Replace the switching function ExecEvalExpr() with a macro that jumps

directly to the appropriate per-node execution function, using a function
pointer stored by ExecInitExpr.  This speeds things up by eliminating one
level of function call.  The function-pointer technique also enables further
small improvements such as only making one-time tests once (and then
changing the function pointer).  Overall this seems to gain about 10%
on evaluation of simple expressions, which isn't earthshaking but seems
a worthwhile gain for a relatively small hack.  Per recent discussion
on pghackers.

1 files changed, 10 insertions, 2 deletions

diff --git a/src/backend/executor/nodeSubplan.c b/src/backend/executor/nodeSubplan.c
index 1624f41fd54..8c667b70e78 100644
--- a/src/backend/executor/nodeSubplan.c
+++ b/src/backend/executor/nodeSubplan.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeSubplan.c,v 1.60 2004/01/14 23:01:54 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeSubplan.c,v 1.61 2004/03/17 01:02:23 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -47,10 +47,16 @@ static bool tupleAllNulls(HeapTuple tuple);
 Datum
 ExecSubPlan(SubPlanState *node,
 			ExprContext *econtext,
-			bool *isNull)
+			bool *isNull,
+			ExprDoneCond *isDone)
 {
 	SubPlan    *subplan = (SubPlan *) node->xprstate.expr;
 
+	/* Set default values for result flags: non-null, not a set result */
+	*isNull = false;
+	if (isDone)
+		*isDone = ExprSingleResult;
+
 	if (subplan->setParam != NIL)
 		elog(ERROR, "cannot set parent params from subquery");
 
@@ -819,6 +825,7 @@ ExecInitSubPlan(SubPlanState *node, EState *estate)
 								  expr);
 			tlestate = makeNode(GenericExprState);
 			tlestate->xprstate.expr = (Expr *) tle;
+			tlestate->xprstate.evalfunc = NULL;
 			tlestate->arg = exstate;
 			lefttlist = lappend(lefttlist, tlestate);
 			leftptlist = lappend(leftptlist, tle);
@@ -834,6 +841,7 @@ ExecInitSubPlan(SubPlanState *node, EState *estate)
 								  expr);
 			tlestate = makeNode(GenericExprState);
 			tlestate->xprstate.expr = (Expr *) tle;
+			tlestate->xprstate.evalfunc = NULL;
 			tlestate->arg = exstate;
 			righttlist = lappend(righttlist, tlestate);
 			rightptlist = lappend(rightptlist, tle);