1/*-------------------------------------------------------------------------
4 * Routines to determine which relations should be joined
6 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
7 * Portions Copyright (c) 1994, Regents of the University of California
11 * src/backend/optimizer/path/joinrels.c
13 *-------------------------------------------------------------------------
38 bool only_pushed_down);
45 List *parent_restrictlist);
61 * join_search_one_level
62 * Consider ways to produce join relations containing exactly 'level'
63 * jointree items. (This is one step of the dynamic-programming method
64 * embodied in standard_join_search.) Join rel nodes for each feasible
65 * combination of lower-level rels are created and returned in a list.
66 * Implementation paths are created for each such joinrel, too.
68 * level: level of rels we want to make this time
69 * root->join_rel_level[j], 1 <= j < level, is a list of rels containing j items
71 * The result is returned in root->join_rel_level[level].
76 List **joinrels =
root->join_rel_level;
82 /* Set join_cur_level so that new joinrels are added to proper list */
83 root->join_cur_level = level;
86 * First, consider left-sided and right-sided plans, in which rels of
87 * exactly level-1 member relations are joined against initial relations.
88 * We prefer to join using join clauses, but if we find a rel of level-1
89 * members that has no join clauses, we will generate Cartesian-product
90 * joins against all initial rels not already contained in it.
92 foreach(r, joinrels[level - 1])
102 * There are join clauses or join order restrictions relevant to
103 * this rel, so consider joins between this rel and (only) those
104 * initial rels it is linked to by a clause or restriction.
106 * At level 2 this condition is symmetric, so there is no need to
107 * look at initial rels before this one in the list; we already
108 * considered such joins when we were at the earlier rel. (The
109 * mirror-image joins are handled automatically by make_join_rel.)
110 * In later passes (level > 2), we join rels of the previous level
111 * to each initial rel they don't already include but have a join
112 * clause or restriction with.
114 if (level == 2)
/* consider remaining initial rels */
124 * Oops, we have a relation that is not joined to any other
125 * relation, either directly or by join-order restrictions.
126 * Cartesian product time.
128 * We consider a cartesian product with each not-already-included
129 * initial rel, whether it has other join clauses or not. At
130 * level 2, if there are two or more clauseless initial rels, we
131 * will redundantly consider joining them in both directions; but
132 * such cases aren't common enough to justify adding complexity to
133 * avoid the duplicated effort.
142 * Now, consider "bushy plans" in which relations of k initial rels are
143 * joined to relations of level-k initial rels, for 2 <= k <= level-2.
145 * We only consider bushy-plan joins for pairs of rels where there is a
146 * suitable join clause (or join order restriction), in order to avoid
147 * unreasonable growth of planning time.
151 int other_level = level - k;
154 * Since make_join_rel(x, y) handles both x,y and y,x cases, we only
155 * need to go as far as the halfway point.
160 foreach(r, joinrels[k])
167 * We can ignore relations without join clauses here, unless they
168 * participate in join-order restrictions --- then we might have
169 * to force a bushy join plan.
175 if (k == other_level)
/* only consider remaining rels */
187 * OK, we can build a rel of the right level from this
188 * pair of rels. Do so if there is at least one relevant
189 * join clause or join order restriction.
202 * Last-ditch effort: if we failed to find any usable joins so far, force
203 * a set of cartesian-product joins to be generated. This handles the
204 * special case where all the available rels have join clauses but we
205 * cannot use any of those clauses yet. This can only happen when we are
206 * considering a join sub-problem (a sub-joinlist) and all the rels in the
207 * sub-problem have only join clauses with rels outside the sub-problem.
210 * SELECT ... FROM a INNER JOIN b ON TRUE, c, d, ...
211 * WHERE a.w = c.x and b.y = d.z;
213 * If the "a INNER JOIN b" sub-problem does not get flattened into the
214 * upper level, we must be willing to make a cartesian join of a and b;
215 * but the code above will not have done so, because it thought that both
216 * a and b have joinclauses. We consider only left-sided and right-sided
217 * cartesian joins in this case (no bushy).
220 if (joinrels[level] ==
NIL)
223 * This loop is just like the first one, except we always call
224 * make_rels_by_clauseless_joins().
226 foreach(r, joinrels[level - 1])
236 * When special joins are involved, there may be no legal way
237 * to make an N-way join for some values of N. For example consider
239 * SELECT ... FROM t1 WHERE
240 * x IN (SELECT ... FROM t2,t3 WHERE ...) AND
241 * y IN (SELECT ... FROM t4,t5 WHERE ...)
243 * We will flatten this query to a 5-way join problem, but there are
244 * no 4-way joins that join_is_legal() will consider legal. We have
245 * to accept failure at level 4 and go on to discover a workable
246 * bushy plan at level 5.
248 * However, if there are no special joins and no lateral references
249 * then join_is_legal() should never fail, and so the following sanity
253 if (joinrels[level] ==
NIL &&
255 !
root->hasLateralRTEs)
256 elog(
ERROR,
"failed to build any %d-way joins", level);
261 * make_rels_by_clause_joins
262 * Build joins between the given relation 'old_rel' and other relations
263 * that participate in join clauses that 'old_rel' also participates in
264 * (or participate in join-order restrictions with it).
