCell *key1,
307 : *key2;
308 :
309 : /*
310 : * Fall out quickly if we are passed two identical lists. This mostly
311 : * catches the case where both are NIL, but that's common enough to
312 : * warrant the test.
313 : */
314 7014117 : if (keys1 == keys2)
315 2718215 : return PATHKEYS_EQUAL;
316 :
317 5410642 : forboth(key1, keys1, key2, keys2)
318 : {
319 1556802 : PathKey *pathkey1 = (PathKey *) lfirst(key1);
320 1556802 : PathKey *pathkey2 = (PathKey *) lfirst(key2);
321 :
322 1556802 : if (pathkey1 != pathkey2)
323 442062 : return PATHKEYS_DIFFERENT; /* no need to keep looking */
324 : }
325 :
326 : /*
327 : * If we reached the end of only one list, the other is longer and
328 : * therefore not a subset.
329 : */
330 3853840 : if (key1 != NULL)
331 2485477 : return PATHKEYS_BETTER1; /* key1 is longer */
332 1368363 : if (key2 != NULL)
333 499609 : return PATHKEYS_BETTER2; /* key2 is longer */
334 868754 : return PATHKEYS_EQUAL;
335 : }
336 :
337 : /*
338 : * pathkeys_contained_in
339 : * Common special case of compare_pathkeys: we just want to know
340 : * if keys2 are at least as well sorted as keys1.
341 : */
342 : bool
343 2234905 : pathkeys_contained_in(List *keys1, List *keys2)
344 : {
345 2234905 : switch (compare_pathkeys(keys1, keys2))
346 : {
347 592579 : case PATHKEYS_EQUAL:
348 : case PATHKEYS_BETTER2:
349 592579 : return true;
350 1642326 : default:
351 1642326 : break;
352 : }
353 1642326 : return false;
354 : }
355 :
356 : /*
357 : * group_keys_reorder_by_pathkeys
358 : * Reorder GROUP BY pathkeys and clauses to match the input pathkeys.
359 : *
360 : * 'pathkeys' is an input list of pathkeys
361 : * '*group_pathkeys' and '*group_clauses' are pathkeys and clauses lists to
362 : * reorder. The pointers are redirected to new lists, original lists
363 : * stay untouched.
364 : * 'num_groupby_pathkeys' is the number of first '*group_pathkeys' items to
365 : * search matching pathkeys.
366 : *
367 : * Returns the number of GROUP BY keys with a matching pathkey.
368 : */
369 : static int
370 82 : group_keys_reorder_by_pathkeys(List *pathkeys, List **group_pathkeys,
371 : List **group_clauses,
372 : int num_groupby_pathkeys)
373 : {
374 82 : List *new_group_pathkeys = NIL,
375 82 : *new_group_clauses = NIL;
376 : List *grouping_pathkeys;
377 : ListCell *lc;
378 : int n;
379 :
380 82 : if (pathkeys == NIL || *group_pathkeys == NIL)
381 0 : return 0;
382 :
383 : /*
384 : * We're going to search within just the first num_groupby_pathkeys of
385 : * *group_pathkeys. The thing is that root->group_pathkeys is passed as
386 : * *group_pathkeys containing grouping pathkeys altogether with aggregate
387 : * pathkeys. If we process aggregate pathkeys we could get an invalid
388 : * result of get_sortgroupref_clause_noerr(), because their
389 : * pathkey->pk_eclass->ec_sortref doesn't reference query targetlist. So,
390 : * we allocate a separate list of pathkeys for lookups.
391 : */
392 82 : grouping_pathkeys = list_copy_head(*group_pathkeys, num_groupby_pathkeys);
393 :
394 : /*
395 : * Walk the pathkeys (determining ordering of the input path) and see if
396 : * there's a matching GROUP BY key. If we find one, we append it to the
397 : * list, and do the same for the clauses.
398 : *
399 : * Once we find the first pathkey without a matching GROUP BY key, the
400 : * rest of the pathkeys are useless and can't be used to evaluate the
401 : * grouping, so we abort the loop and ignore the remaining pathkeys.
402 : */
403 199 : foreach(lc, pathkeys)
404 : {
405 130 : PathKey *pathkey = (PathKey *) lfirst(lc);
406 : SortGroupClause *sgc;
407 :
408 : /*
409 : * Pathkeys are built in a way that allows simply comparing pointers.
410 : * Give up if we can't find the matching pointer. Also give up if
411 : * there is no sortclause reference for some reason.
412 : */
413 130 : if (foreach_current_index(lc) >= num_groupby_pathkeys ||
414 127 : !list_member_ptr(grouping_pathkeys, pathkey) ||
415 117 : pathkey->pk_eclass->ec_sortref == 0)
416 : break;
417 :
418 : /*
419 : * Since 1349d27 pathkey coming from underlying node can be in the
420 : * root->group_pathkeys but not in the processed_groupClause. So, we
421 : * should be careful here.
422 : */
423 117 : sgc = get_sortgroupref_clause_noerr(pathkey->pk_eclass->ec_sortref,
424 : *group_clauses);
425 117 : if (!sgc)
426 : /* The grouping clause does not cover this pathkey */
427 0 : break;
428 :
429 : /*
430 : * Sort group clause should have an ordering operator as long as there
431 : * is an associated pathkey.
432 : */
433 : Assert(OidIsValid(sgc->sortop));
434 :
435 117 : new_group_pathkeys = lappend(new_group_pathkeys, pathkey);
436 117 : new_group_clauses = lappend(new_group_clauses, sgc);
437 : }
438 :
439 : /* remember the number of pathkeys with a matching GROUP BY key */
440 82 : n = list_length(new_group_pathkeys);
441 :
442 : /* append the remaining group pathkeys (will be treated as not sorted) */
443 82 : *group_pathkeys = list_concat_unique_ptr(new_group_pathkeys,
444 : *group_pathkeys);
445 82 : *group_clauses = list_concat_unique_ptr(new_group_clauses,
446 : *group_clauses);
447 :
448 82 : list_free(grouping_pathkeys);
449 82 : return n;
450 : }
451 :
452 : /*
453 : * get_useful_group_keys_orderings
454 : * Determine which orderings of GROUP BY keys are potentially interesting.
455 : *
456 : * Returns a list of GroupByOrdering items, each representing an interesting
457 : * ordering of GROUP BY keys. Each item stores pathkeys and clauses in the
458 : * matching order.
459 : *
460 : * The function considers (and keeps) following GROUP BY orderings:
461 : *
462 : * - GROUP BY keys as ordered by preprocess_groupclause() to match target
463 : * ORDER BY clause (as much as possible),
464 : * - GROUP BY keys reordered to match 'path' ordering (as much as possible).
465 : */
466 : List *
467 29992 : get_useful_group_keys_orderings(PlannerInfo *root, Path *path)
468 : {
469 29992 : Query *parse = root->parse;
470 29992 : List *infos = NIL;
471 : GroupByOrdering *info;
472 :
473 29992 : List *pathkeys = root->group_pathkeys;
474 29992 : List *clauses = root->processed_groupClause;
475 :
476 : /* always return at least the original pathkeys/clauses */
477 29992 : info = makeNode(GroupByOrdering);
478 29992 : info->pathkeys = pathkeys;
479 29992 : info->clauses = clauses;
480 29992 : infos = lappend(infos, info);
481 :
482 : /*
483 : * Should we try generating alternative orderings of the group keys? If
484 : * not, we produce only the order specified in the query, i.e. the
485 : * optimization is effectively disabled.
486 : */
487 29992 : if (!enable_group_by_reordering)
488 0 : return infos;
489 :
490 : /*
491 : * Grouping sets have own and more complex logic to decide the ordering.
492 : */
493 29992 : if (parse->groupingSets)
494 534 : return infos;
495 :
496 : /*
497 : * If the path is sorted in some way, try reordering the group keys to
498 : * match the path as much of the ordering as possible. Then thanks to
499 : * incremental sort we would get this sort as cheap as possible.
500 : */
501 29458 : if (path->pathkeys &&
502 2881 : !pathkeys_contained_in(path->pathkeys, root->group_pathkeys))
503 : {
504 : int n;
505 :
506 82 : n = group_keys_reorder_by_pathkeys(path->pathkeys, &pathkeys, &clauses,
507 : root->num_groupby_pathkeys);
508 :
509 82 : if (n > 0 &&
510 144 : (enable_incremental_sort || n == root->num_groupby_pathkeys) &&
511 72 : compare_pathkeys(pathkeys, root->group_pathkeys) != PATHKEYS_EQUAL)
512 : {
513 72 : info = makeNode(GroupByOrdering);
514 72 : info->pathkeys = pathkeys;
515 72 : info->clauses = clauses;
516 :
517 72 : infos = lappend(infos, info);
518 : }
519 : }
520 :
521 : #ifdef USE_ASSERT_CHECKING
522 : {
523 : GroupByOrdering *pinfo = linitial_node(GroupByOrdering, infos);
524 : ListCell *lc;
525 :
526 : /* Test consistency of info structures */
527 : for_each_from(lc, infos, 1)
528 : {
529 : ListCell *lc1,
530 : *lc2;
531 :
532 : info = lfirst_node(GroupByOrdering, lc);
533 :
534 : Assert(list_length(info->clauses) == list_length(pinfo->clauses));
535 : Assert(list_length(info->pathkeys) == list_length(pinfo->pathkeys));
536 : Assert(list_difference(info->clauses, pinfo->clauses) == NIL);
537 : Assert(list_difference_ptr(info->pathkeys, pinfo->pathkeys) == NIL);
538 :
539 : forboth(lc1, info->clauses, lc2, info->pathkeys)
540 : {
541 : SortGroupClause *sgc = lfirst_node(SortGroupClause, lc1);
542 : PathKey *pk = lfirst_node(PathKey, lc2);
543 :
544 : Assert(pk->pk_eclass->ec_sortref == sgc->tleSortGroupRef);
545 : }
546 : }
547 : }
548 : #endif
549 29458 : return infos;
550 : }
551 :
552 : /*
553 : * pathkeys_count_contained_in
554 : * Same as pathkeys_contained_in, but also sets length of longest
555 : * common prefix of keys1 and keys2.
