Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * joinpath.c
4 : * Routines to find all possible paths for processing a set of joins
5 : *
6 : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : *
10 : * IDENTIFICATION
11 : * src/backend/optimizer/path/joinpath.c
12 : *
13 : *-------------------------------------------------------------------------
14 : */
15 : #include "postgres.h"
16 :
17 : #include "executor/executor.h"
18 : #include "foreign/fdwapi.h"
19 : #include "nodes/nodeFuncs.h"
20 : #include "optimizer/cost.h"
21 : #include "optimizer/optimizer.h"
22 : #include "optimizer/pathnode.h"
23 : #include "optimizer/paths.h"
24 : #include "optimizer/placeholder.h"
25 : #include "optimizer/planmain.h"
26 : #include "optimizer/restrictinfo.h"
27 : #include "utils/lsyscache.h"
28 : #include "utils/typcache.h"
29 :
30 : /* Hooks for plugins to get control in add_paths_to_joinrel() */
31 : set_join_pathlist_hook_type set_join_pathlist_hook = NULL;
32 : join_path_setup_hook_type join_path_setup_hook = NULL;
33 :
34 : /*
35 : * Paths parameterized by a parent rel can be considered to be parameterized
36 : * by any of its children, when we are performing partitionwise joins. These
37 : * macros simplify checking for such cases. Beware multiple eval of args.
38 : */
39 : #define PATH_PARAM_BY_PARENT(path, rel) \
40 : ((path)->param_info && bms_overlap(PATH_REQ_OUTER(path), \
41 : (rel)->top_parent_relids))
42 : #define PATH_PARAM_BY_REL_SELF(path, rel) \
43 : ((path)->param_info && bms_overlap(PATH_REQ_OUTER(path), (rel)->relids))
44 :
45 : #define PATH_PARAM_BY_REL(path, rel) \
46 : (PATH_PARAM_BY_REL_SELF(path, rel) || PATH_PARAM_BY_PARENT(path, rel))
47 :
48 : static void try_partial_mergejoin_path(PlannerInfo *root,
49 : RelOptInfo *joinrel,
50 : Path *outer_path,
51 : Path *inner_path,
52 : List *pathkeys,
53 : List *mergeclauses,
54 : List *outersortkeys,
55 : List *innersortkeys,
56 : JoinType jointype,
57 : JoinPathExtraData *extra);
58 : static void sort_inner_and_outer(PlannerInfo *root, RelOptInfo *joinrel,
59 : RelOptInfo *outerrel, RelOptInfo *innerrel,
60 : JoinType jointype, JoinPathExtraData *extra);
61 : static void match_unsorted_outer(PlannerInfo *root, RelOptInfo *joinrel,
62 : RelOptInfo *outerrel, RelOptInfo *innerrel,
63 : JoinType jointype, JoinPathExtraData *extra);
64 : static void consider_parallel_nestloop(PlannerInfo *root,
65 : RelOptInfo *joinrel,
66 : RelOptInfo *outerrel,
67 : RelOptInfo *innerrel,
68 : JoinType jointype,
69 : JoinPathExtraData *extra);
70 : static void consider_parallel_mergejoin(PlannerInfo *root,
71 : RelOptInfo *joinrel,
72 : RelOptInfo *outerrel,
73 : RelOptInfo *innerrel,
74 : JoinType jointype,
75 : JoinPathExtraData *extra,
76 : Path *inner_cheapest_total);
77 : static void hash_inner_and_outer(PlannerInfo *root, RelOptInfo *joinrel,
78 : RelOptInfo *outerrel, RelOptInfo *innerrel,
79 : JoinType jointype, JoinPathExtraData *extra);
80 : static List *select_mergejoin_clauses(PlannerInfo *root,
81 : RelOptInfo *joinrel,
82 : RelOptInfo *outerrel,
83 : RelOptInfo *innerrel,
84 : List *restrictlist,
85 : JoinType jointype,
86 : bool *mergejoin_allowed);
87 : static void generate_mergejoin_paths(PlannerInfo *root,
88 : RelOptInfo *joinrel,
89 : RelOptInfo *innerrel,
90 : Path *outerpath,
91 : JoinType jointype,
92 : JoinPathExtraData *extra,
93 : bool useallclauses,
94 : Path *inner_cheapest_total,
95 : List *merge_pathkeys,
96 : bool is_partial);
97 :
98 :
99 : /*
100 : * add_paths_to_joinrel
101 : * Given a join relation and two component rels from which it can be made,
102 : * consider all possible paths that use the two component rels as outer
103 : * and inner rel respectively. Add these paths to the join rel's pathlist
104 : * if they survive comparison with other paths (and remove any existing
105 : * paths that are dominated by these paths).
106 : *
107 : * Modifies the pathlist field of the joinrel node to contain the best
108 : * paths found so far.
109 : *
110 : * jointype is not necessarily the same as sjinfo->jointype; it might be
111 : * "flipped around" if we are considering joining the rels in the opposite
112 : * direction from what's indicated in sjinfo.
113 : *
114 : * Also, this routine accepts the special JoinTypes JOIN_UNIQUE_OUTER and
115 : * JOIN_UNIQUE_INNER to indicate that the outer or inner relation has been
116 : * unique-ified and a regular inner join should then be applied. These values
117 : * are not allowed to propagate outside this routine, however. Path cost
118 : * estimation code, as well as match_unsorted_outer, may need to recognize that
119 : * it's dealing with such a case --- the combination of nominal jointype INNER
120 : * with sjinfo->jointype == JOIN_SEMI indicates that.
121 : */
122 : void
123 781440 : add_paths_to_joinrel(PlannerInfo *root,
124 : RelOptInfo *joinrel,
125 : RelOptInfo *outerrel,
126 : RelOptInfo *innerrel,
127 : JoinType jointype,
128 : SpecialJoinInfo *sjinfo,
129 : List *restrictlist)
130 : {
131 781440 : JoinType save_jointype = jointype;
132 : JoinPathExtraData extra;
133 781440 : bool mergejoin_allowed = true;
134 : ListCell *lc;
135 : Relids joinrelids;
136 :
137 : /*
138 : * PlannerInfo doesn't contain the SpecialJoinInfos created for joins
139 : * between child relations, even if there is a SpecialJoinInfo node for
140 : * the join between the topmost parents. So, while calculating Relids set
141 : * representing the restriction, consider relids of topmost parent of
142 : * partitions.
143 : */
144 781440 : if (joinrel->reloptkind == RELOPT_OTHER_JOINREL)
145 64948 : joinrelids = joinrel->top_parent_relids;
146 : else
147 716492 : joinrelids = joinrel->relids;
148 :
149 781440 : extra.restrictlist = restrictlist;
150 781440 : extra.mergeclause_list = NIL;
151 781440 : extra.sjinfo = sjinfo;
152 781440 : extra.param_source_rels = NULL;
153 781440 : extra.pgs_mask = joinrel->pgs_mask;
154 :
155 : /*
156 : * Give extensions a chance to take control. In particular, an extension
157 : * might want to modify extra.pgs_mask. It's possible to override pgs_mask
158 : * on a query-wide basis using join_search_hook, or for a particular
159 : * relation using joinrel_setup_hook, but extensions that want to provide
160 : * different advice for the same joinrel based on the choice of innerrel
161 : * and outerrel will need to use this hook.
162 : *
163 : * A very simple way for an extension to use this hook is to set
164 : * extra.pgs_mask &= ~PGS_JOIN_ANY, if it simply doesn't want any of the
165 : * paths generated by this call to add_paths_to_joinrel() to be selected.
166 : * An extension could use this technique to constrain the join order,
167 : * since it could thereby arrange to reject all paths from join orders
168 : * that it does not like. An extension can also selectively clear bits
169 : * from extra.pgs_mask to rule out specific techniques for specific joins,
170 : * or could even set additional bits to re-allow methods disabled at some
171 : * higher level.
172 : *
173 : * NB: Below this point, this function should be careful to reference
174 : * extra.pgs_mask rather than rel->pgs_mask to avoid disregarding any
175 : * changes made by the hook we're about to call.
176 : */
177 781440 : if (join_path_setup_hook)
178 0 : join_path_setup_hook(root, joinrel, outerrel, innerrel,
179 : jointype, &extra);
180 :
181 : /*
182 : * See if the inner relation is provably unique for this outer rel.
183 : *
184 : * We have some special cases: for JOIN_SEMI, it doesn't matter since the
185 : * executor can make the equivalent optimization anyway. It also doesn't
186 : * help enable use of Memoize, since a semijoin with a provably unique
187 : * inner side should have been reduced to an inner join in that case.
188 : * Therefore, we need not expend planner cycles on proofs. (For
189 : * JOIN_ANTI, although it doesn't help the executor for the same reason,
190 : * it can benefit Memoize paths.) For JOIN_UNIQUE_INNER, we must be
191 : * considering a semijoin whose inner side is not provably unique (else
192 : * reduce_unique_semijoins would've simplified it), so there's no point in
193 : * calling innerrel_is_unique. However, if the LHS covers all of the
194 : * semijoin's min_lefthand, then it's appropriate to set inner_unique
195 : * because the unique relation produced by create_unique_paths will be
196 : * unique relative to the LHS. (If we have an LHS that's only part of the
197 : * min_lefthand, that is *not* true.) For JOIN_UNIQUE_OUTER, pass
198 : * JOIN_INNER to avoid letting that value escape this module.
199 : */
200 781440 : switch (jointype)
201 : {
202 7652 : case JOIN_SEMI:
203 7652 : extra.inner_unique = false; /* well, unproven */
204 7652 : break;
205 6336 : case JOIN_UNIQUE_INNER:
206 12672 : extra.inner_unique = bms_is_subset(sjinfo->min_lefthand,
207 6336 : outerrel->relids);
208 6336 : break;
209 6336 : case JOIN_UNIQUE_OUTER:
210 6336 : extra.inner_unique = innerrel_is_unique(root,
211 : joinrel->relids,
212 : outerrel->relids,
213 : innerrel,
214 : JOIN_INNER,
215 : restrictlist,
216 : false);
217 6336 : break;
218 761116 : default:
219 761116 : extra.inner_unique = innerrel_is_unique(root,
220 : joinrel->relids,
221 : outerrel->relids,
222 : innerrel,
223 : jointype,
224 : restrictlist,
225 : false);
226 761116 : break;
227 : }
228 :
229 : /*
230 : * If the outer or inner relation has been unique-ified, handle as a plain
231 : * inner join.
232 : */
233 781440 : if (jointype == JOIN_UNIQUE_OUTER || jointype == JOIN_UNIQUE_INNER)
234 12672 : jointype = JOIN_INNER;
235 :
236 : /*
237 : * Find potential mergejoin clauses. We can skip this if we are not
238 : * interested in doing a mergejoin. However, mergejoin may be our only
239 : * way of implementing a full outer join, so in that case we don't care
240 : * whether mergejoins are disabled.
241 : */
242 781440 : if ((extra.pgs_mask & PGS_MERGEJOIN_ANY) != 0 || jointype == JOIN_FULL)
243 777496 : extra.mergeclause_list = select_mergejoin_clauses(root,
244 : joinrel,
245 : outerrel,
246 : innerrel,
247 : restrictlist,
248 : jointype,
249 : &mergejoin_allowed);
250 :
251 : /*
252 : * If it's SEMI, ANTI, or inner_unique join, compute correction factors
253 : * for cost estimation. These will be the same for all paths.
254 : */
255 781440 : if (jointype == JOIN_SEMI || jointype == JOIN_ANTI || extra.inner_unique)
256 223956 : compute_semi_anti_join_factors(root, joinrel, outerrel, innerrel,
257 : jointype, sjinfo, restrictlist,
258 : &extra.semifactors);
259 :
260 : /*
261 : * Decide whether it's sensible to generate parameterized paths for this
262 : * joinrel, and if so, which relations such paths should require. There
263 : * is usually no need to create a parameterized result path unless there
264 : * is a join order restriction that prevents joining one of our input rels
265 : * directly to the parameter source rel instead of joining to the other
266 : * input rel. (But see allow_star_schema_join().) This restriction
267 : * reduces the number of parameterized paths we have to deal with at
268 : * higher join levels, without compromising the quality of the resulting
269 : * plan. We express the restriction as a Relids set that must overlap the
270 : * parameterization of any proposed join path. Note: param_source_rels
271 : * should contain only baserels, not OJ relids, so starting from
272 : * all_baserels not all_query_rels is correct.
273 : */
274 1519444 : foreach(lc, root->join_info_list)
275 : {
276 738004 : SpecialJoinInfo *sjinfo2 = (SpecialJoinInfo *) lfirst(lc);
277 :
278 : /*
279 : * SJ is relevant to this join if we have some part of its RHS
280 : * (possibly not all of it), and haven't yet joined to its LHS. (This
281 : * test is pretty simplistic, but should be sufficient considering the
282 : * join has already been proven legal.) If the SJ is relevant, it
283 : * presents constraints for joining to anything not in its RHS.
