MERGE post-commit review

Review comments from Andres Freund

* Consolidate code into AfterTriggerGetTransitionTable()
* Rename nodeMerge.c to execMerge.c
* Rename nodeMerge.h to execMerge.h
* Move MERGE handling in ExecInitModifyTable()
  into a execMerge.c ExecInitMerge()
* Move mt_merge_subcommands flags into execMerge.h
* Rename opt_and_condition to opt_merge_when_and_condition
* Wordsmith various comments

Author: Pavan Deolasee
Reviewer: Simon Riggs

src/backend/commands/trigger.c

@@ -96,6 +96,12 @@ static HeapTuple ExecCallTriggerFunc(TriggerData *trigdata,
 					FmgrInfo *finfo,
 					Instrumentation *instr,
 					MemoryContext per_tuple_context);
+static Tuplestorestate *AfterTriggerGetTransitionTable(int event,
+					HeapTuple oldtup,
+					HeapTuple newtup,
+					TransitionCaptureState *transition_capture);
+static void TransitionTableAddTuple(HeapTuple heaptup, Tuplestorestate *tuplestore,
+					TupleConversionMap *map);
 static void AfterTriggerSaveEvent(EState *estate, ResultRelInfo *relinfo,
 					  int event, bool row_trigger,
 					  HeapTuple oldtup, HeapTuple newtup,
@@ -3846,6 +3852,14 @@ struct AfterTriggersTableData
 	bool		before_trig_done;	/* did we already queue BS triggers? */
 	bool		after_trig_done;	/* did we already queue AS triggers? */
 	AfterTriggerEventList after_trig_events;	/* if so, saved list pointer */
+
+	/*
+	 * We maintain separate transaction tables for UPDATE/INSERT/DELETE since
+	 * MERGE can run all three actions in a single statement. Note that UPDATE
+	 * needs both old and new transition tables whereas INSERT needs only new
+	 * and DELETE needs only old.
+	 */
+
 	/* "old" transition table for UPDATE, if any */
 	Tuplestorestate *old_upd_tuplestore;
 	/* "new" transition table for UPDATE, if any */
@@ -5716,6 +5730,84 @@ AfterTriggerPendingOnRel(Oid relid)
 	return false;
 }
 
+/*
+ * Get the transition table for the given event and depending on whether we are
+ * processing the old or the new tuple.
+ */
+static Tuplestorestate *
+AfterTriggerGetTransitionTable(int event,
+							   HeapTuple oldtup,
+							   HeapTuple newtup,
+							   TransitionCaptureState *transition_capture)
+{
+	Tuplestorestate	*tuplestore = NULL;
+	bool			delete_old_table = transition_capture->tcs_delete_old_table;
+	bool			update_old_table = transition_capture->tcs_update_old_table;
+	bool			update_new_table = transition_capture->tcs_update_new_table;
+	bool			insert_new_table = transition_capture->tcs_insert_new_table;;
+
+	/*
+	 * For INSERT events newtup should be non-NULL, for DELETE events
+	 * oldtup should be non-NULL, whereas for UPDATE events normally both
+	 * oldtup and newtup are non-NULL.  But for UPDATE events fired for
+	 * capturing transition tuples during UPDATE partition-key row
+	 * movement, oldtup is NULL when the event is for a row being inserted,
+	 * whereas newtup is NULL when the event is for a row being deleted.
+	 */
+	Assert(!(event == TRIGGER_EVENT_DELETE && delete_old_table &&
+				oldtup == NULL));
+	Assert(!(event == TRIGGER_EVENT_INSERT && insert_new_table &&
+				newtup == NULL));
+
+	/*
+	 * We're called either for the newtup or the oldtup, but not both at the
+	 * same time.
+	 */
+	Assert((oldtup != NULL) ^ (newtup != NULL));
+
+	if (oldtup != NULL)
+	{
+		if (event == TRIGGER_EVENT_DELETE && delete_old_table)
+			tuplestore = transition_capture->tcs_private->old_del_tuplestore;
+		else if (event == TRIGGER_EVENT_UPDATE && update_old_table)
+			tuplestore = transition_capture->tcs_private->old_upd_tuplestore;
+	}
+
+	if (newtup != NULL)
+	{
+		if (event == TRIGGER_EVENT_INSERT && insert_new_table)
+			tuplestore = transition_capture->tcs_private->new_ins_tuplestore;
+		else if (event == TRIGGER_EVENT_UPDATE && update_new_table)
+			tuplestore = transition_capture->tcs_private->new_upd_tuplestore;
+	}
+
+	return tuplestore;
+}
+
+/*
+ * Add the given heap tuple to the given tuplestore, applying the conversion
+ * map if necessary.
+ */
+static void
+TransitionTableAddTuple(HeapTuple heaptup, Tuplestorestate *tuplestore,
+						TupleConversionMap *map)
+{
+	/*
+	 * Nothing needs to be done if we don't have a tuplestore.
+	 */
+	if (tuplestore == NULL)
+		return;
+
+	if (map != NULL)
+	{
+		HeapTuple	converted = do_convert_tuple(heaptup, map);
+
+		tuplestore_puttuple(tuplestore, converted);
+		pfree(converted);
+	}
+	else
+		tuplestore_puttuple(tuplestore, heaptup);
+}
 
