/*------------------------------------------------------------------------- * * joinrels.c * Routines to determine which relations should be joined * * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * * IDENTIFICATION * src/backend/optimizer/path/joinrels.c * *------------------------------------------------------------------------- */ #include "postgres.h" #include "miscadmin.h" #include "optimizer/appendinfo.h" #include "optimizer/joininfo.h" #include "optimizer/pathnode.h" #include "optimizer/paths.h" #include "partitioning/partbounds.h" #include "utils/memutils.h" static void make_rels_by_clause_joins(PlannerInfo *root, RelOptInfo *old_rel, List *other_rels_list, ListCell *other_rels); static void make_rels_by_clauseless_joins(PlannerInfo *root, RelOptInfo *old_rel, List *other_rels); static bool has_join_restriction(PlannerInfo *root, RelOptInfo *rel); static bool has_legal_joinclause(PlannerInfo *root, RelOptInfo *rel); static bool restriction_is_constant_false(List *restrictlist, RelOptInfo *joinrel, bool only_pushed_down); 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 SpecialJoinInfo *build_child_join_sjinfo(PlannerInfo *root, SpecialJoinInfo *parent_sjinfo, Relids left_relids, Relids right_relids); static void compute_partition_bounds(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, RelOptInfo *joinrel, SpecialJoinInfo *parent_sjinfo, List **parts1, List **parts2); static void get_matching_part_pairs(PlannerInfo *root, RelOptInfo *joinrel, RelOptInfo *rel1, RelOptInfo *rel2, List **parts1, List **parts2); /* * join_search_one_level * Consider ways to produce join relations containing exactly 'level' * jointree items. (This is one step of the dynamic-programming method * embodied in standard_join_search.) Join rel nodes for each feasible * combination of lower-level rels are created and returned in a list. * Implementation paths are created for each such joinrel, too. * * level: level of rels we want to make this time * root->join_rel_level[j], 1 <= j < level, is a list of rels containing j items * * The result is returned in root->join_rel_level[level]. */ void join_search_one_level(PlannerInfo *root, int level) { List **joinrels = root->join_rel_level; ListCell *r; int k; Assert(joinrels[level] == NIL); /* Set join_cur_level so that new joinrels are added to proper list */ root->join_cur_level = level; /* * First, consider left-sided and right-sided plans, in which rels of * exactly level-1 member relations are joined against initial relations. * We prefer to join using join clauses, but if we find a rel of level-1 * members that has no join clauses, we will generate Cartesian-product * joins against all initial rels not already contained in it. */ foreach(r, joinrels[level - 1]) { RelOptInfo *old_rel = (RelOptInfo *) lfirst(r); if (old_rel->joininfo != NIL || old_rel->has_eclass_joins || has_join_restriction(root, old_rel)) { /* * There are join clauses or join order restrictions relevant to * this rel, so consider joins between this rel and (only) those * initial rels it is linked to by a clause or restriction. * * At level 2 this condition is symmetric, so there is no need to * look at initial rels before this one in the list; we already * considered such joins when we were at the earlier rel. (The * mirror-image joins are handled automatically by make_join_rel.) * In later passes (level > 2), we join rels of the previous level * to each initial rel they don't already include but have a join * clause or restriction with. */ List *other_rels_list; ListCell *other_rels; if (level == 2) /* consider remaining initial rels */ { other_rels_list = joinrels[level - 1]; other_rels = lnext(other_rels_list, r); } else /* consider all initial rels */ { other_rels_list = joinrels[1]; other_rels = list_head(other_rels_list); } make_rels_by_clause_joins(root, old_rel, other_rels_list, other_rels); } else { /* * Oops, we have a relation that is not joined to any other * relation, either directly or by join-order restrictions. * Cartesian product time. * * We consider a cartesian product with each not-already-included * initial rel, whether it has other join clauses or not. At * level 2, if there are two or more clauseless initial rels, we * will redundantly consider joining them in both directions; but * such cases aren't common enough to justify adding complexity to * avoid the duplicated effort. */ make_rels_by_clauseless_joins(root, old_rel, joinrels[1]); } } /* * Now, consider "bushy plans" in which relations of k initial rels are * joined to relations of level-k initial rels, for 2 <= k <= level-2. * * We only consider bushy-plan joins for pairs of rels where there is a * suitable join clause (or join order restriction), in order to avoid * unreasonable growth of planning time. */ for (k = 2;; k++) { int other_level = level - k; /* * Since make_join_rel(x, y) handles both x,y and y,x cases, we only * need to go as far as the halfway point. */ if (k > other_level) break; foreach(r, joinrels[k]) { RelOptInfo *old_rel = (RelOptInfo *) lfirst(r); List *other_rels_list; ListCell *other_rels; ListCell *r2; /* * We can ignore relations without join clauses here, unless they * participate in join-order restrictions --- then we might have * to force a bushy join plan. */ if (old_rel->joininfo == NIL && !old_rel->has_eclass_joins && !has_join_restriction(root, old_rel)) continue; if (k == other_level) { /* only consider remaining rels */ other_rels_list = joinrels[k]; other_rels = lnext(other_rels_list, r); } else { other_rels_list = joinrels[other_level]; other_rels = list_head(other_rels_list); } for_each_cell(r2, other_rels_list, other_rels) { RelOptInfo *new_rel = (RelOptInfo *) lfirst(r2); if (!bms_overlap(old_rel->relids, new_rel->relids)) { /* * OK, we can build a rel of the right level from this * pair of rels. Do so if there is at least one relevant * join clause or join order restriction. */ if (have_relevant_joinclause(root, old_rel, new_rel) || have_join_order_restriction(root, old_rel, new_rel)) { (void) make_join_rel(root, old_rel, new_rel); } } } } } /*---------- * Last-ditch effort: if we failed to find any usable joins so far, force * a set of cartesian-product joins to be generated. This handles the * special case where all the available rels have join clauses but we * cannot use any of those clauses yet. This can only happen when we are * considering a join sub-problem (a sub-joinlist) and all the rels in the * sub-problem have only join clauses with rels outside the sub-problem. * An example is * * SELECT ... FROM a INNER JOIN b ON TRUE, c, d, ... * WHERE a.w = c.x and b.y = d.z; * * If the "a INNER JOIN b" sub-problem does not get flattened into the * upper level, we must