284 : */
285 738004 : if (bms_overlap(joinrelids, sjinfo2->min_righthand) &&
286 489512 : !bms_overlap(joinrelids, sjinfo2->min_lefthand))
287 21936 : extra.param_source_rels = bms_join(extra.param_source_rels,
288 21936 : bms_difference(root->all_baserels,
289 21936 : sjinfo2->min_righthand));
290 :
291 : /* full joins constrain both sides symmetrically */
292 742920 : if (sjinfo2->jointype == JOIN_FULL &&
293 4916 : bms_overlap(joinrelids, sjinfo2->min_lefthand) &&
294 4860 : !bms_overlap(joinrelids, sjinfo2->min_righthand))
295 672 : extra.param_source_rels = bms_join(extra.param_source_rels,
296 672 : bms_difference(root->all_baserels,
297 672 : sjinfo2->min_lefthand));
298 : }
299 :
300 : /*
301 : * However, when a LATERAL subquery is involved, there will simply not be
302 : * any paths for the joinrel that aren't parameterized by whatever the
303 : * subquery is parameterized by, unless its parameterization is resolved
304 : * within the joinrel. So we might as well allow additional dependencies
305 : * on whatever residual lateral dependencies the joinrel will have.
306 : */
307 1562880 : extra.param_source_rels = bms_add_members(extra.param_source_rels,
308 781440 : joinrel->lateral_relids);
309 :
310 : /*
311 : * 1. Consider mergejoin paths where both relations must be explicitly
312 : * sorted. Skip this if we can't mergejoin.
313 : */
314 781440 : if (mergejoin_allowed)
315 763798 : sort_inner_and_outer(root, joinrel, outerrel, innerrel,
316 : jointype, &extra);
317 :
318 : /*
319 : * 2. Consider paths where the outer relation need not be explicitly
320 : * sorted. This includes both nestloops and mergejoins where the outer
321 : * path is already ordered. Again, skip this if we can't mergejoin.
322 : * (That's okay because we know that nestloop can't handle
323 : * right/right-anti/right-semi/full joins at all, so it wouldn't work in
324 : * the prohibited cases either.)
325 : */
326 781440 : if (mergejoin_allowed)
327 763798 : match_unsorted_outer(root, joinrel, outerrel, innerrel,
328 : jointype, &extra);
329 :
330 : #ifdef NOT_USED
331 :
332 : /*
333 : * 3. Consider paths where the inner relation need not be explicitly
334 : * sorted. This includes mergejoins only (nestloops were already built in
335 : * match_unsorted_outer).
336 : *
337 : * Diked out as redundant 2/13/2000 -- tgl. There isn't any really
338 : * significant difference between the inner and outer side of a mergejoin,
339 : * so match_unsorted_inner creates no paths that aren't equivalent to
340 : * those made by match_unsorted_outer when add_paths_to_joinrel() is
341 : * invoked with the two rels given in the other order.
342 : */
343 : if (mergejoin_allowed)
344 : match_unsorted_inner(root, joinrel, outerrel, innerrel,
345 : jointype, &extra);
346 : #endif
347 :
348 : /*
349 : * 4. Consider paths where both outer and inner relations must be hashed
350 : * before being joined. As above, when it's a full join, we must try this
351 : * even when the path type is disabled, because it may be our only option.
352 : */
353 781440 : if ((extra.pgs_mask & PGS_HASHJOIN) != 0 || jointype == JOIN_FULL)
354 776096 : hash_inner_and_outer(root, joinrel, outerrel, innerrel,
355 : jointype, &extra);
356 :
357 : /*
358 : * 5. If inner and outer relations are foreign tables (or joins) belonging
359 : * to the same server and assigned to the same user to check access
360 : * permissions as, give the FDW a chance to push down joins.
361 : */
362 781440 : if ((extra.pgs_mask & PGS_FOREIGNJOIN) != 0 && joinrel->fdwroutine &&
363 2724 : joinrel->fdwroutine->GetForeignJoinPaths)
364 2720 : joinrel->fdwroutine->GetForeignJoinPaths(root, joinrel,
365 : outerrel, innerrel,
366 : save_jointype, &extra);
367 :
368 : /*
369 : * 6. Finally, give extensions a chance to manipulate the path list. They
370 : * could add new paths (such as CustomPaths) by calling add_path(), or
371 : * add_partial_path() if parallel aware.
372 : *
373 : * In theory, extensions could also use this hook to delete or modify
374 : * paths added by the core code, but in practice this is difficult to make
375 : * work, since it's too late to get back any paths that have already been
376 : * discarded by add_path() or add_partial_path(). If you're trying to
377 : * suppress paths, consider using join_path_setup_hook instead.
378 : */
379 781440 : if (set_join_pathlist_hook)
380 0 : set_join_pathlist_hook(root, joinrel, outerrel, innerrel,
381 : save_jointype, &extra);
382 781440 : }
383 :
384 : /*
385 : * We override the param_source_rels heuristic to accept nestloop paths in
386 : * which the outer rel satisfies some but not all of the inner path's
387 : * parameterization. This is necessary to get good plans for star-schema
388 : * scenarios, in which a parameterized path for a large table may require
389 : * parameters from multiple small tables that will not get joined directly to
390 : * each other. We can handle that by stacking nestloops that have the small
391 : * tables on the outside; but this breaks the rule the param_source_rels
392 : * heuristic is based on, namely that parameters should not be passed down
393 : * across joins unless there's a join-order-constraint-based reason to do so.
394 : * So we ignore the param_source_rels restriction when this case applies.
395 : *
396 : * allow_star_schema_join() returns true if the param_source_rels restriction
397 : * should be overridden, ie, it's okay to perform this join.
398 : */
399 : static inline bool
400 324656 : allow_star_schema_join(PlannerInfo *root,
401 : Relids outerrelids,
402 : Relids inner_paramrels)
403 : {
404 : /*
405 : * It's a star-schema case if the outer rel provides some but not all of
406 : * the inner rel's parameterization.
407 : */
408 381334 : return (bms_overlap(inner_paramrels, outerrelids) &&
409 56678 : bms_nonempty_difference(inner_paramrels, outerrelids));
410 : }
411 :
412 : /*
413 : * If the parameterization is only partly satisfied by the outer rel,
414 : * the unsatisfied part can't include any outer-join relids that could
415 : * null rels of the satisfied part. That would imply that we're trying
416 : * to use a clause involving a Var with nonempty varnullingrels at
417 : * a join level where that value isn't yet computable.
418 : *
419 : * In practice, this test never finds a problem because earlier join order
420 : * restrictions prevent us from attempting a join that would cause a problem.
421 : * (That's unsurprising, because the code worked before we ever added
422 : * outer-join relids to expression relids.) It still seems worth checking
423 : * as a backstop, but we only do so in assert-enabled builds.
424 : */
425 : #ifdef USE_ASSERT_CHECKING
426 : static inline bool
427 : have_unsafe_outer_join_ref(PlannerInfo *root,
428 : Relids outerrelids,
429 : Relids inner_paramrels)
430 : {
431 : bool result = false;
432 : Relids unsatisfied = bms_difference(inner_paramrels, outerrelids);
433 : Relids satisfied = bms_intersect(inner_paramrels, outerrelids);
434 :
435 : if (bms_overlap(unsatisfied, root->outer_join_rels))
436 : {
437 : ListCell *lc;
438 :
439 : foreach(lc, root->join_info_list)
440 : {
441 : SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);
442 :
443 : if (!bms_is_member(sjinfo->ojrelid, unsatisfied))
444 : continue; /* not relevant */
445 : if (bms_overlap(satisfied, sjinfo->min_righthand) ||
446 : (sjinfo->jointype == JOIN_FULL &&
447 : bms_overlap(satisfied, sjinfo->min_lefthand)))
448 : {
449 : result = true; /* doesn't work */
450 : break;
451 : }
452 : }
453 : }
454 :
455 : /* Waste no memory when we reject a path here */
456 : bms_free(unsatisfied);
457 : bms_free(satisfied);
458 :
459 : return result;
460 : }
461 : #endif /* USE_ASSERT_CHECKING */
462 :
463 : /*
464 : * paraminfo_get_equal_hashops
465 : * Determine if the clauses in param_info and innerrel's lateral vars
466 : * can be hashed.
467 : * Returns true if hashing is possible, otherwise false.
468 : *
469 : * Additionally, on success we collect the outer expressions and the
470 : * appropriate equality operators for each hashable parameter to innerrel.
471 : * These are returned in parallel lists in *param_exprs and *operators.
472 : * We also set *binary_mode to indicate whether strict binary matching is
473 : * required.
474 : */
475 : static bool
476 400834 : paraminfo_get_equal_hashops(PlannerInfo *root, ParamPathInfo *param_info,
477 : RelOptInfo *outerrel, RelOptInfo *innerrel,
478 : List *ph_lateral_vars, List **param_exprs,
479 : List **operators, bool *binary_mode)
480 :
481 : {
482 : List *lateral_vars;
483 : ListCell *lc;
484 :
485 400834 : *param_exprs = NIL;
486 400834 : *operators = NIL;
487 400834 : *binary_mode = false;
488 :
489 : /* Add join clauses from param_info to the hash key */
490 400834 : if (param_info != NULL)
491 : {
492 400834 : List *clauses = param_info->ppi_clauses;
493 :
494 756616 : foreach(lc, clauses)
495 : {
496 435932 : RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
497 : OpExpr *opexpr;
498 : Node *expr;
499 : Oid hasheqoperator;
500 :
501 435932 : opexpr = (OpExpr *) rinfo->clause;
502 :
503 : /*
504 : * Bail if the rinfo is not compatible. We need a join OpExpr
505 : * with 2 args.
506 : */
507 435932 : if (!IsA(opexpr, OpExpr) || list_length(opexpr->args) != 2 ||
508 418054 : !clause_sides_match_join(rinfo, outerrel->relids,
509 : innerrel->relids))
510 : {
511 80060 : list_free(*operators);
512 80060 : list_free(*param_exprs);
513 80150 : return false;
514 : }
515 :
516 355872 : if (rinfo->outer_is_left)
517 : {
518 197864 : expr = (Node *) linitial(opexpr->args);
519 197864 : hasheqoperator = rinfo->left_hasheqoperator;
520 : }
521 : else
522 : {
523 158008 : expr = (Node *) lsecond(opexpr->args);
524 158008 : hasheqoperator = rinfo->right_hasheqoperator;
525 : }
526 :
527 : /* can't do memoize if we can't hash the outer type */
528 355872 : if (!OidIsValid(hasheqoperator))
529 : {
530 90 : list_free(*operators);
531 90 : list_free(*param_exprs);
532 90 : return false;
533 : }
534 :
535 : /*
536 : * 'expr' may already exist as a parameter from a previous item in
537 : * ppi_clauses. No need to include it again, however we'd better
538 : * ensure we do switch into binary mode if required. See below.
539 : */
540 355782 : if (!list_member(*param_exprs, expr))
541 : {
542 355776 : *operators = lappend_oid(*operators, hasheqoperator);
543 355776 : *param_exprs = lappend(*param_exprs, expr);
544 : }
545 :
546 : /*
547 : * When the join operator is not hashable then it's possible that
548 : * the operator will be able to distinguish something that the
549 : * hash equality operator could not. For example with floating
550 : * point types -0.0 and +0.0 are classed as equal by the hash
551 : * function and equality function, but some other operator may be
552 : * able to tell those values apart. This means that we must put
553 : * memoize into binary comparison mode so that it does bit-by-bit
554 : * comparisons rather than a "logical" comparison as it would
555 : * using the hash equality operator.
556 : */
557 355782 : if (!OidIsValid(rinfo->hashjoinoperator))
558 1270 : *binary_mode = true;
559 : }
560 : }
561 :
562 : /* Now add any lateral vars to the cache key too */
563 320684 : lateral_vars = list_concat(ph_lateral_vars, innerrel->lateral_vars);
564 328446 : foreach(lc, lateral_vars)
565 : {
566 7960 : Node *expr = (Node *) lfirst(lc);
567 : TypeCacheEntry *typentry;
568 :
569 : /* Reject if there are any volatile functions in lateral vars */
570 7960 : if (contain_volatile_functions(expr))
571 : {
572 0 : list_free(*operators);
573 0 : list_free(*param_exprs);
574 198 : return false;
575 : }
576 :
577 7960 : typentry = lookup_type_cache(exprType(expr),
578 : TYPECACHE_HASH_PROC | TYPECACHE_EQ_OPR);
579 :
580 : /* can't use memoize without a valid hash proc and equals operator */
581 7960 : if (!OidIsValid(typentry->hash_proc) || !OidIsValid(typentry->eq_opr))
582 : {
583 198 : list_free(*operators);
584 198 : list_free(*param_exprs);
585 198 : return false;
586 : }
587 :
588 : /*
589 : * 'expr' may already exist as a parameter from the ppi_clauses. No
590 : * need to include it again, however we'd better ensure we do switch
591 : * into binary mode.
592 : */
593 7762 : if (!list_member(*param_exprs, expr))
594 : {
595 7264 : *operators = lappend_oid(*operators, typentry->eq_opr);
596 7264 : *param_exprs = lappend(*param_exprs, expr);
597 : }
598 :
599 : /*
600 : * We must go into binary mode as we don't have too much of an idea of
601 : * how these lateral Vars are being used. See comment above when we
602 : * set *binary_mode for the non-lateral Var case. This could be
603 : * relaxed a bit if we had the RestrictInfos and knew the operators
604 : * being used, however for cases like Vars that are arguments to
605 : * functions we must operate in binary mode as we don't have
606 : * visibility into what the function is doing with the Vars.
