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 627972 : 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 627972 : JoinType save_jointype = jointype;
132 : JoinPathExtraData extra;
133 627972 : 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 627972 : if (joinrel->reloptkind == RELOPT_OTHER_JOINREL)
145 54278 : joinrelids = joinrel->top_parent_relids;
146 : else
147 573694 : joinrelids = joinrel->relids;
148 :
149 627972 : extra.restrictlist = restrictlist;
150 627972 : extra.mergeclause_list = NIL;
151 627972 : extra.sjinfo = sjinfo;
152 627972 : extra.param_source_rels = NULL;
153 627972 : 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 627972 : if (join_path_setup_hook)
178 154676 : 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 627972 : switch (jointype)
201 : {
202 5934 : case JOIN_SEMI:
203 5934 : extra.inner_unique = false; /* well, unproven */
204 5934 : break;
205 4794 : case JOIN_UNIQUE_INNER:
206 9588 : extra.inner_unique = bms_is_subset(sjinfo->min_lefthand,
207 4794 : outerrel->relids);
208 4794 : break;
209 4794 : case JOIN_UNIQUE_OUTER:
210 4794 : extra.inner_unique = innerrel_is_unique(root,
211 : joinrel->relids,
212 : outerrel->relids,
213 : innerrel,
214 : JOIN_INNER,
215 : restrictlist,
216 : false);
217 4794 : break;
218 612450 : default:
219 612450 : extra.inner_unique = innerrel_is_unique(root,
220 : joinrel->relids,
221 : outerrel->relids,
222 : innerrel,
223 : jointype,
224 : restrictlist,
225 : false);
226 612450 : break;
227 : }
228 :
229 : /*
230 : * If the outer or inner relation has been unique-ified, handle as a plain
231 : * inner join.
232 : */
233 627972 : if (jointype == JOIN_UNIQUE_OUTER || jointype == JOIN_UNIQUE_INNER)
234 9588 : 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 627972 : if ((extra.pgs_mask & PGS_MERGEJOIN_ANY) != 0 || jointype == JOIN_FULL)
243 553686 : 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 627972 : if (jointype == JOIN_SEMI || jointype == JOIN_ANTI || extra.inner_unique)
256 183397 : 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 1150274 : foreach(lc, root->join_info_list)
275 : {
276 522302 : 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 522302 : if (bms_overlap(joinrelids, sjinfo2->min_righthand) &&
286 345824 : !bms_overlap(joinrelids, sjinfo2->min_lefthand))
287 15260 : extra.param_source_rels = bms_join(extra.param_source_rels,
288 15260 : bms_difference(root->all_baserels,
289 15260 : sjinfo2->min_righthand));
290 :
291 : /* full joins constrain both sides symmetrically */
292 526236 : if (sjinfo2->jointype == JOIN_FULL &&
293 3934 : bms_overlap(joinrelids, sjinfo2->min_lefthand) &&
294 3898 : !bms_overlap(joinrelids, sjinfo2->min_righthand))
295 536 : extra.param_source_rels = bms_join(extra.param_source_rels,
296 536 : bms_difference(root->all_baserels,
297 536 : 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 1255944 : extra.param_source_rels = bms_add_members(extra.param_source_rels,
308 627972 : 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 627972 : if (mergejoin_allowed)
315 616428 : 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 627972 : if (mergejoin_allowed)
327 616428 : 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 627972 : if ((extra.pgs_mask & PGS_HASHJOIN) != 0 || jointype == JOIN_FULL)
354 560369 : 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 627972 : if ((extra.pgs_mask & PGS_FOREIGNJOIN) != 0 && joinrel->fdwroutine &&
363 1362 : joinrel->fdwroutine->GetForeignJoinPaths)
364 1360 : 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 627972 : if (set_join_pathlist_hook)
380 0 : set_join_pathlist_hook(root, joinrel, outerrel, innerrel,
381 : save_jointype, &extra);
382 627972 : }
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 248131 : 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 291216 : return (bms_overlap(inner_paramrels, outerrelids) &&
409 43085 : 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 277551 : 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 277551 : *param_exprs = NIL;
486 277551 : *operators = NIL;
487 277551 : *binary_mode = false;
488 :
489 : /* Add join clauses from param_info to the hash key */
490 277551 : if (param_info != NULL)
491 : {
492 277551 : List *clauses = param_info->ppi_clauses;
493 :
494 521124 : foreach(lc, clauses)
495 : {
496 301292 : RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
497 : OpExpr *opexpr;
498 : Node *expr;
499 : Oid hasheqoperator;
500 :
501 301292 : 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 301292 : if (!IsA(opexpr, OpExpr) || list_length(opexpr->args) != 2 ||
508 289244 : !clause_sides_match_join(rinfo, outerrel->relids,
509 : innerrel->relids))
510 : {
511 57659 : list_free(*operators);
512 57659 : list_free(*param_exprs);
513 57719 : return false;
514 : }
515 :
516 243633 : if (rinfo->outer_is_left)
517 : {
518 138043 : expr = (Node *) linitial(opexpr->args);
519 138043 : hasheqoperator = rinfo->left_hasheqoperator;
520 : }
521 : else
522 : {
523 105590 : expr = (Node *) lsecond(opexpr->args);
524 105590 : hasheqoperator = rinfo->right_hasheqoperator;
525 : }
526 :
527 : /* can't do memoize if we can't hash the outer type */
528 243633 : if (!OidIsValid(hasheqoperator))
529 : {
530 60 : list_free(*operators);
531 60 : list_free(*param_exprs);
532 60 : 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 243573 : if (!list_member(*param_exprs, expr))
541 : {
542 243569 : *operators = lappend_oid(*operators, hasheqoperator);
543 243569 : *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 243573 : if (!OidIsValid(rinfo->hashjoinoperator))
558 747 : *binary_mode = true;
559 : }
560 : }
561 :
562 : /* Now add any lateral vars to the cache key too */
563 219832 : lateral_vars = list_concat(ph_lateral_vars, innerrel->lateral_vars);
564 225420 : foreach(lc, lateral_vars)
565 : {
566 6352 : Node *expr = (Node *) lfirst(lc);
567 : TypeCacheEntry *typentry;
568 :
569 : /* Reject if there are any volatile functions in lateral vars */
570 6352 : if (contain_volatile_functions(expr))
571 : {
572 0 : list_free(*operators);
573 0 : list_free(*param_exprs);
574 764 : return false;
575 : }
576 :
577 6352 : 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 6352 : if (!OidIsValid(typentry->hash_proc) || !OidIsValid(typentry->eq_opr))
582 : {
583 764 : list_free(*operators);
584 764 : list_free(*param_exprs);
585 764 : 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 5588 : if (!list_member(*param_exprs, expr))
594 : {
595 5262 : *operators = lappend_oid(*operators, typentry->eq_opr);
596 5262 : *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 5588 : *binary_mode = true;
609 : }
610 :
611 : /* We're okay to use memoize */
612 219068 : 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 1069732 : extract_lateral_vars_from_PHVs(PlannerInfo *root, Relids innerrelids)
622 : {
623 1069732 : List *ph_lateral_vars = NIL;
624 : ListCell *lc;
625 :
626 : /* Nothing would be found if the query contains no LATERAL RTEs */
627 1069732 : if (!root->hasLateralRTEs)
628 1024343 : 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 45389 : if (bms_membership(innerrelids) == BMS_MULTIPLE)
635 18515 : return NIL;
636 :
637 28796 : foreach(lc, root->placeholder_list)
638 : {
639 1922 : PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(lc);
640 : List *vars;
641 : ListCell *cell;
642 :
643 : /* PHV is uninteresting if no lateral refs */
644 1922 : if (phinfo->ph_lateral == NULL)
645 1102 : continue;
646 :
647 : /* PHV is uninteresting if not due to be evaluated at innerrelids */
648 820 : if (!bms_equal(phinfo->ph_eval_at, innerrelids))
649 654 : 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 : */
658 166 : if (!bms_overlap(pull_varnos(root, (Node *) phinfo->ph_var->phexpr),
659 : innerrelids))
660 : {
661 158 : ph_lateral_vars = lappend(ph_lateral_vars, phinfo->ph_var->phexpr);
662 158 : continue;
663 : }
664 :
665 : /* Fetch Vars and PHVs of lateral references within PlaceHolderVars */
666 8 : vars = pull_vars_of_level((Node *) phinfo->ph_var->phexpr, 0);
667 24 : foreach(cell, vars)
668 : {
669 16 : Node *node = (Node *) lfirst(cell);
670 :
671 16 : if (IsA(node, Var))
672 : {
673 8 : Var *var = (Var *) node;
674 :
675 : Assert(var->varlevelsup == 0);
676 :
677 8 : if (bms_is_member(var->varno, phinfo->ph_lateral))
678 0 : ph_lateral_vars = lappend(ph_lateral_vars, node);
679 : }
680 8 : else if (IsA(node, PlaceHolderVar))
681 : {
682 8 : PlaceHolderVar *phv = (PlaceHolderVar *) node;
683 :
684 : Assert(phv->phlevelsup == 0);
685 :
686 8 : if (bms_is_subset(find_placeholder_info(root, phv)->ph_eval_at,
687 8 : phinfo->ph_lateral))
688 8 : ph_lateral_vars = lappend(ph_lateral_vars, node);
689 : }
690 : else
691 : Assert(false);
692 : }
693 :
694 8 : list_free(vars);
695 : }
696 :
697 26874 : 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 1668719 : 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 1668719 : if ((extra->pgs_mask & PGS_NESTLOOP_MEMOIZE) == 0)
725 163984 : 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 1504735 : if (outer_path->parent->rows < 2)
734 435003 : 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 1069732 : 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 1069732 : if ((inner_path->param_info == NULL ||