265 * The join rels are returned in root->join_rel_level[join_cur_level].
267 * Note: at levels above 2 we will generate the same joined relation in
268 * multiple ways --- for example (a join b) join c is the same RelOptInfo as
269 * (b join c) join a, though the second case will add a different set of Paths
270 * to it. This is the reason for using the join_rel_level mechanism, which
271 * automatically ensures that each new joinrel is only added to the list once.
273 * 'old_rel' is the relation entry for the relation to be joined
274 * 'other_rels': a list containing the other rels to be considered for joining
275 * 'first_rel_idx': the first rel to be considered in 'other_rels'
277 * Currently, this is only used with initial rels in other_rels, but it
278 * will work for joining to joinrels too.
302 * make_rels_by_clauseless_joins
303 * Given a relation 'old_rel' and a list of other relations
304 * 'other_rels', create a join relation between 'old_rel' and each
305 * member of 'other_rels' that isn't already included in 'old_rel'.
306 * The join rels are returned in root->join_rel_level[join_cur_level].
308 * 'old_rel' is the relation entry for the relation to be joined
309 * 'other_rels': a list containing the other rels to be considered for joining
311 * Currently, this is only used with initial rels in other_rels, but it would
312 * work for joining to joinrels too.
321 foreach(l, other_rels)
335 * Determine whether a proposed join is legal given the query's
336 * join order constraints; and if it is, determine the join type.
338 * Caller must supply not only the two rels, but the union of their relids.
339 * (We could simplify the API by computing joinrelids locally, but this
340 * would be redundant work in the normal path through make_join_rel.
341 * Note that this value does NOT include the RT index of any outer join that
342 * might need to be performed here, so it's not the canonical identifier
343 * of the join relation.)
345 * On success, *sjinfo_p is set to NULL if this is to be a plain inner join,
346 * else it's set to point to the associated SpecialJoinInfo node. Also,
347 * *reversed_p is set true if the given relations need to be swapped to
348 * match the SpecialJoinInfo node.
358 bool must_be_leftjoin;
362 * Ensure output params are set on failure return. This is just to
363 * suppress uninitialized-variable warnings from overly anal compilers.
369 * If we have any special joins, the proposed join might be illegal; and
370 * in any case we have to determine its join type. Scan the join info
371 * list for matches and conflicts.
375 unique_ified =
false;
376 must_be_leftjoin =
false;
378 foreach(l,
root->join_info_list)
383 * This special join is not relevant unless its RHS overlaps the
384 * proposed join. (Check this first as a fast path for dismissing
385 * most irrelevant SJs quickly.)
391 * Also, not relevant if proposed join is fully contained within RHS
392 * (ie, we're still building up the RHS).
398 * Also, not relevant if SJ is already done within either input.
408 * If it's a semijoin and we already joined the RHS to any other rels
409 * within either input, then we must have unique-ified the RHS at that
410 * point (see below). Therefore the semijoin is no longer relevant in
424 * If one input contains min_lefthand and the other contains
425 * min_righthand, then we can perform the SJ at this join.
427 * Reject if we get matches to more than one SJ; that implies we're
428 * considering something that's not really valid.
434 return false;
/* invalid join path */
435 match_sjinfo = sjinfo;
442 return false;
/* invalid join path */
443 match_sjinfo = sjinfo;
451 * For a semijoin, we can join the RHS to anything else by
452 * unique-ifying the RHS (if the RHS can be unique-ified).
453 * We will only get here if we have the full RHS but less
454 * than min_lefthand on the LHS.
456 * The reason to consider such a join path is exemplified by
457 * SELECT ... FROM a,b WHERE (a.x,b.y) IN (SELECT c1,c2 FROM c)
458 * If we insist on doing this as a semijoin we will first have
459 * to form the cartesian product of A*B. But if we unique-ify
460 * C then the semijoin becomes a plain innerjoin and we can join
461 * in any order, eg C to A and then to B. When C is much smaller
462 * than A and B this can be a huge win. So we allow C to be
463 * joined to just A or just B here, and then make_join_rel has
464 * to handle the case properly.
466 * Note that actually we'll allow unique-ified C to be joined to
467 * some other relation D here, too. That is legal, if usually not
468 * very sane, and this routine is only concerned with legality not
469 * with whether the join is good strategy.
473 return false;
/* invalid join path */
474 match_sjinfo = sjinfo;
482 /* Reversed semijoin case */
484 return false;
/* invalid join path */
485 match_sjinfo = sjinfo;
492 * Otherwise, the proposed join overlaps the RHS but isn't a valid
493 * implementation of this SJ. But don't panic quite yet: the RHS
494 * violation might have occurred previously, in one or both input
495 * relations, in which case we must have previously decided that
496 * it was OK to commute some other SJ with this one. If we need
497 * to perform this join to finish building up the RHS, rejecting
498 * it could lead to not finding any plan at all. (This can occur
499 * because of the heuristics elsewhere in this file that postpone
500 * clauseless joins: we might not consider doing a clauseless join
501 * within the RHS until after we've performed other, validly
502 * commutable SJs with one or both sides of the clauseless join.)
