1583 lines
51 KiB
C
1583 lines
51 KiB
C
/*-------------------------------------------------------------------------
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*
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* joinrels.c
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* Routines to determine which relations should be joined
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*
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* Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* src/backend/optimizer/path/joinrels.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "miscadmin.h"
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#include "catalog/partition.h"
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#include "nodes/relation.h"
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#include "optimizer/clauses.h"
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#include "optimizer/joininfo.h"
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#include "optimizer/pathnode.h"
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#include "optimizer/paths.h"
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#include "optimizer/prep.h"
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#include "optimizer/cost.h"
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#include "utils/memutils.h"
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#include "utils/lsyscache.h"
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static void make_rels_by_clause_joins(PlannerInfo *root,
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RelOptInfo *old_rel,
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ListCell *other_rels);
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static void make_rels_by_clauseless_joins(PlannerInfo *root,
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RelOptInfo *old_rel,
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ListCell *other_rels);
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static bool has_join_restriction(PlannerInfo *root, RelOptInfo *rel);
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static bool has_legal_joinclause(PlannerInfo *root, RelOptInfo *rel);
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static bool is_dummy_rel(RelOptInfo *rel);
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static bool restriction_is_constant_false(List *restrictlist,
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bool only_pushed_down);
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static void populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
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RelOptInfo *rel2, RelOptInfo *joinrel,
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SpecialJoinInfo *sjinfo, List *restrictlist);
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static void try_partition_wise_join(PlannerInfo *root, RelOptInfo *rel1,
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RelOptInfo *rel2, RelOptInfo *joinrel,
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SpecialJoinInfo *parent_sjinfo,
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List *parent_restrictlist);
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static int match_expr_to_partition_keys(Expr *expr, RelOptInfo *rel,
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bool strict_op);
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/*
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* join_search_one_level
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* Consider ways to produce join relations containing exactly 'level'
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* jointree items. (This is one step of the dynamic-programming method
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* embodied in standard_join_search.) Join rel nodes for each feasible
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* combination of lower-level rels are created and returned in a list.
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* Implementation paths are created for each such joinrel, too.
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*
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* level: level of rels we want to make this time
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* root->join_rel_level[j], 1 <= j < level, is a list of rels containing j items
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*
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* The result is returned in root->join_rel_level[level].
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*/
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void
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join_search_one_level(PlannerInfo *root, int level)
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{
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List **joinrels = root->join_rel_level;
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ListCell *r;
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int k;
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Assert(joinrels[level] == NIL);
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/* Set join_cur_level so that new joinrels are added to proper list */
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root->join_cur_level = level;
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/*
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* First, consider left-sided and right-sided plans, in which rels of
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* exactly level-1 member relations are joined against initial relations.
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* We prefer to join using join clauses, but if we find a rel of level-1
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* members that has no join clauses, we will generate Cartesian-product
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* joins against all initial rels not already contained in it.
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*/
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foreach(r, joinrels[level - 1])
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{
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RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
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if (old_rel->joininfo != NIL || old_rel->has_eclass_joins ||
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has_join_restriction(root, old_rel))
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{
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/*
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* There are join clauses or join order restrictions relevant to
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* this rel, so consider joins between this rel and (only) those
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* initial rels it is linked to by a clause or restriction.
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*
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* At level 2 this condition is symmetric, so there is no need to
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* look at initial rels before this one in the list; we already
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* considered such joins when we were at the earlier rel. (The
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* mirror-image joins are handled automatically by make_join_rel.)
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* In later passes (level > 2), we join rels of the previous level
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* to each initial rel they don't already include but have a join
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* clause or restriction with.
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*/
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ListCell *other_rels;
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if (level == 2) /* consider remaining initial rels */
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other_rels = lnext(r);
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else /* consider all initial rels */
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other_rels = list_head(joinrels[1]);
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make_rels_by_clause_joins(root,
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old_rel,
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other_rels);
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}
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else
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{
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/*
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* Oops, we have a relation that is not joined to any other
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* relation, either directly or by join-order restrictions.
