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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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18
src/backend/nodes/readfuncs.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/nodes/readfuncs.c,v 1.165 2004/01/14 23:01:55 tgl Exp $
* $PostgreSQL: pgsql/src/backend/nodes/readfuncs.c,v 1.166 2004/03/17 20:48:42 tgl Exp $
*
* NOTES
* Path and Plan nodes do not have any readfuncs support, because we
@ -648,6 +648,20 @@ _readCaseWhen(void)
READ_DONE();
}
/*
* _readCaseTestExpr
*/
static CaseTestExpr *
_readCaseTestExpr(void)
{
READ_LOCALS(CaseTestExpr);
READ_OID_FIELD(typeId);
READ_INT_FIELD(typeMod);
READ_DONE();
}
/*
* _readArrayExpr
*/
@ -1010,6 +1024,8 @@ parseNodeString(void)
return_value = _readCaseExpr();
else if (MATCH("WHEN", 4))
return_value = _readCaseWhen();
else if (MATCH("CASETESTEXPR", 12))
return_value = _readCaseTestExpr();
else if (MATCH("ARRAY", 5))
return_value = _readArrayExpr();
else if (MATCH("COALESCE", 8))