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, 24 insertions, 29 deletions

diff --git a/src/backend/executor/nodeMergejoin.c b/src/backend/executor/nodeMergejoin.c
index ec5f82f6a92..f3cbe2f889b 100644
--- a/src/backend/executor/nodeMergejoin.c
+++ b/src/backend/executor/nodeMergejoin.c
@@ -1436,6 +1436,7 @@ MergeJoinState *
 ExecInitMergeJoin(MergeJoin *node, EState *estate, int eflags)
 {
 	MergeJoinState *mergestate;
+	TupleDesc	outerDesc, innerDesc;
 
 	/* check for unsupported flags */
 	Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
@@ -1450,6 +1451,8 @@ ExecInitMergeJoin(MergeJoin *node, EState *estate, int eflags)
 	mergestate->js.ps.plan = (Plan *) node;
 	mergestate->js.ps.state = estate;
 	mergestate->js.ps.ExecProcNode = ExecMergeJoin;
+	mergestate->js.jointype = node->join.jointype;
+	mergestate->mj_ConstFalseJoin = false;
 
 	/*
 	 * Miscellaneous initialization
@@ -1467,17 +1470,6 @@ ExecInitMergeJoin(MergeJoin *node, EState *estate, int eflags)
 	mergestate->mj_InnerEContext = CreateExprContext(estate);
 
 	/*
-	 * initialize child expressions
-	 */
-	mergestate->js.ps.qual =
-		ExecInitQual(node->join.plan.qual, (PlanState *) mergestate);
-	mergestate->js.jointype = node->join.jointype;
-	mergestate->js.joinqual =
-		ExecInitQual(node->join.joinqual, (PlanState *) mergestate);
-	mergestate->mj_ConstFalseJoin = false;
-	/* mergeclauses are handled below */
-
-	/*
 	 * initialize child nodes
 	 *
 	 * inner child must support MARK/RESTORE, unless we have detected that we
@@ -1488,10 +1480,12 @@ ExecInitMergeJoin(MergeJoin *node, EState *estate, int eflags)
 	mergestate->mj_SkipMarkRestore = node->skip_mark_restore;
 
 	outerPlanState(mergestate) = ExecInitNode(outerPlan(node), estate, eflags);
+	outerDesc = ExecGetResultType(outerPlanState(mergestate));
 	innerPlanState(mergestate) = ExecInitNode(innerPlan(node), estate,
 											  mergestate->mj_SkipMarkRestore ?
 											  eflags :
 											  (eflags | EXEC_FLAG_MARK));
+	innerDesc = ExecGetResultType(innerPlanState(mergestate));
 
 	/*
 	 * For certain types of inner child nodes, it is advantageous to issue
@@ -1515,13 +1509,24 @@ ExecInitMergeJoin(MergeJoin *node, EState *estate, int eflags)
 		mergestate->mj_ExtraMarks = false;
 
 	/*
+	 * Initialize result slot, type and projection.
+	 */
+	ExecInitResultTupleSlotTL(estate, &mergestate->js.ps);
+	ExecAssignProjectionInfo(&mergestate->js.ps, NULL);
+
+	/*
 	 * tuple table initialization
 	 */
-	ExecInitResultTupleSlot(estate, &mergestate->js.ps);
+	mergestate->mj_MarkedTupleSlot = ExecInitExtraTupleSlot(estate, innerDesc);
 
-	mergestate->mj_MarkedTupleSlot = ExecInitExtraTupleSlot(estate);
-	ExecSetSlotDescriptor(mergestate->mj_MarkedTupleSlot,
-						  ExecGetResultType(innerPlanState(mergestate)));
+	/*
+	 * initialize child expressions
+	 */
+	mergestate->js.ps.qual =
+		ExecInitQual(node->join.plan.qual, (PlanState *) mergestate);
+	mergestate->js.joinqual =
+		ExecInitQual(node->join.joinqual, (PlanState *) mergestate);
+	/* mergeclauses are handled below */
 
 	/*
 	 * detect whether we need only consider the first matching inner tuple
@@ -1542,15 +1547,13 @@ ExecInitMergeJoin(MergeJoin *node, EState *estate, int eflags)
 			mergestate->mj_FillOuter = true;
 			mergestate->mj_FillInner = false;
 			mergestate->mj_NullInnerTupleSlot =
-				ExecInitNullTupleSlot(estate,
-									  ExecGetResultType(innerPlanState(mergestate)));
+				ExecInitNullTupleSlot(estate, innerDesc);
 			break;
 		case JOIN_RIGHT:
 			mergestate->mj_FillOuter = false;
 			mergestate->mj_FillInner = true;
 			mergestate->mj_NullOuterTupleSlot =
-				ExecInitNullTupleSlot(estate,
-									  ExecGetResultType(outerPlanState(mergestate)));
+				ExecInitNullTupleSlot(estate, outerDesc);
 
 			/*
 			 * Can't handle right or full join with non-constant extra
@@ -1566,11 +1569,9 @@ ExecInitMergeJoin(MergeJoin *node, EState *estate, int eflags)
 			mergestate->mj_FillOuter = true;
 			mergestate->mj_FillInner = true;
 			mergestate->mj_NullOuterTupleSlot =
-				ExecInitNullTupleSlot(estate,
-									  ExecGetResultType(outerPlanState(mergestate)));
+				ExecInitNullTupleSlot(estate, outerDesc);
 			mergestate->mj_NullInnerTupleSlot =
-				ExecInitNullTupleSlot(estate,
-									  ExecGetResultType(innerPlanState(mergestate)));
+				ExecInitNullTupleSlot(estate, innerDesc);
 
 			/*
 			 * Can't handle right or full join with non-constant extra
@@ -1588,12 +1589,6 @@ ExecInitMergeJoin(MergeJoin *node, EState *estate, int eflags)
 	}
 
 	/*
-	 * initialize tuple type and projection info
-	 */
-	ExecAssignResultTypeFromTL(&mergestate->js.ps);
-	ExecAssignProjectionInfo(&mergestate->js.ps, NULL);
-
-	/*
 	 * preprocess the merge clauses
 	 */
 	mergestate->mj_NumClauses = list_length(node->mergeclauses);