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* Cartesian product time.
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*
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* We consider a cartesian product with each not-already-included
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* initial rel, whether it has other join clauses or not. At
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* level 2, if there are two or more clauseless initial rels, we
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* will redundantly consider joining them in both directions; but
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* such cases aren't common enough to justify adding complexity to
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* avoid the duplicated effort.
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*/
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make_rels_by_clauseless_joins(root,
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old_rel,
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list_head(joinrels[1]));
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}
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}
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/*
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* Now, consider "bushy plans" in which relations of k initial rels are
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* joined to relations of level-k initial rels, for 2 <= k <= level-2.
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*
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* We only consider bushy-plan joins for pairs of rels where there is a
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* suitable join clause (or join order restriction), in order to avoid
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* unreasonable growth of planning time.
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*/
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for (k = 2;; k++)
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{
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int other_level = level - k;
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/*
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* Since make_join_rel(x, y) handles both x,y and y,x cases, we only
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* need to go as far as the halfway point.
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*/
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if (k > other_level)
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break;
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foreach(r, joinrels[k])
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{
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RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
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ListCell *other_rels;
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ListCell *r2;
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/*
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* We can ignore relations without join clauses here, unless they
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* participate in join-order restrictions --- then we might have
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* to force a bushy join plan.
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*/
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if (old_rel->joininfo == NIL && !old_rel->has_eclass_joins &&
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!has_join_restriction(root, old_rel))
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continue;
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if (k == other_level)
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other_rels = lnext(r); /* only consider remaining rels */
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else
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other_rels = list_head(joinrels[other_level]);
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for_each_cell(r2, other_rels)
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{
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RelOptInfo *new_rel = (RelOptInfo *) lfirst(r2);
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if (!bms_overlap(old_rel->relids, new_rel->relids))
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{
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/*
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* OK, we can build a rel of the right level from this
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* pair of rels. Do so if there is at least one relevant
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* join clause or join order restriction.
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*/
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if (have_relevant_joinclause(root, old_rel, new_rel) ||
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have_join_order_restriction(root, old_rel, new_rel))
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{
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(void) make_join_rel(root, old_rel, new_rel);
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}
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}
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}
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}
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}
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/*----------
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* Last-ditch effort: if we failed to find any usable joins so far, force
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* a set of cartesian-product joins to be generated. This handles the
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* special case where all the available rels have join clauses but we
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* cannot use any of those clauses yet. This can only happen when we are
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* considering a join sub-problem (a sub-joinlist) and all the rels in the
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* sub-problem have only join clauses with rels outside the sub-problem.
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* An example is
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*
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* SELECT ... FROM a INNER JOIN b ON TRUE, c, d, ...
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* WHERE a.w = c.x and b.y = d.z;
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*
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* If the "a INNER JOIN b" sub-problem does not get flattened into the
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* upper level, we must be willing to make a cartesian join of a and b;
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* but the code above will not have done so, because it thought that both
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* a and b have joinclauses. We consider only left-sided and right-sided
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* cartesian joins in this case (no bushy).
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*----------
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*/
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if (joinrels[level] == NIL)
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{
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/*
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* This loop is just like the first one, except we always call
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* make_rels_by_clauseless_joins().
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*/
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foreach(r, joinrels[level - 1])
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{
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RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
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make_rels_by_clauseless_joins(root,
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old_rel,
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list_head(joinrels[1]));
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}
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/*----------
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* When special joins are involved, there may be no legal way
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* to make an N-way join for some values of N. For example consider
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*
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* SELECT ... FROM t1 WHERE
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* x IN (SELECT ... FROM t2,t3 WHERE ...) AND
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* y IN (SELECT ... FROM t4,t5 WHERE ...)