556 : */
557 : bool
558 3910262 : pathkeys_count_contained_in(List *keys1, List *keys2, int *n_common)
559 : {
560 3910262 : int n = 0;
561 : ListCell *key1,
562 : *key2;
563 :
564 : /*
565 : * See if we can avoiding looping through both lists. This optimization
566 : * gains us several percent in planning time in a worst-case test.
567 : */
568 3910262 : if (keys1 == keys2)
569 : {
570 383140 : *n_common = list_length(keys1);
571 383140 : return true;
572 : }
573 3527122 : else if (keys1 == NIL)
574 : {
575 2026878 : *n_common = 0;
576 2026878 : return true;
577 : }
578 1500244 : else if (keys2 == NIL)
579 : {
580 808420 : *n_common = 0;
581 808420 : return false;
582 : }
583 :
584 : /*
585 : * If both lists are non-empty, iterate through both to find out how many
586 : * items are shared.
587 : */
588 953381 : forboth(key1, keys1, key2, keys2)
589 : {
590 713417 : PathKey *pathkey1 = (PathKey *) lfirst(key1);
591 713417 : PathKey *pathkey2 = (PathKey *) lfirst(key2);
592 :
593 713417 : if (pathkey1 != pathkey2)
594 : {
595 451860 : *n_common = n;
596 451860 : return false;
597 : }
598 261557 : n++;
599 : }
600 :
601 : /* If we ended with a null value, then we've processed the whole list. */
602 239964 : *n_common = n;
603 239964 : return (key1 == NULL);
604 : }
605 :
606 : /*
607 : * get_cheapest_path_for_pathkeys
608 : * Find the cheapest path (according to the specified criterion) that
609 : * satisfies the given pathkeys and parameterization, and is parallel-safe
610 : * if required.
611 : * Return NULL if no such path.
612 : *
613 : * 'paths' is a list of possible paths that all generate the same relation
614 : * 'pathkeys' represents a required ordering (in canonical form!)
615 : * 'required_outer' denotes allowable outer relations for parameterized paths
616 : * 'cost_criterion' is STARTUP_COST or TOTAL_COST
617 : * 'require_parallel_safe' causes us to consider only parallel-safe paths
618 : */
619 : Path *
620 554117 : get_cheapest_path_for_pathkeys(List *paths, List *pathkeys,
621 : Relids required_outer,
622 : CostSelector cost_criterion,
623 : bool require_parallel_safe)
624 : {
625 554117 : Path *matched_path = NULL;
626 : ListCell *l;
627 :
628 1940641 : foreach(l, paths)
629 : {
630 1386524 : Path *path = (Path *) lfirst(l);
631 :
632 : /* If required, reject paths that are not parallel-safe */
633 1386524 : if (require_parallel_safe && !path->parallel_safe)
634 2814 : continue;
635 :
636 : /*
637 : * Since cost comparison is a lot cheaper than pathkey comparison, do
638 : * that first. (XXX is that still true?)
639 : */
640 1445799 : if (matched_path != NULL &&
641 62089 : compare_path_costs(matched_path, path, cost_criterion) <= 0)
642 51361 : continue;
643 :
644 1886579 : if (pathkeys_contained_in(pathkeys, path->pathkeys) &&
645 554230 : bms_is_subset(PATH_REQ_OUTER(path), required_outer))
646 349742 : matched_path = path;
647 : }
648 554117 : return matched_path;
649 : }
650 :
651 : /*
652 : * get_cheapest_fractional_path_for_pathkeys
653 : * Find the cheapest path (for retrieving a specified fraction of all
654 : * the tuples) that satisfies the given pathkeys and parameterization.
655 : * Return NULL if no such path.
656 : *
657 : * See compare_fractional_path_costs() for the interpretation of the fraction
658 : * parameter.
659 : *
660 : * 'paths' is a list of possible paths that all generate the same relation
661 : * 'pathkeys' represents a required ordering (in canonical form!)
662 : * 'required_outer' denotes allowable outer relations for parameterized paths
663 : * 'fraction' is the fraction of the total tuples expected to be retrieved
664 : */
665 : Path *
666 1003 : get_cheapest_fractional_path_for_pathkeys(List *paths,
667 : List *pathkeys,
668 : Relids required_outer,
669 : double fraction)
670 : {
671 1003 : Path *matched_path = NULL;
672 : ListCell *l;
673 :
674 2827 : foreach(l, paths)
675 : {
676 1824 : Path *path = (Path *) lfirst(l);
677 :
678 : /*
679 : * Since cost comparison is a lot cheaper than pathkey comparison, do
680 : * that first. (XXX is that still true?)
681 : */
682 2009 : if (matched_path != NULL &&
683 185 : compare_fractional_path_costs(matched_path, path, fraction) <= 0)
684 110 : continue;
685 :
686 2479 : if (pathkeys_contained_in(pathkeys, path->pathkeys) &&
687 765 : bms_is_subset(PATH_REQ_OUTER(path), required_outer))
688 667 : matched_path = path;
689 : }
690 1003 : return matched_path;
691 : }
692 :
693 :
694 : /*
695 : * get_cheapest_parallel_safe_total_inner
696 : * Find the unparameterized parallel-safe path with the least total cost.
697 : */
698 : Path *
699 40319 : get_cheapest_parallel_safe_total_inner(List *paths)
700 : {
701 : ListCell *l;
702 :
703 43975 : foreach(l, paths)
704 : {
705 43311 : Path *innerpath = (Path *) lfirst(l);
706 :
707 43311 : if (innerpath->parallel_safe &&
708 42218 : bms_is_empty(PATH_REQ_OUTER(innerpath)))
709 39655 : return innerpath;
710 : }
711 :
712 664 : return NULL;
713 : }
714 :
715 : /****************************************************************************
716 : * NEW PATHKEY FORMATION
717 : ****************************************************************************/
718 :
719 : /*
720 : * build_index_pathkeys
721 : * Build a pathkeys list that describes the ordering induced by an index
722 : * scan using the given index. (Note that an unordered index doesn't
723 : * induce any ordering, so we return NIL.)
724 : *
725 : * If 'scandir' is BackwardScanDirection, build pathkeys representing a
726 : * backwards scan of the index.
727 : *
728 : * We iterate only key columns of covering indexes, since non-key columns
729 : * don't influence index ordering. The result is canonical, meaning that
730 : * redundant pathkeys are removed; it may therefore have fewer entries than
731 : * there are key columns in the index.
732 : *
733 : * Another reason for stopping early is that we may be able to tell that
734 : * an index column's sort order is uninteresting for this query. However,
735 : * that test is just based on the existence of an EquivalenceClass and not
736 : * on position in pathkey lists, so it's not complete. Caller should call
737 : * truncate_useless_pathkeys() to possibly remove more pathkeys.
738 : */
739 : List *
740 678204 : build_index_pathkeys(PlannerInfo *root,
741 : IndexOptInfo *index,
742 : ScanDirection scandir)
743 : {
744 678204 : List *retval = NIL;
745 : ListCell *lc;
746 : int i;
747 :
748 678204 : if (index->sortopfamily == NULL)
749 0 : return NIL; /* non-orderable index */
750 :
751 678204 : i = 0;
752 1235524 : foreach(lc, index->indextlist)
753 : {
754 893690 : TargetEntry *indextle = (TargetEntry *) lfirst(lc);
755 : Expr *indexkey;
756 : bool reverse_sort;
757 : bool nulls_first;
758 : PathKey *cpathkey;
759 :
760 : /*
761 : * INCLUDE columns are stored in index unordered, so they don't
762 : * support ordered index scan.
763 : */
764 893690 : if (i >= index->nkeycolumns)
765 0 : break;
766 :
767 : /* We assume we don't need to make a copy of the tlist item */
768 893690 : indexkey = indextle->expr;
769 :
770 893690 : if (ScanDirectionIsBackward(scandir))
771 : {
772 446845 : reverse_sort = !index->reverse_sort[i];
773 446845 : nulls_first = !index->nulls_first[i];
774 : }
775 : else
776 : {
777 446845 : reverse_sort = index->reverse_sort[i];
778 446845 : nulls_first = index->nulls_first[i];
779 : }
780 :
781 : /*
782 : * OK, try to make a canonical pathkey for this sort key.
783 : */
784 893690 : cpathkey = make_pathkey_from_sortinfo(root,
785 : indexkey,
786 893690 : index->sortopfamily[i],
787 893690 : index->opcintype[i],
788 893690 : index->indexcollations[i],
789 : reverse_sort,
790 : nulls_first,
791 : 0,
792 893690 : index->rel->relids,
793 : false);
794 :
795 893690 : if (cpathkey)
796 : {
797 : /*
798 : * We found the sort key in an EquivalenceClass, so it's relevant
799 : * for this query. Add it to list, unless it's redundant.
800 : */
801 556608 : if (!pathkey_is_redundant(cpathkey, retval))
802 403140 : retval = lappend(retval, cpathkey);
803 : }
804 : else
805 : {
806 : /*
807 : * Boolean index keys might be redundant even if they do not
808 : * appear in an EquivalenceClass, because of our special treatment
809 : * of boolean equality conditions --- see the comment for
810 : * indexcol_is_bool_constant_for_query(). If that applies, we can
811 : * continue to examine lower-order index columns. Otherwise, the
812 : * sort key is not an interesting sort order for this query, so we
813 : * should stop considering index columns; any lower-order sort
814 : * keys won't be useful either.
815 : */
816 337082 : if (!indexcol_is_bool_constant_for_query(root, index, i))
817 336370 : break;
818 : }
819 :
820 557320 : i++;
821 : }
822 :
823 678204 : return retval;
824 : }
825 :
826 : /*
827 : * partkey_is_bool_constant_for_query
828 : *
829 : * If a partition key column is constrained to have a constant value by the
830 : * query's WHERE conditions, then it's irrelevant for sort-order
831 : * considerations. Usually that means we have a restriction clause
832 : * WHERE partkeycol = constant, which gets turned into an EquivalenceClass
833 : * containing a constant, which is recognized as redundant by
834 : * build_partition_pathkeys(). But if the partition key column is a
835 : * boolean variable (or expression), then we are not going to see such a
836 : * WHERE clause, because expression preprocessing will have simplified it
837 : * to "WHERE partkeycol" or "WHERE NOT partkeycol". So we are not going
838 : * to have a matching EquivalenceClass (unless the query also contains
839 : * "ORDER BY partkeycol"). To allow such cases to work the same as they would
840 : * for non-boolean values, this function is provided to detect whether the
841 : * specified partition key column matches a boolean restriction clause.
