Age Owner Branch data TLA Line data Source code
1 : : /*-------------------------------------------------------------------------
2 : : *
3 : : * analyzejoins.c
4 : : * Routines for simplifying joins after initial query analysis
5 : : *
6 : : * While we do a great deal of join simplification in prep/prepjointree.c,
7 : : * certain optimizations cannot be performed at that stage for lack of
8 : : * detailed information about the query. The routines here are invoked
9 : : * after initsplan.c has done its work, and can do additional join removal
10 : : * and simplification steps based on the information extracted. The penalty
11 : : * is that we have to work harder to clean up after ourselves when we modify
12 : : * the query, since the derived data structures have to be updated too.
13 : : *
14 : : * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
15 : : * Portions Copyright (c) 1994, Regents of the University of California
16 : : *
17 : : *
18 : : * IDENTIFICATION
19 : : * src/backend/optimizer/plan/analyzejoins.c
20 : : *
21 : : *-------------------------------------------------------------------------
22 : : */
23 : : #include "postgres.h"
24 : :
25 : : #include "catalog/pg_class.h"
26 : : #include "nodes/nodeFuncs.h"
27 : : #include "optimizer/joininfo.h"
28 : : #include "optimizer/optimizer.h"
29 : : #include "optimizer/pathnode.h"
30 : : #include "optimizer/paths.h"
31 : : #include "optimizer/placeholder.h"
32 : : #include "optimizer/planmain.h"
33 : : #include "optimizer/restrictinfo.h"
34 : : #include "parser/parse_agg.h"
35 : : #include "rewrite/rewriteManip.h"
36 : : #include "utils/lsyscache.h"
37 : :
38 : : /*
39 : : * Utility structure. A sorting procedure is needed to simplify the search
40 : : * of SJE-candidate baserels referencing the same database relation. Having
41 : : * collected all baserels from the query jointree, the planner sorts them
42 : : * according to the reloid value, groups them with the next pass and attempts
43 : : * to remove self-joins.
44 : : *
45 : : * Preliminary sorting prevents quadratic behavior that can be harmful in the
46 : : * case of numerous joins.
47 : : */
48 : : typedef struct
49 : : {
50 : : int relid;
51 : : Oid reloid;
52 : : } SelfJoinCandidate;
53 : :
54 : : bool enable_self_join_elimination;
55 : :
56 : : /* local functions */
57 : : static bool join_is_removable(PlannerInfo *root, SpecialJoinInfo *sjinfo);
58 : : static void remove_leftjoinrel_from_query(PlannerInfo *root, int relid,
59 : : SpecialJoinInfo *sjinfo);
60 : : static void remove_rel_from_query(PlannerInfo *root, int relid,
61 : : int subst, SpecialJoinInfo *sjinfo,
62 : : Relids joinrelids);
63 : : static void remove_rel_from_restrictinfo(RestrictInfo *rinfo,
64 : : int relid, int ojrelid);
65 : : static void remove_rel_from_eclass(EquivalenceClass *ec,
66 : : int relid, int ojrelid);
67 : : static List *remove_rel_from_joinlist(List *joinlist, int relid, int *nremoved);
68 : : static bool rel_supports_distinctness(PlannerInfo *root, RelOptInfo *rel);
69 : : static bool rel_is_distinct_for(PlannerInfo *root, RelOptInfo *rel,
70 : : List *clause_list, List **extra_clauses);
71 : : static DistinctColInfo *distinct_col_search(int colno, List *distinct_cols);
72 : : static bool is_innerrel_unique_for(PlannerInfo *root,
73 : : Relids joinrelids,
74 : : Relids outerrelids,
75 : : RelOptInfo *innerrel,
76 : : JoinType jointype,
77 : : List *restrictlist,
78 : : List **extra_clauses);
79 : : static int self_join_candidates_cmp(const void *a, const void *b);
80 : : static bool replace_relid_callback(Node *node,
81 : : ChangeVarNodes_context *context);
82 : :
83 : :
84 : : /*
85 : : * remove_useless_joins
86 : : * Check for relations that don't actually need to be joined at all,
87 : : * and remove them from the query.
88 : : *
89 : : * We are passed the current joinlist and return the updated list. Other
90 : : * data structures that have to be updated are accessible via "root".
91 : : */
92 : : List *
5882 tgl@sss.pgh.pa.us 93 :CBC 255118 : remove_useless_joins(PlannerInfo *root, List *joinlist)
94 : : {
95 : : ListCell *lc;
96 : :
97 : : /*
98 : : * We are only interested in relations that are left-joined to, so we can
99 : : * scan the join_info_list to find them easily.
100 : : */
101 : 263814 : restart:
102 [ + + + + : 299305 : foreach(lc, root->join_info_list)
+ + ]
103 : : {
104 : 44187 : SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);
105 : : int innerrelid;
106 : : int nremoved;
107 : :
108 : : /* Skip if not removable */
109 [ + + ]: 44187 : if (!join_is_removable(root, sjinfo))
110 : 35491 : continue;
111 : :
112 : : /*
113 : : * Currently, join_is_removable can only succeed when the sjinfo's
114 : : * righthand is a single baserel. Remove that rel from the query and
115 : : * joinlist.
116 : : */
117 : 8696 : innerrelid = bms_singleton_member(sjinfo->min_righthand);
118 : :
446 akorotkov@postgresql 119 : 8696 : remove_leftjoinrel_from_query(root, innerrelid, sjinfo);
120 : :
121 : : /* We verify that exactly one reference gets removed from joinlist */
5882 tgl@sss.pgh.pa.us 122 : 8696 : nremoved = 0;
123 : 8696 : joinlist = remove_rel_from_joinlist(joinlist, innerrelid, &nremoved);
124 [ - + ]: 8696 : if (nremoved != 1)
5882 tgl@sss.pgh.pa.us 125 [ # # ]:UBC 0 : elog(ERROR, "failed to find relation %d in joinlist", innerrelid);
126 : :
127 : : /*
128 : : * We can delete this SpecialJoinInfo from the list too, since it's no
129 : : * longer of interest. (Since we'll restart the foreach loop
130 : : * immediately, we don't bother with foreach_delete_current.)
131 : : */
2486 tgl@sss.pgh.pa.us 132 :CBC 8696 : root->join_info_list = list_delete_cell(root->join_info_list, lc);
133 : :
134 : : /*
135 : : * Restart the scan. This is necessary to ensure we find all
136 : : * removable joins independently of ordering of the join_info_list
137 : : * (note that removal of attr_needed bits may make a join appear
138 : : * removable that did not before).
139 : : */
5882 140 : 8696 : goto restart;
141 : : }
142 : :
143 : 255118 : return joinlist;
144 : : }
145 : :
146 : : /*
147 : : * join_is_removable
148 : : * Check whether we need not perform this special join at all, because
149 : : * it will just duplicate its left input.
150 : : *
151 : : * This is true for a left join for which the join condition cannot match
152 : : * more than one inner-side row. (There are other possibly interesting
153 : : * cases, but we don't have the infrastructure to prove them.) We also
154 : : * have to check that the inner side doesn't generate any variables needed
155 : : * above the join.
156 : : */
157 : : static bool
158 : 44187 : join_is_removable(PlannerInfo *root, SpecialJoinInfo *sjinfo)
159 : : {
160 : : int innerrelid;
161 : : RelOptInfo *innerrel;
162 : : Relids inputrelids;
163 : : Relids joinrelids;
164 : 44187 : List *clause_list = NIL;
165 : : ListCell *l;
166 : : int attroff;
167 : :
168 : : /*
169 : : * Must be a left join to a single baserel, else we aren't going to be
170 : : * able to do anything with it.
171 : : */
1191 172 [ + + ]: 44187 : if (sjinfo->jointype != JOIN_LEFT)
4176 173 : 10700 : return false;
174 : :
175 [ + + ]: 33487 : if (!bms_get_singleton_member(sjinfo->min_righthand, &innerrelid))
5882 176 : 1058 : return false;
177 : :
178 : : /*
179 : : * Never try to eliminate a left join to the query result rel. Although
180 : : * the case is syntactically impossible in standard SQL, MERGE will build
181 : : * a join tree that looks exactly like that.
182 : : */
1170 183 [ + + ]: 32429 : if (innerrelid == root->parse->resultRelation)
184 : 636 : return false;
185 : :
5882 186 : 31793 : innerrel = find_base_rel(root, innerrelid);
187 : :
188 : : /*
189 : : * Before we go to the effort of checking whether any innerrel variables
190 : : * are needed above the join, make a quick check to eliminate cases in
191 : : * which we will surely be unable to prove uniqueness of the innerrel.
192 : : */
3680 193 [ + + ]: 31793 : if (!rel_supports_distinctness(root, innerrel))
194 : 2508 : return false;
195 : :
196 : : /* Compute the relid set for the join we are considering */
1082 197 : 29285 : inputrelids = bms_union(sjinfo->min_lefthand, sjinfo->min_righthand);
1186 198 [ - + ]: 29285 : Assert(sjinfo->ojrelid != 0);
199 : 29285 : joinrelids = bms_copy(inputrelids);
200 : 29285 : joinrelids = bms_add_member(joinrelids, sjinfo->ojrelid);
201 : :
202 : : /*
203 : : * We can't remove the join if any inner-rel attributes are used above the
204 : : * join. Here, "above" the join includes pushed-down conditions, so we
205 : : * should reject if attr_needed includes the OJ's own relid; therefore,
206 : : * compare to inputrelids not joinrelids.
207 : : *
208 : : * As a micro-optimization, it seems better to start with max_attr and
209 : : * count down rather than starting with min_attr and counting up, on the
210 : : * theory that the system attributes are somewhat less likely to be wanted
211 : : * and should be tested last.
212 : : */
5882 213 : 29285 : for (attroff = innerrel->max_attr - innerrel->min_attr;
214 [ + + ]: 276354 : attroff >= 0;
215 : 247069 : attroff--)
216 : : {
1186 217 [ + + ]: 267391 : if (!bms_is_subset(innerrel->attr_needed[attroff], inputrelids))
5882 218 : 20322 : return false;
219 : : }
220 : :
221 : : /*
222 : : * Similarly check that the inner rel isn't needed by any PlaceHolderVars
223 : : * that will be used above the join. The PHV case is a little bit more
224 : : * complicated, because PHVs may have been assigned a ph_eval_at location
225 : : * that includes the innerrel, yet their contained expression might not
226 : : * actually reference the innerrel (it could be just a constant, for
227 : : * instance). If such a PHV is due to be evaluated above the join then it
228 : : * needn't prevent join removal.
229 : : */
230 [ + + + + : 9117 : foreach(l, root->placeholder_list)
+ + ]
231 : : {
232 : 184 : PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);
233 : :
4644 234 [ - + ]: 184 : if (bms_overlap(phinfo->ph_lateral, innerrel->relids))
235 : 30 : return false; /* it references innerrel laterally */
5701 236 [ + + ]: 184 : if (!bms_overlap(phinfo->ph_eval_at, innerrel->relids))
237 : 51 : continue; /* it definitely doesn't reference innerrel */
1184 238 [ + + ]: 133 : if (bms_is_subset(phinfo->ph_needed, inputrelids))
239 : 5 : continue; /* PHV is not used above the join */
240 [ + + ]: 128 : if (!bms_is_member(sjinfo->ojrelid, phinfo->ph_eval_at))
241 : 25 : return false; /* it has to be evaluated below the join */
242 : :
243 : : /*
244 : : * We need to be sure there will still be a place to evaluate the PHV
245 : : * if we remove the join, ie that ph_eval_at wouldn't become empty.
246 : : */
247 [ + + ]: 103 : if (!bms_overlap(sjinfo->min_lefthand, phinfo->ph_eval_at))
4644 248 : 5 : return false; /* there isn't any other place to eval PHV */
249 : : /* Check contained expression last, since this is a bit expensive */
1930 250 [ - + ]: 98 : if (bms_overlap(pull_varnos(root, (Node *) phinfo->ph_var->phexpr),
5701 251 : 98 : innerrel->relids))
1184 tgl@sss.pgh.pa.us 252 :UBC 0 : return false; /* contained expression references innerrel */
253 : : }
254 : :
255 : : /*
256 : : * Search for mergejoinable clauses that constrain the inner rel against
257 : : * either the outer rel or a pseudoconstant. If an operator is
258 : : * mergejoinable then it behaves like equality for some btree opclass, so
259 : : * it's what we want. The mergejoinability test also eliminates clauses
260 : : * containing volatile functions, which we couldn't depend on.
261 : : */
5882 tgl@sss.pgh.pa.us 262 [ + + + + :CBC 18029 : foreach(l, innerrel->joininfo)
+ + ]
263 : : {
264 : 9096 : RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l);
265 : :
266 : : /*
267 : : * If the current join commutes with some other outer join(s) via
268 : : * outer join identity 3, there will be multiple clones of its join
269 : : * clauses in the joininfo list. We want to consider only the
270 : : * has_clone form of such clauses. Processing more than one form
271 : : * would be wasteful, and also some of the others would confuse the
272 : : * RINFO_IS_PUSHED_DOWN test below.
273 : : */
1191 274 [ + + ]: 9096 : if (restrictinfo->is_clone)
275 : 82 : continue; /* ignore it */
276 : :
277 : : /*
278 : : * If it's not a join clause for this outer join, we can't use it.
279 : : * Note that if the clause is pushed-down, then it is logically from
280 : : * above the outer join, even if it references no other rels (it might
281 : : * be from WHERE, for example).
282 : : */
2937 283 [ + + + + ]: 9014 : if (RINFO_IS_PUSHED_DOWN(restrictinfo, joinrelids))
1186 284 : 99 : continue; /* ignore; not useful here */
285 : :
286 : : /* Ignore if it's not a mergejoinable clause */
5882 287 [ + + ]: 8915 : if (!restrictinfo->can_join ||
288 [ - + ]: 8769 : restrictinfo->mergeopfamilies == NIL)
289 : 146 : continue; /* not mergejoinable */
290 : :
291 : : /*
292 : : * Check if the clause has the form "outer op inner" or "inner op
293 : : * outer", and if so mark which side is inner.
294 : : */
295 [ + + ]: 8769 : if (!clause_sides_match_join(restrictinfo, sjinfo->min_lefthand,
296 : : innerrel->relids))
297 : 5 : continue; /* no good for these input relations */
298 : :
299 : : /* OK, add to list */
300 : 8764 : clause_list = lappend(clause_list, restrictinfo);
301 : : }
302 : :
303 : : /*
304 : : * Now that we have the relevant equality join clauses, try to prove the
305 : : * innerrel distinct.
306 : : */
446 akorotkov@postgresql 307 [ + + ]: 8933 : if (rel_is_distinct_for(root, innerrel, clause_list, NULL))
3680 tgl@sss.pgh.pa.us 308 : 8696 : return true;
309 : :
310 : : /*
311 : : * Some day it would be nice to check for other methods of establishing
312 : : * distinctness.
313 : : */
5882 314 : 237 : return false;
315 : : }
316 : :
317 : : /*
318 : : * Remove the target relid and references to the target join from the
319 : : * planner's data structures, having determined that there is no need
320 : : * to include them in the query.
321 : : *
322 : : * We are not terribly thorough here. We only bother to update parts of
323 : : * the planner's data structures that will actually be consulted later.
324 : : */
325 : : static void
15 rguo@postgresql.org 326 :GNC 8696 : remove_leftjoinrel_from_query(PlannerInfo *root, int relid,
327 : : SpecialJoinInfo *sjinfo)
328 : : {
329 : 8696 : RelOptInfo *rel = find_base_rel(root, relid);
330 : 8696 : int ojrelid = sjinfo->ojrelid;
331 : : Relids joinrelids;
332 : : Relids join_plus_commute;
333 : : List *joininfos;
334 : : ListCell *l;
335 : :
336 : : /* Compute the relid set for the join we are considering */
337 : 8696 : joinrelids = bms_union(sjinfo->min_lefthand, sjinfo->min_righthand);
338 [ - + ]: 8696 : Assert(ojrelid != 0);
339 : 8696 : joinrelids = bms_add_member(joinrelids, ojrelid);
340 : :
341 : 8696 : remove_rel_from_query(root, relid, -1, sjinfo, joinrelids);
342 : :
343 : : /*
344 : : * Remove any joinquals referencing the rel from the joininfo lists.