 /* ----------
  * AfterTriggerSaveEvent()
@@ -5777,95 +5869,37 @@ AfterTriggerSaveEvent(EState *estate, ResultRelInfo *relinfo,
 	{
 		HeapTuple	original_insert_tuple = transition_capture->tcs_original_insert_tuple;
 		TupleConversionMap *map = transition_capture->tcs_map;
-		bool		delete_old_table = transition_capture->tcs_delete_old_table;
-		bool		update_old_table = transition_capture->tcs_update_old_table;
-		bool		update_new_table = transition_capture->tcs_update_new_table;
-		bool		insert_new_table = transition_capture->tcs_insert_new_table;;
 
 		/*
-		 * For INSERT events newtup should be non-NULL, for DELETE events
-		 * oldtup should be non-NULL, whereas for UPDATE events normally both
-		 * oldtup and newtup are non-NULL.  But for UPDATE events fired for
-		 * capturing transition tuples during UPDATE partition-key row
-		 * movement, oldtup is NULL when the event is for a row being inserted,
-		 * whereas newtup is NULL when the event is for a row being deleted.
+		 * Capture the old tuple in the appropriate transition table based on
+		 * the event.
 		 */
-		Assert(!(event == TRIGGER_EVENT_DELETE && delete_old_table &&
-				 oldtup == NULL));
-		Assert(!(event == TRIGGER_EVENT_INSERT && insert_new_table &&
-				 newtup == NULL));
-
-		if (oldtup != NULL &&
-			(event == TRIGGER_EVENT_DELETE && delete_old_table))
+		if (oldtup != NULL)
 		{
-			Tuplestorestate *old_tuplestore;
-
-			old_tuplestore = transition_capture->tcs_private->old_del_tuplestore;
-
-			if (map != NULL)
-			{
-				HeapTuple	converted = do_convert_tuple(oldtup, map);
-
-				tuplestore_puttuple(old_tuplestore, converted);
-				pfree(converted);
-			}
-			else
-				tuplestore_puttuple(old_tuplestore, oldtup);
+			Tuplestorestate *tuplestore =
+				AfterTriggerGetTransitionTable(event,
+											   oldtup,
+											   NULL,
+											   transition_capture);
+			TransitionTableAddTuple(oldtup, tuplestore, map);
 		}
-		if (oldtup != NULL &&
-			 (event == TRIGGER_EVENT_UPDATE && update_old_table))
-		{
-			Tuplestorestate *old_tuplestore;
-
-			old_tuplestore = transition_capture->tcs_private->old_upd_tuplestore;
-
-			if (map != NULL)
-			{
-				HeapTuple	converted = do_convert_tuple(oldtup, map);
 
