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(PlannerInfo *root, EquivalenceClass *ec,
66 : : int relid, int ojrelid);
67 : : static Node *remove_rel_from_phvs(Node *node, int relid, int ojrelid);
68 : : static Node *remove_rel_from_phvs_mutator(Node *node, Relids removable);
69 : : static List *remove_rel_from_joinlist(List *joinlist, int relid, int *nremoved);
70 : : static bool rel_supports_distinctness(PlannerInfo *root, RelOptInfo *rel);
71 : : static bool rel_is_distinct_for(PlannerInfo *root, RelOptInfo *rel,
72 : : List *clause_list, List **extra_clauses);
73 : : static DistinctColInfo *distinct_col_search(int colno, List *distinct_cols);
74 : : static bool is_innerrel_unique_for(PlannerInfo *root,
75 : : Relids joinrelids,
76 : : Relids outerrelids,
77 : : RelOptInfo *innerrel,
78 : : JoinType jointype,
79 : : List *restrictlist,
80 : : List **extra_clauses);
81 : : static int self_join_candidates_cmp(const void *a, const void *b);
82 : : static bool replace_relid_callback(Node *node,
83 : : ChangeVarNodes_context *context);
84 : :
85 : :
86 : : /*
87 : : * remove_useless_joins
88 : : * Check for relations that don't actually need to be joined at all,
89 : : * and remove them from the query.
90 : : *
91 : : * We are passed the current joinlist and return the updated list. Other
92 : : * data structures that have to be updated are accessible via "root".
93 : : */
94 : : List *
5938 tgl@sss.pgh.pa.us 95 :CBC 246771 : remove_useless_joins(PlannerInfo *root, List *joinlist)
96 : : {
97 : : ListCell *lc;
98 : :
99 : : /*
100 : : * We are only interested in relations that are left-joined to, so we can
101 : : * scan the join_info_list to find them easily.
102 : : */
103 : 255314 : restart:
104 [ + + + + : 289742 : foreach(lc, root->join_info_list)
+ + ]
105 : : {
106 : 42971 : SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);
107 : : int innerrelid;
108 : : int nremoved;
109 : :
110 : : /* Skip if not removable */
111 [ + + ]: 42971 : if (!join_is_removable(root, sjinfo))
112 : 34428 : continue;
113 : :
114 : : /*
115 : : * Currently, join_is_removable can only succeed when the sjinfo's
116 : : * righthand is a single baserel. Remove that rel from the query and
117 : : * joinlist.
118 : : */
119 : 8543 : innerrelid = bms_singleton_member(sjinfo->min_righthand);
120 : :
502 akorotkov@postgresql 121 : 8543 : remove_leftjoinrel_from_query(root, innerrelid, sjinfo);
122 : :
123 : : /* We verify that exactly one reference gets removed from joinlist */
5938 tgl@sss.pgh.pa.us 124 : 8543 : nremoved = 0;
125 : 8543 : joinlist = remove_rel_from_joinlist(joinlist, innerrelid, &nremoved);
126 [ - + ]: 8543 : if (nremoved != 1)
5938 tgl@sss.pgh.pa.us 127 [ # # ]:UBC 0 : elog(ERROR, "failed to find relation %d in joinlist", innerrelid);
128 : :
129 : : /*
130 : : * We can delete this SpecialJoinInfo from the list too, since it's no
131 : : * longer of interest. (Since we'll restart the foreach loop
132 : : * immediately, we don't bother with foreach_delete_current.)
133 : : */
2542 tgl@sss.pgh.pa.us 134 :CBC 8543 : root->join_info_list = list_delete_cell(root->join_info_list, lc);
135 : :
136 : : /*
137 : : * Restart the scan. This is necessary to ensure we find all
138 : : * removable joins independently of ordering of the join_info_list
139 : : * (note that removal of attr_needed bits may make a join appear
140 : : * removable that did not before).
141 : : */
5938 142 : 8543 : goto restart;
143 : : }
144 : :
145 : 246771 : return joinlist;
146 : : }
147 : :
148 : : /*
149 : : * join_is_removable
150 : : * Check whether we need not perform this special join at all, because
151 : : * it will just duplicate its left input.
152 : : *
153 : : * This is true for a left join for which the join condition cannot match
154 : : * more than one inner-side row. (There are other possibly interesting
155 : : * cases, but we don't have the infrastructure to prove them.) We also
156 : : * have to check that the inner side doesn't generate any variables needed
157 : : * above the join.
158 : : */
159 : : static bool
160 : 42971 : join_is_removable(PlannerInfo *root, SpecialJoinInfo *sjinfo)
161 : : {
162 : : int innerrelid;
163 : : RelOptInfo *innerrel;
164 : : Relids inputrelids;
165 : : Relids joinrelids;
166 : 42971 : List *clause_list = NIL;
167 : : ListCell *l;
168 : : int attroff;
169 : :
170 : : /*
171 : : * Must be a left join to a single baserel, else we aren't going to be
172 : : * able to do anything with it.
173 : : */
1247 174 [ + + ]: 42971 : if (sjinfo->jointype != JOIN_LEFT)
4232 175 : 10581 : return false;
176 : :
177 [ + + ]: 32390 : if (!bms_get_singleton_member(sjinfo->min_righthand, &innerrelid))
5938 178 : 1057 : return false;
179 : :
180 : : /*
181 : : * Never try to eliminate a left join to the query result rel. Although
182 : : * the case is syntactically impossible in standard SQL, MERGE will build
183 : : * a join tree that looks exactly like that.
184 : : */
1226 185 [ + + ]: 31333 : if (innerrelid == root->parse->resultRelation)
186 : 636 : return false;
187 : :
5938 188 : 30697 : innerrel = find_base_rel(root, innerrelid);
189 : :
190 : : /*
191 : : * Before we go to the effort of checking whether any innerrel variables
192 : : * are needed above the join, make a quick check to eliminate cases in
193 : : * which we will surely be unable to prove uniqueness of the innerrel.
194 : : */
3736 195 [ + + ]: 30697 : if (!rel_supports_distinctness(root, innerrel))
196 : 2440 : return false;
197 : :
198 : : /* Compute the relid set for the join we are considering */
1138 199 : 28257 : inputrelids = bms_union(sjinfo->min_lefthand, sjinfo->min_righthand);
1242 200 [ - + ]: 28257 : Assert(sjinfo->ojrelid != 0);
201 : 28257 : joinrelids = bms_copy(inputrelids);
202 : 28257 : joinrelids = bms_add_member(joinrelids, sjinfo->ojrelid);
203 : :
204 : : /*
205 : : * We can't remove the join if any inner-rel attributes are used above the
206 : : * join. Here, "above" the join includes pushed-down conditions, so we
207 : : * should reject if attr_needed includes the OJ's own relid; therefore,
208 : : * compare to inputrelids not joinrelids.
209 : : *
210 : : * As a micro-optimization, it seems better to start with max_attr and
211 : : * count down rather than starting with min_attr and counting up, on the
212 : : * theory that the system attributes are somewhat less likely to be wanted
213 : : * and should be tested last.
214 : : */
5938 215 : 28257 : for (attroff = innerrel->max_attr - innerrel->min_attr;
216 [ + + ]: 270608 : attroff >= 0;
217 : 242351 : attroff--)
218 : : {
1242 219 [ + + ]: 261798 : if (!bms_is_subset(innerrel->attr_needed[attroff], inputrelids))
5938 220 : 19447 : return false;
221 : : }
222 : :
223 : : /*
224 : : * Similarly check that the inner rel isn't needed by any PlaceHolderVars
225 : : * that will be used above the join. The PHV case is a little bit more
226 : : * complicated, because PHVs may have been assigned a ph_eval_at location
227 : : * that includes the innerrel, yet their contained expression might not
228 : : * actually reference the innerrel (it could be just a constant, for
229 : : * instance). If such a PHV is due to be evaluated above the join then it
230 : : * needn't prevent join removal.
231 : : */
232 [ + + + + : 8974 : foreach(l, root->placeholder_list)
+ + ]
233 : : {
234 : 194 : PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);
235 : :
4700 236 [ - + ]: 194 : if (bms_overlap(phinfo->ph_lateral, innerrel->relids))
237 : 30 : return false; /* it references innerrel laterally */
5757 238 [ + + ]: 194 : if (!bms_overlap(phinfo->ph_eval_at, innerrel->relids))
239 : 61 : continue; /* it definitely doesn't reference innerrel */
1240 240 [ + + ]: 133 : if (bms_is_subset(phinfo->ph_needed, inputrelids))
241 : 5 : continue; /* PHV is not used above the join */
242 [ + + ]: 128 : if (!bms_is_member(sjinfo->ojrelid, phinfo->ph_eval_at))
243 : 25 : return false; /* it has to be evaluated below the join */
244 : :
245 : : /*
246 : : * We need to be sure there will still be a place to evaluate the PHV
247 : : * if we remove the join, ie that ph_eval_at wouldn't become empty.
248 : : */
249 [ + + ]: 103 : if (!bms_overlap(sjinfo->min_lefthand, phinfo->ph_eval_at))
4700 250 : 5 : return false; /* there isn't any other place to eval PHV */
251 : : /* Check contained expression last, since this is a bit expensive */
1986 252 [ - + ]: 98 : if (bms_overlap(pull_varnos(root, (Node *) phinfo->ph_var->phexpr),
5757 253 : 98 : innerrel->relids))
1240 tgl@sss.pgh.pa.us 254 :UBC 0 : return false; /* contained expression references innerrel */
255 : : }
256 : :
257 : : /*
258 : : * Search for mergejoinable clauses that constrain the inner rel against
259 : : * either the outer rel or a pseudoconstant. If an operator is
260 : : * mergejoinable then it behaves like equality for some btree opclass, so
261 : : * it's what we want. The mergejoinability test also eliminates clauses
262 : : * containing volatile functions, which we couldn't depend on.
263 : : */
5938 tgl@sss.pgh.pa.us 264 [ + + + + :CBC 17723 : foreach(l, innerrel->joininfo)
+ + ]
265 : : {
266 : 8943 : RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l);
267 : :
268 : : /*
269 : : * If the current join commutes with some other outer join(s) via
270 : : * outer join identity 3, there will be multiple clones of its join
271 : : * clauses in the joininfo list. We want to consider only the
272 : : * has_clone form of such clauses. Processing more than one form
273 : : * would be wasteful, and also some of the others would confuse the
274 : : * RINFO_IS_PUSHED_DOWN test below.
275 : : */
1247 276 [ + + ]: 8943 : if (restrictinfo->is_clone)
277 : 82 : continue; /* ignore it */
278 : :
279 : : /*
280 : : * If it's not a join clause for this outer join, we can't use it.
281 : : * Note that if the clause is pushed-down, then it is logically from
282 : : * above the outer join, even if it references no other rels (it might
283 : : * be from WHERE, for example).
284 : : */
2993 285 [ + + + + ]: 8861 : if (RINFO_IS_PUSHED_DOWN(restrictinfo, joinrelids))
1242 286 : 99 : continue; /* ignore; not useful here */
287 : :
288 : : /* Ignore if it's not a mergejoinable clause */
5938 289 [ + + ]: 8762 : if (!restrictinfo->can_join ||
290 [ - + ]: 8617 : restrictinfo->mergeopfamilies == NIL)
291 : 145 : continue; /* not mergejoinable */
292 : :
293 : : /*
294 : : * Check if the clause has the form "outer op inner" or "inner op
295 : : * outer", and if so mark which side is inner.
296 : : */
297 [ + + ]: 8617 : if (!clause_sides_match_join(restrictinfo, sjinfo->min_lefthand,
298 : : innerrel->relids))
299 : 5 : continue; /* no good for these input relations */
300 : :
301 : : /* OK, add to list */
302 : 8612 : clause_list = lappend(clause_list, restrictinfo);
303 : : }
304 : :
305 : : /*
306 : : * Now that we have the relevant equality join clauses, try to prove the
307 : : * innerrel distinct.
308 : : */
502 akorotkov@postgresql 309 [ + + ]: 8780 : if (rel_is_distinct_for(root, innerrel, clause_list, NULL))
3736 tgl@sss.pgh.pa.us 310 : 8543 : return true;
311 : :
312 : : /*
313 : : * Some day it would be nice to check for other methods of establishing
314 : : * distinctness.
315 : : */
5938 316 : 237 : return false;
317 : : }
318 : :
319 : : /*
320 : : * Remove the target relid and references to the target join from the
321 : : * planner's data structures, having determined that there is no need
322 : : * to include them in the query.
323 : : *
324 : : * We are not terribly thorough here. We only bother to update parts of
325 : : * the planner's data structures that will actually be consulted later.
326 : : */
327 : : static void
71 rguo@postgresql.org 328 :GNC 8543 : remove_leftjoinrel_from_query(PlannerInfo *root, int relid,
329 : : SpecialJoinInfo *sjinfo)
330 : : {
331 : 8543 : RelOptInfo *rel = find_base_rel(root, relid);
332 : 8543 : int ojrelid = sjinfo->ojrelid;
333 : : Relids joinrelids;
334 : : Relids join_plus_commute;
335 : : List *joininfos;
336 : : ListCell *l;
337 : :
338 : : /* Compute the relid set for the join we are considering */
339 : 8543 : joinrelids = bms_union(sjinfo->min_lefthand, sjinfo->min_righthand);
340 [ - + ]: 8543 : Assert(ojrelid != 0);
341 : 8543 : joinrelids = bms_add_member(joinrelids, ojrelid);
342 : :
343 : 8543 : remove_rel_from_query(root, relid, -1, sjinfo, joinrelids);
344 : :
345 : : /*
346 : : * Remove any joinquals referencing the rel from the joininfo lists.
347 : : *
348 : : * In some cases, a joinqual has to be put back after deleting its
349 : : * reference to the target rel. This can occur for pseudoconstant and
350 : : * outerjoin-delayed quals, which can get marked as requiring the rel in
351 : : * order to force them to be evaluated at or above the join. We can't
352 : : * just discard them, though. Only quals that logically belonged to the
353 : : * outer join being discarded should be removed from the query.
354 : : *
355 : : * We might encounter a qual that is a clone of a deletable qual with some
356 : : * outer-join relids added (see deconstruct_distribute_oj_quals). To
357 : : * ensure we get rid of such clones as well, add the relids of all OJs
358 : : * commutable with this one to the set we test against for
359 : : * pushed-down-ness.
360 : : */
361 : 8543 : join_plus_commute = bms_union(joinrelids,
362 : 8543 : sjinfo->commute_above_r);
363 : 8543 : join_plus_commute = bms_add_members(join_plus_commute,
364 : 8543 : sjinfo->commute_below_l);
365 : :
366 : : /*
367 : : * We must make a copy of the rel's old joininfo list before starting the
368 : : * loop, because otherwise remove_join_clause_from_rels would destroy the
369 : : * list while we're scanning it.
370 : : */
371 : 8543 : joininfos = list_copy(rel->joininfo);
372 [ + + + + : 17265 : foreach(l, joininfos)
+ + ]
373 : : {
374 : 8722 : RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
375 : :
376 : 8722 : remove_join_clause_from_rels(root, rinfo, rinfo->required_relids);
377 : :
378 [ + + + + ]: 8722 : if (RINFO_IS_PUSHED_DOWN(rinfo, join_plus_commute))
379 : : {
380 : : /*
381 : : * There might be references to relid or ojrelid in the
382 : : * RestrictInfo's relid sets, as a consequence of PHVs having had
383 : : * ph_eval_at sets that include those. We already checked above
384 : : * that any such PHV is safe (and updated its ph_eval_at), so we
385 : : * can just drop those references.
386 : : */
387 : 99 : remove_rel_from_restrictinfo(rinfo, relid, ojrelid);
388 : :
389 : : /*
390 : : * Cross-check that the clause itself does not reference the
391 : : * target rel or join.
392 : : */
393 : : #ifdef USE_ASSERT_CHECKING
394 : : {
395 : 99 : Relids clause_varnos = pull_varnos(root,
396 : 99 : (Node *) rinfo->clause);
397 : :
398 [ - + ]: 99 : Assert(!bms_is_member(relid, clause_varnos));
399 [ - + ]: 99 : Assert(!bms_is_member(ojrelid, clause_varnos));
400 : : }
401 : : #endif
402 : : /* Now throw it back into the joininfo lists */
403 : 99 : distribute_restrictinfo_to_rels(root, rinfo);
404 : : }
405 : : }
406 : :
407 : : /*
408 : : * There may be references to the rel in root->fkey_list, but if so,
409 : : * match_foreign_keys_to_quals() will get rid of them.