345 : : *
346 : : * In some cases, a joinqual has to be put back after deleting its
347 : : * reference to the target rel. This can occur for pseudoconstant and
348 : : * outerjoin-delayed quals, which can get marked as requiring the rel in
349 : : * order to force them to be evaluated at or above the join. We can't
350 : : * just discard them, though. Only quals that logically belonged to the
351 : : * outer join being discarded should be removed from the query.
352 : : *
353 : : * We might encounter a qual that is a clone of a deletable qual with some
354 : : * outer-join relids added (see deconstruct_distribute_oj_quals). To
355 : : * ensure we get rid of such clones as well, add the relids of all OJs
356 : : * commutable with this one to the set we test against for
357 : : * pushed-down-ness.
358 : : */
359 : 8696 : join_plus_commute = bms_union(joinrelids,
360 : 8696 : sjinfo->commute_above_r);
361 : 8696 : join_plus_commute = bms_add_members(join_plus_commute,
362 : 8696 : sjinfo->commute_below_l);
363 : :
364 : : /*
365 : : * We must make a copy of the rel's old joininfo list before starting the
366 : : * loop, because otherwise remove_join_clause_from_rels would destroy the
367 : : * list while we're scanning it.
368 : : */
369 : 8696 : joininfos = list_copy(rel->joininfo);
370 [ + + + + : 17571 : foreach(l, joininfos)
+ + ]
371 : : {
372 : 8875 : RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
373 : :
374 : 8875 : remove_join_clause_from_rels(root, rinfo, rinfo->required_relids);
375 : :
376 [ + + + + ]: 8875 : if (RINFO_IS_PUSHED_DOWN(rinfo, join_plus_commute))
377 : : {
378 : : /*
379 : : * There might be references to relid or ojrelid in the
380 : : * RestrictInfo's relid sets, as a consequence of PHVs having had
381 : : * ph_eval_at sets that include those. We already checked above
382 : : * that any such PHV is safe (and updated its ph_eval_at), so we
383 : : * can just drop those references.
384 : : */
385 : 99 : remove_rel_from_restrictinfo(rinfo, relid, ojrelid);
386 : :
387 : : /*
388 : : * Cross-check that the clause itself does not reference the
389 : : * target rel or join.
390 : : */
391 : : #ifdef USE_ASSERT_CHECKING
392 : : {
393 : 99 : Relids clause_varnos = pull_varnos(root,
394 : 99 : (Node *) rinfo->clause);
395 : :
396 [ - + ]: 99 : Assert(!bms_is_member(relid, clause_varnos));
397 [ - + ]: 99 : Assert(!bms_is_member(ojrelid, clause_varnos));
398 : : }
399 : : #endif
400 : : /* Now throw it back into the joininfo lists */
401 : 99 : distribute_restrictinfo_to_rels(root, rinfo);
402 : : }
403 : : }
404 : :
405 : : /*
406 : : * There may be references to the rel in root->fkey_list, but if so,
407 : : * match_foreign_keys_to_quals() will get rid of them.
408 : : */
409 : :
410 : : /*
411 : : * Now remove the rel from the baserel array to prevent it from being
412 : : * referenced again. (We can't do this earlier because
413 : : * remove_join_clause_from_rels will touch it.)
414 : : */
415 : 8696 : root->simple_rel_array[relid] = NULL;
416 : 8696 : root->simple_rte_array[relid] = NULL;
417 : :
418 : : /* And nuke the RelOptInfo, just in case there's another access path */
419 : 8696 : pfree(rel);
420 : :
421 : : /*
422 : : * Now repeat construction of attr_needed bits coming from all other
423 : : * sources.
424 : : */
425 : 8696 : rebuild_placeholder_attr_needed(root);
426 : 8696 : rebuild_joinclause_attr_needed(root);
427 : 8696 : rebuild_eclass_attr_needed(root);
428 : 8696 : rebuild_lateral_attr_needed(root);
429 : 8696 : }
430 : :
431 : : /*
432 : : * Remove the target relid and references to the target join from the
433 : : * planner's data structures, having determined that there is no need
434 : : * to include them in the query. Optionally replace references to the
435 : : * removed relid with subst if this is a self-join removal.
436 : : *
437 : : * This function serves as the common infrastructure for left-join removal
438 : : * and self-join elimination. It is intentionally scoped to update only the
439 : : * shared planner data structures that are universally affected by relation
440 : : * removal. Each specific caller remains responsible for updating any
441 : : * remaining data structures required by its unique removal logic.
442 : : *
443 : : * The specific type of removal being performed is dictated by the combination
444 : : * of the sjinfo and subst parameters. A non-NULL sjinfo indicates left-join
445 : : * removal. When sjinfo is NULL, a positive subst value indicates self-join
446 : : * elimination (where references are replaced with subst).
447 : : */
448 : : static void
449 : 9164 : remove_rel_from_query(PlannerInfo *root, int relid,
450 : : int subst, SpecialJoinInfo *sjinfo,
451 : : Relids joinrelids)
452 : : {
453 [ + + ]: 9164 : int ojrelid = sjinfo ? sjinfo->ojrelid : 0;
454 : : Index rti;
455 : : ListCell *l;
456 : 9164 : bool is_outer_join = (sjinfo != NULL);
457 [ + + + - ]: 9164 : bool is_self_join = (!is_outer_join && subst > 0);
458 : :
459 [ + + - + ]: 9164 : Assert(is_outer_join || is_self_join);
460 [ + + - + ]: 9164 : Assert(!is_outer_join || ojrelid > 0);
461 [ + + - + ]: 9164 : Assert(!is_outer_join || joinrelids != NULL);
462 : :
463 : : /*
464 : : * Update all_baserels and related relid sets.
465 : : */
446 akorotkov@postgresql 466 :CBC 9164 : root->all_baserels = adjust_relid_set(root->all_baserels, relid, subst);
467 : 9164 : root->all_query_rels = adjust_relid_set(root->all_query_rels, relid, subst);
468 : :
15 rguo@postgresql.org 469 [ + + ]:GNC 9164 : if (is_outer_join)
470 : : {
471 : 8696 : root->outer_join_rels = bms_del_member(root->outer_join_rels, ojrelid);
472 : 8696 : root->all_query_rels = bms_del_member(root->all_query_rels, ojrelid);
473 : : }
474 : :
475 : : /*
476 : : * Likewise remove references from SpecialJoinInfo data structures.
477 : : *
478 : : * This is relevant in case the relation we're deleting is part of the
479 : : * relid sets of special joins: those sets have to be adjusted. If we are
480 : : * removing an outer join, the RHS of the target outer join will be made
481 : : * empty here, but that's OK since the caller will delete that
482 : : * SpecialJoinInfo entirely.
483 : : */
5826 tgl@sss.pgh.pa.us 484 [ + + + + :CBC 21634 : foreach(l, root->join_info_list)
+ + ]
485 : : {
1075 486 : 12470 : SpecialJoinInfo *sjinf = (SpecialJoinInfo *) lfirst(l);
487 : :
488 : : /*
489 : : * initsplan.c is fairly cavalier about allowing SpecialJoinInfos'
490 : : * lefthand/righthand relid sets to be shared with other data
491 : : * structures. Ensure that we don't modify the original relid sets.
492 : : * (The commute_xxx sets are always per-SpecialJoinInfo though.)
493 : : */
726 494 : 12470 : sjinf->min_lefthand = bms_copy(sjinf->min_lefthand);
495 : 12470 : sjinf->min_righthand = bms_copy(sjinf->min_righthand);
496 : 12470 : sjinf->syn_lefthand = bms_copy(sjinf->syn_lefthand);
497 : 12470 : sjinf->syn_righthand = bms_copy(sjinf->syn_righthand);
498 : :
499 : : /* Now adjust relid bit in the sets: */
446 akorotkov@postgresql 500 : 12470 : sjinf->min_lefthand = adjust_relid_set(sjinf->min_lefthand, relid, subst);
501 : 12470 : sjinf->min_righthand = adjust_relid_set(sjinf->min_righthand, relid, subst);
502 : 12470 : sjinf->syn_lefthand = adjust_relid_set(sjinf->syn_lefthand, relid, subst);
503 : 12470 : sjinf->syn_righthand = adjust_relid_set(sjinf->syn_righthand, relid, subst);
504 : :
15 rguo@postgresql.org 505 [ + + ]:GNC 12470 : if (is_outer_join)
506 : : {
507 : : /* Remove ojrelid bit from the sets: */
508 : 12377 : sjinf->min_lefthand = bms_del_member(sjinf->min_lefthand, ojrelid);
509 : 12377 : sjinf->min_righthand = bms_del_member(sjinf->min_righthand, ojrelid);
510 : 12377 : sjinf->syn_lefthand = bms_del_member(sjinf->syn_lefthand, ojrelid);
511 : 12377 : sjinf->syn_righthand = bms_del_member(sjinf->syn_righthand, ojrelid);
512 : : /* relid cannot appear in these fields, but ojrelid can: */
513 : 12377 : sjinf->commute_above_l = bms_del_member(sjinf->commute_above_l, ojrelid);
514 : 12377 : sjinf->commute_above_r = bms_del_member(sjinf->commute_above_r, ojrelid);
515 : 12377 : sjinf->commute_below_l = bms_del_member(sjinf->commute_below_l, ojrelid);
516 : 12377 : sjinf->commute_below_r = bms_del_member(sjinf->commute_below_r, ojrelid);
517 : : }
518 : : else
519 : : {
520 : : /*
521 : : * For self-join removal, replace relid references in
522 : : * semi_rhs_exprs.
523 : : */
363 akorotkov@postgresql 524 :CBC 93 : ChangeVarNodesExtended((Node *) sjinf->semi_rhs_exprs, relid, subst,
525 : : 0, replace_relid_callback);
526 : : }
527 : : }
528 : :
529 : : /*
530 : : * Likewise remove references from PlaceHolderVar data structures,
531 : : * removing any no-longer-needed placeholders entirely. We only remove
532 : : * PHVs for left-join removal. With self-join elimination, PHVs already
533 : : * get moved to the remaining relation, where they might still be needed.
534 : : * It might also happen that we skip the removal of some PHVs that could
535 : : * be removed. However, the overhead of extra PHVs is small compared to
536 : : * the complexity of analysis needed to remove them.
537 : : *
538 : : * Removal is a bit trickier than it might seem: we can remove PHVs that
539 : : * are used at the target rel and/or in the join qual, but not those that
540 : : * are used at join partner rels or above the join. It's not that easy to
541 : : * distinguish PHVs used at partner rels from those used in the join qual,
542 : : * since they will both have ph_needed sets that are subsets of
543 : : * joinrelids. However, a PHV used at a partner rel could not have the
544 : : * target rel in ph_eval_at, so we check that while deciding whether to
545 : : * remove or just update the PHV. There is no corresponding test in
546 : : * join_is_removable because it doesn't need to distinguish those cases.
547 : : */
2486 tgl@sss.pgh.pa.us 548 [ + + + + : 9338 : foreach(l, root->placeholder_list)
+ + ]
549 : : {
5882 550 : 174 : PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);
551 : :
15 rguo@postgresql.org 552 [ + + - + ]:GNC 174 : Assert(!is_outer_join || !bms_is_member(relid, phinfo->ph_lateral));
553 : :
554 [ + + + + ]: 313 : if (is_outer_join &&
372 akorotkov@postgresql 555 [ + + ]:CBC 164 : bms_is_subset(phinfo->ph_needed, joinrelids) &&
1062 tgl@sss.pgh.pa.us 556 : 25 : bms_is_member(relid, phinfo->ph_eval_at) &&
15 rguo@postgresql.org 557 [ + + ]:GNC 10 : !bms_is_member(ojrelid, phinfo->ph_eval_at))
558 : : {
2486 tgl@sss.pgh.pa.us 559 :CBC 5 : root->placeholder_list = foreach_delete_current(root->placeholder_list,
560 : : l);
1357 561 : 5 : root->placeholder_array[phinfo->phid] = NULL;
562 : : }
563 : : else
564 : : {
1182 565 : 169 : PlaceHolderVar *phv = phinfo->ph_var;
566 : :
446 akorotkov@postgresql 567 : 169 : phinfo->ph_eval_at = adjust_relid_set(phinfo->ph_eval_at, relid, subst);
15 rguo@postgresql.org 568 [ + + ]:GNC 169 : if (is_outer_join)
569 : 134 : phinfo->ph_eval_at = bms_del_member(phinfo->ph_eval_at, ojrelid);
1182 tgl@sss.pgh.pa.us 570 [ - + ]:CBC 169 : Assert(!bms_is_empty(phinfo->ph_eval_at)); /* checked previously */
571 : :
572 : : /* Reduce ph_needed to contain only "relation 0"; see below */
585 573 [ + + ]: 169 : if (bms_is_member(0, phinfo->ph_needed))
574 : 92 : phinfo->ph_needed = bms_make_singleton(0);
575 : : else
576 : 77 : phinfo->ph_needed = NULL;
577 : :
446 akorotkov@postgresql 578 :GNC 169 : phv->phrels = adjust_relid_set(phv->phrels, relid, subst);
15 rguo@postgresql.org 579 [ + + ]: 169 : if (is_outer_join)
580 : 134 : phv->phrels = bms_del_member(phv->phrels, ojrelid);
1182 tgl@sss.pgh.pa.us 581 [ - + ]: 169 : Assert(!bms_is_empty(phv->phrels));
582 : :
583 : : /*
584 : : * For self-join removal, update Var nodes within the PHV's
585 : : * expression to reference the replacement relid, and adjust
586 : : * ph_lateral for the relid substitution. (For left-join removal,
587 : : * we're removing rather than replacing, and any surviving PHV
588 : : * shouldn't reference the removed rel in its expression. Also,
589 : : * relid can't appear in ph_lateral for outer joins.)
590 : : */
15 rguo@postgresql.org 591 [ + + ]: 169 : if (is_self_join)
592 : : {
593 : 35 : ChangeVarNodesExtended((Node *) phv->phexpr, relid, subst, 0,
594 : : replace_relid_callback);
595 : 35 : phinfo->ph_lateral = adjust_relid_set(phinfo->ph_lateral, relid, subst);
596 : :
597 : : /*
598 : : * ph_lateral might contain rels mentioned in ph_eval_at after
599 : : * the replacement, remove them.
600 : : */
601 : 35 : phinfo->ph_lateral = bms_difference(phinfo->ph_lateral, phinfo->ph_eval_at);
602 : : /* ph_lateral might or might not be empty */
603 : : }
604 : :
1182 tgl@sss.pgh.pa.us 605 [ - + ]:CBC 169 : Assert(phv->phnullingrels == NULL); /* no need to adjust */
606 : : }
607 : : }
608 : :
609 : : /*
610 : : * Likewise remove references from EquivalenceClasses.
611 : : *
612 : : * For self-join removal, the caller has already updated the
613 : : * EquivalenceClasses, so we can skip this step.
614 : : */
15 rguo@postgresql.org 615 [ + + ]:GNC 9164 : if (is_outer_join)
616 : : {
617 [ + - + + : 49936 : foreach(l, root->eq_classes)
+ + ]
618 : : {
619 : 41240 : EquivalenceClass *ec = (EquivalenceClass *) lfirst(l);
620 : :
621 [ + + - + ]: 70232 : if (bms_is_member(relid, ec->ec_relids) ||
622 : 28992 : bms_is_member(ojrelid, ec->ec_relids))
623 : 12248 : remove_rel_from_eclass(ec, relid, ojrelid);
624 : : }
625 : : }
626 : :
627 : : /*
628 : : * Finally, we must prepare for the caller to recompute per-Var
629 : : * attr_needed and per-PlaceHolderVar ph_needed relid sets. These have to
630 : : * be known accurately, else we may fail to remove other now-removable
631 : : * joins. Because the caller removes the join clause(s) associated with
632 : : * the removed join, Vars that were formerly needed may no longer be.