842 : */
843 : static bool
844 7966 : partkey_is_bool_constant_for_query(RelOptInfo *partrel, int partkeycol)
845 : {
846 7966 : PartitionScheme partscheme = partrel->part_scheme;
847 : ListCell *lc;
848 :
849 : /*
850 : * If the partkey isn't boolean, we can't possibly get a match.
851 : *
852 : * Partitioning currently can only use built-in AMs, so checking for
853 : * built-in boolean opfamilies is good enough.
854 : */
855 7966 : if (!IsBuiltinBooleanOpfamily(partscheme->partopfamily[partkeycol]))
856 7726 : return false;
857 :
858 : /* Check each restriction clause for the partitioned rel */
859 396 : foreach(lc, partrel->baserestrictinfo)
860 : {
861 276 : RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
862 :
863 : /* Ignore pseudoconstant quals, they won't match */
864 276 : if (rinfo->pseudoconstant)
865 0 : continue;
866 :
867 : /* See if we can match the clause's expression to the partkey column */
868 276 : if (matches_boolean_partition_clause(rinfo, partrel, partkeycol))
869 120 : return true;
870 : }
871 :
872 120 : return false;
873 : }
874 :
875 : /*
876 : * matches_boolean_partition_clause
877 : * Determine if the boolean clause described by rinfo matches
878 : * partrel's partkeycol-th partition key column.
879 : *
880 : * "Matches" can be either an exact match (equivalent to partkey = true),
881 : * or a NOT above an exact match (equivalent to partkey = false).
882 : */
883 : static bool
884 276 : matches_boolean_partition_clause(RestrictInfo *rinfo,
885 : RelOptInfo *partrel, int partkeycol)
886 : {
887 276 : Node *clause = (Node *) rinfo->clause;
888 276 : Node *partexpr = (Node *) linitial(partrel->partexprs[partkeycol]);
889 :
890 : /* Direct match? */
891 276 : if (equal(partexpr, clause))
892 60 : return true;
893 : /* NOT clause? */
894 216 : else if (is_notclause(clause))
895 : {
896 72 : Node *arg = (Node *) get_notclausearg((Expr *) clause);
897 :
898 72 : if (equal(partexpr, arg))
899 60 : return true;
900 : }
901 :
902 156 : return false;
903 : }
904 :
905 : /*
906 : * build_partition_pathkeys
907 : * Build a pathkeys list that describes the ordering induced by the
908 : * partitions of partrel, under either forward or backward scan
909 : * as per scandir.
910 : *
911 : * Caller must have checked that the partitions are properly ordered,
912 : * as detected by partitions_are_ordered().
913 : *
914 : * Sets *partialkeys to true if pathkeys were only built for a prefix of the
915 : * partition key, or false if the pathkeys include all columns of the
916 : * partition key.
917 : */
918 : List *
919 24366 : build_partition_pathkeys(PlannerInfo *root, RelOptInfo *partrel,
920 : ScanDirection scandir, bool *partialkeys)
921 : {
922 24366 : List *retval = NIL;
923 24366 : PartitionScheme partscheme = partrel->part_scheme;
924 : int i;
925 :
926 : Assert(partscheme != NULL);
927 : Assert(partitions_are_ordered(partrel->boundinfo, partrel->live_parts));
928 : /* For now, we can only cope with baserels */
929 : Assert(IS_SIMPLE_REL(partrel));
930 :
931 41876 : for (i = 0; i < partscheme->partnatts; i++)
932 : {
933 : PathKey *cpathkey;
934 25356 : Expr *keyCol = (Expr *) linitial(partrel->partexprs[i]);
935 :
936 : /*
937 : * Try to make a canonical pathkey for this partkey.
938 : *
939 : * We assume the PartitionDesc lists any NULL partition last, so we
940 : * treat the scan like a NULLS LAST index: we have nulls_first for
941 : * backwards scan only.
942 : */
943 25356 : cpathkey = make_pathkey_from_sortinfo(root,
944 : keyCol,
945 25356 : partscheme->partopfamily[i],
946 25356 : partscheme->partopcintype[i],
947 25356 : partscheme->partcollation[i],
948 : ScanDirectionIsBackward(scandir),
949 : ScanDirectionIsBackward(scandir),
950 : 0,
951 : partrel->relids,
952 : false);
953 :
954 :
955 25356 : if (cpathkey)
956 : {
957 : /*
958 : * We found the sort key in an EquivalenceClass, so it's relevant
959 : * for this query. Add it to list, unless it's redundant.
960 : */
961 17390 : if (!pathkey_is_redundant(cpathkey, retval))
962 6914 : retval = lappend(retval, cpathkey);
963 : }
964 : else
965 : {
966 : /*
967 : * Boolean partition keys might be redundant even if they do not
968 : * appear in an EquivalenceClass, because of our special treatment
969 : * of boolean equality conditions --- see the comment for
970 : * partkey_is_bool_constant_for_query(). If that applies, we can
971 : * continue to examine lower-order partition keys. Otherwise, the
972 : * sort key is not an interesting sort order for this query, so we
973 : * should stop considering partition columns; any lower-order sort
974 : * keys won't be useful either.
975 : */
976 7966 : if (!partkey_is_bool_constant_for_query(partrel, i))
977 : {
978 7846 : *partialkeys = true;
979 7846 : return retval;
980 : }
981 : }
982 : }
983 :
984 16520 : *partialkeys = false;
985 16520 : return retval;
986 : }
987 :
988 : /*
989 : * build_expression_pathkey
990 : * Build a pathkeys list that describes an ordering by a single expression
991 : * using the given sort operator.
992 : *
993 : * expr and rel are as for make_pathkey_from_sortinfo.
994 : * We induce the other arguments assuming default sort order for the operator.
995 : *
996 : * Similarly to make_pathkey_from_sortinfo, the result is NIL if create_it
997 : * is false and the expression isn't already in some EquivalenceClass.
998 : */
999 : List *
1000 474 : build_expression_pathkey(PlannerInfo *root,
1001 : Expr *expr,
1002 : Oid opno,
1003 : Relids rel,
1004 : bool create_it)
1005 : {
1006 : List *pathkeys;
1007 : Oid opfamily,
1008 : opcintype;
1009 : CompareType cmptype;
1010 : PathKey *cpathkey;
1011 :
1012 : /* Find the operator in pg_amop --- failure shouldn't happen */
1013 474 : if (!get_ordering_op_properties(opno,
1014 : &opfamily, &opcintype, &cmptype))
1015 0 : elog(ERROR, "operator %u is not a valid ordering operator",
1016 : opno);
1017 :
1018 474 : cpathkey = make_pathkey_from_sortinfo(root,
1019 : expr,
1020 : opfamily,
1021 : opcintype,
1022 : exprCollation((Node *) expr),
1023 : (cmptype == COMPARE_GT),
1024 : (cmptype == COMPARE_GT),
1025 : 0,
1026 : rel,
1027 : create_it);
1028 :
1029 474 : if (cpathkey)
1030 279 : pathkeys = list_make1(cpathkey);
1031 : else
1032 195 : pathkeys = NIL;
1033 :
1034 474 : return pathkeys;
1035 : }
1036 :
1037 : /*
1038 : * convert_subquery_pathkeys
1039 : * Build a pathkeys list that describes the ordering of a subquery's
1040 : * result, in the terms of the outer query. This is essentially a
1041 : * task of conversion.
1042 : *
1043 : * 'rel': outer query's RelOptInfo for the subquery relation.
1044 : * 'subquery_pathkeys': the subquery's output pathkeys, in its terms.
1045 : * 'subquery_tlist': the subquery's output targetlist, in its terms.
1046 : *
1047 : * We intentionally don't do truncate_useless_pathkeys() here, because there
1048 : * are situations where seeing the raw ordering of the subquery is helpful.
1049 : * For example, if it returns ORDER BY x DESC, that may prompt us to
1050 : * construct a mergejoin using DESC order rather than ASC order; but the
1051 : * right_merge_direction heuristic would have us throw the knowledge away.
1052 : */
1053 : List *
1054 33823 : convert_subquery_pathkeys(PlannerInfo *root, RelOptInfo *rel,
1055 : List *subquery_pathkeys,
1056 : List *subquery_tlist)
1057 : {
1058 33823 : List *retval = NIL;
1059 33823 : int retvallen = 0;
1060 33823 : int outer_query_keys = list_length(root->query_pathkeys);
1061 : ListCell *i;
1062 :
1063 52810 : foreach(i, subquery_pathkeys)
1064 : {
1065 20992 : PathKey *sub_pathkey = (PathKey *) lfirst(i);
1066 20992 : EquivalenceClass *sub_eclass = sub_pathkey->pk_eclass;
1067 20992 : PathKey *best_pathkey = NULL;
1068 :
1069 20992 : if (sub_eclass->ec_has_volatile)
1070 : {
1071 : /*
1072 : * If the sub_pathkey's EquivalenceClass is volatile, then it must
1073 : * have come from an ORDER BY clause, and we have to match it to
1074 : * that same targetlist entry.
1075 : */
1076 : TargetEntry *tle;
1077 : Var *outer_var;
1078 :
1079 49 : if (sub_eclass->ec_sortref == 0) /* can't happen */
1080 0 : elog(ERROR, "volatile EquivalenceClass has no sortref");
1081 49 : tle = get_sortgroupref_tle(sub_eclass->ec_sortref, subquery_tlist);
1082 : Assert(tle);
1083 : /* Is TLE actually available to the outer query? */
1084 49 : outer_var = find_var_for_subquery_tle(rel, tle);
1085 49 : if (outer_var)
1086 : {
1087 : /* We can represent this sub_pathkey */
1088 : EquivalenceMember *sub_member;
1089 : EquivalenceClass *outer_ec;
1090 :
1091 : Assert(list_length(sub_eclass->ec_members) == 1);
1092 36 : sub_member = (EquivalenceMember *) linitial(sub_eclass->ec_members);
1093 :
1094 : /*
1095 : * Note: it might look funny to be setting sortref = 0 for a
1096 : * reference to a volatile sub_eclass. However, the
1097 : * expression is *not* volatile in the outer query: it's just
1098 : * a Var referencing whatever the subquery emitted. (IOW, the
1099 : * outer query isn't going to re-execute the volatile
1100 : * expression itself.) So this is okay.