410 : : */
411 : :
412 : : /*
413 : : * Now remove the rel from the baserel array to prevent it from being
414 : : * referenced again. (We can't do this earlier because
415 : : * remove_join_clause_from_rels will touch it.)
416 : : */
417 : 8543 : root->simple_rel_array[relid] = NULL;
418 : 8543 : root->simple_rte_array[relid] = NULL;
419 : :
420 : : /* And nuke the RelOptInfo, just in case there's another access path */
421 : 8543 : pfree(rel);
422 : :
423 : : /*
424 : : * Now repeat construction of attr_needed bits coming from all other
425 : : * sources.
426 : : */
427 : 8543 : rebuild_placeholder_attr_needed(root);
428 : 8543 : rebuild_joinclause_attr_needed(root);
429 : 8543 : rebuild_eclass_attr_needed(root);
430 : 8543 : rebuild_lateral_attr_needed(root);
431 : 8543 : }
432 : :
433 : : /*
434 : : * Remove the target relid and references to the target join from the
435 : : * planner's data structures, having determined that there is no need
436 : : * to include them in the query. Optionally replace references to the
437 : : * removed relid with subst if this is a self-join removal.
438 : : *
439 : : * This function serves as the common infrastructure for left-join removal
440 : : * and self-join elimination. It is intentionally scoped to update only the
441 : : * shared planner data structures that are universally affected by relation
442 : : * removal. Each specific caller remains responsible for updating any
443 : : * remaining data structures required by its unique removal logic.
444 : : *
445 : : * The specific type of removal being performed is dictated by the combination
446 : : * of the sjinfo and subst parameters. A non-NULL sjinfo indicates left-join
447 : : * removal. When sjinfo is NULL, a positive subst value indicates self-join
448 : : * elimination (where references are replaced with subst).
449 : : */
450 : : static void
451 : 9011 : remove_rel_from_query(PlannerInfo *root, int relid,
452 : : int subst, SpecialJoinInfo *sjinfo,
453 : : Relids joinrelids)
454 : : {
455 [ + + ]: 9011 : int ojrelid = sjinfo ? sjinfo->ojrelid : 0;
456 : : Index rti;
457 : : ListCell *l;
458 : 9011 : bool is_outer_join = (sjinfo != NULL);
459 [ + + + - ]: 9011 : bool is_self_join = (!is_outer_join && subst > 0);
460 : :
461 [ + + - + ]: 9011 : Assert(is_outer_join || is_self_join);
462 [ + + - + ]: 9011 : Assert(!is_outer_join || ojrelid > 0);
463 [ + + - + ]: 9011 : Assert(!is_outer_join || joinrelids != NULL);
464 : :
465 : : /*
466 : : * Update all_baserels and related relid sets.
467 : : */
502 akorotkov@postgresql 468 :CBC 9011 : root->all_baserels = adjust_relid_set(root->all_baserels, relid, subst);
469 : 9011 : root->all_query_rels = adjust_relid_set(root->all_query_rels, relid, subst);
470 : :
71 rguo@postgresql.org 471 [ + + ]:GNC 9011 : if (is_outer_join)
472 : : {
473 : 8543 : root->outer_join_rels = bms_del_member(root->outer_join_rels, ojrelid);
474 : 8543 : root->all_query_rels = bms_del_member(root->all_query_rels, ojrelid);
475 : : }
476 : :
477 : : /*
478 : : * Likewise remove references from SpecialJoinInfo data structures.
479 : : *
480 : : * This is relevant in case the relation we're deleting is part of the
481 : : * relid sets of special joins: those sets have to be adjusted. If we are
482 : : * removing an outer join, the RHS of the target outer join will be made
483 : : * empty here, but that's OK since the caller will delete that
484 : : * SpecialJoinInfo entirely.
485 : : */
5882 tgl@sss.pgh.pa.us 486 [ + + + + :CBC 21325 : foreach(l, root->join_info_list)
+ + ]
487 : : {
1131 488 : 12314 : SpecialJoinInfo *sjinf = (SpecialJoinInfo *) lfirst(l);
489 : :
490 : : /*
491 : : * initsplan.c is fairly cavalier about allowing SpecialJoinInfos'
492 : : * lefthand/righthand relid sets to be shared with other data
493 : : * structures. Ensure that we don't modify the original relid sets.
494 : : * (The commute_xxx sets are always per-SpecialJoinInfo though.)
495 : : */
782 496 : 12314 : sjinf->min_lefthand = bms_copy(sjinf->min_lefthand);
497 : 12314 : sjinf->min_righthand = bms_copy(sjinf->min_righthand);
498 : 12314 : sjinf->syn_lefthand = bms_copy(sjinf->syn_lefthand);
499 : 12314 : sjinf->syn_righthand = bms_copy(sjinf->syn_righthand);
500 : :
501 : : /* Now adjust relid bit in the sets: */
502 akorotkov@postgresql 502 : 12314 : sjinf->min_lefthand = adjust_relid_set(sjinf->min_lefthand, relid, subst);
503 : 12314 : sjinf->min_righthand = adjust_relid_set(sjinf->min_righthand, relid, subst);
504 : 12314 : sjinf->syn_lefthand = adjust_relid_set(sjinf->syn_lefthand, relid, subst);
505 : 12314 : sjinf->syn_righthand = adjust_relid_set(sjinf->syn_righthand, relid, subst);
506 : :
71 rguo@postgresql.org 507 [ + + ]:GNC 12314 : if (is_outer_join)
508 : : {
509 : : /* Remove ojrelid bit from the sets: */
510 : 12221 : sjinf->min_lefthand = bms_del_member(sjinf->min_lefthand, ojrelid);
511 : 12221 : sjinf->min_righthand = bms_del_member(sjinf->min_righthand, ojrelid);
512 : 12221 : sjinf->syn_lefthand = bms_del_member(sjinf->syn_lefthand, ojrelid);
513 : 12221 : sjinf->syn_righthand = bms_del_member(sjinf->syn_righthand, ojrelid);
514 : : /* relid cannot appear in these fields, but ojrelid can: */
515 : 12221 : sjinf->commute_above_l = bms_del_member(sjinf->commute_above_l, ojrelid);
516 : 12221 : sjinf->commute_above_r = bms_del_member(sjinf->commute_above_r, ojrelid);
517 : 12221 : sjinf->commute_below_l = bms_del_member(sjinf->commute_below_l, ojrelid);
518 : 12221 : sjinf->commute_below_r = bms_del_member(sjinf->commute_below_r, ojrelid);
519 : : }
520 : : else
521 : : {
522 : : /*
523 : : * For self-join removal, replace relid references in
524 : : * semi_rhs_exprs.
525 : : */
419 akorotkov@postgresql 526 :CBC 93 : ChangeVarNodesExtended((Node *) sjinf->semi_rhs_exprs, relid, subst,
527 : : 0, replace_relid_callback);
528 : : }
529 : : }
530 : :
531 : : /*
532 : : * Likewise remove references from PlaceHolderVar data structures,
533 : : * removing any no-longer-needed placeholders entirely. We only remove
534 : : * PHVs for left-join removal. With self-join elimination, PHVs already
535 : : * get moved to the remaining relation, where they might still be needed.
536 : : * It might also happen that we skip the removal of some PHVs that could
537 : : * be removed. However, the overhead of extra PHVs is small compared to
538 : : * the complexity of analysis needed to remove them.
539 : : *
540 : : * Removal is a bit trickier than it might seem: we can remove PHVs that
541 : : * are used at the target rel and/or in the join qual, but not those that
542 : : * are used at join partner rels or above the join. It's not that easy to
543 : : * distinguish PHVs used at partner rels from those used in the join qual,
544 : : * since they will both have ph_needed sets that are subsets of
545 : : * joinrelids. However, a PHV used at a partner rel could not have the
546 : : * target rel in ph_eval_at, so we check that while deciding whether to
547 : : * remove or just update the PHV. There is no corresponding test in
548 : : * join_is_removable because it doesn't need to distinguish those cases.
549 : : */
2542 tgl@sss.pgh.pa.us 550 [ + + + + : 9195 : foreach(l, root->placeholder_list)
+ + ]
551 : : {
5938 552 : 184 : PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);
553 : :
71 rguo@postgresql.org 554 [ + + - + ]:GNC 184 : Assert(!is_outer_join || !bms_is_member(relid, phinfo->ph_lateral));
555 : :
556 [ + + + + ]: 333 : if (is_outer_join &&
428 akorotkov@postgresql 557 [ + + ]:CBC 179 : bms_is_subset(phinfo->ph_needed, joinrelids) &&
1118 tgl@sss.pgh.pa.us 558 : 30 : bms_is_member(relid, phinfo->ph_eval_at) &&
71 rguo@postgresql.org 559 [ + + ]:GNC 10 : !bms_is_member(ojrelid, phinfo->ph_eval_at))
560 : : {
2542 tgl@sss.pgh.pa.us 561 :CBC 5 : root->placeholder_list = foreach_delete_current(root->placeholder_list,
562 : : l);
1413 563 : 5 : root->placeholder_array[phinfo->phid] = NULL;
564 : : }
565 : : else
566 : : {
1238 567 : 179 : PlaceHolderVar *phv = phinfo->ph_var;
568 : :
502 akorotkov@postgresql 569 : 179 : phinfo->ph_eval_at = adjust_relid_set(phinfo->ph_eval_at, relid, subst);
71 rguo@postgresql.org 570 [ + + ]:GNC 179 : if (is_outer_join)
571 : 144 : phinfo->ph_eval_at = bms_del_member(phinfo->ph_eval_at, ojrelid);
1238 tgl@sss.pgh.pa.us 572 [ - + ]:CBC 179 : Assert(!bms_is_empty(phinfo->ph_eval_at)); /* checked previously */
573 : :
574 : : /* Reduce ph_needed to contain only "relation 0"; see below */
641 575 [ + + ]: 179 : if (bms_is_member(0, phinfo->ph_needed))
576 : 92 : phinfo->ph_needed = bms_make_singleton(0);
577 : : else
578 : 87 : phinfo->ph_needed = NULL;
579 : :
502 akorotkov@postgresql 580 :GNC 179 : phv->phrels = adjust_relid_set(phv->phrels, relid, subst);
71 rguo@postgresql.org 581 [ + + ]: 179 : if (is_outer_join)
582 : 144 : phv->phrels = bms_del_member(phv->phrels, ojrelid);
1238 tgl@sss.pgh.pa.us 583 [ - + ]: 179 : Assert(!bms_is_empty(phv->phrels));
584 : :
585 : : /*
586 : : * For self-join removal, update Var nodes within the PHV's
587 : : * expression to reference the replacement relid, and adjust
588 : : * ph_lateral for the relid substitution. (For left-join removal,
589 : : * we're removing rather than replacing, and any surviving PHV
590 : : * shouldn't reference the removed rel in its expression. Also,
591 : : * relid can't appear in ph_lateral for outer joins.)
592 : : */
71 rguo@postgresql.org 593 [ + + ]: 179 : if (is_self_join)
594 : : {
595 : 35 : ChangeVarNodesExtended((Node *) phv->phexpr, relid, subst, 0,
596 : : replace_relid_callback);
597 : 35 : phinfo->ph_lateral = adjust_relid_set(phinfo->ph_lateral, relid, subst);
598 : :
599 : : /*
600 : : * ph_lateral might contain rels mentioned in ph_eval_at after
601 : : * the replacement, remove them.
602 : : */
603 : 35 : phinfo->ph_lateral = bms_difference(phinfo->ph_lateral, phinfo->ph_eval_at);
604 : : /* ph_lateral might or might not be empty */
605 : : }
606 : :
1238 tgl@sss.pgh.pa.us 607 [ - + ]:CBC 179 : Assert(phv->phnullingrels == NULL); /* no need to adjust */
608 : : }
609 : : }
610 : :
611 : : /*
612 : : * Likewise remove references from EquivalenceClasses.
613 : : *
614 : : * For self-join removal, the caller has already updated the
615 : : * EquivalenceClasses, so we can skip this step.
616 : : */
71 rguo@postgresql.org 617 [ + + ]:GNC 9011 : if (is_outer_join)
618 : : {
619 [ + - + + : 49284 : foreach(l, root->eq_classes)
+ + ]
620 : : {
621 : 40741 : EquivalenceClass *ec = (EquivalenceClass *) lfirst(l);
622 : :
8 623 : 40741 : remove_rel_from_eclass(root, 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 : : *
646 : : * Also, for left-join removal, we strip the removed rel and join from any
647 : : * PlaceHolderVar embedded in the surviving rels' restriction clauses (see
648 : : * remove_rel_from_phvs); we needn't bother with the rel being removed,
649 : : * nor when the query has no PlaceHolderVars.
650 : : */
502 akorotkov@postgresql 651 [ + + ]:CBC 59885 : for (rti = 1; rti < root->simple_rel_array_size; rti++)
652 : : {
653 : 50874 : RelOptInfo *otherrel = root->simple_rel_array[rti];
654 : : int attroff;
655 : :
656 : : /* there may be empty slots corresponding to non-baserel RTEs */
657 [ + + ]: 50874 : if (otherrel == NULL)
658 : 24744 : continue;
659 : :
660 [ - + ]: 26130 : Assert(otherrel->relid == rti); /* sanity check on array */
661 : :
662 : 26130 : for (attroff = otherrel->max_attr - otherrel->min_attr;
663 [ + + ]: 571975 : attroff >= 0;
664 : 545845 : attroff--)
665 : : {
666 [ + + ]: 545845 : if (bms_is_member(0, otherrel->attr_needed[attroff]))
667 : 37963 : otherrel->attr_needed[attroff] = bms_make_singleton(0);
668 : : else
669 : 507882 : otherrel->attr_needed[attroff] = NULL;
670 : : }
671 : :
71 rguo@postgresql.org 672 [ + + ]:GNC 26130 : if (is_self_join)
419 akorotkov@postgresql 673 :CBC 1209 : ChangeVarNodesExtended((Node *) otherrel->lateral_vars, relid,
674 : : subst, 0, replace_relid_callback);
675 : :
8 rguo@postgresql.org 676 [ + + + + :GNC 26130 : if (is_outer_join && rti != relid && root->glob->lastPHId != 0)
+ + ]
677 : : {
8 rguo@postgresql.org 678 [ + + + + :CBC 808 : foreach_node(RestrictInfo, rinfo, otherrel->baserestrictinfo)
+ + ]
679 : : {
680 : 124 : rinfo->clause = (Expr *)
8 rguo@postgresql.org 681 :GNC 124 : remove_rel_from_phvs((Node *) rinfo->clause, relid, ojrelid);
682 : : }
683 : : }
684 : : }
502 akorotkov@postgresql 685 :CBC 9011 : }
686 : :
687 : : /*
688 : : * Remove any references to relid or ojrelid from the RestrictInfo.
689 : : *
690 : : * We only bother to clean out bits in the RestrictInfo's various relid sets,
691 : : * not nullingrel bits in contained Vars and PHVs. (This might have to be
692 : : * improved sometime.) However, if the RestrictInfo contains an OR clause
693 : : * we have to also clean up the sub-clauses.
694 : : */
695 : : static void
1236 tgl@sss.pgh.pa.us 696 : 3526 : remove_rel_from_restrictinfo(RestrictInfo *rinfo, int relid, int ojrelid)
697 : : {
698 : : /*
699 : : * initsplan.c is fairly cavalier about allowing RestrictInfos to share
700 : : * relid sets with other RestrictInfos, and SpecialJoinInfos too. Make
701 : : * sure this RestrictInfo has its own relid sets before we modify them.
702 : : * (In present usage, clause_relids is probably not shared, but
703 : : * required_relids could be; let's not assume anything.)