749 382897 : inner_path->param_info->ppi_clauses == NIL) &&
750 712564 : innerrel->lateral_vars == NIL &&
751 : ph_lateral_vars == NIL)
752 707752 : 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 361980 : if ((jointype == JOIN_SEMI || jointype == JOIN_ANTI) &&
769 10362 : !extra->inner_unique)
770 4531 : 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 357449 : if (extra->inner_unique)
795 : {
796 : Bitmapset *ppi_serials;
797 :
798 215655 : if (inner_path->param_info == NULL)
799 0 : return NULL;
800 :
801 215655 : ppi_serials = inner_path->param_info->ppi_serials;
802 :
803 513825 : foreach_node(RestrictInfo, rinfo, extra->restrictlist)
804 : {
805 242101 : if (!bms_is_member(rinfo->rinfo_serial, ppi_serials))
806 79793 : 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 277656 : if (contain_volatile_functions((Node *) innerrel->reltarget))
816 0 : return NULL;
817 :
818 458071 : foreach(lc, innerrel->baserestrictinfo)
819 : {
820 180519 : RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
821 :
822 180519 : if (contain_volatile_functions((Node *) rinfo))
823 104 : 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 277552 : if (inner_path->param_info != NULL)
833 : {
834 599967 : foreach(lc, inner_path->param_info->ppi_clauses)
835 : {
836 322416 : RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
837 :
838 322416 : if (contain_volatile_functions((Node *) rinfo))
839 1 : return NULL;
840 : }
841 : }
842 :
843 : /* Check if we have hash ops for each parameter to the path */
844 277551 : if (paraminfo_get_equal_hashops(root,
845 : inner_path->param_info,
846 277551 : 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 219068 : return (Path *) create_memoize_path(root,
855 : innerrel,
856 : inner_path,
857 : param_exprs,
858 : hash_operators,
859 219068 : extra->inner_unique,
860 : binary_mode,
861 : outer_path->rows);
862 : }
863 :
864 58483 : 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 2661282 : 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 2661282 : RelOptInfo *innerrel = inner_path->parent;
885 2661282 : RelOptInfo *outerrel = outer_path->parent;
886 : Relids innerrelids;
887 : Relids outerrelids;
888 2661282 : Relids inner_paramrels = PATH_REQ_OUTER(inner_path);
889 2661282 : 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 3114747 : if (extra->sjinfo->ojrelid != 0 &&
898 906930 : (bms_is_member(extra->sjinfo->ojrelid, inner_paramrels) ||
899 453465 : bms_is_member(extra->sjinfo->ojrelid, outer_paramrels)))
900 244281 : 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 2661182 : if (innerrel->top_parent_relids)
910 134037 : innerrelids = innerrel->top_parent_relids;
911 : else
912 2527145 : innerrelids = innerrel->relids;
913 :
914 2661182 : if (outerrel->top_parent_relids)
915 134037 : outerrelids = outerrel->top_parent_relids;
916 : else
917 2527145 : 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 2661182 : required_outer = calc_nestloop_required_outer(outerrelids, outer_paramrels,
925 : innerrelids, inner_paramrels);
926 2661182 : if (required_outer &&
927 287101 : !bms_overlap(required_outer, extra->param_source_rels) &&
928 248131 : !allow_star_schema_join(root, outerrelids, inner_paramrels))
929 : {
930 : /* Waste no memory when we reject a path here */
931 244181 : bms_free(required_outer);
932 244181 : 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 2417001 : if (PATH_PARAM_BY_PARENT(inner_path, outer_path->parent) &&
946 10645 : !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 2417001 : initial_cost_nestloop(root, &workspace, jointype,
962 : nestloop_subtype | PGS_CONSIDER_NONPARTIAL,
963 : outer_path, inner_path, extra);
964 :
965 2417001 : if (add_path_precheck(joinrel, workspace.disabled_nodes,
966 : workspace.startup_cost, workspace.total_cost,
967 : pathkeys, required_outer))
968 : {
969 1111258 : add_path(joinrel, (Path *)
970 1111258 : 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 1305743 : 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 157787 : 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 157787 : if (inner_path->param_info != NULL)
1014 : {
1015 12346 : Relids inner_paramrels = inner_path->param_info->ppi_req_outer;
1016 12346 : 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 12346 : if (outerrel->top_parent_relids)
1025 8708 : outerrelids = outerrel->top_parent_relids;
1026 : else
1027 3638 : outerrelids = outerrel->relids;
1028 :
1029 12346 : if (!bms_is_subset(inner_paramrels, outerrelids))
1030 119493 : 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 156610 : if (PATH_PARAM_BY_PARENT(inner_path, outer_path->parent) &&
1041 7920 : !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 156610 : initial_cost_nestloop(root, &workspace, jointype, nestloop_subtype,
1049 : outer_path, inner_path, extra);
1050 156610 : if (!add_partial_path_precheck(joinrel, workspace.disabled_nodes,
1051 : workspace.startup_cost,
1052 : workspace.total_cost, pathkeys))
1053 118316 : return;
1054 :
1055 : /* Might be good enough to be worth trying, so let's try it. */
1056 38294 : add_partial_path(joinrel, (Path *)
1057 38294 : create_nestloop_path(root,
1058 : joinrel,
1059 : jointype,
1060 : &workspace,
1061 : extra,
1062 : outer_path,
1063 : inner_path,
1064 : extra->restrictlist,
1065 : pathkeys,
1066 : NULL));
1067 : }
1068 :
1069 : /*
1070 : * try_mergejoin_path
1071 : * Consider a merge join path; if it appears useful, push it into
1072 : * the joinrel's pathlist via add_path().
1073 : */
1074 : static void
1075 1093223 : try_mergejoin_path(PlannerInfo *root,
1076 : RelOptInfo *joinrel,
1077 : Path *outer_path,
1078 : Path *inner_path,
1079 : List *pathkeys,
1080 : List *mergeclauses,
1081 : List *outersortkeys,
1082 : List *innersortkeys,
1083 : JoinType jointype,
1084 : JoinPathExtraData *extra,
1085 : bool is_partial)
1086 : {
1087 : Relids required_outer;
1088 1093223 : int outer_presorted_keys = 0;
1089 : JoinCostWorkspace workspace;
1090 :
1091 1093223 : if (is_partial)
1092 : {
1093 16441 : try_partial_mergejoin_path(root,
1094 : joinrel,
1095 : outer_path,
1096 : inner_path,
1097 : pathkeys,
1098 : mergeclauses,
1099 : outersortkeys,
1100 : innersortkeys,
1101 : jointype,
1102 : extra);
1103 45695 : return;
1104 : }
1105 :
1106 : /*
1107 : * If we are forming an outer join at this join, it's nonsensical to use
1108 : * an input path that uses the outer join as part of its parameterization.
1109 : * (This can happen despite our join order restrictions, since those apply
1110 : * to what is in an input relation not what its parameters are.)
1111 : */
1112 1326746 : if (extra->sjinfo->ojrelid != 0 &&
1113 499928 : (bms_is_member(extra->sjinfo->ojrelid, PATH_REQ_OUTER(inner_path)) ||
1114 249964 : bms_is_member(extra->sjinfo->ojrelid, PATH_REQ_OUTER(outer_path))))
1115 10 : return;
1116 :
1117 : /*
1118 : * Check to see if proposed path is still parameterized, and reject if the
1119 : * parameterization wouldn't be sensible.
1120 : */
1121 1076772 : required_outer = calc_non_nestloop_required_outer(outer_path,
1122 : inner_path);
1123 1076772 : if (required_outer &&
1124 34859 : !bms_overlap(required_outer, extra->param_source_rels))
1125 : {
1126 : /* Waste no memory when we reject a path here */
1127 29244 : bms_free(required_outer);
1128 29244 : return;
1129 : }
1130 :
1131 : /*
1132 : * If the given paths are already well enough ordered, we can skip doing
1133 : * an explicit sort.
1134 : *
1135 : * We need to determine the number of presorted keys of the outer path to
1136 : * decide whether explicit incremental sort can be applied when
1137 : * outersortkeys is not NIL. We do not need to do the same for the inner
1138 : * path though, as incremental sort currently does not support
1139 : * mark/restore.
1140 : */
1141 1577839 : if (outersortkeys &&
1142 530311 : pathkeys_count_contained_in(outersortkeys, outer_path->pathkeys,
1143 : &outer_presorted_keys))
1144 13376 : outersortkeys = NIL;
1145 1898863 : if (innersortkeys &&
1146 851335 : pathkeys_contained_in(innersortkeys, inner_path->pathkeys))
1147 23001 : innersortkeys = NIL;
1148 :
1149 : /*
1150 : * See comments in try_nestloop_path().
1151 : */
1152 1047528 : initial_cost_mergejoin(root, &workspace, jointype, mergeclauses,
1153 : outer_path, inner_path,
1154 : outersortkeys, innersortkeys,
1155 : outer_presorted_keys,
1156 : extra);
1157 :
1158 1047528 : if (add_path_precheck(joinrel, workspace.disabled_nodes,
1159 : workspace.startup_cost, workspace.total_cost,
1160 : pathkeys, required_outer))
1161 : {
1162 298327 : add_path(joinrel, (Path *)
1163 298327 : create_mergejoin_path(root,
1164 : joinrel,
1165 : jointype,
1166 : &workspace,
1167 : extra,
1168 : outer_path,
1169 : inner_path,
1170 : extra->restrictlist,
1171 : pathkeys,
1172 : required_outer,
1173 : mergeclauses,
1174 : outersortkeys,
1175 : innersortkeys,
1176 : outer_presorted_keys));
1177 : }
1178 : else
1179 : {
1180 : /* Waste no memory when we reject a path here */
1181 749201 : bms_free(required_outer);
1182 : }
1183 : }
1184 :
1185 : /*
1186 : * try_partial_mergejoin_path
1187 : * Consider a partial merge join path; if it appears useful, push it into
1188 : * the joinrel's pathlist via add_partial_path().