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*
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* We will flatten this query to a 5-way join problem, but there are
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* no 4-way joins that join_is_legal() will consider legal. We have
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* to accept failure at level 4 and go on to discover a workable
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* bushy plan at level 5.
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*
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* However, if there are no special joins and no lateral references
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* then join_is_legal() should never fail, and so the following sanity
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* check is useful.
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*----------
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*/
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if (joinrels[level] == NIL &&
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root->join_info_list == NIL &&
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!root->hasLateralRTEs)
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elog(ERROR, "failed to build any %d-way joins", level);
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}
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}
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/*
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* make_rels_by_clause_joins
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* Build joins between the given relation 'old_rel' and other relations
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* that participate in join clauses that 'old_rel' also participates in
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* (or participate in join-order restrictions with it).
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* The join rels are returned in root->join_rel_level[join_cur_level].
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*
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* Note: at levels above 2 we will generate the same joined relation in
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* multiple ways --- for example (a join b) join c is the same RelOptInfo as
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* (b join c) join a, though the second case will add a different set of Paths
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* to it. This is the reason for using the join_rel_level mechanism, which
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* automatically ensures that each new joinrel is only added to the list once.
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*
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* 'old_rel' is the relation entry for the relation to be joined
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* 'other_rels': the first cell in a linked list containing the other
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* rels to be considered for joining
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*
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* Currently, this is only used with initial rels in other_rels, but it
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* will work for joining to joinrels too.
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*/
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static void
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make_rels_by_clause_joins(PlannerInfo *root,
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RelOptInfo *old_rel,
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ListCell *other_rels)
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{
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ListCell *l;
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for_each_cell(l, other_rels)
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{
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RelOptInfo *other_rel = (RelOptInfo *) lfirst(l);
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if (!bms_overlap(old_rel->relids, other_rel->relids) &&
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(have_relevant_joinclause(root, old_rel, other_rel) ||
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have_join_order_restriction(root, old_rel, other_rel)))
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{
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(void) make_join_rel(root, old_rel, other_rel);
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}
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}
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}
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/*
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* make_rels_by_clauseless_joins
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* Given a relation 'old_rel' and a list of other relations
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* 'other_rels', create a join relation between 'old_rel' and each
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* member of 'other_rels' that isn't already included in 'old_rel'.
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* The join rels are returned in root->join_rel_level[join_cur_level].
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*
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* 'old_rel' is the relation entry for the relation to be joined
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* 'other_rels': the first cell of a linked list containing the
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* other rels to be considered for joining
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*
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* Currently, this is only used with initial rels in other_rels, but it would
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* work for joining to joinrels too.
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*/
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static void
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make_rels_by_clauseless_joins(PlannerInfo *root,
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RelOptInfo *old_rel,
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ListCell *other_rels)
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{
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ListCell *l;
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for_each_cell(l, other_rels)
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{
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RelOptInfo *other_rel = (RelOptInfo *) lfirst(l);
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if (!bms_overlap(other_rel->relids, old_rel->relids))
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{
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(void) make_join_rel(root, old_rel, other_rel);
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}
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}
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}
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/*
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* join_is_legal
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* Determine whether a proposed join is legal given the query's
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* join order constraints; and if it is, determine the join type.
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*
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* Caller must supply not only the two rels, but the union of their relids.
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* (We could simplify the API by computing joinrelids locally, but this
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* would be redundant work in the normal path through make_join_rel.)
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*
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* On success, *sjinfo_p is set to NULL if this is to be a plain inner join,
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* else it's set to point to the associated SpecialJoinInfo node. Also,
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* *reversed_p is set TRUE if the given relations need to be swapped to
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* match the SpecialJoinInfo node.
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*/
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static bool
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join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
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Relids joinrelids,
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SpecialJoinInfo **sjinfo_p, bool *reversed_p)
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{
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SpecialJoinInfo *match_sjinfo;
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bool reversed;
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bool unique_ified;
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bool must_be_leftjoin;
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ListCell *l;
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/*
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* Ensure output params are set on failure return. This is just to
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* suppress uninitialized-variable warnings from overly anal compilers.