607 : */
608 7762 : *binary_mode = true;
609 : }
610 :
611 : /* We're okay to use memoize */
612 320486 : return true;
613 : }
614 :
615 : /*
616 : * extract_lateral_vars_from_PHVs
617 : * Extract lateral references within PlaceHolderVars that are due to be
618 : * evaluated at 'innerrelids'.
619 : */
620 : static List *
621 1496124 : extract_lateral_vars_from_PHVs(PlannerInfo *root, Relids innerrelids)
622 : {
623 1496124 : List *ph_lateral_vars = NIL;
624 : ListCell *lc;
625 :
626 : /* Nothing would be found if the query contains no LATERAL RTEs */
627 1496124 : if (!root->hasLateralRTEs)
628 1438510 : return NIL;
629 :
630 : /*
631 : * No need to consider PHVs that are due to be evaluated at joinrels,
632 : * since we do not add Memoize nodes on top of joinrel paths.
633 : */
634 57614 : if (bms_membership(innerrelids) == BMS_MULTIPLE)
635 22332 : return NIL;
636 :
637 38146 : foreach(lc, root->placeholder_list)
638 : {
639 2864 : PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(lc);
640 : List *vars;
641 : ListCell *cell;
642 :
643 : /* PHV is uninteresting if no lateral refs */
644 2864 : if (phinfo->ph_lateral == NULL)
645 1638 : continue;
646 :
647 : /* PHV is uninteresting if not due to be evaluated at innerrelids */
648 1226 : if (!bms_equal(phinfo->ph_eval_at, innerrelids))
649 982 : continue;
650 :
651 : /*
652 : * If the PHV does not reference any rels in innerrelids, use its
653 : * contained expression as a cache key rather than extracting the
654 : * Vars/PHVs from it and using those. This can be beneficial in cases
655 : * where the expression results in fewer distinct values to cache
656 : * tuples for.
657 : */
658 244 : if (!bms_overlap(pull_varnos(root, (Node *) phinfo->ph_var->phexpr),
659 : innerrelids))
660 : {
661 232 : ph_lateral_vars = lappend(ph_lateral_vars, phinfo->ph_var->phexpr);
662 232 : continue;
663 : }
664 :
665 : /* Fetch Vars and PHVs of lateral references within PlaceHolderVars */
666 12 : vars = pull_vars_of_level((Node *) phinfo->ph_var->phexpr, 0);
667 36 : foreach(cell, vars)
668 : {
669 24 : Node *node = (Node *) lfirst(cell);
670 :
671 24 : if (IsA(node, Var))
672 : {
673 12 : Var *var = (Var *) node;
674 :
675 : Assert(var->varlevelsup == 0);
676 :
677 12 : if (bms_is_member(var->varno, phinfo->ph_lateral))
678 0 : ph_lateral_vars = lappend(ph_lateral_vars, node);
679 : }
680 12 : else if (IsA(node, PlaceHolderVar))
681 : {
682 12 : PlaceHolderVar *phv = (PlaceHolderVar *) node;
683 :
684 : Assert(phv->phlevelsup == 0);
685 :
686 12 : if (bms_is_subset(find_placeholder_info(root, phv)->ph_eval_at,
687 12 : phinfo->ph_lateral))
688 12 : ph_lateral_vars = lappend(ph_lateral_vars, node);
689 : }
690 : else
691 : Assert(false);
692 : }
693 :
694 12 : list_free(vars);
695 : }
696 :
697 35282 : return ph_lateral_vars;
698 : }
699 :
700 : /*
701 : * get_memoize_path
702 : * If possible, make and return a Memoize path atop of 'inner_path'.
703 : * Otherwise return NULL.
704 : *
705 : * Note that currently we do not add Memoize nodes on top of join relation
706 : * paths. This is because the ParamPathInfos for join relation paths do not
707 : * maintain ppi_clauses, as the set of relevant clauses varies depending on how
708 : * the join is formed. In addition, joinrels do not maintain lateral_vars. So
709 : * we do not have a way to extract cache keys from joinrels.
710 : */
711 : static Path *
712 2102878 : get_memoize_path(PlannerInfo *root, RelOptInfo *innerrel,
713 : RelOptInfo *outerrel, Path *inner_path,
714 : Path *outer_path, JoinType jointype,
715 : JoinPathExtraData *extra)
716 : {
717 : List *param_exprs;
718 : List *hash_operators;
719 : ListCell *lc;
720 : bool binary_mode;
721 : List *ph_lateral_vars;
722 :
723 : /* Obviously not if it's disabled */
724 2102878 : if ((extra->pgs_mask & PGS_NESTLOOP_MEMOIZE) == 0)
725 6412 : return NULL;
726 :
727 : /*
728 : * We can safely not bother with all this unless we expect to perform more
729 : * than one inner scan. The first scan is always going to be a cache
730 : * miss. This would likely fail later anyway based on costs, so this is
731 : * really just to save some wasted effort.
732 : */
733 2096466 : if (outer_path->parent->rows < 2)
734 600342 : return NULL;
735 :
736 : /*
737 : * Extract lateral Vars/PHVs within PlaceHolderVars that are due to be
738 : * evaluated at innerrel. These lateral Vars/PHVs could be used as
739 : * memoize cache keys.
740 : */
741 1496124 : ph_lateral_vars = extract_lateral_vars_from_PHVs(root, innerrel->relids);
742 :
743 : /*
744 : * We can only have a memoize node when there's some kind of cache key,
745 : * either parameterized path clauses or lateral Vars. No cache key sounds
746 : * more like something a Materialize node might be more useful for.
747 : */
748 1496124 : if ((inner_path->param_info == NULL ||
749 543688 : inner_path->param_info->ppi_clauses == NIL) &&
750 985666 : innerrel->lateral_vars == NIL &&
751 : ph_lateral_vars == NIL)
752 978552 : return NULL;
753 :
754 : /*
755 : * Currently we don't do this for SEMI and ANTI joins, because nested loop
756 : * SEMI/ANTI joins don't scan the inner node to completion, which means
757 : * memoize cannot mark the cache entry as complete. Nor can we mark the
758 : * cache entry as complete after fetching the first inner tuple, because
759 : * if that tuple and the current outer tuple don't satisfy the join
760 : * clauses, a second inner tuple that satisfies the parameters would find
761 : * the cache entry already marked as complete. The only exception is when
762 : * the inner relation is provably unique, as in that case, there won't be
763 : * a second matching tuple and we can safely mark the cache entry as
764 : * complete after fetching the first inner tuple. Note that in such
765 : * cases, the SEMI join should have been reduced to an inner join by
766 : * reduce_unique_semijoins.
767 : */
768 517572 : if ((jointype == JOIN_SEMI || jointype == JOIN_ANTI) &&
769 9734 : !extra->inner_unique)
770 5942 : return NULL;
771 :
772 : /*
773 : * Memoize normally marks cache entries as complete when it runs out of
774 : * tuples to read from its subplan. However, with unique joins, Nested
775 : * Loop will skip to the next outer tuple after finding the first matching
776 : * inner tuple. This means that we may not read the inner side of the
777 : * join to completion which leaves no opportunity to mark the cache entry
778 : * as complete. To work around that, when the join is unique we
779 : * automatically mark cache entries as complete after fetching the first
780 : * tuple. This works when the entire join condition is parameterized.
781 : * Otherwise, when the parameterization is only a subset of the join
782 : * condition, we can't be sure which part of it causes the join to be
783 : * unique. This means there are no guarantees that only 1 tuple will be
784 : * read. We cannot mark the cache entry as complete after reading the
785 : * first tuple without that guarantee. This means the scope of Memoize
786 : * node's usefulness is limited to only outer rows that have no join
787 : * partner as this is the only case where Nested Loop would exhaust the
788 : * inner scan of a unique join. Since the scope is limited to that, we
789 : * just don't bother making a memoize path in this case.
790 : *
791 : * Lateral vars needn't be considered here as they're not considered when
792 : * determining if the join is unique.
793 : */
794 511630 : if (extra->inner_unique)
795 : {
796 : Bitmapset *ppi_serials;
797 :
798 305168 : if (inner_path->param_info == NULL)
799 0 : return NULL;
800 :
801 305168 : ppi_serials = inner_path->param_info->ppi_serials;
802 :
803 732122 : foreach_node(RestrictInfo, rinfo, extra->restrictlist)
804 : {
805 343062 : if (!bms_is_member(rinfo->rinfo_serial, ppi_serials))
806 110638 : return NULL;
807 : }
808 : }
809 :
810 : /*
811 : * We can't use a memoize node if there are volatile functions in the
812 : * inner rel's target list or restrict list. A cache hit could reduce the
813 : * number of calls to these functions.
814 : */
815 400992 : if (contain_volatile_functions((Node *) innerrel->reltarget))
816 0 : return NULL;
817 :
818 647524 : foreach(lc, innerrel->baserestrictinfo)
819 : {
820 246688 : RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
821 :
822 246688 : if (contain_volatile_functions((Node *) rinfo))
823 156 : return NULL;
824 : }
825 :
826 : /*
827 : * Also check the parameterized path restrictinfos for volatile functions.
828 : * Indexed functions must be immutable so shouldn't have any volatile
829 : * functions, however, with a lateral join the inner scan may not be an
830 : * index scan.
831 : */
832 400836 : if (inner_path->param_info != NULL)
833 : {
834 867454 : foreach(lc, inner_path->param_info->ppi_clauses)
835 : {
836 466620 : RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
837 :
838 466620 : if (contain_volatile_functions((Node *) rinfo))
839 2 : return NULL;
840 : }
841 : }
842 :
843 : /* Check if we have hash ops for each parameter to the path */
844 400834 : if (paraminfo_get_equal_hashops(root,
845 : inner_path->param_info,
846 400834 : outerrel->top_parent ?
847 : outerrel->top_parent : outerrel,
848 : innerrel,
849 : ph_lateral_vars,
850 : ¶m_exprs,
851 : &hash_operators,
852 : &binary_mode))
853 : {
854 320486 : return (Path *) create_memoize_path(root,
855 : innerrel,
856 : inner_path,
857 : param_exprs,
858 : hash_operators,
859 320486 : extra->inner_unique,
860 : binary_mode,
861 : outer_path->rows);
862 : }
863 :
864 80348 : return NULL;
865 : }
866 :
867 : /*
868 : * try_nestloop_path
869 : * Consider a nestloop join path; if it appears useful, push it into
870 : * the joinrel's pathlist via add_path().
871 : */
872 : static void
873 3509284 : try_nestloop_path(PlannerInfo *root,
874 : RelOptInfo *joinrel,
875 : Path *outer_path,
876 : Path *inner_path,
877 : List *pathkeys,
878 : JoinType jointype,
879 : uint64 nestloop_subtype,
880 : JoinPathExtraData *extra)
881 : {
882 : Relids required_outer;
883 : JoinCostWorkspace workspace;
884 3509284 : RelOptInfo *innerrel = inner_path->parent;
885 3509284 : RelOptInfo *outerrel = outer_path->parent;
886 : Relids innerrelids;
887 : Relids outerrelids;
888 3509284 : Relids inner_paramrels = PATH_REQ_OUTER(inner_path);
889 3509284 : Relids outer_paramrels = PATH_REQ_OUTER(outer_path);
890 :
891 : /*
892 : * If we are forming an outer join at this join, it's nonsensical to use
893 : * an input path that uses the outer join as part of its parameterization.
894 : * (This can happen despite our join order restrictions, since those apply
895 : * to what is in an input relation not what its parameters are.)
896 : */
897 4200626 : if (extra->sjinfo->ojrelid != 0 &&
898 1382684 : (bms_is_member(extra->sjinfo->ojrelid, inner_paramrels) ||
899 691342 : bms_is_member(extra->sjinfo->ojrelid, outer_paramrels)))
900 322600 : return;
901 :
902 : /*
903 : * Any parameterization of the input paths refers to topmost parents of
904 : * the relevant relations, because reparameterize_path_by_child() hasn't
905 : * been called yet. So we must consider topmost parents of the relations
906 : * being joined, too, while determining parameterization of the result and
907 : * checking for disallowed parameterization cases.
908 : */
909 3509164 : if (innerrel->top_parent_relids)
910 172816 : innerrelids = innerrel->top_parent_relids;
911 : else
912 3336348 : innerrelids = innerrel->relids;
913 :
914 3509164 : if (outerrel->top_parent_relids)
915 172816 : outerrelids = outerrel->top_parent_relids;
916 : else
917 3336348 : outerrelids = outerrel->relids;
918 :
919 : /*
920 : * Check to see if proposed path is still parameterized, and reject if the
921 : * parameterization wouldn't be sensible --- unless allow_star_schema_join
922 : * says to allow it anyway.