1189 : */
1190 : static void
1191 71677 : try_partial_mergejoin_path(PlannerInfo *root,
1192 : RelOptInfo *joinrel,
1193 : Path *outer_path,
1194 : Path *inner_path,
1195 : List *pathkeys,
1196 : List *mergeclauses,
1197 : List *outersortkeys,
1198 : List *innersortkeys,
1199 : JoinType jointype,
1200 : JoinPathExtraData *extra)
1201 : {
1202 71677 : int outer_presorted_keys = 0;
1203 : JoinCostWorkspace workspace;
1204 :
1205 : /*
1206 : * See comments in try_partial_hashjoin_path().
1207 : */
1208 : Assert(bms_is_empty(joinrel->lateral_relids));
1209 : Assert(bms_is_empty(PATH_REQ_OUTER(outer_path)));
1210 71677 : if (!bms_is_empty(PATH_REQ_OUTER(inner_path)))
1211 24475 : return;
1212 :
1213 : /*
1214 : * If the given paths are already well enough ordered, we can skip doing
1215 : * an explicit sort.
1216 : *
1217 : * We need to determine the number of presorted keys of the outer path to
1218 : * decide whether explicit incremental sort can be applied when
1219 : * outersortkeys is not NIL. We do not need to do the same for the inner
1220 : * path though, as incremental sort currently does not support
1221 : * mark/restore.
1222 : */
1223 126913 : if (outersortkeys &&
1224 55236 : pathkeys_count_contained_in(outersortkeys, outer_path->pathkeys,
1225 : &outer_presorted_keys))
1226 135 : outersortkeys = NIL;
1227 141210 : if (innersortkeys &&
1228 69533 : pathkeys_contained_in(innersortkeys, inner_path->pathkeys))
1229 450 : innersortkeys = NIL;
1230 :
1231 : /*
1232 : * See comments in try_partial_nestloop_path().
1233 : */
1234 71677 : initial_cost_mergejoin(root, &workspace, jointype, mergeclauses,
1235 : outer_path, inner_path,
1236 : outersortkeys, innersortkeys,
1237 : outer_presorted_keys,
1238 : extra);
1239 :
1240 71677 : if (!add_partial_path_precheck(joinrel, workspace.disabled_nodes,
1241 : workspace.startup_cost,
1242 : workspace.total_cost, pathkeys))
1243 24475 : return;
1244 :
1245 : /* Might be good enough to be worth trying, so let's try it. */
1246 47202 : add_partial_path(joinrel, (Path *)
1247 47202 : create_mergejoin_path(root,
1248 : joinrel,
1249 : jointype,
1250 : &workspace,
1251 : extra,
1252 : outer_path,
1253 : inner_path,
1254 : extra->restrictlist,
1255 : pathkeys,
1256 : NULL,
1257 : mergeclauses,
1258 : outersortkeys,
1259 : innersortkeys,
1260 : outer_presorted_keys));
1261 : }
1262 :
1263 : /*
1264 : * try_hashjoin_path
1265 : * Consider a hash join path; if it appears useful, push it into
1266 : * the joinrel's pathlist via add_path().
1267 : */
1268 : static void
1269 636644 : try_hashjoin_path(PlannerInfo *root,
1270 : RelOptInfo *joinrel,
1271 : Path *outer_path,
1272 : Path *inner_path,
1273 : List *hashclauses,
1274 : JoinType jointype,
1275 : JoinPathExtraData *extra)
1276 : {
1277 : Relids required_outer;
1278 : JoinCostWorkspace workspace;
1279 :
1280 : /*
1281 : * If we are forming an outer join at this join, it's nonsensical to use
1282 : * an input path that uses the outer join as part of its parameterization.
1283 : * (This can happen despite our join order restrictions, since those apply
1284 : * to what is in an input relation not what its parameters are.)
1285 : */
1286 797661 : if (extra->sjinfo->ojrelid != 0 &&
1287 322009 : (bms_is_member(extra->sjinfo->ojrelid, PATH_REQ_OUTER(inner_path)) ||
1288 160992 : bms_is_member(extra->sjinfo->ojrelid, PATH_REQ_OUTER(outer_path))))
1289 93797 : return;
1290 :
1291 : /*
1292 : * Check to see if proposed path is still parameterized, and reject if the
1293 : * parameterization wouldn't be sensible.
1294 : */
1295 636594 : required_outer = calc_non_nestloop_required_outer(outer_path,
1296 : inner_path);
1297 636594 : if (required_outer &&
1298 105457 : !bms_overlap(required_outer, extra->param_source_rels))
1299 : {
1300 : /* Waste no memory when we reject a path here */
1301 93747 : bms_free(required_outer);
1302 93747 : return;
1303 : }
1304 :
1305 : /*
1306 : * See comments in try_nestloop_path(). Also note that hashjoin paths
1307 : * never have any output pathkeys, per comments in create_hashjoin_path.
1308 : */
1309 542847 : initial_cost_hashjoin(root, &workspace, jointype, hashclauses,
1310 : outer_path, inner_path, extra, false);
1311 :
1312 542847 : if (add_path_precheck(joinrel, workspace.disabled_nodes,
1313 : workspace.startup_cost, workspace.total_cost,
1314 : NIL, required_outer))
1315 : {
1316 265232 : add_path(joinrel, (Path *)
1317 265232 : create_hashjoin_path(root,
1318 : joinrel,
1319 : jointype,
1320 : &workspace,
1321 : extra,
1322 : outer_path,
1323 : inner_path,
1324 : false, /* parallel_hash */
1325 : extra->restrictlist,
1326 : required_outer,
1327 : hashclauses));
1328 : }
1329 : else
1330 : {
1331 : /* Waste no memory when we reject a path here */
1332 277615 : bms_free(required_outer);
1333 : }
1334 : }
1335 :
1336 : /*
1337 : * try_partial_hashjoin_path
1338 : * Consider a partial hashjoin join path; if it appears useful, push it into
1339 : * the joinrel's partial_pathlist via add_partial_path().
1340 : * The outer side is partial. If parallel_hash is true, then the inner path
1341 : * must be partial and will be run in parallel to create one or more shared
1342 : * hash tables; otherwise the inner path must be complete and a copy of it
1343 : * is run in every process to create separate identical private hash tables.
1344 : */
1345 : static void
1346 114016 : try_partial_hashjoin_path(PlannerInfo *root,
1347 : RelOptInfo *joinrel,
1348 : Path *outer_path,
1349 : Path *inner_path,
1350 : List *hashclauses,
1351 : JoinType jointype,
1352 : JoinPathExtraData *extra,
1353 : bool parallel_hash)
1354 : {
1355 : JoinCostWorkspace workspace;
1356 :
1357 : /*
1358 : * If the inner path is parameterized, we can't use a partial hashjoin.
1359 : * Parameterized partial paths are not supported. The caller should
1360 : * already have verified that no lateral rels are required here.
1361 : */
1362 : Assert(bms_is_empty(joinrel->lateral_relids));
1363 : Assert(bms_is_empty(PATH_REQ_OUTER(outer_path)));
1364 114016 : if (!bms_is_empty(PATH_REQ_OUTER(inner_path)))
1365 32158 : return;
1366 :
1367 : /*
1368 : * Before creating a path, get a quick lower bound on what it is likely to
1369 : * cost. Bail out right away if it looks terrible.
1370 : */
1371 114016 : initial_cost_hashjoin(root, &workspace, jointype, hashclauses,
1372 : outer_path, inner_path, extra, parallel_hash);
1373 114016 : if (!add_partial_path_precheck(joinrel, workspace.disabled_nodes,
1374 : workspace.startup_cost,
1375 : workspace.total_cost, NIL))
1376 32158 : return;
1377 :
1378 : /* Might be good enough to be worth trying, so let's try it. */
1379 81858 : add_partial_path(joinrel, (Path *)
1380 81858 : create_hashjoin_path(root,
1381 : joinrel,
1382 : jointype,
1383 : &workspace,
1384 : extra,
1385 : outer_path,
1386 : inner_path,
1387 : parallel_hash,
1388 : extra->restrictlist,
1389 : NULL,
1390 : hashclauses));
1391 : }
1392 :
1393 : /*
1394 : * sort_inner_and_outer
1395 : * Create mergejoin join paths by explicitly sorting both the outer and
1396 : * inner join relations on each available merge ordering.
