diff options
Diffstat (limited to 'src/backend/optimizer/plan/initsplan.c')
| -rw-r--r-- | src/backend/optimizer/plan/initsplan.c | 60 |
1 files changed, 33 insertions, 27 deletions
diff --git a/src/backend/optimizer/plan/initsplan.c b/src/backend/optimizer/plan/initsplan.c index b94cc3e4b42..6b6f3971719 100644 --- a/src/backend/optimizer/plan/initsplan.c +++ b/src/backend/optimizer/plan/initsplan.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/plan/initsplan.c,v 1.44 2000/02/07 04:41:00 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/plan/initsplan.c,v 1.45 2000/02/15 20:49:18 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -21,6 +21,7 @@ #include "optimizer/cost.h" #include "optimizer/joininfo.h" #include "optimizer/pathnode.h" +#include "optimizer/paths.h" #include "optimizer/planmain.h" #include "optimizer/tlist.h" #include "optimizer/var.h" @@ -31,7 +32,6 @@ static void add_restrict_and_join_to_rel(Query *root, Node *clause); static void add_join_info_to_rels(Query *root, RestrictInfo *restrictinfo, Relids join_relids); static void add_vars_to_targetlist(Query *root, List *vars); -static void set_restrictinfo_joininfo(RestrictInfo *restrictinfo); static void check_mergejoinable(RestrictInfo *restrictinfo); static void check_hashjoinable(RestrictInfo *restrictinfo); @@ -150,7 +150,9 @@ add_restrict_and_join_to_rels(Query *root, List *clauses) * Add clause information to either the 'RestrictInfo' or 'JoinInfo' field * (depending on whether the clause is a join) of each base relation * mentioned in the clause. A RestrictInfo node is created and added to - * the appropriate list for each rel. + * the appropriate list for each rel. Also, if the clause uses a + * mergejoinable operator, enter the left- and right-side expressions + * into the query's lists of equijoined vars. */ static void add_restrict_and_join_to_rel(Query *root, Node *clause) @@ -181,14 +183,29 @@ add_restrict_and_join_to_rel(Query *root, Node *clause) rel->baserestrictinfo = lcons(restrictinfo, rel->baserestrictinfo); + /* + * Check for a "mergejoinable" clause even though it's not a join + * clause. This is so that we can recognize that "a.x = a.y" makes + * x and y eligible to be considered equal, even when they belong + * to the same rel. Without this, we would not recognize that + * "a.x = a.y AND a.x = b.z AND a.y = c.q" allows us to consider + * z and q equal after their rels are joined. + */ + check_mergejoinable(restrictinfo); } else { /* * 'clause' is a join clause, since there is more than one atom in * the relid list. Set additional RestrictInfo fields for joining. + * + * We need the merge info whether or not mergejoin is enabled (for + * constructing equijoined-var lists), but we don't bother setting + * hash info if hashjoin is disabled. */ - set_restrictinfo_joininfo(restrictinfo); + check_mergejoinable(restrictinfo); + if (enable_hashjoin) + check_hashjoinable(restrictinfo); /* * Add clause to the join lists of all the relevant * relations. (If, perchance, 'clause' contains NO vars, then @@ -202,6 +219,15 @@ add_restrict_and_join_to_rel(Query *root, Node *clause) */ add_vars_to_targetlist(root, vars); } + + /* + * If the clause has a mergejoinable operator, then the two sides + * represent equivalent PathKeyItems for path keys: any path that is + * sorted by one side will also be sorted by the other (after joining, + * that is). Record the key equivalence for future use. + */ + if (restrictinfo->mergejoinoperator != InvalidOid) + add_equijoined_keys(root, restrictinfo); } /* @@ -247,35 +273,18 @@ add_join_info_to_rels(Query *root, RestrictInfo *restrictinfo, /***************************************************************************** * - * JOININFO + * CHECKS FOR MERGEJOINABLE AND HASHJOINABLE CLAUSES * *****************************************************************************/ /* - * set_restrictinfo_joininfo - * Examine a RestrictInfo that has been determined to be a join clause, - * and set the merge and hash info fields if it can be merge/hash joined. - */ -static void -set_restrictinfo_joininfo(RestrictInfo *restrictinfo) -{ - if (enable_mergejoin) - check_mergejoinable(restrictinfo); - if (enable_hashjoin) - check_hashjoinable(restrictinfo); -} - -/* * check_mergejoinable * If the restrictinfo's clause is mergejoinable, set the mergejoin * info fields in the restrictinfo. * * Currently, we support mergejoin for binary opclauses where * both operands are simple Vars and the operator is a mergejoinable - * operator. (Note: since we are only examining clauses that were - * classified as joins, it is certain that the two Vars belong to - * different relations... if we accepted more general clause structures - * we might need to check that the two sides refer to different rels...) + * operator. */ static void check_mergejoinable(RestrictInfo *restrictinfo) @@ -320,10 +329,7 @@ check_mergejoinable(RestrictInfo *restrictinfo) * * Currently, we support hashjoin for binary opclauses where * both operands are simple Vars and the operator is a hashjoinable - * operator. (Note: since we are only examining clauses that were - * classified as joins, it is certain that the two Vars belong to - * different relations... if we accepted more general clause structures - * we might need to check that the two sides refer to different rels...) + * operator. */ static void check_hashjoinable(RestrictInfo *restrictinfo) |