923 : */
924 3509164 : required_outer = calc_nestloop_required_outer(outerrelids, outer_paramrels,
925 : innerrelids, inner_paramrels);
926 3509164 : if (required_outer &&
927 375204 : !bms_overlap(required_outer, extra->param_source_rels) &&
928 324656 : !allow_star_schema_join(root, outerrelids, inner_paramrels))
929 : {
930 : /* Waste no memory when we reject a path here */
931 322480 : bms_free(required_outer);
932 322480 : return;
933 : }
934 :
935 : /* If we got past that, we shouldn't have any unsafe outer-join refs */
936 : Assert(!have_unsafe_outer_join_ref(root, outerrelids, inner_paramrels));
937 :
938 : /*
939 : * If the inner path is parameterized, it is parameterized by the topmost
940 : * parent of the outer rel, not the outer rel itself. We will need to
941 : * translate the parameterization, if this path is chosen, during
942 : * create_plan(). Here we just check whether we will be able to perform
943 : * the translation, and if not avoid creating a nestloop path.
944 : */
945 3186684 : if (PATH_PARAM_BY_PARENT(inner_path, outer_path->parent) &&
946 12988 : !path_is_reparameterizable_by_child(inner_path, outer_path->parent))
947 : {
948 0 : bms_free(required_outer);
949 0 : return;
950 : }
951 :
952 : /*
953 : * Do a precheck to quickly eliminate obviously-inferior paths. We
954 : * calculate a cheap lower bound on the path's cost and then use
955 : * add_path_precheck() to see if the path is clearly going to be dominated
956 : * by some existing path for the joinrel. If not, do the full pushup with
957 : * creating a fully valid path structure and submitting it to add_path().
958 : * The latter two steps are expensive enough to make this two-phase
959 : * methodology worthwhile.
960 : */
961 3186684 : initial_cost_nestloop(root, &workspace, jointype,
962 : nestloop_subtype | PGS_CONSIDER_NONPARTIAL,
963 : outer_path, inner_path, extra);
964 :
965 3186684 : if (add_path_precheck(joinrel, workspace.disabled_nodes,
966 : workspace.startup_cost, workspace.total_cost,
967 : pathkeys, required_outer))
968 : {
969 1479500 : add_path(joinrel, (Path *)
970 1479500 : create_nestloop_path(root,
971 : joinrel,
972 : jointype,
973 : &workspace,
974 : extra,
975 : outer_path,
976 : inner_path,
977 : extra->restrictlist,
978 : pathkeys,
979 : required_outer));
980 : }
981 : else
982 : {
983 : /* Waste no memory when we reject a path here */
984 1707184 : bms_free(required_outer);
985 : }
986 : }
987 :
988 : /*
989 : * try_partial_nestloop_path
990 : * Consider a partial nestloop join path; if it appears useful, push it into
991 : * the joinrel's partial_pathlist via add_partial_path().
992 : */
993 : static void
994 201914 : try_partial_nestloop_path(PlannerInfo *root,
995 : RelOptInfo *joinrel,
996 : Path *outer_path,
997 : Path *inner_path,
998 : List *pathkeys,
999 : JoinType jointype,
1000 : uint64 nestloop_subtype,
1001 : JoinPathExtraData *extra)
1002 : {
1003 : JoinCostWorkspace workspace;
1004 :
1005 : /*
1006 : * If the inner path is parameterized, the parameterization must be fully
1007 : * satisfied by the proposed outer path. Parameterized partial paths are
1008 : * not supported. The caller should already have verified that no lateral
1009 : * rels are required here.
1010 : */
1011 : Assert(bms_is_empty(joinrel->lateral_relids));
1012 : Assert(bms_is_empty(PATH_REQ_OUTER(outer_path)));
1013 201914 : if (inner_path->param_info != NULL)
1014 : {
1015 15478 : Relids inner_paramrels = inner_path->param_info->ppi_req_outer;
1016 15478 : RelOptInfo *outerrel = outer_path->parent;
1017 : Relids outerrelids;
1018 :
1019 : /*
1020 : * The inner and outer paths are parameterized, if at all, by the top
1021 : * level parents, not the child relations, so we must use those relids
1022 : * for our parameterization tests.
1023 : */
1024 15478 : if (outerrel->top_parent_relids)
1025 11412 : outerrelids = outerrel->top_parent_relids;
1026 : else
1027 4066 : outerrelids = outerrel->relids;
1028 :
1029 15478 : if (!bms_is_subset(inner_paramrels, outerrelids))
1030 157870 : return;
1031 : }
1032 :
1033 : /*
1034 : * If the inner path is parameterized, it is parameterized by the topmost
1035 : * parent of the outer rel, not the outer rel itself. We will need to
1036 : * translate the parameterization, if this path is chosen, during
1037 : * create_plan(). Here we just check whether we will be able to perform
1038 : * the translation, and if not avoid creating a nestloop path.
1039 : */
1040 200550 : if (PATH_PARAM_BY_PARENT(inner_path, outer_path->parent) &&
1041 10440 : !path_is_reparameterizable_by_child(inner_path, outer_path->parent))
1042 0 : return;
1043 :
1044 : /*
1045 : * Before creating a path, get a quick lower bound on what it is likely to
1046 : * cost. Bail out right away if it looks terrible.
1047 : */
1048 200550 : initial_cost_nestloop(root, &workspace, jointype, nestloop_subtype,
1049 : outer_path, inner_path, extra);
1050 200550 : if (!add_partial_path_precheck(joinrel, workspace.disabled_nodes,
1051 : workspace.total_cost, pathkeys))
1052 156506 : return;
1053 :
1054 : /* Might be good enough to be worth trying, so let's try it. */
1055 44044 : add_partial_path(joinrel, (Path *)
1056 44044 : create_nestloop_path(root,
1057 : joinrel,
1058 : jointype,
1059 : &workspace,
1060 : extra,
1061 : outer_path,
1062 : inner_path,
1063 : extra->restrictlist,
1064 : pathkeys,
1065 : NULL));
1066 : }
1067 :
1068 : /*
1069 : * try_mergejoin_path
1070 : * Consider a merge join path; if it appears useful, push it into
1071 : * the joinrel's pathlist via add_path().
1072 : */
1073 : static void
1074 1501404 : try_mergejoin_path(PlannerInfo *root,
1075 : RelOptInfo *joinrel,
1076 : Path *outer_path,
1077 : Path *inner_path,
1078 : List *pathkeys,
1079 : List *mergeclauses,
1080 : List *outersortkeys,
1081 : List *innersortkeys,
1082 : JoinType jointype,
1083 : JoinPathExtraData *extra,
1084 : bool is_partial)
1085 : {
1086 : Relids required_outer;
1087 1501404 : int outer_presorted_keys = 0;
1088 : JoinCostWorkspace workspace;
1089 :
1090 1501404 : if (is_partial)
1091 : {
1092 23350 : try_partial_mergejoin_path(root,
1093 : joinrel,
1094 : outer_path,
1095 : inner_path,
1096 : pathkeys,
1097 : mergeclauses,
1098 : outersortkeys,
1099 : innersortkeys,
1100 : jointype,
1101 : extra);
1102 64500 : return;
1103 : }
1104 :
1105 : /*
1106 : * If we are forming an outer join at this join, it's nonsensical to use
1107 : * an input path that uses the outer join as part of its parameterization.
1108 : * (This can happen despite our join order restrictions, since those apply
1109 : * to what is in an input relation not what its parameters are.)
1110 : */
1111 1864454 : if (extra->sjinfo->ojrelid != 0 &&
1112 772800 : (bms_is_member(extra->sjinfo->ojrelid, PATH_REQ_OUTER(inner_path)) ||
1113 386400 : bms_is_member(extra->sjinfo->ojrelid, PATH_REQ_OUTER(outer_path))))
1114 12 : return;
1115 :
1116 : /*
1117 : * Check to see if proposed path is still parameterized, and reject if the
1118 : * parameterization wouldn't be sensible.
1119 : */
1120 1478042 : required_outer = calc_non_nestloop_required_outer(outer_path,
1121 : inner_path);
1122 1478042 : if (required_outer &&
1123 47520 : !bms_overlap(required_outer, extra->param_source_rels))
1124 : {
1125 : /* Waste no memory when we reject a path here */
1126 41138 : bms_free(required_outer);
1127 41138 : return;
1128 : }
1129 :
1130 : /*
1131 : * If the given paths are already well enough ordered, we can skip doing
1132 : * an explicit sort.
1133 : *
1134 : * We need to determine the number of presorted keys of the outer path to
1135 : * decide whether explicit incremental sort can be applied when
1136 : * outersortkeys is not NIL. We do not need to do the same for the inner
1137 : * path though, as incremental sort currently does not support
1138 : * mark/restore.
1139 : */
1140 2155346 : if (outersortkeys &&
1141 718442 : pathkeys_count_contained_in(outersortkeys, outer_path->pathkeys,
1142 : &outer_presorted_keys))
1143 17914 : outersortkeys = NIL;
1144 2602144 : if (innersortkeys &&
1145 1165240 : pathkeys_contained_in(innersortkeys, inner_path->pathkeys))
1146 31372 : innersortkeys = NIL;
1147 :
1148 : /*
1149 : * See comments in try_nestloop_path().
1150 : */
1151 1436904 : initial_cost_mergejoin(root, &workspace, jointype, mergeclauses,
1152 : outer_path, inner_path,
1153 : outersortkeys, innersortkeys,
1154 : outer_presorted_keys,
1155 : extra);
1156 :
1157 1436904 : if (add_path_precheck(joinrel, workspace.disabled_nodes,
1158 : workspace.startup_cost, workspace.total_cost,
1159 : pathkeys, required_outer))
1160 : {
1161 407838 : add_path(joinrel, (Path *)
1162 407838 : create_mergejoin_path(root,
1163 : joinrel,
1164 : jointype,
1165 : &workspace,
1166 : extra,
1167 : outer_path,
1168 : inner_path,
1169 : extra->restrictlist,
1170 : pathkeys,
1171 : required_outer,
1172 : mergeclauses,
1173 : outersortkeys,
1174 : innersortkeys,
1175 : outer_presorted_keys));
1176 : }
1177 : else
1178 : {
1179 : /* Waste no memory when we reject a path here */
1180 1029066 : bms_free(required_outer);
1181 : }
1182 : }
1183 :
1184 : /*
1185 : * try_partial_mergejoin_path
1186 : * Consider a partial merge join path; if it appears useful, push it into
1187 : * the joinrel's pathlist via add_partial_path().
1188 : */
1189 : static void
1190 99914 : try_partial_mergejoin_path(PlannerInfo *root,
1191 : RelOptInfo *joinrel,
1192 : Path *outer_path,
1193 : Path *inner_path,
1194 : List *pathkeys,
1195 : List *mergeclauses,
1196 : List *outersortkeys,
1197 : List *innersortkeys,
1198 : JoinType jointype,
1199 : JoinPathExtraData *extra)
1200 : {
1201 99914 : int outer_presorted_keys = 0;
1202 : JoinCostWorkspace workspace;
1203 :
1204 : /*
1205 : * See comments in try_partial_hashjoin_path().
1206 : */
1207 : Assert(bms_is_empty(joinrel->lateral_relids));
1208 : Assert(bms_is_empty(PATH_REQ_OUTER(outer_path)));
1209 99914 : if (!bms_is_empty(PATH_REQ_OUTER(inner_path)))
1210 34018 : return;
1211 :
1212 : /*
1213 : * If the given paths are already well enough ordered, we can skip doing
1214 : * an explicit sort.
1215 : *
1216 : * We need to determine the number of presorted keys of the outer path to
1217 : * decide whether explicit incremental sort can be applied when
1218 : * outersortkeys is not NIL. We do not need to do the same for the inner
1219 : * path though, as incremental sort currently does not support
1220 : * mark/restore.
1221 : */
1222 176478 : if (outersortkeys &&
1223 76564 : pathkeys_count_contained_in(outersortkeys, outer_path->pathkeys,
1224 : &outer_presorted_keys))
1225 246 : outersortkeys = NIL;
1226 196580 : if (innersortkeys &&
1227 96666 : pathkeys_contained_in(innersortkeys, inner_path->pathkeys))
1228 642 : innersortkeys = NIL;
1229 :
1230 : /*
1231 : * See comments in try_partial_nestloop_path().
1232 : */
1233 99914 : initial_cost_mergejoin(root, &workspace, jointype, mergeclauses,
1234 : outer_path, inner_path,
1235 : outersortkeys, innersortkeys,
1236 : outer_presorted_keys,
1237 : extra);
1238 :
1239 99914 : if (!add_partial_path_precheck(joinrel, workspace.disabled_nodes,
1240 : workspace.total_cost, pathkeys))
1241 34018 : return;
1242 :
1243 : /* Might be good enough to be worth trying, so let's try it. */
1244 65896 : add_partial_path(joinrel, (Path *)
1245 65896 : create_mergejoin_path(root,
1246 : joinrel,
1247 : jointype,
1248 : &workspace,
1249 : extra,
1250 : outer_path,
1251 : inner_path,
1252 : extra->restrictlist,
1253 : pathkeys,
1254 : NULL,
1255 : mergeclauses,
1256 : outersortkeys,
1257 : innersortkeys,
1258 : outer_presorted_keys));
1259 : }
1260 :
1261 : /*
1262 : * try_hashjoin_path
1263 : * Consider a hash join path; if it appears useful, push it into
1264 : * the joinrel's pathlist via add_path().