503 * This consideration boils down to the rule that if both inputs
504 * overlap the RHS, we can allow the join --- they are either
505 * fully within the RHS, or represent previously-allowed joins to
510 continue;
/* assume valid previous violation of RHS */
513 * The proposed join could still be legal, but only if we're
514 * allowed to associate it into the RHS of this SJ. That means
515 * this SJ must be a LEFT join (not SEMI or ANTI, and certainly
516 * not FULL) and the proposed join must not overlap the LHS.
520 return false;
/* invalid join path */
523 * To be valid, the proposed join must be a LEFT join; otherwise
524 * it can't associate into this SJ's RHS. But we may not yet have
525 * found the SpecialJoinInfo matching the proposed join, so we
526 * can't test that yet. Remember the requirement for later.
528 must_be_leftjoin =
true;
533 * Fail if violated any SJ's RHS and didn't match to a LEFT SJ: the
534 * proposed join can't associate into an SJ's RHS.
536 * Also, fail if the proposed join's predicate isn't strict; we're
537 * essentially checking to see if we can apply outer-join identity 3, and
538 * that's a requirement. (This check may be redundant with checks in
539 * make_outerjoininfo, but I'm not quite sure, and it's cheap to test.)
541 if (must_be_leftjoin &&
542 (match_sjinfo == NULL ||
545 return false;
/* invalid join path */
548 * We also have to check for constraints imposed by LATERAL references.
550 if (
root->hasLateralRTEs)
557 * The proposed rels could each contain lateral references to the
558 * other, in which case the join is impossible. If there are lateral
559 * references in just one direction, then the join has to be done with
560 * a nestloop with the lateral referencer on the inside. If the join
561 * matches an SJ that cannot be implemented by such a nestloop, the
562 * join is impossible.
564 * Also, if the lateral reference is only indirect, we should reject
565 * the join; whatever rel(s) the reference chain goes through must be
570 if (lateral_fwd && lateral_rev)
571 return false;
/* have lateral refs in both directions */
574 /* has to be implemented as nestloop with rel1 on left */
579 return false;
/* not implementable as nestloop */
580 /* check there is a direct reference from rel2 to rel1 */
582 return false;
/* only indirect refs, so reject */
584 else if (lateral_rev)
586 /* has to be implemented as nestloop with rel2 on left */
591 return false;
/* not implementable as nestloop */
592 /* check there is a direct reference from rel1 to rel2 */
594 return false;
/* only indirect refs, so reject */
598 * LATERAL references could also cause problems later on if we accept
599 * this join: if the join's minimum parameterization includes any rels
600 * that would have to be on the inside of an outer join with this join
601 * rel, then it's never going to be possible to build the complete
602 * query using this join. We should reject this join not only because
603 * it'll save work, but because if we don't, the clauseless-join
604 * heuristics might think that legality of this join means that some
605 * other join rel need not be formed, and that could lead to failure
606 * to find any plan at all. We have to consider not only rels that
607 * are directly on the inner side of an OJ with the joinrel, but also
608 * ones that are indirectly so, so search to find all such rels.
612 if (join_lateral_rels)
620 foreach(l,
root->join_info_list)
624 /* ignore full joins --- their ordering is predetermined */
638 return false;
/* will not be able to join to some RHS rel */
642 /* Otherwise, it's a valid join */
643 *sjinfo_p = match_sjinfo;
644 *reversed_p = reversed;
650 * Populate the given SpecialJoinInfo for a plain inner join between the
651 * left and right relations specified by left_relids and right_relids
654 * Normally, an inner join does not have a SpecialJoinInfo node associated with
655 * it. But some functions involved in join planning require one containing at
656 * least the information of which relations are being joined. So we initialize
657 * that information here.
663 sjinfo->type = T_SpecialJoinInfo;
674 /* we don't bother trying to make the remaining fields valid */
684 * Find or create a join RelOptInfo that represents the join of
685 * the two given rels, and add to it path information for paths
686 * created with the two rels as outer and inner rel.
687 * (The join rel may already contain paths generated from other
688 * pairs of rels that add up to the same set of base rels.)
690 * NB: will return NULL if attempted join is not valid. This can happen
691 * when working with outer joins, or with IN or EXISTS clauses that have been
705 /* We should never try to join two overlapping sets of rels. */
708 /* Construct Relids set that identifies the joinrel (without OJ as yet). */
711 /* Check validity and determine join type. */
715 /* invalid join path */
721 * Add outer join relid(s) to form the canonical relids. Any added outer
722 * joins besides sjinfo itself are appended to pushed_down_joins.
727 /* Swap rels if needed to match the join info. */
737 * If it's a plain inner join, then we won't have found anything in
738 * join_info_list. Make up a SpecialJoinInfo so that selectivity
739 * estimation functions will know what's being joined.
743 sjinfo = &sjinfo_data;
748 * Find or build the join RelOptInfo, and compute the restrictlist that
749 * goes with this particular joining.
752 sjinfo, pushed_down_joins,
756 * If we've already proven this join is empty, we needn't consider any
765 /* Add paths to the join relation. */
775 * add_outer_joins_to_relids
776 * Add relids to input_relids to represent any outer joins that will be
777 * calculated at this join.
779 * input_relids is the union of the relid sets of the two input relations.
780 * Note that we modify this in-place and return it; caller must bms_copy()
781 * it first, if a separate value is desired.