1101 : */
1102 : outer_ec =
1103 36 : get_eclass_for_sort_expr(root,
1104 : (Expr *) outer_var,
1105 : sub_eclass->ec_opfamilies,
1106 : sub_member->em_datatype,
1107 : sub_eclass->ec_collation,
1108 : 0,
1109 : rel->relids,
1110 : false);
1111 :
1112 : /*
1113 : * If we don't find a matching EC, sub-pathkey isn't
1114 : * interesting to the outer query
1115 : */
1116 36 : if (outer_ec)
1117 : best_pathkey =
1118 6 : make_canonical_pathkey(root,
1119 : outer_ec,
1120 : sub_pathkey->pk_opfamily,
1121 : sub_pathkey->pk_cmptype,
1122 6 : sub_pathkey->pk_nulls_first);
1123 : }
1124 : }
1125 : else
1126 : {
1127 : /*
1128 : * Otherwise, the sub_pathkey's EquivalenceClass could contain
1129 : * multiple elements (representing knowledge that multiple items
1130 : * are effectively equal). Each element might match none, one, or
1131 : * more of the output columns that are visible to the outer query.
1132 : * This means we may have multiple possible representations of the
1133 : * sub_pathkey in the context of the outer query. Ideally we
1134 : * would generate them all and put them all into an EC of the
1135 : * outer query, thereby propagating equality knowledge up to the
1136 : * outer query. Right now we cannot do so, because the outer
1137 : * query's EquivalenceClasses are already frozen when this is
1138 : * called. Instead we prefer the one that has the highest "score"
1139 : * (number of EC peers, plus one if it matches the outer
1140 : * query_pathkeys). This is the most likely to be useful in the
1141 : * outer query.
1142 : */
1143 20943 : int best_score = -1;
1144 : ListCell *j;
1145 :
1146 : /* Ignore children here */
1147 41920 : foreach(j, sub_eclass->ec_members)
1148 : {
1149 20977 : EquivalenceMember *sub_member = (EquivalenceMember *) lfirst(j);
1150 20977 : Expr *sub_expr = sub_member->em_expr;
1151 20977 : Oid sub_expr_type = sub_member->em_datatype;
1152 20977 : Oid sub_expr_coll = sub_eclass->ec_collation;
1153 : ListCell *k;
1154 :
1155 : /* Child members should not exist in ec_members */
1156 : Assert(!sub_member->em_is_child);
1157 :
1158 118845 : foreach(k, subquery_tlist)
1159 : {
1160 97868 : TargetEntry *tle = (TargetEntry *) lfirst(k);
1161 : Var *outer_var;
1162 : Expr *tle_expr;
1163 : EquivalenceClass *outer_ec;
1164 : PathKey *outer_pk;
1165 : int score;
1166 :
1167 : /* Is TLE actually available to the outer query? */
1168 97868 : outer_var = find_var_for_subquery_tle(rel, tle);
1169 97868 : if (!outer_var)
1170 21231 : continue;
1171 :
1172 : /*
1173 : * The targetlist entry is considered to match if it
1174 : * matches after sort-key canonicalization. That is
1175 : * needed since the sub_expr has been through the same
1176 : * process.
1177 : */
1178 76637 : tle_expr = canonicalize_ec_expression(tle->expr,
1179 : sub_expr_type,
1180 : sub_expr_coll);
1181 76637 : if (!equal(tle_expr, sub_expr))
1182 56371 : continue;
1183 :
1184 : /* See if we have a matching EC for the TLE */
1185 20266 : outer_ec = get_eclass_for_sort_expr(root,
1186 : (Expr *) outer_var,
1187 : sub_eclass->ec_opfamilies,
1188 : sub_expr_type,
1189 : sub_expr_coll,
1190 : 0,
1191 : rel->relids,
1192 : false);
1193 :
1194 : /*
1195 : * If we don't find a matching EC, this sub-pathkey isn't
1196 : * interesting to the outer query
1197 : */
1198 20266 : if (!outer_ec)
1199 1277 : continue;
1200 :
1201 18989 : outer_pk = make_canonical_pathkey(root,
1202 : outer_ec,
1203 : sub_pathkey->pk_opfamily,
1204 : sub_pathkey->pk_cmptype,
1205 18989 : sub_pathkey->pk_nulls_first);
1206 : /* score = # of equivalence peers */
1207 18989 : score = list_length(outer_ec->ec_members) - 1;
1208 : /* +1 if it matches the proper query_pathkeys item */
1209 37825 : if (retvallen < outer_query_keys &&
1210 18836 : list_nth(root->query_pathkeys, retvallen) == outer_pk)
1211 17957 : score++;
1212 18989 : if (score > best_score)
1213 : {
1214 18981 : best_pathkey = outer_pk;
1215 18981 : best_score = score;
1216 : }
1217 : }
1218 : }
1219 : }
1220 :
1221 : /*
1222 : * If we couldn't find a representation of this sub_pathkey, we're
1223 : * done (we can't use the ones to its right, either).
1224 : */
1225 20992 : if (!best_pathkey)
1226 2005 : break;
1227 :
1228 : /*
1229 : * Eliminate redundant ordering info; could happen if outer query
1230 : * equivalences subquery keys...
1231 : */
1232 18987 : if (!pathkey_is_redundant(best_pathkey, retval))
1233 : {
1234 18975 : retval = lappend(retval, best_pathkey);
1235 18975 : retvallen++;
1236 : }
1237 : }
1238 :
1239 33823 : return retval;
1240 : }
1241 :
1242 : /*
1243 : * find_var_for_subquery_tle
1244 : *
1245 : * If the given subquery tlist entry is due to be emitted by the subquery's
1246 : * scan node, return a Var for it, else return NULL.
1247 : *
1248 : * We need this to ensure that we don't return pathkeys describing values
1249 : * that are unavailable above the level of the subquery scan.
1250 : */
1251 : static Var *
1252 97917 : find_var_for_subquery_tle(RelOptInfo *rel, TargetEntry *tle)
1253 : {
1254 : ListCell *lc;
1255 :
1256 : /* If the TLE is resjunk, it's certainly not visible to the outer query */
1257 97917 : if (tle->resjunk)
1258 50 : return NULL;
1259 :
1260 : /* Search the rel's targetlist to see what it will return */
1261 573606 : foreach(lc, rel->reltarget->exprs)
1262 : {
1263 552412 : Var *var = (Var *) lfirst(lc);
1264 :
1265 : /* Ignore placeholders */
1266 552412 : if (!IsA(var, Var))
1267 27454 : continue;
1268 : Assert(var->varno == rel->relid);
1269 :
1270 : /* If we find a Var referencing this TLE, we're good */
1271 524958 : if (var->varattno == tle->resno)
1272 76673 : return copyObject(var); /* Make a copy for safety */
1273 : }
1274 21194 : return NULL;
1275 : }
1276 :
1277 : /*
1278 : * build_join_pathkeys
1279 : * Build the path keys for a join relation constructed by mergejoin or
1280 : * nestloop join. This is normally the same as the outer path's keys.
1281 : *
1282 : * EXCEPTION: in a FULL, RIGHT or RIGHT_ANTI join, we cannot treat the
1283 : * result as having the outer path's path keys, because null lefthand rows
1284 : * may be inserted at random points. It must be treated as unsorted.
1285 : *
1286 : * We truncate away any pathkeys that are uninteresting for higher joins.
1287 : *
1288 : * 'joinrel' is the join relation that paths are being formed for
1289 : * 'jointype' is the join type (inner, left, full, etc)
1290 : * 'outer_pathkeys' is the list of the current outer path's path keys
1291 : *
1292 : * Returns the list of new path keys.
1293 : */
1294 : List *
1295 1181399 : build_join_pathkeys(PlannerInfo *root,
1296 : RelOptInfo *joinrel,
1297 : JoinType jointype,
1298 : List *outer_pathkeys)
1299 : {
1300 : /* RIGHT_SEMI should not come here */
1301 : Assert(jointype != JOIN_RIGHT_SEMI);
1302 :
1303 1181399 : if (jointype == JOIN_FULL ||
1304 1042683 : jointype == JOIN_RIGHT ||
1305 : jointype == JOIN_RIGHT_ANTI)
1306 147085 : return NIL;
1307 :
1308 : /*
1309 : * This used to be quite a complex bit of code, but now that all pathkey
1310 : * sublists start out life canonicalized, we don't have to do a darn thing
1311 : * here!
1312 : *
1313 : * We do, however, need to truncate the pathkeys list, since it may
1314 : * contain pathkeys that were useful for forming this joinrel but are
1315 : * uninteresting to higher levels.
1316 : */
1317 1034314 : return truncate_useless_pathkeys(root, joinrel, outer_pathkeys);
1318 : }
1319 :
1320 : /****************************************************************************
1321 : * PATHKEYS AND SORT CLAUSES
1322 : ****************************************************************************/
1323 :
1324 : /*
1325 : * make_pathkeys_for_sortclauses
1326 : * Generate a pathkeys list that represents the sort order specified
1327 : * by a list of SortGroupClauses
1328 : *
1329 : * The resulting PathKeys are always in canonical form. (Actually, there
1330 : * is no longer any code anywhere that creates non-canonical PathKeys.)