1265 : */
1266 : static void
1267 880994 : try_hashjoin_path(PlannerInfo *root,
1268 : RelOptInfo *joinrel,
1269 : Path *outer_path,
1270 : Path *inner_path,
1271 : List *hashclauses,
1272 : JoinType jointype,
1273 : JoinPathExtraData *extra)
1274 : {
1275 : Relids required_outer;
1276 : JoinCostWorkspace workspace;
1277 :
1278 : /*
1279 : * If we are forming an outer join at this join, it's nonsensical to use
1280 : * an input path that uses the outer join as part of its parameterization.
1281 : * (This can happen despite our join order restrictions, since those apply
1282 : * to what is in an input relation not what its parameters are.)
1283 : */
1284 1135192 : if (extra->sjinfo->ojrelid != 0 &&
1285 508366 : (bms_is_member(extra->sjinfo->ojrelid, PATH_REQ_OUTER(inner_path)) ||
1286 254168 : bms_is_member(extra->sjinfo->ojrelid, PATH_REQ_OUTER(outer_path))))
1287 129080 : return;
1288 :
1289 : /*
1290 : * Check to see if proposed path is still parameterized, and reject if the
1291 : * parameterization wouldn't be sensible.
1292 : */
1293 880934 : required_outer = calc_non_nestloop_required_outer(outer_path,
1294 : inner_path);
1295 880934 : if (required_outer &&
1296 146972 : !bms_overlap(required_outer, extra->param_source_rels))
1297 : {
1298 : /* Waste no memory when we reject a path here */
1299 129020 : bms_free(required_outer);
1300 129020 : return;
1301 : }
1302 :
1303 : /*
1304 : * See comments in try_nestloop_path(). Also note that hashjoin paths
1305 : * never have any output pathkeys, per comments in create_hashjoin_path.
1306 : */
1307 751914 : initial_cost_hashjoin(root, &workspace, jointype, hashclauses,
1308 : outer_path, inner_path, extra, false);
1309 :
1310 751914 : if (add_path_precheck(joinrel, workspace.disabled_nodes,
1311 : workspace.startup_cost, workspace.total_cost,
1312 : NIL, required_outer))
1313 : {
1314 359044 : add_path(joinrel, (Path *)
1315 359044 : create_hashjoin_path(root,
1316 : joinrel,
1317 : jointype,
1318 : &workspace,
1319 : extra,
1320 : outer_path,
1321 : inner_path,
1322 : false, /* parallel_hash */
1323 : extra->restrictlist,
1324 : required_outer,
1325 : hashclauses));
1326 : }
1327 : else
1328 : {
1329 : /* Waste no memory when we reject a path here */
1330 392870 : bms_free(required_outer);
1331 : }
1332 : }
1333 :
1334 : /*
1335 : * try_partial_hashjoin_path
1336 : * Consider a partial hashjoin join path; if it appears useful, push it into
1337 : * the joinrel's partial_pathlist via add_partial_path().
1338 : * The outer side is partial. If parallel_hash is true, then the inner path
1339 : * must be partial and will be run in parallel to create one or more shared
1340 : * hash tables; otherwise the inner path must be complete and a copy of it
1341 : * is run in every process to create separate identical private hash tables.
1342 : */
1343 : static void
1344 147860 : try_partial_hashjoin_path(PlannerInfo *root,
1345 : RelOptInfo *joinrel,
1346 : Path *outer_path,
1347 : Path *inner_path,
1348 : List *hashclauses,
1349 : JoinType jointype,
1350 : JoinPathExtraData *extra,
1351 : bool parallel_hash)
1352 : {
1353 : JoinCostWorkspace workspace;
1354 :
1355 : /*
1356 : * If the inner path is parameterized, we can't use a partial hashjoin.
1357 : * Parameterized partial paths are not supported. The caller should
1358 : * already have verified that no lateral rels are required here.
1359 : */
1360 : Assert(bms_is_empty(joinrel->lateral_relids));
1361 : Assert(bms_is_empty(PATH_REQ_OUTER(outer_path)));
1362 147860 : if (!bms_is_empty(PATH_REQ_OUTER(inner_path)))
1363 40700 : return;
1364 :
1365 : /*
1366 : * Before creating a path, get a quick lower bound on what it is likely to
1367 : * cost. Bail out right away if it looks terrible.
1368 : */
1369 147860 : initial_cost_hashjoin(root, &workspace, jointype, hashclauses,
1370 : outer_path, inner_path, extra, parallel_hash);
1371 147860 : if (!add_partial_path_precheck(joinrel, workspace.disabled_nodes,
1372 : workspace.total_cost, NIL))
1373 40700 : return;
1374 :
1375 : /* Might be good enough to be worth trying, so let's try it. */
1376 107160 : add_partial_path(joinrel, (Path *)
1377 107160 : create_hashjoin_path(root,
1378 : joinrel,
1379 : jointype,
1380 : &workspace,
1381 : extra,
1382 : outer_path,
1383 : inner_path,
1384 : parallel_hash,
1385 : extra->restrictlist,
1386 : NULL,
1387 : hashclauses));
1388 : }
1389 :
1390 : /*
1391 : * sort_inner_and_outer
1392 : * Create mergejoin join paths by explicitly sorting both the outer and
1393 : * inner join relations on each available merge ordering.
1394 : *
1395 : * 'joinrel' is the join relation
1396 : * 'outerrel' is the outer join relation
1397 : * 'innerrel' is the inner join relation
1398 : * 'jointype' is the type of join to do
1399 : * 'extra' contains additional input values
1400 : */
1401 : static void
1402 763798 : sort_inner_and_outer(PlannerInfo *root,
1403 : RelOptInfo *joinrel,
1404 : RelOptInfo *outerrel,
1405 : RelOptInfo *innerrel,
1406 : JoinType jointype,
1407 : JoinPathExtraData *extra)
1408 : {
1409 : Path *outer_path;
1410 : Path *inner_path;
1411 763798 : Path *cheapest_partial_outer = NULL;
1412 763798 : Path *cheapest_safe_inner = NULL;
1413 : List *all_pathkeys;
1414 : ListCell *l;
1415 :
1416 : /* Nothing to do if there are no available mergejoin clauses */
1417 763798 : if (extra->mergeclause_list == NIL)
1418 122190 : return;
1419 :
1420 : /*
1421 : * We only consider the cheapest-total-cost input paths, since we are
1422 : * assuming here that a sort is required. We will consider
1423 : * cheapest-startup-cost input paths later, and only if they don't need a
1424 : * sort.
1425 : *
1426 : * This function intentionally does not consider parameterized input
1427 : * paths, except when the cheapest-total is parameterized. If we did so,
1428 : * we'd have a combinatorial explosion of mergejoin paths of dubious
1429 : * value. This interacts with decisions elsewhere that also discriminate
1430 : * against mergejoins with parameterized inputs; see comments in
1431 : * src/backend/optimizer/README.
1432 : */
1433 641608 : outer_path = outerrel->cheapest_total_path;
1434 641608 : inner_path = innerrel->cheapest_total_path;
1435 :
1436 : /*
1437 : * If either cheapest-total path is parameterized by the other rel, we
1438 : * can't use a mergejoin. (There's no use looking for alternative input
1439 : * paths, since these should already be the least-parameterized available
1440 : * paths.)
1441 : */
1442 641608 : if (PATH_PARAM_BY_REL(outer_path, innerrel) ||
1443 640716 : PATH_PARAM_BY_REL(inner_path, outerrel))
1444 1820 : return;
1445 :
1446 : /*
1447 : * If the joinrel is parallel-safe, we may be able to consider a partial
1448 : * merge join. However, we can't handle JOIN_FULL, JOIN_RIGHT and
1449 : * JOIN_RIGHT_ANTI, because they can produce false null extended rows.
1450 : * Also, the resulting path must not be parameterized.
1451 : */
1452 639788 : if (joinrel->consider_parallel &&
1453 576576 : jointype != JOIN_FULL &&
1454 493738 : jointype != JOIN_RIGHT &&
1455 492254 : jointype != JOIN_RIGHT_ANTI &&
1456 492254 : outerrel->partial_pathlist != NIL &&
1457 72902 : bms_is_empty(joinrel->lateral_relids))
1458 : {
1459 72902 : cheapest_partial_outer = (Path *) linitial(outerrel->partial_pathlist);
1460 :
1461 72902 : if (inner_path->parallel_safe)
1462 72722 : cheapest_safe_inner = inner_path;
1463 : else
1464 : cheapest_safe_inner =
1465 180 : get_cheapest_parallel_safe_total_inner(innerrel->pathlist);
1466 : }
1467 :
1468 : /*
1469 : * Each possible ordering of the available mergejoin clauses will generate
1470 : * a differently-sorted result path at essentially the same cost. We have
1471 : * no basis for choosing one over another at this level of joining, but
1472 : * some sort orders may be more useful than others for higher-level
1473 : * mergejoins, so it's worth considering multiple orderings.
1474 : *
1475 : * Actually, it's not quite true that every mergeclause ordering will
1476 : * generate a different path order, because some of the clauses may be
1477 : * partially redundant (refer to the same EquivalenceClasses). Therefore,
1478 : * what we do is convert the mergeclause list to a list of canonical
1479 : * pathkeys, and then consider different orderings of the pathkeys.
1480 : *
1481 : * Generating a path for *every* permutation of the pathkeys doesn't seem
1482 : * like a winning strategy; the cost in planning time is too high. For
1483 : * now, we generate one path for each pathkey, listing that pathkey first
1484 : * and the rest in random order. This should allow at least a one-clause
1485 : * mergejoin without re-sorting against any other possible mergejoin
1486 : * partner path. But if we've not guessed the right ordering of secondary
1487 : * keys, we may end up evaluating clauses as qpquals when they could have
1488 : * been done as mergeclauses. (In practice, it's rare that there's more
1489 : * than two or three mergeclauses, so expending a huge amount of thought
1490 : * on that is probably not worth it.)
1491 : *
1492 : * The pathkey order returned by select_outer_pathkeys_for_merge() has
1493 : * some heuristics behind it (see that function), so be sure to try it
1494 : * exactly as-is as well as making variants.
1495 : */
1496 639788 : all_pathkeys = select_outer_pathkeys_for_merge(root,
1497 : extra->mergeclause_list,
1498 : joinrel);
1499 :
1500 1358230 : foreach(l, all_pathkeys)
1501 : {
1502 718442 : PathKey *front_pathkey = (PathKey *) lfirst(l);
1503 : List *cur_mergeclauses;
1504 : List *outerkeys;
1505 : List *innerkeys;
1506 : List *merge_pathkeys;
1507 :
1508 : /* Make a pathkey list with this guy first */
1509 718442 : if (l != list_head(all_pathkeys))
1510 78654 : outerkeys = lcons(front_pathkey,
1511 : list_delete_nth_cell(list_copy(all_pathkeys),
1512 : foreach_current_index(l)));
1513 : else
1514 639788 : outerkeys = all_pathkeys; /* no work at first one... */
1515 :
1516 : /* Sort the mergeclauses into the corresponding ordering */
1517 : cur_mergeclauses =
1518 718442 : find_mergeclauses_for_outer_pathkeys(root,
1519 : outerkeys,
1520 : extra->mergeclause_list);
1521 :
1522 : /* Should have used them all... */
1523 : Assert(list_length(cur_mergeclauses) == list_length(extra->mergeclause_list));
1524 :
1525 : /* Build sort pathkeys for the inner side */
1526 718442 : innerkeys = make_inner_pathkeys_for_merge(root,
1527 : cur_mergeclauses,
1528 : outerkeys);
1529 :
1530 : /* Build pathkeys representing output sort order */
1531 718442 : merge_pathkeys = build_join_pathkeys(root, joinrel, jointype,
1532 : outerkeys);
1533 :
1534 : /*
1535 : * And now we can make the path.
1536 : *
1537 : * Note: it's possible that the cheapest paths will already be sorted
1538 : * properly. try_mergejoin_path will detect that case and suppress an
1539 : * explicit sort step, so we needn't do so here.
1540 : */
1541 718442 : try_mergejoin_path(root,
1542 : joinrel,
1543 : outer_path,
1544 : inner_path,
1545 : merge_pathkeys,
1546 : cur_mergeclauses,
1547 : outerkeys,
1548 : innerkeys,
1549 : jointype,
1550 : extra,
1551 : false);
1552 :
1553 : /*
1554 : * If we have partial outer and parallel safe inner path then try
1555 : * partial mergejoin path.
1556 : */
1557 718442 : if (cheapest_partial_outer && cheapest_safe_inner)
1558 76564 : try_partial_mergejoin_path(root,
1559 : joinrel,
1560 : cheapest_partial_outer,
1561 : cheapest_safe_inner,
1562 : merge_pathkeys,
1563 : cur_mergeclauses,
1564 : outerkeys,
1565 : innerkeys,
1566 : jointype,
1567 : extra);
1568 : }
1569 : }
1570 :
1571 : /*
1572 : * generate_mergejoin_paths
1573 : * Creates possible mergejoin paths for input outerpath.