783 * sjinfo represents the join being performed.
785 * If the current join completes the calculation of any outer joins that
786 * have been pushed down per outer-join identity 3, those relids will be
787 * added to the result along with sjinfo's own relid. If pushed_down_joins
788 * is not NULL, then also the SpecialJoinInfos for such added outer joins will
789 * be appended to *pushed_down_joins (so caller must initialize it to NIL).
794 List **pushed_down_joins)
796 /* Nothing to do if this isn't an outer join with an assigned relid. */
797 if (sjinfo == NULL || sjinfo->
ojrelid == 0)
801 * If it's not a left join, we have no rules that would permit executing
802 * it in non-syntactic order, so just form the syntactic relid set. (This
803 * is just a quick-exit test; we'd come to the same conclusion anyway,
804 * since its commute_below_l and commute_above_l sets must be empty.)
810 * We cannot add the OJ relid if this join has been pushed into the RHS of
811 * a syntactically-lower left join per OJ identity 3. (If it has, then we
812 * cannot claim that its outputs represent the final state of its RHS.)
813 * There will not be any other OJs that can be added either, so we're
819 /* OK to add OJ's own relid */
823 * Contrariwise, if we are now forming the final result of such a commuted
824 * pair of OJs, it's time to add the relid(s) of the pushed-down join(s).
825 * We can skip this if this join was never a candidate to be pushed up.
833 * The current join could complete the nulling of more than one
834 * pushed-down join, so we have to examine all the SpecialJoinInfos.
835 * Because join_info_list was built in bottom-up order, it's
836 * sufficient to traverse it once: an ojrelid we add in one loop
837 * iteration would not have affected decisions of earlier iterations.
839 foreach(lc,
root->join_info_list)
843 if (othersj == sjinfo ||
845 continue;
/* definitely not interesting */
850 /* Add it if not already present but conditions now satisfied */
857 /* report such pushed down outer joins, if asked */
858 if (pushed_down_joins != NULL)
859 *pushed_down_joins =
lappend(*pushed_down_joins, othersj);
862 * We must also check any joins that othersj potentially
863 * commutes with. They likewise must appear later in
864 * join_info_list than othersj itself, so we can visit them
865 * later in this loop.
877 * populate_joinrel_with_paths
878 * Add paths to the given joinrel for given pair of joining relations. The
879 * SpecialJoinInfo provides details about the join and the restrictlist
880 * contains the join clauses and the other clauses applicable for given pair
881 * of the joining relations.
891 * Consider paths using each rel as both outer and inner. Depending on
892 * the join type, a provably empty outer or inner rel might mean the join
893 * is provably empty too; in which case throw away any previously computed
894 * paths and mark the join as dummy. (We do it this way since it's
895 * conceivable that dummy-ness of a multi-element join might only be
896 * noticeable for certain construction paths.)
898 * Also, a provably constant-false join restriction typically means that
899 * we can skip evaluating one or both sides of the join. We do this by
900 * marking the appropriate rel as dummy. For outer joins, a
901 * constant-false restriction that is pushed down still means the whole
902 * join is dummy, while a non-pushed-down one means that no inner rows
903 * will join so we can treat the inner rel as dummy.
905 * We need only consider the jointypes that appear in join_info_list, plus
956 * If there are join quals that aren't mergeable or hashable, we
957 * may not be able to build any valid plan. Complain here so that
958 * we can give a somewhat-useful error message. (Since we have no
959 * flexibility of planning for a full join, there's no chance of
960 * succeeding later with another pair of input rels.)
964 (
errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
965 errmsg(
"FULL JOIN is only supported with merge-joinable or hash-joinable join conditions")));
970 * We might have a normal semijoin, or a case where we don't have
971 * enough rels to do the semijoin but can unique-ify the RHS and
972 * then do an innerjoin (see comments in join_is_legal). In the
973 * latter case we can't apply JOIN_SEMI joining.
993 * If we know how to unique-ify the RHS and one input rel is
994 * exactly the RHS (not a superset) we can consider unique-ifying
995 * it and then doing a regular join. (The create_unique_paths
996 * check here is probably redundant with what join_is_legal did,
997 * but if so the check is cheap because it's cached. So test
998 * anyway to be sure.)
1035 /* other values not expected here */
1040 /* Apply partitionwise join technique, if possible. */
1046 * have_join_order_restriction
1047 * Detect whether the two relations should be joined to satisfy
1048 * a join-order restriction arising from special or lateral joins.
1050 * In practice this is always used with have_relevant_joinclause(), and so
1051 * could be merged with that function, but it seems clearer to separate the
1052 * two concerns. We need this test because there are degenerate cases where
1053 * a clauseless join must be performed to satisfy join-order restrictions.
1054 * Also, if one rel has a lateral reference to the other, or both are needed
1055 * to compute some PHV, we should consider joining them even if the join would
1058 * Note: this is only a problem if one side of a degenerate outer join
1059 * contains multiple rels, or a clauseless join is required within an
1060 * IN/EXISTS RHS; else we will find a join path via the "last ditch" case in
1061 * join_search_one_level(). We could dispense with this test if we were
1062 * willing to try bushy plans in the "last ditch" case, but that seems much
1069 bool result =
false;
1073 * If either side has a direct lateral reference to the other, attempt the
1074 * join regardless of outer-join considerations.