633 : : *
634 : : * The actual reconstruction of these relid sets is performed by the
635 : : * specific caller. Here, we simply clear out the existing attr_needed
636 : : * sets (we already did this above for ph_needed) to ensure they are
637 : : * rebuilt from scratch. We can cheat to one small extent: we can avoid
638 : : * re-examining the targetlist and HAVING qual by preserving "relation 0"
639 : : * bits from the existing relid sets. This is safe because we'd never
640 : : * remove such references.
641 : : *
642 : : * Additionally, if we are performing self-join elimination, we must
643 : : * replace references to the removed relid with subst within the
644 : : * lateral_vars lists.
645 : : */
446 akorotkov@postgresql 646 [ + + ]:CBC 60474 : for (rti = 1; rti < root->simple_rel_array_size; rti++)
647 : : {
648 : 51310 : RelOptInfo *otherrel = root->simple_rel_array[rti];
649 : : int attroff;
650 : :
651 : : /* there may be empty slots corresponding to non-baserel RTEs */
652 [ + + ]: 51310 : if (otherrel == NULL)
653 : 24950 : continue;
654 : :
655 [ - + ]: 26360 : Assert(otherrel->relid == rti); /* sanity check on array */
656 : :
657 : 26360 : for (attroff = otherrel->max_attr - otherrel->min_attr;
658 [ + + ]: 574706 : attroff >= 0;
659 : 548346 : attroff--)
660 : : {
661 [ + + ]: 548346 : if (bms_is_member(0, otherrel->attr_needed[attroff]))
662 : 38137 : otherrel->attr_needed[attroff] = bms_make_singleton(0);
663 : : else
664 : 510209 : otherrel->attr_needed[attroff] = NULL;
665 : : }
666 : :
15 rguo@postgresql.org 667 [ + + ]:GNC 26360 : if (is_self_join)
363 akorotkov@postgresql 668 :CBC 1209 : ChangeVarNodesExtended((Node *) otherrel->lateral_vars, relid,
669 : : subst, 0, replace_relid_callback);
670 : : }
446 671 : 9164 : }
672 : :
673 : : /*
674 : : * Remove any references to relid or ojrelid from the RestrictInfo.
675 : : *
676 : : * We only bother to clean out bits in the RestrictInfo's various relid sets,
677 : : * not nullingrel bits in contained Vars and PHVs. (This might have to be
678 : : * improved sometime.) However, if the RestrictInfo contains an OR clause
679 : : * we have to also clean up the sub-clauses.
680 : : */
681 : : static void
1180 tgl@sss.pgh.pa.us 682 : 3739 : remove_rel_from_restrictinfo(RestrictInfo *rinfo, int relid, int ojrelid)
683 : : {
684 : : /*
685 : : * initsplan.c is fairly cavalier about allowing RestrictInfos to share
686 : : * relid sets with other RestrictInfos, and SpecialJoinInfos too. Make
687 : : * sure this RestrictInfo has its own relid sets before we modify them.
688 : : * (In present usage, clause_relids is probably not shared, but
689 : : * required_relids could be; let's not assume anything.)
690 : : */
691 : 3739 : rinfo->clause_relids = bms_copy(rinfo->clause_relids);
692 : 3739 : rinfo->clause_relids = bms_del_member(rinfo->clause_relids, relid);
693 : 3739 : rinfo->clause_relids = bms_del_member(rinfo->clause_relids, ojrelid);
694 : : /* Likewise for required_relids */
695 : 3739 : rinfo->required_relids = bms_copy(rinfo->required_relids);
696 : 3739 : rinfo->required_relids = bms_del_member(rinfo->required_relids, relid);
697 : 3739 : rinfo->required_relids = bms_del_member(rinfo->required_relids, ojrelid);
698 : : /* Likewise for incompatible_relids */
15 699 : 3739 : rinfo->incompatible_relids = bms_copy(rinfo->incompatible_relids);
700 : 3739 : rinfo->incompatible_relids = bms_del_member(rinfo->incompatible_relids, relid);
701 : 3739 : rinfo->incompatible_relids = bms_del_member(rinfo->incompatible_relids, ojrelid);
702 : : /* Likewise for outer_relids */
703 : 3739 : rinfo->outer_relids = bms_copy(rinfo->outer_relids);
704 : 3739 : rinfo->outer_relids = bms_del_member(rinfo->outer_relids, relid);
705 : 3739 : rinfo->outer_relids = bms_del_member(rinfo->outer_relids, ojrelid);
706 : : /* Likewise for left_relids */
707 : 3739 : rinfo->left_relids = bms_copy(rinfo->left_relids);
708 : 3739 : rinfo->left_relids = bms_del_member(rinfo->left_relids, relid);
709 : 3739 : rinfo->left_relids = bms_del_member(rinfo->left_relids, ojrelid);
710 : : /* Likewise for right_relids */
711 : 3739 : rinfo->right_relids = bms_copy(rinfo->right_relids);
712 : 3739 : rinfo->right_relids = bms_del_member(rinfo->right_relids, relid);
713 : 3739 : rinfo->right_relids = bms_del_member(rinfo->right_relids, ojrelid);
714 : :
715 : : /* If it's an OR, recurse to clean up sub-clauses */
1180 716 [ + + ]: 3739 : if (restriction_is_or_clause(rinfo))
717 : : {
718 : : ListCell *lc;
719 : :
720 [ - + ]: 5 : Assert(is_orclause(rinfo->orclause));
721 [ + - + + : 15 : foreach(lc, ((BoolExpr *) rinfo->orclause)->args)
+ + ]
722 : : {
723 : 10 : Node *orarg = (Node *) lfirst(lc);
724 : :
725 : : /* OR arguments should be ANDs or sub-RestrictInfos */
726 [ - + ]: 10 : if (is_andclause(orarg))
727 : : {
1180 tgl@sss.pgh.pa.us 728 :UBC 0 : List *andargs = ((BoolExpr *) orarg)->args;
729 : : ListCell *lc2;
730 : :
731 [ # # # # : 0 : foreach(lc2, andargs)
# # ]
732 : : {
733 : 0 : RestrictInfo *rinfo2 = lfirst_node(RestrictInfo, lc2);
734 : :
735 : 0 : remove_rel_from_restrictinfo(rinfo2, relid, ojrelid);
736 : : }
737 : : }
738 : : else
739 : : {
1180 tgl@sss.pgh.pa.us 740 :CBC 10 : RestrictInfo *rinfo2 = castNode(RestrictInfo, orarg);
741 : :
742 : 10 : remove_rel_from_restrictinfo(rinfo2, relid, ojrelid);
743 : : }
744 : : }
745 : : }
746 : 3739 : }
747 : :
748 : : /*
749 : : * Remove any references to relid or ojrelid from the EquivalenceClass.
750 : : *
751 : : * Like remove_rel_from_restrictinfo, we don't worry about cleaning out
752 : : * any nullingrel bits in contained Vars and PHVs. (This might have to be
753 : : * improved sometime.) We do need to fix the EC and EM relid sets to ensure
754 : : * that implied join equalities will be generated at the appropriate join
755 : : * level(s).
756 : : */
757 : : static void
15 rguo@postgresql.org 758 :GNC 12248 : remove_rel_from_eclass(EquivalenceClass *ec, int relid, int ojrelid)
759 : : {
760 : : ListCell *lc;
761 : :
762 : : /* Fix up the EC's overall relids */
763 : 12248 : ec->ec_relids = bms_del_member(ec->ec_relids, relid);
764 : 12248 : ec->ec_relids = bms_del_member(ec->ec_relids, ojrelid);
765 : :
766 : : /*
767 : : * We don't expect any EC child members to exist at this point. Ensure
768 : : * that's the case, otherwise, we might be getting asked to do something
769 : : * this function hasn't been coded for.
770 : : */
392 drowley@postgresql.o 771 [ - + ]:CBC 12248 : Assert(ec->ec_childmembers == NULL);
772 : :
773 : : /*
774 : : * Fix up the member expressions. Any non-const member that ends with
775 : : * empty em_relids must be a Var or PHV of the removed relation. We don't
776 : : * need it anymore, so we can drop it.
777 : : */
1055 tgl@sss.pgh.pa.us 778 [ + + + + : 28126 : foreach(lc, ec->ec_members)
+ + ]
779 : : {
780 : 15878 : EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
781 : :
782 [ + + - + ]: 19508 : if (bms_is_member(relid, cur_em->em_relids) ||
15 rguo@postgresql.org 783 :GNC 3630 : bms_is_member(ojrelid, cur_em->em_relids))
784 : : {
1055 tgl@sss.pgh.pa.us 785 [ - + ]:CBC 12248 : Assert(!cur_em->em_is_const);
786 : : /* em_relids is likely to be shared with some RestrictInfo */
15 tgl@sss.pgh.pa.us 787 :GNC 12248 : cur_em->em_relids = bms_copy(cur_em->em_relids);
rguo@postgresql.org 788 : 12248 : cur_em->em_relids = bms_del_member(cur_em->em_relids, relid);
789 : 12248 : cur_em->em_relids = bms_del_member(cur_em->em_relids, ojrelid);
1055 tgl@sss.pgh.pa.us 790 [ + + ]:CBC 12248 : if (bms_is_empty(cur_em->em_relids))
791 : 12228 : ec->ec_members = foreach_delete_current(ec->ec_members, lc);
792 : : }
793 : : }
794 : :
795 : : /* Fix up the source clauses, in case we can re-use them later */
796 [ + + + + : 15878 : foreach(lc, ec->ec_sources)
+ + ]
797 : : {
798 : 3630 : RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
799 : :
15 rguo@postgresql.org 800 :GNC 3630 : remove_rel_from_restrictinfo(rinfo, relid, ojrelid);
801 : : }
802 : :
803 : : /*
804 : : * Rather than expend code on fixing up any already-derived clauses, just
805 : : * drop them. (At this point, any such clauses would be base restriction
806 : : * clauses, which we'd not need anymore anyway.)
807 : : */
396 amitlan@postgresql.o 808 :CBC 12248 : ec_clear_derived_clauses(ec);
1055 tgl@sss.pgh.pa.us 809 : 12248 : }
810 : :
811 : : /*
812 : : * Remove any occurrences of the target relid from a joinlist structure.
813 : : *
814 : : * It's easiest to build a whole new list structure, so we handle it that
815 : : * way. Efficiency is not a big deal here.
816 : : *
817 : : * *nremoved is incremented by the number of occurrences removed (there
818 : : * should be exactly one, but the caller checks that).
819 : : */
820 : : static List *
5882 821 : 9414 : remove_rel_from_joinlist(List *joinlist, int relid, int *nremoved)
822 : : {
823 : 9414 : List *result = NIL;
824 : : ListCell *jl;
825 : :
826 [ + - + + : 36024 : foreach(jl, joinlist)
+ + ]
827 : : {
828 : 26610 : Node *jlnode = (Node *) lfirst(jl);
829 : :
830 [ + + ]: 26610 : if (IsA(jlnode, RangeTblRef))
831 : : {
832 : 26360 : int varno = ((RangeTblRef *) jlnode)->rtindex;
833 : :
834 [ + + ]: 26360 : if (varno == relid)
835 : 9164 : (*nremoved)++;
836 : : else
837 : 17196 : result = lappend(result, jlnode);
838 : : }
839 [ + - ]: 250 : else if (IsA(jlnode, List))
840 : : {
841 : : /* Recurse to handle subproblem */
842 : : List *sublist;
843 : :
844 : 250 : sublist = remove_rel_from_joinlist((List *) jlnode,
845 : : relid, nremoved);
846 : : /* Avoid including empty sub-lists in the result */
847 [ + - ]: 250 : if (sublist)
848 : 250 : result = lappend(result, sublist);
849 : : }
850 : : else
851 : : {
5882 tgl@sss.pgh.pa.us 852 [ # # ]:UBC 0 : elog(ERROR, "unrecognized joinlist node type: %d",
853 : : (int) nodeTag(jlnode));
854 : : }
855 : : }
856 : :
5882 tgl@sss.pgh.pa.us 857 :CBC 9414 : return result;
858 : : }
859 : :
860 : :
861 : : /*
862 : : * reduce_unique_semijoins
863 : : * Check for semijoins that can be simplified to plain inner joins
864 : : * because the inner relation is provably unique for the join clauses.
865 : : *
866 : : * Ideally this would happen during reduce_outer_joins, but we don't have
867 : : * enough information at that point.
868 : : *
869 : : * To perform the strength reduction when applicable, we need only delete
870 : : * the semijoin's SpecialJoinInfo from root->join_info_list. (We don't
871 : : * bother fixing the join type attributed to it in the query jointree,
872 : : * since that won't be consulted again.)
873 : : */
874 : : void
3291 875 : 255118 : reduce_unique_semijoins(PlannerInfo *root)
876 : : {
877 : : ListCell *lc;
878 : :
879 : : /*
880 : : * Scan the join_info_list to find semijoins.
881 : : */
2486 882 [ + + + + : 290236 : foreach(lc, root->join_info_list)
+ + ]
883 : : {
3291 884 : 35118 : SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);
885 : : int innerrelid;
886 : : RelOptInfo *innerrel;
887 : : Relids joinrelids;
888 : : List *restrictlist;
889 : :
890 : : /*
891 : : * Must be a semijoin to a single baserel, else we aren't going to be
892 : : * able to do anything with it.
893 : : */
1191 894 [ + + ]: 35118 : if (sjinfo->jointype != JOIN_SEMI)
3291 895 : 34881 : continue;
896 : :
897 [ + + ]: 4020 : if (!bms_get_singleton_member(sjinfo->min_righthand, &innerrelid))
898 : 140 : continue;
899 : :
900 : 3880 : innerrel = find_base_rel(root, innerrelid);
901 : :
902 : : /*
903 : : * Before we trouble to run generate_join_implied_equalities, make a
904 : : * quick check to eliminate cases in which we will surely be unable to
905 : : * prove uniqueness of the innerrel.
906 : : */
907 [ + + ]: 3880 : if (!rel_supports_distinctness(root, innerrel))
908 : 801 : continue;
909 : :
910 : : /* Compute the relid set for the join we are considering */
911 : 3079 : joinrelids = bms_union(sjinfo->min_lefthand, sjinfo->min_righthand);
1191 912 [ - + ]: 3079 : Assert(sjinfo->ojrelid == 0); /* SEMI joins don't have RT indexes */
913 : :
914 : : /*
915 : : * Since we're only considering a single-rel RHS, any join clauses it
916 : : * has must be clauses linking it to the semijoin's min_lefthand. We
917 : : * can also consider EC-derived join clauses.
918 : : */
919 : : restrictlist =
3291 920 : 3079 : list_concat(generate_join_implied_equalities(root,
921 : : joinrelids,
922 : : sjinfo->min_lefthand,
923 : : innerrel,
924 : : NULL),
925 : 3079 : innerrel->joininfo);
926 : :
927 : : /* Test whether the innerrel is unique for those clauses. */
2937 928 [ + + ]: 3079 : if (!innerrel_is_unique(root,
929 : : joinrelids, sjinfo->min_lefthand, innerrel,
930 : : JOIN_SEMI, restrictlist, true))
3291 931 : 2842 : continue;
932 : :
933 : : /* OK, remove the SpecialJoinInfo from the list. */
2486 934 : 237 : root->join_info_list = foreach_delete_current(root->join_info_list, lc);
935 : : }
3291 936 : 255118 : }
937 : :
938 : :
939 : : /*
940 : : * rel_supports_distinctness
941 : : * Could the relation possibly be proven distinct on some set of columns?
942 : : *
943 : : * This is effectively a pre-checking function for rel_is_distinct_for().
944 : : * It must return true if rel_is_distinct_for() could possibly return true
945 : : * with this rel, but it should not expend a lot of cycles. The idea is
946 : : * that callers can avoid doing possibly-expensive processing to compute
947 : : * rel_is_distinct_for()'s argument lists if the call could not possibly
948 : : * succeed.