be willing to make a cartesian join of a and b; * but the code above will not have done so, because it thought that both * a and b have joinclauses. We consider only left-sided and right-sided * cartesian joins in this case (no bushy). *---------- */ if (joinrels[level] == NIL) { /* * This loop is just like the first one, except we always call * make_rels_by_clauseless_joins(). */ foreach(r, joinrels[level - 1]) { RelOptInfo *old_rel = (RelOptInfo *) lfirst(r); make_rels_by_clauseless_joins(root, old_rel, joinrels[1]); } /*---------- * When special joins are involved, there may be no legal way * to make an N-way join for some values of N. For example consider * * SELECT ... FROM t1 WHERE * x IN (SELECT ... FROM t2,t3 WHERE ...) AND * y IN (SELECT ... FROM t4,t5 WHERE ...) * * We will flatten this query to a 5-way join problem, but there are * no 4-way joins that join_is_legal() will consider legal. We have * to accept failure at level 4 and go on to discover a workable * bushy plan at level 5. * * However, if there are no special joins and no lateral references * then join_is_legal() should never fail, and so the following sanity * check is useful. *---------- */ if (joinrels[level] == NIL && root->join_info_list == NIL && !root->hasLateralRTEs) elog(ERROR, "failed to build any %d-way joins", level); } } /* * make_rels_by_clause_joins * Build joins between the given relation 'old_rel' and other relations * that participate in join clauses that 'old_rel' also participates in * (or participate in join-order restrictions with it). * The join rels are returned in root->join_rel_level[join_cur_level]. * * Note: at levels above 2 we will generate the same joined relation in * multiple ways --- for example (a join b) join c is the same RelOptInfo as * (b join c) join a, though the second case will add a different set of Paths * to it. This is the reason for using the join_rel_level mechanism, which * automatically ensures that each new joinrel is only added to the list once. * * 'old_rel' is the relation entry for the relation to be joined * 'other_rels_list': a list containing the other * rels to be considered for joining * 'other_rels': the first cell to be considered * * Currently, this is only used with initial rels in other_rels, but it * will work for joining to joinrels too. */ static void make_rels_by_clause_joins(PlannerInfo *root, RelOptInfo *old_rel, List *other_rels_list, ListCell *other_rels) { ListCell *l; for_each_cell(l, other_rels_list, other_rels) { RelOptInfo *other_rel = (RelOptInfo *) lfirst(l); if (!bms_overlap(old_rel->relids, other_rel->relids) && (have_relevant_joinclause(root, old_rel, other_rel) || have_join_order_restriction(root, old_rel, other_rel))) { (void) make_join_rel(root, old_rel, other_rel); } } } /* * make_rels_by_clauseless_joins * Given a relation 'old_rel' and a list of other relations * 'other_rels', create a join relation between 'old_rel' and each * member of 'other_rels' that isn't already included in 'old_rel'. * The join rels are returned in root->join_rel_level[join_cur_level]. * * 'old_rel' is the relation entry for the relation to be joined * 'other_rels': a list containing the other rels to be considered for joining * * Currently, this is only used with initial rels in other_rels, but it would * work for joining to joinrels too. */ static void make_rels_by_clauseless_joins(PlannerInfo *root, RelOptInfo *old_rel, List *other_rels) { ListCell *l; foreach(l, other_rels) { RelOptInfo *other_rel = (RelOptInfo *) lfirst(l); if (!bms_overlap(other_rel->relids, old_rel->relids)) { (void) make_join_rel(root, old_rel, other_rel); } } } /* * join_is_legal * Determine whether a proposed join is legal given the query's * join order constraints; and if it is, determine the join type. * * Caller must supply not only the two rels, but the union of their relids. * (We could simplify the API by computing joinrelids locally, but this * would be redundant work in the normal path through make_join_rel.) * * On success, *sjinfo_p is set to NULL if this is to be a plain inner join, * else it's set to point to the associated SpecialJoinInfo node. Also, * *reversed_p is set true if the given relations need to be swapped to * match the SpecialJoinInfo node. */ static bool join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, Relids joinrelids, SpecialJoinInfo **sjinfo_p, bool *reversed_p) { SpecialJoinInfo *match_sjinfo; bool reversed; bool unique_ified; bool must_be_leftjoin; ListCell *l; /* * Ensure output params are set on failure return. This is just to * suppress uninitialized-variable warnings from overly anal compilers. */ *sjinfo_p = NULL; *reversed_p = false; /* * If we have any special joins, the proposed join might be illegal; and * in any case we have to determine its join type. Scan the join info * list for matches and conflicts. */ match_sjinfo = NULL; reversed = false; unique_ified = false; must_be_leftjoin = false; foreach(l, root->join_info_list) { SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l); /* * This special join is not relevant unless its RHS overlaps the * proposed join. (Check this first as a fast path for dismissing * most irrelevant SJs quickly.) */ if (!bms_overlap(sjinfo->min_righthand, joinrelids)) continue; /* * Also, not relevant if proposed join is fully contained within RHS * (ie, we're still building up the RHS). */ if (bms_is_subset(joinrelids, sjinfo->min_righthand)) continue; /* * Also, not relevant if SJ is already done within either input. */ if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) && bms_is_subset(sjinfo->min_righthand, rel1->relids)) continue; if (bms_is_subset(sjinfo->min_lefthand, rel2->relids) && bms_is_subset(sjinfo->min_righthand, rel2->relids)) continue; /* * If it's a semijoin and we already joined the RHS to any other rels * within either input, then we must have unique-ified the RHS at that * point (see below). Therefore the semijoin is no longer relevant in * this join path. */ if (sjinfo->jointype == JOIN_SEMI) { if (bms_is_subset(sjinfo->syn_righthand, rel1->relids) && !bms_equal(sjinfo->syn_righthand, rel1->relids)) continue; if (bms_is_subset(sjinfo->syn_righthand, rel2->relids) && !bms_equal(sjinfo->syn_righthand, rel2->relids)) continue; } /* * If one input contains min_lefthand and the other contains * min_righthand, then we can perform the SJ at this join. * * Reject if we get matches to more than one SJ; that implies we're * considering something that's not really valid. */ if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) && bms_is_subset(sjinfo->min_righthand, rel2->relids)) { if (match_sjinfo) return false; /* invalid join path */ match_sjinfo = sjinfo; reversed = false; } else if (bms_is_subset(sjinfo->min_lefthand, rel2->relids) && bms_is_subset(sjinfo->min_righthand, rel1->relids)) { if (match_sjinfo) return false; /* invalid join path */ match_sjinfo = sjinfo; reversed = true; } else if (sjinfo->jointype == JOIN_SEMI && bms_equal(sjinfo->syn_righthand, rel2->relids) && create_unique_path(root, rel2, rel2->cheapest_total_path, sjinfo) != NULL) { /*---------- * For a semijoin, we can join the RHS to anything else by * unique-ifying the RHS (if the RHS can be unique-ified). * We will only get here if we have the full RHS but less * than min_lefthand on the LHS. * * The reason to consider such a join path is exemplified by * SELECT ... FROM a,b WHERE (a.x,b.y) IN (SELECT c1,c2 FROM c) * If we insist on doing this as a semijoin we will first have * to form the cartesian product of A*B. But if we unique-ify * C then the semijoin becomes a plain innerjoin and we can join * in any order, eg C to A and then to B. When C is much smaller * than A and B this can be a huge win. So we allow C to be * joined to just A or just B here, and then make_join_rel has * to handle the case properly. * * Note that actually we'll allow unique-ified C to be joined to * some other relation D here, too. That is legal, if usually not * very sane, and this routine is only concerned with legality not * with whether the join is good strategy. *---------- */ if (match_sjinfo) return false; /* invalid join path */ match_sjinfo = sjinfo; reversed = false; unique_ified = true; } else if (sjinfo->jointype == JOIN_SEMI && bms_equal(sjinfo->syn_righthand, rel1->relids) && create_unique_path(root, rel1, rel1->cheapest_total_path, sjinfo) != NULL) { /* Reversed semijoin case */ if (match_sjinfo) return false; /* invalid join path */ match_sjinfo = sjinfo; reversed = true; unique_ified = true; } else { /* * Otherwise, the proposed join overlaps the RHS but isn't a valid * implementation of this SJ. But don't panic quite yet: the RHS * violation might have occurred previously, in one or both input * relations, in which case we must have previously decided that * it was OK to commute some other SJ with this one. If we need * to perform this join to finish building up the RHS, rejecting * it could lead to not finding any plan at all. (This can occur * because of the heuristics elsewhere in this file that postpone * clauseless joins: we might not consider doing a clauseless join * within the RHS until after we've performed other, validly * commutable SJs with one or both sides of the clauseless join.) * This consideration boils down to the rule that if both inputs * overlap the RHS, we can allow the join --- they are either * fully within the RHS, or represent previously-allowed joins to * rels outside it. */ if (bms_overlap(rel1->relids, sjinfo->min_righthand) && bms_overlap(rel2->relids, sjinfo->min_righthand)) continue; /* assume valid previous violation of RHS */ /* * The proposed join could still be legal, but only if we're * allowed to associate it into the RHS of this SJ. That means * this SJ must be a LEFT join (not SEMI or ANTI, and certainly * not FULL) and the proposed join must not overlap the LHS. */ if (sjinfo->jointype != JOIN_LEFT || bms_overlap(joinrelids, sjinfo->min_lefthand)) return false; /* invalid join path */ /* * To be valid, the proposed join must be a LEFT join; otherwise * it can't associate into this SJ's RHS. But we may not yet have * found the SpecialJoinInfo matching the proposed join, so we * can't test that yet. Remember the requirement for later. */ must_be_leftjoin = true; } } /* * Fail if violated any SJ's RHS and didn't match to a LEFT SJ: the * proposed join can't associate into an SJ's RHS. * * Also, fail if the proposed join's predicate isn't strict; we're * essentially checking to see if we can apply outer-join identity 3, and * that's a requirement. (This check may be redundant with checks in * make_outerjoininfo, but I'm not quite sure, and it's cheap to test.) */ if (must_be_leftjoin && (match_sjinfo == NULL || match_sjinfo->jointype != JOIN_LEFT || !match_sjinfo->lhs_strict)) return false; /* invalid join path */ /* * We also have to check for constraints imposed by LATERAL references. */ if (root->hasLateralRTEs) { bool lateral_fwd; bool lateral_rev; Relids join_lateral_rels; /* * The proposed rels could each contain lateral references to the * other, in which case the join is impossible. If there are lateral * references in just one direction, then the join has to be done with * a nestloop with the lateral referencer on the inside. If the join * matches an SJ that cannot be implemented by such a nestloop, the * join is impossible. * * Also, if the lateral reference is only indirect, we should reject * the join; whatever rel(s) the reference chain goes through must be * joined to first. * * Another case that might keep us from building a valid plan is the * implementation restriction described by have_dangerous_phv(). */ lateral_fwd = bms_overlap(rel1->relids, rel2->lateral_relids); lateral_rev = bms_overlap(rel2->relids, rel1->lateral_relids); if (lateral_fwd && lateral_rev) return false; /* have lateral refs in both directions */ if (lateral_fwd) { /* has to be implemented as nestloop with rel1 on left */ if (match_sjinfo && (reversed || unique_ified || match_sjinfo->jointype == JOIN_FULL)) return false; /* not implementable as nestloop */ /* check there is a direct reference from rel2 to rel1 */ if (!bms_overlap(rel1->relids, rel2->direct_lateral_relids)) return false; /* only indirect refs, so reject */ /* check we won't have a dangerous PHV */ if (have_dangerous_phv(root, rel1->relids, rel2->lateral_relids)) return false; /* might be unable to handle required PHV */ } else if (lateral_rev) { /* has to be implemented as nestloop with rel2 on left */ if (match_sjinfo && (!reversed || unique_ified || match_sjinfo->jointype == JOIN_FULL)) return false; /* not implementable as nestloop */ /* check there is a direct reference from rel1 to rel2 */ if (!bms_overlap(rel2->relids, rel1->direct_lateral_relids)) return false; /* only indirect refs, so reject */ /* check we won't have a dangerous PHV */ if (have_dangerous_phv(root, rel2->relids, rel1->lateral_relids)) return false; /* might be unable to handle required PHV */ } /* * LATERAL references could also cause problems later on if we accept * this join: if the join's minimum parameterization includes any rels * that would have to be on the inside of an outer join with this join * rel, then it's never going to be possible to build the complete * query using this join. We should reject this join not only because * it'll save work, but because if we don't, the clauseless-join * heuristics might think that legality of this join