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

2 files changed, 8 insertions, 8 deletions

diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 621e7c3dc46..45a077a949c 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -431,9 +431,10 @@ extern void ExecScanReScan(ScanState *node);
 /*
  * prototypes from functions in execTuples.c
  */
-extern void ExecInitResultTupleSlot(EState *estate, PlanState *planstate);
-extern void ExecInitScanTupleSlot(EState *estate, ScanState *scanstate);
-extern TupleTableSlot *ExecInitExtraTupleSlot(EState *estate);
+extern void ExecInitResultTupleSlotTL(EState *estate, PlanState *planstate);
+extern void ExecInitScanTupleSlot(EState *estate, ScanState *scanstate, TupleDesc tupleDesc);
+extern TupleTableSlot *ExecInitExtraTupleSlot(EState *estate,
+					  TupleDesc tupleDesc);
 extern TupleTableSlot *ExecInitNullTupleSlot(EState *estate,
 					  TupleDesc tupType);
 extern TupleDesc ExecTypeFromTL(List *targetList, bool hasoid);
@@ -502,8 +503,6 @@ extern ExprContext *MakePerTupleExprContext(EState *estate);
 	} while (0)
 
 extern void ExecAssignExprContext(EState *estate, PlanState *planstate);
-extern void ExecAssignResultType(PlanState *planstate, TupleDesc tupDesc);
-extern void ExecAssignResultTypeFromTL(PlanState *planstate);
 extern TupleDesc ExecGetResultType(PlanState *planstate);
 extern void ExecAssignProjectionInfo(PlanState *planstate,
 						 TupleDesc inputDesc);
@@ -511,7 +510,7 @@ extern void ExecConditionalAssignProjectionInfo(PlanState *planstate,
 									TupleDesc inputDesc, Index varno);
 extern void ExecFreeExprContext(PlanState *planstate);
 extern void ExecAssignScanType(ScanState *scanstate, TupleDesc tupDesc);
-extern void ExecAssignScanTypeFromOuterPlan(ScanState *scanstate);
+extern void ExecCreateScanSlotFromOuterPlan(EState *estate, ScanState *scanstate);
 
 extern bool ExecRelationIsTargetRelation(EState *estate, Index scanrelid);
 
diff --git a/src/include/executor/tuptable.h b/src/include/executor/tuptable.h
index 5b54834d33e..8be0d5edc29 100644
--- a/src/include/executor/tuptable.h
+++ b/src/include/executor/tuptable.h
@@ -127,6 +127,7 @@ typedef struct TupleTableSlot
 	MinimalTuple tts_mintuple;	/* minimal tuple, or NULL if none */
 	HeapTupleData tts_minhdr;	/* workspace for minimal-tuple-only case */
 	long		tts_off;		/* saved state for slot_deform_tuple */
+	bool		tts_fixedTupleDescriptor; /* descriptor can't be changed */
 } TupleTableSlot;
 
 #define TTS_HAS_PHYSICAL_TUPLE(slot)  \
@@ -139,8 +140,8 @@ typedef struct TupleTableSlot
 	((slot) == NULL || (slot)->tts_isempty)
 
 /* in executor/execTuples.c */
-extern TupleTableSlot *MakeTupleTableSlot(void);
-extern TupleTableSlot *ExecAllocTableSlot(List **tupleTable);
+extern TupleTableSlot *MakeTupleTableSlot(TupleDesc desc);
+extern TupleTableSlot *ExecAllocTableSlot(List **tupleTable, TupleDesc desc);
 extern void ExecResetTupleTable(List *tupleTable, bool shouldFree);
 extern TupleTableSlot *MakeSingleTupleTableSlot(TupleDesc tupdesc);
 extern void ExecDropSingleTupleTableSlot(TupleTableSlot *slot);