Be lazier about partition tuple routing.

It's not necessary to fully initialize the executor data structures
for partitions to which no tuples are ever routed.  Consider, for
example, an INSERT statement that inserts only one row: it only cares
about the partition to which that one row is routed.  The new function
ExecInitPartitionInfo performs the initialization in question only
when a particular partition is about to receive a tuple. This includes
creating, validating, and saving a pointer to the ResultRelInfo,
setting up for speculative insertions, translating WCOs and
initializing the resulting expressions, translating returning lists
and building the appropriate projection information, and setting up a
tuple conversion map.

One thing that's not deferred is locking the child partitions; that
seems desirable but would need more thought.  Still, testing shows
that this makes single-row inserts significantly faster on a table
with many partitions without harming the bulk-insert case.

Amit Langote, reviewed by Etsuro Fujita, with a few changes by me

Discussion: http://postgr.es/m/8975331d-d961-cbdd-f862-fdd3d97dc2d0@lab.ntt.co.jp

src/backend/commands/copy.c

@@ -2469,7 +2469,7 @@ CopyFrom(CopyState cstate)
 		PartitionTupleRouting *proute;
 
 		proute = cstate->partition_tuple_routing =
-			ExecSetupPartitionTupleRouting(NULL, cstate->rel, 1, estate);
+			ExecSetupPartitionTupleRouting(NULL, cstate->rel);
 
 		/*
 		 * If we are capturing transition tuples, they may need to be
@@ -2606,6 +2606,14 @@ CopyFrom(CopyState cstate)
 			 */
 			saved_resultRelInfo = resultRelInfo;
 			resultRelInfo = proute->partitions[leaf_part_index];
+			if (resultRelInfo == NULL)
+			{
+				resultRelInfo = ExecInitPartitionInfo(NULL,
+													  saved_resultRelInfo,
+													  proute, estate,
+													  leaf_part_index);
+				Assert(resultRelInfo != NULL);
+			}
 
 			/* We do not yet have a way to insert into a foreign partition */
 			if (resultRelInfo->ri_FdwRoutine)

src/backend/executor/execPartition.c

@@ -44,21 +44,25 @@ static char *ExecBuildSlotPartitionKeyDescription(Relation rel,
  *
  * Note that all the relations in the partition tree are locked using the
  * RowExclusiveLock mode upon return from this function.
+ *
+ * While we allocate the arrays of pointers of ResultRelInfo and
+ * TupleConversionMap for all partitions here, actual objects themselves are
+ * lazily allocated for a given partition if a tuple is actually routed to it;
+ * see ExecInitPartitionInfo.  However, if the function is invoked for update
+ * tuple routing, caller would already have initialized ResultRelInfo's for
+ * some of the partitions, which are reused and assigned to their respective
+ * slot in the aforementioned array.
  */
 PartitionTupleRouting *
-ExecSetupPartitionTupleRouting(ModifyTableState *mtstate,
-							   Relation rel, Index resultRTindex,
-							   EState *estate)
+ExecSetupPartitionTupleRouting(ModifyTableState *mtstate, Relation rel)
 {
 	TupleDesc	tupDesc = RelationGetDescr(rel);
 	List	   *leaf_parts;
 	ListCell   *cell;
 	int			i;
-	ResultRelInfo *leaf_part_arr = NULL,
-			   *update_rri = NULL;
+	ResultRelInfo *update_rri = NULL;
 	int			num_update_rri = 0,
 				update_rri_index = 0;
-	bool		is_update = false;
 	PartitionTupleRouting *proute;
 
 	/*
@@ -76,13 +80,14 @@ ExecSetupPartitionTupleRouting(ModifyTableState *mtstate,
 	proute->parent_child_tupconv_maps =
 		(TupleConversionMap **) palloc0(proute->num_partitions *
 										sizeof(TupleConversionMap *));
+	proute->partition_oids = (Oid *) palloc(proute->num_partitions *
+											sizeof(Oid));
 