1397 : *
1398 : * 'joinrel' is the join relation
1399 : * 'outerrel' is the outer join relation
1400 : * 'innerrel' is the inner join relation
1401 : * 'jointype' is the type of join to do
1402 : * 'extra' contains additional input values
1403 : */
1404 : static void
1405 616428 : sort_inner_and_outer(PlannerInfo *root,
1406 : RelOptInfo *joinrel,
1407 : RelOptInfo *outerrel,
1408 : RelOptInfo *innerrel,
1409 : JoinType jointype,
1410 : JoinPathExtraData *extra)
1411 : {
1412 : Path *outer_path;
1413 : Path *inner_path;
1414 616428 : Path *cheapest_partial_outer = NULL;
1415 616428 : Path *cheapest_safe_inner = NULL;
1416 : List *all_pathkeys;
1417 : ListCell *l;
1418 :
1419 : /* Nothing to do if there are no available mergejoin clauses */
1420 616428 : if (extra->mergeclause_list == NIL)
1421 152383 : return;
1422 :
1423 : /*
1424 : * We only consider the cheapest-total-cost input paths, since we are
1425 : * assuming here that a sort is required. We will consider
1426 : * cheapest-startup-cost input paths later, and only if they don't need a
1427 : * sort.
1428 : *
1429 : * This function intentionally does not consider parameterized input
1430 : * paths, except when the cheapest-total is parameterized. If we did so,
1431 : * we'd have a combinatorial explosion of mergejoin paths of dubious
1432 : * value. This interacts with decisions elsewhere that also discriminate
1433 : * against mergejoins with parameterized inputs; see comments in
1434 : * src/backend/optimizer/README.
1435 : */
1436 464045 : outer_path = outerrel->cheapest_total_path;
1437 464045 : inner_path = innerrel->cheapest_total_path;
1438 :
1439 : /*
1440 : * If either cheapest-total path is parameterized by the other rel, we
1441 : * can't use a mergejoin. (There's no use looking for alternative input
1442 : * paths, since these should already be the least-parameterized available
1443 : * paths.)
1444 : */
1445 464045 : if (PATH_PARAM_BY_REL(outer_path, innerrel) ||
1446 462115 : PATH_PARAM_BY_REL(inner_path, outerrel))
1447 3884 : return;
1448 :
1449 : /*
1450 : * If the joinrel is parallel-safe, we may be able to consider a partial
1451 : * merge join. However, we can't handle JOIN_FULL, JOIN_RIGHT and
1452 : * JOIN_RIGHT_ANTI, because they can produce false null extended rows.
1453 : * Also, the resulting path must not be parameterized.
1454 : */
1455 460161 : if (joinrel->consider_parallel &&
1456 415728 : jointype != JOIN_FULL &&
1457 363643 : jointype != JOIN_RIGHT &&
1458 360526 : jointype != JOIN_RIGHT_ANTI &&
1459 360526 : outerrel->partial_pathlist != NIL &&
1460 52653 : bms_is_empty(joinrel->lateral_relids))
1461 : {
1462 52653 : cheapest_partial_outer = (Path *) linitial(outerrel->partial_pathlist);
1463 :
1464 52653 : if (inner_path->parallel_safe)
1465 52522 : cheapest_safe_inner = inner_path;
1466 : else
1467 : cheapest_safe_inner =
1468 131 : get_cheapest_parallel_safe_total_inner(innerrel->pathlist);
1469 : }
1470 :
1471 : /*
1472 : * Each possible ordering of the available mergejoin clauses will generate
1473 : * a differently-sorted result path at essentially the same cost. We have
1474 : * no basis for choosing one over another at this level of joining, but
1475 : * some sort orders may be more useful than others for higher-level
1476 : * mergejoins, so it's worth considering multiple orderings.
1477 : *
1478 : * Actually, it's not quite true that every mergeclause ordering will
1479 : * generate a different path order, because some of the clauses may be
1480 : * partially redundant (refer to the same EquivalenceClasses). Therefore,
1481 : * what we do is convert the mergeclause list to a list of canonical
1482 : * pathkeys, and then consider different orderings of the pathkeys.
1483 : *
1484 : * Generating a path for *every* permutation of the pathkeys doesn't seem
1485 : * like a winning strategy; the cost in planning time is too high. For
1486 : * now, we generate one path for each pathkey, listing that pathkey first
1487 : * and the rest in random order. This should allow at least a one-clause
1488 : * mergejoin without re-sorting against any other possible mergejoin
1489 : * partner path. But if we've not guessed the right ordering of secondary
1490 : * keys, we may end up evaluating clauses as qpquals when they could have
1491 : * been done as mergeclauses. (In practice, it's rare that there's more
1492 : * than two or three mergeclauses, so expending a huge amount of thought
1493 : * on that is probably not worth it.)
1494 : *
1495 : * The pathkey order returned by select_outer_pathkeys_for_merge() has
1496 : * some heuristics behind it (see that function), so be sure to try it
1497 : * exactly as-is as well as making variants.
1498 : */
1499 460161 : all_pathkeys = select_outer_pathkeys_for_merge(root,
1500 : extra->mergeclause_list,
1501 : joinrel);
1502 :
1503 990472 : foreach(l, all_pathkeys)
1504 : {
1505 530311 : PathKey *front_pathkey = (PathKey *) lfirst(l);
1506 : List *cur_mergeclauses;
1507 : List *outerkeys;
1508 : List *innerkeys;
1509 : List *merge_pathkeys;
1510 :
1511 : /* Make a pathkey list with this guy first */
1512 530311 : if (l != list_head(all_pathkeys))
1513 70150 : outerkeys = lcons(front_pathkey,
1514 : list_delete_nth_cell(list_copy(all_pathkeys),
1515 : foreach_current_index(l)));
1516 : else
1517 460161 : outerkeys = all_pathkeys; /* no work at first one... */
1518 :
1519 : /* Sort the mergeclauses into the corresponding ordering */
1520 : cur_mergeclauses =
1521 530311 : find_mergeclauses_for_outer_pathkeys(root,
1522 : outerkeys,
1523 : extra->mergeclause_list);
1524 :
1525 : /* Should have used them all... */
1526 : Assert(list_length(cur_mergeclauses) == list_length(extra->mergeclause_list));
1527 :
1528 : /* Build sort pathkeys for the inner side */
1529 530311 : innerkeys = make_inner_pathkeys_for_merge(root,
1530 : cur_mergeclauses,
1531 : outerkeys);
1532 :
1533 : /* Build pathkeys representing output sort order */
1534 530311 : merge_pathkeys = build_join_pathkeys(root, joinrel, jointype,
1535 : outerkeys);
1536 :
1537 : /*
1538 : * And now we can make the path.
1539 : *
1540 : * Note: it's possible that the cheapest paths will already be sorted
1541 : * properly. try_mergejoin_path will detect that case and suppress an
1542 : * explicit sort step, so we needn't do so here.
1543 : */
1544 530311 : try_mergejoin_path(root,
1545 : joinrel,
1546 : outer_path,
1547 : inner_path,
1548 : merge_pathkeys,
1549 : cur_mergeclauses,
1550 : outerkeys,
1551 : innerkeys,
1552 : jointype,
1553 : extra,
1554 : false);
1555 :
1556 : /*
1557 : * If we have partial outer and parallel safe inner path then try
1558 : * partial mergejoin path.
1559 : */
1560 530311 : if (cheapest_partial_outer && cheapest_safe_inner)
1561 55236 : try_partial_mergejoin_path(root,
1562 : joinrel,
1563 : cheapest_partial_outer,
1564 : cheapest_safe_inner,
1565 : merge_pathkeys,
1566 : cur_mergeclauses,
1567 : outerkeys,
1568 : innerkeys,
1569 : jointype,
1570 : extra);
1571 : }
1572 : }
1573 :
1574 : /*
1575 : * generate_mergejoin_paths
1576 : * Creates possible mergejoin paths for input outerpath.
1577 : *
1578 : * We generate mergejoins if mergejoin clauses are available. We have
1579 : * two ways to generate the inner path for a mergejoin: sort the cheapest
1580 : * inner path, or use an inner path that is already suitably ordered for the
1581 : * merge. If we have several mergeclauses, it could be that there is no inner
1582 : * path (or only a very expensive one) for the full list of mergeclauses, but
1583 : * better paths exist if we truncate the mergeclause list (thereby discarding
1584 : * some sort key requirements). So, we consider truncations of the
1585 : * mergeclause list as well as the full list. (Ideally we'd consider all
1586 : * subsets of the mergeclause list, but that seems way too expensive.)
1587 : */
1588 : static void
1589 1214285 : generate_mergejoin_paths(PlannerInfo *root,
1590 : RelOptInfo *joinrel,
1591 : RelOptInfo *innerrel,
1592 : Path *outerpath,
1593 : JoinType jointype,
1594 : JoinPathExtraData *extra,
1595 : bool useallclauses,
1596 : Path *inner_cheapest_total,
1597 : List *merge_pathkeys,
1598 : bool is_partial)
1599 : {
1600 : List *mergeclauses;
1601 : List *innersortkeys;
1602 : List *trialsortkeys;
1603 : Path *cheapest_startup_inner;
1604 : Path *cheapest_total_inner;
1605 : int num_sortkeys;
1606 : int sortkeycnt;
1607 :
1608 : /* Look for useful mergeclauses (if any) */
1609 : mergeclauses =
1610 1214285 : find_mergeclauses_for_outer_pathkeys(root,
1611 : outerpath->pathkeys,
1612 : extra->mergeclause_list);
1613 :
1614 : /*
1615 : * Done with this outer path if no chance for a mergejoin.
1616 : *
1617 : * Special corner case: for "x FULL JOIN y ON true", there will be no join
1618 : * clauses at all. Ordinarily we'd generate a clauseless nestloop path,
1619 : * but since mergejoin is our only join type that supports FULL JOIN
1620 : * without any join clauses, it's necessary to generate a clauseless
1621 : * mergejoin path instead.