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*/
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*sjinfo_p = NULL;
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*reversed_p = false;
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/*
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* If we have any special joins, the proposed join might be illegal; and
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* in any case we have to determine its join type. Scan the join info
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* list for matches and conflicts.
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*/
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match_sjinfo = NULL;
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reversed = false;
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unique_ified = false;
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must_be_leftjoin = false;
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foreach(l, root->join_info_list)
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{
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SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);
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/*
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* This special join is not relevant unless its RHS overlaps the
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* proposed join. (Check this first as a fast path for dismissing
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* most irrelevant SJs quickly.)
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*/
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if (!bms_overlap(sjinfo->min_righthand, joinrelids))
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continue;
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/*
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* Also, not relevant if proposed join is fully contained within RHS
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* (ie, we're still building up the RHS).
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*/
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if (bms_is_subset(joinrelids, sjinfo->min_righthand))
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continue;
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/*
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* Also, not relevant if SJ is already done within either input.
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*/
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if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
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bms_is_subset(sjinfo->min_righthand, rel1->relids))
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continue;
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if (bms_is_subset(sjinfo->min_lefthand, rel2->relids) &&
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bms_is_subset(sjinfo->min_righthand, rel2->relids))
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continue;
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/*
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* If it's a semijoin and we already joined the RHS to any other rels
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* within either input, then we must have unique-ified the RHS at that
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* point (see below). Therefore the semijoin is no longer relevant in
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* this join path.
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*/
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if (sjinfo->jointype == JOIN_SEMI)
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{
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if (bms_is_subset(sjinfo->syn_righthand, rel1->relids) &&
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!bms_equal(sjinfo->syn_righthand, rel1->relids))
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continue;
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if (bms_is_subset(sjinfo->syn_righthand, rel2->relids) &&
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!bms_equal(sjinfo->syn_righthand, rel2->relids))
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continue;
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}
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/*
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* If one input contains min_lefthand and the other contains
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* min_righthand, then we can perform the SJ at this join.
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*
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* Reject if we get matches to more than one SJ; that implies we're
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* considering something that's not really valid.
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*/
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if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
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bms_is_subset(sjinfo->min_righthand, rel2->relids))
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{
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if (match_sjinfo)
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return false; /* invalid join path */
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match_sjinfo = sjinfo;
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reversed = false;
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}
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else if (bms_is_subset(sjinfo->min_lefthand, rel2->relids) &&
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bms_is_subset(sjinfo->min_righthand, rel1->relids))
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{
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if (match_sjinfo)
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return false; /* invalid join path */
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match_sjinfo = sjinfo;
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reversed = true;
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}
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else if (sjinfo->jointype == JOIN_SEMI &&
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bms_equal(sjinfo->syn_righthand, rel2->relids) &&
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create_unique_path(root, rel2, rel2->cheapest_total_path,
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sjinfo) != NULL)
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{
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/*----------
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* For a semijoin, we can join the RHS to anything else by
|
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* unique-ifying the RHS (if the RHS can be unique-ified).
|
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* We will only get here if we have the full RHS but less
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* than min_lefthand on the LHS.
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*
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* The reason to consider such a join path is exemplified by
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* SELECT ... FROM a,b WHERE (a.x,b.y) IN (SELECT c1,c2 FROM c)
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* If we insist on doing this as a semijoin we will first have
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* to form the cartesian product of A*B. But if we unique-ify
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* C then the semijoin becomes a plain innerjoin and we can join
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* in any order, eg C to A and then to B. When C is much smaller
|
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* than A and B this can be a huge win. So we allow C to be
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* joined to just A or just B here, and then make_join_rel has
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* to handle the case properly.