1081 * Likewise, if both rels are needed to compute some PlaceHolderVar,
1082 * attempt the join regardless of outer-join considerations. (This is not
1083 * very desirable, because a PHV with a large eval_at set will cause a lot
1084 * of probably-useless joins to be considered, but failing to do this can
1085 * cause us to fail to construct a plan at all.)
1087 foreach(l,
root->placeholder_list)
1097 * It's possible that the rels correspond to the left and right sides of a
1098 * degenerate outer join, that is, one with no joinclause mentioning the
1099 * non-nullable side; in which case we should force the join to occur.
1101 * Also, the two rels could represent a clauseless join that has to be
1102 * completed to build up the LHS or RHS of an outer join.
1104 foreach(l,
root->join_info_list)
1108 /* ignore full joins --- other mechanisms handle them */
1112 /* Can we perform the SJ with these rels? */
1127 * Might we need to join these rels to complete the RHS? We have to
1128 * use "overlap" tests since either rel might include a lower SJ that
1129 * has been proven to commute with this one.
1138 /* Likewise for the LHS. */
1148 * We do not force the join to occur if either input rel can legally be
1149 * joined to anything else using joinclauses. This essentially means that
1150 * clauseless bushy joins are put off as long as possible. The reason is
1151 * that when there is a join order restriction high up in the join tree
1152 * (that is, with many rels inside the LHS or RHS), we would otherwise
1153 * expend lots of effort considering very stupid join combinations within
1168 * has_join_restriction
1169 * Detect whether the specified relation has join-order restrictions,
1170 * due to being inside an outer join or an IN (sub-SELECT),
1171 * or participating in any LATERAL references or multi-rel PHVs.
1173 * Essentially, this tests whether have_join_order_restriction() could
1174 * succeed with this rel and some other one. It's OK if we sometimes
1175 * say "true" incorrectly. (Therefore, we don't bother with the relatively
1176 * expensive has_legal_joinclause test.)
1186 foreach(l,
root->placeholder_list)
1195 foreach(l,
root->join_info_list)
1199 /* ignore full joins --- other mechanisms preserve their ordering */
1203 /* ignore if SJ is already contained in rel */
1208 /* restricted if it overlaps LHS or RHS, but doesn't contain SJ */
1219 * has_legal_joinclause
1220 * Detect whether the specified relation can legally be joined
1221 * to any other rels using join clauses.
1223 * We consider only joins to single other relations in the current
1224 * initial_rels list. This is sufficient to get a "true" result in most real
1225 * queries, and an occasional erroneous "false" will only cost a bit more
1226 * planning time. The reason for this limitation is that considering joins to
1227 * other joins would require proving that the other join rel can legally be
1228 * formed, which seems like too much trouble for something that's only a
1229 * heuristic to save planning time. (Note: we must look at initial_rels
1230 * and not all of the query, since when we are planning a sub-joinlist we
1231 * may be forced to make clauseless joins within initial_rels even though
1232 * there are join clauses linking to other parts of the query.)
1239 foreach(lc,
root->initial_rels)
1243 /* ignore rels that are already in "rel" */
1253 /* join_is_legal needs relids of the union */
1257 &sjinfo, &reversed))
1259 /* Yes, this will work */
1273 * is_dummy_rel --- has relation been proven empty?
1281 * A rel that is known dummy will have just one path that is a childless
1282 * Append. (Even if somehow it has more paths, a childless Append will
1283 * have cost zero and hence should be at the front of the pathlist.)
1290 * Initially, a dummy path will just be a childless Append. But in later
1291 * planning stages we might stick a ProjectSetPath and/or ProjectionPath
1292 * on top, since Append can't project. Rather than make assumptions about
1293 * which combinations can occur, just descend through whatever we find.
1310 * Mark a relation as proven empty.
1312 * During GEQO planning, this can get invoked more than once on the same
1313 * baserel struct, so it's worth checking to see if the rel is already marked
1316 * Also, when called during GEQO join planning, we are in a short-lived
1317 * memory context. We must make sure that the dummy path attached to a
1318 * baserel survives the GEQO cycle, else the baserel is trashed for future
1319 * GEQO cycles. On the other hand, when we are marking a joinrel during GEQO,
1320 * we don't want the dummy path to clutter the main planning context. Upshot
1321 * is that the best solution is to explicitly make the dummy path in the same
1322 * context the given RelOptInfo is in.
1329 /* Already marked? */
1333 /* No, so choose correct context to make the dummy path in */
1336 /* Set dummy size estimate */
1339 /* Evict any previously chosen paths */
1343 /* Set up the dummy path */
1348 /* Set or update cheapest_total_path and related fields */
1356 * restriction_is_constant_false --- is a restrictlist just FALSE?
1358 * In cases where a qual is provably constant FALSE, eval_const_expressions
1359 * will generally have thrown away anything that's ANDed with it. In outer
1360 * join situations this will leave us computing cartesian products only to
1361 * decide there's no match for an outer row, which is pretty stupid. So,
1362 * we need to detect the case.
1364 * If only_pushed_down is true, then consider only quals that are pushed-down
1365 * from the point of view of the joinrel.
