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Do not allow Unique nodes to be scanned backwards. The code claimed that it

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would work, but in fact it didn't return the same rows when moving backwards
as when moving forwards.  This would have no visible effect in a DISTINCT
query (at least assuming the column datatypes use a strong definition of
equality), but it gave entirely wrong answers for DISTINCT ON queries.
This commit is contained in:
Tom Lane 2008-08-05 21:29:01 +00:00
parent 20c20dfeec
commit 45b8e6ed68
1 changed files with 1 additions and 4 deletions
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5
src/backend/executor/execAmi.c
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@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California * Portions Copyright (c) 1994, Regents of the University of California
* *
* $Header: /cvsroot/pgsql/src/backend/executor/execAmi.c,v 1.75.4.2 2004/03/02 18:56:28 tgl Exp $ * $Header: /cvsroot/pgsql/src/backend/executor/execAmi.c,v 1.75.4.3 2008/08/05 21:29:01 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -338,9 +338,6 @@ ExecSupportsBackwardScan(Plan *node)
case T_Sort: case T_Sort:
return true; return true;
case T_Unique:
return ExecSupportsBackwardScan(outerPlan(node));
case T_Limit: case T_Limit:
return ExecSupportsBackwardScan(outerPlan(node)); return ExecSupportsBackwardScan(outerPlan(node));