949 : : */
950 : : static bool
3680 951 : 579364 : rel_supports_distinctness(PlannerInfo *root, RelOptInfo *rel)
952 : : {
953 : : /* We only know about baserels ... */
954 [ + + ]: 579364 : if (rel->reloptkind != RELOPT_BASEREL)
955 : 214641 : return false;
956 [ + + ]: 364723 : if (rel->rtekind == RTE_RELATION)
957 : : {
958 : : /*
959 : : * For a plain relation, we only know how to prove uniqueness by
960 : : * reference to unique indexes. Make sure there's at least one
961 : : * suitable unique index. It must be immediately enforced, and not a
962 : : * partial index. (Keep these conditions in sync with
963 : : * relation_has_unique_index_for!)
964 : : */
965 : : ListCell *lc;
966 : :
967 [ + + + + : 451798 : foreach(lc, rel->indexlist)
+ + ]
968 : : {
969 : 391263 : IndexOptInfo *ind = (IndexOptInfo *) lfirst(lc);
970 : :
1051 drowley@postgresql.o 971 [ + + + - : 391263 : if (ind->unique && ind->immediate && ind->indpred == NIL)
+ + ]
3680 tgl@sss.pgh.pa.us 972 : 276433 : return true;
973 : : }
974 : : }
975 [ + + ]: 27755 : else if (rel->rtekind == RTE_SUBQUERY)
976 : : {
977 : 9708 : Query *subquery = root->simple_rte_array[rel->relid]->subquery;
978 : :
979 : : /* Check if the subquery has any qualities that support distinctness */
980 [ + + ]: 9708 : if (query_supports_distinctness(subquery))
981 : 8342 : return true;
982 : : }
983 : : /* We have no proof rules for any other rtekinds. */
984 : 79948 : return false;
985 : : }
986 : :
987 : : /*
988 : : * rel_is_distinct_for
989 : : * Does the relation return only distinct rows according to clause_list?
990 : : *
991 : : * clause_list is a list of join restriction clauses involving this rel and
992 : : * some other one. Return true if no two rows emitted by this rel could
993 : : * possibly join to the same row of the other rel.
994 : : *
995 : : * The caller must have already determined that each condition is a
996 : : * mergejoinable equality with an expression in this relation on one side, and
997 : : * an expression not involving this relation on the other. The transient
998 : : * outer_is_left flag is used to identify which side references this relation:
999 : : * left side if outer_is_left is false, right side if it is true.
1000 : : *
1001 : : * Note that the passed-in clause_list may be destructively modified! This
1002 : : * is OK for current uses, because the clause_list is built by the caller for
1003 : : * the sole purpose of passing to this function.
1004 : : *
1005 : : * (*extra_clauses) to be set to the right sides of baserestrictinfo clauses,
1006 : : * looking like "x = const" if distinctness is derived from such clauses, not
1007 : : * joininfo clauses. Pass NULL to the extra_clauses if this value is not
1008 : : * needed.
1009 : : */
1010 : : static bool
446 akorotkov@postgresql 1011 : 187076 : rel_is_distinct_for(PlannerInfo *root, RelOptInfo *rel, List *clause_list,
1012 : : List **extra_clauses)
1013 : : {
1014 : : /*
1015 : : * We could skip a couple of tests here if we assume all callers checked
1016 : : * rel_supports_distinctness first, but it doesn't seem worth taking any
1017 : : * risk for.
1018 : : */
3680 tgl@sss.pgh.pa.us 1019 [ - + ]: 187076 : if (rel->reloptkind != RELOPT_BASEREL)
3680 tgl@sss.pgh.pa.us 1020 :UBC 0 : return false;
3680 tgl@sss.pgh.pa.us 1021 [ + + ]:CBC 187076 : if (rel->rtekind == RTE_RELATION)
1022 : : {
1023 : : /*
1024 : : * Examine the indexes to see if we have a matching unique index.
1025 : : * relation_has_unique_index_for automatically adds any usable
1026 : : * restriction clauses for the rel, so we needn't do that here.
1027 : : */
259 rguo@postgresql.org 1028 [ + + ]:GNC 182694 : if (relation_has_unique_index_for(root, rel, clause_list, extra_clauses))
3680 tgl@sss.pgh.pa.us 1029 :CBC 107364 : return true;
1030 : : }
1031 [ + - ]: 4382 : else if (rel->rtekind == RTE_SUBQUERY)
1032 : : {
1033 : 4382 : Index relid = rel->relid;
1034 : 4382 : Query *subquery = root->simple_rte_array[relid]->subquery;
0 rguo@postgresql.org 1035 : 4382 : List *distinct_cols = NIL;
1036 : : ListCell *l;
1037 : :
1038 : : /*
1039 : : * Build the argument list for query_is_distinct_for: a list of
1040 : : * DistinctColInfo entries, each holding an output column number that
1041 : : * the query needs to be distinct over, the equality operator that the
1042 : : * column needs to be distinct according to, and that operator's input
1043 : : * collation. The collation matters because the subquery's own
1044 : : * DISTINCT / GROUP BY / set-op proves uniqueness under its own
1045 : : * collation, which need not agree with the operator's.
1046 : : *
1047 : : * (XXX we are not considering restriction clauses attached to the
1048 : : * subquery; is that worth doing?)
1049 : : */
3680 tgl@sss.pgh.pa.us 1050 [ + + + + : 8406 : foreach(l, clause_list)
+ + ]
1051 : : {
3312 1052 : 4024 : RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
1053 : : OpExpr *opexpr;
1054 : : Var *var;
1055 : : DistinctColInfo *dcinfo;
1056 : :
1057 : : /*
1058 : : * The caller's mergejoinability test should have selected only
1059 : : * OpExprs. The operator might be a cross-type operator and thus
1060 : : * not exactly the same operator the subquery would consider;
1061 : : * that's all right since query_is_distinct_for can resolve such
1062 : : * cases.
1063 : : */
0 rguo@postgresql.org 1064 : 4024 : opexpr = castNode(OpExpr, rinfo->clause);
1065 : :
1066 : : /* caller identified the inner side for us */
3680 tgl@sss.pgh.pa.us 1067 [ + + ]: 4024 : if (rinfo->outer_is_left)
1068 : 3663 : var = (Var *) get_rightop(rinfo->clause);
1069 : : else
1070 : 361 : var = (Var *) get_leftop(rinfo->clause);
1071 : :
1072 : : /*
1073 : : * We may ignore any RelabelType node above the operand. (There
1074 : : * won't be more than one, since eval_const_expressions() has been
1075 : : * applied already.)
1076 : : */
3152 1077 [ + - + + ]: 4024 : if (var && IsA(var, RelabelType))
1078 : 2748 : var = (Var *) ((RelabelType *) var)->arg;
1079 : :
1080 : : /*
1081 : : * If inner side isn't a Var referencing a subquery output column,
1082 : : * this clause doesn't help us.
1083 : : */
3680 1084 [ + - + + ]: 4024 : if (!var || !IsA(var, Var) ||
1085 [ + - - + ]: 3999 : var->varno != relid || var->varlevelsup != 0)
1086 : 25 : continue;
1087 : :
0 rguo@postgresql.org 1088 : 3999 : dcinfo = palloc(sizeof(DistinctColInfo));
1089 : 3999 : dcinfo->colno = var->varattno;
1090 : 3999 : dcinfo->opid = opexpr->opno;
1091 : 3999 : dcinfo->collid = opexpr->inputcollid;
1092 : 3999 : distinct_cols = lappend(distinct_cols, dcinfo);
1093 : : }
1094 : :
0 rguo@postgresql.org 1095 [ + + ]:GNC 4382 : if (query_is_distinct_for(subquery, distinct_cols))
3680 tgl@sss.pgh.pa.us 1096 :CBC 563 : return true;
1097 : : }
1098 : 79149 : return false;
1099 : : }
1100 : :
1101 : :
1102 : : /*
1103 : : * query_supports_distinctness - could the query possibly be proven distinct
1104 : : * on some set of output columns?
1105 : : *
1106 : : * This is effectively a pre-checking function for query_is_distinct_for().
1107 : : * It must return true if query_is_distinct_for() could possibly return true
1108 : : * with this query, but it should not expend a lot of cycles. The idea is
1109 : : * that callers can avoid doing possibly-expensive processing to compute
1110 : : * query_is_distinct_for()'s argument lists if the call could not possibly
1111 : : * succeed.
1112 : : */
1113 : : bool
4312 1114 : 9708 : query_supports_distinctness(Query *query)
1115 : : {
1116 : : /* SRFs break distinctness except with DISTINCT, see below */
3083 1117 [ + + + - ]: 9708 : if (query->hasTargetSRFs && query->distinctClause == NIL)
3521 1118 : 763 : return false;
1119 : :
1120 : : /* check for features we can prove distinctness with */
4312 1121 [ + + ]: 8945 : if (query->distinctClause != NIL ||
1122 [ + + ]: 8770 : query->groupClause != NIL ||
4007 andres@anarazel.de 1123 [ + + ]: 8594 : query->groupingSets != NIL ||
4312 tgl@sss.pgh.pa.us 1124 [ + + ]: 8554 : query->hasAggs ||
1125 [ + - ]: 7121 : query->havingQual ||
1126 [ + + ]: 7121 : query->setOperations)
1127 : 8342 : return true;
1128 : :
1129 : 603 : return false;
1130 : : }
1131 : :
1132 : : /*
1133 : : * query_is_distinct_for - does query never return duplicates of the
1134 : : * specified columns?
1135 : : *
1136 : : * query is a not-yet-planned subquery (in current usage, it's always from
1137 : : * a subquery RTE, which the planner avoids scribbling on).
1138 : : *
1139 : : * distinct_cols is a list of DistinctColInfo, one per requested output column.
1140 : : * Each entry names the subquery output column number we want distinct, the
1141 : : * upper-level equality operator we'll compare values with, and that operator's
1142 : : * input collation. We are interested in whether rows consisting of just these
1143 : : * columns are certain to be distinct.
1144 : : *
1145 : : * "Distinctness" is defined according to whether the corresponding upper-level
1146 : : * equality operators would think the values are distinct. (Note: each opid
1147 : : * could be a cross-type operator, and thus not exactly the equality operator
1148 : : * that the subquery would use itself. We use equality_ops_are_compatible() to
1149 : : * check compatibility. That looks at opfamily membership for index AMs that
1150 : : * have declared that they support consistent equality semantics within an
1151 : : * opfamily, and so should give trustworthy answers for all operators that we
1152 : : * might need to deal with here.)
1153 : : *
1154 : : * The collid must also agree on equality with the collation the subquery's own
1155 : : * DISTINCT/GROUP BY/set-op uses to deduplicate the column, else the subquery's
1156 : : * distinctness does not carry over to the caller's equality semantics. Two
1157 : : * collations agree on equality if they match or if both are deterministic (in
1158 : : * which case both reduce equality to byte-equality; see CREATE COLLATION).
1159 : : */
1160 : : bool
0 rguo@postgresql.org 1161 :GNC 4382 : query_is_distinct_for(Query *query, List *distinct_cols)
1162 : : {
1163 : : ListCell *l;
1164 : : DistinctColInfo *dcinfo;
1165 : :
1166 : : /*
1167 : : * DISTINCT (including DISTINCT ON) guarantees uniqueness if all the
1168 : : * columns in the DISTINCT clause appear in colnos and operator semantics
1169 : : * match. This is true even if there are SRFs in the DISTINCT columns or
1170 : : * elsewhere in the tlist.
1171 : : */
4312 tgl@sss.pgh.pa.us 1172 [ + + ]:CBC 4382 : if (query->distinctClause)
1173 : : {
1174 [ + - + + : 180 : foreach(l, query->distinctClause)
+ + ]
1175 : : {
1176 : 145 : SortGroupClause *sgc = (SortGroupClause *) lfirst(l);
1177 : 145 : TargetEntry *tle = get_sortgroupclause_tle(sgc,
1178 : : query->targetList);
1179 : :
0 rguo@postgresql.org 1180 : 145 : dcinfo = distinct_col_search(tle->resno, distinct_cols);
1181 [ + + ]: 145 : if (dcinfo == NULL ||
1182 [ + - ]: 90 : !equality_ops_are_compatible(dcinfo->opid, sgc->eqop) ||
1183 [ + + ]: 90 : !collations_agree_on_equality(dcinfo->collid,
1184 : 90 : exprCollation((Node *) tle->expr)))
1185 : : break; /* exit early if no match */
1186 : : }
4312 tgl@sss.pgh.pa.us 1187 [ + + ]: 130 : if (l == NULL) /* had matches for all? */
1188 : 35 : return true;
1189 : : }
1190 : :
1191 : : /*
1192 : : * Otherwise, a set-returning function in the query's targetlist can
1193 : : * result in returning duplicate rows, despite any grouping that might
1194 : : * occur before tlist evaluation. (If all tlist SRFs are within GROUP BY
1195 : : * columns, it would be safe because they'd be expanded before grouping.
1196 : : * But it doesn't currently seem worth the effort to check for that.)
1197 : : */
3083 1198 [ - + ]: 4347 : if (query->hasTargetSRFs)
3083 tgl@sss.pgh.pa.us 1199 :UBC 0 : return false;
1200 : :
1201 : : /*
1202 : : * Similarly, GROUP BY without GROUPING SETS guarantees uniqueness if all
1203 : : * the grouped columns appear in colnos and operator semantics match.
1204 : : */
4007 andres@anarazel.de 1205 [ + + + + ]:CBC 4347 : if (query->groupClause && !query->groupingSets)
1206 : : {
4312 tgl@sss.pgh.pa.us 1207 [ + - + + : 206 : foreach(l, query->groupClause)
+ + ]
1208 : : {
1209 : 144 : SortGroupClause *sgc = (SortGroupClause *) lfirst(l);
1210 : 144 : TargetEntry *tle = get_sortgroupclause_tle(sgc,
1211 : : query->targetList);
1212 : :
0 rguo@postgresql.org 1213 : 144 : dcinfo = distinct_col_search(tle->resno, distinct_cols);
1214 [ + + ]: 144 : if (dcinfo == NULL ||
1215 [ + - ]: 107 : !equality_ops_are_compatible(dcinfo->opid, sgc->eqop) ||
1216 [ + + ]: 107 : !collations_agree_on_equality(dcinfo->collid,
1217 : 107 : exprCollation((Node *) tle->expr)))
1218 : : break; /* exit early if no match */
1219 : : }
4312 tgl@sss.pgh.pa.us 1220 [ + + ]: 109 : if (l == NULL) /* had matches for all? */
1221 : 62 : return true;
1222 : : }
4007 andres@anarazel.de 1223 [ + + ]: 4238 : else if (query->groupingSets)
1224 : : {
1225 : : List *gsets;
1226 : :
1227 : : /*
1228 : : * If we have grouping sets with expressions, we probably don't have
1229 : : * uniqueness and analysis would be hard. Punt.
1230 : : */
4007 andres@anarazel.de 1231 [ + + ]:GBC 50 : if (query->groupClause)
1232 : 10 : return false;
1233 : :
1234 : : /*
1235 : : * If we have no groupClause (therefore no grouping expressions), we
1236 : : * might have one or many empty grouping sets. If there's just one,
1237 : : * or if the DISTINCT clause is used on the GROUP BY, then we're
1238 : : * returning only one row and are certainly unique. But otherwise, we
1239 : : * know we're certainly not unique.
1240 : : */
147 rguo@postgresql.org 1241 [ + + ]:GNC 40 : if (query->groupDistinct)
4007 andres@anarazel.de 1242 :GBC 5 : return true;
1243 : :
147 rguo@postgresql.org 1244 :GNC 35 : gsets = expand_grouping_sets(query->groupingSets, false, -1);
1245 : :
1246 : 35 : return (list_length(gsets) == 1);
1247 : : }
1248 : : else
1249 : : {
1250 : : /*
1251 : : * If we have no GROUP BY, but do have aggregates or HAVING, then the
1252 : : * result is at most one row so it's surely unique, for any operators.
1253 : : */
4312 tgl@sss.pgh.pa.us 1254 [ + + - + ]:CBC 4188 : if (query->hasAggs || query->havingQual)
1255 : 396 : return true;
1256 : : }
1257 : :
1258 : : /*
1259 : : * UNION, INTERSECT, EXCEPT guarantee uniqueness of the whole output row,
1260 : : * except with ALL.