1574 : *
1575 : * We generate mergejoins if mergejoin clauses are available. We have
1576 : * two ways to generate the inner path for a mergejoin: sort the cheapest
1577 : * inner path, or use an inner path that is already suitably ordered for the
1578 : * merge. If we have several mergeclauses, it could be that there is no inner
1579 : * path (or only a very expensive one) for the full list of mergeclauses, but
1580 : * better paths exist if we truncate the mergeclause list (thereby discarding
1581 : * some sort key requirements). So, we consider truncations of the
1582 : * mergeclause list as well as the full list. (Ideally we'd consider all
1583 : * subsets of the mergeclause list, but that seems way too expensive.)
1584 : */
1585 : static void
1586 1532094 : generate_mergejoin_paths(PlannerInfo *root,
1587 : RelOptInfo *joinrel,
1588 : RelOptInfo *innerrel,
1589 : Path *outerpath,
1590 : JoinType jointype,
1591 : JoinPathExtraData *extra,
1592 : bool useallclauses,
1593 : Path *inner_cheapest_total,
1594 : List *merge_pathkeys,
1595 : bool is_partial)
1596 : {
1597 : List *mergeclauses;
1598 : List *innersortkeys;
1599 : List *trialsortkeys;
1600 : Path *cheapest_startup_inner;
1601 : Path *cheapest_total_inner;
1602 : int num_sortkeys;
1603 : int sortkeycnt;
1604 :
1605 : /* Look for useful mergeclauses (if any) */
1606 : mergeclauses =
1607 1532094 : find_mergeclauses_for_outer_pathkeys(root,
1608 : outerpath->pathkeys,
1609 : extra->mergeclause_list);
1610 :
1611 : /*
1612 : * Done with this outer path if no chance for a mergejoin.
1613 : *
1614 : * Special corner case: for "x FULL JOIN y ON true", there will be no join
1615 : * clauses at all. Ordinarily we'd generate a clauseless nestloop path,
1616 : * but since mergejoin is our only join type that supports FULL JOIN
1617 : * without any join clauses, it's necessary to generate a clauseless
1618 : * mergejoin path instead.
1619 : */
1620 1532094 : if (mergeclauses == NIL)
1621 : {
1622 1031482 : if (jointype == JOIN_FULL)
1623 : /* okay to try for mergejoin */ ;
1624 : else
1625 1028086 : return;
1626 : }
1627 593054 : if (useallclauses &&
1628 89046 : list_length(mergeclauses) != list_length(extra->mergeclause_list))
1629 13736 : return;
1630 :
1631 : /* Compute the required ordering of the inner path */
1632 490272 : innersortkeys = make_inner_pathkeys_for_merge(root,
1633 : mergeclauses,
1634 : outerpath->pathkeys);
1635 :
1636 : /*
1637 : * Generate a mergejoin on the basis of sorting the cheapest inner. Since
1638 : * a sort will be needed, only cheapest total cost matters. (But
1639 : * try_mergejoin_path will do the right thing if inner_cheapest_total is
1640 : * already correctly sorted.)
1641 : */
1642 490272 : try_mergejoin_path(root,
1643 : joinrel,
1644 : outerpath,
1645 : inner_cheapest_total,
1646 : merge_pathkeys,
1647 : mergeclauses,
1648 : NIL,
1649 : innersortkeys,
1650 : jointype,
1651 : extra,
1652 : is_partial);
1653 :
1654 : /*
1655 : * Look for presorted inner paths that satisfy the innersortkey list ---
1656 : * or any truncation thereof, if we are allowed to build a mergejoin using
1657 : * a subset of the merge clauses. Here, we consider both cheap startup
1658 : * cost and cheap total cost.
1659 : *
1660 : * Currently we do not consider parameterized inner paths here. This
1661 : * interacts with decisions elsewhere that also discriminate against
1662 : * mergejoins with parameterized inputs; see comments in
1663 : * src/backend/optimizer/README.
1664 : *
1665 : * As we shorten the sortkey list, we should consider only paths that are
1666 : * strictly cheaper than (in particular, not the same as) any path found
1667 : * in an earlier iteration. Otherwise we'd be intentionally using fewer
1668 : * merge keys than a given path allows (treating the rest as plain
1669 : * joinquals), which is unlikely to be a good idea. Also, eliminating
1670 : * paths here on the basis of compare_path_costs is a lot cheaper than
1671 : * building the mergejoin path only to throw it away.
1672 : *
1673 : * If inner_cheapest_total is well enough sorted to have not required a
1674 : * sort in the path made above, we shouldn't make a duplicate path with
1675 : * it, either. We handle that case with the same logic that handles the
1676 : * previous consideration, by initializing the variables that track
1677 : * cheapest-so-far properly. Note that we do NOT reject
1678 : * inner_cheapest_total if we find it matches some shorter set of
1679 : * pathkeys. That case corresponds to using fewer mergekeys to avoid
1680 : * sorting inner_cheapest_total, whereas we did sort it above, so the
1681 : * plans being considered are different.
1682 : */
1683 490272 : if (pathkeys_contained_in(innersortkeys,
1684 : inner_cheapest_total->pathkeys))
1685 : {
1686 : /* inner_cheapest_total didn't require a sort */
1687 15282 : cheapest_startup_inner = inner_cheapest_total;
1688 15282 : cheapest_total_inner = inner_cheapest_total;
1689 : }
1690 : else
1691 : {
1692 : /* it did require a sort, at least for the full set of keys */
1693 474990 : cheapest_startup_inner = NULL;
1694 474990 : cheapest_total_inner = NULL;
1695 : }
1696 490272 : num_sortkeys = list_length(innersortkeys);
1697 490272 : if (num_sortkeys > 1 && !useallclauses)
1698 25542 : trialsortkeys = list_copy(innersortkeys); /* need modifiable copy */
1699 : else
1700 464730 : trialsortkeys = innersortkeys; /* won't really truncate */
1701 :
1702 931660 : for (sortkeycnt = num_sortkeys; sortkeycnt > 0; sortkeycnt--)
1703 : {
1704 : Path *innerpath;
1705 516554 : List *newclauses = NIL;
1706 :
1707 : /*
1708 : * Look for an inner path ordered well enough for the first
1709 : * 'sortkeycnt' innersortkeys. NB: trialsortkeys list is modified
1710 : * destructively, which is why we made a copy...
1711 : */
1712 516554 : trialsortkeys = list_truncate(trialsortkeys, sortkeycnt);
1713 516554 : innerpath = get_cheapest_path_for_pathkeys(innerrel->pathlist,
1714 : trialsortkeys,
1715 : NULL,
1716 : TOTAL_COST,
1717 : is_partial);
1718 516554 : if (innerpath != NULL &&
1719 25936 : (cheapest_total_inner == NULL ||
1720 25936 : compare_path_costs(innerpath, cheapest_total_inner,
1721 : TOTAL_COST) < 0))
1722 : {
1723 : /* Found a cheap (or even-cheaper) sorted path */
1724 : /* Select the right mergeclauses, if we didn't already */
1725 289814 : if (sortkeycnt < num_sortkeys)
1726 : {
1727 : newclauses =
1728 15404 : trim_mergeclauses_for_inner_pathkeys(root,
1729 : mergeclauses,
1730 : trialsortkeys);
1731 : Assert(newclauses != NIL);
1732 : }
1733 : else
1734 274410 : newclauses = mergeclauses;
1735 289814 : try_mergejoin_path(root,
1736 : joinrel,
1737 : outerpath,
1738 : innerpath,
1739 : merge_pathkeys,
1740 : newclauses,
1741 : NIL,
1742 : NIL,
1743 : jointype,
1744 : extra,
1745 : is_partial);
1746 289814 : cheapest_total_inner = innerpath;
1747 : }
1748 : /* Same on the basis of cheapest startup cost ... */
1749 516554 : innerpath = get_cheapest_path_for_pathkeys(innerrel->pathlist,
1750 : trialsortkeys,
1751 : NULL,
1752 : STARTUP_COST,
1753 : is_partial);
1754 516554 : if (innerpath != NULL &&
1755 25936 : (cheapest_startup_inner == NULL ||
1756 25936 : compare_path_costs(innerpath, cheapest_startup_inner,
1757 : STARTUP_COST) < 0))
1758 : {
1759 : /* Found a cheap (or even-cheaper) sorted path */
1760 287208 : if (innerpath != cheapest_total_inner)
1761 : {
1762 : /*
1763 : * Avoid rebuilding clause list if we already made one; saves
1764 : * memory in big join trees...
1765 : */
1766 2876 : if (newclauses == NIL)
1767 : {
1768 102 : if (sortkeycnt < num_sortkeys)
1769 : {
1770 : newclauses =
1771 0 : trim_mergeclauses_for_inner_pathkeys(root,
1772 : mergeclauses,
1773 : trialsortkeys);
1774 : Assert(newclauses != NIL);
1775 : }
1776 : else
1777 102 : newclauses = mergeclauses;
1778 : }
1779 2876 : try_mergejoin_path(root,
1780 : joinrel,
1781 : outerpath,
1782 : innerpath,
1783 : merge_pathkeys,
1784 : newclauses,
1785 : NIL,
1786 : NIL,
1787 : jointype,
1788 : extra,
1789 : is_partial);
1790 : }
1791 287208 : cheapest_startup_inner = innerpath;
1792 : }
1793 :
1794 : /*
1795 : * Don't consider truncated sortkeys if we need all clauses.
1796 : */
1797 516554 : if (useallclauses)
1798 75166 : break;
1799 : }
1800 : }
1801 :
1802 : /*
1803 : * match_unsorted_outer
1804 : * Creates possible join paths for processing a single join relation
1805 : * 'joinrel' by employing either iterative substitution or
1806 : * mergejoining on each of its possible outer paths (considering
1807 : * only outer paths that are already ordered well enough for merging).
1808 : *
1809 : * We always generate a nestloop path for each available outer path.
1810 : * In fact we may generate as many as five: one on the cheapest-total-cost
1811 : * inner path, one on the same with materialization, one on the
1812 : * cheapest-startup-cost inner path (if different), one on the
1813 : * cheapest-total inner-indexscan path (if any), and one on the
1814 : * cheapest-startup inner-indexscan path (if different).
1815 : *
1816 : * We also consider mergejoins if mergejoin clauses are available. See
1817 : * detailed comments in generate_mergejoin_paths.
1818 : *
1819 : * 'joinrel' is the join relation
1820 : * 'outerrel' is the outer join relation
1821 : * 'innerrel' is the inner join relation
1822 : * 'jointype' is the type of join to do
1823 : * 'extra' contains additional input values
1824 : */
1825 : static void
1826 763798 : match_unsorted_outer(PlannerInfo *root,
1827 : RelOptInfo *joinrel,
1828 : RelOptInfo *outerrel,
1829 : RelOptInfo *innerrel,
1830 : JoinType jointype,
1831 : JoinPathExtraData *extra)
1832 : {
1833 : bool nestjoinOK;
1834 : bool useallclauses;
1835 763798 : Path *inner_cheapest_total = innerrel->cheapest_total_path;
1836 763798 : Path *matpath = NULL;
1837 : ListCell *lc1;
1838 :
1839 : /*
1840 : * For now we do not support RIGHT_SEMI join in mergejoin or nestloop
1841 : * join.
1842 : */
1843 763798 : if (jointype == JOIN_RIGHT_SEMI)
1844 102 : return;
1845 :
1846 : /*
1847 : * Nestloop only supports inner, left, semi, and anti joins. Also, if we
1848 : * are doing a right, right-anti or full mergejoin, we must use *all* the
1849 : * mergeclauses as join clauses, else we will not have a valid plan.
1850 : * (Although these two flags are currently inverses, keep them separate
1851 : * for clarity and possible future changes.)
1852 : */
1853 763696 : switch (jointype)
1854 : {
1855 666688 : case JOIN_INNER:
1856 : case JOIN_LEFT:
1857 : case JOIN_SEMI:
1858 : case JOIN_ANTI:
1859 666688 : nestjoinOK = true;
1860 666688 : useallclauses = false;
1861 666688 : break;
1862 97008 : case JOIN_RIGHT:
1863 : case JOIN_RIGHT_ANTI:
1864 : case JOIN_FULL:
1865 97008 : nestjoinOK = false;
1866 97008 : useallclauses = true;
1867 97008 : break;
1868 0 : default:
1869 0 : elog(ERROR, "unrecognized join type: %d",
1870 : (int) jointype);
1871 : nestjoinOK = false; /* keep compiler quiet */
1872 : useallclauses = false;
1873 : break;
1874 : }
1875 :
1876 : /*
1877 : * If inner_cheapest_total is parameterized by the outer rel, ignore it;
1878 : * we will consider it below as a member of cheapest_parameterized_paths,
1879 : * but the other possibilities considered in this routine aren't usable.
1880 : *
1881 : * Furthermore, if the inner side is a unique-ified relation, we cannot
1882 : * generate any valid paths here, because the inner rel's dependency on
1883 : * the outer rel makes unique-ification meaningless.