1370 bool only_pushed_down)
1375 * Despite the above comment, the restriction list we see here might
1376 * possibly have other members besides the FALSE constant, since other
1377 * quals could get "pushed down" to the outer join level. So we check
1378 * each member of the list.
1380 foreach(lc, restrictlist)
1391 /* constant NULL is as good as constant FALSE for our purposes */
1392 if (con->constisnull)
1402 * Assess whether join between given two partitioned relations can be broken
1403 * down into joins between matching partitions; a technique called
1404 * "partitionwise join"
1406 * Partitionwise join is possible when a. Joining relations have same
1407 * partitioning scheme b. There exists an equi-join between the partition keys
1408 * of the two relations.
1410 * Partitionwise join is planned as follows (details: optimizer/README.)
1412 * 1. Create the RelOptInfos for joins between matching partitions i.e
1413 * child-joins and add paths to them.
1415 * 2. Construct Append or MergeAppend paths across the set of child joins.
1416 * This second phase is implemented by generate_partitionwise_join_paths().
1418 * The RelOptInfo, SpecialJoinInfo and restrictlist for each child join are
1419 * obtained by translating the respective parent join structures.
1424 List *parent_restrictlist)
1434 /* Guard against stack overflow due to overly deep partition hierarchy. */
1437 /* Nothing to do, if the join relation is not partitioned. */
1438 if (joinrel->part_scheme == NULL || joinrel->
nparts == 0)
1441 /* The join relation should have consider_partitionwise_join set. */
1445 * We can not perform partitionwise join if either of the joining
1446 * relations is not partitioned.
1453 /* The joining relations should have consider_partitionwise_join set. */
1458 * The partition scheme of the join relation should match that of the
1459 * joining relations.
1461 Assert(joinrel->part_scheme == rel1->part_scheme &&
1462 joinrel->part_scheme == rel2->part_scheme);
1476 * Create child-join relations for this partitioned join, if those don't
1477 * exist. Add paths to child-joins for a pair of child relations
1478 * corresponding to the given pair of parent relations.
1480 for (cnt_parts = 0; cnt_parts < joinrel->
nparts; cnt_parts++)
1487 List *child_restrictlist;
1497 lcr1 =
lnext(parts1, lcr1);
1498 lcr2 =
lnext(parts2, lcr2);
1502 child_rel1 = rel1->part_rels[cnt_parts];
1503 child_rel2 = rel2->part_rels[cnt_parts];
1506 rel1_empty = (child_rel1 == NULL ||
IS_DUMMY_REL(child_rel1));
1507 rel2_empty = (child_rel2 == NULL ||
IS_DUMMY_REL(child_rel2));
1510 * Check for cases where we can prove that this segment of the join
1511 * returns no rows, due to one or both inputs being empty (including
1512 * inputs that have been pruned away entirely). If so just ignore it.
1513 * These rules are equivalent to populate_joinrel_with_paths's rules
1514 * for dummy input relations.
1520 if (rel1_empty || rel2_empty)
1521 continue;
/* ignore this join segment */
1526 continue;
/* ignore this join segment */
1529 if (rel1_empty && rel2_empty)
1530 continue;
/* ignore this join segment */
1533 /* other values not expected here */
1534 elog(
ERROR,
"unrecognized join type: %d",
1540 * If a child has been pruned entirely then we can't generate paths
1541 * for it, so we have to reject partitionwise joining unless we were
1542 * able to eliminate this partition above.
1544 if (child_rel1 == NULL || child_rel2 == NULL)
1547 * Mark the joinrel as unpartitioned so that later functions treat
1555 * If a leaf relation has consider_partitionwise_join=false, it means
1556 * that it's a dummy relation for which we skipped setting up tlist
1557 * expressions and adding EC members in set_append_rel_size(), so
1558 * again we have to fail here.
1575 /* We should never try to join two overlapping sets of rels. */
1579 * Construct SpecialJoinInfo from parent join relations's
1586 /* Find the AppendRelInfo structures */
1592 * Construct restrictions applicable to the child join from those
1593 * applicable to the parent join.
1595 child_restrictlist =
1597 (
Node *) parent_restrictlist,
1598 nappinfos, appinfos);
1600 /* Find or construct the child join's RelOptInfo */
1601 child_joinrel = joinrel->part_rels[cnt_parts];
1605 joinrel, child_restrictlist,
1606 child_sjinfo, nappinfos, appinfos);
1607 joinrel->part_rels[cnt_parts] = child_joinrel;
1613 /* Assert we got the right one */
1616 nappinfos, appinfos)));
1618 /* And make paths for the child join */
1620 child_joinrel, child_sjinfo,
1621 child_restrictlist);
1624 * When there are thousands of partitions involved, this loop will
1625 * accumulate a significant amount of memory usage from objects that
1626 * are only needed within the loop. Free these local objects eagerly
1627 * at the end of each iteration.
1636 * Construct the SpecialJoinInfo for a child-join by translating
1637 * SpecialJoinInfo for the join between parents. left_relids and right_relids
1638 * are the relids of left and right side of the join respectively.
1640 * If translations are added to or removed from this function, consider
1641 * updating free_child_join_sjinfo() accordingly.
