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244f649261
the cheapest-total inner path as a new candidate while truncating the sort key list, if it already matched the full sort key list. This is too much of a corner case to be worth back-patching, since it's unusual for the cheapest total path to be sorted, and anyway no real harm is done (except in JOIN_SEMI/ANTI cases where cost_mergejoin is a bit broken at the moment). But it wasn't behaving as intended, so fix it. Noted while examining a test case from Kevin Grittner. This error doesn't explain his issue, but it does explain why "set enable_seqscan = off" seemed to reproduce it for me.
1072 lines
34 KiB
C
1072 lines
34 KiB
C
/*-------------------------------------------------------------------------
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*
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* joinpath.c
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* Routines to find all possible paths for processing a set of joins
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*
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* Portions Copyright (c) 1996-2009, 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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* $PostgreSQL: pgsql/src/backend/optimizer/path/joinpath.c,v 1.121 2009/02/05 01:24:55 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include <math.h>
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#include "optimizer/cost.h"
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#include "optimizer/pathnode.h"
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#include "optimizer/paths.h"
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static void sort_inner_and_outer(PlannerInfo *root, RelOptInfo *joinrel,
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RelOptInfo *outerrel, RelOptInfo *innerrel,
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List *restrictlist, List *mergeclause_list,
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JoinType jointype, SpecialJoinInfo *sjinfo);
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static void match_unsorted_outer(PlannerInfo *root, RelOptInfo *joinrel,
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RelOptInfo *outerrel, RelOptInfo *innerrel,
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List *restrictlist, List *mergeclause_list,
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JoinType jointype, SpecialJoinInfo *sjinfo);
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static void hash_inner_and_outer(PlannerInfo *root, RelOptInfo *joinrel,
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RelOptInfo *outerrel, RelOptInfo *innerrel,
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List *restrictlist,
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JoinType jointype, SpecialJoinInfo *sjinfo);
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static Path *best_appendrel_indexscan(PlannerInfo *root, RelOptInfo *rel,
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RelOptInfo *outer_rel, JoinType jointype);
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static List *select_mergejoin_clauses(PlannerInfo *root,
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RelOptInfo *joinrel,
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RelOptInfo *outerrel,
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RelOptInfo *innerrel,
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List *restrictlist,
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JoinType jointype);
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/*
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* add_paths_to_joinrel
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* Given a join relation and two component rels from which it can be made,
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* consider all possible paths that use the two component rels as outer
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* and inner rel respectively. Add these paths to the join rel's pathlist
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* if they survive comparison with other paths (and remove any existing
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* paths that are dominated by these paths).
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*
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* Modifies the pathlist field of the joinrel node to contain the best
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* paths found so far.
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*
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* jointype is not necessarily the same as sjinfo->jointype; it might be
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* "flipped around" if we are considering joining the rels in the opposite
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* direction from what's indicated in sjinfo.
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*
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* Also, this routine and others in this module accept the special JoinTypes
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* JOIN_UNIQUE_OUTER and JOIN_UNIQUE_INNER to indicate that we should
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* unique-ify the outer or inner relation and then apply a regular inner
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* join. These values are not allowed to propagate outside this module,
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* however. Path cost estimation code may need to recognize that it's
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* dealing with such a case --- the combination of nominal jointype INNER
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* with sjinfo->jointype == JOIN_SEMI indicates that.
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*/
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void
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add_paths_to_joinrel(PlannerInfo *root,
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RelOptInfo *joinrel,
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RelOptInfo *outerrel,
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RelOptInfo *innerrel,
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JoinType jointype,
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SpecialJoinInfo *sjinfo,
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List *restrictlist)
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{
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List *mergeclause_list = NIL;
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/*
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* Find potential mergejoin clauses. We can skip this if we are not
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* interested in doing a mergejoin. However, mergejoin is currently our
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* only way of implementing full outer joins, so override mergejoin
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* disable if it's a full join.
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*/
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if (enable_mergejoin || jointype == JOIN_FULL)
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mergeclause_list = select_mergejoin_clauses(root,
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joinrel,
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outerrel,
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innerrel,
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restrictlist,
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jointype);
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/*
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* 1. Consider mergejoin paths where both relations must be explicitly
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* sorted.
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*/
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sort_inner_and_outer(root, joinrel, outerrel, innerrel,
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restrictlist, mergeclause_list, jointype, sjinfo);
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/*
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* 2. Consider paths where the outer relation need not be explicitly
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* sorted. This includes both nestloops and mergejoins where the outer
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* path is already ordered.
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*/
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match_unsorted_outer(root, joinrel, outerrel, innerrel,
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restrictlist, mergeclause_list, jointype, sjinfo);
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#ifdef NOT_USED
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/*
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* 3. Consider paths where the inner relation need not be explicitly
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* sorted. This includes mergejoins only (nestloops were already built in
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* match_unsorted_outer).
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*
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* Diked out as redundant 2/13/2000 -- tgl. There isn't any really
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* significant difference between the inner and outer side of a mergejoin,
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* so match_unsorted_inner creates no paths that aren't equivalent to
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* those made by match_unsorted_outer when add_paths_to_joinrel() is
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* invoked with the two rels given in the other order.