1884 : */
1885 763696 : if (PATH_PARAM_BY_REL(inner_cheapest_total, outerrel))
1886 : {
1887 15000 : inner_cheapest_total = NULL;
1888 :
1889 15000 : if (RELATION_WAS_MADE_UNIQUE(innerrel, extra->sjinfo, jointype))
1890 36 : return;
1891 : }
1892 :
1893 763660 : if (nestjoinOK)
1894 : {
1895 : /*
1896 : * Consider materializing the cheapest inner path, unless that is
1897 : * disabled or the path in question materializes its output anyway.
1898 : */
1899 666652 : if ((extra->pgs_mask & PGS_NESTLOOP_MATERIALIZE) != 0 &&
1900 649672 : inner_cheapest_total != NULL &&
1901 649672 : !ExecMaterializesOutput(inner_cheapest_total->pathtype))
1902 : matpath = (Path *)
1903 621452 : create_material_path(innerrel, inner_cheapest_total, true);
1904 : }
1905 :
1906 2488838 : foreach(lc1, outerrel->pathlist)
1907 : {
1908 1725178 : Path *outerpath = (Path *) lfirst(lc1);
1909 : List *merge_pathkeys;
1910 :
1911 : /*
1912 : * We cannot use an outer path that is parameterized by the inner rel.
1913 : */
1914 1725178 : if (PATH_PARAM_BY_REL(outerpath, innerrel))
1915 269266 : continue;
1916 :
1917 : /*
1918 : * The result will have this sort order (even if it is implemented as
1919 : * a nestloop, and even if some of the mergeclauses are implemented by
1920 : * qpquals rather than as true mergeclauses):
1921 : */
1922 1455912 : merge_pathkeys = build_join_pathkeys(root, joinrel, jointype,
1923 : outerpath->pathkeys);
1924 :
1925 1455912 : if (nestjoinOK)
1926 : {
1927 : /*
1928 : * Consider nestloop joins using this outer path and various
1929 : * available paths for the inner relation. We consider the
1930 : * cheapest-total paths for each available parameterization of the
1931 : * inner relation, including the unparameterized case.
1932 : */
1933 : ListCell *lc2;
1934 :
1935 3271520 : foreach(lc2, innerrel->cheapest_parameterized_paths)
1936 : {
1937 1999636 : Path *innerpath = (Path *) lfirst(lc2);
1938 : Path *mpath;
1939 :
1940 1999636 : try_nestloop_path(root,
1941 : joinrel,
1942 : outerpath,
1943 : innerpath,
1944 : merge_pathkeys,
1945 : jointype,
1946 : PGS_NESTLOOP_PLAIN,
1947 : extra);
1948 :
1949 : /*
1950 : * Try generating a memoize path and see if that makes the
1951 : * nested loop any cheaper.
1952 : */
1953 1999636 : mpath = get_memoize_path(root, innerrel, outerrel,
1954 : innerpath, outerpath, jointype,
1955 : extra);
1956 1999636 : if (mpath != NULL)
1957 314628 : try_nestloop_path(root,
1958 : joinrel,
1959 : outerpath,
1960 : mpath,
1961 : merge_pathkeys,
1962 : jointype,
1963 : PGS_NESTLOOP_MEMOIZE,
1964 : extra);
1965 : }
1966 :
1967 : /* Also consider materialized form of the cheapest inner path */
1968 1271884 : if (matpath != NULL)
1969 1195020 : try_nestloop_path(root,
1970 : joinrel,
1971 : outerpath,
1972 : matpath,
1973 : merge_pathkeys,
1974 : jointype,
1975 : PGS_NESTLOOP_MATERIALIZE,
1976 : extra);
1977 : }
1978 :
1979 : /* Can't do anything else if inner rel is parameterized by outer */
1980 1455912 : if (inner_cheapest_total == NULL)
1981 17890 : continue;
1982 :
1983 : /* Generate merge join paths */
1984 1438022 : generate_mergejoin_paths(root, joinrel, innerrel, outerpath,
1985 : jointype, extra, useallclauses,
1986 : inner_cheapest_total, merge_pathkeys,
1987 : false);
1988 : }
1989 :
1990 : /*
1991 : * Consider partial nestloop and mergejoin plan if outerrel has any
1992 : * partial path and the joinrel is parallel-safe. However, we can't
1993 : * handle joins needing lateral rels, since partial paths must not be
1994 : * parameterized. Similarly, we can't handle JOIN_FULL, JOIN_RIGHT and
1995 : * JOIN_RIGHT_ANTI, because they can produce false null extended rows.
1996 : */
1997 763660 : if (joinrel->consider_parallel &&
1998 656546 : jointype != JOIN_FULL &&
1999 572036 : jointype != JOIN_RIGHT &&
2000 570534 : jointype != JOIN_RIGHT_ANTI &&
2001 570534 : outerrel->partial_pathlist != NIL &&
2002 74644 : bms_is_empty(joinrel->lateral_relids))
2003 : {
2004 74644 : if (nestjoinOK)
2005 74644 : consider_parallel_nestloop(root, joinrel, outerrel, innerrel,
2006 : jointype, extra);
2007 :
2008 : /*
2009 : * If inner_cheapest_total is NULL or non parallel-safe then find the
2010 : * cheapest total parallel safe path.
2011 : */
2012 74644 : if (inner_cheapest_total == NULL ||
2013 74224 : !inner_cheapest_total->parallel_safe)
2014 : {
2015 : inner_cheapest_total =
2016 876 : get_cheapest_parallel_safe_total_inner(innerrel->pathlist);
2017 : }
2018 :
2019 74644 : if (inner_cheapest_total)
2020 74182 : consider_parallel_mergejoin(root, joinrel, outerrel, innerrel,
2021 : jointype, extra,
2022 : inner_cheapest_total);
2023 : }
2024 : }
2025 :
2026 : /*
2027 : * consider_parallel_mergejoin
2028 : * Try to build partial paths for a joinrel by joining a partial path
2029 : * for the outer relation to a complete path for the inner relation.
2030 : *
2031 : * 'joinrel' is the join relation
2032 : * 'outerrel' is the outer join relation
2033 : * 'innerrel' is the inner join relation
2034 : * 'jointype' is the type of join to do
2035 : * 'extra' contains additional input values
2036 : * 'inner_cheapest_total' cheapest total path for innerrel
2037 : */
2038 : static void
2039 74182 : consider_parallel_mergejoin(PlannerInfo *root,
2040 : RelOptInfo *joinrel,
2041 : RelOptInfo *outerrel,
2042 : RelOptInfo *innerrel,
2043 : JoinType jointype,
2044 : JoinPathExtraData *extra,
2045 : Path *inner_cheapest_total)
2046 : {
2047 : ListCell *lc1;
2048 :
2049 : /* generate merge join path for each partial outer path */
2050 168254 : foreach(lc1, outerrel->partial_pathlist)
2051 : {
2052 94072 : Path *outerpath = (Path *) lfirst(lc1);
2053 : List *merge_pathkeys;
2054 :
2055 : /*
2056 : * Figure out what useful ordering any paths we create will have.
2057 : */
2058 94072 : merge_pathkeys = build_join_pathkeys(root, joinrel, jointype,
2059 : outerpath->pathkeys);
2060 :
2061 94072 : generate_mergejoin_paths(root, joinrel, innerrel, outerpath, jointype,
2062 : extra, false, inner_cheapest_total,
2063 : merge_pathkeys, true);
2064 : }
2065 74182 : }
2066 :
2067 : /*
2068 : * consider_parallel_nestloop
2069 : * Try to build partial paths for a joinrel by joining a partial path for the
2070 : * outer relation to a complete path for the inner relation.
2071 : *
2072 : * 'joinrel' is the join relation
2073 : * 'outerrel' is the outer join relation
2074 : * 'innerrel' is the inner join relation
2075 : * 'jointype' is the type of join to do
2076 : * 'extra' contains additional input values
2077 : */
2078 : static void
2079 74644 : consider_parallel_nestloop(PlannerInfo *root,
2080 : RelOptInfo *joinrel,
2081 : RelOptInfo *outerrel,
2082 : RelOptInfo *innerrel,
2083 : JoinType jointype,
2084 : JoinPathExtraData *extra)
2085 : {
2086 74644 : Path *inner_cheapest_total = innerrel->cheapest_total_path;
2087 74644 : Path *matpath = NULL;
2088 : ListCell *lc1;
2089 :
2090 : /*
2091 : * Consider materializing the cheapest inner path, unless: 1)
2092 : * materialization is disabled here, 2) the cheapest inner path is not
2093 : * parallel-safe, 3) the cheapest inner path is parameterized by the outer
2094 : * rel, or 4) the cheapest inner path materializes its output anyway.
2095 : */
2096 74644 : if ((extra->pgs_mask & PGS_NESTLOOP_MATERIALIZE) != 0 &&
2097 73980 : inner_cheapest_total->parallel_safe &&
2098 73698 : !PATH_PARAM_BY_REL(inner_cheapest_total, outerrel) &&
2099 73308 : !ExecMaterializesOutput(inner_cheapest_total->pathtype))
2100 : {
2101 : matpath = (Path *)
2102 73212 : create_material_path(innerrel, inner_cheapest_total, true);
2103 : Assert(matpath->parallel_safe);
2104 : }
2105 :
2106 169316 : foreach(lc1, outerrel->partial_pathlist)
2107 : {
2108 94672 : Path *outerpath = (Path *) lfirst(lc1);
2109 : List *pathkeys;
2110 : ListCell *lc2;
2111 :
2112 : /* Figure out what useful ordering any paths we create will have. */
2113 94672 : pathkeys = build_join_pathkeys(root, joinrel, jointype,
2114 : outerpath->pathkeys);
2115 :
2116 : /*
2117 : * Try the cheapest parameterized paths; only those which will produce
2118 : * an unparameterized path when joined to this outerrel will survive
2119 : * try_partial_nestloop_path. The cheapest unparameterized path is
2120 : * also in this list.
2121 : */
2122 198448 : foreach(lc2, innerrel->cheapest_parameterized_paths)
2123 : {
2124 103776 : Path *innerpath = (Path *) lfirst(lc2);
2125 : Path *mpath;
2126 :
2127 : /* Can't join to an inner path that is not parallel-safe */
2128 103776 : if (!innerpath->parallel_safe)
2129 534 : continue;
2130 :
2131 103242 : try_partial_nestloop_path(root, joinrel, outerpath, innerpath,
2132 : pathkeys, jointype,
2133 : PGS_NESTLOOP_PLAIN, extra);
2134 :
2135 : /*
2136 : * Try generating a memoize path and see if that makes the nested
2137 : * loop any cheaper.
2138 : */
2139 103242 : mpath = get_memoize_path(root, innerrel, outerrel,
2140 : innerpath, outerpath, jointype,
2141 : extra);
2142 103242 : if (mpath != NULL)
2143 5858 : try_partial_nestloop_path(root, joinrel, outerpath, mpath,
2144 : pathkeys, jointype,
2145 : PGS_NESTLOOP_MEMOIZE, extra);
2146 : }
2147 :
2148 : /* Also consider materialized form of the cheapest inner path */
2149 94672 : if (matpath != NULL)
2150 92814 : try_partial_nestloop_path(root, joinrel, outerpath, matpath,
2151 : pathkeys, jointype,
2152 : PGS_NESTLOOP_MATERIALIZE, extra);
2153 : }
2154 74644 : }
2155 :
2156 : /*
2157 : * hash_inner_and_outer
2158 : * Create hashjoin join paths by explicitly hashing both the outer and
2159 : * inner keys of each available hash clause.
2160 : *
2161 : * 'joinrel' is the join relation
2162 : * 'outerrel' is the outer join relation
2163 : * 'innerrel' is the inner join relation
2164 : * 'jointype' is the type of join to do
2165 : * 'extra' contains additional input values
2166 : */
2167 : static void
2168 776096 : hash_inner_and_outer(PlannerInfo *root,
2169 : RelOptInfo *joinrel,
2170 : RelOptInfo *outerrel,
2171 : RelOptInfo *innerrel,
2172 : JoinType jointype,
2173 : JoinPathExtraData *extra)
2174 : {
2175 776096 : bool isouterjoin = IS_OUTER_JOIN(jointype);
2176 : List *hashclauses;
2177 : ListCell *l;
2178 :
2179 : /*
2180 : * We need to build only one hashclauses list for any given pair of outer
2181 : * and inner relations; all of the hashable clauses will be used as keys.
2182 : *
2183 : * Scan the join's restrictinfo list to find hashjoinable clauses that are
2184 : * usable with this pair of sub-relations.
2185 : */
2186 776096 : hashclauses = NIL;
2187 1618464 : foreach(l, extra->restrictlist)
2188 : {
2189 842368 : RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l);
2190 :
2191 : /*
2192 : * If processing an outer join, only use its own join clauses for
2193 : * hashing. For inner joins we need not be so picky.
2194 : */
2195 842368 : if (isouterjoin && RINFO_IS_PUSHED_DOWN(restrictinfo, joinrel->relids))
2196 10368 : continue;
2197 :
2198 832000 : if (!restrictinfo->can_join ||
2199 751576 : restrictinfo->hashjoinoperator == InvalidOid)
2200 98720 : continue; /* not hashjoinable */
2201 :
2202 : /*
2203 : * Check if clause has the form "outer op inner" or "inner op outer".