1331 : *
1332 : * 'sortclauses' is a list of SortGroupClause nodes
1333 : * 'tlist' is the targetlist to find the referenced tlist entries in
1334 : */
1335 : List *
1336 286710 : make_pathkeys_for_sortclauses(PlannerInfo *root,
1337 : List *sortclauses,
1338 : List *tlist)
1339 : {
1340 : List *result;
1341 : bool sortable;
1342 :
1343 286710 : result = make_pathkeys_for_sortclauses_extended(root,
1344 : &sortclauses,
1345 : tlist,
1346 : false,
1347 : false,
1348 : &sortable,
1349 : false);
1350 : /* It's caller error if not all clauses were sortable */
1351 : Assert(sortable);
1352 286710 : return result;
1353 : }
1354 :
1355 : /*
1356 : * make_pathkeys_for_sortclauses_extended
1357 : * Generate a pathkeys list that represents the sort order specified
1358 : * by a list of SortGroupClauses
1359 : *
1360 : * The comments for make_pathkeys_for_sortclauses apply here too. In addition:
1361 : *
1362 : * If remove_redundant is true, then any sort clauses that are found to
1363 : * give rise to redundant pathkeys are removed from the sortclauses list
1364 : * (which therefore must be pass-by-reference in this version).
1365 : *
1366 : * If remove_group_rtindex is true, then we need to remove the RT index of the
1367 : * grouping step from the sort expressions before we make PathKeys for them.
1368 : *
1369 : * *sortable is set to true if all the sort clauses are in fact sortable.
1370 : * If any are not, they are ignored except for setting *sortable false.
1371 : * (In that case, the output pathkey list isn't really useful. However,
1372 : * we process the whole sortclauses list anyway, because it's still valid
1373 : * to remove any clauses that can be proven redundant via the eclass logic.
1374 : * Even though we'll have to hash in that case, we might as well not hash
1375 : * redundant columns.)
1376 : *
1377 : * If set_ec_sortref is true then sets the value of the pathkey's
1378 : * EquivalenceClass unless it's already initialized.
1379 : */
1380 : List *
1381 298940 : make_pathkeys_for_sortclauses_extended(PlannerInfo *root,
1382 : List **sortclauses,
1383 : List *tlist,
1384 : bool remove_redundant,
1385 : bool remove_group_rtindex,
1386 : bool *sortable,
1387 : bool set_ec_sortref)
1388 : {
1389 298940 : List *pathkeys = NIL;
1390 : ListCell *l;
1391 :
1392 298940 : *sortable = true;
1393 399238 : foreach(l, *sortclauses)
1394 : {
1395 100298 : SortGroupClause *sortcl = (SortGroupClause *) lfirst(l);
1396 : Expr *sortkey;
1397 : PathKey *pathkey;
1398 :
1399 100298 : sortkey = (Expr *) get_sortgroupclause_expr(sortcl, tlist);
1400 100298 : if (!OidIsValid(sortcl->sortop))
1401 : {
1402 107 : *sortable = false;
1403 107 : continue;
1404 : }
1405 100191 : if (remove_group_rtindex)
1406 : {
1407 : Assert(root->group_rtindex > 0);
1408 : sortkey = (Expr *)
1409 771 : remove_nulling_relids((Node *) sortkey,
1410 771 : bms_make_singleton(root->group_rtindex),
1411 : NULL);
1412 : }
1413 100191 : pathkey = make_pathkey_from_sortop(root,
1414 : sortkey,
1415 : sortcl->sortop,
1416 100191 : sortcl->reverse_sort,
1417 100191 : sortcl->nulls_first,
1418 : sortcl->tleSortGroupRef,
1419 : true);
1420 100191 : if (pathkey->pk_eclass->ec_sortref == 0 && set_ec_sortref)
1421 : {
1422 : /*
1423 : * Copy the sortref if it hasn't been set yet. That may happen if
1424 : * the EquivalenceClass was constructed from a WHERE clause, i.e.
1425 : * it doesn't have a target reference at all.
1426 : */
1427 374 : pathkey->pk_eclass->ec_sortref = sortcl->tleSortGroupRef;
1428 : }
1429 :
1430 : /* Canonical form eliminates redundant ordering keys */
1431 100191 : if (!pathkey_is_redundant(pathkey, pathkeys))
1432 90871 : pathkeys = lappend(pathkeys, pathkey);
1433 9320 : else if (remove_redundant)
1434 678 : *sortclauses = foreach_delete_current(*sortclauses, l);
1435 : }
1436 298940 : return pathkeys;
1437 : }
1438 :
1439 : /****************************************************************************
1440 : * PATHKEYS AND MERGECLAUSES
1441 : ****************************************************************************/
1442 :
1443 : /*
1444 : * initialize_mergeclause_eclasses
1445 : * Set the EquivalenceClass links in a mergeclause restrictinfo.
1446 : *
1447 : * RestrictInfo contains fields in which we may cache pointers to
1448 : * EquivalenceClasses for the left and right inputs of the mergeclause.
1449 : * (If the mergeclause is a true equivalence clause these will be the
1450 : * same EquivalenceClass, otherwise not.) If the mergeclause is either
1451 : * used to generate an EquivalenceClass, or derived from an EquivalenceClass,
1452 : * then it's easy to set up the left_ec and right_ec members --- otherwise,
1453 : * this function should be called to set them up. We will generate new
1454 : * EquivalenceClauses if necessary to represent the mergeclause's left and
1455 : * right sides.
1456 : *
1457 : * Note this is called before EC merging is complete, so the links won't
1458 : * necessarily point to canonical ECs. Before they are actually used for
1459 : * anything, update_mergeclause_eclasses must be called to ensure that
1460 : * they've been updated to point to canonical ECs.
1461 : */
1462 : void
1463 29575 : initialize_mergeclause_eclasses(PlannerInfo *root, RestrictInfo *restrictinfo)
1464 : {
1465 29575 : Expr *clause = restrictinfo->clause;
1466 : Oid lefttype,
1467 : righttype;
1468 :
1469 : /* Should be a mergeclause ... */
1470 : Assert(restrictinfo->mergeopfamilies != NIL);
1471 : /* ... with links not yet set */
1472 : Assert(restrictinfo->left_ec == NULL);
1473 : Assert(restrictinfo->right_ec == NULL);
1474 :
1475 : /* Need the declared input types of the operator */
1476 29575 : op_input_types(((OpExpr *) clause)->opno, &lefttype, &righttype);
1477 :
1478 : /* Find or create a matching EquivalenceClass for each side */
1479 29575 : restrictinfo->left_ec =
1480 29575 : get_eclass_for_sort_expr(root,
1481 29575 : (Expr *) get_leftop(clause),
1482 : restrictinfo->mergeopfamilies,
1483 : lefttype,
1484 : ((OpExpr *) clause)->inputcollid,
1485 : 0,
1486 : NULL,
1487 : true);
1488 29575 : restrictinfo->right_ec =
1489 29575 : get_eclass_for_sort_expr(root,
1490 29575 : (Expr *) get_rightop(clause),
1491 : restrictinfo->mergeopfamilies,
1492 : righttype,
1493 : ((OpExpr *) clause)->inputcollid,
1494 : 0,
1495 : NULL,
1496 : true);
1497 29575 : }
1498 :
1499 : /*
1500 : * update_mergeclause_eclasses
1501 : * Make the cached EquivalenceClass links valid in a mergeclause
1502 : * restrictinfo.
1503 : *
1504 : * These pointers should have been set by process_equivalence or
1505 : * initialize_mergeclause_eclasses, but they might have been set to
1506 : * non-canonical ECs that got merged later. Chase up to the canonical
1507 : * merged parent if so.
1508 : */
1509 : void
1510 2883792 : update_mergeclause_eclasses(PlannerInfo *root, RestrictInfo *restrictinfo)
1511 : {
1512 : /* Should be a merge clause ... */
1513 : Assert(restrictinfo->mergeopfamilies != NIL);
1514 : /* ... with pointers already set */
1515 : Assert(restrictinfo->left_ec != NULL);
1516 : Assert(restrictinfo->right_ec != NULL);
1517 :
1518 : /* Chase up to the top as needed */
1519 2883792 : while (restrictinfo->left_ec->ec_merged)
1520 0 : restrictinfo->left_ec = restrictinfo->left_ec->ec_merged;
1521 2883792 : while (restrictinfo->right_ec->ec_merged)
1522 0 : restrictinfo->right_ec = restrictinfo->right_ec->ec_merged;
1523 2883792 : }
1524 :
1525 : /*
1526 : * find_mergeclauses_for_outer_pathkeys
1527 : * This routine attempts to find a list of mergeclauses that can be
1528 : * used with a specified ordering for the join's outer relation.
1529 : * If successful, it returns a list of mergeclauses.
1530 : *
1531 : * 'pathkeys' is a pathkeys list showing the ordering of an outer-rel path.
1532 : * 'restrictinfos' is a list of mergejoinable restriction clauses for the
1533 : * join relation being formed, in no particular order.
1534 : *
1535 : * The restrictinfos must be marked (via outer_is_left) to show which side
1536 : * of each clause is associated with the current outer path. (See
1537 : * select_mergejoin_clauses())
1538 : *
1539 : * The result is NIL if no merge can be done, else a maximal list of
1540 : * usable mergeclauses (represented as a list of their restrictinfo nodes).
1541 : * The list is ordered to match the pathkeys, as required for execution.
1542 : */
1543 : List *
1544 1125116 : find_mergeclauses_for_outer_pathkeys(PlannerInfo *root,
1545 : List *pathkeys,
1546 : List *restrictinfos)
1547 : {
1548 1125116 : List *mergeclauses = NIL;
1549 : ListCell *i;
1550 :
1551 : /* make sure we have eclasses cached in the clauses */
1552 2363471 : foreach(i, restrictinfos)
1553 : {
1554 1238355 : RestrictInfo *rinfo = (RestrictInfo *) lfirst(i);
1555 :
1556 1238355 : update_mergeclause_eclasses(root, rinfo);
1557 : }
1558 :
1559 1832683 : foreach(i, pathkeys)
1560 : {
1561 841586 : PathKey *pathkey = (PathKey *) lfirst(i);
1562 841586 : EquivalenceClass *pathkey_ec = pathkey->pk_eclass;
1563 841586 : List *matched_restrictinfos = NIL;
1564 : ListCell *j;
1565 :
1566 : /*----------
1567 : * A mergejoin clause matches a pathkey if it has the same EC.