means that some * other join rel need not be formed, and that could lead to failure * to find any plan at all. We have to consider not only rels that * are directly on the inner side of an OJ with the joinrel, but also * ones that are indirectly so, so search to find all such rels. */ join_lateral_rels = min_join_parameterization(root, joinrelids, rel1, rel2); if (join_lateral_rels) { Relids join_plus_rhs = bms_copy(joinrelids); bool more; do { more = false; foreach(l, root->join_info_list) { SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l); /* ignore full joins --- their ordering is predetermined */ if (sjinfo->jointype == JOIN_FULL) continue; if (bms_overlap(sjinfo->min_lefthand, join_plus_rhs) && !bms_is_subset(sjinfo->min_righthand, join_plus_rhs)) { join_plus_rhs = bms_add_members(join_plus_rhs, sjinfo->min_righthand); more = true; } } } while (more); if (bms_overlap(join_plus_rhs, join_lateral_rels)) return false; /* will not be able to join to some RHS rel */ } } /* Otherwise, it's a valid join */ *sjinfo_p = match_sjinfo; *reversed_p = reversed; return true; } /* * make_join_rel * Find or create a join RelOptInfo that represents the join of * the two given rels, and add to it path information for paths * created with the two rels as outer and inner rel. * (The join rel may already contain paths generated from other * pairs of rels that add up to the same set of base rels.) * * NB: will return NULL if attempted join is not valid. This can happen * when working with outer joins, or with IN or EXISTS clauses that have been * turned into joins. */ RelOptInfo * make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2) { Relids joinrelids; SpecialJoinInfo *sjinfo; bool reversed; SpecialJoinInfo sjinfo_data; RelOptInfo *joinrel; List *restrictlist; /* We should never try to join two overlapping sets of rels. */ Assert(!bms_overlap(rel1->relids, rel2->relids)); /* Construct Relids set that identifies the joinrel. */ joinrelids = bms_union(rel1->relids, rel2->relids); /* Check validity and determine join type. */ if (!join_is_legal(root, rel1, rel2, joinrelids, &sjinfo, &reversed)) { /* invalid join path */ bms_free(joinrelids); return NULL; } /* Swap rels if needed to match the join info. */ if (reversed) { RelOptInfo *trel = rel1; rel1 = rel2; rel2 = trel; } /* * If it's a plain inner join, then we won't have found anything in * join_info_list. Make up a SpecialJoinInfo so that selectivity * estimation functions will know what's being joined. */ if (sjinfo == NULL) { sjinfo = &sjinfo_data; sjinfo->type = T_SpecialJoinInfo; sjinfo->min_lefthand = rel1->relids; sjinfo->min_righthand = rel2->relids; sjinfo->syn_lefthand = rel1->relids; sjinfo->syn_righthand = rel2->relids; sjinfo->jointype = JOIN_INNER; /* we don't bother trying to make the remaining fields valid */ sjinfo->lhs_strict = false; sjinfo->delay_upper_joins = false; sjinfo->semi_can_btree = false; sjinfo->semi_can_hash = false; sjinfo->semi_operators = NIL; sjinfo->semi_rhs_exprs = NIL; } /* * Find or build the join RelOptInfo, and compute the restrictlist that * goes with this particular joining. */ joinrel = build_join_rel(root, joinrelids, rel1, rel2, sjinfo, &restrictlist); /* * If we've already proven this join is empty, we needn't consider any * more paths for it. */ if (is_dummy_rel(joinrel)) { bms_free(joinrelids); return joinrel; } /* Add paths to the join relation. */ populate_joinrel_with_paths(root, rel1, rel2, joinrel, sjinfo, restrictlist); bms_free(joinrelids); return joinrel; } /* * populate_joinrel_with_paths * Add paths to the given joinrel for given pair of joining relations. The * SpecialJoinInfo provides details about the join and the restrictlist * contains the join clauses and the other clauses applicable for given pair * of the joining relations. */ static void populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, RelOptInfo *joinrel, SpecialJoinInfo *sjinfo, List *restrictlist) { /* * Consider paths using each rel as both outer and inner. Depending on * the join type, a provably empty outer or inner rel might mean the join * is provably empty too; in which case throw away any previously computed * paths and mark the join as dummy. (We do it this way since it's * conceivable that dummy-ness of a multi-element join might only be * noticeable for certain construction paths.) * * Also, a provably constant-false join restriction typically means that * we can skip evaluating one or both sides of the join. We do this by * marking the appropriate rel as dummy. For outer joins, a * constant-false restriction that is pushed down still means the whole * join is dummy, while a non-pushed-down one means that no inner rows * will join so we can treat the inner rel as dummy. * * We need only consider the jointypes that appear in join_info_list, plus * JOIN_INNER. */ switch (sjinfo->jointype) { case JOIN_INNER: if (is_dummy_rel(rel1) || is_dummy_rel(rel2) || restriction_is_constant_false(restrictlist, joinrel, false)) { mark_dummy_rel(joinrel); break; } add_paths_to_joinrel(root, joinrel, rel1, rel2, JOIN_INNER, sjinfo, restrictlist); add_paths_to_joinrel(root, joinrel, rel2, rel1, JOIN_INNER, sjinfo, restrictlist); break; case JOIN_LEFT: if (is_dummy_rel(rel1) || restriction_is_constant_false(restrictlist, joinrel, true)) { mark_dummy_rel(joinrel); break; } if (restriction_is_constant_false(restrictlist, joinrel, false) && bms_is_subset(rel2->relids, sjinfo->syn_righthand)) mark_dummy_rel(rel2); add_paths_to_joinrel(root, joinrel, rel1, rel2, JOIN_LEFT, sjinfo, restrictlist); add_paths_to_joinrel(root, joinrel, rel2, rel1, JOIN_RIGHT, sjinfo, restrictlist); break; case JOIN_FULL: if ((is_dummy_rel(rel1) && is_dummy_rel(rel2)) || restriction_is_constant_false(restrictlist, joinrel, true)) { mark_dummy_rel(joinrel); break; } add_paths_to_joinrel(root, joinrel, rel1, rel2, JOIN_FULL, sjinfo, restrictlist); add_paths_to_joinrel(root, joinrel, rel2, rel1, JOIN_FULL, sjinfo, restrictlist); /* * If there are join quals that aren't mergeable or hashable, we * may not be able to build any valid plan. Complain here so that * we can give a somewhat-useful error message. (Since we have no * flexibility of planning for a full join, there's no chance of * succeeding later with another pair of input rels.) */ if (joinrel->pathlist == NIL) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("FULL JOIN is only supported with merge-joinable or hash-joinable join conditions"))); break; case JOIN_SEMI: /* * We might have a normal semijoin, or a case where we don't have * enough rels to do the semijoin but can unique-ify the RHS and * then do an innerjoin (see comments in join_is_legal). In the * latter case we can't apply JOIN_SEMI