Allow tupleslots to have a fixed tupledesc, use in executor nodes.

The reason for doing so is that it will allow expression evaluation to
optimize based on the underlying tupledesc. In particular it will
allow to JIT tuple deforming together with the expression itself.

For that expression initialization needs to be moved after the
relevant slots are initialized - mostly unproblematic, except in the
case of nodeWorktablescan.c.

After doing so there's no need for ExecAssignResultType() and
ExecAssignResultTypeFromTL() anymore, as all former callers have been
converted to create a slot with a fixed descriptor.

When creating a slot with a fixed descriptor, tts_values/isnull can be
allocated together with the main slot, reducing allocation overhead
and increasing cache density a bit.

Author: Andres Freund
Discussion: https://postgr.es/m/20171206093717.vqdxe5icqttpxs3p@alap3.anarazel.de

1 files changed, 5 insertions, 57 deletions

diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c
index 50b6edce63d..a8ae37ebc80 100644
--- a/src/backend/executor/execUtils.c
+++ b/src/backend/executor/execUtils.c
@@ -22,7 +22,6 @@
  *		ReScanExprContext
  *
  *		ExecAssignExprContext	Common code for plan node init routines.
- *		ExecAssignResultType
  *		etc
  *
  *		ExecOpenScanRelation	Common code for scan node init routines.
@@ -429,47 +428,6 @@ ExecAssignExprContext(EState *estate, PlanState *planstate)
 }
 
 /* ----------------
- *		ExecAssignResultType
- * ----------------
- */
-void
-ExecAssignResultType(PlanState *planstate, TupleDesc tupDesc)
-{
-	TupleTableSlot *slot = planstate->ps_ResultTupleSlot;
-
-	ExecSetSlotDescriptor(slot, tupDesc);
-}
-
-/* ----------------
- *		ExecAssignResultTypeFromTL
- * ----------------
- */
-void
-ExecAssignResultTypeFromTL(PlanState *planstate)
-{
-	bool		hasoid;
-	TupleDesc	tupDesc;
-
-	if (ExecContextForcesOids(planstate, &hasoid))
-	{
-		/* context forces OID choice; hasoid is now set correctly */
-	}
-	else
-	{
-		/* given free choice, don't leave space for OIDs in result tuples */
-		hasoid = false;
-	}
-
-	/*
-	 * ExecTypeFromTL needs the parse-time representation of the tlist, not a
-	 * list of ExprStates.  This is good because some plan nodes don't bother
-	 * to set up planstate->targetlist ...
-	 */
-	tupDesc = ExecTypeFromTL(planstate->plan->targetlist, hasoid);
-	ExecAssignResultType(planstate, tupDesc);
-}
-
-/* ----------------
  *		ExecGetResultType
  * ----------------
  */
@@ -609,13 +567,9 @@ ExecFreeExprContext(PlanState *planstate)
 	planstate->ps_ExprContext = NULL;
 }
 
+
 /* ----------------------------------------------------------------
- *		the following scan type support functions are for
- *		those nodes which are stubborn and return tuples in
- *		their Scan tuple slot instead of their Result tuple
- *		slot..  luck fur us, these nodes do not do projections
- *		so we don't have to worry about getting the ProjectionInfo
- *		right for them...  -cim 6/3/91
+ *				  Scan node support
  * ----------------------------------------------------------------
  */
 
@@ -632,11 +586,11 @@ ExecAssignScanType(ScanState *scanstate, TupleDesc tupDesc)
 }
 
 /* ----------------
- *		ExecAssignScanTypeFromOuterPlan
+ *		ExecCreateSlotFromOuterPlan
  * ----------------
  */
 void
-ExecAssignScanTypeFromOuterPlan(ScanState *scanstate)
+ExecCreateScanSlotFromOuterPlan(EState *estate, ScanState *scanstate)
 {
 	PlanState  *outerPlan;
 	TupleDesc	tupDesc;
@@ -644,15 +598,9 @@ ExecAssignScanTypeFromOuterPlan(ScanState *scanstate)
 	outerPlan = outerPlanState(scanstate);
 	tupDesc = ExecGetResultType(outerPlan);
 
-	ExecAssignScanType(scanstate, tupDesc);
+	ExecInitScanTupleSlot(estate, scanstate, tupDesc);
 }
 
-
-/* ----------------------------------------------------------------
- *				  Scan node support
- * ----------------------------------------------------------------
- */
-
 /* ----------------------------------------------------------------
  *		ExecRelationIsTargetRelation
  *