1622 : */
1623 1214285 : if (mergeclauses == NIL)
1624 : {
1625 854636 : if (jointype == JOIN_FULL)
1626 : /* okay to try for mergejoin */ ;
1627 : else
1628 851930 : return;
1629 : }
1630 421154 : if (useallclauses &&
1631 58799 : list_length(mergeclauses) != list_length(extra->mergeclause_list))
1632 9878 : return;
1633 :
1634 : /* Compute the required ordering of the inner path */
1635 352477 : innersortkeys = make_inner_pathkeys_for_merge(root,
1636 : mergeclauses,
1637 : outerpath->pathkeys);
1638 :
1639 : /*
1640 : * Generate a mergejoin on the basis of sorting the cheapest inner. Since
1641 : * a sort will be needed, only cheapest total cost matters. (But
1642 : * try_mergejoin_path will do the right thing if inner_cheapest_total is
1643 : * already correctly sorted.)
1644 : */
1645 352477 : try_mergejoin_path(root,
1646 : joinrel,
1647 : outerpath,
1648 : inner_cheapest_total,
1649 : merge_pathkeys,
1650 : mergeclauses,
1651 : NIL,
1652 : innersortkeys,
1653 : jointype,
1654 : extra,
1655 : is_partial);
1656 :
1657 : /*
1658 : * Look for presorted inner paths that satisfy the innersortkey list ---
1659 : * or any truncation thereof, if we are allowed to build a mergejoin using
1660 : * a subset of the merge clauses. Here, we consider both cheap startup
1661 : * cost and cheap total cost.
1662 : *
1663 : * Currently we do not consider parameterized inner paths here. This
1664 : * interacts with decisions elsewhere that also discriminate against
1665 : * mergejoins with parameterized inputs; see comments in
1666 : * src/backend/optimizer/README.
1667 : *
1668 : * As we shorten the sortkey list, we should consider only paths that are
1669 : * strictly cheaper than (in particular, not the same as) any path found
1670 : * in an earlier iteration. Otherwise we'd be intentionally using fewer
1671 : * merge keys than a given path allows (treating the rest as plain
1672 : * joinquals), which is unlikely to be a good idea. Also, eliminating
1673 : * paths here on the basis of compare_path_costs is a lot cheaper than
1674 : * building the mergejoin path only to throw it away.
1675 : *
1676 : * If inner_cheapest_total is well enough sorted to have not required a
1677 : * sort in the path made above, we shouldn't make a duplicate path with
1678 : * it, either. We handle that case with the same logic that handles the
1679 : * previous consideration, by initializing the variables that track
1680 : * cheapest-so-far properly. Note that we do NOT reject
1681 : * inner_cheapest_total if we find it matches some shorter set of
1682 : * pathkeys. That case corresponds to using fewer mergekeys to avoid
1683 : * sorting inner_cheapest_total, whereas we did sort it above, so the
1684 : * plans being considered are different.
1685 : */
1686 352477 : if (pathkeys_contained_in(innersortkeys,
1687 : inner_cheapest_total->pathkeys))
1688 : {
1689 : /* inner_cheapest_total didn't require a sort */
1690 11226 : cheapest_startup_inner = inner_cheapest_total;
1691 11226 : cheapest_total_inner = inner_cheapest_total;
1692 : }
1693 : else
1694 : {
1695 : /* it did require a sort, at least for the full set of keys */
1696 341251 : cheapest_startup_inner = NULL;
1697 341251 : cheapest_total_inner = NULL;
1698 : }
1699 352477 : num_sortkeys = list_length(innersortkeys);
1700 352477 : if (num_sortkeys > 1 && !useallclauses)
1701 20716 : trialsortkeys = list_copy(innersortkeys); /* need modifiable copy */
1702 : else
1703 331761 : trialsortkeys = innersortkeys; /* won't really truncate */
1704 :
1705 677356 : for (sortkeycnt = num_sortkeys; sortkeycnt > 0; sortkeycnt--)
1706 : {
1707 : Path *innerpath;
1708 373688 : List *newclauses = NIL;
1709 :
1710 : /*
1711 : * Look for an inner path ordered well enough for the first
1712 : * 'sortkeycnt' innersortkeys. NB: trialsortkeys list is modified
1713 : * destructively, which is why we made a copy...
1714 : */
1715 373688 : trialsortkeys = list_truncate(trialsortkeys, sortkeycnt);
1716 373688 : innerpath = get_cheapest_path_for_pathkeys(innerrel->pathlist,
1717 : trialsortkeys,
1718 : NULL,
1719 : TOTAL_COST,
1720 : is_partial);
1721 373688 : if (innerpath != NULL &&
1722 18070 : (cheapest_total_inner == NULL ||
1723 18070 : compare_path_costs(innerpath, cheapest_total_inner,
1724 : TOTAL_COST) < 0))
1725 : {
1726 : /* Found a cheap (or even-cheaper) sorted path */
1727 : /* Select the right mergeclauses, if we didn't already */
1728 208674 : if (sortkeycnt < num_sortkeys)
1729 : {
1730 : newclauses =
1731 10290 : trim_mergeclauses_for_inner_pathkeys(root,
1732 : mergeclauses,
1733 : trialsortkeys);
1734 : Assert(newclauses != NIL);
1735 : }
1736 : else
1737 198384 : newclauses = mergeclauses;
1738 208674 : try_mergejoin_path(root,
1739 : joinrel,
1740 : outerpath,
1741 : innerpath,
1742 : merge_pathkeys,
1743 : newclauses,
1744 : NIL,
1745 : NIL,
1746 : jointype,
1747 : extra,
1748 : is_partial);
1749 208674 : cheapest_total_inner = innerpath;
1750 : }
1751 : /* Same on the basis of cheapest startup cost ... */
1752 373688 : innerpath = get_cheapest_path_for_pathkeys(innerrel->pathlist,
1753 : trialsortkeys,
1754 : NULL,
1755 : STARTUP_COST,
1756 : is_partial);
1757 373688 : if (innerpath != NULL &&
1758 18070 : (cheapest_startup_inner == NULL ||
1759 18070 : compare_path_costs(innerpath, cheapest_startup_inner,
1760 : STARTUP_COST) < 0))
1761 : {
1762 : /* Found a cheap (or even-cheaper) sorted path */
1763 207021 : if (innerpath != cheapest_total_inner)
1764 : {
1765 : /*
1766 : * Avoid rebuilding clause list if we already made one; saves
1767 : * memory in big join trees...
1768 : */
1769 1761 : if (newclauses == NIL)
1770 : {
1771 104 : if (sortkeycnt < num_sortkeys)
1772 : {
1773 : newclauses =
1774 63 : trim_mergeclauses_for_inner_pathkeys(root,
1775 : mergeclauses,
1776 : trialsortkeys);
1777 : Assert(newclauses != NIL);
1778 : }
1779 : else
1780 41 : newclauses = mergeclauses;
1781 : }
1782 1761 : try_mergejoin_path(root,
1783 : joinrel,
1784 : outerpath,
1785 : innerpath,
1786 : merge_pathkeys,
1787 : newclauses,
1788 : NIL,
1789 : NIL,
1790 : jointype,
1791 : extra,
1792 : is_partial);
1793 : }
1794 207021 : cheapest_startup_inner = innerpath;
1795 : }
1796 :
1797 : /*
1798 : * Don't consider truncated sortkeys if we need all clauses.
1799 : */
1800 373688 : if (useallclauses)
1801 48809 : break;
1802 : }
1803 : }
1804 :
1805 : /*
1806 : * match_unsorted_outer
1807 : * Creates possible join paths for processing a single join relation
1808 : * 'joinrel' by employing either iterative substitution or
1809 : * mergejoining on each of its possible outer paths (considering
1810 : * only outer paths that are already ordered well enough for merging).
1811 : *
1812 : * We always generate a nestloop path for each available outer path.
1813 : * In fact we may generate as many as five: one on the cheapest-total-cost
1814 : * inner path, one on the same with materialization, one on the
1815 : * cheapest-startup-cost inner path (if different), one on the
1816 : * cheapest-total inner-indexscan path (if any), and one on the
1817 : * cheapest-startup inner-indexscan path (if different).
1818 : *
1819 : * We also consider mergejoins if mergejoin clauses are available. See
1820 : * detailed comments in generate_mergejoin_paths.
1821 : *
1822 : * 'joinrel' is the join relation
1823 : * 'outerrel' is the outer join relation
1824 : * 'innerrel' is the inner join relation
1825 : * 'jointype' is the type of join to do
1826 : * 'extra' contains additional input values
1827 : */
1828 : static void
1829 616428 : match_unsorted_outer(PlannerInfo *root,
1830 : RelOptInfo *joinrel,
1831 : RelOptInfo *outerrel,
1832 : RelOptInfo *innerrel,
1833 : JoinType jointype,
1834 : JoinPathExtraData *extra)
1835 : {
1836 : bool nestjoinOK;
1837 : bool useallclauses;
1838 616428 : Path *inner_cheapest_total = innerrel->cheapest_total_path;
1839 616428 : Path *matpath = NULL;
1840 : ListCell *lc1;
1841 :
1842 : /*
1843 : * For now we do not support RIGHT_SEMI join in mergejoin or nestloop
1844 : * join.
1845 : */
1846 616428 : if (jointype == JOIN_RIGHT_SEMI)
1847 1104 : return;
1848 :
1849 : /*
1850 : * Nestloop only supports inner, left, semi, and anti joins. Also, if we
1851 : * are doing a right, right-anti or full mergejoin, we must use *all* the
1852 : * mergeclauses as join clauses, else we will not have a valid plan.
1853 : * (Although these two flags are currently inverses, keep them separate
1854 : * for clarity and possible future changes.)