1568 : * If there are multiple matching clauses, take them all. In plain
1569 : * inner-join scenarios we expect only one match, because
1570 : * equivalence-class processing will have removed any redundant
1571 : * mergeclauses. However, in outer-join scenarios there might be
1572 : * multiple matches. An example is
1573 : *
1574 : * select * from a full join b
1575 : * on a.v1 = b.v1 and a.v2 = b.v2 and a.v1 = b.v2;
1576 : *
1577 : * Given the pathkeys ({a.v1}, {a.v2}) it is okay to return all three
1578 : * clauses (in the order a.v1=b.v1, a.v1=b.v2, a.v2=b.v2) and indeed
1579 : * we *must* do so or we will be unable to form a valid plan.
1580 : *
1581 : * We expect that the given pathkeys list is canonical, which means
1582 : * no two members have the same EC, so it's not possible for this
1583 : * code to enter the same mergeclause into the result list twice.
1584 : *
1585 : * It's possible that multiple matching clauses might have different
1586 : * ECs on the other side, in which case the order we put them into our
1587 : * result makes a difference in the pathkeys required for the inner
1588 : * input rel. However this routine hasn't got any info about which
1589 : * order would be best, so we don't worry about that.
1590 : *
1591 : * It's also possible that the selected mergejoin clauses produce
1592 : * a noncanonical ordering of pathkeys for the inner side, ie, we
1593 : * might select clauses that reference b.v1, b.v2, b.v1 in that
1594 : * order. This is not harmful in itself, though it suggests that
1595 : * the clauses are partially redundant. Since the alternative is
1596 : * to omit mergejoin clauses and thereby possibly fail to generate a
1597 : * plan altogether, we live with it. make_inner_pathkeys_for_merge()
1598 : * has to delete duplicates when it constructs the inner pathkeys
1599 : * list, and we also have to deal with such cases specially in
1600 : * create_mergejoin_plan().
1601 : *----------
1602 : */
1603 1922005 : foreach(j, restrictinfos)
1604 : {
1605 1080419 : RestrictInfo *rinfo = (RestrictInfo *) lfirst(j);
1606 : EquivalenceClass *clause_ec;
1607 :
1608 2160838 : clause_ec = rinfo->outer_is_left ?
1609 1080419 : rinfo->left_ec : rinfo->right_ec;
1610 1080419 : if (clause_ec == pathkey_ec)
1611 707624 : matched_restrictinfos = lappend(matched_restrictinfos, rinfo);
1612 : }
1613 :
1614 : /*
1615 : * If we didn't find a mergeclause, we're done --- any additional
1616 : * sort-key positions in the pathkeys are useless. (But we can still
1617 : * mergejoin if we found at least one mergeclause.)
1618 : */
1619 841586 : if (matched_restrictinfos == NIL)
1620 134019 : break;
1621 :
1622 : /*
1623 : * If we did find usable mergeclause(s) for this sort-key position,
1624 : * add them to result list.
1625 : */
1626 707567 : mergeclauses = list_concat(mergeclauses, matched_restrictinfos);
1627 : }
1628 :
1629 1125116 : return mergeclauses;
1630 : }
1631 :
1632 : /*
1633 : * select_outer_pathkeys_for_merge
1634 : * Builds a pathkey list representing a possible sort ordering
1635 : * that can be used with the given mergeclauses.
1636 : *
1637 : * 'mergeclauses' is a list of RestrictInfos for mergejoin clauses
1638 : * that will be used in a merge join.
1639 : * 'joinrel' is the join relation we are trying to construct.
1640 : *
1641 : * The restrictinfos must be marked (via outer_is_left) to show which side
1642 : * of each clause is associated with the current outer path. (See
1643 : * select_mergejoin_clauses())
1644 : *
1645 : * Returns a pathkeys list that can be applied to the outer relation.
1646 : *
1647 : * Since we assume here that a sort is required, there is no particular use
1648 : * in matching any available ordering of the outerrel. (joinpath.c has an
1649 : * entirely separate code path for considering sort-free mergejoins.) Rather,
1650 : * it's interesting to try to match, or match a prefix of the requested
1651 : * query_pathkeys so that a second output sort may be avoided or an
1652 : * incremental sort may be done instead. We can get away with just a prefix
1653 : * of the query_pathkeys when that prefix covers the entire join condition.
1654 : * Failing that, we try to list "more popular" keys (those with the most
1655 : * unmatched EquivalenceClass peers) earlier, in hopes of making the resulting
1656 : * ordering useful for as many higher-level mergejoins as possible.
1657 : */
1658 : List *
1659 319890 : select_outer_pathkeys_for_merge(PlannerInfo *root,
1660 : List *mergeclauses,
1661 : RelOptInfo *joinrel)
1662 : {
1663 319890 : List *pathkeys = NIL;
1664 319890 : int nClauses = list_length(mergeclauses);
1665 : EquivalenceClass **ecs;
1666 : int *scores;
1667 : int necs;
1668 : ListCell *lc;
1669 : int j;
1670 :
1671 : /* Might have no mergeclauses */
1672 319890 : if (nClauses == 0)
1673 0 : return NIL;
1674 :
1675 : /*
1676 : * Make arrays of the ECs used by the mergeclauses (dropping any
1677 : * duplicates) and their "popularity" scores.
1678 : */
1679 319890 : ecs = (EquivalenceClass **) palloc(nClauses * sizeof(EquivalenceClass *));
1680 319890 : scores = (int *) palloc(nClauses * sizeof(int));
1681 319890 : necs = 0;
1682 :
1683 679140 : foreach(lc, mergeclauses)
1684 : {
1685 359250 : RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
1686 : EquivalenceClass *oeclass;
1687 : int score;
1688 : ListCell *lc2;
1689 :
1690 : /* get the outer eclass */
1691 359250 : update_mergeclause_eclasses(root, rinfo);
1692 :
1693 359250 : if (rinfo->outer_is_left)
1694 181414 : oeclass = rinfo->left_ec;
1695 : else
1696 177836 : oeclass = rinfo->right_ec;
1697 :
1698 : /* reject duplicates */
1699 400751 : for (j = 0; j < necs; j++)
1700 : {
1701 41534 : if (ecs[j] == oeclass)
1702 33 : break;
1703 : }
1704 359250 : if (j < necs)
1705 33 : continue;
1706 :
1707 : /* compute score */
1708 359217 : score = 0;
1709 1032550 : foreach(lc2, oeclass->ec_members)
1710 : {
1711 673333 : EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2);
1712 :
1713 : /* Child members should not exist in ec_members */
1714 : Assert(!em->em_is_child);
1715 :
1716 : /* Potential future join partner? */
1717 673333 : if (!em->em_is_const &&
1718 673333 : !bms_overlap(em->em_relids, joinrel->relids))
1719 95840 : score++;
1720 : }
1721 :
1722 359217 : ecs[necs] = oeclass;
1723 359217 : scores[necs] = score;
1724 359217 : necs++;
1725 : }
1726 :
1727 : /*
1728 : * Find out if we have all the ECs mentioned in query_pathkeys; if so we
1729 : * can generate a sort order that's also useful for final output. If we
1730 : * only have a prefix of the query_pathkeys, and that prefix is the entire
1731 : * join condition, then it's useful to use the prefix as the pathkeys as
1732 : * this increases the chances that an incremental sort will be able to be
1733 : * used by the upper planner.
1734 : */
1735 319890 : if (root->query_pathkeys)
1736 : {
1737 212322 : int matches = 0;
1738 :
1739 276360 : foreach(lc, root->query_pathkeys)
1740 : {
1741 237783 : PathKey *query_pathkey = (PathKey *) lfirst(lc);
1742 237783 : EquivalenceClass *query_ec = query_pathkey->pk_eclass;
1743 :
1744 432881 : for (j = 0; j < necs; j++)
1745 : {
1746 259136 : if (ecs[j] == query_ec)
1747 64038 : break; /* found match */
1748 : }
1749 237783 : if (j >= necs)
1750 173745 : break; /* didn't find match */
1751 :
1752 64038 : matches++;
1753 : }
1754 : /* if we got to the end of the list, we have them all */
1755 212322 : if (lc == NULL)
1756 : {
1757 : /* copy query_pathkeys as starting point for our output */
1758 38577 : pathkeys = list_copy(root->query_pathkeys);
1759 : /* mark their ECs as already-emitted */
1760 77544 : foreach(lc, root->query_pathkeys)
1761 : {
1762 38967 : PathKey *query_pathkey = (PathKey *) lfirst(lc);
1763 38967 : EquivalenceClass *query_ec = query_pathkey->pk_eclass;
1764 :
1765 39420 : for (j = 0; j < necs; j++)
1766 : {
1767 39420 : if (ecs[j] == query_ec)
1768 : {
1769 38967 : scores[j] = -1;
1770 38967 : break;
1771 : }
1772 : }
1773 : }
1774 : }
1775 :
1776 : /*
1777 : * If we didn't match to all of the query_pathkeys, but did match to
1778 : * all of the join clauses then we'll make use of these as partially
1779 : * sorted input is better than nothing for the upper planner as it may
1780 : * lead to incremental sorts instead of full sorts.
1781 : */
1782 173745 : else if (matches == nClauses)
1783 : {
1784 20186 : pathkeys = list_copy_head(root->query_pathkeys, matches);
1785 :
1786 : /* we have all of the join pathkeys, so nothing more to do */
1787 20186 : pfree(ecs);
1788 20186 : pfree(scores);
1789 :
1790 20186 : return pathkeys;
1791 : }
1792 : }
1793 :
1794 : /*
1795 : * Add remaining ECs to the list in popularity order, using a default sort
1796 : * ordering. (We could use qsort() here, but the list length is usually
1797 : * so small it's not worth it.)
