Rejigger materializing and fetching a HeapTuple from a slot.

Previously materializing a slot always returned a HeapTuple. As
current work aims to reduce the reliance on HeapTuples (so other
storage systems can work efficiently), that needs to change. Thus
split the tasks of materializing a slot (i.e. making it independent
from the underlying storage / other memory contexts) from fetching a
HeapTuple from the slot.  For brevity, allow to fetch a HeapTuple from
a slot and materializing the slot at the same time, controlled by a
parameter.

For now some callers of ExecFetchSlotHeapTuple, with materialize =
true, expect that changes to the heap tuple will be reflected in the
underlying slot.  Those places will be adapted in due course, so while
not pretty, that's OK for now.

Also rename ExecFetchSlotTuple to ExecFetchSlotHeapTupleDatum and
ExecFetchSlotTupleDatum to ExecFetchSlotHeapTupleDatum, as it's likely
that future storage methods will need similar methods. There already
is ExecFetchSlotMinimalTuple, so the new names make the naming scheme
more coherent.

Author: Ashutosh Bapat and Andres Freund, with changes by Amit Khandekar
Discussion: https://postgr.es/m/20181105210039.hh4vvi4vwoq5ba2q@alap3.anarazel.de

1 files changed, 13 insertions, 13 deletions

diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
index 6ef694d5a4a..a3ca336f2ac 100644
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -175,7 +175,7 @@ ExecProcessReturning(ResultRelInfo *resultRelInfo,
 		 * initialize t_tableOid before evaluating them.
 		 */
 		Assert(!TupIsNull(econtext->ecxt_scantuple));
-		tuple = ExecMaterializeSlot(econtext->ecxt_scantuple);
+		tuple = ExecFetchSlotHeapTuple(econtext->ecxt_scantuple, true, NULL);
 		tuple->t_tableOid = RelationGetRelid(resultRelInfo->ri_RelationDesc);
 	}
 	econtext->ecxt_outertuple = planSlot;
@@ -274,7 +274,7 @@ ExecInsert(ModifyTableState *mtstate,
 	 * get the heap tuple out of the tuple table slot, making sure we have a
 	 * writable copy
 	 */
-	tuple = ExecMaterializeSlot(slot);
+	tuple = ExecFetchSlotHeapTuple(slot, true, NULL);
 
 	/*
 	 * get information on the (current) result relation
@@ -315,7 +315,7 @@ ExecInsert(ModifyTableState *mtstate,
 			return NULL;
 
 		/* trigger might have changed tuple */
-		tuple = ExecMaterializeSlot(slot);
+		tuple = ExecFetchSlotHeapTuple(slot, true, NULL);
 	}
 
 	/* INSTEAD OF ROW INSERT Triggers */
@@ -328,7 +328,7 @@ ExecInsert(ModifyTableState *mtstate,
 			return NULL;
 
 		/* trigger might have changed tuple */
-		tuple = ExecMaterializeSlot(slot);
+		tuple = ExecFetchSlotHeapTuple(slot, true, NULL);
 
 		newId = InvalidOid;
 	}
@@ -346,7 +346,7 @@ ExecInsert(ModifyTableState *mtstate,
 			return NULL;
 
 		/* FDW might have changed tuple */
-		tuple = ExecMaterializeSlot(slot);
+		tuple = ExecFetchSlotHeapTuple(slot, true, NULL);
 
 		/*
 		 * AFTER ROW Triggers or RETURNING expressions might reference the
@@ -695,7 +695,7 @@ ExecDelete(ModifyTableState *mtstate,
 		 */
 		if (TTS_EMPTY(slot))
 			ExecStoreAllNullTuple(slot);
-		tuple = ExecMaterializeSlot(slot);
+		tuple = ExecFetchSlotHeapTuple(slot, true, NULL);
 		tuple->t_tableOid = RelationGetRelid(resultRelationDesc);
 	}
 	else
@@ -953,7 +953,7 @@ ExecUpdate(ModifyTableState *mtstate,
 	 * get the heap tuple out of the tuple table slot, making sure we have a
 	 * writable copy
 	 */
-	tuple = ExecMaterializeSlot(slot);
+	tuple = ExecFetchSlotHeapTuple(slot, true, NULL);
 
 	/*
 	 * get information on the (current) result relation
@@ -972,7 +972,7 @@ ExecUpdate(ModifyTableState *mtstate,
 			return NULL;
 
 		/* trigger might have changed tuple */
-		tuple = ExecMaterializeSlot(slot);
+		tuple = ExecFetchSlotHeapTuple(slot, true, NULL);
 	}
 
 	/* INSTEAD OF ROW UPDATE Triggers */
@@ -986,7 +986,7 @@ ExecUpdate(ModifyTableState *mtstate,
 			return NULL;
 
 		/* trigger might have changed tuple */
-		tuple = ExecMaterializeSlot(slot);
+		tuple = ExecFetchSlotHeapTuple(slot, true, NULL);
 	}
 	else if (resultRelInfo->ri_FdwRoutine)
 	{
@@ -1002,7 +1002,7 @@ ExecUpdate(ModifyTableState *mtstate,
 			return NULL;
 
 		/* FDW might have changed tuple */
-		tuple = ExecMaterializeSlot(slot);
+		tuple = ExecFetchSlotHeapTuple(slot, true, NULL);
 
 		/*
 		 * AFTER ROW Triggers or RETURNING expressions might reference the
@@ -1129,7 +1129,7 @@ lreplace:;
 				else
 				{
 					slot = ExecFilterJunk(resultRelInfo->ri_junkFilter, epqslot);
-					tuple = ExecMaterializeSlot(slot);
+					tuple = ExecFetchSlotHeapTuple(slot, true, NULL);
 					goto lreplace;
 				}
 			}
@@ -1268,7 +1268,7 @@ lreplace:;
 					{
 						*tupleid = hufd.ctid;
 						slot = ExecFilterJunk(resultRelInfo->ri_junkFilter, epqslot);
-						tuple = ExecMaterializeSlot(slot);
+						tuple = ExecFetchSlotHeapTuple(slot, true, NULL);
 						goto lreplace;
 					}
 				}
@@ -1739,7 +1739,7 @@ ExecPrepareTupleRouting(ModifyTableState *mtstate,
 	estate->es_result_relation_info = partrel;
 
 	/* Get the heap tuple out of the given slot. */
-	tuple = ExecMaterializeSlot(slot);
+	tuple = ExecFetchSlotHeapTuple(slot, true, NULL);
 
 	/*
 	 * If we're capturing transition tuples, we might need to convert from the