joining. */ if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) && bms_is_subset(sjinfo->min_righthand, rel2->relids)) { if (is_dummy_rel(rel1) || is_dummy_rel(rel2) || restriction_is_constant_false(restrictlist, joinrel, false)) { mark_dummy_rel(joinrel); break; } add_paths_to_joinrel(root, joinrel, rel1, rel2, JOIN_SEMI, sjinfo, restrictlist); } /* * If we know how to unique-ify the RHS and one input rel is * exactly the RHS (not a superset) we can consider unique-ifying * it and then doing a regular join. (The create_unique_path * check here is probably redundant with what join_is_legal did, * but if so the check is cheap because it's cached. So test * anyway to be sure.) */ if (bms_equal(sjinfo->syn_righthand, rel2->relids) && create_unique_path(root, rel2, rel2->cheapest_total_path, sjinfo) != NULL) { if (is_dummy_rel(rel1) || is_dummy_rel(rel2) || restriction_is_constant_false(restrictlist, joinrel, false)) { mark_dummy_rel(joinrel); break; } add_paths_to_joinrel(root, joinrel, rel1, rel2, JOIN_UNIQUE_INNER, sjinfo, restrictlist); add_paths_to_joinrel(root, joinrel, rel2, rel1, JOIN_UNIQUE_OUTER, sjinfo, restrictlist); } break; case JOIN_ANTI: if (is_dummy_rel(rel1) || restriction_is_constant_false(restrictlist, joinrel, true)) { mark_dummy_rel(joinrel); break; } if (restriction_is_constant_false(restrictlist, joinrel, false) && bms_is_subset(rel2->relids, sjinfo->syn_righthand)) mark_dummy_rel(rel2); add_paths_to_joinrel(root, joinrel, rel1, rel2, JOIN_ANTI, sjinfo, restrictlist); break; default: /* other values not expected here */ elog(ERROR, "unrecognized join type: %d", (int) sjinfo->jointype); break; } /* Apply partitionwise join technique, if possible. */ try_partitionwise_join(root, rel1, rel2, joinrel, sjinfo, restrictlist); } /* * have_join_order_restriction * Detect whether the two relations should be joined to satisfy * a join-order restriction arising from special or lateral joins. * * In practice this is always used with have_relevant_joinclause(), and so * could be merged with that function, but it seems clearer to separate the * two concerns. We need this test because there are degenerate cases where * a clauseless join must be performed to satisfy join-order restrictions. * Also, if one rel has a lateral reference to the other, or both are needed * to compute some PHV, we should consider joining them even if the join would * be clauseless. * * Note: this is only a problem if one side of a degenerate outer join * contains multiple rels, or a clauseless join is required within an * IN/EXISTS RHS; else we will find a join path via the "last ditch" case in * join_search_one_level(). We could dispense with this test if we were * willing to try bushy plans in the "last ditch" case, but that seems much * less efficient. */ bool have_join_order_restriction(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2) { bool result = false; ListCell *l; /* * If either side has a direct lateral reference to the other, attempt the * join regardless of outer-join considerations. */ if (bms_overlap(rel1->relids, rel2->direct_lateral_relids) || bms_overlap(rel2->relids, rel1->direct_lateral_relids)) return true; /* * Likewise, if both rels are needed to compute some PlaceHolderVar, * attempt the join regardless of outer-join considerations. (This is not * very desirable, because a PHV with a large eval_at set will cause a lot * of probably-useless joins to be considered, but failing to do this can * cause us to fail to construct a plan at all.) */ foreach(l, root->placeholder_list) { PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l); if (bms_is_subset(rel1->relids, phinfo->ph_eval_at) && bms_is_subset(rel2->relids, phinfo->ph_eval_at)) return true; } /* * It's possible that the rels correspond to the left and right sides of a * degenerate outer join, that is, one with no joinclause mentioning the * non-nullable side; in which case we should force the join to occur. * * Also, the two rels could represent a clauseless join that has to be * completed to build up the LHS or RHS of an outer join. */ foreach(l, root->join_info_list) { SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l); /* ignore full joins --- other mechanisms handle them */ if (sjinfo->jointype == JOIN_FULL) continue; /* Can we perform the SJ with these rels? */ if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) && bms_is_subset(sjinfo->min_righthand, rel2->relids)) { result = true; break; } if (bms_is_subset(sjinfo->min_lefthand, rel2->relids) && bms_is_subset(sjinfo->min_righthand, rel1->relids)) { result = true; break; } /* * Might we need to join these rels to complete the RHS? We have to * use "overlap" tests since either rel might include a lower SJ that * has been proven to commute with this one. */ if (bms_overlap(sjinfo->min_righthand, rel1->relids) && bms_overlap(sjinfo->min_righthand, rel2->relids)) { result = true; break; } /* Likewise for the LHS. */ if (bms_overlap(sjinfo->min_lefthand, rel1->relids) && bms_overlap(sjinfo->min_lefthand, rel2->relids)) { result = true; break; } } /* * We do not force the join to occur if either input rel can legally be * joined to anything else using joinclauses. This essentially means that * clauseless bushy joins are put off as long as possible. The reason is * that when there is a join order restriction high up in the join tree * (that is, with many rels inside the LHS or RHS), we would otherwise * expend lots of effort considering very stupid join combinations within * its LHS or RHS. */ if (result) { if (has_legal_joinclause(root, rel1) || has_legal_joinclause(root, rel2)) result = false; } return result; } /* * has_join_restriction * Detect whether the specified relation has join-order restrictions, * due to being inside an outer join or an IN (sub-SELECT), * or participating in any LATERAL references or multi-rel PHVs. * * Essentially, this tests whether have_join_order_restriction() could * succeed with this rel and some other one. It's OK if we sometimes * say "true" incorrectly. (Therefore, we don't bother with the relatively * expensive has_legal_joinclause test.) */ static bool has_join_restriction(PlannerInfo *root, RelOptInfo *rel) { ListCell *l; if (rel->lateral_relids != NULL || rel->lateral_referencers != NULL) return true; foreach(l, root->placeholder_list) { PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l); if (bms_is_subset(rel->relids, phinfo->ph_eval_at) && !bms_equal(rel->relids, phinfo->ph_eval_at)) return true; } foreach(l, root->join_info_list) { SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l); /* ignore full joins --- other mechanisms preserve their ordering */ if (sjinfo->jointype == JOIN_FULL) continue; /* ignore if SJ is