704 : : */
705 : 3526 : rinfo->clause_relids = bms_copy(rinfo->clause_relids);
706 : 3526 : rinfo->clause_relids = bms_del_member(rinfo->clause_relids, relid);
707 : 3526 : rinfo->clause_relids = bms_del_member(rinfo->clause_relids, ojrelid);
708 : : /* Likewise for required_relids */
709 : 3526 : rinfo->required_relids = bms_copy(rinfo->required_relids);
710 : 3526 : rinfo->required_relids = bms_del_member(rinfo->required_relids, relid);
711 : 3526 : rinfo->required_relids = bms_del_member(rinfo->required_relids, ojrelid);
712 : : /* Likewise for incompatible_relids */
71 713 : 3526 : rinfo->incompatible_relids = bms_copy(rinfo->incompatible_relids);
714 : 3526 : rinfo->incompatible_relids = bms_del_member(rinfo->incompatible_relids, relid);
715 : 3526 : rinfo->incompatible_relids = bms_del_member(rinfo->incompatible_relids, ojrelid);
716 : : /* Likewise for outer_relids */
717 : 3526 : rinfo->outer_relids = bms_copy(rinfo->outer_relids);
718 : 3526 : rinfo->outer_relids = bms_del_member(rinfo->outer_relids, relid);
719 : 3526 : rinfo->outer_relids = bms_del_member(rinfo->outer_relids, ojrelid);
720 : : /* Likewise for left_relids */
721 : 3526 : rinfo->left_relids = bms_copy(rinfo->left_relids);
722 : 3526 : rinfo->left_relids = bms_del_member(rinfo->left_relids, relid);
723 : 3526 : rinfo->left_relids = bms_del_member(rinfo->left_relids, ojrelid);
724 : : /* Likewise for right_relids */
725 : 3526 : rinfo->right_relids = bms_copy(rinfo->right_relids);
726 : 3526 : rinfo->right_relids = bms_del_member(rinfo->right_relids, relid);
727 : 3526 : rinfo->right_relids = bms_del_member(rinfo->right_relids, ojrelid);
728 : :
729 : : /* If it's an OR, recurse to clean up sub-clauses */
1236 730 [ + + ]: 3526 : if (restriction_is_or_clause(rinfo))
731 : : {
732 : : ListCell *lc;
733 : :
734 [ - + ]: 5 : Assert(is_orclause(rinfo->orclause));
735 [ + - + + : 15 : foreach(lc, ((BoolExpr *) rinfo->orclause)->args)
+ + ]
736 : : {
737 : 10 : Node *orarg = (Node *) lfirst(lc);
738 : :
739 : : /* OR arguments should be ANDs or sub-RestrictInfos */
740 [ - + ]: 10 : if (is_andclause(orarg))
741 : : {
1236 tgl@sss.pgh.pa.us 742 :UBC 0 : List *andargs = ((BoolExpr *) orarg)->args;
743 : : ListCell *lc2;
744 : :
745 [ # # # # : 0 : foreach(lc2, andargs)
# # ]
746 : : {
747 : 0 : RestrictInfo *rinfo2 = lfirst_node(RestrictInfo, lc2);
748 : :
749 : 0 : remove_rel_from_restrictinfo(rinfo2, relid, ojrelid);
750 : : }
751 : : }
752 : : else
753 : : {
1236 tgl@sss.pgh.pa.us 754 :CBC 10 : RestrictInfo *rinfo2 = castNode(RestrictInfo, orarg);
755 : :
756 : 10 : remove_rel_from_restrictinfo(rinfo2, relid, ojrelid);
757 : : }
758 : : }
759 : : }
760 : 3526 : }
761 : :
762 : : /*
763 : : * Remove any references to relid or ojrelid from the EquivalenceClass.
764 : : *
765 : : * We fix the EC and EM relid sets to ensure that implied join equalities will
766 : : * be generated at the appropriate join level(s). We also strip the removed
767 : : * rel from PlaceHolderVars embedded in member expressions; a member's
768 : : * em_relids reflects ph_eval_at rather than the PHV's phrels, so the latter
769 : : * can still mention the removed rel even when em_relids does not. Like
770 : : * remove_rel_from_restrictinfo, we don't bother with nullingrel bits in
771 : : * contained plain Vars.
772 : : */
773 : : static void
8 rguo@postgresql.org 774 : 40741 : remove_rel_from_eclass(PlannerInfo *root, EquivalenceClass *ec,
775 : : int relid, int ojrelid)
776 : : {
777 : : ListCell *lc;
778 : :
779 : : /*
780 : : * Strip the removed rel/join from PlaceHolderVars in member expressions.
781 : : * This is needed even when the EC's relids don't mention the removed rel.
782 : : * Plain Vars and Consts can't contain a PlaceHolderVar, so skip them.
783 : : */
8 rguo@postgresql.org 784 [ + + ]:GNC 40741 : if (root->glob->lastPHId != 0)
785 : : {
8 rguo@postgresql.org 786 [ + + + + :CBC 2160 : foreach_node(EquivalenceMember, em, ec->ec_members)
+ + ]
787 : : {
788 [ + + + + ]: 814 : if (!IsA(em->em_expr, Var) && !IsA(em->em_expr, Const))
789 : 83 : em->em_expr = (Expr *)
8 rguo@postgresql.org 790 :GNC 83 : remove_rel_from_phvs((Node *) em->em_expr, relid, ojrelid);
791 : : }
792 : : }
793 : :
8 rguo@postgresql.org 794 [ + + + + ]:CBC 40741 : if (!bms_is_member(relid, ec->ec_relids) &&
8 rguo@postgresql.org 795 [ + - ]:GNC 28858 : !bms_is_member(ojrelid, ec->ec_relids))
8 rguo@postgresql.org 796 :CBC 28858 : return;
797 : :
798 : : /* Fix up the EC's overall relids */
71 rguo@postgresql.org 799 :GNC 11883 : ec->ec_relids = bms_del_member(ec->ec_relids, relid);
800 : 11883 : ec->ec_relids = bms_del_member(ec->ec_relids, ojrelid);
801 : :
802 : : /*
803 : : * We don't expect any EC child members to exist at this point. Ensure
804 : : * that's the case, otherwise, we might be getting asked to do something
805 : : * this function hasn't been coded for.
806 : : */
448 drowley@postgresql.o 807 [ - + ]:CBC 11883 : Assert(ec->ec_childmembers == NULL);
808 : :
809 : : /*
810 : : * Fix up the member expressions. Any non-const member that ends with
811 : : * empty em_relids must be a Var or PHV of the removed relation. We don't
812 : : * need it anymore, so we can drop it.
813 : : */
1111 tgl@sss.pgh.pa.us 814 [ + + + + : 27183 : foreach(lc, ec->ec_members)
+ + ]
815 : : {
816 : 15300 : EquivalenceMember *cur_em = (EquivalenceMember *) lfirst(lc);
817 : :
818 [ + + - + ]: 18717 : if (bms_is_member(relid, cur_em->em_relids) ||
71 rguo@postgresql.org 819 :GNC 3417 : bms_is_member(ojrelid, cur_em->em_relids))
820 : : {
1111 tgl@sss.pgh.pa.us 821 [ - + ]:CBC 11883 : Assert(!cur_em->em_is_const);
822 : : /* em_relids is likely to be shared with some RestrictInfo */
71 tgl@sss.pgh.pa.us 823 :GNC 11883 : cur_em->em_relids = bms_copy(cur_em->em_relids);
rguo@postgresql.org 824 : 11883 : cur_em->em_relids = bms_del_member(cur_em->em_relids, relid);
825 : 11883 : cur_em->em_relids = bms_del_member(cur_em->em_relids, ojrelid);
1111 tgl@sss.pgh.pa.us 826 [ + + ]:CBC 11883 : if (bms_is_empty(cur_em->em_relids))
827 : 11863 : ec->ec_members = foreach_delete_current(ec->ec_members, lc);
828 : : }
829 : : }
830 : :
831 : : /* Fix up the source clauses, in case we can re-use them later */
832 [ + + + + : 15300 : foreach(lc, ec->ec_sources)
+ + ]
833 : : {
834 : 3417 : RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
835 : :
71 rguo@postgresql.org 836 :GNC 3417 : remove_rel_from_restrictinfo(rinfo, relid, ojrelid);
837 : : }
838 : :
839 : : /*
840 : : * Rather than expend code on fixing up any already-derived clauses, just
841 : : * drop them. (At this point, any such clauses would be base restriction
842 : : * clauses, which we'd not need anymore anyway.)
843 : : */
452 amitlan@postgresql.o 844 :CBC 11883 : ec_clear_derived_clauses(ec);
845 : : }
846 : :
847 : : /*
848 : : * Remove any references to the specified RT index(es) from the phrels (and
849 : : * phnullingrels) of every PlaceHolderVar in the given expression.
850 : : *
851 : : * remove_rel_from_query() fixes up the relid sets of RestrictInfos and
852 : : * EquivalenceMembers, but not the PlaceHolderVars embedded in their
853 : : * expressions. That's normally fine, but such an expression may later be
854 : : * translated for an appendrel child and have its relids recomputed by
855 : : * pull_varnos(). A leftover removed relid in phrels would then make
856 : : * pull_varnos() reference a nonexistent rel, so we strip it here to match the
857 : : * canonical PlaceHolderVar.
858 : : */
859 : : static Node *
8 rguo@postgresql.org 860 : 207 : remove_rel_from_phvs(Node *node, int relid, int ojrelid)
861 : : {
862 : 207 : Relids removable = bms_add_member(bms_make_singleton(relid), ojrelid);
863 : :
864 : 207 : return remove_rel_from_phvs_mutator(node, removable);
865 : : }
866 : :
867 : : static Node *
868 : 1142 : remove_rel_from_phvs_mutator(Node *node, Relids removable)
869 : : {
870 [ + + ]: 1142 : if (node == NULL)
871 : 55 : return NULL;
872 [ + + ]: 1087 : if (IsA(node, PlaceHolderVar))
873 : : {
874 : 75 : PlaceHolderVar *phv = (PlaceHolderVar *) node;
875 : : Relids newphrels;
876 : :
877 : : /* Upper-level PlaceHolderVars should be long gone at this point */
878 [ - + ]: 75 : Assert(phv->phlevelsup == 0);
879 : :
880 : : /* Copy the PlaceHolderVar and mutate what's below ... */
881 : : phv = (PlaceHolderVar *)
882 : 75 : expression_tree_mutator(node,
883 : : remove_rel_from_phvs_mutator,
884 : : removable);
885 : :
886 : : /*
887 : : * ... then strip the removed rels from its relid sets.
888 : : *
889 : : * If stripping would empty phrels, the PHV is evaluated only at the
890 : : * removed relation(s); it then belongs to an EquivalenceMember that
891 : : * the caller drops immediately afterwards. Leave such a PHV
892 : : * untouched rather than build one with empty phrels, which the rest
893 : : * of the planner assumes never occurs.
894 : : */
895 : 75 : newphrels = bms_difference(phv->phrels, removable);
896 [ + + ]: 75 : if (!bms_is_empty(newphrels))
897 : : {
898 : 65 : phv->phrels = newphrels;
899 : 65 : phv->phnullingrels = bms_difference(phv->phnullingrels,
900 : : removable);
901 : : }
902 : :
903 : 75 : return (Node *) phv;
904 : : }
905 : 1012 : return expression_tree_mutator(node,
906 : : remove_rel_from_phvs_mutator,
907 : : removable);
908 : : }
909 : :
910 : : /*
911 : : * Remove any occurrences of the target relid from a joinlist structure.
912 : : *
913 : : * It's easiest to build a whole new list structure, so we handle it that
914 : : * way. Efficiency is not a big deal here.
915 : : *
916 : : * *nremoved is incremented by the number of occurrences removed (there
917 : : * should be exactly one, but the caller checks that).
918 : : */
919 : : static List *
5938 tgl@sss.pgh.pa.us 920 : 9261 : remove_rel_from_joinlist(List *joinlist, int relid, int *nremoved)
921 : : {
922 : 9261 : List *result = NIL;
923 : : ListCell *jl;
924 : :
925 [ + - + + : 35641 : foreach(jl, joinlist)
+ + ]
926 : : {
927 : 26380 : Node *jlnode = (Node *) lfirst(jl);
928 : :
929 [ + + ]: 26380 : if (IsA(jlnode, RangeTblRef))
930 : : {
931 : 26130 : int varno = ((RangeTblRef *) jlnode)->rtindex;
932 : :
933 [ + + ]: 26130 : if (varno == relid)
934 : 9011 : (*nremoved)++;
935 : : else
936 : 17119 : result = lappend(result, jlnode);
937 : : }
938 [ + - ]: 250 : else if (IsA(jlnode, List))
939 : : {
940 : : /* Recurse to handle subproblem */
941 : : List *sublist;
942 : :
943 : 250 : sublist = remove_rel_from_joinlist((List *) jlnode,
944 : : relid, nremoved);
945 : : /* Avoid including empty sub-lists in the result */
946 [ + - ]: 250 : if (sublist)
947 : 250 : result = lappend(result, sublist);
948 : : }
949 : : else
950 : : {
5938 tgl@sss.pgh.pa.us 951 [ # # ]:UBC 0 : elog(ERROR, "unrecognized joinlist node type: %d",
952 : : (int) nodeTag(jlnode));
953 : : }
954 : : }
955 : :
5938 tgl@sss.pgh.pa.us 956 :CBC 9261 : return result;
957 : : }
958 : :
959 : :
960 : : /*
961 : : * reduce_unique_semijoins
962 : : * Check for semijoins that can be simplified to plain inner joins
963 : : * because the inner relation is provably unique for the join clauses.
964 : : *
965 : : * Ideally this would happen during reduce_outer_joins, but we don't have
966 : : * enough information at that point.
967 : : *
968 : : * To perform the strength reduction when applicable, we need only delete
969 : : * the semijoin's SpecialJoinInfo from root->join_info_list. (We don't
970 : : * bother fixing the join type attributed to it in the query jointree,
971 : : * since that won't be consulted again.)
972 : : */
973 : : void
3347 974 : 246771 : reduce_unique_semijoins(PlannerInfo *root)
975 : : {
976 : : ListCell *lc;
977 : :
978 : : /*
979 : : * Scan the join_info_list to find semijoins.
980 : : */
2542 981 [ + + + + : 280826 : foreach(lc, root->join_info_list)
+ + ]
982 : : {
3347 983 : 34055 : SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);
984 : : int innerrelid;
985 : : RelOptInfo *innerrel;
986 : : Relids joinrelids;
987 : : List *restrictlist;
988 : :
989 : : /*
990 : : * Must be a semijoin to a single baserel, else we aren't going to be
991 : : * able to do anything with it.
992 : : */
1247 993 [ + + ]: 34055 : if (sjinfo->jointype != JOIN_SEMI)
3347 994 : 33818 : continue;
995 : :
996 [ + + ]: 4030 : if (!bms_get_singleton_member(sjinfo->min_righthand, &innerrelid))
997 : 140 : continue;
998 : :
999 : 3890 : innerrel = find_base_rel(root, innerrelid);
1000 : :
1001 : : /*
1002 : : * Before we trouble to run generate_join_implied_equalities, make a
1003 : : * quick check to eliminate cases in which we will surely be unable to
1004 : : * prove uniqueness of the innerrel.
1005 : : */
1006 [ + + ]: 3890 : if (!rel_supports_distinctness(root, innerrel))
1007 : 811 : continue;
1008 : :
1009 : : /* Compute the relid set for the join we are considering */
1010 : 3079 : joinrelids = bms_union(sjinfo->min_lefthand, sjinfo->min_righthand);
1247 1011 [ - + ]: 3079 : Assert(sjinfo->ojrelid == 0); /* SEMI joins don't have RT indexes */
1012 : :
1013 : : /*
1014 : : * Since we're only considering a single-rel RHS, any join clauses it
1015 : : * has must be clauses linking it to the semijoin's min_lefthand. We
1016 : : * can also consider EC-derived join clauses.
1017 : : */
1018 : : restrictlist =
3347 1019 : 3079 : list_concat(generate_join_implied_equalities(root,
1020 : : joinrelids,
1021 : : sjinfo->min_lefthand,
1022 : : innerrel,
1023 : : NULL),
1024 : 3079 : innerrel->joininfo);
1025 : :
1026 : : /* Test whether the innerrel is unique for those clauses. */
2993 1027 [ + + ]: 3079 : if (!innerrel_is_unique(root,
1028 : : joinrelids, sjinfo->min_lefthand, innerrel,
1029 : : JOIN_SEMI, restrictlist, true))
3347 1030 : 2842 : continue;
1031 : :
1032 : : /* OK, remove the SpecialJoinInfo from the list. */
2542 1033 : 237 : root->join_info_list = foreach_delete_current(root->join_info_list, lc);
1034 : : }
3347 1035 : 246771 : }
1036 : :
1037 : :
1038 : : /*
1039 : : * rel_supports_distinctness
1040 : : * Could the relation possibly be proven distinct on some set of columns?
