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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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14
src/backend/nodes/equalfuncs.c
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@@ -18,7 +18,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.217 2004/03/14 23:41:26 tgl Exp $
* $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.218 2004/03/17 20:48:42 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -403,6 +403,15 @@ _equalCaseWhen(CaseWhen *a, CaseWhen *b)
return true;
}
static bool
_equalCaseTestExpr(CaseTestExpr *a, CaseTestExpr *b)
{
COMPARE_SCALAR_FIELD(typeId);
COMPARE_SCALAR_FIELD(typeMod);
return true;
}
static bool
_equalArrayExpr(ArrayExpr *a, ArrayExpr *b)
{
@@ -1724,6 +1733,9 @@ equal(void *a, void *b)
case T_CaseWhen:
retval = _equalCaseWhen(a, b);
break;
case T_CaseTestExpr:
retval = _equalCaseTestExpr(a, b);
break;
case T_ArrayExpr:
retval = _equalArrayExpr(a, b);
break;