1855 : */
1856 615324 : switch (jointype)
1857 : {
1858 544584 : case JOIN_INNER:
1859 : case JOIN_LEFT:
1860 : case JOIN_SEMI:
1861 : case JOIN_ANTI:
1862 544584 : nestjoinOK = true;
1863 544584 : useallclauses = false;
1864 544584 : break;
1865 70740 : case JOIN_RIGHT:
1866 : case JOIN_RIGHT_ANTI:
1867 : case JOIN_FULL:
1868 70740 : nestjoinOK = false;
1869 70740 : useallclauses = true;
1870 70740 : break;
1871 0 : default:
1872 0 : elog(ERROR, "unrecognized join type: %d",
1873 : (int) jointype);
1874 : nestjoinOK = false; /* keep compiler quiet */
1875 : useallclauses = false;
1876 : break;
1877 : }
1878 :
1879 : /*
1880 : * If inner_cheapest_total is parameterized by the outer rel, ignore it;
1881 : * we will consider it below as a member of cheapest_parameterized_paths,
1882 : * but the other possibilities considered in this routine aren't usable.
1883 : *
1884 : * Furthermore, if the inner side is a unique-ified relation, we cannot
1885 : * generate any valid paths here, because the inner rel's dependency on
1886 : * the outer rel makes unique-ification meaningless.
1887 : */
1888 615324 : if (PATH_PARAM_BY_REL(inner_cheapest_total, outerrel))
1889 : {
1890 12647 : inner_cheapest_total = NULL;
1891 :
1892 12647 : if (RELATION_WAS_MADE_UNIQUE(innerrel, extra->sjinfo, jointype))
1893 30 : return;
1894 : }
1895 :
1896 615294 : if (nestjoinOK)
1897 : {
1898 : /*
1899 : * Consider materializing the cheapest inner path, unless that is
1900 : * disabled or the path in question materializes its output anyway.
1901 : *
1902 : * At present, we only consider materialization for non-partial outer
1903 : * paths, so it's correct to test PGS_CONSIDER_NONPARTIAL here. If we
1904 : * ever want to consider materialization for partial paths, we'll need
1905 : * to create matpath whenever PGS_NESTLOOP_MATERIALIZE is set, use it
1906 : * for partial paths either way, and use it for non-partial paths only
1907 : * when PGS_CONSIDER_NONPARTIAL is also set.
1908 : */
1909 544554 : if ((extra->pgs_mask &
1910 : (PGS_NESTLOOP_MATERIALIZE | PGS_CONSIDER_NONPARTIAL)) ==
1911 479462 : (PGS_NESTLOOP_MATERIALIZE | PGS_CONSIDER_NONPARTIAL) &&
1912 467723 : inner_cheapest_total != NULL &&
1913 467723 : !ExecMaterializesOutput(inner_cheapest_total->pathtype))
1914 : matpath = (Path *)
1915 450072 : create_material_path(innerrel, inner_cheapest_total, true);
1916 : }
1917 :
1918 1981080 : foreach(lc1, outerrel->pathlist)
1919 : {
1920 1365786 : Path *outerpath = (Path *) lfirst(lc1);
1921 : List *merge_pathkeys;
1922 :
1923 : /*
1924 : * We cannot use an outer path that is parameterized by the inner rel.
1925 : */
1926 1365786 : if (PATH_PARAM_BY_REL(outerpath, innerrel))
1927 210582 : continue;
1928 :
1929 : /*
1930 : * The result will have this sort order (even if it is implemented as
1931 : * a nestloop, and even if some of the mergeclauses are implemented by
1932 : * qpquals rather than as true mergeclauses):
1933 : */
1934 1155204 : merge_pathkeys = build_join_pathkeys(root, joinrel, jointype,
1935 : outerpath->pathkeys);
1936 :
1937 1155204 : if (nestjoinOK)
1938 : {
1939 : /*
1940 : * Consider nestloop joins using this outer path and various
1941 : * available paths for the inner relation. We consider the
1942 : * cheapest-total paths for each available parameterization of the
1943 : * inner relation, including the unparameterized case.
1944 : */
1945 : ListCell *lc2;
1946 :
1947 2606546 : foreach(lc2, innerrel->cheapest_parameterized_paths)
1948 : {
1949 1581918 : Path *innerpath = (Path *) lfirst(lc2);
1950 : Path *mpath;
1951 :
1952 1581918 : try_nestloop_path(root,
1953 : joinrel,
1954 : outerpath,
1955 : innerpath,
1956 : merge_pathkeys,
1957 : jointype,
1958 : PGS_NESTLOOP_PLAIN,
1959 : extra);
1960 :
1961 : /*
1962 : * Try generating a memoize path and see if that makes the
1963 : * nested loop any cheaper.
1964 : */
1965 1581918 : mpath = get_memoize_path(root, innerrel, outerrel,
1966 : innerpath, outerpath, jointype,
1967 : extra);
1968 1581918 : if (mpath != NULL)
1969 215058 : try_nestloop_path(root,
1970 : joinrel,
1971 : outerpath,
1972 : mpath,
1973 : merge_pathkeys,
1974 : jointype,
1975 : PGS_NESTLOOP_MEMOIZE,
1976 : extra);
1977 : }
1978 :
1979 : /* Also consider materialized form of the cheapest inner path */
1980 1024628 : if (matpath != NULL)
1981 864306 : try_nestloop_path(root,
1982 : joinrel,
1983 : outerpath,
1984 : matpath,
1985 : merge_pathkeys,
1986 : jointype,
1987 : PGS_NESTLOOP_MATERIALIZE,
1988 : extra);
1989 : }
1990 :
1991 : /* Can't do anything else if inner rel is parameterized by outer */
1992 1155204 : if (inner_cheapest_total == NULL)
1993 19714 : continue;
1994 :
1995 : /* Generate merge join paths */
1996 1135490 : generate_mergejoin_paths(root, joinrel, innerrel, outerpath,
1997 : jointype, extra, useallclauses,
1998 : inner_cheapest_total, merge_pathkeys,
1999 : false);
2000 : }
2001 :
2002 : /*
2003 : * Consider partial nestloop and mergejoin plan if outerrel has any
2004 : * partial path and the joinrel is parallel-safe. However, we can't
2005 : * handle joins needing lateral rels, since partial paths must not be
2006 : * parameterized. Similarly, we can't handle JOIN_FULL, JOIN_RIGHT and
2007 : * JOIN_RIGHT_ANTI, because they can produce false null extended rows.
2008 : */
2009 615294 : if (joinrel->consider_parallel &&
2010 530568 : jointype != JOIN_FULL &&
2011 472088 : jointype != JOIN_RIGHT &&
2012 468324 : jointype != JOIN_RIGHT_ANTI &&
2013 468324 : outerrel->partial_pathlist != NIL &&
2014 62881 : bms_is_empty(joinrel->lateral_relids))
2015 : {
2016 62881 : if (nestjoinOK)
2017 62881 : consider_parallel_nestloop(root, joinrel, outerrel, innerrel,
2018 : jointype, extra);
2019 :
2020 : /*
2021 : * If inner_cheapest_total is NULL or non parallel-safe then find the
2022 : * cheapest total parallel safe path.
2023 : */
2024 62881 : if (inner_cheapest_total == NULL ||
2025 62531 : !inner_cheapest_total->parallel_safe)
2026 : {
2027 : inner_cheapest_total =
2028 688 : get_cheapest_parallel_safe_total_inner(innerrel->pathlist);
2029 : }
2030 :
2031 62881 : if (inner_cheapest_total)
2032 62499 : consider_parallel_mergejoin(root, joinrel, outerrel, innerrel,
2033 : jointype, extra,
2034 : inner_cheapest_total);
2035 : }
2036 : }
2037 :
2038 : /*
2039 : * consider_parallel_mergejoin
2040 : * Try to build partial paths for a joinrel by joining a partial path
2041 : * for the outer relation to a complete path for the inner relation.
2042 : *
2043 : * 'joinrel' is the join relation
2044 : * 'outerrel' is the outer join relation
2045 : * 'innerrel' is the inner join relation
2046 : * 'jointype' is the type of join to do
2047 : * 'extra' contains additional input values
2048 : * 'inner_cheapest_total' cheapest total path for innerrel
2049 : */
2050 : static void
2051 62499 : consider_parallel_mergejoin(PlannerInfo *root,
2052 : RelOptInfo *joinrel,
2053 : RelOptInfo *outerrel,
2054 : RelOptInfo *innerrel,
2055 : JoinType jointype,
2056 : JoinPathExtraData *extra,
2057 : Path *inner_cheapest_total)
2058 : {
2059 : ListCell *lc1;
2060 :
2061 : /* generate merge join path for each partial outer path */
2062 141294 : foreach(lc1, outerrel->partial_pathlist)
2063 : {
2064 78795 : Path *outerpath = (Path *) lfirst(lc1);
2065 : List *merge_pathkeys;
2066 :
2067 : /*
2068 : * Figure out what useful ordering any paths we create will have.
2069 : */
2070 78795 : merge_pathkeys = build_join_pathkeys(root, joinrel, jointype,
2071 : outerpath->pathkeys);
2072 :
2073 78795 : generate_mergejoin_paths(root, joinrel, innerrel, outerpath, jointype,
2074 : extra, false, inner_cheapest_total,
2075 : merge_pathkeys, true);
2076 : }
2077 62499 : }
2078 :
2079 : /*
2080 : * consider_parallel_nestloop
2081 : * Try to build partial paths for a joinrel by joining a partial path for the
2082 : * outer relation to a complete path for the inner relation.
