Revise TupleTableSlot code to avoid unnecessary construction and disassembly

of tuples when passing data up through multiple plan nodes.  A slot can now
hold either a normal "physical" HeapTuple, or a "virtual" tuple consisting
of Datum/isnull arrays.  Upper plan levels can usually just copy the Datum
arrays, avoiding heap_formtuple() and possible subsequent nocachegetattr()
calls to extract the data again.  This work extends Atsushi Ogawa's earlier
patch, which provided the key idea of adding Datum arrays to TupleTableSlots.
(I believe however that something like this was foreseen way back in Berkeley
days --- see the old comment on ExecProject.)  A test case involving many
levels of join of fairly wide tables (about 80 columns altogether) showed
about 3x overall speedup, though simple queries will probably not be
helped very much.

I have also duplicated some code in heaptuple.c in order to provide versions
of heap_formtuple and friends that use "bool" arrays to indicate null
attributes, instead of the old convention of "char" arrays containing either
'n' or ' '.  This provides a better match to the convention used by
ExecEvalExpr.  While I have not made a concerted effort to get rid of uses
of the old routines, I think they should be deprecated and eventually removed.

1 files changed, 17 insertions, 31 deletions

diff --git a/src/backend/executor/nodeGroup.c b/src/backend/executor/nodeGroup.c
index f8bd18f3499..e16a228fa15 100644
--- a/src/backend/executor/nodeGroup.c
+++ b/src/backend/executor/nodeGroup.c
@@ -15,7 +15,7 @@
  *	  locate group boundaries.
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeGroup.c,v 1.60 2005/03/10 23:21:21 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeGroup.c,v 1.61 2005/03/16 21:38:07 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -36,11 +36,9 @@ TupleTableSlot *
 ExecGroup(GroupState *node)
 {
 	ExprContext *econtext;
-	TupleDesc	tupdesc;
 	int			numCols;
 	AttrNumber *grpColIdx;
-	HeapTuple	outerTuple;
-	HeapTuple	firsttuple;
+	TupleTableSlot *firsttupleslot;
 	TupleTableSlot *outerslot;
 
 	/*
@@ -49,11 +47,15 @@ ExecGroup(GroupState *node)
 	if (node->grp_done)
 		return NULL;
 	econtext = node->ss.ps.ps_ExprContext;
-	tupdesc = ExecGetScanType(&node->ss);
 	numCols = ((Group *) node->ss.ps.plan)->numCols;
 	grpColIdx = ((Group *) node->ss.ps.plan)->grpColIdx;
 
 	/*
+	 * The ScanTupleSlot holds the (copied) first tuple of each group.
+	 */
+	firsttupleslot = node->ss.ss_ScanTupleSlot;
+
+	/*
 	 * We need not call ResetExprContext here because execTuplesMatch will
 	 * reset the per-tuple memory context once per input tuple.
 	 */
@@ -62,8 +64,7 @@ ExecGroup(GroupState *node)
 	 * If first time through, acquire first input tuple and determine
 	 * whether to return it or not.
 	 */
-	firsttuple = node->grp_firstTuple;
-	if (firsttuple == NULL)
+	if (TupIsNull(firsttupleslot))
 	{
 		outerslot = ExecProcNode(outerPlanState(node));
 		if (TupIsNull(outerslot))
@@ -72,13 +73,9 @@ ExecGroup(GroupState *node)
 			node->grp_done = TRUE;
 			return NULL;
 		}
-		node->grp_firstTuple = firsttuple = heap_copytuple(outerslot->val);
-		/* Set up tuple as input for qual test and projection */
-		ExecStoreTuple(firsttuple,
-					   node->ss.ss_ScanTupleSlot,
-					   InvalidBuffer,
-					   false);
-		econtext->ecxt_scantuple = node->ss.ss_ScanTupleSlot;
+		/* Copy tuple, set up as input for qual test and projection */
+		ExecCopySlot(firsttupleslot, outerslot);
+		econtext->ecxt_scantuple = firsttupleslot;
 		/*
 		 * Check the qual (HAVING clause); if the group does not match,
 		 * ignore it and fall into scan loop.
@@ -112,14 +109,12 @@ ExecGroup(GroupState *node)
 				node->grp_done = TRUE;
 				return NULL;
 			}
-			outerTuple = outerslot->val;
 
 			/*
 			 * Compare with first tuple and see if this tuple is of the same
 			 * group.  If so, ignore it and keep scanning.
 			 */
-			if (!execTuplesMatch(firsttuple, outerTuple,
-								 tupdesc,
+			if (!execTuplesMatch(firsttupleslot, outerslot,
 								 numCols, grpColIdx,
 								 node->eqfunctions,
 								 econtext->ecxt_per_tuple_memory))
@@ -129,14 +124,9 @@ ExecGroup(GroupState *node)
 		 * We have the first tuple of the next input group.  See if we
 		 * want to return it.
 		 */
-		heap_freetuple(firsttuple);
-		node->grp_firstTuple = firsttuple = heap_copytuple(outerTuple);
-		/* Set up tuple as input for qual test and projection */
-		ExecStoreTuple(firsttuple,
-					   node->ss.ss_ScanTupleSlot,
-					   InvalidBuffer,
-					   false);
-		econtext->ecxt_scantuple = node->ss.ss_ScanTupleSlot;
+		/* Copy tuple, set up as input for qual test and projection */
+		ExecCopySlot(firsttupleslot, outerslot);
+		econtext->ecxt_scantuple = firsttupleslot;
 		/*
 		 * Check the qual (HAVING clause); if the group does not match,
 		 * ignore it and loop back to scan the rest of the group.
@@ -173,7 +163,6 @@ ExecInitGroup(Group *node, EState *estate)
 	grpstate = makeNode(GroupState);
 	grpstate->ss.ps.plan = (Plan *) node;
 	grpstate->ss.ps.state = estate;
-	grpstate->grp_firstTuple = NULL;
 	grpstate->grp_done = FALSE;
 
 	/*
@@ -255,11 +244,8 @@ void
 ExecReScanGroup(GroupState *node, ExprContext *exprCtxt)
 {
 	node->grp_done = FALSE;
-	if (node->grp_firstTuple != NULL)
-	{
-		heap_freetuple(node->grp_firstTuple);
-		node->grp_firstTuple = NULL;
-	}
+	/* must clear first tuple */
+	ExecClearTuple(node->ss.ss_ScanTupleSlot);
 
 	if (((PlanState *) node)->lefttree &&
 		((PlanState *) node)->lefttree->chgParam == NULL)