1798 : */
1799 : for (;;)
1800 300058 : {
1801 : int best_j;
1802 : int best_score;
1803 : EquivalenceClass *ec;
1804 : PathKey *pathkey;
1805 :
1806 599762 : best_j = 0;
1807 599762 : best_score = scores[0];
1808 719862 : for (j = 1; j < necs; j++)
1809 : {
1810 120100 : if (scores[j] > best_score)
1811 : {
1812 38877 : best_j = j;
1813 38877 : best_score = scores[j];
1814 : }
1815 : }
1816 599762 : if (best_score < 0)
1817 299704 : break; /* all done */
1818 300058 : ec = ecs[best_j];
1819 300058 : scores[best_j] = -1;
1820 300058 : pathkey = make_canonical_pathkey(root,
1821 : ec,
1822 300058 : linitial_oid(ec->ec_opfamilies),
1823 : COMPARE_LT,
1824 : false);
1825 : /* can't be redundant because no duplicate ECs */
1826 : Assert(!pathkey_is_redundant(pathkey, pathkeys));
1827 300058 : pathkeys = lappend(pathkeys, pathkey);
1828 : }
1829 :
1830 299704 : pfree(ecs);
1831 299704 : pfree(scores);
1832 :
1833 299704 : return pathkeys;
1834 : }
1835 :
1836 : /*
1837 : * make_inner_pathkeys_for_merge
1838 : * Builds a pathkey list representing the explicit sort order that
1839 : * must be applied to an inner path to make it usable with the
1840 : * given mergeclauses.
1841 : *
1842 : * 'mergeclauses' is a list of RestrictInfos for the mergejoin clauses
1843 : * that will be used in a merge join, in order.
1844 : * 'outer_pathkeys' are the already-known canonical pathkeys for the outer
1845 : * side of the join.
1846 : *
1847 : * The restrictinfos must be marked (via outer_is_left) to show which side
1848 : * of each clause is associated with the current outer path. (See
1849 : * select_mergejoin_clauses())
1850 : *
1851 : * Returns a pathkeys list that can be applied to the inner relation.
1852 : *
1853 : * Note that it is not this routine's job to decide whether sorting is
1854 : * actually needed for a particular input path. Assume a sort is necessary;
1855 : * just make the keys, eh?
1856 : */
1857 : List *
1858 604403 : make_inner_pathkeys_for_merge(PlannerInfo *root,
1859 : List *mergeclauses,
1860 : List *outer_pathkeys)
1861 : {
1862 604403 : List *pathkeys = NIL;
1863 : EquivalenceClass *lastoeclass;
1864 : PathKey *opathkey;
1865 : ListCell *lc;
1866 : ListCell *lop;
1867 :
1868 604403 : lastoeclass = NULL;
1869 604403 : opathkey = NULL;
1870 604403 : lop = list_head(outer_pathkeys);
1871 :
1872 1306771 : foreach(lc, mergeclauses)
1873 : {
1874 702368 : RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
1875 : EquivalenceClass *oeclass;
1876 : EquivalenceClass *ieclass;
1877 : PathKey *pathkey;
1878 :
1879 702368 : update_mergeclause_eclasses(root, rinfo);
1880 :
1881 702368 : if (rinfo->outer_is_left)
1882 : {
1883 366291 : oeclass = rinfo->left_ec;
1884 366291 : ieclass = rinfo->right_ec;
1885 : }
1886 : else
1887 : {
1888 336077 : oeclass = rinfo->right_ec;
1889 336077 : ieclass = rinfo->left_ec;
1890 : }
1891 :
1892 : /* outer eclass should match current or next pathkeys */
1893 : /* we check this carefully for debugging reasons */
1894 702368 : if (oeclass != lastoeclass)
1895 : {
1896 702317 : if (!lop)
1897 0 : elog(ERROR, "too few pathkeys for mergeclauses");
1898 702317 : opathkey = (PathKey *) lfirst(lop);
1899 702317 : lop = lnext(outer_pathkeys, lop);
1900 702317 : lastoeclass = opathkey->pk_eclass;
1901 702317 : if (oeclass != lastoeclass)
1902 0 : elog(ERROR, "outer pathkeys do not match mergeclause");
1903 : }
1904 :
1905 : /*
1906 : * Often, we'll have same EC on both sides, in which case the outer
1907 : * pathkey is also canonical for the inner side, and we can skip a
1908 : * useless search.
1909 : */
1910 702368 : if (ieclass == oeclass)
1911 494485 : pathkey = opathkey;
1912 : else
1913 207883 : pathkey = make_canonical_pathkey(root,
1914 : ieclass,
1915 : opathkey->pk_opfamily,
1916 : opathkey->pk_cmptype,
1917 207883 : opathkey->pk_nulls_first);
1918 :
1919 : /*
1920 : * Don't generate redundant pathkeys (which can happen if multiple
1921 : * mergeclauses refer to the same EC). Because we do this, the output
1922 : * pathkey list isn't necessarily ordered like the mergeclauses, which
1923 : * complicates life for create_mergejoin_plan(). But if we didn't,
1924 : * we'd have a noncanonical sort key list, which would be bad; for one
1925 : * reason, it certainly wouldn't match any available sort order for
1926 : * the input relation.
1927 : */
1928 702368 : if (!pathkey_is_redundant(pathkey, pathkeys))
1929 702287 : pathkeys = lappend(pathkeys, pathkey);
1930 : }
1931 :
1932 604403 : return pathkeys;
1933 : }
1934 :
1935 : /*
1936 : * trim_mergeclauses_for_inner_pathkeys
1937 : * This routine trims a list of mergeclauses to include just those that
1938 : * work with a specified ordering for the join's inner relation.
1939 : *
1940 : * 'mergeclauses' is a list of RestrictInfos for mergejoin clauses for the
1941 : * join relation being formed, in an order known to work for the
1942 : * currently-considered sort ordering of the join's outer rel.
1943 : * 'pathkeys' is a pathkeys list showing the ordering of an inner-rel path;
1944 : * it should be equal to, or a truncation of, the result of
1945 : * make_inner_pathkeys_for_merge for these mergeclauses.
1946 : *
1947 : * What we return will be a prefix of the given mergeclauses list.
1948 : *
1949 : * We need this logic because make_inner_pathkeys_for_merge's result isn't
1950 : * necessarily in the same order as the mergeclauses. That means that if we
1951 : * consider an inner-rel pathkey list that is a truncation of that result,
1952 : * we might need to drop mergeclauses even though they match a surviving inner
1953 : * pathkey. This happens when they are to the right of a mergeclause that
1954 : * matches a removed inner pathkey.
1955 : *
1956 : * The mergeclauses must be marked (via outer_is_left) to show which side
1957 : * of each clause is associated with the current outer path. (See
1958 : * select_mergejoin_clauses())
1959 : */
1960 : List *
1961 7707 : trim_mergeclauses_for_inner_pathkeys(PlannerInfo *root,
1962 : List *mergeclauses,
1963 : List *pathkeys)
1964 : {
1965 7707 : List *new_mergeclauses = NIL;
1966 : PathKey *pathkey;
1967 : EquivalenceClass *pathkey_ec;
1968 : bool matched_pathkey;
1969 : ListCell *lip;
1970 : ListCell *i;
1971 :
1972 : /* No pathkeys => no mergeclauses (though we don't expect this case) */
1973 7707 : if (pathkeys == NIL)
1974 0 : return NIL;
1975 : /* Initialize to consider first pathkey */
1976 7707 : lip = list_head(pathkeys);
1977 7707 : pathkey = (PathKey *) lfirst(lip);
1978 7707 : pathkey_ec = pathkey->pk_eclass;
1979 7707 : lip = lnext(pathkeys, lip);
1980 7707 : matched_pathkey = false;
1981 :
1982 : /* Scan mergeclauses to see how many we can use */
1983 15414 : foreach(i, mergeclauses)
1984 : {
1985 15414 : RestrictInfo *rinfo = (RestrictInfo *) lfirst(i);
1986 : EquivalenceClass *clause_ec;
1987 :
1988 : /* Assume we needn't do update_mergeclause_eclasses again here */
1989 :
1990 : /* Check clause's inner-rel EC against current pathkey */
1991 30828 : clause_ec = rinfo->outer_is_left ?
1992 15414 : rinfo->right_ec : rinfo->left_ec;
1993 :
1994 : /* If we don't have a match, attempt to advance to next pathkey */
1995 15414 : if (clause_ec != pathkey_ec)
1996 : {
1997 : /* If we had no clauses matching this inner pathkey, must stop */
1998 7707 : if (!matched_pathkey)
1999 0 : break;
2000 :
2001 : /* Advance to next inner pathkey, if any */
2002 7707 : if (lip == NULL)
2003 7707 : break;
2004 0 : pathkey = (PathKey *) lfirst(lip);
2005 0 : pathkey_ec = pathkey->pk_eclass;
2006 0 : lip = lnext(pathkeys, lip);
2007 0 : matched_pathkey = false;
2008 : }
2009 :
2010 : /* If mergeclause matches current inner pathkey, we can use it */
2011 7707 : if (clause_ec == pathkey_ec)
2012 : {
2013 7707 : new_mergeclauses = lappend(new_mergeclauses, rinfo);
2014 7707 : matched_pathkey = true;
2015 : }
2016 : else
2017 : {
2018 : /* Else, no hope of adding any more mergeclauses */
2019 0 : break;
2020 : }
2021 : }
2022 :
2023 7707 : return new_mergeclauses;
2024 : }
2025 :
2026 :
2027 : /****************************************************************************
2028 : * PATHKEY USEFULNESS CHECKS
2029 : *
2030 : * We only want to remember as many of the pathkeys of a path as have some
2031 : * potential use, either for subsequent mergejoins or for meeting the query's
2032 : * requested output ordering. This ensures that add_path() won't consider
2033 : * a path to have a usefully different ordering unless it really is useful.
2034 : * These routines check for usefulness of given pathkeys.
2035 : ****************************************************************************/
2036 :
2037 : /*
2038 : * pathkeys_useful_for_merging
2039 : * Count the number of pathkeys that may be useful for mergejoins
2040 : * above the given relation.
2041 : *
2042 : * We consider a pathkey potentially useful if it corresponds to the merge
2043 : * ordering of either side of any joinclause for the rel. This might be
2044 : * overoptimistic, since joinclauses that require different other relations
2045 : * might never be usable at the same time, but trying to be exact is likely
2046 : * to be more trouble than it's worth.
2047 : *
2048 : * To avoid doubling the number of mergejoin paths considered, we would like
2049 : * to consider only one of the two scan directions (ASC or DESC) as useful
2050 : * for merging for any given target column. The choice is arbitrary unless
2051 : * one of the directions happens to match an ORDER BY key, in which case
2052 : * that direction should be preferred, in hopes of avoiding a final sort step.