1651 int right_nappinfos;
1653 /* Dummy SpecialJoinInfos can be created without any translation. */
1668 left_nappinfos, left_appinfos);
1673 left_nappinfos, left_appinfos);
1677 /* outer-join relids need no adjustment */
1683 pfree(left_appinfos);
1684 pfree(right_appinfos);
1690 * free_child_join_sjinfo
1691 * Free memory consumed by a SpecialJoinInfo created by
1692 * build_child_join_sjinfo()
1694 * Only members that are translated copies of their counterpart in the parent
1695 * SpecialJoinInfo are freed here.
1702 * Dummy SpecialJoinInfos of inner joins do not have any translated fields
1703 * and hence no fields that to be freed.
1727 * semi_rhs_exprs may in principle be freed, but a simple pfree() does
1728 * not suffice, so we leave it alone.
1732 pfree(child_sjinfo);
1736 * compute_partition_bounds
1737 * Compute the partition bounds for a join rel from those for inputs
1746 * If we don't have the partition bounds for the join rel yet, try to
1747 * compute those along with pairs of partitions to be joined.
1749 if (joinrel->
nparts == -1)
1755 Assert(joinrel->boundinfo == NULL);
1756 Assert(joinrel->part_rels == NULL);
1759 * See if the partition bounds for inputs are exactly the same, in
1760 * which case we don't need to work hard: the join rel will have the
1761 * same partition bounds as inputs, and the partitions with the same
1762 * cardinal positions will form the pairs.
1764 * Note: even in cases where one or both inputs have merged bounds, it
1765 * would be possible for both the bounds to be exactly the same, but
1766 * it seems unlikely to be worth the cycles to check.
1774 rel1->boundinfo, rel2->boundinfo))
1776 boundinfo = rel1->boundinfo;
1781 /* Try merging the partition bounds for inputs. */
1788 if (boundinfo == NULL)
1798 joinrel->boundinfo = boundinfo;
1799 joinrel->
nparts = nparts;
1800 joinrel->part_rels =
1806 Assert(joinrel->boundinfo);
1807 Assert(joinrel->part_rels);
1810 * If the join rel's partbounds_merged flag is true, it means inputs
1811 * are not guaranteed to have the same partition bounds, therefore we
1812 * can't assume that the partitions at the same cardinal positions
1813 * form the pairs; let get_matching_part_pairs() generate the pairs.
1814 * Otherwise, nothing to do since we can assume that.
1827 * get_matching_part_pairs
1828 * Generate pairs of partitions to be joined from inputs
1842 for (cnt_parts = 0; cnt_parts < joinrel->
nparts; cnt_parts++)
1844 RelOptInfo *child_joinrel = joinrel->part_rels[cnt_parts];
1851 * If this segment of the join is empty, it means that this segment
1852 * was ignored when previously creating child-join paths for it in
1853 * try_partitionwise_join() as it would not contribute to the join
1854 * result, due to one or both inputs being empty; add NULL to each of
1855 * the given lists so that this segment will be ignored again in that
1860 *parts1 =
lappend(*parts1, NULL);
1861 *parts2 =
lappend(*parts2, NULL);
1866 * Get a relids set of partition(s) involved in this join segment that
1867 * are from the rel1 side.
1874 * Get a child rel for rel1 with the relids. Note that we should have
1875 * the child rel even if rel1 is a join rel, because in that case the
1876 * partitions specified in the relids would have matching/overlapping
1877 * boundaries, so the specified partitions should be considered as
1878 * ones to be joined when planning partitionwise joins of rel1,
1879 * meaning that the child rel would have been built by the time we get
1893 * Get a relids set of partition(s) involved in this join segment that
1894 * are from the rel2 side.
1901 * Get a child rel for rel2 with the relids. See above comments.
1914 * The join of rel1 and rel2 is legal, so is the join of the child
1915 * rels obtained above; add them to the given lists as a join pair
1916 * producing this join segment.
1918 *parts1 =
lappend(*parts1, child_rel1);
1919 *parts2 =
lappend(*parts2, child_rel2);
AppendRelInfo ** find_appinfos_by_relids(PlannerInfo *root, Relids relids, int *nappinfos)
Node * adjust_appendrel_attrs(PlannerInfo *root, Node *node, int nappinfos, AppendRelInfo **appinfos)
Relids adjust_child_relids(Relids relids, int nappinfos, AppendRelInfo **appinfos)
Bitmapset * bms_intersect(const Bitmapset *a, const Bitmapset *b)
bool bms_equal(const Bitmapset *a, const Bitmapset *b)
bool bms_is_subset(const Bitmapset *a, const Bitmapset *b)
int bms_singleton_member(const Bitmapset *a)
void bms_free(Bitmapset *a)
int bms_num_members(const Bitmapset *a)
bool bms_is_member(int x, const Bitmapset *a)
Bitmapset * bms_add_member(Bitmapset *a, int x)
Bitmapset * bms_add_members(Bitmapset *a, const Bitmapset *b)
Bitmapset * bms_union(const Bitmapset *a, const Bitmapset *b)
bool bms_overlap(const Bitmapset *a, const Bitmapset *b)
Bitmapset * bms_copy(const Bitmapset *a)
int errcode(int sqlerrcode)
int errmsg(const char *fmt,...)
#define ereport(elevel,...)