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*/
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match_unsorted_inner(root, joinrel, outerrel, innerrel,
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restrictlist, mergeclause_list, jointype, sjinfo);
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#endif
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/*
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* 4. Consider paths where both outer and inner relations must be hashed
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* before being joined.
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*/
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if (enable_hashjoin)
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hash_inner_and_outer(root, joinrel, outerrel, innerrel,
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restrictlist, jointype, sjinfo);
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}
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/*
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* sort_inner_and_outer
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* Create mergejoin join paths by explicitly sorting both the outer and
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* inner join relations on each available merge ordering.
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*
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* 'joinrel' is the join relation
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* 'outerrel' is the outer join relation
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* 'innerrel' is the inner join relation
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* 'restrictlist' contains all of the RestrictInfo nodes for restriction
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* clauses that apply to this join
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* 'mergeclause_list' is a list of RestrictInfo nodes for available
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* mergejoin clauses in this join
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* 'jointype' is the type of join to do
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* 'sjinfo' is extra info about the join for selectivity estimation
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*/
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static void
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sort_inner_and_outer(PlannerInfo *root,
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RelOptInfo *joinrel,
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RelOptInfo *outerrel,
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RelOptInfo *innerrel,
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List *restrictlist,
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List *mergeclause_list,
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JoinType jointype,
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SpecialJoinInfo *sjinfo)
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{
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bool useallclauses;
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Path *outer_path;
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Path *inner_path;
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List *all_pathkeys;
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ListCell *l;
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/*
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* If we are doing a right or full join, we must use *all* the
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* mergeclauses as join clauses, else we will not have a valid plan.
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*/
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switch (jointype)
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{
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case JOIN_INNER:
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case JOIN_LEFT:
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case JOIN_SEMI:
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case JOIN_ANTI:
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case JOIN_UNIQUE_OUTER:
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case JOIN_UNIQUE_INNER:
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useallclauses = false;
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break;
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case JOIN_RIGHT:
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case JOIN_FULL:
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useallclauses = true;
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break;
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default:
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elog(ERROR, "unrecognized join type: %d",
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(int) jointype);
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useallclauses = false; /* keep compiler quiet */
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break;
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}
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/*
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* We only consider the cheapest-total-cost input paths, since we are
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* assuming here that a sort is required. We will consider
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* cheapest-startup-cost input paths later, and only if they don't need a
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* sort.
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*
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* If unique-ification is requested, do it and then handle as a plain
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* inner join.
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*/
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outer_path = outerrel->cheapest_total_path;
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inner_path = innerrel->cheapest_total_path;
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if (jointype == JOIN_UNIQUE_OUTER)
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{
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outer_path = (Path *) create_unique_path(root, outerrel,
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outer_path, sjinfo);
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Assert(outer_path);
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jointype = JOIN_INNER;
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}
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else if (jointype == JOIN_UNIQUE_INNER)
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{
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inner_path = (Path *) create_unique_path(root, innerrel,
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inner_path, sjinfo);
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Assert(inner_path);
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jointype = JOIN_INNER;
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}
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/*
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* Each possible ordering of the available mergejoin clauses will generate
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* a differently-sorted result path at essentially the same cost. We have
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* no basis for choosing one over another at this level of joining, but
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* some sort orders may be more useful than others for higher-level
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* mergejoins, so it's worth considering multiple orderings.
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*
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* Actually, it's not quite true that every mergeclause ordering will
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* generate a different path order, because some of the clauses may be
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* partially redundant (refer to the same EquivalenceClasses). Therefore,
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* what we do is convert the mergeclause list to a list of canonical
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* pathkeys, and then consider different orderings of the pathkeys.
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*
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* Generating a path for *every* permutation of the pathkeys doesn't seem
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* like a winning strategy; the cost in planning time is too high. For
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* now, we generate one path for each pathkey, listing that pathkey first
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* and the rest in random order. This should allow at least a one-clause
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* mergejoin without re-sorting against any other possible mergejoin
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* partner path. But if we've not guessed the right ordering of secondary
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* keys, we may end up evaluating clauses as qpquals when they could have
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* been done as mergeclauses. (In practice, it's rare that there's more
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* than two or three mergeclauses, so expending a huge amount of thought
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* on that is probably not worth it.)
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*
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* The pathkey order returned by select_outer_pathkeys_for_merge() has
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* some heuristics behind it (see that function), so be sure to try it
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* exactly as-is as well as making variants.
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*/
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all_pathkeys = select_outer_pathkeys_for_merge(root,
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mergeclause_list,
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joinrel);
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foreach(l, all_pathkeys)
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{
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List *front_pathkey = (List *) lfirst(l);
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List *cur_mergeclauses;
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List *outerkeys;
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List *innerkeys;
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List *merge_pathkeys;
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/* Make a pathkey list with this guy first */
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if (l != list_head(all_pathkeys))
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outerkeys = lcons(front_pathkey,
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list_delete_ptr(list_copy(all_pathkeys),
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front_pathkey));
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else
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outerkeys = all_pathkeys; /* no work at first one... */
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/* Sort the mergeclauses into the corresponding ordering */
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cur_mergeclauses = find_mergeclauses_for_pathkeys(root,
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outerkeys,
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true,
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mergeclause_list);
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/* Should have used them all... */
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Assert(list_length(cur_mergeclauses) == list_length(mergeclause_list));
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/* Build sort pathkeys for the inner side */
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innerkeys = make_inner_pathkeys_for_merge(root,
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cur_mergeclauses,
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outerkeys);
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/* Build pathkeys representing output sort order */
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merge_pathkeys = build_join_pathkeys(root, joinrel, jointype,
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outerkeys);
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/*
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* And now we can make the path.