1261 : : */
1262 [ + + ]: 3839 : if (query->setOperations)
1263 : : {
3360 peter_e@gmx.net 1264 : 3697 : SetOperationStmt *topop = castNode(SetOperationStmt, query->setOperations);
1265 : :
4312 tgl@sss.pgh.pa.us 1266 [ - + ]: 3697 : Assert(topop->op != SETOP_NONE);
1267 : :
1268 [ + + ]: 3697 : if (!topop->all)
1269 : : {
1270 : : ListCell *lg;
1271 : :
1272 : : /* We're good if all the nonjunk output columns are in colnos */
1273 : 93 : lg = list_head(topop->groupClauses);
1274 [ + - + + : 148 : foreach(l, query->targetList)
+ + ]
1275 : : {
1276 : 98 : TargetEntry *tle = (TargetEntry *) lfirst(l);
1277 : : SortGroupClause *sgc;
1278 : :
1279 [ - + ]: 98 : if (tle->resjunk)
4312 tgl@sss.pgh.pa.us 1280 :UBC 0 : continue; /* ignore resjunk columns */
1281 : :
1282 : : /* non-resjunk columns should have grouping clauses */
4312 tgl@sss.pgh.pa.us 1283 [ - + ]:CBC 98 : Assert(lg != NULL);
1284 : 98 : sgc = (SortGroupClause *) lfirst(lg);
2486 1285 : 98 : lg = lnext(topop->groupClauses, lg);
1286 : :
0 rguo@postgresql.org 1287 : 98 : dcinfo = distinct_col_search(tle->resno, distinct_cols);
1288 [ + + ]: 98 : if (dcinfo == NULL ||
1289 [ + - ]: 65 : !equality_ops_are_compatible(dcinfo->opid, sgc->eqop) ||
1290 [ + + ]: 65 : !collations_agree_on_equality(dcinfo->collid,
1291 : 65 : exprCollation((Node *) tle->expr)))
1292 : : break; /* exit early if no match */
1293 : : }
4312 tgl@sss.pgh.pa.us 1294 [ + + ]: 93 : if (l == NULL) /* had matches for all? */
1295 : 50 : return true;
1296 : : }
1297 : : }
1298 : :
1299 : : /*
1300 : : * XXX Are there any other cases in which we can easily see the result
1301 : : * must be distinct?
1302 : : *
1303 : : * If you do add more smarts to this function, be sure to update
1304 : : * query_supports_distinctness() to match.
1305 : : */
1306 : :
1307 : 3789 : return false;
1308 : : }
1309 : :
1310 : : /*
1311 : : * distinct_col_search - subroutine for query_is_distinct_for
1312 : : *
1313 : : * If colno matches the colno field of an entry in distinct_cols, return a
1314 : : * pointer to that entry; else return NULL. (Ordinarily distinct_cols would
1315 : : * not contain duplicate colnos, but if it does, we arbitrarily select the
1316 : : * first match.)
1317 : : */
1318 : : static DistinctColInfo *
0 rguo@postgresql.org 1319 : 387 : distinct_col_search(int colno, List *distinct_cols)
1320 : : {
1321 [ + - + + : 655 : foreach_ptr(DistinctColInfo, dcinfo, distinct_cols)
+ + ]
1322 : : {
1323 [ + + ]: 405 : if (dcinfo->colno == colno)
1324 : 262 : return dcinfo;
1325 : : }
1326 : :
1327 : 125 : return NULL;
1328 : : }
1329 : :
1330 : :
1331 : : /*
1332 : : * innerrel_is_unique
1333 : : * Check if the innerrel provably contains at most one tuple matching any
1334 : : * tuple from the outerrel, based on join clauses in the 'restrictlist'.
1335 : : *
1336 : : * We need an actual RelOptInfo for the innerrel, but it's sufficient to
1337 : : * identify the outerrel by its Relids. This asymmetry supports use of this
1338 : : * function before joinrels have been built. (The caller is expected to
1339 : : * also supply the joinrelids, just to save recalculating that.)
1340 : : *
1341 : : * The proof must be made based only on clauses that will be "joinquals"
1342 : : * rather than "otherquals" at execution. For an inner join there's no
1343 : : * difference; but if the join is outer, we must ignore pushed-down quals,
1344 : : * as those will become "otherquals". Note that this means the answer might
1345 : : * vary depending on whether IS_OUTER_JOIN(jointype); since we cache the
1346 : : * answer without regard to that, callers must take care not to call this
1347 : : * with jointypes that would be classified differently by IS_OUTER_JOIN().
1348 : : *
1349 : : * The actual proof is undertaken by is_innerrel_unique_for(); this function
1350 : : * is a frontend that is mainly concerned with caching the answers.
1351 : : * In particular, the force_cache argument allows overriding the internal
1352 : : * heuristic about whether to cache negative answers; it should be "true"
1353 : : * if making an inquiry that is not part of the normal bottom-up join search
1354 : : * sequence.
1355 : : */
1356 : : bool
3315 tgl@sss.pgh.pa.us 1357 : 620991 : innerrel_is_unique(PlannerInfo *root,
1358 : : Relids joinrelids,
1359 : : Relids outerrelids,
1360 : : RelOptInfo *innerrel,
1361 : : JoinType jointype,
1362 : : List *restrictlist,
1363 : : bool force_cache)
1364 : : {
446 akorotkov@postgresql 1365 : 620991 : return innerrel_is_unique_ext(root, joinrelids, outerrelids, innerrel,
1366 : : jointype, restrictlist, force_cache, NULL);
1367 : : }
1368 : :
1369 : : /*
1370 : : * innerrel_is_unique_ext
1371 : : * Do the same as innerrel_is_unique(), but also set to (*extra_clauses)
1372 : : * additional clauses from a baserestrictinfo list used to prove the
1373 : : * uniqueness.
1374 : : *
1375 : : * A non-NULL extra_clauses indicates that we're checking for self-join and
1376 : : * correspondingly dealing with filtered clauses.
1377 : : */
1378 : : bool
1379 : 622782 : innerrel_is_unique_ext(PlannerInfo *root,
1380 : : Relids joinrelids,
1381 : : Relids outerrelids,
1382 : : RelOptInfo *innerrel,
1383 : : JoinType jointype,
1384 : : List *restrictlist,
1385 : : bool force_cache,
1386 : : List **extra_clauses)
1387 : : {
1388 : : MemoryContext old_context;
1389 : : ListCell *lc;
1390 : : UniqueRelInfo *uniqueRelInfo;
1391 : 622782 : List *outer_exprs = NIL;
1392 : 622782 : bool self_join = (extra_clauses != NULL);
1393 : :
1394 : : /* Certainly can't prove uniqueness when there are no joinclauses */
3315 tgl@sss.pgh.pa.us 1395 [ + + ]: 622782 : if (restrictlist == NIL)
1396 : 79091 : return false;
1397 : :
1398 : : /*
1399 : : * Make a quick check to eliminate cases in which we will surely be unable
1400 : : * to prove uniqueness of the innerrel.
1401 : : */
1402 [ + + ]: 543691 : if (!rel_supports_distinctness(root, innerrel))
1403 : 291280 : return false;
1404 : :
1405 : : /*
1406 : : * Query the cache to see if we've managed to prove that innerrel is
1407 : : * unique for any subset of this outerrel. For non-self-join search, we
1408 : : * don't need an exact match, as extra outerrels can't make the innerrel
1409 : : * any less unique (or more formally, the restrictlist for a join to a
1410 : : * superset outerrel must be a superset of the conditions we successfully
1411 : : * used before). For self-join search, we require an exact match of
1412 : : * outerrels because we need extra clauses to be valid for our case. Also,
1413 : : * for self-join checking we've filtered the clauses list. Thus, we can
1414 : : * match only the result cached for a self-join search for another
1415 : : * self-join check.
1416 : : */
1417 [ + + + + : 275468 : foreach(lc, innerrel->unique_for_rels)
+ + ]
1418 : : {
446 akorotkov@postgresql 1419 : 96977 : uniqueRelInfo = (UniqueRelInfo *) lfirst(lc);
1420 : :
1421 [ + + + + : 96977 : if ((!self_join && bms_is_subset(uniqueRelInfo->outerrelids, outerrelids)) ||
+ + ]
1422 [ + + ]: 57 : (self_join && bms_equal(uniqueRelInfo->outerrelids, outerrelids) &&
1423 [ + + ]: 42 : uniqueRelInfo->self_join))
1424 : : {
1425 [ + + ]: 73920 : if (extra_clauses)
1426 : 10 : *extra_clauses = uniqueRelInfo->extra_clauses;
3315 tgl@sss.pgh.pa.us 1427 : 73920 : return true; /* Success! */
1428 : : }
1429 : : }
1430 : :
1431 : : /*
1432 : : * Conversely, we may have already determined that this outerrel, or some
1433 : : * superset thereof, cannot prove this innerrel to be unique.
1434 : : */
1435 [ + + + + : 179027 : foreach(lc, innerrel->non_unique_for_rels)
+ + ]
1436 : : {
1437 : 884 : Relids unique_for_rels = (Relids) lfirst(lc);
1438 : :
3291 1439 [ + + ]: 884 : if (bms_is_subset(outerrelids, unique_for_rels))
3315 1440 : 348 : return false;
1441 : : }
1442 : :
1443 : : /* No cached information, so try to make the proof. */
2937 1444 [ + + + + ]: 178143 : if (is_innerrel_unique_for(root, joinrelids, outerrelids, innerrel,
1445 : : jointype, restrictlist,
1446 : : self_join ? &outer_exprs : NULL))
1447 : : {
1448 : : /*
1449 : : * Cache the positive result for future probes, being sure to keep it
1450 : : * in the planner_cxt even if we are working in GEQO.
1451 : : *
1452 : : * Note: one might consider trying to isolate the minimal subset of
1453 : : * the outerrels that proved the innerrel unique. But it's not worth
1454 : : * the trouble, because the planner builds up joinrels incrementally
1455 : : * and so we'll see the minimally sufficient outerrels before any
1456 : : * supersets of them anyway.
1457 : : */
3315 1458 : 99231 : old_context = MemoryContextSwitchTo(root->planner_cxt);
446 akorotkov@postgresql 1459 : 99231 : uniqueRelInfo = makeNode(UniqueRelInfo);
1460 : 99231 : uniqueRelInfo->outerrelids = bms_copy(outerrelids);
1461 : 99231 : uniqueRelInfo->self_join = self_join;
1462 : 99231 : uniqueRelInfo->extra_clauses = outer_exprs;
3315 tgl@sss.pgh.pa.us 1463 : 99231 : innerrel->unique_for_rels = lappend(innerrel->unique_for_rels,
1464 : : uniqueRelInfo);
1465 : 99231 : MemoryContextSwitchTo(old_context);
1466 : :
446 akorotkov@postgresql 1467 [ + + ]: 99231 : if (extra_clauses)
1468 : 513 : *extra_clauses = outer_exprs;
3315 tgl@sss.pgh.pa.us 1469 : 99231 : return true; /* Success! */
1470 : : }
1471 : : else
1472 : : {
1473 : : /*
1474 : : * None of the join conditions for outerrel proved innerrel unique, so
1475 : : * we can safely reject this outerrel or any subset of it in future
1476 : : * checks.
1477 : : *
1478 : : * However, in normal planning mode, caching this knowledge is totally
1479 : : * pointless; it won't be queried again, because we build up joinrels
1480 : : * from smaller to larger. It's only useful when using GEQO or
1481 : : * another planner extension that attempts planning multiple times.
1482 : : *
1483 : : * Also, allow callers to override that heuristic and force caching;
1484 : : * that's useful for reduce_unique_semijoins, which calls here before
1485 : : * the normal join search starts.
1486 : : */
258 rhaas@postgresql.org 1487 [ + + - + ]:GNC 78912 : if (force_cache || root->assumeReplanning)
1488 : : {
3315 tgl@sss.pgh.pa.us 1489 :CBC 3190 : old_context = MemoryContextSwitchTo(root->planner_cxt);
1490 : 3190 : innerrel->non_unique_for_rels =
1491 : 3190 : lappend(innerrel->non_unique_for_rels,
3291 1492 : 3190 : bms_copy(outerrelids));
3315 1493 : 3190 : MemoryContextSwitchTo(old_context);
1494 : : }
1495 : :
1496 : 78912 : return false;
1497 : : }
1498 : : }
1499 : :
1500 : : /*
1501 : : * is_innerrel_unique_for
1502 : : * Check if the innerrel provably contains at most one tuple matching any
1503 : : * tuple from the outerrel, based on join clauses in the 'restrictlist'.
1504 : : */
1505 : : static bool
1506 : 178143 : is_innerrel_unique_for(PlannerInfo *root,
1507 : : Relids joinrelids,
1508 : : Relids outerrelids,
1509 : : RelOptInfo *innerrel,
1510 : : JoinType jointype,
1511 : : List *restrictlist,
1512 : : List **extra_clauses)
1513 : : {
1514 : 178143 : List *clause_list = NIL;
1515 : : ListCell *lc;
1516 : :
1517 : : /*
1518 : : * Search for mergejoinable clauses that constrain the inner rel against
1519 : : * the outer rel. If an operator is mergejoinable then it behaves like
1520 : : * equality for some btree opclass, so it's what we want. The
1521 : : * mergejoinability test also eliminates clauses containing volatile
1522 : : * functions, which we couldn't depend on.
1523 : : */
1524 [ + - + + : 399616 : foreach(lc, restrictlist)
+ + ]
1525 : : {
1526 : 221473 : RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc);
1527 : :
1528 : : /*
1529 : : * As noted above, if it's a pushed-down clause and we're at an outer
1530 : : * join, we can't use it.
1531 : : */
2937 1532 [ + + ]: 221473 : if (IS_OUTER_JOIN(jointype) &&
1533 [ + + - + ]: 88694 : RINFO_IS_PUSHED_DOWN(restrictinfo, joinrelids))
3315 1534 : 8048 : continue;
1535 : :
1536 : : /* Ignore if it's not a mergejoinable clause */
1537 [ + + ]: 213425 : if (!restrictinfo->can_join ||
1538 [ + + ]: 200178 : restrictinfo->mergeopfamilies == NIL)
1539 : 13949 : continue; /* not mergejoinable */
1540 : :
1541 : : /*
1542 : : * Check if the clause has the form "outer op inner" or "inner op
1543 : : * outer", and if so mark which side is inner.
1544 : : */
3291 1545 [ + + ]: 199476 : if (!clause_sides_match_join(restrictinfo, outerrelids,
1546 : : innerrel->relids))
3315 1547 : 20 : continue; /* no good for these input relations */
1548 : :
1549 : : /* OK, add to the list */
1550 : 199456 : clause_list = lappend(clause_list, restrictinfo);
1551 : : }
1552 : :
1553 : : /* Let rel_is_distinct_for() do the hard work */
446 akorotkov@postgresql 1554 : 178143 : return rel_is_distinct_for(root, innerrel, clause_list, extra_clauses);
1555 : : }
1556 : :
1557 : : /*
1558 : : * Update EC members to point to the remaining relation instead of the removed
1559 : : * one, removing duplicates.
1560 : : *
1561 : : * Restriction clauses for base relations are already distributed to
1562 : : * the respective baserestrictinfo lists (see
1563 : : * generate_implied_equalities_for_column). The above code has already processed
1564 : : * this list and updated these clauses to reference the remaining
1565 : : * relation, so that we can skip them here based on their relids.
1566 : : *
1567 : : * Likewise, we have already processed the join clauses that join the
1568 : : * removed relation to the remaining one.
1569 : : *
1570 : : * Finally, there might be join clauses tying the removed relation to
1571 : : * some third relation. We can't just delete the source clauses and
1572 : : * regenerate them from the EC because the corresponding equality
1573 : : * operators might be missing (see the handling of ec_broken).
1574 : : * Therefore, we will update the references in the source clauses.
1575 : : *
1576 : : * Derived clauses can be generated again, so it is simpler just to
1577 : : * delete them.