2053 : * right_merge_direction() implements this heuristic.
2054 : */
2055 : static int
2056 805241 : pathkeys_useful_for_merging(PlannerInfo *root, RelOptInfo *rel, List *pathkeys)
2057 : {
2058 805241 : int useful = 0;
2059 : ListCell *i;
2060 :
2061 1115930 : foreach(i, pathkeys)
2062 : {
2063 854683 : PathKey *pathkey = (PathKey *) lfirst(i);
2064 854683 : bool matched = false;
2065 : ListCell *j;
2066 :
2067 : /* If "wrong" direction, not useful for merging */
2068 854683 : if (!right_merge_direction(root, pathkey))
2069 178399 : break;
2070 :
2071 : /*
2072 : * First look into the EquivalenceClass of the pathkey, to see if
2073 : * there are any members not yet joined to the rel. If so, it's
2074 : * surely possible to generate a mergejoin clause using them.
2075 : */
2076 1068246 : if (rel->has_eclass_joins &&
2077 391962 : eclass_useful_for_merging(root, pathkey->pk_eclass, rel))
2078 227480 : matched = true;
2079 : else
2080 : {
2081 : /*
2082 : * Otherwise search the rel's joininfo list, which contains
2083 : * non-EquivalenceClass-derivable join clauses that might
2084 : * nonetheless be mergejoinable.
2085 : */
2086 656833 : foreach(j, rel->joininfo)
2087 : {
2088 291238 : RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(j);
2089 :
2090 291238 : if (restrictinfo->mergeopfamilies == NIL)
2091 72017 : continue;
2092 219221 : update_mergeclause_eclasses(root, restrictinfo);
2093 :
2094 219221 : if (pathkey->pk_eclass == restrictinfo->left_ec ||
2095 179215 : pathkey->pk_eclass == restrictinfo->right_ec)
2096 : {
2097 83209 : matched = true;
2098 83209 : break;
2099 : }
2100 : }
2101 : }
2102 :
2103 : /*
2104 : * If we didn't find a mergeclause, we're done --- any additional
2105 : * sort-key positions in the pathkeys are useless. (But we can still
2106 : * mergejoin if we found at least one mergeclause.)
2107 : */
2108 676284 : if (matched)
2109 310689 : useful++;
2110 : else
2111 365595 : break;
2112 : }
2113 :
2114 805241 : return useful;
2115 : }
2116 :
2117 : /*
2118 : * right_merge_direction
2119 : * Check whether the pathkey embodies the preferred sort direction
2120 : * for merging its target column.
2121 : */
2122 : static bool
2123 854683 : right_merge_direction(PlannerInfo *root, PathKey *pathkey)
2124 : {
2125 : ListCell *l;
2126 :
2127 1653304 : foreach(l, root->query_pathkeys)
2128 : {
2129 865678 : PathKey *query_pathkey = (PathKey *) lfirst(l);
2130 :
2131 865678 : if (pathkey->pk_eclass == query_pathkey->pk_eclass &&
2132 67057 : pathkey->pk_opfamily == query_pathkey->pk_opfamily)
2133 : {
2134 : /*
2135 : * Found a matching query sort column. Prefer this pathkey's
2136 : * direction iff it matches. Note that we ignore pk_nulls_first,
2137 : * which means that a sort might be needed anyway ... but we still
2138 : * want to prefer only one of the two possible directions, and we
2139 : * might as well use this one.
2140 : */
2141 67057 : return (pathkey->pk_cmptype == query_pathkey->pk_cmptype);
2142 : }
2143 : }
2144 :
2145 : /* If no matching ORDER BY request, prefer the ASC direction */
2146 787626 : return (pathkey->pk_cmptype == COMPARE_LT);
2147 : }
2148 :
2149 : /*
2150 : * count_common_leading_pathkeys_ordered
2151 : * Returns the number of leading pathkeys which both lists have in common
2152 : */
2153 : static int
2154 3374110 : count_common_leading_pathkeys_ordered(List *keys1, List *keys2)
2155 : {
2156 : int ncommon;
2157 :
2158 3374110 : (void) pathkeys_count_contained_in(keys1, keys2, &ncommon);
2159 :
2160 3374110 : return ncommon;
2161 : }
2162 :
2163 : /*
2164 : * count_common_leading_pathkeys_unordered
2165 : * Returns the number of leading PathKeys in 'keys2' which exist in
2166 : * 'keys1'.
2167 : */
2168 : static int
2169 1623170 : count_common_leading_pathkeys_unordered(List *keys1, List *keys2)
2170 : {
2171 1623170 : int ncommon = 0;
2172 :
2173 : /* No point in searching keys2 when keys1 is empty */
2174 1623170 : if (keys1 == NIL)
2175 1582877 : return 0;
2176 :
2177 : /* walk keys2 and search for matching PathKeys in keys1 */
2178 89113 : foreach_node(PathKey, pathkey, keys2)
2179 : {
2180 : /*
2181 : * return the number of matches so far as soon as keys1 doesn't
2182 : * contain the given keys2 key.
2183 : */
2184 41439 : if (!list_member_ptr(keys1, pathkey))
2185 32912 : break;
2186 :
2187 8527 : ncommon++;
2188 : }
2189 :
2190 40293 : return ncommon;
2191 : }
2192 :
2193 : /*
2194 : * truncate_useless_pathkeys
2195 : * Shorten the given PathKey List to just the useful PathKeys. If all
2196 : * PathKeys are useful, return the input List, otherwise return a new
2197 : * List containing only the useful PathKeys.
2198 : */
2199 : List *
2200 1712518 : truncate_useless_pathkeys(PlannerInfo *root,
2201 : RelOptInfo *rel,
2202 : List *pathkeys)
2203 : {
2204 : int nuseful;
2205 : int nuseful2;
2206 1712518 : int ntotal = list_length(pathkeys);
2207 :
2208 : /*
2209 : * Here we determine how many items in 'pathkeys' might be useful for
2210 : * various Path sort ordering requirements the planner has. Operations
2211 : * such as ORDER BY require a Path's pathkeys to match the PathKeys of the
2212 : * ORDER BY in the same order, however operations such as GROUP BY and
2213 : * DISTINCT are less critical as a Unique or GroupAggregate only need to
2214 : * care that all PathKeys exist in their subpath, and don't need to care
2215 : * if they're in the same order as the clause in the query.
2216 : */
2217 1712518 : nuseful = count_common_leading_pathkeys_ordered(root->sort_pathkeys,
2218 : pathkeys);
2219 :
2220 : /* Short-circuit at any point we discover *all* pathkeys are useful */
2221 1712518 : if (nuseful == ntotal)
2222 881652 : return pathkeys;
2223 :
2224 830866 : nuseful2 = count_common_leading_pathkeys_ordered(root->window_pathkeys,
2225 : pathkeys);
2226 830866 : if (nuseful2 == ntotal)
2227 140 : return pathkeys;
2228 :
2229 830726 : nuseful = Max(nuseful, nuseful2);
2230 830726 : nuseful2 = count_common_leading_pathkeys_ordered(root->setop_pathkeys,
2231 : pathkeys);
2232 830726 : if (nuseful2 == ntotal)
2233 18104 : return pathkeys;
2234 :
2235 812622 : nuseful = Max(nuseful, nuseful2);
2236 :
2237 : /*
2238 : * Check if these pathkeys are useful for GROUP BY or DISTINCT. The order
2239 : * of the pathkeys does not matter here as Unique and GroupAggregate for
2240 : * these operations can take advantage of Paths presorted by any of the
2241 : * GROUP BY/DISTINCT pathkeys.
2242 : */
2243 812622 : nuseful2 = count_common_leading_pathkeys_unordered(root->group_pathkeys,
2244 : pathkeys);
2245 812622 : if (nuseful2 == ntotal)
2246 2074 : return pathkeys;
2247 :
2248 810548 : nuseful = Max(nuseful, nuseful2);
2249 810548 : nuseful2 = count_common_leading_pathkeys_unordered(root->distinct_pathkeys,
2250 : pathkeys);
2251 :
2252 810548 : if (nuseful2 == ntotal)
2253 5307 : return pathkeys;
2254 :
2255 805241 : nuseful = Max(nuseful, nuseful2);
2256 :
2257 : /*
2258 : * Finally, check how many PathKeys might be useful for Merge Joins. This
2259 : * is a bit more expensive, so do it last and only if we've not figured
2260 : * out that all the pathkeys are useful already.
2261 : */
2262 805241 : nuseful2 = pathkeys_useful_for_merging(root, rel, pathkeys);
2263 805241 : nuseful = Max(nuseful, nuseful2);
2264 :
2265 : /*
2266 : * Note: not safe to modify input list destructively, but we can avoid
2267 : * copying the list if we're not actually going to change it
2268 : */
2269 805241 : if (nuseful == ntotal)
2270 261247 : return pathkeys;
2271 : else
2272 543994 : return list_copy_head(pathkeys, nuseful);
2273 : }
2274 :
2275 : /*
2276 : * has_useful_pathkeys
2277 : * Detect whether the specified rel could have any pathkeys that are
2278 : * useful according to truncate_useless_pathkeys().
2279 : *
2280 : * This is a cheap test that lets us skip building pathkeys at all in very
2281 : * simple queries. It's OK to err in the direction of returning "true" when
2282 : * there really aren't any usable pathkeys, but erring in the other direction
2283 : * is bad --- so keep this in sync with the routines above!
2284 : *
2285 : * We could make the test more complex, for example checking to see if any of
2286 : * the joinclauses are really mergejoinable, but that likely wouldn't win
2287 : * often enough to repay the extra cycles. Queries with neither a join nor
2288 : * a sort are reasonably common, though, so this much work seems worthwhile.
2289 : */
2290 : bool
2291 478420 : has_useful_pathkeys(PlannerInfo *root, RelOptInfo *rel)
2292 : {
2293 478420 : if (rel->joininfo != NIL || rel->has_eclass_joins)
2294 298216 : return true; /* might be able to use pathkeys for merging */
2295 180204 : if (root->query_pathkeys != NIL)
2296 59575 : return true; /* the upper planner might need them */
2297 :
2298 120629 : return false; /* definitely useless */
2299 : }
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