-				tuplestore_puttuple(old_tuplestore, converted);
-				pfree(converted);
-			}
-			else
-				tuplestore_puttuple(old_tuplestore, oldtup);
-		}
-		if (newtup != NULL &&
-			(event == TRIGGER_EVENT_INSERT && insert_new_table))
-		{
-			Tuplestorestate *new_tuplestore;
-
-			new_tuplestore = transition_capture->tcs_private->new_ins_tuplestore;
-
-			if (original_insert_tuple != NULL)
-				tuplestore_puttuple(new_tuplestore, original_insert_tuple);
-			else if (map != NULL)
-			{
-				HeapTuple	converted = do_convert_tuple(newtup, map);
-
-				tuplestore_puttuple(new_tuplestore, converted);
-				pfree(converted);
-			}
-			else
-				tuplestore_puttuple(new_tuplestore, newtup);
-		}
-		if (newtup != NULL &&
-			(event == TRIGGER_EVENT_UPDATE && update_new_table))
+		/*
+		 * Capture the new tuple in the appropriate transition table based on
+		 * the event.
+		 */
+		if (newtup != NULL)
 		{
-			Tuplestorestate *new_tuplestore;
-
-			new_tuplestore = transition_capture->tcs_private->new_upd_tuplestore;
+			Tuplestorestate *tuplestore =
+				AfterTriggerGetTransitionTable(event,
+											   NULL,
+											   newtup,
+											   transition_capture);
 
 			if (original_insert_tuple != NULL)
-				tuplestore_puttuple(new_tuplestore, original_insert_tuple);
-			else if (map != NULL)
-			{
-				HeapTuple	converted = do_convert_tuple(newtup, map);
-
-				tuplestore_puttuple(new_tuplestore, converted);
-				pfree(converted);
-			}
+				tuplestore_puttuple(tuplestore, original_insert_tuple);
 			else
-				tuplestore_puttuple(new_tuplestore, newtup);
+				TransitionTableAddTuple(newtup, tuplestore, map);
 		}
 
 		/*

src/backend/executor/Makefile

@@ -14,7 +14,7 @@ include $(top_builddir)/src/Makefile.global
 
 OBJS = execAmi.o execCurrent.o execExpr.o execExprInterp.o \
        execGrouping.o execIndexing.o execJunk.o \
-       execMain.o execParallel.o execPartition.o execProcnode.o \
+       execMain.o execMerge.o execParallel.o execPartition.o execProcnode.o \
        execReplication.o execScan.o execSRF.o execTuples.o \
        execUtils.o functions.o instrument.o nodeAppend.o nodeAgg.o \
        nodeBitmapAnd.o nodeBitmapOr.o \
@@ -22,7 +22,7 @@ OBJS = execAmi.o execCurrent.o execExpr.o execExprInterp.o \
        nodeCustom.o nodeFunctionscan.o nodeGather.o \
        nodeHash.o nodeHashjoin.o nodeIndexscan.o nodeIndexonlyscan.o \
        nodeLimit.o nodeLockRows.o nodeGatherMerge.o \
-       nodeMaterial.o nodeMergeAppend.o nodeMergejoin.o nodeMerge.o nodeModifyTable.o \
+       nodeMaterial.o nodeMergeAppend.o nodeMergejoin.o nodeModifyTable.o \
        nodeNestloop.o nodeProjectSet.o nodeRecursiveunion.o nodeResult.o \
        nodeSamplescan.o nodeSeqscan.o nodeSetOp.o nodeSort.o nodeUnique.o \
        nodeValuesscan.o \

src/backend/executor/README

@@ -39,13 +39,14 @@ ModifyTable node visits each of those rows and marks the row deleted.
 