1041 : : *
1042 : : * This is effectively a pre-checking function for rel_is_distinct_for().
1043 : : * It must return true if rel_is_distinct_for() could possibly return true
1044 : : * with this rel, but it should not expend a lot of cycles. The idea is
1045 : : * that callers can avoid doing possibly-expensive processing to compute
1046 : : * rel_is_distinct_for()'s argument lists if the call could not possibly
1047 : : * succeed.
1048 : : */
1049 : : static bool
3736 1050 : 543800 : rel_supports_distinctness(PlannerInfo *root, RelOptInfo *rel)
1051 : : {
1052 : : /* We only know about baserels ... */
1053 [ + + ]: 543800 : if (rel->reloptkind != RELOPT_BASEREL)
1054 : 200062 : return false;
1055 [ + + ]: 343738 : if (rel->rtekind == RTE_RELATION)
1056 : : {
1057 : : /*
1058 : : * For a plain relation, we only know how to prove uniqueness by
1059 : : * reference to unique indexes. Make sure there's at least one
1060 : : * suitable unique index. It must be immediately enforced, and not a
1061 : : * partial index. (Keep these conditions in sync with
1062 : : * relation_has_unique_index_for!)
1063 : : */
1064 : : ListCell *lc;
1065 : :
1066 [ + + + + : 423174 : foreach(lc, rel->indexlist)
+ + ]
1067 : : {
1068 : 365013 : IndexOptInfo *ind = (IndexOptInfo *) lfirst(lc);
1069 : :
1107 drowley@postgresql.o 1070 [ + + + - : 365013 : if (ind->unique && ind->immediate && ind->indpred == NIL)
+ + ]
3736 tgl@sss.pgh.pa.us 1071 : 259930 : return true;
1072 : : }
1073 : : }
1074 [ + + ]: 25647 : else if (rel->rtekind == RTE_SUBQUERY)
1075 : : {
1076 : 9782 : Query *subquery = root->simple_rte_array[rel->relid]->subquery;
1077 : :
1078 : : /* Check if the subquery has any qualities that support distinctness */
1079 [ + + ]: 9782 : if (query_supports_distinctness(subquery))
1080 : 8414 : return true;
1081 : : }
1082 : : /* We have no proof rules for any other rtekinds. */
1083 : 75394 : return false;
1084 : : }
1085 : :
1086 : : /*
1087 : : * rel_is_distinct_for
1088 : : * Does the relation return only distinct rows according to clause_list?
1089 : : *
1090 : : * clause_list is a list of join restriction clauses involving this rel and
1091 : : * some other one. Return true if no two rows emitted by this rel could
1092 : : * possibly join to the same row of the other rel.
1093 : : *
1094 : : * The caller must have already determined that each condition is a
1095 : : * mergejoinable equality with an expression in this relation on one side, and
1096 : : * an expression not involving this relation on the other. The transient
1097 : : * outer_is_left flag is used to identify which side references this relation:
1098 : : * left side if outer_is_left is false, right side if it is true.
1099 : : *
1100 : : * Note that the passed-in clause_list may be destructively modified! This
1101 : : * is OK for current uses, because the clause_list is built by the caller for
1102 : : * the sole purpose of passing to this function.
1103 : : *
1104 : : * (*extra_clauses) to be set to the right sides of baserestrictinfo clauses,
1105 : : * looking like "x = const" if distinctness is derived from such clauses, not
1106 : : * joininfo clauses. Pass NULL to the extra_clauses if this value is not
1107 : : * needed.
1108 : : */
1109 : : static bool
502 akorotkov@postgresql 1110 : 177356 : rel_is_distinct_for(PlannerInfo *root, RelOptInfo *rel, List *clause_list,
1111 : : List **extra_clauses)
1112 : : {
1113 : : /*
1114 : : * We could skip a couple of tests here if we assume all callers checked
1115 : : * rel_supports_distinctness first, but it doesn't seem worth taking any
1116 : : * risk for.
1117 : : */
3736 tgl@sss.pgh.pa.us 1118 [ - + ]: 177356 : if (rel->reloptkind != RELOPT_BASEREL)
3736 tgl@sss.pgh.pa.us 1119 :UBC 0 : return false;
3736 tgl@sss.pgh.pa.us 1120 [ + + ]:CBC 177356 : if (rel->rtekind == RTE_RELATION)
1121 : : {
1122 : : /*
1123 : : * Examine the indexes to see if we have a matching unique index.
1124 : : * relation_has_unique_index_for automatically adds any usable
1125 : : * restriction clauses for the rel, so we needn't do that here.
1126 : : */
315 rguo@postgresql.org 1127 [ + + ]:GNC 172962 : if (relation_has_unique_index_for(root, rel, clause_list, extra_clauses))
3736 tgl@sss.pgh.pa.us 1128 :CBC 103530 : return true;
1129 : : }
1130 [ + - ]: 4394 : else if (rel->rtekind == RTE_SUBQUERY)
1131 : : {
1132 : 4394 : Index relid = rel->relid;
1133 : 4394 : Query *subquery = root->simple_rte_array[relid]->subquery;
56 rguo@postgresql.org 1134 : 4394 : List *distinct_cols = NIL;
1135 : : ListCell *l;
1136 : :
1137 : : /*
1138 : : * Build the argument list for query_is_distinct_for: a list of
1139 : : * DistinctColInfo entries, each holding an output column number that
1140 : : * the query needs to be distinct over, the equality operator that the
1141 : : * column needs to be distinct according to, and that operator's input
1142 : : * collation. The collation matters because the subquery's own
1143 : : * DISTINCT / GROUP BY / set-op proves uniqueness under its own
1144 : : * collation, which need not agree with the operator's.
1145 : : *
1146 : : * (XXX we are not considering restriction clauses attached to the
1147 : : * subquery; is that worth doing?)
1148 : : */
3736 tgl@sss.pgh.pa.us 1149 [ + + + + : 8418 : foreach(l, clause_list)
+ + ]
1150 : : {
3368 1151 : 4024 : RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
1152 : : OpExpr *opexpr;
1153 : : Var *var;
1154 : : DistinctColInfo *dcinfo;
1155 : :
1156 : : /*
1157 : : * The caller's mergejoinability test should have selected only
1158 : : * OpExprs. The operator might be a cross-type operator and thus
1159 : : * not exactly the same operator the subquery would consider;
1160 : : * that's all right since query_is_distinct_for can resolve such
1161 : : * cases.
1162 : : */
56 rguo@postgresql.org 1163 : 4024 : opexpr = castNode(OpExpr, rinfo->clause);
1164 : :
1165 : : /* caller identified the inner side for us */
3736 tgl@sss.pgh.pa.us 1166 [ + + ]: 4024 : if (rinfo->outer_is_left)
1167 : 3663 : var = (Var *) get_rightop(rinfo->clause);
1168 : : else
1169 : 361 : var = (Var *) get_leftop(rinfo->clause);
1170 : :
1171 : : /*
1172 : : * We may ignore any RelabelType node above the operand. (There
1173 : : * won't be more than one, since eval_const_expressions() has been
1174 : : * applied already.)
1175 : : */
3208 1176 [ + - + + ]: 4024 : if (var && IsA(var, RelabelType))
1177 : 2748 : var = (Var *) ((RelabelType *) var)->arg;
1178 : :
1179 : : /*
1180 : : * If inner side isn't a Var referencing a subquery output column,
1181 : : * this clause doesn't help us.
1182 : : */
3736 1183 [ + - + + ]: 4024 : if (!var || !IsA(var, Var) ||
1184 [ + - - + ]: 3999 : var->varno != relid || var->varlevelsup != 0)
1185 : 25 : continue;
1186 : :
56 rguo@postgresql.org 1187 : 3999 : dcinfo = palloc(sizeof(DistinctColInfo));
1188 : 3999 : dcinfo->colno = var->varattno;
1189 : 3999 : dcinfo->opid = opexpr->opno;
1190 : 3999 : dcinfo->collid = opexpr->inputcollid;
1191 : 3999 : distinct_cols = lappend(distinct_cols, dcinfo);
1192 : : }
1193 : :
56 rguo@postgresql.org 1194 [ + + ]:GNC 4394 : if (query_is_distinct_for(subquery, distinct_cols))
3736 tgl@sss.pgh.pa.us 1195 :CBC 575 : return true;
1196 : : }
1197 : 73251 : return false;
1198 : : }
1199 : :
1200 : :
1201 : : /*
1202 : : * query_supports_distinctness - could the query possibly be proven distinct
1203 : : * on some set of output columns?
1204 : : *
1205 : : * This is effectively a pre-checking function for query_is_distinct_for().
1206 : : * It must return true if query_is_distinct_for() could possibly return true
1207 : : * with this query, but it should not expend a lot of cycles. The idea is
1208 : : * that callers can avoid doing possibly-expensive processing to compute
1209 : : * query_is_distinct_for()'s argument lists if the call could not possibly
1210 : : * succeed.
1211 : : */
1212 : : bool
4368 1213 : 9782 : query_supports_distinctness(Query *query)
1214 : : {
1215 : : /* SRFs break distinctness except with DISTINCT, see below */
3139 1216 [ + + + - ]: 9782 : if (query->hasTargetSRFs && query->distinctClause == NIL)
3577 1217 : 763 : return false;
1218 : :
1219 : : /* check for features we can prove distinctness with */
4368 1220 [ + + ]: 9019 : if (query->distinctClause != NIL ||
1221 [ + + ]: 8844 : query->groupClause != NIL ||
4063 andres@anarazel.de 1222 [ + + ]: 8668 : query->groupingSets != NIL ||
4368 tgl@sss.pgh.pa.us 1223 [ + + ]: 8628 : query->hasAggs ||
1224 [ + - ]: 7123 : query->havingQual ||
1225 [ + + ]: 7123 : query->setOperations)
1226 : 8414 : return true;
1227 : :
1228 : 605 : return false;
1229 : : }
1230 : :
1231 : : /*
1232 : : * query_is_distinct_for - does query never return duplicates of the
1233 : : * specified columns?
1234 : : *
1235 : : * query is a not-yet-planned subquery (in current usage, it's always from
1236 : : * a subquery RTE, which the planner avoids scribbling on).
1237 : : *
1238 : : * distinct_cols is a list of DistinctColInfo, one per requested output column.
1239 : : * Each entry names the subquery output column number we want distinct, the
1240 : : * upper-level equality operator we'll compare values with, and that operator's
1241 : : * input collation. We are interested in whether rows consisting of just these
1242 : : * columns are certain to be distinct.
1243 : : *
1244 : : * "Distinctness" is defined according to whether the corresponding upper-level
1245 : : * equality operators would think the values are distinct. (Note: each opid
1246 : : * could be a cross-type operator, and thus not exactly the equality operator
1247 : : * that the subquery would use itself. We use equality_ops_are_compatible() to
1248 : : * check compatibility. That looks at opfamily membership for index AMs that
1249 : : * have declared that they support consistent equality semantics within an
1250 : : * opfamily, and so should give trustworthy answers for all operators that we
1251 : : * might need to deal with here.)
1252 : : *
1253 : : * The collid must also agree on equality with the collation the subquery's own
1254 : : * DISTINCT/GROUP BY/set-op uses to deduplicate the column, else the subquery's
1255 : : * distinctness does not carry over to the caller's equality semantics. Two
1256 : : * collations agree on equality if they match or if both are deterministic (in
1257 : : * which case both reduce equality to byte-equality; see CREATE COLLATION).
1258 : : */
1259 : : bool
56 rguo@postgresql.org 1260 :GNC 4394 : query_is_distinct_for(Query *query, List *distinct_cols)
1261 : : {
1262 : : ListCell *l;
1263 : : DistinctColInfo *dcinfo;
1264 : :
1265 : : /*
1266 : : * DISTINCT (including DISTINCT ON) guarantees uniqueness if all the
1267 : : * columns in the DISTINCT clause appear in colnos and operator semantics
1268 : : * match. This is true even if there are SRFs in the DISTINCT columns or
1269 : : * elsewhere in the tlist.
1270 : : */
4368 tgl@sss.pgh.pa.us 1271 [ + + ]:CBC 4394 : if (query->distinctClause)
1272 : : {
1273 [ + - + + : 180 : foreach(l, query->distinctClause)
+ + ]
1274 : : {
1275 : 145 : SortGroupClause *sgc = (SortGroupClause *) lfirst(l);
1276 : 145 : TargetEntry *tle = get_sortgroupclause_tle(sgc,
1277 : : query->targetList);
1278 : :
56 rguo@postgresql.org 1279 : 145 : dcinfo = distinct_col_search(tle->resno, distinct_cols);
1280 [ + + ]: 145 : if (dcinfo == NULL ||
1281 [ + - ]: 90 : !equality_ops_are_compatible(dcinfo->opid, sgc->eqop) ||
1282 [ + + ]: 90 : !collations_agree_on_equality(dcinfo->collid,
1283 : 90 : exprCollation((Node *) tle->expr)))
1284 : : break; /* exit early if no match */
1285 : : }
4368 tgl@sss.pgh.pa.us 1286 [ + + ]: 130 : if (l == NULL) /* had matches for all? */
1287 : 35 : return true;
1288 : : }
1289 : :
1290 : : /*
1291 : : * Otherwise, a set-returning function in the query's targetlist can
1292 : : * result in returning duplicate rows, despite any grouping that might
1293 : : * occur before tlist evaluation. (If all tlist SRFs are within GROUP BY
1294 : : * columns, it would be safe because they'd be expanded before grouping.
1295 : : * But it doesn't currently seem worth the effort to check for that.)
1296 : : */
3139 1297 [ - + ]: 4359 : if (query->hasTargetSRFs)
3139 tgl@sss.pgh.pa.us 1298 :UBC 0 : return false;
1299 : :
1300 : : /*
1301 : : * Similarly, GROUP BY without GROUPING SETS guarantees uniqueness if all
1302 : : * the grouped columns appear in colnos and operator semantics match.
1303 : : */
4063 andres@anarazel.de 1304 [ + + + + ]:CBC 4359 : if (query->groupClause && !query->groupingSets)
1305 : : {
4368 tgl@sss.pgh.pa.us 1306 [ + - + + : 206 : foreach(l, query->groupClause)
+ + ]
1307 : : {
1308 : 144 : SortGroupClause *sgc = (SortGroupClause *) lfirst(l);
1309 : 144 : TargetEntry *tle = get_sortgroupclause_tle(sgc,
1310 : : query->targetList);
1311 : :
56 rguo@postgresql.org 1312 : 144 : dcinfo = distinct_col_search(tle->resno, distinct_cols);
1313 [ + + ]: 144 : if (dcinfo == NULL ||
1314 [ + - ]: 107 : !equality_ops_are_compatible(dcinfo->opid, sgc->eqop) ||
1315 [ + + ]: 107 : !collations_agree_on_equality(dcinfo->collid,
1316 : 107 : exprCollation((Node *) tle->expr)))
1317 : : break; /* exit early if no match */
1318 : : }
4368 tgl@sss.pgh.pa.us 1319 [ + + ]: 109 : if (l == NULL) /* had matches for all? */
1320 : 62 : return true;
1321 : : }
4063 andres@anarazel.de 1322 [ + + ]: 4250 : else if (query->groupingSets)
1323 : : {
1324 : : List *gsets;
1325 : :
1326 : : /*
1327 : : * If we have grouping sets with expressions, we probably don't have
1328 : : * uniqueness and analysis would be hard. Punt.
1329 : : */
4063 andres@anarazel.de 1330 [ + + ]:GBC 50 : if (query->groupClause)
1331 : 10 : return false;
1332 : :
1333 : : /*
1334 : : * If we have no groupClause (therefore no grouping expressions), we
1335 : : * might have one or many empty grouping sets. If there's just one,
1336 : : * or if the DISTINCT clause is used on the GROUP BY, then we're
1337 : : * returning only one row and are certainly unique. But otherwise, we
1338 : : * know we're certainly not unique.