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*
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* Note that actually we'll allow unique-ified C to be joined to
|
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* some other relation D here, too. That is legal, if usually not
|
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* very sane, and this routine is only concerned with legality not
|
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* with whether the join is good strategy.
|
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*----------
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*/
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if (match_sjinfo)
|
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return false; /* invalid join path */
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match_sjinfo = sjinfo;
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reversed = false;
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unique_ified = true;
|
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}
|
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else if (sjinfo->jointype == JOIN_SEMI &&
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bms_equal(sjinfo->syn_righthand, rel1->relids) &&
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create_unique_path(root, rel1, rel1->cheapest_total_path,
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sjinfo) != NULL)
|
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{
|
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/* Reversed semijoin case */
|
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if (match_sjinfo)
|
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return false; /* invalid join path */
|
|
match_sjinfo = sjinfo;
|
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reversed = true;
|
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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);
|
|
|
|
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;
|
|
}
|
|
/* full joins constrain both sides symmetrically */
|
|
if (sjinfo->jointype == JOIN_FULL &&
|
|
bms_overlap(sjinfo->min_righthand, join_plus_rhs) &&
|
|
!bms_is_subset(sjinfo->min_lefthand, join_plus_rhs))
|
|
{
|
|
join_plus_rhs = bms_add_members(join_plus_rhs,
|
|
sjinfo->min_lefthand);
|
|
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, 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, true))
|
|
{
|
|
mark_dummy_rel(joinrel);
|
|
break;
|
|
}
|
|
if (restriction_is_constant_false(restrictlist, 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, 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, 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, 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, true))
|
|
{
|
|
mark_dummy_rel(joinrel);
|
|
break;
|
|
}
|
|
if (restriction_is_constant_false(restrictlist, 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 partition-wise join technique, if possible. */
|
|
try_partition_wise_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?
|
|
*/
|
|
static bool
|
|
is_dummy_rel(RelOptInfo *rel)
|
|
{
|
|
return IS_DUMMY_REL(rel);
|
|
}
|
|
|
|
/*
|
|
* 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(rel, NIL, NULL, 0, NIL));
|
|
|
|
/* 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 pushed-down quals.
|
|
*/
|
|
static bool
|
|
restriction_is_constant_false(List *restrictlist, 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)
|
|
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
|
|
* "partition-wise join"
|
|
*
|
|
* Partition-wise 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.
|
|
*
|
|
* Partition-wise 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_partition_wise_join_paths().
|
|
*
|
|
* The RelOptInfo, SpecialJoinInfo and restrictlist for each child join are
|
|
* obtained by translating the respective parent join structures.
|
|
*/
|
|
static void
|
|
try_partition_wise_join(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
|
|
RelOptInfo *joinrel, SpecialJoinInfo *parent_sjinfo,
|
|
List *parent_restrictlist)
|
|
{
|
|
int nparts;
|
|
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 (!IS_PARTITIONED_REL(joinrel))
|
|
return;
|
|
|
|
/*
|
|
* set_rel_pathlist() may not create paths in children of an empty
|
|
* partitioned table and so we can not add paths to child-joins. So, deem
|
|
* such a join as unpartitioned. When a partitioned relation is deemed
|
|
* empty because all its children are empty, dummy path will be set in
|
|
* each of the children. In such a case we could still consider the join
|
|
* as partitioned, but it might not help much.
|
|
*/
|
|
if (IS_DUMMY_REL(rel1) || IS_DUMMY_REL(rel2))
|
|
return;
|
|
|
|
/*
|
|
* Since this join relation is partitioned, all the base relations
|
|
* participating in this join must be partitioned and so are all the
|
|
* intermediate join relations.
