diff options
Diffstat (limited to 'src/backend/optimizer/path/allpaths.c')
| -rw-r--r-- | src/backend/optimizer/path/allpaths.c | 63 |
1 files changed, 59 insertions, 4 deletions
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index 4f7a0e570f5..5e461cb3c15 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -8,13 +8,14 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/path/allpaths.c,v 1.68 2000/12/14 22:30:43 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/path/allpaths.c,v 1.69 2001/01/18 07:12:37 tgl Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" +#include "optimizer/clauses.h" #include "optimizer/cost.h" #include "optimizer/geqo.h" #include "optimizer/pathnode.h" @@ -23,6 +24,7 @@ #include "optimizer/planner.h" #include "optimizer/prep.h" #include "parser/parsetree.h" +#include "rewrite/rewriteManip.h" bool enable_geqo = true; @@ -99,12 +101,65 @@ set_base_rel_pathlists(Query *root) if (rel->issubquery) { /* Subquery --- generate a separate plan for it */ + List *upperrestrictlist; + List *lst; /* - * XXX for now, we just apply any restrict clauses that came - * from the outer query as qpquals of the SubqueryScan node. - * Later, think about pushing them down into the subquery itself. + * If there are any restriction clauses that have been attached + * to the subquery relation, consider pushing them down to become + * HAVING quals of the subquery itself. (Not WHERE clauses, since + * they may refer to subquery outputs that are aggregate results. + * But planner.c will transfer them into the subquery's WHERE if + * they do not.) This transformation is useful because it may + * allow us to generate a better plan for the subquery than + * evaluating all the subquery output rows and then filtering + * them. + * + * Currently, we do not push down clauses that contain subselects, + * mainly because I'm not sure it will work correctly (the + * subplan hasn't yet transformed sublinks to subselects). + * Non-pushed-down clauses will get evaluated as qpquals of + * the SubqueryScan node. + * + * XXX Are there any cases where we want to make a policy + * decision not to push down, because it'd result in a worse + * plan? */ + upperrestrictlist = NIL; + foreach(lst, rel->baserestrictinfo) + { + RestrictInfo *rinfo = (RestrictInfo *) lfirst(lst); + Node *clause = (Node *) rinfo->clause; + + if (contain_subplans(clause)) + { + /* Keep it in the upper query */ + upperrestrictlist = lappend(upperrestrictlist, rinfo); + } + else + { + /* + * We need to replace Vars in the clause (which must + * refer to outputs of the subquery) with copies of the + * subquery's targetlist expressions. Note that at this + * point, any uplevel Vars in the clause should have been + * replaced with Params, so they need no work. + */ + clause = ResolveNew(clause, rti, 0, + rte->subquery->targetList, + CMD_SELECT, 0); + rte->subquery->havingQual = + make_and_qual(rte->subquery->havingQual, + clause); + /* + * We need not change the subquery's hasAggs or + * hasSublinks flags, since we can't be pushing down + * any aggregates that weren't there before, and we + * don't push down subselects at all. + */ + } + } + rel->baserestrictinfo = upperrestrictlist; /* Generate the plan for the subquery */ rel->subplan = subquery_planner(rte->subquery, |