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*
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* Note: it's possible that the cheapest paths will already be sorted
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* properly. create_mergejoin_path will detect that case and suppress
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* an explicit sort step, so we needn't do so here.
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*/
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add_path(joinrel, (Path *)
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create_mergejoin_path(root,
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joinrel,
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jointype,
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sjinfo,
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outer_path,
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inner_path,
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restrictlist,
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merge_pathkeys,
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cur_mergeclauses,
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outerkeys,
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innerkeys));
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}
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}
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/*
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* match_unsorted_outer
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* Creates possible join paths for processing a single join relation
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* 'joinrel' by employing either iterative substitution or
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* mergejoining on each of its possible outer paths (considering
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* only outer paths that are already ordered well enough for merging).
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*
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* We always generate a nestloop path for each available outer path.
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* In fact we may generate as many as five: one on the cheapest-total-cost
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* inner path, one on the same with materialization, one on the
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* cheapest-startup-cost inner path (if different), one on the
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* cheapest-total inner-indexscan path (if any), and one on the
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* cheapest-startup inner-indexscan path (if different).
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*
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* We also consider mergejoins if mergejoin clauses are available. We have
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* two ways to generate the inner path for a mergejoin: sort the cheapest
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* inner path, or use an inner path that is already suitably ordered for the
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* merge. If we have several mergeclauses, it could be that there is no inner
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* path (or only a very expensive one) for the full list of mergeclauses, but
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* better paths exist if we truncate the mergeclause list (thereby discarding
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* some sort key requirements). So, we consider truncations of the
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* mergeclause list as well as the full list. (Ideally we'd consider all
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* subsets of the mergeclause list, but that seems way too expensive.)
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*
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* 'joinrel' is the join relation
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* 'outerrel' is the outer join relation
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* 'innerrel' is the inner join relation
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* 'restrictlist' contains all of the RestrictInfo nodes for restriction
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* clauses that apply to this join
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* 'mergeclause_list' is a list of RestrictInfo nodes for available
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* mergejoin clauses in this join
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* 'jointype' is the type of join to do
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* 'sjinfo' is extra info about the join for selectivity estimation
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*/
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static void
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match_unsorted_outer(PlannerInfo *root,
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RelOptInfo *joinrel,
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RelOptInfo *outerrel,
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RelOptInfo *innerrel,
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List *restrictlist,
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List *mergeclause_list,
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JoinType jointype,
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SpecialJoinInfo *sjinfo)
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{
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JoinType save_jointype = jointype;
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bool nestjoinOK;
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bool useallclauses;
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Path *inner_cheapest_startup = innerrel->cheapest_startup_path;
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Path *inner_cheapest_total = innerrel->cheapest_total_path;
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Path *matpath = NULL;
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Path *index_cheapest_startup = NULL;
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Path *index_cheapest_total = NULL;
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ListCell *l;
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/*
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* Nestloop only supports inner, left, semi, and anti joins. Also, if we
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* are doing a right or full join, we must use *all* the mergeclauses as
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* join clauses, else we will not have a valid plan. (Although these two
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* flags are currently inverses, keep them separate for clarity and
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* possible future changes.)
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*/
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switch (jointype)
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{
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case JOIN_INNER:
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case JOIN_LEFT:
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case JOIN_SEMI:
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case JOIN_ANTI:
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nestjoinOK = true;
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useallclauses = false;
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break;
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case JOIN_RIGHT:
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case JOIN_FULL:
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nestjoinOK = false;
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useallclauses = true;
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break;
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case JOIN_UNIQUE_OUTER:
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case JOIN_UNIQUE_INNER:
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jointype = JOIN_INNER;
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nestjoinOK = true;
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useallclauses = false;
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break;
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default:
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elog(ERROR, "unrecognized join type: %d",
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(int) jointype);
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nestjoinOK = false; /* keep compiler quiet */
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useallclauses = false;
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break;
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}
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/*
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* If we need to unique-ify the inner path, we will consider only the
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* cheapest inner.
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*/
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if (save_jointype == JOIN_UNIQUE_INNER)
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{
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inner_cheapest_total = (Path *)
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create_unique_path(root, innerrel, inner_cheapest_total, sjinfo);
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Assert(inner_cheapest_total);
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inner_cheapest_startup = inner_cheapest_total;
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}
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else if (nestjoinOK)
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{
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/*
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* If the cheapest inner path is a join or seqscan, we should consider
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* materializing it. (This is a heuristic: we could consider it
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* always, but for inner indexscans it's probably a waste of time.)
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* Also skip it if the inner path materializes its output anyway.