1578 : : */
1579 : : static void
1580 : 751 : update_eclasses(EquivalenceClass *ec, int from, int to)
1581 : : {
1582 : 751 : List *new_members = NIL;
1583 : 751 : List *new_sources = NIL;
1584 : :
1585 : : /*
1586 : : * We don't expect any EC child members to exist at this point. Ensure
1587 : : * that's the case, otherwise, we might be getting asked to do something
1588 : : * this function hasn't been coded for.
1589 : : */
392 drowley@postgresql.o 1590 [ - + ]: 751 : Assert(ec->ec_childmembers == NULL);
1591 : :
446 akorotkov@postgresql 1592 [ + - + + : 3076 : foreach_node(EquivalenceMember, em, ec->ec_members)
+ + ]
1593 : : {
1594 : 1574 : bool is_redundant = false;
1595 : :
1596 [ + + ]: 1574 : if (!bms_is_member(from, em->em_relids))
1597 : : {
1598 : 808 : new_members = lappend(new_members, em);
1599 : 808 : continue;
1600 : : }
1601 : :
1602 : 766 : em->em_relids = adjust_relid_set(em->em_relids, from, to);
1603 : 766 : em->em_jdomain->jd_relids = adjust_relid_set(em->em_jdomain->jd_relids, from, to);
1604 : :
1605 : : /* We only process inner joins */
363 1606 : 766 : ChangeVarNodesExtended((Node *) em->em_expr, from, to, 0,
1607 : : replace_relid_callback);
1608 : :
446 1609 [ + + + + : 1552 : foreach_node(EquivalenceMember, other, new_members)
+ + ]
1610 : : {
1611 [ + + ]: 186 : if (!equal(em->em_relids, other->em_relids))
1612 : 20 : continue;
1613 : :
1614 [ + - ]: 166 : if (equal(em->em_expr, other->em_expr))
1615 : : {
1616 : 166 : is_redundant = true;
1617 : 166 : break;
1618 : : }
1619 : : }
1620 : :
1621 [ + + ]: 766 : if (!is_redundant)
1622 : 600 : new_members = lappend(new_members, em);
1623 : : }
1624 : :
1625 : 751 : list_free(ec->ec_members);
1626 : 751 : ec->ec_members = new_members;
1627 : :
396 amitlan@postgresql.o 1628 : 751 : ec_clear_derived_clauses(ec);
1629 : :
1630 : : /* Update EC source expressions */
446 akorotkov@postgresql 1631 [ + + + + : 2325 : foreach_node(RestrictInfo, rinfo, ec->ec_sources)
+ + ]
1632 : : {
1633 : 823 : bool is_redundant = false;
1634 : :
1635 [ + + ]: 823 : if (!bms_is_member(from, rinfo->required_relids))
1636 : : {
1637 : 160 : new_sources = lappend(new_sources, rinfo);
1638 : 160 : continue;
1639 : : }
1640 : :
363 1641 : 663 : ChangeVarNodesExtended((Node *) rinfo, from, to, 0,
1642 : : replace_relid_callback);
1643 : :
1644 : : /*
1645 : : * After switching the clause to the remaining relation, check it for
1646 : : * redundancy with existing ones. We don't have to check for
1647 : : * redundancy with derived clauses, because we've just deleted them.
1648 : : */
446 1649 [ + + + + : 1338 : foreach_node(RestrictInfo, other, new_sources)
+ + ]
1650 : : {
1651 [ + + ]: 22 : if (!equal(rinfo->clause_relids, other->clause_relids))
1652 : 12 : continue;
1653 : :
1654 [ + - ]: 10 : if (equal(rinfo->clause, other->clause))
1655 : : {
1656 : 10 : is_redundant = true;
1657 : 10 : break;
1658 : : }
1659 : : }
1660 : :
1661 [ + + ]: 663 : if (!is_redundant)
1662 : 653 : new_sources = lappend(new_sources, rinfo);
1663 : : }
1664 : :
1665 : 751 : list_free(ec->ec_sources);
1666 : 751 : ec->ec_sources = new_sources;
1667 : 751 : ec->ec_relids = adjust_relid_set(ec->ec_relids, from, to);
1668 : 751 : }
1669 : :
1670 : : /*
1671 : : * "Logically" compares two RestrictInfo's ignoring the 'rinfo_serial' field,
1672 : : * which makes almost every RestrictInfo unique. This type of comparison is
1673 : : * useful when removing duplicates while moving RestrictInfo's from removed
1674 : : * relation to remaining relation during self-join elimination.
1675 : : *
1676 : : * XXX: In the future, we might remove the 'rinfo_serial' field completely and
1677 : : * get rid of this function.
1678 : : */
1679 : : static bool
1680 : 476 : restrict_infos_logically_equal(RestrictInfo *a, RestrictInfo *b)
1681 : : {
1682 : 476 : int saved_rinfo_serial = a->rinfo_serial;
1683 : : bool result;
1684 : :
1685 : 476 : a->rinfo_serial = b->rinfo_serial;
1686 : 476 : result = equal(a, b);
1687 : 476 : a->rinfo_serial = saved_rinfo_serial;
1688 : :
1689 : 476 : return result;
1690 : : }
1691 : :
1692 : : /*
1693 : : * This function adds all non-redundant clauses to the keeping relation
1694 : : * during self-join elimination. That is a contradictory operation. On the
1695 : : * one hand, we reduce the length of the `restrict` lists, which can
1696 : : * impact planning or executing time. Additionally, we improve the
1697 : : * accuracy of cardinality estimation. On the other hand, it is one more
1698 : : * place that can make planning time much longer in specific cases. It
1699 : : * would have been better to avoid calling the equal() function here, but
1700 : : * it's the only way to detect duplicated inequality expressions.
1701 : : *
1702 : : * (*keep_rinfo_list) is given by pointer because it might be altered by
1703 : : * distribute_restrictinfo_to_rels().
1704 : : */
1705 : : static void
1706 : 936 : add_non_redundant_clauses(PlannerInfo *root,
1707 : : List *rinfo_candidates,
1708 : : List **keep_rinfo_list,
1709 : : Index removed_relid)
1710 : : {
1711 [ + + + + : 2652 : foreach_node(RestrictInfo, rinfo, rinfo_candidates)
+ + ]
1712 : : {
1713 : 780 : bool is_redundant = false;
1714 : :
1715 [ - + ]: 780 : Assert(!bms_is_member(removed_relid, rinfo->required_relids));
1716 : :
1717 [ + + + + : 1939 : foreach_node(RestrictInfo, src, (*keep_rinfo_list))
+ + ]
1718 : : {
1719 [ + + ]: 496 : if (!bms_equal(src->clause_relids, rinfo->clause_relids))
1720 : : /* Can't compare trivially different clauses */
1721 : 15 : continue;
1722 : :
1723 [ + - ]: 481 : if (src == rinfo ||
1724 [ + + ]: 481 : (rinfo->parent_ec != NULL &&
1725 [ + + + + ]: 790 : src->parent_ec == rinfo->parent_ec) ||
1726 : 476 : restrict_infos_logically_equal(rinfo, src))
1727 : : {
1728 : 117 : is_redundant = true;
1729 : 117 : break;
1730 : : }
1731 : : }
1732 [ + + ]: 780 : if (!is_redundant)
1733 : 663 : distribute_restrictinfo_to_rels(root, rinfo);
1734 : : }
1735 : 936 : }
1736 : :
1737 : : /*
1738 : : * A custom callback for ChangeVarNodesExtended() providing Self-join
1739 : : * elimination (SJE) related functionality
1740 : : *
1741 : : * SJE needs to skip the RangeTblRef node type. During SJE's last
1742 : : * step, remove_rel_from_joinlist() removes remaining RangeTblRefs
1743 : : * with target relid. If ChangeVarNodes() replaces the target relid
1744 : : * before, remove_rel_from_joinlist() would fail to identify the nodes
1745 : : * to delete.
1746 : : *
1747 : : * SJE also needs to change the relids within RestrictInfo's.
1748 : : */
1749 : : static bool
363 1750 : 30676 : replace_relid_callback(Node *node, ChangeVarNodes_context *context)
1751 : : {
1752 [ + + ]: 30676 : if (IsA(node, RangeTblRef))
1753 : : {
1754 : 1249 : return true;
1755 : : }
1756 [ + + ]: 29427 : else if (IsA(node, RestrictInfo))
1757 : : {
1758 : 1463 : RestrictInfo *rinfo = (RestrictInfo *) node;
1759 : 1463 : int relid = -1;
1760 : 1463 : bool is_req_equal =
1761 : 1463 : (rinfo->required_relids == rinfo->clause_relids);
1762 : 1463 : bool clause_relids_is_multiple =
1763 : 1463 : (bms_membership(rinfo->clause_relids) == BMS_MULTIPLE);
1764 : :
1765 : : /*
1766 : : * Recurse down into clauses if the target relation is present in
1767 : : * clause_relids or required_relids. We must check required_relids
1768 : : * because the relation not present in clause_relids might still be
1769 : : * present somewhere in orclause.
1770 : : */
1771 [ + + + + ]: 1511 : if (bms_is_member(context->rt_index, rinfo->clause_relids) ||
1772 : 48 : bms_is_member(context->rt_index, rinfo->required_relids))
1773 : : {
1774 : : Relids new_clause_relids;
1775 : :
1776 : 1453 : ChangeVarNodesWalkExpression((Node *) rinfo->clause, context);
1777 : 1453 : ChangeVarNodesWalkExpression((Node *) rinfo->orclause, context);
1778 : :
1779 : 1453 : new_clause_relids = adjust_relid_set(rinfo->clause_relids,
1780 : : context->rt_index,
1781 : : context->new_index);
1782 : :
1783 : : /*
1784 : : * Incrementally adjust num_base_rels based on the change of
1785 : : * clause_relids, which could contain both base relids and
1786 : : * outer-join relids. This operation is legal until we remove
1787 : : * only baserels.
1788 : : */
1789 : 1453 : rinfo->num_base_rels -= bms_num_members(rinfo->clause_relids) -
1790 : 1453 : bms_num_members(new_clause_relids);
1791 : :
1792 : 1453 : rinfo->clause_relids = new_clause_relids;
1793 : 1453 : rinfo->left_relids =
1794 : 1453 : adjust_relid_set(rinfo->left_relids, context->rt_index, context->new_index);
1795 : 1453 : rinfo->right_relids =
1796 : 1453 : adjust_relid_set(rinfo->right_relids, context->rt_index, context->new_index);
1797 : : }
1798 : :
1799 [ + + ]: 1463 : if (is_req_equal)
1800 : 20 : rinfo->required_relids = rinfo->clause_relids;
1801 : : else
1802 : 1443 : rinfo->required_relids =
1803 : 1443 : adjust_relid_set(rinfo->required_relids, context->rt_index, context->new_index);
1804 : :
1805 : 1463 : rinfo->outer_relids =
1806 : 1463 : adjust_relid_set(rinfo->outer_relids, context->rt_index, context->new_index);
1807 : 1463 : rinfo->incompatible_relids =
1808 : 1463 : adjust_relid_set(rinfo->incompatible_relids, context->rt_index, context->new_index);
1809 : :
1810 [ + + + + ]: 2767 : if (rinfo->mergeopfamilies &&
1811 [ + + ]: 2490 : bms_get_singleton_member(rinfo->clause_relids, &relid) &&
1812 : 991 : clause_relids_is_multiple &&
1813 [ + - + - ]: 991 : relid == context->new_index && IsA(rinfo->clause, OpExpr))
1814 : : {
1815 : : Expr *leftOp;
1816 : : Expr *rightOp;
1817 : :
1818 : 991 : leftOp = (Expr *) get_leftop(rinfo->clause);
1819 : 991 : rightOp = (Expr *) get_rightop(rinfo->clause);
1820 : :
1821 : : /*
1822 : : * For self-join elimination, changing varnos could transform
1823 : : * "t1.a = t2.a" into "t1.a = t1.a". That is always true as long
1824 : : * as "t1.a" is not null. We use equal() to check for such a
1825 : : * case, and then we replace the qual with a check for not null
1826 : : * (NullTest).
1827 : : */
1828 [ + - + + ]: 991 : if (leftOp != NULL && equal(leftOp, rightOp))
1829 : : {
1830 : 981 : NullTest *ntest = makeNode(NullTest);
1831 : :
1832 : 981 : ntest->arg = leftOp;
1833 : 981 : ntest->nulltesttype = IS_NOT_NULL;
1834 : 981 : ntest->argisrow = false;
1835 : 981 : ntest->location = -1;
1836 : 981 : rinfo->clause = (Expr *) ntest;
1837 : 981 : rinfo->mergeopfamilies = NIL;
1838 : 981 : rinfo->left_em = NULL;
1839 : 981 : rinfo->right_em = NULL;
1840 : : }
1841 [ - + ]: 991 : Assert(rinfo->orclause == NULL);
1842 : : }
1843 : 1463 : return true;
1844 : : }
1845 : :
1846 : 27964 : return false;
1847 : : }
1848 : :
1849 : : /*
1850 : : * Remove a relation after we have proven that it participates only in an
1851 : : * unneeded unique self-join.
1852 : : *
1853 : : * Replace any links in planner info structures.
1854 : : *
1855 : : * Transfer join and restriction clauses from the removed relation to the
1856 : : * remaining one. We change the Vars of the clause to point to the
1857 : : * remaining relation instead of the removed one. The clauses that require
1858 : : * a subset of joinrelids become restriction clauses of the remaining
1859 : : * relation, and others remain join clauses. We append them to
1860 : : * baserestrictinfo and joininfo, respectively, trying not to introduce
1861 : : * duplicates.
1862 : : *
1863 : : * We also have to process the 'joinclauses' list here, because it
1864 : : * contains EC-derived join clauses which must become filter clauses. It
1865 : : * is not enough to just correct the ECs because the EC-derived
1866 : : * restrictions are generated before join removal (see
1867 : : * generate_base_implied_equalities).
1868 : : *
1869 : : * NOTE: Remember to keep the code in sync with PlannerInfo to be sure all
1870 : : * cached relids and relid bitmapsets can be correctly cleaned during the
1871 : : * self-join elimination procedure.
1872 : : */
1873 : : static void
446 1874 : 468 : remove_self_join_rel(PlannerInfo *root, PlanRowMark *kmark, PlanRowMark *rmark,
1875 : : RelOptInfo *toKeep, RelOptInfo *toRemove,
1876 : : List *restrictlist)
1877 : : {
1878 : : List *joininfos;
1879 : : ListCell *lc;
1880 : : int i;
1881 : 468 : List *jinfo_candidates = NIL;
1882 : 468 : List *binfo_candidates = NIL;
1883 : :
1884 [ - + ]: 468 : Assert(toKeep->relid > 0);
1885 [ - + ]: 468 : Assert(toRemove->relid > 0);
1886 : :
1887 : : /*
1888 : : * Replace the index of the removing table with the keeping one. The
1889 : : * technique of removing/distributing restrictinfo is used here to attach
1890 : : * just appeared (for keeping relation) join clauses and avoid adding
1891 : : * duplicates of those that already exist in the joininfo list.
1892 : : */
1893 : 468 : joininfos = list_copy(toRemove->joininfo);
1894 [ + + + + : 1019 : foreach_node(RestrictInfo, rinfo, joininfos)
+ + ]
1895 : : {
1896 : 83 : remove_join_clause_from_rels(root, rinfo, rinfo->required_relids);
363 1897 : 83 : ChangeVarNodesExtended((Node *) rinfo, toRemove->relid, toKeep->relid,
1898 : : 0, replace_relid_callback);
1899 : :
446 1900 [ + + ]: 83 : if (bms_membership(rinfo->required_relids) == BMS_MULTIPLE)
1901 : 68 : jinfo_candidates = lappend(jinfo_candidates, rinfo);
1902 : : else
1903 : 15 : binfo_candidates = lappend(binfo_candidates, rinfo);
1904 : : }
1905 : :
1906 : : /*
1907 : : * Concatenate restrictlist to the list of base restrictions of the
1908 : : * removing table just to simplify the replacement procedure: all of them
1909 : : * weren't connected to any keeping relations and need to be added to some
1910 : : * rels.