already contained in rel */ if (bms_is_subset(sjinfo->min_lefthand, rel->relids) && bms_is_subset(sjinfo->min_righthand, rel->relids)) continue; /* restricted if it overlaps LHS or RHS, but doesn't contain SJ */ if (bms_overlap(sjinfo->min_lefthand, rel->relids) || bms_overlap(sjinfo->min_righthand, rel->relids)) return true; } return false; } /* * has_legal_joinclause * Detect whether the specified relation can legally be joined * to any other rels using join clauses. * * We consider only joins to single other relations in the current * initial_rels list. This is sufficient to get a "true" result in most real * queries, and an occasional erroneous "false" will only cost a bit more * planning time. The reason for this limitation is that considering joins to * other joins would require proving that the other join rel can legally be * formed, which seems like too much trouble for something that's only a * heuristic to save planning time. (Note: we must look at initial_rels * and not all of the query, since when we are planning a sub-joinlist we * may be forced to make clauseless joins within initial_rels even though * there are join clauses linking to other parts of the query.) */ static bool has_legal_joinclause(PlannerInfo *root, RelOptInfo *rel) { ListCell *lc; foreach(lc, root->initial_rels) { RelOptInfo *rel2 = (RelOptInfo *) lfirst(lc); /* ignore rels that are already in "rel" */ if (bms_overlap(rel->relids, rel2->relids)) continue; if (have_relevant_joinclause(root, rel, rel2)) { Relids joinrelids; SpecialJoinInfo *sjinfo; bool reversed; /* join_is_legal needs relids of the union */ joinrelids = bms_union(rel->relids, rel2->relids); if (join_is_legal(root, rel, rel2, joinrelids, &sjinfo, &reversed)) { /* Yes, this will work */ bms_free(joinrelids); return true; } bms_free(joinrelids); } } return false; } /* * There's a pitfall for creating parameterized nestloops: suppose the inner * rel (call it A) has a parameter that is a PlaceHolderVar, and that PHV's * minimum eval_at set includes the outer rel (B) and some third rel (C). * We might think we could create a B/A nestloop join that's parameterized by * C. But we would end up with a plan in which the PHV's expression has to be * evaluated as a nestloop parameter at the B/A join; and the executor is only * set up to handle simple Vars as NestLoopParams. Rather than add complexity * and overhead to the executor for such corner cases, it seems better to * forbid the join. (Note that we can still make use of A's parameterized * path with pre-joined B+C as the outer rel. have_join_order_restriction() * ensures that we will consider making such a join even if there are not * other reasons to do so.) * * So we check whether any PHVs used in the query could pose such a hazard. * We don't have any simple way of checking whether a risky PHV would actually * be used in the inner plan, and the case is so unusual that it doesn't seem * worth working very hard on it. * * This needs to be checked in two places. If the inner rel's minimum * parameterization would trigger the restriction, then join_is_legal() should * reject the join altogether, because there will be no workable paths for it. * But joinpath.c has to check again for every proposed nestloop path, because * the inner path might have more than the minimum parameterization, causing * some PHV to be dangerous for it that otherwise wouldn't be. */ bool have_dangerous_phv(PlannerInfo *root, Relids outer_relids, Relids inner_params) { ListCell *lc; foreach(lc, root->placeholder_list) { PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(lc); if (!bms_is_subset(phinfo->ph_eval_at, inner_params)) continue; /* ignore, could not be a nestloop param */ if (!bms_overlap(phinfo->ph_eval_at, outer_relids)) continue; /* ignore, not relevant to this join */ if (bms_is_subset(phinfo->ph_eval_at, outer_relids)) continue; /* safe, it can be eval'd within outerrel */ /* Otherwise, it's potentially unsafe, so reject the join */ return true; } /* OK to perform the join */ return false; } /* * is_dummy_rel --- has relation been proven empty? */ bool is_dummy_rel(RelOptInfo *rel) { Path *path; /* * A rel that is known dummy will have just one path that is a childless * Append. (Even if somehow it has more paths, a childless Append will * have cost zero and hence should be at the front of the pathlist.) */ if (rel->pathlist == NIL) return false; path = (Path *) linitial(rel->pathlist); /* * Initially, a dummy path will just be a childless Append. But in later * planning stages we might stick a ProjectSetPath and/or ProjectionPath * on top, since Append can't project. Rather than make assumptions about * which combinations can occur, just descend through whatever we find. */ for (;;) { if (IsA(path, ProjectionPath)) path = ((ProjectionPath *) path)->subpath; else if (IsA(path, ProjectSetPath)) path = ((ProjectSetPath *) path)->subpath; else break; } if (IS_DUMMY_APPEND(path)) return true; return false; } /* * Mark a relation as proven empty. * * During GEQO planning, this can get invoked more than once on the same * baserel struct, so it's worth checking to see if the rel is already marked * dummy. * * Also, when called during GEQO join planning, we are in a short-lived * memory context. We must make sure that the dummy path attached to a * baserel survives the GEQO cycle, else the baserel is trashed for future * GEQO cycles. On the other hand, when we are marking a joinrel during GEQO, * we don't want the dummy path to clutter the main planning context. Upshot * is that the best solution is to explicitly make the dummy path in the same * context the given RelOptInfo is in. */ void mark_dummy_rel(RelOptInfo *rel) { MemoryContext oldcontext; /* Already marked? */ if (is_dummy_rel(rel)) return; /* No, so choose correct context to make the dummy path in */ oldcontext = MemoryContextSwitchTo(GetMemoryChunkContext(rel)); /* Set dummy size estimate */ rel->rows = 0; /* Evict any previously chosen paths */ rel->pathlist = NIL; rel->partial_pathlist = NIL; /* Set up the dummy path */ add_path(rel, (Path *) create_append_path(NULL, rel, NIL, NIL, NIL, rel->lateral_relids, 0, false, -1)); /* Set or update cheapest_total_path and related fields */ set_cheapest(rel); MemoryContextSwitchTo(oldcontext); } /* * restriction_is_constant_false --- is a restrictlist just FALSE? * * In cases where a qual is provably constant FALSE, eval_const_expressions * will generally have thrown away anything that's ANDed with it. In outer * join situations this will leave us computing cartesian products only to * decide there's no match for an outer row, which is pretty stupid. So, * we need to detect the case. * * If only_pushed_down is true, then consider