2204 : */
2205 733280 : if (!clause_sides_match_join(restrictinfo, outerrel->relids,
2206 : innerrel->relids))
2207 216 : continue; /* no good for these input relations */
2208 :
2209 : /*
2210 : * If clause has the form "inner op outer", check if its operator has
2211 : * valid commutator. This is necessary because hashclauses in this
2212 : * form will get commuted in createplan.c to put the outer var on the
2213 : * left (see get_switched_clauses). This probably shouldn't ever
2214 : * fail, since hashable operators ought to have commutators, but be
2215 : * paranoid.
2216 : *
2217 : * The clause being hashjoinable indicates that it's an OpExpr.
2218 : */
2219 1099596 : if (!restrictinfo->outer_is_left &&
2220 366532 : !OidIsValid(get_commutator(castNode(OpExpr, restrictinfo->clause)->opno)))
2221 6 : continue;
2222 :
2223 733058 : hashclauses = lappend(hashclauses, restrictinfo);
2224 : }
2225 :
2226 : /* If we found any usable hashclauses, make paths */
2227 776096 : if (hashclauses)
2228 : {
2229 : /*
2230 : * We consider both the cheapest-total-cost and cheapest-startup-cost
2231 : * outer paths. There's no need to consider any but the
2232 : * cheapest-total-cost inner path, however.
2233 : */
2234 653586 : Path *cheapest_startup_outer = outerrel->cheapest_startup_path;
2235 653586 : Path *cheapest_total_outer = outerrel->cheapest_total_path;
2236 653586 : Path *cheapest_total_inner = innerrel->cheapest_total_path;
2237 : ListCell *lc1;
2238 : ListCell *lc2;
2239 :
2240 : /*
2241 : * If either cheapest-total path is parameterized by the other rel, we
2242 : * can't use a hashjoin. (There's no use looking for alternative
2243 : * input paths, since these should already be the least-parameterized
2244 : * available paths.)
2245 : */
2246 653586 : if (PATH_PARAM_BY_REL(cheapest_total_outer, innerrel) ||
2247 652682 : PATH_PARAM_BY_REL(cheapest_total_inner, outerrel))
2248 1808 : return;
2249 :
2250 : /*
2251 : * Consider the cheapest startup outer together with the cheapest
2252 : * total inner, and then consider pairings of cheapest-total paths
2253 : * including parameterized ones. There is no use in generating
2254 : * parameterized paths on the basis of possibly cheap startup cost, so
2255 : * this is sufficient.
2256 : */
2257 651778 : if (cheapest_startup_outer != NULL)
2258 649890 : try_hashjoin_path(root,
2259 : joinrel,
2260 : cheapest_startup_outer,
2261 : cheapest_total_inner,
2262 : hashclauses,
2263 : jointype,
2264 : extra);
2265 :
2266 1627742 : foreach(lc1, outerrel->cheapest_parameterized_paths)
2267 : {
2268 975964 : Path *outerpath = (Path *) lfirst(lc1);
2269 :
2270 : /*
2271 : * We cannot use an outer path that is parameterized by the inner
2272 : * rel.
2273 : */
2274 975964 : if (PATH_PARAM_BY_REL(outerpath, innerrel))
2275 260704 : continue;
2276 :
2277 1806914 : foreach(lc2, innerrel->cheapest_parameterized_paths)
2278 : {
2279 1091654 : Path *innerpath = (Path *) lfirst(lc2);
2280 :
2281 : /*
2282 : * We cannot use an inner path that is parameterized by the
2283 : * outer rel, either.
2284 : */
2285 1091654 : if (PATH_PARAM_BY_REL(innerpath, outerrel))
2286 296808 : continue;
2287 :
2288 794846 : if (outerpath == cheapest_startup_outer &&
2289 : innerpath == cheapest_total_inner)
2290 563742 : continue; /* already tried it */
2291 :
2292 231104 : try_hashjoin_path(root,
2293 : joinrel,
2294 : outerpath,
2295 : innerpath,
2296 : hashclauses,
2297 : jointype,
2298 : extra);
2299 : }
2300 : }
2301 :
2302 : /*
2303 : * If the joinrel is parallel-safe, we may be able to consider a
2304 : * partial hash join.
2305 : *
2306 : * However, we can't handle JOIN_RIGHT_SEMI, because the hash table is
2307 : * either a shared hash table or a private hash table per backend. In
2308 : * the shared case, there is no concurrency protection for the match
2309 : * flags, so multiple workers could inspect and set the flags
2310 : * concurrently, potentially producing incorrect results. In the
2311 : * private case, each worker has its own copy of the hash table, so no
2312 : * single process has all the match flags.
2313 : *
2314 : * Also, the resulting path must not be parameterized.
2315 : */
2316 651778 : if (joinrel->consider_parallel &&
2317 585730 : jointype != JOIN_RIGHT_SEMI &&
2318 585730 : outerrel->partial_pathlist != NIL &&
2319 76862 : bms_is_empty(joinrel->lateral_relids))
2320 : {
2321 : Path *cheapest_partial_outer;
2322 76862 : Path *cheapest_partial_inner = NULL;
2323 76862 : Path *cheapest_safe_inner = NULL;
2324 :
2325 76862 : cheapest_partial_outer =
2326 76862 : (Path *) linitial(outerrel->partial_pathlist);
2327 :
2328 : /*
2329 : * Can we use a partial inner plan too, so that we can build a
2330 : * shared hash table in parallel?
2331 : */
2332 76862 : if (innerrel->partial_pathlist != NIL &&
2333 : enable_parallel_hash)
2334 : {
2335 75186 : cheapest_partial_inner =
2336 75186 : (Path *) linitial(innerrel->partial_pathlist);
2337 75186 : try_partial_hashjoin_path(root, joinrel,
2338 : cheapest_partial_outer,
2339 : cheapest_partial_inner,
2340 : hashclauses, jointype, extra,
2341 : true /* parallel_hash */ );
2342 : }
2343 :
2344 : /*
2345 : * Normally, given that the joinrel is parallel-safe, the cheapest
2346 : * total inner path will also be parallel-safe, but if not, we'll
2347 : * have to search for the cheapest safe, unparameterized inner
2348 : * path. If full, right, or right-anti join, we can't use
2349 : * parallelism (building the hash table in each backend) because
2350 : * no one process has all the match bits.
2351 : */
2352 76862 : if (jointype == JOIN_FULL ||
2353 73046 : jointype == JOIN_RIGHT ||
2354 : jointype == JOIN_RIGHT_ANTI)
2355 4146 : cheapest_safe_inner = NULL;
2356 72716 : else if (cheapest_total_inner->parallel_safe)
2357 72404 : cheapest_safe_inner = cheapest_total_inner;
2358 : else
2359 : cheapest_safe_inner =
2360 312 : get_cheapest_parallel_safe_total_inner(innerrel->pathlist);
2361 :
2362 76862 : if (cheapest_safe_inner != NULL)
2363 72674 : try_partial_hashjoin_path(root, joinrel,
2364 : cheapest_partial_outer,
2365 : cheapest_safe_inner,
2366 : hashclauses, jointype, extra,
2367 : false /* parallel_hash */ );
2368 : }
2369 : }
2370 : }
2371 :
2372 : /*
2373 : * select_mergejoin_clauses
2374 : * Select mergejoin clauses that are usable for a particular join.
2375 : * Returns a list of RestrictInfo nodes for those clauses.
2376 : *
2377 : * *mergejoin_allowed is normally set to true, but it is set to false if
2378 : * this is a right-semi join, or this is a right/right-anti/full join and
2379 : * there are nonmergejoinable join clauses. The executor's mergejoin
2380 : * machinery cannot handle such cases, so we have to avoid generating a
2381 : * mergejoin plan. (Note that this flag does NOT consider whether there are
2382 : * actually any mergejoinable clauses. This is correct because in some
2383 : * cases we need to build a clauseless mergejoin. Simply returning NIL is
2384 : * therefore not enough to distinguish safe from unsafe cases.)
2385 : *
2386 : * We also mark each selected RestrictInfo to show which side is currently
2387 : * being considered as outer. These are transient markings that are only
2388 : * good for the duration of the current add_paths_to_joinrel() call!
2389 : *
2390 : * We examine each restrictinfo clause known for the join to see
2391 : * if it is mergejoinable and involves vars from the two sub-relations
2392 : * currently of interest.
2393 : */
2394 : static List *
2395 777496 : select_mergejoin_clauses(PlannerInfo *root,
2396 : RelOptInfo *joinrel,
2397 : RelOptInfo *outerrel,
2398 : RelOptInfo *innerrel,
2399 : List *restrictlist,
2400 : JoinType jointype,
2401 : bool *mergejoin_allowed)
2402 : {
2403 777496 : List *result_list = NIL;
2404 777496 : bool isouterjoin = IS_OUTER_JOIN(jointype);
2405 777496 : bool have_nonmergeable_joinclause = false;
2406 : ListCell *l;
2407 :
2408 : /*
2409 : * For now we do not support RIGHT_SEMI join in mergejoin: the benefit of
2410 : * swapping inputs tends to be small here.
2411 : */
2412 777496 : if (jointype == JOIN_RIGHT_SEMI)
2413 : {
2414 7550 : *mergejoin_allowed = false;
2415 7550 : return NIL;
2416 : }
2417 :
2418 1607444 : foreach(l, restrictlist)
2419 : {
2420 837498 : RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l);
2421 :
2422 : /*
2423 : * If processing an outer join, only use its own join clauses in the
2424 : * merge. For inner joins we can use pushed-down clauses too. (Note:
2425 : * we don't set have_nonmergeable_joinclause here because pushed-down
2426 : * clauses will become otherquals not joinquals.)
2427 : */
2428 837498 : if (isouterjoin && RINFO_IS_PUSHED_DOWN(restrictinfo, joinrel->relids))
2429 10392 : continue;
2430 :
2431 : /* Check that clause is a mergeable operator clause */
2432 827106 : if (!restrictinfo->can_join ||
2433 746700 : restrictinfo->mergeopfamilies == NIL)
2434 : {
2435 : /*
2436 : * The executor can handle extra joinquals that are constants, but
2437 : * not anything else, when doing right/right-anti/full merge join.
2438 : * (The reason to support constants is so we can do FULL JOIN ON
2439 : * FALSE.)
2440 : */
2441 97236 : if (!restrictinfo->clause || !IsA(restrictinfo->clause, Const))
2442 86908 : have_nonmergeable_joinclause = true;
2443 97236 : continue; /* not mergejoinable */
2444 : }
2445 :
2446 : /*
2447 : * Check if clause has the form "outer op inner" or "inner op outer".
2448 : */
2449 729870 : if (!clause_sides_match_join(restrictinfo, outerrel->relids,
2450 : innerrel->relids))
2451 : {
2452 1008 : have_nonmergeable_joinclause = true;
2453 1008 : continue; /* no good for these input relations */
2454 : }
2455 :
2456 : /*
2457 : * If clause has the form "inner op outer", check if its operator has
2458 : * valid commutator. This is necessary because mergejoin clauses in
2459 : * this form will get commuted in createplan.c to put the outer var on
2460 : * the left (see get_switched_clauses). This probably shouldn't ever
2461 : * fail, since mergejoinable operators ought to have commutators, but
2462 : * be paranoid.
2463 : *
2464 : * The clause being mergejoinable indicates that it's an OpExpr.
2465 : */
2466 1090346 : if (!restrictinfo->outer_is_left &&
2467 361484 : !OidIsValid(get_commutator(castNode(OpExpr, restrictinfo->clause)->opno)))
2468 : {
2469 36 : have_nonmergeable_joinclause = true;
2470 36 : continue;
2471 : }
2472 :
2473 : /*
2474 : * Insist that each side have a non-redundant eclass. This
2475 : * restriction is needed because various bits of the planner expect
2476 : * that each clause in a merge be associable with some pathkey in a
2477 : * canonical pathkey list, but redundant eclasses can't appear in
2478 : * canonical sort orderings. (XXX it might be worth relaxing this,
2479 : * but not enough time to address it for 8.3.)
2480 : */
2481 728826 : update_mergeclause_eclasses(root, restrictinfo);
2482 :
2483 728826 : if (EC_MUST_BE_REDUNDANT(restrictinfo->left_ec) ||
2484 728778 : EC_MUST_BE_REDUNDANT(restrictinfo->right_ec))
2485 : {
2486 128 : have_nonmergeable_joinclause = true;
2487 128 : continue; /* can't handle redundant eclasses */
2488 : }
2489 :
2490 728698 : result_list = lappend(result_list, restrictinfo);
2491 : }
2492 :
2493 : /*
2494 : * Report whether mergejoin is allowed (see comment at top of function).
2495 : */
2496 769946 : switch (jointype)
2497 : {
2498 106830 : case JOIN_RIGHT:
2499 : case JOIN_RIGHT_ANTI:
2500 : case JOIN_FULL:
2501 106830 : *mergejoin_allowed = !have_nonmergeable_joinclause;
2502 106830 : break;
2503 663116 : default:
2504 663116 : *mergejoin_allowed = true;
2505 663116 : break;
2506 : }
2507 :
2508 769946 : return result_list;
2509 : }
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