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*/
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if (!(inner_cheapest_total->pathtype == T_IndexScan ||
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inner_cheapest_total->pathtype == T_BitmapHeapScan ||
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inner_cheapest_total->pathtype == T_TidScan ||
|
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inner_cheapest_total->pathtype == T_Material ||
|
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inner_cheapest_total->pathtype == T_FunctionScan ||
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inner_cheapest_total->pathtype == T_CteScan ||
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inner_cheapest_total->pathtype == T_WorkTableScan))
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matpath = (Path *)
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create_material_path(innerrel, inner_cheapest_total);
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|
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/*
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* Get the best innerjoin indexpaths (if any) for this outer rel.
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* They're the same for all outer paths.
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*/
|
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if (innerrel->reloptkind != RELOPT_JOINREL)
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{
|
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if (IsA(inner_cheapest_total, AppendPath))
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index_cheapest_total = best_appendrel_indexscan(root,
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innerrel,
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outerrel,
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jointype);
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else if (innerrel->rtekind == RTE_RELATION)
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best_inner_indexscan(root, innerrel, outerrel, jointype,
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&index_cheapest_startup,
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&index_cheapest_total);
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}
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}
|
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|
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foreach(l, outerrel->pathlist)
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{
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Path *outerpath = (Path *) lfirst(l);
|
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List *merge_pathkeys;
|
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List *mergeclauses;
|
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List *innersortkeys;
|
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List *trialsortkeys;
|
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Path *cheapest_startup_inner;
|
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Path *cheapest_total_inner;
|
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int num_sortkeys;
|
|
int sortkeycnt;
|
|
|
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/*
|
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* If we need to unique-ify the outer path, it's pointless to consider
|
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* any but the cheapest outer.
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*/
|
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if (save_jointype == JOIN_UNIQUE_OUTER)
|
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{
|
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if (outerpath != outerrel->cheapest_total_path)
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continue;
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outerpath = (Path *) create_unique_path(root, outerrel,
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outerpath, sjinfo);
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Assert(outerpath);
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}
|
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|
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/*
|
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* The result will have this sort order (even if it is implemented as
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* a nestloop, and even if some of the mergeclauses are implemented by
|
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* qpquals rather than as true mergeclauses):
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*/
|
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merge_pathkeys = build_join_pathkeys(root, joinrel, jointype,
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outerpath->pathkeys);
|
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|
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if (nestjoinOK)
|
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{
|
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/*
|
|
* Always consider a nestloop join with this outer and
|
|
* cheapest-total-cost inner. When appropriate, also consider
|
|
* using the materialized form of the cheapest inner, the
|
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* cheapest-startup-cost inner path, and the cheapest innerjoin
|
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* indexpaths.
|
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*/
|
|
add_path(joinrel, (Path *)
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create_nestloop_path(root,
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joinrel,
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jointype,
|
|
sjinfo,
|
|
outerpath,
|
|
inner_cheapest_total,
|
|
restrictlist,
|
|
merge_pathkeys));
|
|
if (matpath != NULL)
|
|
add_path(joinrel, (Path *)
|
|
create_nestloop_path(root,
|
|
joinrel,
|
|
jointype,
|
|
sjinfo,
|
|
outerpath,
|
|
matpath,
|
|
restrictlist,
|
|
merge_pathkeys));
|
|
if (inner_cheapest_startup != inner_cheapest_total)
|
|
add_path(joinrel, (Path *)
|
|
create_nestloop_path(root,
|
|
joinrel,
|
|
jointype,
|
|
sjinfo,
|
|
outerpath,
|
|
inner_cheapest_startup,
|
|
restrictlist,
|
|
merge_pathkeys));
|
|
if (index_cheapest_total != NULL)
|
|
add_path(joinrel, (Path *)
|
|
create_nestloop_path(root,
|
|
joinrel,
|
|
jointype,
|
|
sjinfo,
|
|
outerpath,
|
|
index_cheapest_total,
|
|
restrictlist,
|
|
merge_pathkeys));
|
|
if (index_cheapest_startup != NULL &&
|
|
index_cheapest_startup != index_cheapest_total)
|
|
add_path(joinrel, (Path *)
|
|
create_nestloop_path(root,
|
|
joinrel,
|
|
jointype,
|
|
sjinfo,
|
|
outerpath,
|
|
index_cheapest_startup,
|
|
restrictlist,
|
|
merge_pathkeys));
|
|
}
|
|
|
|
/* Can't do anything else if outer path needs to be unique'd */
|
|
if (save_jointype == JOIN_UNIQUE_OUTER)
|
|
continue;
|
|
|
|
/* Look for useful mergeclauses (if any) */
|
|
mergeclauses = find_mergeclauses_for_pathkeys(root,
|
|
outerpath->pathkeys,
|
|
true,
|
|
mergeclause_list);
|
|
|
|
/*
|
|
* Done with this outer path if no chance for a mergejoin.
|
|
*
|
|
* Special corner case: for "x FULL JOIN y ON true", there will be no
|
|
* join clauses at all. Ordinarily we'd generate a clauseless
|
|
* nestloop path, but since mergejoin is our only join type that
|
|
* supports FULL JOIN, it's necessary to generate a clauseless
|
|
* mergejoin path instead.
