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Fix EquivalenceClass code to handle volatile sort expressions in a more

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predictable manner; in particular that if you say ORDER BY output-column-ref,
it will in fact sort by that specific column even if there are multiple
syntactic matches.  An example is
	SELECT random() AS a, random() AS b FROM ... ORDER BY b, a;
While the use-case for this might be a bit debatable, it worked as expected
in earlier releases, so we should preserve the behavior for 8.3.  Per my
recent proposal.

While at it, fix convert_subquery_pathkeys() to handle RelabelType stripping
in both directions; it needs this for the same reasons make_sort_from_pathkeys
does.
This commit is contained in:
Tom Lane
2007-11-08 21:49:48 +00:00
parent 1be0601681
commit c291203ca3
8 changed files with 304 additions and 187 deletions
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14
src/backend/optimizer/path/equivclass.c
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@@ -10,7 +10,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/equivclass.c,v 1.3 2007/07/07 20:46:45 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/equivclass.c,v 1.4 2007/11/08 21:49:47 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -294,6 +294,7 @@ process_equivalence(PlannerInfo *root, RestrictInfo *restrictinfo,
ec->ec_has_volatile = false;
ec->ec_below_outer_join = below_outer_join;
ec->ec_broken = false;
ec->ec_sortref = 0;
ec->ec_merged = NULL;
em1 = add_eq_member(ec, item1, item1_relids, false, item1_type);
em2 = add_eq_member(ec, item2, item2_relids, false, item2_type);
@@ -354,6 +355,9 @@ add_eq_member(EquivalenceClass *ec, Expr *expr, Relids relids,
* class it is a member of; if none, build a new single-member
* EquivalenceClass for it.
*
* sortref is the SortGroupRef of the originating SortClause, if any,
* or zero if not.
*
* This can be used safely both before and after EquivalenceClass merging;
* since it never causes merging it does not invalidate any existing ECs
* or PathKeys.
@@ -367,7 +371,8 @@ EquivalenceClass *
get_eclass_for_sort_expr(PlannerInfo *root,
Expr *expr,
Oid expr_datatype,
List *opfamilies)
List *opfamilies,
Index sortref)
{
EquivalenceClass *newec;
EquivalenceMember *newem;
@@ -382,7 +387,9 @@ get_eclass_for_sort_expr(PlannerInfo *root,
EquivalenceClass *cur_ec = (EquivalenceClass *) lfirst(lc1);
ListCell *lc2;
/* we allow matching to a volatile EC here */
/* Never match to a volatile EC */
if (cur_ec->ec_has_volatile)
continue;
if (!equal(opfamilies, cur_ec->ec_opfamilies))
continue;
@@ -423,6 +430,7 @@ get_eclass_for_sort_expr(PlannerInfo *root,
newec->ec_has_volatile = contain_volatile_functions((Node *) expr);
newec->ec_below_outer_join = false;
newec->ec_broken = false;
newec->ec_sortref = sortref;
newec->ec_merged = NULL;
newem = add_eq_member(newec, expr, pull_varnos((Node *) expr),
false, expr_datatype);