1339 : : */
203 rguo@postgresql.org 1340 [ + + ]:GNC 40 : if (query->groupDistinct)
4063 andres@anarazel.de 1341 :GBC 5 : return true;
1342 : :
203 rguo@postgresql.org 1343 :GNC 35 : gsets = expand_grouping_sets(query->groupingSets, false, -1);
1344 : :
1345 : 35 : return (list_length(gsets) == 1);
1346 : : }
1347 : : else
1348 : : {
1349 : : /*
1350 : : * If we have no GROUP BY, but do have aggregates or HAVING, then the
1351 : : * result is at most one row so it's surely unique, for any operators.
1352 : : */
4368 tgl@sss.pgh.pa.us 1353 [ + + - + ]:CBC 4200 : if (query->hasAggs || query->havingQual)
1354 : 408 : return true;
1355 : : }
1356 : :
1357 : : /*
1358 : : * UNION, INTERSECT, EXCEPT guarantee uniqueness of the whole output row,
1359 : : * except with ALL.
1360 : : */
1361 [ + + ]: 3839 : if (query->setOperations)
1362 : : {
3416 peter_e@gmx.net 1363 : 3697 : SetOperationStmt *topop = castNode(SetOperationStmt, query->setOperations);
1364 : :
4368 tgl@sss.pgh.pa.us 1365 [ - + ]: 3697 : Assert(topop->op != SETOP_NONE);
1366 : :
1367 [ + + ]: 3697 : if (!topop->all)
1368 : : {
1369 : : ListCell *lg;
1370 : :
1371 : : /* We're good if all the nonjunk output columns are in colnos */
1372 : 93 : lg = list_head(topop->groupClauses);
1373 [ + - + + : 148 : foreach(l, query->targetList)
+ + ]
1374 : : {
1375 : 98 : TargetEntry *tle = (TargetEntry *) lfirst(l);
1376 : : SortGroupClause *sgc;
1377 : :
1378 [ - + ]: 98 : if (tle->resjunk)
4368 tgl@sss.pgh.pa.us 1379 :UBC 0 : continue; /* ignore resjunk columns */
1380 : :
1381 : : /* non-resjunk columns should have grouping clauses */
4368 tgl@sss.pgh.pa.us 1382 [ - + ]:CBC 98 : Assert(lg != NULL);
1383 : 98 : sgc = (SortGroupClause *) lfirst(lg);
2542 1384 : 98 : lg = lnext(topop->groupClauses, lg);
1385 : :
56 rguo@postgresql.org 1386 : 98 : dcinfo = distinct_col_search(tle->resno, distinct_cols);
1387 [ + + ]: 98 : if (dcinfo == NULL ||
1388 [ + - ]: 65 : !equality_ops_are_compatible(dcinfo->opid, sgc->eqop) ||
1389 [ + + ]: 65 : !collations_agree_on_equality(dcinfo->collid,
1390 : 65 : exprCollation((Node *) tle->expr)))
1391 : : break; /* exit early if no match */
1392 : : }
4368 tgl@sss.pgh.pa.us 1393 [ + + ]: 93 : if (l == NULL) /* had matches for all? */
1394 : 50 : return true;
1395 : : }
1396 : : }
1397 : :
1398 : : /*
1399 : : * XXX Are there any other cases in which we can easily see the result
1400 : : * must be distinct?
1401 : : *
1402 : : * If you do add more smarts to this function, be sure to update
1403 : : * query_supports_distinctness() to match.
1404 : : */
1405 : :
1406 : 3789 : return false;
1407 : : }
1408 : :
1409 : : /*
1410 : : * distinct_col_search - subroutine for query_is_distinct_for
1411 : : *
1412 : : * If colno matches the colno field of an entry in distinct_cols, return a
1413 : : * pointer to that entry; else return NULL. (Ordinarily distinct_cols would
1414 : : * not contain duplicate colnos, but if it does, we arbitrarily select the
1415 : : * first match.)
1416 : : */
1417 : : static DistinctColInfo *
56 rguo@postgresql.org 1418 : 387 : distinct_col_search(int colno, List *distinct_cols)
1419 : : {
1420 [ + - + + : 655 : foreach_ptr(DistinctColInfo, dcinfo, distinct_cols)
+ + ]
1421 : : {
1422 [ + + ]: 405 : if (dcinfo->colno == colno)
1423 : 262 : return dcinfo;
1424 : : }
1425 : :
1426 : 125 : return NULL;
1427 : : }
1428 : :
1429 : :
1430 : : /*
1431 : : * innerrel_is_unique
1432 : : * Check if the innerrel provably contains at most one tuple matching any
1433 : : * tuple from the outerrel, based on join clauses in the 'restrictlist'.
1434 : : *
1435 : : * We need an actual RelOptInfo for the innerrel, but it's sufficient to
1436 : : * identify the outerrel by its Relids. This asymmetry supports use of this
1437 : : * function before joinrels have been built. (The caller is expected to
1438 : : * also supply the joinrelids, just to save recalculating that.)
1439 : : *
1440 : : * The proof must be made based only on clauses that will be "joinquals"
1441 : : * rather than "otherquals" at execution. For an inner join there's no
1442 : : * difference; but if the join is outer, we must ignore pushed-down quals,
1443 : : * as those will become "otherquals". Note that this means the answer might
1444 : : * vary depending on whether IS_OUTER_JOIN(jointype); since we cache the
1445 : : * answer without regard to that, callers must take care not to call this
1446 : : * with jointypes that would be classified differently by IS_OUTER_JOIN().
1447 : : *
1448 : : * The actual proof is undertaken by is_innerrel_unique_for(); this function
1449 : : * is a frontend that is mainly concerned with caching the answers.
1450 : : * In particular, the force_cache argument allows overriding the internal
1451 : : * heuristic about whether to cache negative answers; it should be "true"
1452 : : * if making an inquiry that is not part of the normal bottom-up join search
1453 : : * sequence.
1454 : : */
1455 : : bool
3371 tgl@sss.pgh.pa.us 1456 : 586991 : innerrel_is_unique(PlannerInfo *root,
1457 : : Relids joinrelids,
1458 : : Relids outerrelids,
1459 : : RelOptInfo *innerrel,
1460 : : JoinType jointype,
1461 : : List *restrictlist,
1462 : : bool force_cache)
1463 : : {
502 akorotkov@postgresql 1464 : 586991 : return innerrel_is_unique_ext(root, joinrelids, outerrelids, innerrel,
1465 : : jointype, restrictlist, force_cache, NULL);
1466 : : }
1467 : :
1468 : : /*
1469 : : * innerrel_is_unique_ext
1470 : : * Do the same as innerrel_is_unique(), but also set to (*extra_clauses)
1471 : : * additional clauses from a baserestrictinfo list used to prove the
1472 : : * uniqueness.
1473 : : *
1474 : : * A non-NULL extra_clauses indicates that we're checking for self-join and
1475 : : * correspondingly dealing with filtered clauses.
1476 : : */
1477 : : bool
1478 : 588782 : innerrel_is_unique_ext(PlannerInfo *root,
1479 : : Relids joinrelids,
1480 : : Relids outerrelids,
1481 : : RelOptInfo *innerrel,
1482 : : JoinType jointype,
1483 : : List *restrictlist,
1484 : : bool force_cache,
1485 : : List **extra_clauses)
1486 : : {
1487 : : MemoryContext old_context;
1488 : : ListCell *lc;
1489 : : UniqueRelInfo *uniqueRelInfo;
1490 : 588782 : List *outer_exprs = NIL;
1491 : 588782 : bool self_join = (extra_clauses != NULL);
1492 : :
1493 : : /* Certainly can't prove uniqueness when there are no joinclauses */
3371 tgl@sss.pgh.pa.us 1494 [ + + ]: 588782 : if (restrictlist == NIL)
1495 : 79569 : return false;
1496 : :
1497 : : /*
1498 : : * Make a quick check to eliminate cases in which we will surely be unable
1499 : : * to prove uniqueness of the innerrel.
1500 : : */
1501 [ + + ]: 509213 : if (!rel_supports_distinctness(root, innerrel))
1502 : 272205 : return false;
1503 : :
1504 : : /*
1505 : : * Query the cache to see if we've managed to prove that innerrel is
1506 : : * unique for any subset of this outerrel. For non-self-join search, we
1507 : : * don't need an exact match, as extra outerrels can't make the innerrel
1508 : : * any less unique (or more formally, the restrictlist for a join to a
1509 : : * superset outerrel must be a superset of the conditions we successfully
1510 : : * used before). For self-join search, we require an exact match of
1511 : : * outerrels because we need extra clauses to be valid for our case. Also,
1512 : : * for self-join checking we've filtered the clauses list. Thus, we can
1513 : : * match only the result cached for a self-join search for another
1514 : : * self-join check.
1515 : : */
1516 [ + + + + : 257826 : foreach(lc, innerrel->unique_for_rels)
+ + ]
1517 : : {
502 akorotkov@postgresql 1518 : 88902 : uniqueRelInfo = (UniqueRelInfo *) lfirst(lc);
1519 : :
1520 [ + + + + : 88902 : if ((!self_join && bms_is_subset(uniqueRelInfo->outerrelids, outerrelids)) ||
+ + ]
1521 [ + + ]: 57 : (self_join && bms_equal(uniqueRelInfo->outerrelids, outerrelids) &&
1522 [ + + ]: 42 : uniqueRelInfo->self_join))
1523 : : {
1524 [ + + ]: 68084 : if (extra_clauses)
1525 : 10 : *extra_clauses = uniqueRelInfo->extra_clauses;
3371 tgl@sss.pgh.pa.us 1526 : 68084 : return true; /* Success! */
1527 : : }
1528 : : }
1529 : :
1530 : : /*
1531 : : * Conversely, we may have already determined that this outerrel, or some
1532 : : * superset thereof, cannot prove this innerrel to be unique.
1533 : : */
1534 [ + + + + : 169460 : foreach(lc, innerrel->non_unique_for_rels)
+ + ]
1535 : : {
1536 : 884 : Relids unique_for_rels = (Relids) lfirst(lc);
1537 : :
3347 1538 [ + + ]: 884 : if (bms_is_subset(outerrelids, unique_for_rels))
3371 1539 : 348 : return false;
1540 : : }
1541 : :
1542 : : /* No cached information, so try to make the proof. */
2993 1543 [ + + + + ]: 168576 : if (is_innerrel_unique_for(root, joinrelids, outerrelids, innerrel,
1544 : : jointype, restrictlist,
1545 : : self_join ? &outer_exprs : NULL))
1546 : : {
1547 : : /*
1548 : : * Cache the positive result for future probes, being sure to keep it
1549 : : * in the planner_cxt even if we are working in GEQO.
1550 : : *
1551 : : * Note: one might consider trying to isolate the minimal subset of
1552 : : * the outerrels that proved the innerrel unique. But it's not worth
1553 : : * the trouble, because the planner builds up joinrels incrementally
1554 : : * and so we'll see the minimally sufficient outerrels before any
1555 : : * supersets of them anyway.
1556 : : */
3371 1557 : 95562 : old_context = MemoryContextSwitchTo(root->planner_cxt);
502 akorotkov@postgresql 1558 : 95562 : uniqueRelInfo = makeNode(UniqueRelInfo);
1559 : 95562 : uniqueRelInfo->outerrelids = bms_copy(outerrelids);
1560 : 95562 : uniqueRelInfo->self_join = self_join;
1561 : 95562 : uniqueRelInfo->extra_clauses = outer_exprs;
3371 tgl@sss.pgh.pa.us 1562 : 95562 : innerrel->unique_for_rels = lappend(innerrel->unique_for_rels,
1563 : : uniqueRelInfo);
1564 : 95562 : MemoryContextSwitchTo(old_context);
1565 : :
502 akorotkov@postgresql 1566 [ + + ]: 95562 : if (extra_clauses)
1567 : 513 : *extra_clauses = outer_exprs;
3371 tgl@sss.pgh.pa.us 1568 : 95562 : return true; /* Success! */
1569 : : }
1570 : : else
1571 : : {
1572 : : /*
1573 : : * None of the join conditions for outerrel proved innerrel unique, so
1574 : : * we can safely reject this outerrel or any subset of it in future
1575 : : * checks.
1576 : : *
1577 : : * However, in normal planning mode, caching this knowledge is totally
1578 : : * pointless; it won't be queried again, because we build up joinrels
1579 : : * from smaller to larger. It's only useful when using GEQO or
1580 : : * another planner extension that attempts planning multiple times.
1581 : : *
1582 : : * Also, allow callers to override that heuristic and force caching;
1583 : : * that's useful for reduce_unique_semijoins, which calls here before
1584 : : * the normal join search starts.
1585 : : */
314 rhaas@postgresql.org 1586 [ + + - + ]:GNC 73014 : if (force_cache || root->assumeReplanning)
1587 : : {
3371 tgl@sss.pgh.pa.us 1588 :CBC 3190 : old_context = MemoryContextSwitchTo(root->planner_cxt);
1589 : 3190 : innerrel->non_unique_for_rels =
1590 : 3190 : lappend(innerrel->non_unique_for_rels,
3347 1591 : 3190 : bms_copy(outerrelids));
3371 1592 : 3190 : MemoryContextSwitchTo(old_context);
1593 : : }
1594 : :
1595 : 73014 : return false;
1596 : : }
1597 : : }
1598 : :
1599 : : /*
1600 : : * is_innerrel_unique_for
1601 : : * Check if the innerrel provably contains at most one tuple matching any
1602 : : * tuple from the outerrel, based on join clauses in the 'restrictlist'.
1603 : : */
1604 : : static bool
1605 : 168576 : is_innerrel_unique_for(PlannerInfo *root,
1606 : : Relids joinrelids,
1607 : : Relids outerrelids,
1608 : : RelOptInfo *innerrel,
1609 : : JoinType jointype,
1610 : : List *restrictlist,
1611 : : List **extra_clauses)
1612 : : {
1613 : 168576 : List *clause_list = NIL;
1614 : : ListCell *lc;
1615 : :
1616 : : /*
1617 : : * Search for mergejoinable clauses that constrain the inner rel against
1618 : : * the outer rel. If an operator is mergejoinable then it behaves like
1619 : : * equality for some btree opclass, so it's what we want. The
1620 : : * mergejoinability test also eliminates clauses containing volatile
1621 : : * functions, which we couldn't depend on.
1622 : : */
1623 [ + - + + : 374748 : foreach(lc, restrictlist)
+ + ]
1624 : : {
1625 : 206172 : RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(lc);
1626 : :
1627 : : /*
1628 : : * As noted above, if it's a pushed-down clause and we're at an outer
1629 : : * join, we can't use it.
1630 : : */
2993 1631 [ + + ]: 206172 : if (IS_OUTER_JOIN(jointype) &&
1632 [ + + - + ]: 80898 : RINFO_IS_PUSHED_DOWN(restrictinfo, joinrelids))
3371 1633 : 7502 : continue;
1634 : :
1635 : : /* Ignore if it's not a mergejoinable clause */
1636 [ + + ]: 198670 : if (!restrictinfo->can_join ||
1637 [ + + ]: 186052 : restrictinfo->mergeopfamilies == NIL)
1638 : 13319 : continue; /* not mergejoinable */
1639 : :
1640 : : /*
1641 : : * Check if the clause has the form "outer op inner" or "inner op
1642 : : * outer", and if so mark which side is inner.
1643 : : */
3347 1644 [ + + ]: 185351 : if (!clause_sides_match_join(restrictinfo, outerrelids,
1645 : : innerrel->relids))
3371 1646 : 20 : continue; /* no good for these input relations */
1647 : :
1648 : : /* OK, add to the list */
1649 : 185331 : clause_list = lappend(clause_list, restrictinfo);
1650 : : }
1651 : :
1652 : : /* Let rel_is_distinct_for() do the hard work */
502 akorotkov@postgresql 1653 : 168576 : return rel_is_distinct_for(root, innerrel, clause_list, extra_clauses);
1654 : : }
1655 : :
1656 : : /*
1657 : : * Update EC members to point to the remaining relation instead of the removed
1658 : : * one, removing duplicates.
1659 : : *
1660 : : * Restriction clauses for base relations are already distributed to
1661 : : * the respective baserestrictinfo lists (see
1662 : : * generate_implied_equalities_for_column). The above code has already processed
1663 : : * this list and updated these clauses to reference the remaining
1664 : : * relation, so that we can skip them here based on their relids.
1665 : : *
1666 : : * Likewise, we have already processed the join clauses that join the
1667 : : * removed relation to the remaining one.