|
|
*/
|
|
if (mergeclauses == NIL)
|
|
{
|
|
if (jointype == JOIN_FULL)
|
|
/* okay to try for mergejoin */ ;
|
|
else
|
|
continue;
|
|
}
|
|
if (useallclauses && list_length(mergeclauses) != list_length(mergeclause_list))
|
|
continue;
|
|
|
|
/* Compute the required ordering of the inner path */
|
|
innersortkeys = make_inner_pathkeys_for_merge(root,
|
|
mergeclauses,
|
|
outerpath->pathkeys);
|
|
|
|
/*
|
|
* Generate a mergejoin on the basis of sorting the cheapest inner.
|
|
* Since a sort will be needed, only cheapest total cost matters. (But
|
|
* create_mergejoin_path will do the right thing if
|
|
* inner_cheapest_total is already correctly sorted.)
|
|
*/
|
|
add_path(joinrel, (Path *)
|
|
create_mergejoin_path(root,
|
|
joinrel,
|
|
jointype,
|
|
sjinfo,
|
|
outerpath,
|
|
inner_cheapest_total,
|
|
restrictlist,
|
|
merge_pathkeys,
|
|
mergeclauses,
|
|
NIL,
|
|
innersortkeys));
|
|
|
|
/* Can't do anything else if inner path needs to be unique'd */
|
|
if (save_jointype == JOIN_UNIQUE_INNER)
|
|
continue;
|
|
|
|
/*
|
|
* Look for presorted inner paths that satisfy the innersortkey list
|
|
* --- or any truncation thereof, if we are allowed to build a
|
|
* mergejoin using a subset of the merge clauses. Here, we consider
|
|
* both cheap startup cost and cheap total cost.
|
|
*
|
|
* As we shorten the sortkey list, we should consider only paths that
|
|
* are strictly cheaper than (in particular, not the same as) any path
|
|
* found in an earlier iteration. Otherwise we'd be intentionally
|
|
* using fewer merge keys than a given path allows (treating the rest
|
|
* as plain joinquals), which is unlikely to be a good idea. Also,
|
|
* eliminating paths here on the basis of compare_path_costs is a lot
|
|
* cheaper than building the mergejoin path only to throw it away.
|
|
*
|
|
* If inner_cheapest_total is well enough sorted to have not required
|
|
* a sort in the path made above, we shouldn't make a duplicate path
|
|
* with it, either. We handle that case with the same logic that
|
|
* handles the previous consideration, by initializing the variables
|
|
* that track cheapest-so-far properly. Note that we do NOT reject
|
|
* inner_cheapest_total if we find it matches some shorter set of
|
|
* pathkeys. That case corresponds to using fewer mergekeys to avoid
|
|
* sorting inner_cheapest_total, whereas we did sort it above, so the
|
|
* plans being considered are different.
|
|
*/
|
|
if (pathkeys_contained_in(innersortkeys,
|
|
inner_cheapest_total->pathkeys))
|
|
{
|
|
/* inner_cheapest_total didn't require a sort */
|
|
cheapest_startup_inner = inner_cheapest_total;
|
|
cheapest_total_inner = inner_cheapest_total;
|
|
}
|
|
else
|
|
{
|
|
/* it did require a sort, at least for the full set of keys */
|
|
cheapest_startup_inner = NULL;
|
|
cheapest_total_inner = NULL;
|
|
}
|
|
num_sortkeys = list_length(innersortkeys);
|
|
if (num_sortkeys > 1 && !useallclauses)
|
|
trialsortkeys = list_copy(innersortkeys); /* need modifiable copy */
|
|
else
|
|
trialsortkeys = innersortkeys; /* won't really truncate */
|
|
|
|
for (sortkeycnt = num_sortkeys; sortkeycnt > 0; sortkeycnt--)
|
|
{
|
|
Path *innerpath;
|
|
List *newclauses = NIL;
|
|
|
|
/*
|
|
* Look for an inner path ordered well enough for the first
|
|
* 'sortkeycnt' innersortkeys. NB: trialsortkeys list is modified
|
|
* destructively, which is why we made a copy...