|
|
*/
|
|
Assert(IS_PARTITIONED_REL(rel1) && IS_PARTITIONED_REL(rel2));
|
|
Assert(REL_HAS_ALL_PART_PROPS(rel1) && REL_HAS_ALL_PART_PROPS(rel2));
|
|
|
|
/*
|
|
* 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);
|
|
|
|
/*
|
|
* Since we allow partition-wise join only when the partition bounds of
|
|
* the joining relations exactly match, the partition bounds of the join
|
|
* should match those of the joining relations.
|
|
*/
|
|
Assert(partition_bounds_equal(joinrel->part_scheme->partnatts,
|
|
joinrel->part_scheme->parttyplen,
|
|
joinrel->part_scheme->parttypbyval,
|
|
joinrel->boundinfo, rel1->boundinfo));
|
|
Assert(partition_bounds_equal(joinrel->part_scheme->partnatts,
|
|
joinrel->part_scheme->parttyplen,
|
|
joinrel->part_scheme->parttypbyval,
|
|
joinrel->boundinfo, rel2->boundinfo));
|
|
|
|
nparts = joinrel->nparts;
|
|
|
|
/* Allocate space to hold child-joins RelOptInfos, if not already done. */
|
|
if (!joinrel->part_rels)
|
|
joinrel->part_rels =
|
|
(RelOptInfo **) palloc0(sizeof(RelOptInfo *) * nparts);
|
|
|
|
/*
|
|
* 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 < nparts; cnt_parts++)
|
|
{
|
|
RelOptInfo *child_rel1 = rel1->part_rels[cnt_parts];
|
|
RelOptInfo *child_rel2 = rel2->part_rels[cnt_parts];
|
|
SpecialJoinInfo *child_sjinfo;
|
|
List *child_restrictlist;
|
|
RelOptInfo *child_joinrel;
|
|
Relids child_joinrelids;
|
|
AppendRelInfo **appinfos;
|
|
int nappinfos;
|
|
|
|
/* 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;
|
|
}
|
|
|
|
Assert(bms_equal(child_joinrel->relids, child_joinrelids));
|
|
|
|
populate_joinrel_with_paths(root, child_rel1, child_rel2,
|
|
child_joinrel, child_sjinfo,
|
|
child_restrictlist);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Returns true if there exists an equi-join condition for each pair of
|
|
* partition keys from given relations being joined.
|
|
*/
|
|
bool
|
|
have_partkey_equi_join(RelOptInfo *rel1, RelOptInfo *rel2, JoinType jointype,
|
|
List *restrictlist)
|
|
{
|
|
PartitionScheme part_scheme = rel1->part_scheme;
|
|
ListCell *lc;
|
|
int cnt_pks;
|
|
bool pk_has_clause[PARTITION_MAX_KEYS];
|
|
bool strict_op;
|
|
|
|
/*
|
|
* This function should be called when the joining relations have same
|
|
* partitioning scheme.
|
|
*/
|
|
Assert(rel1->part_scheme == rel2->part_scheme);
|
|
Assert(part_scheme);
|
|
|
|
memset(pk_has_clause, 0, sizeof(pk_has_clause));
|
|
foreach(lc, restrictlist)
|
|
{
|
|
RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
|
|
OpExpr *opexpr;
|
|
Expr *expr1;
|
|
Expr *expr2;
|
|
int ipk1;
|
|
int ipk2;
|
|
|
|
/* If processing an outer join, only use its own join clauses. */
|
|
if (IS_OUTER_JOIN(jointype) && rinfo->is_pushed_down)
|
|
continue;
|
|
|
|
/* Skip clauses which can not be used for a join. */
|
|
if (!rinfo->can_join)
|
|
continue;
|
|
|
|
/* Skip clauses which are not equality conditions. */
|
|
if (!rinfo->mergeopfamilies)
|
|
continue;
|
|
|
|
opexpr = (OpExpr *) rinfo->clause;
|
|
Assert(is_opclause(opexpr));
|
|
|
|
/*
|
|
* The equi-join between partition keys is strict if equi-join between
|
|
* at least one partition key is using a strict operator. See
|
|
* explanation about outer join reordering identity 3 in
|
|
* optimizer/README
|
|
*/
|
|
strict_op = op_strict(opexpr->opno);
|
|
|
|
/* Match the operands to the relation. */
|
|
if (bms_is_subset(rinfo->left_relids, rel1->relids) &&
|
|
bms_is_subset(rinfo->right_relids, rel2->relids))
|
|
{
|
|
expr1 = linitial(opexpr->args);
|
|
expr2 = lsecond(opexpr->args);
|
|
}
|
|
else if (bms_is_subset(rinfo->left_relids, rel2->relids) &&
|
|
bms_is_subset(rinfo->right_relids, rel1->relids))
|
|
{
|
|
expr1 = lsecond(opexpr->args);
|
|
expr2 = linitial(opexpr->args);
|
|
}
|
|
else
|
|
continue;
|
|
|
|
/*
|
|
* Only clauses referencing the partition keys are useful for
|
|
* partition-wise join.