1668 : : *
1669 : : * Finally, there might be join clauses tying the removed relation to
1670 : : * some third relation. We can't just delete the source clauses and
1671 : : * regenerate them from the EC because the corresponding equality
1672 : : * operators might be missing (see the handling of ec_broken).
1673 : : * Therefore, we will update the references in the source clauses.
1674 : : *
1675 : : * Derived clauses can be generated again, so it is simpler just to
1676 : : * delete them.
1677 : : */
1678 : : static void
1679 : 751 : update_eclasses(EquivalenceClass *ec, int from, int to)
1680 : : {
1681 : 751 : List *new_members = NIL;
1682 : 751 : List *new_sources = NIL;
1683 : :
1684 : : /*
1685 : : * We don't expect any EC child members to exist at this point. Ensure
1686 : : * that's the case, otherwise, we might be getting asked to do something
1687 : : * this function hasn't been coded for.
1688 : : */
448 drowley@postgresql.o 1689 [ - + ]: 751 : Assert(ec->ec_childmembers == NULL);
1690 : :
502 akorotkov@postgresql 1691 [ + - + + : 3076 : foreach_node(EquivalenceMember, em, ec->ec_members)
+ + ]
1692 : : {
1693 : 1574 : bool is_redundant = false;
1694 : :
1695 [ + + ]: 1574 : if (!bms_is_member(from, em->em_relids))
1696 : : {
1697 : 808 : new_members = lappend(new_members, em);
1698 : 808 : continue;
1699 : : }
1700 : :
1701 : 766 : em->em_relids = adjust_relid_set(em->em_relids, from, to);
1702 : 766 : em->em_jdomain->jd_relids = adjust_relid_set(em->em_jdomain->jd_relids, from, to);
1703 : :
1704 : : /* We only process inner joins */
419 1705 : 766 : ChangeVarNodesExtended((Node *) em->em_expr, from, to, 0,
1706 : : replace_relid_callback);
1707 : :
502 1708 [ + + + + : 1552 : foreach_node(EquivalenceMember, other, new_members)
+ + ]
1709 : : {
1710 [ + + ]: 186 : if (!equal(em->em_relids, other->em_relids))
1711 : 20 : continue;
1712 : :
1713 [ + - ]: 166 : if (equal(em->em_expr, other->em_expr))
1714 : : {
1715 : 166 : is_redundant = true;
1716 : 166 : break;
1717 : : }
1718 : : }
1719 : :
1720 [ + + ]: 766 : if (!is_redundant)
1721 : 600 : new_members = lappend(new_members, em);
1722 : : }
1723 : :
1724 : 751 : list_free(ec->ec_members);
1725 : 751 : ec->ec_members = new_members;
1726 : :
452 amitlan@postgresql.o 1727 : 751 : ec_clear_derived_clauses(ec);
1728 : :
1729 : : /* Update EC source expressions */
502 akorotkov@postgresql 1730 [ + + + + : 2325 : foreach_node(RestrictInfo, rinfo, ec->ec_sources)
+ + ]
1731 : : {
1732 : 823 : bool is_redundant = false;
1733 : :
1734 [ + + ]: 823 : if (!bms_is_member(from, rinfo->required_relids))
1735 : : {
1736 : 160 : new_sources = lappend(new_sources, rinfo);
1737 : 160 : continue;
1738 : : }
1739 : :
419 1740 : 663 : ChangeVarNodesExtended((Node *) rinfo, from, to, 0,
1741 : : replace_relid_callback);
1742 : :
1743 : : /*
1744 : : * After switching the clause to the remaining relation, check it for
1745 : : * redundancy with existing ones. We don't have to check for
1746 : : * redundancy with derived clauses, because we've just deleted them.
1747 : : */
502 1748 [ + + + + : 1338 : foreach_node(RestrictInfo, other, new_sources)
+ + ]
1749 : : {
1750 [ + + ]: 22 : if (!equal(rinfo->clause_relids, other->clause_relids))
1751 : 12 : continue;
1752 : :
1753 [ + - ]: 10 : if (equal(rinfo->clause, other->clause))
1754 : : {
1755 : 10 : is_redundant = true;
1756 : 10 : break;
1757 : : }
1758 : : }
1759 : :
1760 [ + + ]: 663 : if (!is_redundant)
1761 : 653 : new_sources = lappend(new_sources, rinfo);
1762 : : }
1763 : :
1764 : 751 : list_free(ec->ec_sources);
1765 : 751 : ec->ec_sources = new_sources;
1766 : 751 : ec->ec_relids = adjust_relid_set(ec->ec_relids, from, to);
1767 : 751 : }
1768 : :
1769 : : /*
1770 : : * "Logically" compares two RestrictInfo's ignoring the 'rinfo_serial' field,
1771 : : * which makes almost every RestrictInfo unique. This type of comparison is
1772 : : * useful when removing duplicates while moving RestrictInfo's from removed
1773 : : * relation to remaining relation during self-join elimination.
1774 : : *
1775 : : * XXX: In the future, we might remove the 'rinfo_serial' field completely and
1776 : : * get rid of this function.
1777 : : */
1778 : : static bool
1779 : 476 : restrict_infos_logically_equal(RestrictInfo *a, RestrictInfo *b)
1780 : : {
1781 : 476 : int saved_rinfo_serial = a->rinfo_serial;
1782 : : bool result;
1783 : :
1784 : 476 : a->rinfo_serial = b->rinfo_serial;
1785 : 476 : result = equal(a, b);
1786 : 476 : a->rinfo_serial = saved_rinfo_serial;
1787 : :
1788 : 476 : return result;
1789 : : }
1790 : :
1791 : : /*
1792 : : * This function adds all non-redundant clauses to the keeping relation
1793 : : * during self-join elimination. That is a contradictory operation. On the
1794 : : * one hand, we reduce the length of the `restrict` lists, which can
1795 : : * impact planning or executing time. Additionally, we improve the
1796 : : * accuracy of cardinality estimation. On the other hand, it is one more
1797 : : * place that can make planning time much longer in specific cases. It
1798 : : * would have been better to avoid calling the equal() function here, but
1799 : : * it's the only way to detect duplicated inequality expressions.
1800 : : *
1801 : : * (*keep_rinfo_list) is given by pointer because it might be altered by
1802 : : * distribute_restrictinfo_to_rels().
1803 : : */
1804 : : static void
1805 : 936 : add_non_redundant_clauses(PlannerInfo *root,
1806 : : List *rinfo_candidates,
1807 : : List **keep_rinfo_list,
1808 : : Index removed_relid)
1809 : : {
1810 [ + + + + : 2652 : foreach_node(RestrictInfo, rinfo, rinfo_candidates)
+ + ]
1811 : : {
1812 : 780 : bool is_redundant = false;
1813 : :
1814 [ - + ]: 780 : Assert(!bms_is_member(removed_relid, rinfo->required_relids));
1815 : :
1816 [ + + + + : 1939 : foreach_node(RestrictInfo, src, (*keep_rinfo_list))
+ + ]
1817 : : {
1818 [ + + ]: 496 : if (!bms_equal(src->clause_relids, rinfo->clause_relids))
1819 : : /* Can't compare trivially different clauses */
1820 : 15 : continue;
1821 : :
1822 [ + - ]: 481 : if (src == rinfo ||
1823 [ + + ]: 481 : (rinfo->parent_ec != NULL &&
1824 [ + + + + ]: 790 : src->parent_ec == rinfo->parent_ec) ||
1825 : 476 : restrict_infos_logically_equal(rinfo, src))
1826 : : {
1827 : 117 : is_redundant = true;
1828 : 117 : break;
1829 : : }
1830 : : }
1831 [ + + ]: 780 : if (!is_redundant)
1832 : 663 : distribute_restrictinfo_to_rels(root, rinfo);
1833 : : }
1834 : 936 : }
1835 : :
1836 : : /*
1837 : : * A custom callback for ChangeVarNodesExtended() providing Self-join
1838 : : * elimination (SJE) related functionality
1839 : : *
1840 : : * SJE needs to skip the RangeTblRef node type. During SJE's last
1841 : : * step, remove_rel_from_joinlist() removes remaining RangeTblRefs
1842 : : * with target relid. If ChangeVarNodes() replaces the target relid
1843 : : * before, remove_rel_from_joinlist() would fail to identify the nodes
1844 : : * to delete.
1845 : : *
1846 : : * SJE also needs to change the relids within RestrictInfo's.
1847 : : */
1848 : : static bool
419 1849 : 30676 : replace_relid_callback(Node *node, ChangeVarNodes_context *context)
1850 : : {
1851 [ + + ]: 30676 : if (IsA(node, RangeTblRef))
1852 : : {
1853 : 1249 : return true;
1854 : : }
1855 [ + + ]: 29427 : else if (IsA(node, RestrictInfo))
1856 : : {
1857 : 1463 : RestrictInfo *rinfo = (RestrictInfo *) node;
1858 : 1463 : int relid = -1;
1859 : 1463 : bool is_req_equal =
1860 : 1463 : (rinfo->required_relids == rinfo->clause_relids);
1861 : 1463 : bool clause_relids_is_multiple =
1862 : 1463 : (bms_membership(rinfo->clause_relids) == BMS_MULTIPLE);
1863 : :
1864 : : /*
1865 : : * Recurse down into clauses if the target relation is present in
1866 : : * clause_relids or required_relids. We must check required_relids
1867 : : * because the relation not present in clause_relids might still be
1868 : : * present somewhere in orclause.
1869 : : */
1870 [ + + + + ]: 1511 : if (bms_is_member(context->rt_index, rinfo->clause_relids) ||
1871 : 48 : bms_is_member(context->rt_index, rinfo->required_relids))
1872 : : {
1873 : : Relids new_clause_relids;
1874 : :
1875 : 1453 : ChangeVarNodesWalkExpression((Node *) rinfo->clause, context);
1876 : 1453 : ChangeVarNodesWalkExpression((Node *) rinfo->orclause, context);
1877 : :
1878 : 1453 : new_clause_relids = adjust_relid_set(rinfo->clause_relids,
1879 : : context->rt_index,
1880 : : context->new_index);
1881 : :
1882 : : /*
1883 : : * Incrementally adjust num_base_rels based on the change of
1884 : : * clause_relids, which could contain both base relids and
1885 : : * outer-join relids. This operation is legal until we remove
1886 : : * only baserels.
1887 : : */
1888 : 1453 : rinfo->num_base_rels -= bms_num_members(rinfo->clause_relids) -
1889 : 1453 : bms_num_members(new_clause_relids);
1890 : :
1891 : 1453 : rinfo->clause_relids = new_clause_relids;
1892 : 1453 : rinfo->left_relids =
1893 : 1453 : adjust_relid_set(rinfo->left_relids, context->rt_index, context->new_index);
1894 : 1453 : rinfo->right_relids =
1895 : 1453 : adjust_relid_set(rinfo->right_relids, context->rt_index, context->new_index);
1896 : : }
1897 : :
1898 [ + + ]: 1463 : if (is_req_equal)
1899 : 20 : rinfo->required_relids = rinfo->clause_relids;
1900 : : else
1901 : 1443 : rinfo->required_relids =
1902 : 1443 : adjust_relid_set(rinfo->required_relids, context->rt_index, context->new_index);
1903 : :
1904 : 1463 : rinfo->outer_relids =
1905 : 1463 : adjust_relid_set(rinfo->outer_relids, context->rt_index, context->new_index);
1906 : 1463 : rinfo->incompatible_relids =
1907 : 1463 : adjust_relid_set(rinfo->incompatible_relids, context->rt_index, context->new_index);
1908 : :
1909 [ + + + + ]: 2767 : if (rinfo->mergeopfamilies &&
1910 [ + + ]: 2490 : bms_get_singleton_member(rinfo->clause_relids, &relid) &&
1911 : 991 : clause_relids_is_multiple &&
1912 [ + - + - ]: 991 : relid == context->new_index && IsA(rinfo->clause, OpExpr))
1913 : : {
1914 : : Expr *leftOp;
1915 : : Expr *rightOp;
1916 : :
1917 : 991 : leftOp = (Expr *) get_leftop(rinfo->clause);
1918 : 991 : rightOp = (Expr *) get_rightop(rinfo->clause);
1919 : :
1920 : : /*
1921 : : * For self-join elimination, changing varnos could transform
1922 : : * "t1.a = t2.a" into "t1.a = t1.a". That is always true as long
1923 : : * as "t1.a" is not null. We use equal() to check for such a
1924 : : * case, and then we replace the qual with a check for not null
1925 : : * (NullTest).
1926 : : */
1927 [ + - + + ]: 991 : if (leftOp != NULL && equal(leftOp, rightOp))
1928 : : {
1929 : 981 : NullTest *ntest = makeNode(NullTest);
1930 : :
1931 : 981 : ntest->arg = leftOp;
1932 : 981 : ntest->nulltesttype = IS_NOT_NULL;
1933 : 981 : ntest->argisrow = false;
1934 : 981 : ntest->location = -1;
1935 : 981 : rinfo->clause = (Expr *) ntest;
1936 : 981 : rinfo->mergeopfamilies = NIL;
1937 : 981 : rinfo->left_em = NULL;
1938 : 981 : rinfo->right_em = NULL;
1939 : : }
1940 [ - + ]: 991 : Assert(rinfo->orclause == NULL);
1941 : : }
1942 : 1463 : return true;
1943 : : }
1944 : :
1945 : 27964 : return false;
1946 : : }
1947 : :
1948 : : /*
1949 : : * Remove a relation after we have proven that it participates only in an
1950 : : * unneeded unique self-join.
1951 : : *
1952 : : * Replace any links in planner info structures.
1953 : : *
1954 : : * Transfer join and restriction clauses from the removed relation to the
1955 : : * remaining one. We change the Vars of the clause to point to the
1956 : : * remaining relation instead of the removed one. The clauses that require
1957 : : * a subset of joinrelids become restriction clauses of the remaining
1958 : : * relation, and others remain join clauses. We append them to
1959 : : * baserestrictinfo and joininfo, respectively, trying not to introduce
1960 : : * duplicates.
1961 : : *
1962 : : * We also have to process the 'joinclauses' list here, because it
1963 : : * contains EC-derived join clauses which must become filter clauses. It
1964 : : * is not enough to just correct the ECs because the EC-derived
1965 : : * restrictions are generated before join removal (see
1966 : : * generate_base_implied_equalities).
1967 : : *
1968 : : * NOTE: Remember to keep the code in sync with PlannerInfo to be sure all
1969 : : * cached relids and relid bitmapsets can be correctly cleaned during the
1970 : : * self-join elimination procedure.
1971 : : */
1972 : : static void
502 1973 : 468 : remove_self_join_rel(PlannerInfo *root, PlanRowMark *kmark, PlanRowMark *rmark,
1974 : : RelOptInfo *toKeep, RelOptInfo *toRemove,
1975 : : List *restrictlist)
1976 : : {
1977 : : List *joininfos;
1978 : : ListCell *lc;
1979 : : int i;
1980 : 468 : List *jinfo_candidates = NIL;
1981 : 468 : List *binfo_candidates = NIL;
1982 : :
1983 [ - + ]: 468 : Assert(toKeep->relid > 0);
1984 [ - + ]: 468 : Assert(toRemove->relid > 0);
1985 : :
1986 : : /*
1987 : : * Replace the index of the removing table with the keeping one. The
1988 : : * technique of removing/distributing restrictinfo is used here to attach
1989 : : * just appeared (for keeping relation) join clauses and avoid adding
1990 : : * duplicates of those that already exist in the joininfo list.
1991 : : */
1992 : 468 : joininfos = list_copy(toRemove->joininfo);
1993 [ + + + + : 1019 : foreach_node(RestrictInfo, rinfo, joininfos)
+ + ]
1994 : : {
1995 : 83 : remove_join_clause_from_rels(root, rinfo, rinfo->required_relids);
419 1996 : 83 : ChangeVarNodesExtended((Node *) rinfo, toRemove->relid, toKeep->relid,
1997 : : 0, replace_relid_callback);
1998 : :
502 1999 [ + + ]: 83 : if (bms_membership(rinfo->required_relids) == BMS_MULTIPLE)
2000 : 68 : jinfo_candidates = lappend(jinfo_candidates, rinfo);
2001 : : else
2002 : 15 : binfo_candidates = lappend(binfo_candidates, rinfo);
2003 : : }
2004 : :
2005 : : /*
2006 : : * Concatenate restrictlist to the list of base restrictions of the
2007 : : * removing table just to simplify the replacement procedure: all of them
2008 : : * weren't connected to any keeping relations and need to be added to some
2009 : : * rels.