 MERGE runs one generic plan that returns candidate target rows. Each row
 consists of a super-row that contains all the columns needed by any of the
-individual actions, plus a CTID and a TABLEOID junk columns. The CTID column is
+individual actions, plus CTID and TABLEOID junk columns. The CTID column is
 required to know if a matching target row was found or not and the TABLEOID
 column is needed to find the underlying target partition, in case when the
-target table is a partition table. If the CTID column is set we attempt to
-activate WHEN MATCHED actions, or if it is NULL then we will attempt to
-activate WHEN NOT MATCHED actions. Once we know which action is activated we
-form the final result row and apply only those changes.
+target table is a partition table. When a matching target tuple is found, the
+CTID column identifies the matching target tuple and we attempt to activate
+WHEN MATCHED actions. If a matching tuple is not found, then CTID column is
+NULL and we attempt to activate WHEN NOT MATCHED actions. Once we know which
+action is activated we form the final result row and apply only those changes.
 
 XXX a great deal more documentation needs to be written here...
 

src/backend/executor/execPartition.c

@@ -313,6 +313,10 @@ ExecFindPartition(ResultRelInfo *resultRelInfo, PartitionDispatch *pd,
 /*
  * Given OID of the partition leaf, return the index of the leaf in the
  * partition hierarchy.
+ *
+ * NB: This is an O(N) operation. Unfortunately, there are many other problem
+ * areas with more than a handful partitions, so we don't try to optimise this
+ * code right now.
  */
 int
 ExecFindPartitionByOid(PartitionTupleRouting *proute, Oid partoid)
@@ -325,7 +329,10 @@ ExecFindPartitionByOid(PartitionTupleRouting *proute, Oid partoid)
 			break;
 	}
 
-	Assert(i < proute->num_partitions);
+	if (i >= proute->num_partitions)
+		ereport(ERROR,
+				(errcode(ERRCODE_INTERNAL_ERROR),
+				 errmsg("no partition found for OID %u", partoid)));
 	return i;
 }
 

src/backend/executor/nodeModifyTable.c

@@ -42,7 +42,7 @@
 #include "commands/trigger.h"
 #include "executor/execPartition.h"
 #include "executor/executor.h"
-#include "executor/nodeMerge.h"
+#include "executor/execMerge.h"
 #include "executor/nodeModifyTable.h"
 #include "foreign/fdwapi.h"
 #include "miscadmin.h"
@@ -69,11 +69,6 @@ static void ExecSetupChildParentMapForSubplan(ModifyTableState *mtstate);
 static TupleConversionMap *tupconv_map_for_subplan(ModifyTableState *node,
 						int whichplan);
 
-/* flags for mt_merge_subcommands */
-#define MERGE_INSERT	0x01
-#define MERGE_UPDATE	0x02
-#define MERGE_DELETE	0x04
-
 /*
  * Verify that the tuples to be produced by INSERT or UPDATE match the
  * target relation's rowtype
@@ -86,7 +81,7 @@ static TupleConversionMap *tupconv_map_for_subplan(ModifyTableState *node,
  * The plan output is represented by its targetlist, because that makes
  * handling the dropped-column case easier.
  */
-static void
+void
 ExecCheckPlanOutput(Relation resultRel, List *targetList)
 {
 	TupleDesc	resultDesc = RelationGetDescr(resultRel);
@@ -2660,104 +2655,8 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 	}
 