2083 : *
2084 : * 'joinrel' is the join relation
2085 : * 'outerrel' is the outer join relation
2086 : * 'innerrel' is the inner join relation
2087 : * 'jointype' is the type of join to do
2088 : * 'extra' contains additional input values
2089 : */
2090 : static void
2091 62881 : consider_parallel_nestloop(PlannerInfo *root,
2092 : RelOptInfo *joinrel,
2093 : RelOptInfo *outerrel,
2094 : RelOptInfo *innerrel,
2095 : JoinType jointype,
2096 : JoinPathExtraData *extra)
2097 : {
2098 62881 : Path *inner_cheapest_total = innerrel->cheapest_total_path;
2099 62881 : Path *matpath = NULL;
2100 : ListCell *lc1;
2101 :
2102 : /*
2103 : * Consider materializing the cheapest inner path, unless: 1)
2104 : * materialization is disabled here, 2) the cheapest inner path is not
2105 : * parallel-safe, 3) the cheapest inner path is parameterized by the outer
2106 : * rel, or 4) the cheapest inner path materializes its output anyway.
2107 : */
2108 62881 : if ((extra->pgs_mask & PGS_NESTLOOP_MATERIALIZE) != 0 &&
2109 53523 : inner_cheapest_total->parallel_safe &&
2110 53322 : !PATH_PARAM_BY_REL(inner_cheapest_total, outerrel) &&
2111 53062 : !ExecMaterializesOutput(inner_cheapest_total->pathtype))
2112 : {
2113 : matpath = (Path *)
2114 52998 : create_material_path(innerrel, inner_cheapest_total, true);
2115 : Assert(matpath->parallel_safe);
2116 : }
2117 :
2118 142173 : foreach(lc1, outerrel->partial_pathlist)
2119 : {
2120 79292 : Path *outerpath = (Path *) lfirst(lc1);
2121 : List *pathkeys;
2122 : ListCell *lc2;
2123 :
2124 : /* Figure out what useful ordering any paths we create will have. */
2125 79292 : pathkeys = build_join_pathkeys(root, joinrel, jointype,
2126 : outerpath->pathkeys);
2127 :
2128 : /*
2129 : * Try the cheapest parameterized paths; only those which will produce
2130 : * an unparameterized path when joined to this outerrel will survive
2131 : * try_partial_nestloop_path. The cheapest unparameterized path is
2132 : * also in this list.
2133 : */
2134 166490 : foreach(lc2, innerrel->cheapest_parameterized_paths)
2135 : {
2136 87198 : Path *innerpath = (Path *) lfirst(lc2);
2137 : Path *mpath;
2138 :
2139 : /* Can't join to an inner path that is not parallel-safe */
2140 87198 : if (!innerpath->parallel_safe)
2141 397 : continue;
2142 :
2143 86801 : try_partial_nestloop_path(root, joinrel, outerpath, innerpath,
2144 : pathkeys, jointype,
2145 : PGS_NESTLOOP_PLAIN, extra);
2146 :
2147 : /*
2148 : * Try generating a memoize path and see if that makes the nested
2149 : * loop any cheaper.
2150 : */
2151 86801 : mpath = get_memoize_path(root, innerrel, outerrel,
2152 : innerpath, outerpath, jointype,
2153 : extra);
2154 86801 : if (mpath != NULL)
2155 4010 : try_partial_nestloop_path(root, joinrel, outerpath, mpath,
2156 : pathkeys, jointype,
2157 : PGS_NESTLOOP_MEMOIZE, extra);
2158 : }
2159 :
2160 : /* Also consider materialized form of the cheapest inner path */
2161 79292 : if (matpath != NULL)
2162 66976 : try_partial_nestloop_path(root, joinrel, outerpath, matpath,
2163 : pathkeys, jointype,
2164 : PGS_NESTLOOP_MATERIALIZE, extra);
2165 : }
2166 62881 : }
2167 :
2168 : /*
2169 : * hash_inner_and_outer
2170 : * Create hashjoin join paths by explicitly hashing both the outer and
2171 : * inner keys of each available hash clause.
2172 : *
2173 : * 'joinrel' is the join relation
2174 : * 'outerrel' is the outer join relation
2175 : * 'innerrel' is the inner join relation
2176 : * 'jointype' is the type of join to do
2177 : * 'extra' contains additional input values
2178 : */
2179 : static void
2180 560369 : hash_inner_and_outer(PlannerInfo *root,
2181 : RelOptInfo *joinrel,
2182 : RelOptInfo *outerrel,
2183 : RelOptInfo *innerrel,
2184 : JoinType jointype,
2185 : JoinPathExtraData *extra)
2186 : {
2187 560369 : bool isouterjoin = IS_OUTER_JOIN(jointype);
2188 : List *hashclauses;
2189 : ListCell *l;
2190 :
2191 : /*
2192 : * We need to build only one hashclauses list for any given pair of outer
2193 : * and inner relations; all of the hashable clauses will be used as keys.
2194 : *
2195 : * Scan the join's restrictinfo list to find hashjoinable clauses that are
2196 : * usable with this pair of sub-relations.
2197 : */
2198 560369 : hashclauses = NIL;
2199 1189190 : foreach(l, extra->restrictlist)
2200 : {
2201 628821 : RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l);
2202 :
2203 : /*
2204 : * If processing an outer join, only use its own join clauses for
2205 : * hashing. For inner joins we need not be so picky.
2206 : */
2207 628821 : if (isouterjoin && RINFO_IS_PUSHED_DOWN(restrictinfo, joinrel->relids))
2208 11602 : continue;
2209 :
2210 617219 : if (!restrictinfo->can_join ||
2211 563678 : restrictinfo->hashjoinoperator == InvalidOid)
2212 66454 : continue; /* not hashjoinable */
2213 :
2214 : /*
2215 : * Check if clause has the form "outer op inner" or "inner op outer".
2216 : */
2217 550765 : if (!clause_sides_match_join(restrictinfo, outerrel->relids,
2218 : innerrel->relids))
2219 144 : continue; /* no good for these input relations */
2220 :
2221 : /*
2222 : * If clause has the form "inner op outer", check if its operator has
2223 : * valid commutator. This is necessary because hashclauses in this
2224 : * form will get commuted in createplan.c to put the outer var on the
2225 : * left (see get_switched_clauses). This probably shouldn't ever
2226 : * fail, since hashable operators ought to have commutators, but be
2227 : * paranoid.
2228 : *
2229 : * The clause being hashjoinable indicates that it's an OpExpr.
2230 : */
2231 825340 : if (!restrictinfo->outer_is_left &&
2232 274719 : !OidIsValid(get_commutator(castNode(OpExpr, restrictinfo->clause)->opno)))
2233 5 : continue;
2234 :
2235 550616 : hashclauses = lappend(hashclauses, restrictinfo);
2236 : }
2237 :
2238 : /* If we found any usable hashclauses, make paths */
2239 560369 : if (hashclauses)
2240 : {
2241 : /*
2242 : * We consider both the cheapest-total-cost and cheapest-startup-cost
2243 : * outer paths. There's no need to consider any but the
2244 : * cheapest-total-cost inner path, however.
2245 : */
2246 479629 : Path *cheapest_startup_outer = outerrel->cheapest_startup_path;
2247 479629 : Path *cheapest_total_outer = outerrel->cheapest_total_path;
2248 479629 : Path *cheapest_total_inner = innerrel->cheapest_total_path;
2249 : ListCell *lc1;
2250 : ListCell *lc2;
2251 :
2252 : /*
2253 : * If either cheapest-total path is parameterized by the other rel, we
2254 : * can't use a hashjoin. (There's no use looking for alternative
2255 : * input paths, since these should already be the least-parameterized
2256 : * available paths.)
2257 : */
2258 479629 : if (PATH_PARAM_BY_REL(cheapest_total_outer, innerrel) ||
2259 477691 : PATH_PARAM_BY_REL(cheapest_total_inner, outerrel))
2260 3876 : return;
2261 :
2262 : /*
2263 : * Consider the cheapest startup outer together with the cheapest
2264 : * total inner, and then consider pairings of cheapest-total paths
2265 : * including parameterized ones. There is no use in generating
2266 : * parameterized paths on the basis of possibly cheap startup cost, so
2267 : * this is sufficient.
2268 : */
2269 475753 : if (cheapest_startup_outer != NULL)
2270 474000 : try_hashjoin_path(root,
2271 : joinrel,
2272 : cheapest_startup_outer,
2273 : cheapest_total_inner,
2274 : hashclauses,
2275 : jointype,
2276 : extra);
2277 :
2278 1180384 : foreach(lc1, outerrel->cheapest_parameterized_paths)
2279 : {
2280 704631 : Path *outerpath = (Path *) lfirst(lc1);
2281 :
2282 : /*
2283 : * We cannot use an outer path that is parameterized by the inner
2284 : * rel.
2285 : */
2286 704631 : if (PATH_PARAM_BY_REL(outerpath, innerrel))
2287 183593 : continue;
2288 :
2289 1306180 : foreach(lc2, innerrel->cheapest_parameterized_paths)
2290 : {
2291 785142 : Path *innerpath = (Path *) lfirst(lc2);
2292 :
2293 : /*
2294 : * We cannot use an inner path that is parameterized by the
2295 : * outer rel, either.