|
|
*/
|
|
trialsortkeys = list_truncate(trialsortkeys, sortkeycnt);
|
|
innerpath = get_cheapest_path_for_pathkeys(innerrel->pathlist,
|
|
trialsortkeys,
|
|
TOTAL_COST);
|
|
if (innerpath != NULL &&
|
|
(cheapest_total_inner == NULL ||
|
|
compare_path_costs(innerpath, cheapest_total_inner,
|
|
TOTAL_COST) < 0))
|
|
{
|
|
/* Found a cheap (or even-cheaper) sorted path */
|
|
/* Select the right mergeclauses, if we didn't already */
|
|
if (sortkeycnt < num_sortkeys)
|
|
{
|
|
newclauses =
|
|
find_mergeclauses_for_pathkeys(root,
|
|
trialsortkeys,
|
|
false,
|
|
mergeclauses);
|
|
Assert(newclauses != NIL);
|
|
}
|
|
else
|
|
newclauses = mergeclauses;
|
|
add_path(joinrel, (Path *)
|
|
create_mergejoin_path(root,
|
|
joinrel,
|
|
jointype,
|
|
sjinfo,
|
|
outerpath,
|
|
innerpath,
|
|
restrictlist,
|
|
merge_pathkeys,
|
|
newclauses,
|
|
NIL,
|
|
NIL));
|
|
cheapest_total_inner = innerpath;
|
|
}
|
|
/* Same on the basis of cheapest startup cost ... */
|
|
innerpath = get_cheapest_path_for_pathkeys(innerrel->pathlist,
|
|
trialsortkeys,
|
|
STARTUP_COST);
|
|
if (innerpath != NULL &&
|
|
(cheapest_startup_inner == NULL ||
|
|
compare_path_costs(innerpath, cheapest_startup_inner,
|
|
STARTUP_COST) < 0))
|
|
{
|
|
/* Found a cheap (or even-cheaper) sorted path */
|
|
if (innerpath != cheapest_total_inner)
|
|
{
|
|
/*
|
|
* Avoid rebuilding clause list if we already made one;
|
|
* saves memory in big join trees...
|
|
*/
|
|
if (newclauses == NIL)
|
|
{
|
|
if (sortkeycnt < num_sortkeys)
|
|
{
|
|
newclauses =
|
|
find_mergeclauses_for_pathkeys(root,
|
|
trialsortkeys,
|
|
false,
|
|
mergeclauses);
|
|
Assert(newclauses != NIL);
|
|
}
|
|
else
|
|
newclauses = mergeclauses;
|
|
}
|
|
add_path(joinrel, (Path *)
|
|
create_mergejoin_path(root,
|
|
joinrel,
|
|
jointype,
|
|
sjinfo,
|
|
outerpath,
|
|
innerpath,
|
|
restrictlist,
|
|
merge_pathkeys,
|
|
newclauses,
|
|
NIL,
|
|
NIL));
|
|
}
|
|
cheapest_startup_inner = innerpath;
|
|
}
|
|
|
|
/*
|
|
* Don't consider truncated sortkeys if we need all clauses.
|
|
*/
|
|
if (useallclauses)
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* hash_inner_and_outer
|
|
* Create hashjoin join paths by explicitly hashing both the outer and
|
|
* inner keys of each available hash clause.
|
|
*
|
|
* 'joinrel' is the join relation
|
|
* 'outerrel' is the outer join relation
|
|
* 'innerrel' is the inner join relation
|
|
* 'restrictlist' contains all of the RestrictInfo nodes for restriction
|
|
* clauses that apply to this join
|
|
* 'jointype' is the type of join to do
|
|
* 'sjinfo' is extra info about the join for selectivity estimation
|
|
*/
|
|
static void
|
|
hash_inner_and_outer(PlannerInfo *root,
|
|
RelOptInfo *joinrel,
|
|
RelOptInfo *outerrel,
|
|
RelOptInfo *innerrel,
|
|
List *restrictlist,
|
|
JoinType jointype,
|
|
SpecialJoinInfo *sjinfo)
|
|
{
|
|
bool isouterjoin;
|
|
List *hashclauses;
|
|
ListCell *l;
|
|
|
|
/*
|
|
* Hashjoin only supports inner, left, semi, and anti joins.
|
|
*/
|
|
switch (jointype)
|
|
{
|
|
case JOIN_INNER:
|
|
case JOIN_SEMI:
|
|
case JOIN_UNIQUE_OUTER:
|
|
case JOIN_UNIQUE_INNER:
|
|
isouterjoin = false;
|
|
break;
|
|
case JOIN_LEFT:
|
|
case JOIN_ANTI:
|
|
isouterjoin = true;
|
|
break;
|
|
default:
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* We need to build only one hashpath for any given pair of outer and
|
|
* inner relations; all of the hashable clauses will be used as keys.
|
|
*
|
|
* Scan the join's restrictinfo list to find hashjoinable clauses that are
|
|
* usable with this pair of sub-relations.
|
|
*/
|
|
hashclauses = NIL;
|
|
foreach(l, restrictlist)
|
|
{
|
|
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l);
|
|
|
|
if (!restrictinfo->can_join ||
|
|
restrictinfo->hashjoinoperator == InvalidOid)
|
|
continue; /* not hashjoinable */
|
|
|
|
/*
|
|
* If processing an outer join, only use its own join clauses for
|
|
* hashing. For inner joins we need not be so picky.
|
|
*/
|
|
if (isouterjoin && restrictinfo->is_pushed_down)
|
|
continue;
|
|
|
|
/*
|
|
* Check if clause is usable with these input rels.
|
|
*/
|
|
if (bms_is_subset(restrictinfo->left_relids, outerrel->relids) &&
|
|
bms_is_subset(restrictinfo->right_relids, innerrel->relids))
|
|
{
|
|
/* righthand side is inner */
|
|
}
|
|
else if (bms_is_subset(restrictinfo->left_relids, innerrel->relids) &&
|
|
bms_is_subset(restrictinfo->right_relids, outerrel->relids))
|
|
{
|
|
/* lefthand side is inner */
|
|
}
|
|
else
|
|
continue; /* no good for these input relations */
|
|
|
|
hashclauses = lappend(hashclauses, restrictinfo);
|
|
}
|
|
|
|
/* If we found any usable hashclauses, make a path */
|
|
if (hashclauses)
|
|
{
|
|
/*
|
|
* We consider both the cheapest-total-cost and cheapest-startup-cost
|
|
* outer paths. There's no need to consider any but the
|
|
* cheapest-total-cost inner path, however.