1911 : : */
1912 : 468 : toRemove->baserestrictinfo = list_concat(toRemove->baserestrictinfo,
1913 : : restrictlist);
1914 [ + - + + : 1633 : foreach_node(RestrictInfo, rinfo, toRemove->baserestrictinfo)
+ + ]
1915 : : {
363 1916 : 697 : ChangeVarNodesExtended((Node *) rinfo, toRemove->relid, toKeep->relid,
1917 : : 0, replace_relid_callback);
1918 : :
446 1919 [ - + ]: 697 : if (bms_membership(rinfo->required_relids) == BMS_MULTIPLE)
446 akorotkov@postgresql 1920 :UBC 0 : jinfo_candidates = lappend(jinfo_candidates, rinfo);
1921 : : else
446 akorotkov@postgresql 1922 :CBC 697 : binfo_candidates = lappend(binfo_candidates, rinfo);
1923 : : }
1924 : :
1925 : : /*
1926 : : * Now, add all non-redundant clauses to the keeping relation.
1927 : : */
1928 : 468 : add_non_redundant_clauses(root, binfo_candidates,
1929 : : &toKeep->baserestrictinfo, toRemove->relid);
1930 : 468 : add_non_redundant_clauses(root, jinfo_candidates,
1931 : : &toKeep->joininfo, toRemove->relid);
1932 : :
1933 : 468 : list_free(binfo_candidates);
1934 : 468 : list_free(jinfo_candidates);
1935 : :
1936 : : /*
1937 : : * Arrange equivalence classes, mentioned removing a table, with the
1938 : : * keeping one: varno of removing table should be replaced in members and
1939 : : * sources lists. Also, remove duplicated elements if this replacement
1940 : : * procedure created them.
1941 : : */
1942 : 468 : i = -1;
1943 [ + + ]: 1219 : while ((i = bms_next_member(toRemove->eclass_indexes, i)) >= 0)
1944 : : {
1945 : 751 : EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
1946 : :
1947 : 751 : update_eclasses(ec, toRemove->relid, toKeep->relid);
1948 : 751 : toKeep->eclass_indexes = bms_add_member(toKeep->eclass_indexes, i);
1949 : : }
1950 : :
1951 : : /*
1952 : : * Transfer the targetlist and attr_needed flags.
1953 : : */
1954 : :
1955 [ + - + + : 1704 : foreach(lc, toRemove->reltarget->exprs)
+ + ]
1956 : : {
1957 : 1236 : Node *node = lfirst(lc);
1958 : :
363 1959 : 1236 : ChangeVarNodesExtended(node, toRemove->relid, toKeep->relid, 0,
1960 : : replace_relid_callback);
446 1961 [ + + ]: 1236 : if (!list_member(toKeep->reltarget->exprs, node))
1962 : 128 : toKeep->reltarget->exprs = lappend(toKeep->reltarget->exprs, node);
1963 : : }
1964 : :
1965 [ + + ]: 5653 : for (i = toKeep->min_attr; i <= toKeep->max_attr; i++)
1966 : : {
1967 : 5185 : int attno = i - toKeep->min_attr;
1968 : :
1969 : 10370 : toRemove->attr_needed[attno] = adjust_relid_set(toRemove->attr_needed[attno],
1970 : 5185 : toRemove->relid, toKeep->relid);
1971 : 5185 : toKeep->attr_needed[attno] = bms_add_members(toKeep->attr_needed[attno],
1972 : 5185 : toRemove->attr_needed[attno]);
1973 : : }
1974 : :
1975 : : /*
1976 : : * If the removed relation has a row mark, transfer it to the remaining
1977 : : * one.
1978 : : *
1979 : : * If both rels have row marks, just keep the one corresponding to the
1980 : : * remaining relation because we verified earlier that they have the same
1981 : : * strength.
1982 : : */
1983 [ + + ]: 468 : if (rmark)
1984 : : {
1985 [ + - ]: 41 : if (kmark)
1986 : : {
1987 [ - + ]: 41 : Assert(kmark->markType == rmark->markType);
1988 : :
1989 : 41 : root->rowMarks = list_delete_ptr(root->rowMarks, rmark);
1990 : : }
1991 : : else
1992 : : {
1993 : : /* Shouldn't have inheritance children here. */
446 akorotkov@postgresql 1994 [ # # ]:UBC 0 : Assert(rmark->rti == rmark->prti);
1995 : :
1996 : 0 : rmark->rti = rmark->prti = toKeep->relid;
1997 : : }
1998 : : }
1999 : :
2000 : : /*
2001 : : * Replace varno in all the query structures, except nodes RangeTblRef
2002 : : * otherwise later remove_rel_from_joinlist will yield errors.
2003 : : */
363 akorotkov@postgresql 2004 :CBC 468 : ChangeVarNodesExtended((Node *) root->parse, toRemove->relid, toKeep->relid,
2005 : : 0, replace_relid_callback);
2006 : :
2007 : : /* Replace links in the planner info */
15 rguo@postgresql.org 2008 :GNC 468 : remove_rel_from_query(root, toRemove->relid, toKeep->relid, NULL, NULL);
2009 : :
2010 : : /* Replace varno in the fully-processed targetlist */
363 akorotkov@postgresql 2011 :CBC 468 : ChangeVarNodesExtended((Node *) root->processed_tlist, toRemove->relid,
2012 : 468 : toKeep->relid, 0, replace_relid_callback);
2013 : :
2014 : : /*
2015 : : * No need to touch all_result_relids or leaf_result_relids: at this point
2016 : : * those sets contain only parse->resultRelation; inheritance children
2017 : : * have not been added yet; that happens later in add_other_rels_to_query.
2018 : : * And remove_self_joins_recurse rejects parse->resultRelation as an SJE
2019 : : * candidate to preserve the EPQ mechanism. So toRemove->relid cannot be
2020 : : * a member.
2021 : : */
8 rguo@postgresql.org 2022 [ - + ]:GNC 468 : Assert(!bms_is_member(toRemove->relid, root->all_result_relids));
2023 [ - + ]: 468 : Assert(!bms_is_member(toRemove->relid, root->leaf_result_relids));
2024 : :
2025 : : /*
2026 : : * There may be references to the rel in root->fkey_list, but if so,
2027 : : * match_foreign_keys_to_quals() will get rid of them.
2028 : : */
2029 : :
2030 : : /*
2031 : : * Finally, remove the rel from the baserel array to prevent it from being
2032 : : * referenced again. (We can't do this earlier because
2033 : : * remove_join_clause_from_rels will touch it.)
2034 : : */
446 akorotkov@postgresql 2035 :CBC 468 : root->simple_rel_array[toRemove->relid] = NULL;
254 2036 : 468 : root->simple_rte_array[toRemove->relid] = NULL;
2037 : :
2038 : : /* And nuke the RelOptInfo, just in case there's another access path. */
446 2039 : 468 : pfree(toRemove);
2040 : :
2041 : :
2042 : : /*
2043 : : * Now repeat construction of attr_needed bits coming from all other
2044 : : * sources.
2045 : : */
2046 : 468 : rebuild_placeholder_attr_needed(root);
2047 : 468 : rebuild_joinclause_attr_needed(root);
2048 : 468 : rebuild_eclass_attr_needed(root);
2049 : 468 : rebuild_lateral_attr_needed(root);
2050 : 468 : }
2051 : :
2052 : : /*
2053 : : * split_selfjoin_quals
2054 : : * Processes 'joinquals' by building two lists: one containing the quals
2055 : : * where the columns/exprs are on either side of the join match and
2056 : : * another one containing the remaining quals.
2057 : : *
2058 : : * 'joinquals' must only contain quals for a RTE_RELATION being joined to
2059 : : * itself.
2060 : : */
2061 : : static void
2062 : 1791 : split_selfjoin_quals(PlannerInfo *root, List *joinquals, List **selfjoinquals,
2063 : : List **otherjoinquals, int from, int to)
2064 : : {
2065 : 1791 : List *sjoinquals = NIL;
2066 : 1791 : List *ojoinquals = NIL;
2067 : :
2068 [ + - + + : 5497 : foreach_node(RestrictInfo, rinfo, joinquals)
+ + ]
2069 : : {
2070 : : OpExpr *expr;
2071 : : Node *leftexpr;
2072 : : Node *rightexpr;
2073 : :
2074 : : /* In general, clause looks like F(arg1) = G(arg2) */
2075 [ + - + - ]: 3830 : if (!rinfo->mergeopfamilies ||
2076 [ + - ]: 3830 : bms_num_members(rinfo->clause_relids) != 2 ||
2077 [ - + ]: 3830 : bms_membership(rinfo->left_relids) != BMS_SINGLETON ||
2078 : 1915 : bms_membership(rinfo->right_relids) != BMS_SINGLETON)
2079 : : {
446 akorotkov@postgresql 2080 :UBC 0 : ojoinquals = lappend(ojoinquals, rinfo);
2081 : 0 : continue;
2082 : : }
2083 : :
446 akorotkov@postgresql 2084 :CBC 1915 : expr = (OpExpr *) rinfo->clause;
2085 : :
2086 [ + - - + ]: 1915 : if (!IsA(expr, OpExpr) || list_length(expr->args) != 2)
2087 : : {
446 akorotkov@postgresql 2088 :UBC 0 : ojoinquals = lappend(ojoinquals, rinfo);
2089 : 0 : continue;
2090 : : }
2091 : :
446 akorotkov@postgresql 2092 :CBC 1915 : leftexpr = get_leftop(rinfo->clause);
2093 : 1915 : rightexpr = copyObject(get_rightop(rinfo->clause));
2094 : :
2095 [ + - + + ]: 1915 : if (leftexpr && IsA(leftexpr, RelabelType))
2096 : 130 : leftexpr = (Node *) ((RelabelType *) leftexpr)->arg;
2097 [ + - + + ]: 1915 : if (rightexpr && IsA(rightexpr, RelabelType))
2098 : 125 : rightexpr = (Node *) ((RelabelType *) rightexpr)->arg;
2099 : :
2100 : : /*
2101 : : * Quite an expensive operation, narrowing the use case. For example,
2102 : : * when we have cast of the same var to different (but compatible)
2103 : : * types.
2104 : : */
363 2105 : 1915 : ChangeVarNodesExtended(rightexpr,
2106 : 1915 : bms_singleton_member(rinfo->right_relids),
2107 : 1915 : bms_singleton_member(rinfo->left_relids), 0,
2108 : : replace_relid_callback);
2109 : :
446 2110 [ + + ]: 1915 : if (equal(leftexpr, rightexpr))
2111 : 1492 : sjoinquals = lappend(sjoinquals, rinfo);
2112 : : else
2113 : 423 : ojoinquals = lappend(ojoinquals, rinfo);
2114 : : }
2115 : :
2116 : 1791 : *selfjoinquals = sjoinquals;
2117 : 1791 : *otherjoinquals = ojoinquals;
2118 : 1791 : }
2119 : :
2120 : : /*
2121 : : * Check for a case when uniqueness is at least partly derived from a
2122 : : * baserestrictinfo clause. In this case, we have a chance to return only
2123 : : * one row (if such clauses on both sides of SJ are equal) or nothing (if they
2124 : : * are different).
2125 : : */
2126 : : static bool
2127 : 523 : match_unique_clauses(PlannerInfo *root, RelOptInfo *outer, List *uclauses,
2128 : : Index relid)
2129 : : {
2130 [ + + + + : 1061 : foreach_node(RestrictInfo, rinfo, uclauses)
+ + ]
2131 : : {
2132 : : Expr *clause;
2133 : : Node *iclause;
2134 : : Node *c1;
2135 : 125 : bool matched = false;
2136 : :
2137 [ + - - + ]: 125 : Assert(outer->relid > 0 && relid > 0);
2138 : :
2139 : : /* Only filters like f(R.x1,...,R.xN) == expr we should consider. */
2140 [ - + ]: 125 : Assert(bms_is_empty(rinfo->left_relids) ^
2141 : : bms_is_empty(rinfo->right_relids));
2142 : :
2143 : 125 : clause = (Expr *) copyObject(rinfo->clause);
363 2144 : 125 : ChangeVarNodesExtended((Node *) clause, relid, outer->relid, 0,
2145 : : replace_relid_callback);
2146 : :
446 2147 [ + + ]: 125 : iclause = bms_is_empty(rinfo->left_relids) ? get_rightop(clause) :
2148 : 120 : get_leftop(clause);
2149 [ + + ]: 125 : c1 = bms_is_empty(rinfo->left_relids) ? get_leftop(clause) :
2150 : 120 : get_rightop(clause);
2151 : :
2152 : : /*
2153 : : * Compare these left and right sides with the corresponding sides of
2154 : : * the outer's filters. If no one is detected - return immediately.
2155 : : */
2156 [ + + + + : 340 : foreach_node(RestrictInfo, orinfo, outer->baserestrictinfo)
+ + ]
2157 : : {
2158 : : Node *oclause;
2159 : : Node *c2;
2160 : :
2161 [ + + ]: 160 : if (orinfo->mergeopfamilies == NIL)
2162 : : /* Don't consider clauses that aren't similar to 'F(X)=G(Y)' */
2163 : 50 : continue;
2164 : :
2165 [ - + ]: 110 : Assert(is_opclause(orinfo->clause));
2166 : :
2167 : 220 : oclause = bms_is_empty(orinfo->left_relids) ?
2168 [ + + ]: 110 : get_rightop(orinfo->clause) : get_leftop(orinfo->clause);
2169 : 220 : c2 = (bms_is_empty(orinfo->left_relids) ?
2170 [ + + ]: 110 : get_leftop(orinfo->clause) : get_rightop(orinfo->clause));
2171 : :
2172 [ + + + + ]: 110 : if (equal(iclause, oclause) && equal(c1, c2))
2173 : : {
2174 : 70 : matched = true;
2175 : 70 : break;
2176 : : }
2177 : : }
2178 : :
2179 [ + + ]: 125 : if (!matched)
2180 : 55 : return false;
2181 : : }
2182 : :
2183 : 468 : return true;
2184 : : }
2185 : :
2186 : : /*
2187 : : * Find and remove unique self-joins in a group of base relations that have
2188 : : * the same Oid.
2189 : : *
2190 : : * Returns a set of relids that were removed.
2191 : : */
2192 : : static Relids
2193 : 9069 : remove_self_joins_one_group(PlannerInfo *root, Relids relids)
2194 : : {
2195 : 9069 : Relids result = NULL;
2196 : : int k; /* Index of kept relation */
2197 : 9069 : int r = -1; /* Index of removed relation */
2198 : :
2199 [ + + ]: 28321 : while ((r = bms_next_member(relids, r)) > 0)
2200 : : {
252 2201 : 19252 : RelOptInfo *rrel = root->simple_rel_array[r];
2202 : :
446 2203 : 19252 : k = r;
2204 : :
2205 [ + + ]: 30302 : while ((k = bms_next_member(relids, k)) > 0)
2206 : : {
2207 : 11518 : Relids joinrelids = NULL;
252 2208 : 11518 : RelOptInfo *krel = root->simple_rel_array[k];
2209 : : List *restrictlist;
2210 : : List *selfjoinquals;
2211 : : List *otherjoinquals;
2212 : : ListCell *lc;
446 2213 : 11518 : bool jinfo_check = true;
252 2214 : 11518 : PlanRowMark *kmark = NULL;
2215 : 11518 : PlanRowMark *rmark = NULL;
446 2216 : 11518 : List *uclauses = NIL;
2217 : :
2218 : : /* A sanity check: the relations have the same Oid. */
2219 [ - + ]: 11518 : Assert(root->simple_rte_array[k]->relid ==
2220 : : root->simple_rte_array[r]->relid);
2221 : :
2222 : : /*
2223 : : * It is impossible to eliminate the join of two relations if they
2224 : : * belong to different rules of order. Otherwise, the planner
2225 : : * can't find any variants of the correct query plan.
