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Reimplement CASE val WHEN compval1 THEN ... WHEN compval2 THEN ... END

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so that the 'val' is computed only once, per recent discussion.  The
speedup is not much when 'val' is just a simple variable, but could be
significant for larger expressions.  More importantly this avoids issues
with multiple evaluations of a volatile 'val', and it allows the CASE
expression to be reverse-listed in its original form by ruleutils.c.
This commit is contained in:
Tom Lane
2004-03-17 20:48:43 +00:00
parent 8c702ea7ac
commit 55f7c3300d
16 changed files with 248 additions and 55 deletions
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3
src/include/nodes/nodes.h
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@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/nodes/nodes.h,v 1.150 2004/01/07 18:43:36 neilc Exp $
* $PostgreSQL: pgsql/src/include/nodes/nodes.h,v 1.151 2004/03/17 20:48:43 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -113,6 +113,7 @@ typedef enum NodeTag
T_RelabelType,
T_CaseExpr,
T_CaseWhen,
T_CaseTestExpr,
T_ArrayExpr,
T_CoalesceExpr,
T_NullIfExpr,