|
|
*/
|
|
Path *cheapest_startup_outer = outerrel->cheapest_startup_path;
|
|
Path *cheapest_total_outer = outerrel->cheapest_total_path;
|
|
Path *cheapest_total_inner = innerrel->cheapest_total_path;
|
|
|
|
/* Unique-ify if need be */
|
|
if (jointype == JOIN_UNIQUE_OUTER)
|
|
{
|
|
cheapest_total_outer = (Path *)
|
|
create_unique_path(root, outerrel,
|
|
cheapest_total_outer, sjinfo);
|
|
Assert(cheapest_total_outer);
|
|
cheapest_startup_outer = cheapest_total_outer;
|
|
jointype = JOIN_INNER;
|
|
}
|
|
else if (jointype == JOIN_UNIQUE_INNER)
|
|
{
|
|
cheapest_total_inner = (Path *)
|
|
create_unique_path(root, innerrel,
|
|
cheapest_total_inner, sjinfo);
|
|
Assert(cheapest_total_inner);
|
|
jointype = JOIN_INNER;
|
|
}
|
|
|
|
add_path(joinrel, (Path *)
|
|
create_hashjoin_path(root,
|
|
joinrel,
|
|
jointype,
|
|
sjinfo,
|
|
cheapest_total_outer,
|
|
cheapest_total_inner,
|
|
restrictlist,
|
|
hashclauses));
|
|
if (cheapest_startup_outer != cheapest_total_outer)
|
|
add_path(joinrel, (Path *)
|
|
create_hashjoin_path(root,
|
|
joinrel,
|
|
jointype,
|
|
sjinfo,
|
|
cheapest_startup_outer,
|
|
cheapest_total_inner,
|
|
restrictlist,
|
|
hashclauses));
|
|
}
|
|
}
|
|
|
|
/*
|
|
* best_appendrel_indexscan
|
|
* Finds the best available set of inner indexscans for a nestloop join
|
|
* with the given append relation on the inside and the given outer_rel
|
|
* outside. Returns an AppendPath comprising the best inner scans, or
|
|
* NULL if there are no possible inner indexscans.
|
|
*
|
|
* Note that we currently consider only cheapest-total-cost. It's not
|
|
* very clear what cheapest-startup-cost might mean for an AppendPath.
|
|
*/
|
|
static Path *
|
|
best_appendrel_indexscan(PlannerInfo *root, RelOptInfo *rel,
|
|
RelOptInfo *outer_rel, JoinType jointype)
|
|
{
|
|
int parentRTindex = rel->relid;
|
|
List *append_paths = NIL;
|
|
bool found_indexscan = false;
|
|
ListCell *l;
|
|
|
|
foreach(l, root->append_rel_list)
|
|
{
|
|
AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
|
|
int childRTindex;
|
|
RelOptInfo *childrel;
|
|
Path *index_cheapest_startup;
|
|
Path *index_cheapest_total;
|
|
|
|
/* append_rel_list contains all append rels; ignore others */
|
|
if (appinfo->parent_relid != parentRTindex)
|
|
continue;
|
|
|
|
childRTindex = appinfo->child_relid;
|
|
childrel = find_base_rel(root, childRTindex);
|
|
Assert(childrel->reloptkind == RELOPT_OTHER_MEMBER_REL);
|
|
|
|
/*
|
|
* Check to see if child was rejected by constraint exclusion. If so,
|
|
* it will have a cheapest_total_path that's a "dummy" path.
|
|
*/
|
|
if (IS_DUMMY_PATH(childrel->cheapest_total_path))
|
|
continue; /* OK, we can ignore it */
|
|
|
|
/*
|
|
* Get the best innerjoin indexpaths (if any) for this child rel.
|
|
*/
|
|
best_inner_indexscan(root, childrel, outer_rel, jointype,
|
|
&index_cheapest_startup, &index_cheapest_total);
|
|
|
|
/*
|
|
* If no luck on an indexpath for this rel, we'll still consider an
|
|
* Append substituting the cheapest-total inner path. However we must
|
|
* find at least one indexpath, else there's not going to be any
|
|
* improvement over the base path for the appendrel.
|
|
*/
|
|
if (index_cheapest_total)
|
|
found_indexscan = true;
|
|
else
|
|
index_cheapest_total = childrel->cheapest_total_path;
|
|
|
|
append_paths = lappend(append_paths, index_cheapest_total);
|
|
}
|
|
|
|
if (!found_indexscan)
|
|
return NULL;
|
|
|
|
/* Form and return the completed Append path. */
|
|
return (Path *) create_append_path(rel, append_paths);
|
|
}
|
|
|
|
/*
|
|
* select_mergejoin_clauses
|
|
* Select mergejoin clauses that are usable for a particular join.
