diff options
Diffstat (limited to 'src/backend/optimizer/prep/prepunion.c')
| -rw-r--r-- | src/backend/optimizer/prep/prepunion.c | 45 |
1 files changed, 40 insertions, 5 deletions
diff --git a/src/backend/optimizer/prep/prepunion.c b/src/backend/optimizer/prep/prepunion.c index e8b78509475..2e22d09b4ad 100644 --- a/src/backend/optimizer/prep/prepunion.c +++ b/src/backend/optimizer/prep/prepunion.c @@ -22,7 +22,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.157 2008/10/06 17:39:26 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/prep/prepunion.c,v 1.158 2008/10/07 19:27:04 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -318,10 +318,12 @@ generate_recursion_plan(SetOperationStmt *setOp, PlannerInfo *root, Plan *lplan; Plan *rplan; List *tlist; + List *groupList; + long numGroups; /* Parser should have rejected other cases */ - if (setOp->op != SETOP_UNION || !setOp->all) - elog(ERROR, "only UNION ALL queries can be recursive"); + if (setOp->op != SETOP_UNION) + elog(ERROR, "only UNION queries can be recursive"); /* Worktable ID should be assigned */ Assert(root->wt_param_id >= 0); @@ -347,12 +349,45 @@ generate_recursion_plan(SetOperationStmt *setOp, PlannerInfo *root, refnames_tlist); /* + * If UNION, identify the grouping operators + */ + if (setOp->all) + { + groupList = NIL; + numGroups = 0; + } + else + { + double dNumGroups; + + /* Identify the grouping semantics */ + groupList = generate_setop_grouplist(setOp, tlist); + + /* We only support hashing here */ + if (!grouping_is_hashable(groupList)) + ereport(ERROR, + (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), + errmsg("could not implement recursive UNION"), + errdetail("All column datatypes must be hashable."))); + + /* + * For the moment, take the number of distinct groups as equal to + * the total input size, ie, the worst case. + */ + dNumGroups = lplan->plan_rows + rplan->plan_rows * 10; + + /* Also convert to long int --- but 'ware overflow! */ + numGroups = (long) Min(dNumGroups, (double) LONG_MAX); + } + + /* * And make the plan node. */ plan = (Plan *) make_recursive_union(tlist, lplan, rplan, - root->wt_param_id); + root->wt_param_id, + groupList, numGroups); - *sortClauses = NIL; /* result of UNION ALL is always unsorted */ + *sortClauses = NIL; /* RecursiveUnion result is always unsorted */ return plan; } |