2010 : : */
2011 : 468 : toRemove->baserestrictinfo = list_concat(toRemove->baserestrictinfo,
2012 : : restrictlist);
2013 [ + - + + : 1633 : foreach_node(RestrictInfo, rinfo, toRemove->baserestrictinfo)
+ + ]
2014 : : {
419 2015 : 697 : ChangeVarNodesExtended((Node *) rinfo, toRemove->relid, toKeep->relid,
2016 : : 0, replace_relid_callback);
2017 : :
502 2018 [ - + ]: 697 : if (bms_membership(rinfo->required_relids) == BMS_MULTIPLE)
502 akorotkov@postgresql 2019 :UBC 0 : jinfo_candidates = lappend(jinfo_candidates, rinfo);
2020 : : else
502 akorotkov@postgresql 2021 :CBC 697 : binfo_candidates = lappend(binfo_candidates, rinfo);
2022 : : }
2023 : :
2024 : : /*
2025 : : * Now, add all non-redundant clauses to the keeping relation.
2026 : : */
2027 : 468 : add_non_redundant_clauses(root, binfo_candidates,
2028 : : &toKeep->baserestrictinfo, toRemove->relid);
2029 : 468 : add_non_redundant_clauses(root, jinfo_candidates,
2030 : : &toKeep->joininfo, toRemove->relid);
2031 : :
2032 : 468 : list_free(binfo_candidates);
2033 : 468 : list_free(jinfo_candidates);
2034 : :
2035 : : /*
2036 : : * Arrange equivalence classes, mentioned removing a table, with the
2037 : : * keeping one: varno of removing table should be replaced in members and
2038 : : * sources lists. Also, remove duplicated elements if this replacement
2039 : : * procedure created them.
2040 : : */
2041 : 468 : i = -1;
2042 [ + + ]: 1219 : while ((i = bms_next_member(toRemove->eclass_indexes, i)) >= 0)
2043 : : {
2044 : 751 : EquivalenceClass *ec = (EquivalenceClass *) list_nth(root->eq_classes, i);
2045 : :
2046 : 751 : update_eclasses(ec, toRemove->relid, toKeep->relid);
2047 : 751 : toKeep->eclass_indexes = bms_add_member(toKeep->eclass_indexes, i);
2048 : : }
2049 : :
2050 : : /*
2051 : : * Transfer the targetlist and attr_needed flags.
2052 : : */
2053 : :
2054 [ + - + + : 1704 : foreach(lc, toRemove->reltarget->exprs)
+ + ]
2055 : : {
2056 : 1236 : Node *node = lfirst(lc);
2057 : :
419 2058 : 1236 : ChangeVarNodesExtended(node, toRemove->relid, toKeep->relid, 0,
2059 : : replace_relid_callback);
502 2060 [ + + ]: 1236 : if (!list_member(toKeep->reltarget->exprs, node))
2061 : 128 : toKeep->reltarget->exprs = lappend(toKeep->reltarget->exprs, node);
2062 : : }
2063 : :
2064 [ + + ]: 5653 : for (i = toKeep->min_attr; i <= toKeep->max_attr; i++)
2065 : : {
2066 : 5185 : int attno = i - toKeep->min_attr;
2067 : :
2068 : 10370 : toRemove->attr_needed[attno] = adjust_relid_set(toRemove->attr_needed[attno],
2069 : 5185 : toRemove->relid, toKeep->relid);
2070 : 5185 : toKeep->attr_needed[attno] = bms_add_members(toKeep->attr_needed[attno],
2071 : 5185 : toRemove->attr_needed[attno]);
2072 : : }
2073 : :
2074 : : /*
2075 : : * If the removed relation has a row mark, transfer it to the remaining
2076 : : * one.
2077 : : *
2078 : : * If both rels have row marks, just keep the one corresponding to the
2079 : : * remaining relation because we verified earlier that they have the same
2080 : : * strength.
2081 : : */
2082 [ + + ]: 468 : if (rmark)
2083 : : {
2084 [ + - ]: 41 : if (kmark)
2085 : : {
2086 [ - + ]: 41 : Assert(kmark->markType == rmark->markType);
2087 : :
2088 : 41 : root->rowMarks = list_delete_ptr(root->rowMarks, rmark);
2089 : : }
2090 : : else
2091 : : {
2092 : : /* Shouldn't have inheritance children here. */
502 akorotkov@postgresql 2093 [ # # ]:UBC 0 : Assert(rmark->rti == rmark->prti);
2094 : :
2095 : 0 : rmark->rti = rmark->prti = toKeep->relid;
2096 : : }
2097 : : }
2098 : :
2099 : : /*
2100 : : * Replace varno in all the query structures, except nodes RangeTblRef
2101 : : * otherwise later remove_rel_from_joinlist will yield errors.
2102 : : */
419 akorotkov@postgresql 2103 :CBC 468 : ChangeVarNodesExtended((Node *) root->parse, toRemove->relid, toKeep->relid,
2104 : : 0, replace_relid_callback);
2105 : :
2106 : : /* Replace links in the planner info */
71 rguo@postgresql.org 2107 :GNC 468 : remove_rel_from_query(root, toRemove->relid, toKeep->relid, NULL, NULL);
2108 : :
2109 : : /* Replace varno in the fully-processed targetlist */
419 akorotkov@postgresql 2110 :CBC 468 : ChangeVarNodesExtended((Node *) root->processed_tlist, toRemove->relid,
2111 : 468 : toKeep->relid, 0, replace_relid_callback);
2112 : :
2113 : : /*
2114 : : * No need to touch all_result_relids or leaf_result_relids: at this point
2115 : : * those sets contain only parse->resultRelation; inheritance children
2116 : : * have not been added yet; that happens later in add_other_rels_to_query.
2117 : : * And remove_self_joins_recurse rejects parse->resultRelation as an SJE
2118 : : * candidate to preserve the EPQ mechanism. So toRemove->relid cannot be
2119 : : * a member.
2120 : : */
64 rguo@postgresql.org 2121 [ - + ]:GNC 468 : Assert(!bms_is_member(toRemove->relid, root->all_result_relids));
2122 [ - + ]: 468 : Assert(!bms_is_member(toRemove->relid, root->leaf_result_relids));
2123 : :
2124 : : /*
2125 : : * There may be references to the rel in root->fkey_list, but if so,
2126 : : * match_foreign_keys_to_quals() will get rid of them.
2127 : : */
2128 : :
2129 : : /*
2130 : : * Finally, remove the rel from the baserel array to prevent it from being
2131 : : * referenced again. (We can't do this earlier because
2132 : : * remove_join_clause_from_rels will touch it.)
2133 : : */
502 akorotkov@postgresql 2134 :CBC 468 : root->simple_rel_array[toRemove->relid] = NULL;
310 2135 : 468 : root->simple_rte_array[toRemove->relid] = NULL;
2136 : :
2137 : : /* And nuke the RelOptInfo, just in case there's another access path. */
502 2138 : 468 : pfree(toRemove);
2139 : :
2140 : :
2141 : : /*
2142 : : * Now repeat construction of attr_needed bits coming from all other
2143 : : * sources.
2144 : : */
2145 : 468 : rebuild_placeholder_attr_needed(root);
2146 : 468 : rebuild_joinclause_attr_needed(root);
2147 : 468 : rebuild_eclass_attr_needed(root);
2148 : 468 : rebuild_lateral_attr_needed(root);
2149 : 468 : }
2150 : :
2151 : : /*
2152 : : * split_selfjoin_quals
2153 : : * Processes 'joinquals' by building two lists: one containing the quals
2154 : : * where the columns/exprs are on either side of the join match and
2155 : : * another one containing the remaining quals.
2156 : : *
2157 : : * 'joinquals' must only contain quals for a RTE_RELATION being joined to
2158 : : * itself.
2159 : : */
2160 : : static void
2161 : 1791 : split_selfjoin_quals(PlannerInfo *root, List *joinquals, List **selfjoinquals,
2162 : : List **otherjoinquals, int from, int to)
2163 : : {
2164 : 1791 : List *sjoinquals = NIL;
2165 : 1791 : List *ojoinquals = NIL;
2166 : :
2167 [ + - + + : 5497 : foreach_node(RestrictInfo, rinfo, joinquals)
+ + ]
2168 : : {
2169 : : OpExpr *expr;
2170 : : Node *leftexpr;
2171 : : Node *rightexpr;
2172 : :
2173 : : /* In general, clause looks like F(arg1) = G(arg2) */
2174 [ + - + - ]: 3830 : if (!rinfo->mergeopfamilies ||
2175 [ + - ]: 3830 : bms_num_members(rinfo->clause_relids) != 2 ||
2176 [ - + ]: 3830 : bms_membership(rinfo->left_relids) != BMS_SINGLETON ||
2177 : 1915 : bms_membership(rinfo->right_relids) != BMS_SINGLETON)
2178 : : {
502 akorotkov@postgresql 2179 :UBC 0 : ojoinquals = lappend(ojoinquals, rinfo);
2180 : 0 : continue;
2181 : : }
2182 : :
502 akorotkov@postgresql 2183 :CBC 1915 : expr = (OpExpr *) rinfo->clause;
2184 : :
2185 [ + - - + ]: 1915 : if (!IsA(expr, OpExpr) || list_length(expr->args) != 2)
2186 : : {
502 akorotkov@postgresql 2187 :UBC 0 : ojoinquals = lappend(ojoinquals, rinfo);
2188 : 0 : continue;
2189 : : }
2190 : :
502 akorotkov@postgresql 2191 :CBC 1915 : leftexpr = get_leftop(rinfo->clause);
2192 : 1915 : rightexpr = copyObject(get_rightop(rinfo->clause));
2193 : :
2194 [ + - + + ]: 1915 : if (leftexpr && IsA(leftexpr, RelabelType))
2195 : 130 : leftexpr = (Node *) ((RelabelType *) leftexpr)->arg;
2196 [ + - + + ]: 1915 : if (rightexpr && IsA(rightexpr, RelabelType))
2197 : 125 : rightexpr = (Node *) ((RelabelType *) rightexpr)->arg;
2198 : :
2199 : : /*
2200 : : * Quite an expensive operation, narrowing the use case. For example,
2201 : : * when we have cast of the same var to different (but compatible)
2202 : : * types.
2203 : : */
419 2204 : 1915 : ChangeVarNodesExtended(rightexpr,
2205 : 1915 : bms_singleton_member(rinfo->right_relids),
2206 : 1915 : bms_singleton_member(rinfo->left_relids), 0,
2207 : : replace_relid_callback);
2208 : :
502 2209 [ + + ]: 1915 : if (equal(leftexpr, rightexpr))
2210 : 1492 : sjoinquals = lappend(sjoinquals, rinfo);
2211 : : else
2212 : 423 : ojoinquals = lappend(ojoinquals, rinfo);
2213 : : }
2214 : :
2215 : 1791 : *selfjoinquals = sjoinquals;
2216 : 1791 : *otherjoinquals = ojoinquals;
2217 : 1791 : }
2218 : :
2219 : : /*
2220 : : * Check for a case when uniqueness is at least partly derived from a
2221 : : * baserestrictinfo clause. In this case, we have a chance to return only
2222 : : * one row (if such clauses on both sides of SJ are equal) or nothing (if they
2223 : : * are different).
2224 : : */
2225 : : static bool
2226 : 523 : match_unique_clauses(PlannerInfo *root, RelOptInfo *outer, List *uclauses,
2227 : : Index relid)
2228 : : {
2229 [ + + + + : 1061 : foreach_node(RestrictInfo, rinfo, uclauses)
+ + ]
2230 : : {
2231 : : Expr *clause;
2232 : : Node *iclause;
2233 : : Node *c1;
2234 : 125 : bool matched = false;
2235 : :
2236 [ + - - + ]: 125 : Assert(outer->relid > 0 && relid > 0);
2237 : :
2238 : : /* Only filters like f(R.x1,...,R.xN) == expr we should consider. */
2239 [ - + ]: 125 : Assert(bms_is_empty(rinfo->left_relids) ^
2240 : : bms_is_empty(rinfo->right_relids));
2241 : :
2242 : 125 : clause = (Expr *) copyObject(rinfo->clause);
419 2243 : 125 : ChangeVarNodesExtended((Node *) clause, relid, outer->relid, 0,
2244 : : replace_relid_callback);
2245 : :
502 2246 [ + + ]: 125 : iclause = bms_is_empty(rinfo->left_relids) ? get_rightop(clause) :
2247 : 120 : get_leftop(clause);
2248 [ + + ]: 125 : c1 = bms_is_empty(rinfo->left_relids) ? get_leftop(clause) :
2249 : 120 : get_rightop(clause);
2250 : :
2251 : : /*
2252 : : * Compare these left and right sides with the corresponding sides of
2253 : : * the outer's filters. If no one is detected - return immediately.
2254 : : */
2255 [ + + + + : 340 : foreach_node(RestrictInfo, orinfo, outer->baserestrictinfo)
+ + ]
2256 : : {
2257 : : Node *oclause;
2258 : : Node *c2;
2259 : :
2260 [ + + ]: 160 : if (orinfo->mergeopfamilies == NIL)
2261 : : /* Don't consider clauses that aren't similar to 'F(X)=G(Y)' */
2262 : 50 : continue;
2263 : :
2264 [ - + ]: 110 : Assert(is_opclause(orinfo->clause));
2265 : :
2266 : 220 : oclause = bms_is_empty(orinfo->left_relids) ?
2267 [ + + ]: 110 : get_rightop(orinfo->clause) : get_leftop(orinfo->clause);
2268 : 220 : c2 = (bms_is_empty(orinfo->left_relids) ?
2269 [ + + ]: 110 : get_leftop(orinfo->clause) : get_rightop(orinfo->clause));
2270 : :
2271 [ + + + + ]: 110 : if (equal(iclause, oclause) && equal(c1, c2))
2272 : : {
2273 : 70 : matched = true;
2274 : 70 : break;
2275 : : }
2276 : : }
2277 : :
2278 [ + + ]: 125 : if (!matched)
2279 : 55 : return false;
2280 : : }
2281 : :
2282 : 468 : return true;
2283 : : }
2284 : :
2285 : : /*
2286 : : * Find and remove unique self-joins in a group of base relations that have
2287 : : * the same Oid.
2288 : : *
2289 : : * Returns a set of relids that were removed.
2290 : : */
2291 : : static Relids
2292 : 8705 : remove_self_joins_one_group(PlannerInfo *root, Relids relids)
2293 : : {
2294 : 8705 : Relids result = NULL;
2295 : : int k; /* Index of kept relation */
2296 : 8705 : int r = -1; /* Index of removed relation */
2297 : :
2298 [ + + ]: 27219 : while ((r = bms_next_member(relids, r)) > 0)
2299 : : {
308 2300 : 18514 : RelOptInfo *rrel = root->simple_rel_array[r];
2301 : :
502 2302 : 18514 : k = r;
2303 : :
2304 [ + + ]: 29180 : while ((k = bms_next_member(relids, k)) > 0)
2305 : : {
2306 : 11134 : Relids joinrelids = NULL;
308 2307 : 11134 : RelOptInfo *krel = root->simple_rel_array[k];
2308 : : List *restrictlist;
2309 : : List *selfjoinquals;
2310 : : List *otherjoinquals;
2311 : : ListCell *lc;
502 2312 : 11134 : bool jinfo_check = true;
308 2313 : 11134 : PlanRowMark *kmark = NULL;
2314 : 11134 : PlanRowMark *rmark = NULL;
502 2315 : 11134 : List *uclauses = NIL;
2316 : :
2317 : : /* A sanity check: the relations have the same Oid. */
2318 [ - + ]: 11134 : Assert(root->simple_rte_array[k]->relid ==
2319 : : root->simple_rte_array[r]->relid);
2320 : :
2321 : : /*
2322 : : * It is impossible to eliminate the join of two relations if they
2323 : : * belong to different rules of order. Otherwise, the planner
2324 : : * can't find any variants of the correct query plan.