Assert(PointerIsAligned(start, uint64))
if(TABLE==NULL||TABLE_index==NULL)
bool have_relevant_joinclause(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
void add_paths_to_joinrel(PlannerInfo *root, RelOptInfo *joinrel, RelOptInfo *outerrel, RelOptInfo *innerrel, JoinType jointype, SpecialJoinInfo *sjinfo, List *restrictlist)
static void populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, RelOptInfo *joinrel, SpecialJoinInfo *sjinfo, List *restrictlist)
static void try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, RelOptInfo *joinrel, SpecialJoinInfo *parent_sjinfo, List *parent_restrictlist)
static void make_rels_by_clauseless_joins(PlannerInfo *root, RelOptInfo *old_rel, List *other_rels)
bool is_dummy_rel(RelOptInfo *rel)
void join_search_one_level(PlannerInfo *root, int level)
static bool restriction_is_constant_false(List *restrictlist, RelOptInfo *joinrel, bool only_pushed_down)
static void get_matching_part_pairs(PlannerInfo *root, RelOptInfo *joinrel, RelOptInfo *rel1, RelOptInfo *rel2, List **parts1, List **parts2)
RelOptInfo * make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
static bool has_legal_joinclause(PlannerInfo *root, RelOptInfo *rel)
static void compute_partition_bounds(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, RelOptInfo *joinrel, SpecialJoinInfo *parent_sjinfo, List **parts1, List **parts2)
Relids add_outer_joins_to_relids(PlannerInfo *root, Relids input_relids, SpecialJoinInfo *sjinfo, List **pushed_down_joins)
static SpecialJoinInfo * build_child_join_sjinfo(PlannerInfo *root, SpecialJoinInfo *parent_sjinfo, Relids left_relids, Relids right_relids)
void mark_dummy_rel(RelOptInfo *rel)
bool have_join_order_restriction(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
static bool has_join_restriction(PlannerInfo *root, RelOptInfo *rel)
void init_dummy_sjinfo(SpecialJoinInfo *sjinfo, Relids left_relids, Relids right_relids)
static void free_child_join_sjinfo(SpecialJoinInfo *child_sjinfo, SpecialJoinInfo *parent_sjinfo)
static bool join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, Relids joinrelids, SpecialJoinInfo **sjinfo_p, bool *reversed_p)
static void make_rels_by_clause_joins(PlannerInfo *root, RelOptInfo *old_rel, List *other_rels, int first_rel_idx)
List * lappend(List *list, void *datum)
Datum subpath(PG_FUNCTION_ARGS)
void pfree(void *pointer)
void * palloc0(Size size)
MemoryContext GetMemoryChunkContext(void *pointer)
#define IsA(nodeptr, _type_)
static MemoryContext MemoryContextSwitchTo(MemoryContext context)
bool partition_bounds_equal(int partnatts, int16 *parttyplen, bool *parttypbyval, PartitionBoundInfo b1, PartitionBoundInfo b2)
PartitionBoundInfo partition_bounds_merge(int partnatts, FmgrInfo *partsupfunc, Oid *partcollation, RelOptInfo *outer_rel, RelOptInfo *inner_rel, JoinType jointype, List **outer_parts, List **inner_parts)
void set_cheapest(RelOptInfo *parent_rel)
AppendPath * create_append_path(PlannerInfo *root, RelOptInfo *rel, List *subpaths, List *partial_subpaths, List *pathkeys, Relids required_outer, int parallel_workers, bool parallel_aware, double rows)
void add_path(RelOptInfo *parent_rel, Path *new_path)
#define IS_DUMMY_APPEND(p)
#define RINFO_IS_PUSHED_DOWN(rinfo, joinrelids)
#define IS_SIMPLE_REL(rel)
#define IS_PARTITIONED_REL(rel)
#define REL_HAS_ALL_PART_PROPS(rel)
@ RELOPT_OTHER_MEMBER_REL
#define lfirst_node(type, lc)
static int list_length(const List *l)
#define foreach_current_index(var_or_cell)
#define for_each_from(cell, lst, N)
static ListCell * list_head(const List *l)
static ListCell * lnext(const List *l, const ListCell *c)
RelOptInfo * create_unique_paths(PlannerInfo *root, RelOptInfo *rel, SpecialJoinInfo *sjinfo)
static bool DatumGetBool(Datum X)
RelOptInfo * find_base_rel(PlannerInfo *root, int relid)
RelOptInfo * build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel, RelOptInfo *inner_rel, RelOptInfo *parent_joinrel, List *restrictlist, SpecialJoinInfo *sjinfo, int nappinfos, AppendRelInfo **appinfos)
Relids min_join_parameterization(PlannerInfo *root, Relids joinrelids, RelOptInfo *outer_rel, RelOptInfo *inner_rel)
RelOptInfo * find_join_rel(PlannerInfo *root, Relids relids)
RelOptInfo * build_join_rel(PlannerInfo *root, Relids joinrelids, RelOptInfo *outer_rel, RelOptInfo *inner_rel, SpecialJoinInfo *sjinfo, List *pushed_down_joins, List **restrictlist_ptr)
void check_stack_depth(void)
struct FmgrInfo * partsupfunc
Relids lateral_referencers
Relids direct_lateral_relids
bool consider_partitionwise_join