2296 : */
2297 785142 : if (PATH_PARAM_BY_REL(innerpath, outerrel))
2298 207430 : continue;
2299 :
2300 577712 : if (outerpath == cheapest_startup_outer &&
2301 : innerpath == cheapest_total_inner)
2302 415068 : continue; /* already tried it */
2303 :
2304 162644 : try_hashjoin_path(root,
2305 : joinrel,
2306 : outerpath,
2307 : innerpath,
2308 : hashclauses,
2309 : jointype,
2310 : extra);
2311 : }
2312 : }
2313 :
2314 : /*
2315 : * If the joinrel is parallel-safe, we may be able to consider a
2316 : * partial hash join.
2317 : *
2318 : * However, we can't handle JOIN_RIGHT_SEMI, because the hash table is
2319 : * either a shared hash table or a private hash table per backend. In
2320 : * the shared case, there is no concurrency protection for the match
2321 : * flags, so multiple workers could inspect and set the flags
2322 : * concurrently, potentially producing incorrect results. In the
2323 : * private case, each worker has its own copy of the hash table, so no
2324 : * single process has all the match flags.
2325 : *
2326 : * Also, the resulting path must not be parameterized.
2327 : */
2328 475753 : if (joinrel->consider_parallel &&
2329 428955 : jointype != JOIN_RIGHT_SEMI &&
2330 428955 : outerrel->partial_pathlist != NIL &&
2331 59410 : bms_is_empty(joinrel->lateral_relids))
2332 : {
2333 : Path *cheapest_partial_outer;
2334 59410 : Path *cheapest_partial_inner = NULL;
2335 59410 : Path *cheapest_safe_inner = NULL;
2336 :
2337 59410 : cheapest_partial_outer =
2338 59410 : (Path *) linitial(outerrel->partial_pathlist);
2339 :
2340 : /*
2341 : * Can we use a partial inner plan too, so that we can build a
2342 : * shared hash table in parallel?
2343 : */
2344 59410 : if (innerrel->partial_pathlist != NIL &&
2345 : enable_parallel_hash)
2346 : {
2347 57878 : cheapest_partial_inner =
2348 57878 : (Path *) linitial(innerrel->partial_pathlist);
2349 57878 : try_partial_hashjoin_path(root, joinrel,
2350 : cheapest_partial_outer,
2351 : cheapest_partial_inner,
2352 : hashclauses, jointype, extra,
2353 : true /* parallel_hash */ );
2354 : }
2355 :
2356 : /*
2357 : * Normally, given that the joinrel is parallel-safe, the cheapest
2358 : * total inner path will also be parallel-safe, but if not, we'll
2359 : * have to search for the cheapest safe, unparameterized inner
2360 : * path. If full, right, or right-anti join, we can't use
2361 : * parallelism (building the hash table in each backend) because
2362 : * no one process has all the match bits.
2363 : */
2364 59410 : if (jointype == JOIN_FULL ||
2365 56423 : jointype == JOIN_RIGHT ||
2366 : jointype == JOIN_RIGHT_ANTI)
2367 3244 : cheapest_safe_inner = NULL;
2368 56166 : else if (cheapest_total_inner->parallel_safe)
2369 55947 : cheapest_safe_inner = cheapest_total_inner;
2370 : else
2371 : cheapest_safe_inner =
2372 219 : get_cheapest_parallel_safe_total_inner(innerrel->pathlist);
2373 :
2374 59410 : if (cheapest_safe_inner != NULL)
2375 56138 : try_partial_hashjoin_path(root, joinrel,
2376 : cheapest_partial_outer,
2377 : cheapest_safe_inner,
2378 : hashclauses, jointype, extra,
2379 : false /* parallel_hash */ );
2380 : }
2381 : }
2382 : }
2383 :
2384 : /*
2385 : * select_mergejoin_clauses
2386 : * Select mergejoin clauses that are usable for a particular join.
2387 : * Returns a list of RestrictInfo nodes for those clauses.
2388 : *
2389 : * *mergejoin_allowed is normally set to true, but it is set to false if
2390 : * this is a right-semi join, or this is a right/right-anti/full join and
2391 : * there are nonmergejoinable join clauses. The executor's mergejoin
2392 : * machinery cannot handle such cases, so we have to avoid generating a
2393 : * mergejoin plan. (Note that this flag does NOT consider whether there are
2394 : * actually any mergejoinable clauses. This is correct because in some
2395 : * cases we need to build a clauseless mergejoin. Simply returning NIL is
2396 : * therefore not enough to distinguish safe from unsafe cases.)
2397 : *
2398 : * We also mark each selected RestrictInfo to show which side is currently
2399 : * being considered as outer. These are transient markings that are only
2400 : * good for the duration of the current add_paths_to_joinrel() call!
2401 : *
2402 : * We examine each restrictinfo clause known for the join to see
2403 : * if it is mergejoinable and involves vars from the two sub-relations
2404 : * currently of interest.
2405 : */
2406 : static List *
2407 553686 : select_mergejoin_clauses(PlannerInfo *root,
2408 : RelOptInfo *joinrel,
2409 : RelOptInfo *outerrel,
2410 : RelOptInfo *innerrel,
2411 : List *restrictlist,
2412 : JoinType jointype,
2413 : bool *mergejoin_allowed)
2414 : {
2415 553686 : List *result_list = NIL;
2416 553686 : bool isouterjoin = IS_OUTER_JOIN(jointype);
2417 553686 : bool have_nonmergeable_joinclause = false;
2418 : ListCell *l;
2419 :
2420 : /*
2421 : * For now we do not support RIGHT_SEMI join in mergejoin: the benefit of
2422 : * swapping inputs tends to be small here.
2423 : */
2424 553686 : if (jointype == JOIN_RIGHT_SEMI)
2425 : {
2426 4830 : *mergejoin_allowed = false;
2427 4830 : return NIL;
2428 : }
2429 :
2430 1166391 : foreach(l, restrictlist)
2431 : {
2432 617535 : RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l);
2433 :
2434 : /*
2435 : * If processing an outer join, only use its own join clauses in the
2436 : * merge. For inner joins we can use pushed-down clauses too. (Note:
2437 : * we don't set have_nonmergeable_joinclause here because pushed-down
2438 : * clauses will become otherquals not joinquals.)
2439 : */
2440 617535 : if (isouterjoin && RINFO_IS_PUSHED_DOWN(restrictinfo, joinrel->relids))
2441 11305 : continue;
2442 :
2443 : /* Check that clause is a mergeable operator clause */
2444 606230 : if (!restrictinfo->can_join ||
2445 552723 : restrictinfo->mergeopfamilies == NIL)
2446 : {
2447 : /*
2448 : * The executor can handle extra joinquals that are constants, but
2449 : * not anything else, when doing right/right-anti/full merge join.
2450 : * (The reason to support constants is so we can do FULL JOIN ON
2451 : * FALSE.)
2452 : */
2453 65435 : if (!restrictinfo->clause || !IsA(restrictinfo->clause, Const))
2454 58577 : have_nonmergeable_joinclause = true;
2455 65435 : continue; /* not mergejoinable */
2456 : }
2457 :
2458 : /*
2459 : * Check if clause has the form "outer op inner" or "inner op outer".
2460 : */
2461 540795 : if (!clause_sides_match_join(restrictinfo, outerrel->relids,
2462 : innerrel->relids))
2463 : {
2464 672 : have_nonmergeable_joinclause = true;
2465 672 : continue; /* no good for these input relations */
2466 : }
2467 :
2468 : /*
2469 : * If clause has the form "inner op outer", check if its operator has
2470 : * valid commutator. This is necessary because mergejoin clauses in
2471 : * this form will get commuted in createplan.c to put the outer var on
2472 : * the left (see get_switched_clauses). This probably shouldn't ever
2473 : * fail, since mergejoinable operators ought to have commutators, but
2474 : * be paranoid.
2475 : *
2476 : * The clause being mergejoinable indicates that it's an OpExpr.
2477 : */
2478 808125 : if (!restrictinfo->outer_is_left &&
2479 268002 : !OidIsValid(get_commutator(castNode(OpExpr, restrictinfo->clause)->opno)))
2480 : {
2481 26 : have_nonmergeable_joinclause = true;
2482 26 : continue;
2483 : }
2484 :
2485 : /*
2486 : * Insist that each side have a non-redundant eclass. This
2487 : * restriction is needed because various bits of the planner expect
2488 : * that each clause in a merge be associable with some pathkey in a
2489 : * canonical pathkey list, but redundant eclasses can't appear in
2490 : * canonical sort orderings. (XXX it might be worth relaxing this,
2491 : * but not enough time to address it for 8.3.)
2492 : */
2493 540097 : update_mergeclause_eclasses(root, restrictinfo);
2494 :
2495 540097 : if (EC_MUST_BE_REDUNDANT(restrictinfo->left_ec) ||
2496 540065 : EC_MUST_BE_REDUNDANT(restrictinfo->right_ec))
2497 : {
2498 84 : have_nonmergeable_joinclause = true;
2499 84 : continue; /* can't handle redundant eclasses */
2500 : }
2501 :
2502 540013 : result_list = lappend(result_list, restrictinfo);
2503 : }
2504 :
2505 : /*
2506 : * Report whether mergejoin is allowed (see comment at top of function).
2507 : */
2508 548856 : switch (jointype)
2509 : {
2510 70633 : case JOIN_RIGHT:
2511 : case JOIN_RIGHT_ANTI:
2512 : case JOIN_FULL:
2513 70633 : *mergejoin_allowed = !have_nonmergeable_joinclause;
2514 70633 : break;
2515 478223 : default:
2516 478223 : *mergejoin_allowed = true;
2517 478223 : break;
2518 : }
2519 :
2520 548856 : return result_list;
2521 : }
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