2325 : : */
2326 [ + + + + : 13652 : foreach(lc, root->join_info_list)
+ + ]
2327 : : {
2328 : 8635 : SpecialJoinInfo *info = (SpecialJoinInfo *) lfirst(lc);
2329 : :
2330 [ + + ]: 17270 : if ((bms_is_member(k, info->syn_lefthand) ^
2331 [ + + ]: 12173 : bms_is_member(r, info->syn_lefthand)) ||
2332 : 3538 : (bms_is_member(k, info->syn_righthand) ^
2333 : 3538 : bms_is_member(r, info->syn_righthand)))
2334 : : {
2335 : 6117 : jinfo_check = false;
2336 : 6117 : break;
2337 : : }
2338 : : }
2339 [ + + ]: 11134 : if (!jinfo_check)
2340 : 10666 : continue;
2341 : :
2342 : : /*
2343 : : * Check Row Marks equivalence. We can't remove the join if the
2344 : : * relations have row marks of different strength (e.g., one is
2345 : : * locked FOR UPDATE, and another just has ROW_MARK_REFERENCE for
2346 : : * EvalPlanQual rechecking).
2347 : : */
2348 [ + + + - : 5153 : foreach(lc, root->rowMarks)
+ + ]
2349 : : {
2350 : 242 : PlanRowMark *rowMark = (PlanRowMark *) lfirst(lc);
2351 : :
310 2352 [ + + ]: 242 : if (rowMark->rti == r)
2353 : : {
308 2354 [ - + ]: 106 : Assert(rmark == NULL);
2355 : 106 : rmark = rowMark;
2356 : : }
310 2357 [ + + ]: 136 : else if (rowMark->rti == k)
2358 : : {
308 2359 [ - + ]: 106 : Assert(kmark == NULL);
2360 : 106 : kmark = rowMark;
2361 : : }
2362 : :
2363 [ + + + - ]: 242 : if (kmark && rmark)
502 2364 : 106 : break;
2365 : : }
308 2366 [ + + + - : 5017 : if (kmark && rmark && kmark->markType != rmark->markType)
+ + ]
502 2367 : 28 : continue;
2368 : :
2369 : : /*
2370 : : * We only deal with base rels here, so their relids bitset
2371 : : * contains only one member -- their relid.
2372 : : */
2373 : 4989 : joinrelids = bms_add_member(joinrelids, r);
2374 : 4989 : joinrelids = bms_add_member(joinrelids, k);
2375 : :
2376 : : /*
2377 : : * PHVs should not impose any constraints on removing self-joins.
2378 : : */
2379 : :
2380 : : /*
2381 : : * At this stage, joininfo lists of inner and outer can contain
2382 : : * only clauses required for a superior outer join that can't
2383 : : * influence this optimization. So, we can avoid to call the
2384 : : * build_joinrel_restrictlist() routine.
2385 : : */
2386 : 4989 : restrictlist = generate_join_implied_equalities(root, joinrelids,
2387 : : rrel->relids,
2388 : : krel, NULL);
2389 [ + + ]: 4989 : if (restrictlist == NIL)
2390 : 3198 : continue;
2391 : :
2392 : : /*
2393 : : * Process restrictlist to separate the self-join quals from the
2394 : : * other quals. e.g., "x = x" goes to selfjoinquals and "a = b" to
2395 : : * otherjoinquals.
2396 : : */
2397 : 1791 : split_selfjoin_quals(root, restrictlist, &selfjoinquals,
308 2398 : 1791 : &otherjoinquals, rrel->relid, krel->relid);
2399 : :
502 2400 [ - + ]: 1791 : Assert(list_length(restrictlist) ==
2401 : : (list_length(selfjoinquals) + list_length(otherjoinquals)));
2402 : :
2403 : : /*
2404 : : * To enable SJE for the only degenerate case without any self
2405 : : * join clauses at all, add baserestrictinfo to this list. The
2406 : : * degenerate case works only if both sides have the same clause.
2407 : : * So doesn't matter which side to add.
2408 : : */
308 2409 : 1791 : selfjoinquals = list_concat(selfjoinquals, krel->baserestrictinfo);
2410 : :
2411 : : /*
2412 : : * Determine if the rrel can duplicate outer rows. We must bypass
2413 : : * the unique rel cache here since we're possibly using a subset
2414 : : * of join quals. We can use 'force_cache' == true when all join
2415 : : * quals are self-join quals. Otherwise, we could end up putting
2416 : : * false negatives in the cache.
2417 : : */
2418 [ + + ]: 1791 : if (!innerrel_is_unique_ext(root, joinrelids, rrel->relids,
2419 : : krel, JOIN_INNER, selfjoinquals,
502 2420 : 1791 : list_length(otherjoinquals) == 0,
2421 : : &uclauses))
2422 : 1268 : continue;
2423 : :
2424 : : /*
2425 : : * 'uclauses' is the copy of outer->baserestrictinfo that are
2426 : : * associated with an index. We proved by matching selfjoinquals
2427 : : * to a unique index that the outer relation has at most one
2428 : : * matching row for each inner row. Sometimes that is not enough.
2429 : : * e.g. "WHERE s1.b = s2.b AND s1.a = 1 AND s2.a = 2" when the
2430 : : * unique index is (a,b). Having non-empty uclauses, we must
2431 : : * validate that the inner baserestrictinfo contains the same
2432 : : * expressions, or we won't match the same row on each side of the
2433 : : * join.
2434 : : */
308 2435 [ + + ]: 523 : if (!match_unique_clauses(root, rrel, uclauses, krel->relid))
502 2436 : 55 : continue;
2437 : :
2438 : : /*
2439 : : * Remove rrel RelOptInfo from the planner structures and the
2440 : : * corresponding row mark.
2441 : : */
308 2442 : 468 : remove_self_join_rel(root, kmark, rmark, krel, rrel, restrictlist);
2443 : :
502 2444 : 468 : result = bms_add_member(result, r);
2445 : :
2446 : : /* We have removed the outer relation, try the next one. */
2447 : 468 : break;
2448 : : }
2449 : : }
2450 : :
2451 : 8705 : return result;
2452 : : }
2453 : :
2454 : : /*
2455 : : * Gather indexes of base relations from the joinlist and try to eliminate self
2456 : : * joins.
2457 : : */
2458 : : static Relids
2459 : 81542 : remove_self_joins_recurse(PlannerInfo *root, List *joinlist, Relids toRemove)
2460 : : {
2461 : : ListCell *jl;
2462 : 81542 : Relids relids = NULL;
2463 : 81542 : SelfJoinCandidate *candidates = NULL;
2464 : : int i;
2465 : : int j;
2466 : : int numRels;
2467 : :
2468 : : /* Collect indexes of base relations of the join tree */
2469 [ + - + + : 271256 : foreach(jl, joinlist)
+ + ]
2470 : : {
2471 : 189714 : Node *jlnode = (Node *) lfirst(jl);
2472 : :
2473 [ + + ]: 189714 : if (IsA(jlnode, RangeTblRef))
2474 : : {
2475 : 186996 : int varno = ((RangeTblRef *) jlnode)->rtindex;
2476 : 186996 : RangeTblEntry *rte = root->simple_rte_array[varno];
2477 : :
2478 : : /*
2479 : : * We only consider ordinary relations as candidates to be
2480 : : * removed, and these relations should not have TABLESAMPLE
2481 : : * clauses specified. Removing a relation with TABLESAMPLE clause
2482 : : * could potentially change the syntax of the query. Because of
2483 : : * UPDATE/DELETE EPQ mechanism, currently Query->resultRelation or
2484 : : * Query->mergeTargetRelation associated rel cannot be eliminated.
2485 : : */
2486 [ + + ]: 186996 : if (rte->rtekind == RTE_RELATION &&
2487 [ + + ]: 165946 : rte->relkind == RELKIND_RELATION &&
2488 [ + + ]: 161408 : rte->tablesample == NULL &&
2489 [ + + ]: 161386 : varno != root->parse->resultRelation &&
2490 [ + - ]: 159863 : varno != root->parse->mergeTargetRelation)
2491 : : {
2492 [ - + ]: 159863 : Assert(!bms_is_member(varno, relids));
2493 : 159863 : relids = bms_add_member(relids, varno);
2494 : : }
2495 : : }
2496 [ + - ]: 2718 : else if (IsA(jlnode, List))
2497 : : {
2498 : : /* Recursively go inside the sub-joinlist */
2499 : 2718 : toRemove = remove_self_joins_recurse(root, (List *) jlnode,
2500 : : toRemove);
2501 : : }
2502 : : else
502 akorotkov@postgresql 2503 [ # # ]:UBC 0 : elog(ERROR, "unrecognized joinlist node type: %d",
2504 : : (int) nodeTag(jlnode));
2505 : : }
2506 : :
502 akorotkov@postgresql 2507 :CBC 81542 : numRels = bms_num_members(relids);
2508 : :
2509 : : /* Need at least two relations for the join */
2510 [ + + ]: 81542 : if (numRels < 2)
2511 : 22037 : return toRemove;
2512 : :
2513 : : /*
2514 : : * In order to find relations with the same oid we first build an array of
2515 : : * candidates and then sort it by oid.
2516 : : */
202 michael@paquier.xyz 2517 :GNC 59505 : candidates = palloc_array(SelfJoinCandidate, numRels);
502 akorotkov@postgresql 2518 :CBC 59505 : i = -1;
2519 : 59505 : j = 0;
2520 [ + + ]: 203688 : while ((i = bms_next_member(relids, i)) >= 0)
2521 : : {
2522 : 144183 : candidates[j].relid = i;
2523 : 144183 : candidates[j].reloid = root->simple_rte_array[i]->relid;
2524 : 144183 : j++;
2525 : : }
2526 : :
2527 : 59505 : qsort(candidates, numRels, sizeof(SelfJoinCandidate),
2528 : : self_join_candidates_cmp);
2529 : :
2530 : : /*
2531 : : * Iteratively form a group of relation indexes with the same oid and
2532 : : * launch the routine that detects self-joins in this group and removes
2533 : : * excessive range table entries.
2534 : : *
2535 : : * At the end of the iteration, exclude the group from the overall relids
2536 : : * list. So each next iteration of the cycle will involve less and less
2537 : : * value of relids.
2538 : : */
2539 : 59505 : i = 0;
2540 [ + + ]: 203688 : for (j = 1; j < numRels + 1; j++)
2541 : : {
2542 [ + + + + ]: 144183 : if (j == numRels || candidates[j].reloid != candidates[i].reloid)
2543 : : {
2544 [ + + ]: 134454 : if (j - i >= 2)
2545 : : {
2546 : : /* Create a group of relation indexes with the same oid */
2547 : 8635 : Relids group = NULL;
2548 : : Relids removed;
2549 : :
2550 [ + + ]: 26999 : while (i < j)
2551 : : {
2552 : 18364 : group = bms_add_member(group, candidates[i].relid);
2553 : 18364 : i++;
2554 : : }
2555 : 8635 : relids = bms_del_members(relids, group);
2556 : :
2557 : : /*
2558 : : * Try to remove self-joins from a group of identical entries.
2559 : : * Make the next attempt iteratively - if something is deleted
2560 : : * from a group, changes in clauses and equivalence classes
2561 : : * can give us a chance to find more candidates.
2562 : : */
2563 : : do
2564 : : {
2565 [ - + ]: 8705 : Assert(!bms_overlap(group, toRemove));
2566 : 8705 : removed = remove_self_joins_one_group(root, group);
2567 : 8705 : toRemove = bms_add_members(toRemove, removed);
2568 : 8705 : group = bms_del_members(group, removed);
2569 [ + + + + ]: 9153 : } while (!bms_is_empty(removed) &&
2570 : 448 : bms_membership(group) == BMS_MULTIPLE);
2571 : 8635 : bms_free(removed);
2572 : 8635 : bms_free(group);
2573 : : }
2574 : : else
2575 : : {
2576 : : /* Single relation, just remove it from the set */
2577 : 125819 : relids = bms_del_member(relids, candidates[i].relid);
2578 : 125819 : i = j;
2579 : : }
2580 : : }
2581 : : }
2582 : :
2583 [ - + ]: 59505 : Assert(bms_is_empty(relids));
2584 : :
2585 : 59505 : return toRemove;
2586 : : }
2587 : :
2588 : : /*
2589 : : * Compare self-join candidates by their oids.
2590 : : */
2591 : : static int
2592 : 105409 : self_join_candidates_cmp(const void *a, const void *b)
2593 : : {
2594 : 105409 : const SelfJoinCandidate *ca = (const SelfJoinCandidate *) a;
2595 : 105409 : const SelfJoinCandidate *cb = (const SelfJoinCandidate *) b;
2596 : :
2597 [ + + ]: 105409 : if (ca->reloid != cb->reloid)
2598 [ + + ]: 95635 : return (ca->reloid < cb->reloid ? -1 : 1);
2599 : : else
2600 : 9774 : return 0;
2601 : : }
2602 : :
2603 : : /*
2604 : : * Find and remove useless self joins.
2605 : : *
2606 : : * Search for joins where a relation is joined to itself. If the join clause
2607 : : * for each tuple from one side of the join is proven to match the same
2608 : : * physical row (or nothing) on the other side, that self-join can be
2609 : : * eliminated from the query. Suitable join clauses are assumed to be in the
2610 : : * form of X = X, and can be replaced with NOT NULL clauses.
2611 : : *
2612 : : * For the sake of simplicity, we don't apply this optimization to special
2613 : : * joins. Here is a list of what we could do in some particular cases:
2614 : : * 'a a1 semi join a a2': is reduced to inner by reduce_unique_semijoins,
2615 : : * and then removed normally.
2616 : : * 'a a1 anti join a a2': could simplify to a scan with 'outer quals AND
2617 : : * (IS NULL on join columns OR NOT inner quals)'.
2618 : : * 'a a1 left join a a2': could simplify to a scan like inner but without
2619 : : * NOT NULL conditions on join columns.
2620 : : * 'a a1 left join (a a2 join b)': can't simplify this, because join to b
2621 : : * can both remove rows and introduce duplicates.
2622 : : *
2623 : : * To search for removable joins, we order all the relations on their Oid,
2624 : : * go over each set with the same Oid, and consider each pair of relations
2625 : : * in this set.
2626 : : *
2627 : : * To remove the join, we mark one of the participating relations as dead
2628 : : * and rewrite all references to it to point to the remaining relation.
2629 : : * This includes modifying RestrictInfos, EquivalenceClasses, and
2630 : : * EquivalenceMembers. We also have to modify the row marks. The join clauses
2631 : : * of the removed relation become either restriction or join clauses, based on
2632 : : * whether they reference any relations not participating in the removed join.
2633 : : *
2634 : : * 'joinlist' is the top-level joinlist of the query. If it has any
2635 : : * references to the removed relations, we update them to point to the
2636 : : * remaining ones.
2637 : : */
2638 : : List *
2639 : 246771 : remove_useless_self_joins(PlannerInfo *root, List *joinlist)
2640 : : {
2641 : 246771 : Relids toRemove = NULL;
2642 : 246771 : int relid = -1;
2643 : :
2644 [ + - + - : 493542 : if (!enable_self_join_elimination || joinlist == NIL ||
+ + ]
2645 [ + + ]: 415416 : (list_length(joinlist) == 1 && !IsA(linitial(joinlist), List)))
2646 : 167947 : return joinlist;
2647 : :
2648 : : /*
2649 : : * Merge pairs of relations participated in self-join. Remove unnecessary
2650 : : * range table entries.
2651 : : */
2652 : 78824 : toRemove = remove_self_joins_recurse(root, joinlist, toRemove);
2653 : :
2654 [ + + ]: 78824 : if (unlikely(toRemove != NULL))
2655 : : {
2656 : : /* At the end, remove orphaned relation links */
2657 [ + + ]: 911 : while ((relid = bms_next_member(toRemove, relid)) >= 0)
2658 : : {
2659 : 468 : int nremoved = 0;
2660 : :
2661 : 468 : joinlist = remove_rel_from_joinlist(joinlist, relid, &nremoved);
2662 [ - + ]: 468 : if (nremoved != 1)
502 akorotkov@postgresql 2663 [ # # ]:UBC 0 : elog(ERROR, "failed to find relation %d in joinlist", relid);
2664 : : }
2665 : : }
2666 : :
502 akorotkov@postgresql 2667 :CBC 78824 : return joinlist;
2668 : : }
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