only quals that are pushed-down * from the point of view of the joinrel. */ static bool restriction_is_constant_false(List *restrictlist, RelOptInfo *joinrel, bool only_pushed_down) { ListCell *lc; /* * Despite the above comment, the restriction list we see here might * possibly have other members besides the FALSE constant, since other * quals could get "pushed down" to the outer join level. So we check * each member of the list. */ foreach(lc, restrictlist) { RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc); if (only_pushed_down && !RINFO_IS_PUSHED_DOWN(rinfo, joinrel->relids)) continue; if (rinfo->clause && IsA(rinfo->clause, Const)) { Const *con = (Const *) rinfo->clause; /* constant NULL is as good as constant FALSE for our purposes */ if (con->constisnull) return true; if (!DatumGetBool(con->constvalue)) return true; } } return false; } /* * Assess whether join between given two partitioned relations can be broken * down into joins between matching partitions; a technique called * "partitionwise join" * * Partitionwise join is possible when a. Joining relations have same * partitioning scheme b. There exists an equi-join between the partition keys * of the two relations. * * Partitionwise join is planned as follows (details: optimizer/README.) * * 1. Create the RelOptInfos for joins between matching partitions i.e * child-joins and add paths to them. * * 2. Construct Append or MergeAppend paths across the set of child joins. * This second phase is implemented by generate_partitionwise_join_paths(). * * The RelOptInfo, SpecialJoinInfo and restrictlist for each child join are * obtained by translating the respective parent join structures. */ static void try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, RelOptInfo *joinrel, SpecialJoinInfo *parent_sjinfo, List *parent_restrictlist) { bool rel1_is_simple = IS_SIMPLE_REL(rel1); bool rel2_is_simple = IS_SIMPLE_REL(rel2); List *parts1 = NIL; List *parts2 = NIL; ListCell *lcr1 = NULL; ListCell *lcr2 = NULL; int cnt_parts; /* Guard against stack overflow due to overly deep partition hierarchy. */ check_stack_depth(); /* Nothing to do, if the join relation is not partitioned. */ if (joinrel->part_scheme == NULL || joinrel->nparts == 0) return; /* The join relation should have consider_partitionwise_join set. */ Assert(joinrel->consider_partitionwise_join); /* * We can not perform partitionwise join if either of the joining * relations is not partitioned. */ if (!IS_PARTITIONED_REL(rel1) || !IS_PARTITIONED_REL(rel2)) return; Assert(REL_HAS_ALL_PART_PROPS(rel1) && REL_HAS_ALL_PART_PROPS(rel2)); /* The joining relations should have consider_partitionwise_join set. */ Assert(rel1->consider_partitionwise_join && rel2->consider_partitionwise_join); /* * The partition scheme of the join relation should match that of the * joining relations. */ Assert(joinrel->part_scheme == rel1->part_scheme && joinrel->part_scheme == rel2->part_scheme); Assert(!(joinrel->partbounds_merged && (joinrel->nparts <= 0))); compute_partition_bounds(root, rel1, rel2, joinrel, parent_sjinfo, &parts1, &parts2); if (joinrel->partbounds_merged) { lcr1 = list_head(parts1); lcr2 = list_head(parts2); } /* * Create child-join relations for this partitioned join, if those don't * exist. Add paths to child-joins for a pair of child relations * corresponding to the given pair of parent relations. */ for (cnt_parts = 0; cnt_parts < joinrel->nparts; cnt_parts++) { RelOptInfo *child_rel1; RelOptInfo *child_rel2; bool rel1_empty; bool rel2_empty; SpecialJoinInfo *child_sjinfo; List *child_restrictlist; RelOptInfo *child_joinrel; Relids child_joinrelids; AppendRelInfo **appinfos; int nappinfos; if (joinrel->partbounds_merged) { child_rel1 = lfirst_node(RelOptInfo, lcr1); child_rel2 = lfirst_node(RelOptInfo, lcr2); lcr1 = lnext(parts1, lcr1); lcr2 = lnext(parts2, lcr2); } else { child_rel1 = rel1->part_rels[cnt_parts]; child_rel2 = rel2->part_rels[cnt_parts]; } rel1_empty = (child_rel1 == NULL || IS_DUMMY_REL(child_rel1)); rel2_empty = (child_rel2 == NULL || IS_DUMMY_REL(child_rel2)); /* * Check for cases where we can prove that this segment of the join * returns no rows, due to one or both inputs being empty (including * inputs that have been pruned away entirely). If so just ignore it. * These rules are equivalent to populate_joinrel_with_paths's rules * for dummy input relations. */ switch (parent_sjinfo->jointype) { case JOIN_INNER: case JOIN_SEMI: if (rel1_empty || rel2_empty) continue; /* ignore this join segment */ break; case JOIN_LEFT: case JOIN_ANTI: if (rel1_empty) continue; /* ignore this join segment */ break; case JOIN_FULL: if (rel1_empty && rel2_empty) continue; /* ignore this join segment */ break; default: /* other values not expected here */ elog(ERROR, "unrecognized join type: %d", (int) parent_sjinfo->jointype); break; } /* * If a child has been pruned entirely then we can't generate paths * for it, so we have to reject partitionwise joining unless we were * able to eliminate this partition above. */ if (child_rel1 == NULL || child_rel2 == NULL) { /* * Mark the joinrel as unpartitioned so that later functions treat * it correctly. */ joinrel->nparts = 0; return; } /* * If a leaf relation has consider_partitionwise_join=false, it means * that it's a dummy relation for which we skipped setting up tlist * expressions and adding EC members in set_append_rel_size(), so * again we have to fail here. */ if (rel1_is_simple && !child_rel1->consider_partitionwise_join) { Assert(child_rel1->reloptkind == RELOPT_OTHER_MEMBER_REL); Assert(IS_DUMMY_REL(child_rel1)); joinrel->nparts = 0; return; } if (rel2_is_simple && !child_rel2->consider_partitionwise_join) { Assert(child_rel2->reloptkind == RELOPT_OTHER_MEMBER_REL); Assert(IS_DUMMY_REL(child_rel2)); joinrel->nparts = 0; return; } /* We should never try to join two overlapping sets of rels. */ Assert(!bms_overlap(child_rel1->relids, child_rel2->relids)); child_joinrelids = bms_union(child_rel1->relids, child_rel2->relids); appinfos = find_appinfos_by_relids(root, child_joinrelids, &nappinfos); /* * Construct SpecialJoinInfo from parent join relations's * SpecialJoinInfo. */ child_sjinfo = build_child_join_sjinfo(root, parent_sjinfo, child_rel1->relids, child_rel2->relids); /* * Construct restrictions applicable to the child join from those * applicable to the parent join. */ child_restrictlist = (List *) adjust_appendrel_attrs(root, (Node *) parent_restrictlist, nappinfos, appinfos); pfree(appinfos); child_joinrel = joinrel->part_rels[cnt_parts]; if (!child_joinrel) { child_joinrel = build_child_join_rel(root, child_rel1, child_rel2, joinrel, child_restrictlist, child_sjinfo, child_sjinfo->jointype); joinrel->part_rels[cnt_parts] = child_joinrel; joinrel->all_partrels = bms_add_members(joinrel->all_partrels, child_joinrel->relids); } Assert(bms_equal(child_joinrel->relids, child_joinrelids)); populate_joinrel_with_paths(root, child_rel1, child_rel2, child_joinrel, child_sjinfo, child_restrictlist); } } /* * Construct the SpecialJoinInfo for a child-join by translating * SpecialJoinInfo for the join between parents. left_relids and right_relids * are the relids of left and right side of the join respectively. */ static SpecialJoinInfo * build_child_join_sjinfo(PlannerInfo *root, SpecialJoinInfo *parent_sjinfo, Relids left_relids, Relids right_relids) { SpecialJoinInfo *sjinfo = makeNode(SpecialJoinInfo); AppendRelInfo **left_appinfos; int left_nappinfos; AppendRelInfo **right_appinfos; int right_nappinfos; memcpy(sjinfo, parent_sjinfo, sizeof(SpecialJoinInfo)); left_appinfos = find_appinfos_by_relids(root, left_relids, &left_nappinfos); right_appinfos = find_appinfos_by_relids(root, right_relids, &right_nappinfos); sjinfo->min_lefthand = adjust_child_relids(sjinfo->min_lefthand, left_nappinfos, left_appinfos); sjinfo->min_righthand = adjust_child_relids(sjinfo->min_righthand, right_nappinfos, right_appinfos); sjinfo->syn_lefthand = adjust_child_relids(sjinfo->syn_lefthand, left_nappinfos, left_appinfos); sjinfo->syn_righthand = adjust_child_relids(sjinfo->syn_righthand, right_nappinfos, right_appinfos); sjinfo->semi_rhs_exprs = (List *) adjust_appendrel_attrs(root, (Node *) sjinfo->semi_rhs_exprs, right_nappinfos, right_appinfos); pfree(left_appinfos); pfree(right_appinfos); return sjinfo; } /* * compute_partition_bounds * Compute the partition bounds for a join rel from those for inputs */ static void compute_partition_bounds(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, RelOptInfo *joinrel, SpecialJoinInfo *parent_sjinfo, List **parts1, List **parts2) { /* * If we don't have the partition bounds for the join rel yet, try to * compute those along with pairs of partitions to be joined. */ if (joinrel->nparts == -1) { PartitionScheme part_scheme = joinrel->part_scheme; PartitionBoundInfo boundinfo = NULL; int nparts = 0; Assert(joinrel->boundinfo == NULL); Assert(joinrel->part_rels == NULL); /* * See if the partition bounds for inputs are exactly the same, in * which case we don't need to work hard: the join rel will have the * same partition bounds as inputs, and the partitions with the same * cardinal positions will form the pairs. * * Note: even in cases where one or both inputs have merged bounds, it * would be possible for both the bounds to be exactly the same, but * it seems unlikely to be worth the cycles to check. */ if (!rel1->partbounds_merged && !rel2->partbounds_merged && rel1->nparts == rel2->nparts && partition_bounds_equal(part_scheme->partnatts, part_scheme->parttyplen, part_scheme->parttypbyval, rel1->boundinfo, rel2->boundinfo)) { boundinfo = rel1->boundinfo; nparts = rel1->nparts; } else { /* Try merging the partition bounds for inputs. */ boundinfo = partition_bounds_merge(part_scheme->partnatts, part_scheme->partsupfunc, part_scheme->partcollation, rel1, rel2, parent_sjinfo->jointype, parts1, parts2); if (boundinfo == NULL) { joinrel->nparts = 0; return; } nparts = list_length(*parts1); joinrel->partbounds_merged = true; } Assert(nparts > 0); joinrel->boundinfo = boundinfo; joinrel->nparts = nparts; joinrel->part_rels = (RelOptInfo **) palloc0(sizeof(RelOptInfo *) * nparts); } else { Assert(joinrel->nparts > 0); Assert(joinrel->boundinfo); Assert(joinrel->part_rels); /* * If the join rel's partbounds_merged flag is true, it means inputs * are not guaranteed to have the same partition bounds, therefore we * can't assume that the partitions at the same cardinal positions * form the pairs; let get_matching_part_pairs() generate the pairs. * Otherwise, nothing to do since we can assume that. */ if (joinrel->partbounds_merged) { get_matching_part_pairs(root, joinrel, rel1, rel2, parts1, parts2); Assert(list_length(*parts1) == joinrel->nparts); Assert(list_length(*parts2) == joinrel->nparts); } } } /* * get_matching_part_pairs * Generate pairs of partitions to be joined from inputs */ static void get_matching_part_pairs(PlannerInfo *root, RelOptInfo *joinrel, RelOptInfo *rel1, RelOptInfo *rel2, List **parts1, List **parts2) { bool rel1_is_simple = IS_SIMPLE_REL(rel1); bool rel2_is_simple = IS_SIMPLE_REL(rel2); int cnt_parts; *parts1 = NIL; *parts2 = NIL; for (cnt_parts = 0; cnt_parts < joinrel->nparts; cnt_parts++) { RelOptInfo *child_joinrel = joinrel->part_rels[cnt_parts]; RelOptInfo *child_rel1; RelOptInfo *child_rel2; Relids child_relids1; Relids child_relids2; /* * If this segment of the join is empty, it means that this segment * was ignored when previously creating child-join paths for it in * try_partitionwise_join() as it would not contribute to the join * result, due to one or both inputs being empty; add NULL to each of * the given lists so that this segment will be ignored again in that * function. */ if (!child_joinrel) { *parts1 = lappend(*parts1, NULL); *parts2 = lappend(*parts2, NULL); continue; } /* * Get a relids set of partition(s) involved in this join segment that * are from the rel1 side. */ child_relids1 = bms_intersect(child_joinrel->relids, rel1->all_partrels); Assert(bms_num_members(child_relids1) == bms_num_members(rel1->relids)); /* * Get a child rel for rel1 with the relids. Note that we should have * the child rel even if rel1 is a join rel, because in that case the * partitions specified in the relids would have matching/overlapping * boundaries, so the specified partitions should be considered as * ones to be joined when planning partitionwise joins of rel1, * meaning that the child rel would have been built by the time we get * here. */ if (rel1_is_simple) { int varno = bms_singleton_member(child_relids1); child_rel1 = find_base_rel(root, varno); } else child_rel1 = find_join_rel(root, child_relids1); Assert(child_rel1); /* * Get a relids set of partition(s) involved in this join segment that * are from the rel2 side. */ child_relids2 = bms_intersect(child_joinrel->relids, rel2->all_partrels); Assert(bms_num_members(child_relids2) == bms_num_members(rel2->relids)); /* * Get a child rel for rel2 with the relids. See above comments. */ if (rel2_is_simple) { int varno = bms_singleton_member(child_relids2); child_rel2 = find_base_rel(root, varno); } else child_rel2 = find_join_rel(root, child_relids2); Assert(child_rel2); /* * The join of rel1 and rel2 is legal, so is the join of the child * rels obtained above; add them to the given lists as a join pair * producing this join segment. */ *parts1 = lappend(*parts1, child_rel1); *parts2 = lappend(*parts2, child_rel2); } }