|
|
*/
|
|
ipk1 = match_expr_to_partition_keys(expr1, rel1, strict_op);
|
|
if (ipk1 < 0)
|
|
continue;
|
|
ipk2 = match_expr_to_partition_keys(expr2, rel2, strict_op);
|
|
if (ipk2 < 0)
|
|
continue;
|
|
|
|
/*
|
|
* If the clause refers to keys at different ordinal positions, it can
|
|
* not be used for partition-wise join.
|
|
*/
|
|
if (ipk1 != ipk2)
|
|
continue;
|
|
|
|
/*
|
|
* The clause allows partition-wise join if only it uses the same
|
|
* operator family as that specified by the partition key.
|
|
*/
|
|
if (!list_member_oid(rinfo->mergeopfamilies,
|
|
part_scheme->partopfamily[ipk1]))
|
|
continue;
|
|
|
|
/* Mark the partition key as having an equi-join clause. */
|
|
pk_has_clause[ipk1] = true;
|
|
}
|
|
|
|
/* Check whether every partition key has an equi-join condition. */
|
|
for (cnt_pks = 0; cnt_pks < part_scheme->partnatts; cnt_pks++)
|
|
{
|
|
if (!pk_has_clause[cnt_pks])
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* Find the partition key from the given relation matching the given
|
|
* expression. If found, return the index of the partition key, else return -1.
|
|
*/
|
|
static int
|
|
match_expr_to_partition_keys(Expr *expr, RelOptInfo *rel, bool strict_op)
|
|
{
|
|
int cnt;
|
|
|
|
/* This function should be called only for partitioned relations. */
|
|
Assert(rel->part_scheme);
|
|
|
|
/* Remove any relabel decorations. */
|
|
while (IsA(expr, RelabelType))
|
|
expr = (Expr *) (castNode(RelabelType, expr))->arg;
|
|
|
|
for (cnt = 0; cnt < rel->part_scheme->partnatts; cnt++)
|
|
{
|
|
ListCell *lc;
|
|
|
|
Assert(rel->partexprs);
|
|
foreach(lc, rel->partexprs[cnt])
|
|
{
|
|
if (equal(lfirst(lc), expr))
|
|
return cnt;
|
|
}
|
|
|
|
if (!strict_op)
|
|
continue;
|
|
|
|
/*
|
|
* If it's a strict equi-join a NULL partition key on one side will
|
|
* not join a NULL partition key on the other side. So, rows with NULL
|
|
* partition key from a partition on one side can not join with those
|
|
* from a non-matching partition on the other side. So, search the
|
|
* nullable partition keys as well.
|
|
*/
|
|
Assert(rel->nullable_partexprs);
|
|
foreach(lc, rel->nullable_partexprs[cnt])
|
|
{
|
|
if (equal(lfirst(lc), expr))
|
|
return cnt;
|
|
}
|
|
}
|
|
|
|
return -1;
|
|
}
|