diff options
Diffstat (limited to 'src/backend/optimizer')
| -rw-r--r-- | src/backend/optimizer/path/allpaths.c | 10 | ||||
| -rw-r--r-- | src/backend/optimizer/util/clauses.c | 56 |
2 files changed, 62 insertions, 4 deletions
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c index 1cf73dffff7..820a0e6e26f 100644 --- a/src/backend/optimizer/path/allpaths.c +++ b/src/backend/optimizer/path/allpaths.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/path/allpaths.c,v 1.72 2001/03/22 03:59:34 momjian Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/path/allpaths.c,v 1.72.2.1 2001/07/31 18:39:12 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -125,11 +125,17 @@ set_base_rel_pathlists(Query *root) * Non-pushed-down clauses will get evaluated as qpquals of * the SubqueryScan node. * + * We can't push down into subqueries with LIMIT or DISTINCT ON + * clauses, either. + * * 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? */ - if (rte->subquery->setOperations == NULL) + if (rte->subquery->setOperations == NULL && + rte->subquery->limitOffset == NULL && + rte->subquery->limitCount == NULL && + !has_distinct_on_clause(rte->subquery)) { /* OK to consider pushing down individual quals */ List *upperrestrictlist = NIL; diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c index 8bd6ef6f68b..5e2a7b63dca 100644 --- a/src/backend/optimizer/util/clauses.c +++ b/src/backend/optimizer/util/clauses.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.84 2001/03/27 17:12:34 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/util/clauses.c,v 1.84.2.1 2001/07/31 18:39:12 tgl Exp $ * * HISTORY * AUTHOR DATE MAJOR EVENT @@ -730,13 +730,65 @@ pull_constant_clauses(List *quals, List **constantQual) /***************************************************************************** + * Tests on clauses of queries + * + * Possibly this code should go someplace else, since this isn't quite the + * same meaning of "clause" as is used elsewhere in this module. But I can't + * think of a better place for it... + *****************************************************************************/ + +/* + * Test whether a query uses DISTINCT ON, ie, has a distinct-list that is + * just a subset of the output columns. + */ +bool +has_distinct_on_clause(Query *query) +{ + List *targetList; + + /* Is there a DISTINCT clause at all? */ + if (query->distinctClause == NIL) + return false; + /* + * If the DISTINCT list contains all the nonjunk targetlist items, + * then it's a simple DISTINCT, else it's DISTINCT ON. We do not + * require the lists to be in the same order (since the parser may + * have adjusted the DISTINCT clause ordering to agree with ORDER BY). + */ + foreach(targetList, query->targetList) + { + TargetEntry *tle = (TargetEntry *) lfirst(targetList); + Index ressortgroupref; + List *distinctClause; + + if (tle->resdom->resjunk) + continue; + ressortgroupref = tle->resdom->ressortgroupref; + if (ressortgroupref == 0) + return true; /* definitely not in DISTINCT list */ + foreach(distinctClause, query->distinctClause) + { + SortClause *scl = (SortClause *) lfirst(distinctClause); + + if (scl->tleSortGroupRef == ressortgroupref) + break; /* found TLE in DISTINCT */ + } + if (distinctClause == NIL) + return true; /* this TLE is not in DISTINCT list */ + } + /* It's a simple DISTINCT */ + return false; +} + + +/***************************************************************************** * * * General clause-manipulating routines * * * *****************************************************************************/ /* - * clause_relids_vars + * clause_get_relids_vars * Retrieves distinct relids and vars appearing within a clause. * * '*relids' is set to an integer list of all distinct "varno"s appearing |