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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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19
src/backend/nodes/copyfuncs.c
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@ -15,7 +15,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.278 2004/03/11 01:47:35 ishii Exp $
* $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.279 2004/03/17 20:48:42 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -968,6 +968,20 @@ _copyCaseWhen(CaseWhen *from)
return newnode;
}
/*
* _copyCaseTestExpr
*/
static CaseTestExpr *
_copyCaseTestExpr(CaseTestExpr *from)
{
CaseTestExpr *newnode = makeNode(CaseTestExpr);
COPY_SCALAR_FIELD(typeId);
COPY_SCALAR_FIELD(typeMod);
return newnode;
}
/*
* _copyArrayExpr
*/
@ -2643,6 +2657,9 @@ copyObject(void *from)
case T_CaseWhen:
retval = _copyCaseWhen(from);
break;
case T_CaseTestExpr:
retval = _copyCaseTestExpr(from);
break;
case T_ArrayExpr:
retval = _copyArrayExpr(from);
break;