 	resultRelInfo = mtstate->resultRelInfo;
-
-	if (node->mergeActionList)
-	{
-		ListCell   *l;
-		ExprContext *econtext;
-		List	   *mergeMatchedActionStates = NIL;
-		List	   *mergeNotMatchedActionStates = NIL;
-		TupleDesc	relationDesc = resultRelInfo->ri_RelationDesc->rd_att;
-
-		mtstate->mt_merge_subcommands = 0;
-
-		if (mtstate->ps.ps_ExprContext == NULL)
-			ExecAssignExprContext(estate, &mtstate->ps);
-
-		econtext = mtstate->ps.ps_ExprContext;
-
-		/* initialize slot for the existing tuple */
-		Assert(mtstate->mt_existing == NULL);
-		mtstate->mt_existing =
-			ExecInitExtraTupleSlot(mtstate->ps.state,
-								   mtstate->mt_partition_tuple_routing ?
-								   NULL : relationDesc);
-
-		/* initialize slot for merge actions */
-		Assert(mtstate->mt_mergeproj == NULL);
-		mtstate->mt_mergeproj =
-			ExecInitExtraTupleSlot(mtstate->ps.state,
-								   mtstate->mt_partition_tuple_routing ?
-								   NULL : relationDesc);
-
-		/*
-		 * Create a MergeActionState for each action on the mergeActionList
-		 * and add it to either a list of matched actions or not-matched
-		 * actions.
-		 */
-		foreach(l, node->mergeActionList)
-		{
-			MergeAction *action = (MergeAction *) lfirst(l);
-			MergeActionState *action_state = makeNode(MergeActionState);
-			TupleDesc	tupDesc;
-
-			action_state->matched = action->matched;
-			action_state->commandType = action->commandType;
-			action_state->whenqual = ExecInitQual((List *) action->qual,
-					&mtstate->ps);
-
-			/* create target slot for this action's projection */
-			tupDesc = ExecTypeFromTL((List *) action->targetList,
-					resultRelInfo->ri_RelationDesc->rd_rel->relhasoids);
-			action_state->tupDesc = tupDesc;
-
-			/* build action projection state */
-			action_state->proj =
-				ExecBuildProjectionInfo(action->targetList, econtext,
-						mtstate->mt_mergeproj, &mtstate->ps,
-						resultRelInfo->ri_RelationDesc->rd_att);
-
-			/*
-			 * We create two lists - one for WHEN MATCHED actions and one
-			 * for WHEN NOT MATCHED actions - and stick the
-			 * MergeActionState into the appropriate list.
-			 */
-			if (action_state->matched)
-				mergeMatchedActionStates =
-					lappend(mergeMatchedActionStates, action_state);
-			else
-				mergeNotMatchedActionStates =
-					lappend(mergeNotMatchedActionStates, action_state);
-
-			switch (action->commandType)
-			{
-				case CMD_INSERT:
-					ExecCheckPlanOutput(resultRelInfo->ri_RelationDesc,
-										action->targetList);
-					mtstate->mt_merge_subcommands |= MERGE_INSERT;
-					break;
-				case CMD_UPDATE:
-					ExecCheckPlanOutput(resultRelInfo->ri_RelationDesc,
-										action->targetList);
-					mtstate->mt_merge_subcommands |= MERGE_UPDATE;
-					break;
-				case CMD_DELETE:
-					mtstate->mt_merge_subcommands |= MERGE_DELETE;
-					break;
-				case CMD_NOTHING:
-					break;
-				default:
-					elog(ERROR, "unknown operation");
-					break;
-			}
-
-			resultRelInfo->ri_mergeState->matchedActionStates =
-						mergeMatchedActionStates;
-			resultRelInfo->ri_mergeState->notMatchedActionStates =
-						mergeNotMatchedActionStates;
-
-		}
-	}
+	if (mtstate->operation == CMD_MERGE)
+		ExecInitMerge(mtstate, estate, resultRelInfo);
 
 	/* select first subplan */
 	mtstate->mt_whichplan = 0;

src/backend/optimizer/plan/setrefs.c

@@ -852,14 +852,14 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 				}
 
 				/*
-				 * The MERGE produces the target rows by performing a right
-				 * join between the target relation and the source relation
-				 * (which could be a plain relation or a subquery). The INSERT
-				 * and UPDATE actions of the MERGE requires access to the
-				 * columns from the source relation. We arrange things so that
-				 * the source relation attributes are available as INNER_VAR
-				 * and the target relation attributes are available from the
-				 * scan tuple.
+				 * The MERGE statement produces the target rows by performing a
+				 * right join between the target relation and the source
+				 * relation (which could be a plain relation or a subquery).
+				 * The INSERT and UPDATE actions of the MERGE statement
+				 * requires access to the columns from the source relation. We
+				 * arrange things so that the source relation attributes are
+				 * available as INNER_VAR and the target relation attributes
+				 * are available from the scan tuple.
 				 */
 				if (splan->mergeActionList != NIL)
 				{

src/backend/parser/gram.y

@@ -585,7 +585,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>		hash_partbound partbound_datum_list range_datum_list
 %type <defelt>		hash_partbound_elem
 