2226 : : */
2227 [ + + + + : 14188 : foreach(lc, root->join_info_list)
+ + ]
2228 : : {
2229 : 8956 : SpecialJoinInfo *info = (SpecialJoinInfo *) lfirst(lc);
2230 : :
2231 [ + + ]: 17912 : if ((bms_is_member(k, info->syn_lefthand) ^
2232 [ + + ]: 12677 : bms_is_member(r, info->syn_lefthand)) ||
2233 : 3721 : (bms_is_member(k, info->syn_righthand) ^
2234 : 3721 : bms_is_member(r, info->syn_righthand)))
2235 : : {
2236 : 6286 : jinfo_check = false;
2237 : 6286 : break;
2238 : : }
2239 : : }
2240 [ + + ]: 11518 : if (!jinfo_check)
2241 : 11050 : continue;
2242 : :
2243 : : /*
2244 : : * Check Row Marks equivalence. We can't remove the join if the
2245 : : * relations have row marks of different strength (e.g., one is
2246 : : * locked FOR UPDATE, and another just has ROW_MARK_REFERENCE for
2247 : : * EvalPlanQual rechecking).
2248 : : */
2249 [ + + + - : 5368 : foreach(lc, root->rowMarks)
+ + ]
2250 : : {
2251 : 242 : PlanRowMark *rowMark = (PlanRowMark *) lfirst(lc);
2252 : :
254 2253 [ + + ]: 242 : if (rowMark->rti == r)
2254 : : {
252 2255 [ - + ]: 106 : Assert(rmark == NULL);
2256 : 106 : rmark = rowMark;
2257 : : }
254 2258 [ + + ]: 136 : else if (rowMark->rti == k)
2259 : : {
252 2260 [ - + ]: 106 : Assert(kmark == NULL);
2261 : 106 : kmark = rowMark;
2262 : : }
2263 : :
2264 [ + + + - ]: 242 : if (kmark && rmark)
446 2265 : 106 : break;
2266 : : }
252 2267 [ + + + - : 5232 : if (kmark && rmark && kmark->markType != rmark->markType)
+ + ]
446 2268 : 28 : continue;
2269 : :
2270 : : /*
2271 : : * We only deal with base rels here, so their relids bitset
2272 : : * contains only one member -- their relid.
2273 : : */
2274 : 5204 : joinrelids = bms_add_member(joinrelids, r);
2275 : 5204 : joinrelids = bms_add_member(joinrelids, k);
2276 : :
2277 : : /*
2278 : : * PHVs should not impose any constraints on removing self-joins.
2279 : : */
2280 : :
2281 : : /*
2282 : : * At this stage, joininfo lists of inner and outer can contain
2283 : : * only clauses required for a superior outer join that can't
2284 : : * influence this optimization. So, we can avoid to call the
2285 : : * build_joinrel_restrictlist() routine.
2286 : : */
2287 : 5204 : restrictlist = generate_join_implied_equalities(root, joinrelids,
2288 : : rrel->relids,
2289 : : krel, NULL);
2290 [ + + ]: 5204 : if (restrictlist == NIL)
2291 : 3413 : continue;
2292 : :
2293 : : /*
2294 : : * Process restrictlist to separate the self-join quals from the
2295 : : * other quals. e.g., "x = x" goes to selfjoinquals and "a = b" to
2296 : : * otherjoinquals.
2297 : : */
2298 : 1791 : split_selfjoin_quals(root, restrictlist, &selfjoinquals,
252 2299 : 1791 : &otherjoinquals, rrel->relid, krel->relid);
2300 : :
446 2301 [ - + ]: 1791 : Assert(list_length(restrictlist) ==
2302 : : (list_length(selfjoinquals) + list_length(otherjoinquals)));
2303 : :
2304 : : /*
2305 : : * To enable SJE for the only degenerate case without any self
2306 : : * join clauses at all, add baserestrictinfo to this list. The
2307 : : * degenerate case works only if both sides have the same clause.
2308 : : * So doesn't matter which side to add.
2309 : : */
252 2310 : 1791 : selfjoinquals = list_concat(selfjoinquals, krel->baserestrictinfo);
2311 : :
2312 : : /*
2313 : : * Determine if the rrel can duplicate outer rows. We must bypass
2314 : : * the unique rel cache here since we're possibly using a subset
2315 : : * of join quals. We can use 'force_cache' == true when all join
2316 : : * quals are self-join quals. Otherwise, we could end up putting
2317 : : * false negatives in the cache.
2318 : : */
2319 [ + + ]: 1791 : if (!innerrel_is_unique_ext(root, joinrelids, rrel->relids,
2320 : : krel, JOIN_INNER, selfjoinquals,
446 2321 : 1791 : list_length(otherjoinquals) == 0,
2322 : : &uclauses))
2323 : 1268 : continue;
2324 : :
2325 : : /*
2326 : : * 'uclauses' is the copy of outer->baserestrictinfo that are
2327 : : * associated with an index. We proved by matching selfjoinquals
2328 : : * to a unique index that the outer relation has at most one
2329 : : * matching row for each inner row. Sometimes that is not enough.
2330 : : * e.g. "WHERE s1.b = s2.b AND s1.a = 1 AND s2.a = 2" when the
2331 : : * unique index is (a,b). Having non-empty uclauses, we must
2332 : : * validate that the inner baserestrictinfo contains the same
2333 : : * expressions, or we won't match the same row on each side of the
2334 : : * join.
2335 : : */
252 2336 [ + + ]: 523 : if (!match_unique_clauses(root, rrel, uclauses, krel->relid))
446 2337 : 55 : continue;
2338 : :
2339 : : /*
2340 : : * Remove rrel RelOptInfo from the planner structures and the
2341 : : * corresponding row mark.
2342 : : */
252 2343 : 468 : remove_self_join_rel(root, kmark, rmark, krel, rrel, restrictlist);
2344 : :
446 2345 : 468 : result = bms_add_member(result, r);
2346 : :
2347 : : /* We have removed the outer relation, try the next one. */
2348 : 468 : break;
2349 : : }
2350 : : }
2351 : :
2352 : 9069 : return result;
2353 : : }
2354 : :
2355 : : /*
2356 : : * Gather indexes of base relations from the joinlist and try to eliminate self
2357 : : * joins.
2358 : : */
2359 : : static Relids
2360 : 83659 : remove_self_joins_recurse(PlannerInfo *root, List *joinlist, Relids toRemove)
2361 : : {
2362 : : ListCell *jl;
2363 : 83659 : Relids relids = NULL;
2364 : 83659 : SelfJoinCandidate *candidates = NULL;
2365 : : int i;
2366 : : int j;
2367 : : int numRels;
2368 : :
2369 : : /* Collect indexes of base relations of the join tree */
2370 [ + - + + : 279015 : foreach(jl, joinlist)
+ + ]
2371 : : {
2372 : 195356 : Node *jlnode = (Node *) lfirst(jl);
2373 : :
2374 [ + + ]: 195356 : if (IsA(jlnode, RangeTblRef))
2375 : : {
2376 : 192638 : int varno = ((RangeTblRef *) jlnode)->rtindex;
2377 : 192638 : RangeTblEntry *rte = root->simple_rte_array[varno];
2378 : :
2379 : : /*
2380 : : * We only consider ordinary relations as candidates to be
2381 : : * removed, and these relations should not have TABLESAMPLE
2382 : : * clauses specified. Removing a relation with TABLESAMPLE clause
2383 : : * could potentially change the syntax of the query. Because of
2384 : : * UPDATE/DELETE EPQ mechanism, currently Query->resultRelation or
2385 : : * Query->mergeTargetRelation associated rel cannot be eliminated.
2386 : : */
2387 [ + + ]: 192638 : if (rte->rtekind == RTE_RELATION &&
2388 [ + + ]: 171336 : rte->relkind == RELKIND_RELATION &&
2389 [ + + ]: 166808 : rte->tablesample == NULL &&
2390 [ + + ]: 166786 : varno != root->parse->resultRelation &&
2391 [ + - ]: 165262 : varno != root->parse->mergeTargetRelation)
2392 : : {
2393 [ - + ]: 165262 : Assert(!bms_is_member(varno, relids));
2394 : 165262 : relids = bms_add_member(relids, varno);
2395 : : }
2396 : : }
2397 [ + - ]: 2718 : else if (IsA(jlnode, List))
2398 : : {
2399 : : /* Recursively go inside the sub-joinlist */
2400 : 2718 : toRemove = remove_self_joins_recurse(root, (List *) jlnode,
2401 : : toRemove);
2402 : : }
2403 : : else
446 akorotkov@postgresql 2404 [ # # ]:UBC 0 : elog(ERROR, "unrecognized joinlist node type: %d",
2405 : : (int) nodeTag(jlnode));
2406 : : }
2407 : :
446 akorotkov@postgresql 2408 :CBC 83659 : numRels = bms_num_members(relids);
2409 : :
2410 : : /* Need at least two relations for the join */
2411 [ + + ]: 83659 : if (numRels < 2)
2412 : 22100 : return toRemove;
2413 : :
2414 : : /*
2415 : : * In order to find relations with the same oid we first build an array of
2416 : : * candidates and then sort it by oid.
2417 : : */
146 michael@paquier.xyz 2418 :GNC 61559 : candidates = palloc_array(SelfJoinCandidate, numRels);
446 akorotkov@postgresql 2419 :CBC 61559 : i = -1;
2420 : 61559 : j = 0;
2421 [ + + ]: 211004 : while ((i = bms_next_member(relids, i)) >= 0)
2422 : : {
2423 : 149445 : candidates[j].relid = i;
2424 : 149445 : candidates[j].reloid = root->simple_rte_array[i]->relid;
2425 : 149445 : j++;
2426 : : }
2427 : :
2428 : 61559 : qsort(candidates, numRels, sizeof(SelfJoinCandidate),
2429 : : self_join_candidates_cmp);
2430 : :
2431 : : /*
2432 : : * Iteratively form a group of relation indexes with the same oid and
2433 : : * launch the routine that detects self-joins in this group and removes
2434 : : * excessive range table entries.
2435 : : *
2436 : : * At the end of the iteration, exclude the group from the overall relids
2437 : : * list. So each next iteration of the cycle will involve less and less
2438 : : * value of relids.
2439 : : */
2440 : 61559 : i = 0;
2441 [ + + ]: 211004 : for (j = 1; j < numRels + 1; j++)
2442 : : {
2443 [ + + + + ]: 149445 : if (j == numRels || candidates[j].reloid != candidates[i].reloid)
2444 : : {
2445 [ + + ]: 139342 : if (j - i >= 2)
2446 : : {
2447 : : /* Create a group of relation indexes with the same oid */
2448 : 8999 : Relids group = NULL;
2449 : : Relids removed;
2450 : :
2451 [ + + ]: 28101 : while (i < j)
2452 : : {
2453 : 19102 : group = bms_add_member(group, candidates[i].relid);
2454 : 19102 : i++;
2455 : : }
2456 : 8999 : relids = bms_del_members(relids, group);
2457 : :
2458 : : /*
2459 : : * Try to remove self-joins from a group of identical entries.
2460 : : * Make the next attempt iteratively - if something is deleted
2461 : : * from a group, changes in clauses and equivalence classes
2462 : : * can give us a chance to find more candidates.
2463 : : */
2464 : : do
2465 : : {
2466 [ - + ]: 9069 : Assert(!bms_overlap(group, toRemove));
2467 : 9069 : removed = remove_self_joins_one_group(root, group);
2468 : 9069 : toRemove = bms_add_members(toRemove, removed);
2469 : 9069 : group = bms_del_members(group, removed);
2470 [ + + + + ]: 9517 : } while (!bms_is_empty(removed) &&
2471 : 448 : bms_membership(group) == BMS_MULTIPLE);
2472 : 8999 : bms_free(removed);
2473 : 8999 : bms_free(group);
2474 : : }
2475 : : else
2476 : : {
2477 : : /* Single relation, just remove it from the set */
2478 : 130343 : relids = bms_del_member(relids, candidates[i].relid);
2479 : 130343 : i = j;
2480 : : }
2481 : : }
2482 : : }
2483 : :
2484 [ - + ]: 61559 : Assert(bms_is_empty(relids));
2485 : :
2486 : 61559 : return toRemove;
2487 : : }
2488 : :
2489 : : /*
2490 : : * Compare self-join candidates by their oids.
2491 : : */
2492 : : static int
2493 : 109691 : self_join_candidates_cmp(const void *a, const void *b)
2494 : : {
2495 : 109691 : const SelfJoinCandidate *ca = (const SelfJoinCandidate *) a;
2496 : 109691 : const SelfJoinCandidate *cb = (const SelfJoinCandidate *) b;
2497 : :
2498 [ + + ]: 109691 : if (ca->reloid != cb->reloid)
2499 [ + + ]: 99543 : return (ca->reloid < cb->reloid ? -1 : 1);
2500 : : else
2501 : 10148 : return 0;
2502 : : }
2503 : :
2504 : : /*
2505 : : * Find and remove useless self joins.
2506 : : *
2507 : : * Search for joins where a relation is joined to itself. If the join clause
2508 : : * for each tuple from one side of the join is proven to match the same
2509 : : * physical row (or nothing) on the other side, that self-join can be
2510 : : * eliminated from the query. Suitable join clauses are assumed to be in the
2511 : : * form of X = X, and can be replaced with NOT NULL clauses.
2512 : : *
2513 : : * For the sake of simplicity, we don't apply this optimization to special
2514 : : * joins. Here is a list of what we could do in some particular cases:
2515 : : * 'a a1 semi join a a2': is reduced to inner by reduce_unique_semijoins,
2516 : : * and then removed normally.
2517 : : * 'a a1 anti join a a2': could simplify to a scan with 'outer quals AND
2518 : : * (IS NULL on join columns OR NOT inner quals)'.
2519 : : * 'a a1 left join a a2': could simplify to a scan like inner but without
2520 : : * NOT NULL conditions on join columns.
2521 : : * 'a a1 left join (a a2 join b)': can't simplify this, because join to b
2522 : : * can both remove rows and introduce duplicates.
2523 : : *
2524 : : * To search for removable joins, we order all the relations on their Oid,
2525 : : * go over each set with the same Oid, and consider each pair of relations
2526 : : * in this set.
2527 : : *
2528 : : * To remove the join, we mark one of the participating relations as dead
2529 : : * and rewrite all references to it to point to the remaining relation.
2530 : : * This includes modifying RestrictInfos, EquivalenceClasses, and
2531 : : * EquivalenceMembers. We also have to modify the row marks. The join clauses
2532 : : * of the removed relation become either restriction or join clauses, based on
2533 : : * whether they reference any relations not participating in the removed join.
2534 : : *
2535 : : * 'joinlist' is the top-level joinlist of the query. If it has any
2536 : : * references to the removed relations, we update them to point to the
2537 : : * remaining ones.
2538 : : */
2539 : : List *
2540 : 255118 : remove_useless_self_joins(PlannerInfo *root, List *joinlist)
2541 : : {
2542 : 255118 : Relids toRemove = NULL;
2543 : 255118 : int relid = -1;
2544 : :
2545 [ + - + - : 510236 : if (!enable_self_join_elimination || joinlist == NIL ||
+ + ]
2546 [ + + ]: 429993 : (list_length(joinlist) == 1 && !IsA(linitial(joinlist), List)))
2547 : 174177 : return joinlist;
2548 : :
2549 : : /*
2550 : : * Merge pairs of relations participated in self-join. Remove unnecessary
2551 : : * range table entries.
2552 : : */
2553 : 80941 : toRemove = remove_self_joins_recurse(root, joinlist, toRemove);
2554 : :
2555 [ + + ]: 80941 : if (unlikely(toRemove != NULL))
2556 : : {
2557 : : /* At the end, remove orphaned relation links */
2558 [ + + ]: 911 : while ((relid = bms_next_member(toRemove, relid)) >= 0)
2559 : : {
2560 : 468 : int nremoved = 0;
2561 : :
2562 : 468 : joinlist = remove_rel_from_joinlist(joinlist, relid, &nremoved);
2563 [ - + ]: 468 : if (nremoved != 1)
446 akorotkov@postgresql 2564 [ # # ]:UBC 0 : elog(ERROR, "failed to find relation %d in joinlist", relid);
2565 : : }
2566 : : }
2567 : :
446 akorotkov@postgresql 2568 :CBC 80941 : return joinlist;
2569 : : }
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