 	/* Set up details specific to the type of tuple routing we are doing. */
 	if (mtstate && mtstate->operation == CMD_UPDATE)
 	{
 		ModifyTable *node = (ModifyTable *) mtstate->ps.plan;
 
-		is_update = true;
 		update_rri = mtstate->resultRelInfo;
 		num_update_rri = list_length(node->plans);
 		proute->subplan_partition_offsets =
@@ -95,16 +100,6 @@ ExecSetupPartitionTupleRouting(ModifyTableState *mtstate,
 		 */
 		proute->root_tuple_slot = MakeTupleTableSlot(NULL);
 	}
-	else
-	{
-		/*
-		 * Since we are inserting tuples, we need to create all new result
-		 * rels. Avoid repeated pallocs by allocating memory for all the
-		 * result rels in bulk.
-		 */
-		leaf_part_arr = (ResultRelInfo *) palloc0(proute->num_partitions *
-												  sizeof(ResultRelInfo));
-	}
 
 	/*
 	 * Initialize an empty slot that will be used to manipulate tuples of any
@@ -117,33 +112,33 @@ ExecSetupPartitionTupleRouting(ModifyTableState *mtstate,
 	i = 0;
 	foreach(cell, leaf_parts)
 	{
-		ResultRelInfo *leaf_part_rri;
-		Relation	partrel = NULL;
-		TupleDesc	part_tupdesc;
+		ResultRelInfo *leaf_part_rri = NULL;
 		Oid			leaf_oid = lfirst_oid(cell);
 
-		if (is_update)
-		{
+		proute->partition_oids[i] = leaf_oid;
+
 		/*
-			 * If the leaf partition is already present in the per-subplan
-			 * result rels, we re-use that rather than initialize a new result
-			 * rel. The per-subplan resultrels and the resultrels of the leaf
-			 * partitions are both in the same canonical order. So while going
-			 * through the leaf partition oids, we need to keep track of the
-			 * next per-subplan result rel to be looked for in the leaf
-			 * partition resultrels.
+		 * If the leaf partition is already present in the per-subplan result
+		 * rels, we re-use that rather than initialize a new result rel. The
+		 * per-subplan resultrels and the resultrels of the leaf partitions
+		 * are both in the same canonical order. So while going through the
+		 * leaf partition oids, we need to keep track of the next per-subplan
+		 * result rel to be looked for in the leaf partition resultrels.
 		 */
 		if (update_rri_index < num_update_rri &&
 			RelationGetRelid(update_rri[update_rri_index].ri_RelationDesc) == leaf_oid)
 		{
+			Relation	partrel;
+			TupleDesc	part_tupdesc;
+
 			leaf_part_rri = &update_rri[update_rri_index];
 			partrel = leaf_part_rri->ri_RelationDesc;
 
 			/*
-				 * This is required in order to convert the partition's tuple
-				 * to be compatible with the root partitioned table's tuple
-				 * descriptor.  When generating the per-subplan result rels,
-				 * this was not set.
+			 * This is required in order to convert the partition's tuple to
+			 * be compatible with the root partitioned table's tuple
+			 * descriptor.  When generating the per-subplan result rels, this
+			 * was not set.
 			 */
 			leaf_part_rri->ri_PartitionRoot = rel;
 
@@ -151,43 +146,6 @@ ExecSetupPartitionTupleRouting(ModifyTableState *mtstate,
 			proute->subplan_partition_offsets[update_rri_index] = i;
 
