Use slots in trigger infrastructure, except for the actual invocation.

In preparation for abstracting table storage, convert trigger.c to
track tuples in slots. Which also happens to make code calling
triggers simpler.

As the calling interface for triggers themselves is not changed in
this patch, HeapTuples still are extracted from the slot at that
time. But that's handled solely inside trigger.c, not visible to
callers. It's quite likely that we'll want to revise the external
trigger interface, but that's a separate large project.

As part of this work the slots used for old/new/return tuples are
moved from EState into ResultRelInfo, as different updated tables
might need different slots. The slots are now also now created
on-demand, which is good both from an efficiency POV, but also makes
the modifying code simpler.

Author: Andres Freund, Amit Khandekar and Ashutosh Bapat
Discussion: https://postgr.es/m/20180703070645.wchpu5muyto5n647@alap3.anarazel.de

1 files changed, 66 insertions, 3 deletions

diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c
index 312a0dc8056..51362693481 100644
--- a/src/backend/executor/execUtils.c
+++ b/src/backend/executor/execUtils.c
@@ -131,9 +131,6 @@ CreateExecutorState(void)
 	estate->es_tuple_routing_result_relations = NIL;
 
 	estate->es_trig_target_relations = NIL;
-	estate->es_trig_tuple_slot = NULL;
-	estate->es_trig_oldtup_slot = NULL;
-	estate->es_trig_newtup_slot = NULL;
 
 	estate->es_param_list_info = NULL;
 	estate->es_param_exec_vals = NULL;
@@ -1102,3 +1099,69 @@ ExecCleanTargetListLength(List *targetlist)
 	}
 	return len;
 }
+
+/*
+ * Return a relInfo's tuple slot for a trigger's OLD tuples.
+ */
+TupleTableSlot *
+ExecGetTriggerOldSlot(EState *estate, ResultRelInfo *relInfo)
+{
+	if (relInfo->ri_TrigOldSlot == NULL)
+	{
+		Relation	rel = relInfo->ri_RelationDesc;
+		MemoryContext oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
+
+		relInfo->ri_TrigOldSlot =
+			ExecInitExtraTupleSlot(estate,
+								   RelationGetDescr(rel),
+								   &TTSOpsBufferHeapTuple);
+
+		MemoryContextSwitchTo(oldcontext);
+	}
+
+	return relInfo->ri_TrigOldSlot;
+}
+
+/*
+ * Return a relInfo's tuple slot for a trigger's NEW tuples.
+ */
+TupleTableSlot *
+ExecGetTriggerNewSlot(EState *estate, ResultRelInfo *relInfo)
+{
+	if (relInfo->ri_TrigNewSlot == NULL)
+	{
+		Relation	rel = relInfo->ri_RelationDesc;
+		MemoryContext oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
+
+		relInfo->ri_TrigNewSlot =
+			ExecInitExtraTupleSlot(estate,
+								   RelationGetDescr(rel),
+								   &TTSOpsBufferHeapTuple);
+
+		MemoryContextSwitchTo(oldcontext);
+	}
+
+	return relInfo->ri_TrigNewSlot;
+}
+
+/*
+ * Return a relInfo's tuple slot for processing returning tuples.
+ */
+TupleTableSlot *
+ExecGetReturningSlot(EState *estate, ResultRelInfo *relInfo)
+{
+	if (relInfo->ri_ReturningSlot == NULL)
+	{
+		Relation	rel = relInfo->ri_RelationDesc;
+		MemoryContext oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
+
+		relInfo->ri_ReturningSlot =
+			ExecInitExtraTupleSlot(estate,
+								   RelationGetDescr(rel),
+								   &TTSOpsBufferHeapTuple);
+
+		MemoryContextSwitchTo(oldcontext);
+	}
+
+	return relInfo->ri_ReturningSlot;
+}