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

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.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index afdd0669d4..440fcc4d57 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -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/execnodes.h,v 1.113 2004/03/17 01:02:24 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/nodes/execnodes.h,v 1.114 2004/03/17 20:48:42 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -113,6 +113,10 @@ typedef struct ExprContext
 	Datum	   *ecxt_aggvalues; /* precomputed values for Aggref nodes */
 	bool	   *ecxt_aggnulls;	/* null flags for Aggref nodes */
 
+	/* Value to substitute for CaseTestExpr nodes in expression */
+	Datum		caseValue_datum;
+	bool		caseValue_isNull;
+
 	/* Value to substitute for CoerceToDomainValue nodes in expression */
 	Datum		domainValue_datum;
 	bool		domainValue_isNull;
@@ -566,6 +570,7 @@ typedef struct SubPlanState
 typedef struct CaseExprState
 {
 	ExprState	xprstate;
+	ExprState  *arg;			/* implicit equality comparison argument */
 	List	   *args;			/* the arguments (list of WHEN clauses) */
 	ExprState  *defresult;		/* the default result (ELSE clause) */
 } CaseExprState;