|
|
* Returns a list of RestrictInfo nodes for those clauses.
|
|
*
|
|
* We also mark each selected RestrictInfo to show which side is currently
|
|
* being considered as outer. These are transient markings that are only
|
|
* good for the duration of the current add_paths_to_joinrel() call!
|
|
*
|
|
* We examine each restrictinfo clause known for the join to see
|
|
* if it is mergejoinable and involves vars from the two sub-relations
|
|
* currently of interest.
|
|
*/
|
|
static List *
|
|
select_mergejoin_clauses(PlannerInfo *root,
|
|
RelOptInfo *joinrel,
|
|
RelOptInfo *outerrel,
|
|
RelOptInfo *innerrel,
|
|
List *restrictlist,
|
|
JoinType jointype)
|
|
{
|
|
List *result_list = NIL;
|
|
bool isouterjoin = IS_OUTER_JOIN(jointype);
|
|
bool have_nonmergeable_joinclause = false;
|
|
ListCell *l;
|
|
|
|
foreach(l, restrictlist)
|
|
{
|
|
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l);
|
|
|
|
/*
|
|
* If processing an outer join, only use its own join clauses in the
|
|
* merge. For inner joins we can use pushed-down clauses too. (Note:
|
|
* we don't set have_nonmergeable_joinclause here because pushed-down
|
|
* clauses will become otherquals not joinquals.)
|
|
*/
|
|
if (isouterjoin && restrictinfo->is_pushed_down)
|
|
continue;
|
|
|
|
if (!restrictinfo->can_join ||
|
|
restrictinfo->mergeopfamilies == NIL)
|
|
{
|
|
have_nonmergeable_joinclause = true;
|
|
continue; /* not mergejoinable */
|
|
}
|
|
|
|
/*
|
|
* Check if clause is usable with these input rels. All the vars
|
|
* needed on each side of the clause must be available from one or the
|
|
* other of the input rels.
|
|
*/
|
|
if (bms_is_subset(restrictinfo->left_relids, outerrel->relids) &&
|
|
bms_is_subset(restrictinfo->right_relids, innerrel->relids))
|
|
{
|
|
/* righthand side is inner */
|
|
restrictinfo->outer_is_left = true;
|
|
}
|
|
else if (bms_is_subset(restrictinfo->left_relids, innerrel->relids) &&
|
|
bms_is_subset(restrictinfo->right_relids, outerrel->relids))
|
|
{
|
|
/* lefthand side is inner */
|
|
restrictinfo->outer_is_left = false;
|
|
}
|
|
else
|
|
{
|
|
have_nonmergeable_joinclause = true;
|
|
continue; /* no good for these input relations */
|
|
}
|
|
|
|
/*
|
|
* Insist that each side have a non-redundant eclass. This
|
|
* restriction is needed because various bits of the planner expect
|
|
* that each clause in a merge be associatable with some pathkey in a
|
|
* canonical pathkey list, but redundant eclasses can't appear in
|
|
* canonical sort orderings. (XXX it might be worth relaxing this,
|
|
* but not enough time to address it for 8.3.)
|
|
*
|
|
* Note: it would be bad if this condition failed for an otherwise
|
|
* mergejoinable FULL JOIN clause, since that would result in
|
|
* undesirable planner failure. I believe that is not possible
|
|
* however; a variable involved in a full join could only appear
|
|
* in below_outer_join eclasses, which aren't considered redundant.
|
|
*
|
|
* This case *can* happen for left/right join clauses: the
|
|
* outer-side variable could be equated to a constant. Because we
|
|
* will propagate that constant across the join clause, the loss of
|
|
* ability to do a mergejoin is not really all that big a deal, and
|
|
* so it's not clear that improving this is important.
|
|
*/
|
|
cache_mergeclause_eclasses(root, restrictinfo);
|
|
|
|
if (EC_MUST_BE_REDUNDANT(restrictinfo->left_ec) ||
|
|
EC_MUST_BE_REDUNDANT(restrictinfo->right_ec))
|
|
{
|
|
have_nonmergeable_joinclause = true;
|
|
continue; /* can't handle redundant eclasses */
|
|
}
|
|
|
|
result_list = lappend(result_list, restrictinfo);
|
|
}
|
|
|
|
/*
|
|
* If it is a right/full join then *all* the explicit join clauses must be
|
|
* mergejoinable, else the executor will fail. If we are asked for a right
|
|
* join then just return NIL to indicate no mergejoin is possible (we can
|
|
* handle it as a left join instead). If we are asked for a full join then
|
|
* emit an error, because there is no fallback.
|
|
*/
|
|
if (have_nonmergeable_joinclause)
|
|
{
|
|
switch (jointype)
|
|
{
|
|
case JOIN_RIGHT:
|
|
return NIL; /* not mergejoinable */
|
|
case JOIN_FULL:
|
|
ereport(ERROR,
|
|
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
|
|
errmsg("FULL JOIN is only supported with merge-joinable join conditions")));
|
|
break;
|
|
default:
|
|
/* otherwise, it's OK to have nonmergeable join quals */
|
|
break;
|
|
}
|
|
}
|
|
|
|
return result_list;
|
|
}
|