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Teach the system how to use hashing for UNION. (INTERSECT/EXCEPT will follow,

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but seem like a separate patch since most of the remaining work is on the
executor side.)  I took the opportunity to push selection of the grouping
operators for set operations into the parser where it belongs.  Otherwise this
is just a small exercise in making prepunion.c consider both alternatives.

As with the recent DISTINCT patch, this means we can UNION on datatypes that
can hash but not sort, and it means that UNION without ORDER BY is no longer
certain to produce sorted output.
This commit is contained in:
Tom Lane
2008-08-07 01:11:52 +00:00
parent 3d40d5e70e
commit 2d1d96b1ce
20 changed files with 462 additions and 212 deletions
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5
src/backend/optimizer/util/clauses.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.260 2008/08/02 21:32:00 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.261 2008/08/07 01:11:50 tgl Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
@@ -3933,6 +3933,8 @@ expression_tree_walker(Node *node,
return true;
if (walker(setop->rarg, context))
return true;
/* groupClauses are deemed uninteresting */
}
break;
case T_InClauseInfo:
@@ -4535,6 +4537,7 @@ expression_tree_mutator(Node *node,
FLATCOPY(newnode, setop, SetOperationStmt);
MUTATE(newnode->larg, setop->larg, Node *);
MUTATE(newnode->rarg, setop->rarg, Node *);
/* We do not mutate groupClauses by default */
return (Node *) newnode;
}
break;