-%type <node>	merge_when_clause opt_and_condition
+%type <node>	merge_when_clause opt_merge_when_and_condition
 %type <list>	merge_when_list
 %type <node>	merge_update merge_delete merge_insert
 
@@ -11129,7 +11129,7 @@ merge_when_list:
 			;
 
 merge_when_clause:
-			WHEN MATCHED opt_and_condition THEN merge_update
+			WHEN MATCHED opt_merge_when_and_condition THEN merge_update
 				{
 					MergeAction *m = makeNode(MergeAction);
 
@@ -11140,7 +11140,7 @@ merge_when_clause:
 
 					$$ = (Node *)m;
 				}
-			| WHEN MATCHED opt_and_condition THEN merge_delete
+			| WHEN MATCHED opt_merge_when_and_condition THEN merge_delete
 				{
 					MergeAction *m = makeNode(MergeAction);
 
@@ -11151,7 +11151,7 @@ merge_when_clause:
 
 					$$ = (Node *)m;
 				}
-			| WHEN NOT MATCHED opt_and_condition THEN merge_insert
+			| WHEN NOT MATCHED opt_merge_when_and_condition THEN merge_insert
 				{
 					MergeAction *m = makeNode(MergeAction);
 
@@ -11162,7 +11162,7 @@ merge_when_clause:
 
 					$$ = (Node *)m;
 				}
-			| WHEN NOT MATCHED opt_and_condition THEN DO NOTHING
+			| WHEN NOT MATCHED opt_merge_when_and_condition THEN DO NOTHING
 				{
 					MergeAction *m = makeNode(MergeAction);
 
@@ -11175,7 +11175,7 @@ merge_when_clause:
 				}
 			;
 
-opt_and_condition:
+opt_merge_when_and_condition:
 			AND a_expr 				{ $$ = $2; }
 			| 			 			{ $$ = NULL; }
 			;

src/include/executor/nodeMerge.h → src/include/executor/execMerge.h

 /*-------------------------------------------------------------------------
  *
- * nodeMerge.h
+ * execMerge.h
  *
  *
  * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * src/include/executor/nodeMerge.h
+ * src/include/executor/execMerge.h
  *
  *-------------------------------------------------------------------------
  */
-#ifndef NODEMERGE_H
-#define NODEMERGE_H
+#ifndef EXECMERGE_H
+#define EXECMERGE_H
 
 #include "nodes/execnodes.h"
 
-extern void
-ExecMerge(ModifyTableState *mtstate, EState *estate, TupleTableSlot *slot,
-		  JunkFilter *junkfilter, ResultRelInfo *resultRelInfo);
+/* flags for mt_merge_subcommands */
+#define MERGE_INSERT	0x01
+#define MERGE_UPDATE	0x02
+#define MERGE_DELETE	0x04
+
+extern void ExecMerge(ModifyTableState *mtstate, EState *estate,
+					  TupleTableSlot *slot, JunkFilter *junkfilter,
+					  ResultRelInfo *resultRelInfo);
+
+extern void ExecInitMerge(ModifyTableState *mtstate,
+						  EState *estate,
+						  ResultRelInfo *resultRelInfo);
 
 #endif							/* NODEMERGE_H */

src/include/executor/nodeModifyTable.h

@@ -39,5 +39,6 @@ extern TupleTableSlot *ExecInsert(ModifyTableState *mtstate,
 		   EState *estate,
 		   MergeActionState *actionState,
 		   bool canSetTag);
+extern void ExecCheckPlanOutput(Relation resultRel, List *targetList);
 
 #endif							/* NODEMODIFYTABLE_H */