 			update_rri_index++;
-			}
-			else
-				leaf_part_rri = (ResultRelInfo *) palloc0(sizeof(ResultRelInfo));
-		}
-		else
-		{
-			/* For INSERTs, we already have an array of result rels allocated */
-			leaf_part_rri = &leaf_part_arr[i];
-		}
-
-		/*
-		 * If we didn't open the partition rel, it means we haven't
-		 * initialized the result rel either.
-		 */
-		if (!partrel)
-		{
-			/*
-			 * We locked all the partitions above including the leaf
-			 * partitions. Note that each of the newly opened relations in
-			 * proute->partitions are eventually closed by the caller.
-			 */
-			partrel = heap_open(leaf_oid, NoLock);
-			InitResultRelInfo(leaf_part_rri,
-							  partrel,
-							  resultRTindex,
-							  rel,
-							  estate->es_instrument);
-
-			/*
-			 * Since we've just initialized this ResultRelInfo, it's not in
-			 * any list attached to the estate as yet.  Add it, so that it can
-			 * be found later.
-			 */
-			estate->es_tuple_routing_result_relations =
-						lappend(estate->es_tuple_routing_result_relations,
-								leaf_part_rri);
-		}
 
 			part_tupdesc = RelationGetDescr(partrel);
 
@@ -200,24 +158,12 @@ ExecSetupPartitionTupleRouting(ModifyTableState *mtstate,
 									   gettext_noop("could not convert row type"));
 
 			/*
-		 * Verify result relation is a valid target for an INSERT.  An UPDATE
-		 * of a partition-key becomes a DELETE+INSERT operation, so this check
-		 * is still required when the operation is CMD_UPDATE.
+			 * Verify result relation is a valid target for an INSERT.  An
+			 * UPDATE of a partition-key becomes a DELETE+INSERT operation, so
+			 * this check is required even when the operation is CMD_UPDATE.
 			 */
 			CheckValidResultRel(leaf_part_rri, CMD_INSERT);
-
-		/*
-		 * Open partition indices.  The user may have asked to check for
-		 * conflicts within this leaf partition and do "nothing" instead of
-		 * throwing an error.  Be prepared in that case by initializing the
-		 * index information needed by ExecInsert() to perform speculative
-		 * insertions.
-		 */
-		if (leaf_part_rri->ri_RelationDesc->rd_rel->relhasindex &&
-			leaf_part_rri->ri_IndexRelationDescs == NULL)
-			ExecOpenIndices(leaf_part_rri,
-							mtstate != NULL &&
-							mtstate->mt_onconflict != ONCONFLICT_NONE);
+		}
 
 		proute->partitions[i] = leaf_part_rri;
 		i++;
@@ -225,9 +171,9 @@ ExecSetupPartitionTupleRouting(ModifyTableState *mtstate,
 
 	/*
 	 * For UPDATE, we should have found all the per-subplan resultrels in the
-	 * leaf partitions.
+	 * leaf partitions.  (If this is an INSERT, both values will be zero.)
 	 */
-	Assert(!is_update || update_rri_index == num_update_rri);
+	Assert(update_rri_index == num_update_rri);
 
 	return proute;
 }
@@ -351,6 +297,201 @@ ExecFindPartition(ResultRelInfo *resultRelInfo, PartitionDispatch *pd,
 	return result;
 }
 
+/*
+ * ExecInitPartitionInfo
+ *		Initialize ResultRelInfo and other information for a partition if not
+ *		already done
+ *
+ * Returns the ResultRelInfo
+ */
+ResultRelInfo *
+ExecInitPartitionInfo(ModifyTableState *mtstate,
+					  ResultRelInfo *resultRelInfo,
+					  PartitionTupleRouting *proute,
+					  EState *estate, int partidx)
+{
+	Relation	rootrel = resultRelInfo->ri_RelationDesc,
+				partrel;
+	ResultRelInfo *leaf_part_rri;
+	ModifyTable *node = mtstate ? (ModifyTable *) mtstate->ps.plan : NULL;
+	MemoryContext oldContext;
+
+	/*
+	 * We locked all the partitions in ExecSetupPartitionTupleRouting
+	 * including the leaf partitions.
+	 */
+	partrel = heap_open(proute->partition_oids[partidx], NoLock);
+
+	/*
+	 * Keep ResultRelInfo and other information for this partition in the
+	 * per-query memory context so they'll survive throughout the query.
+	 */
+	oldContext = MemoryContextSwitchTo(estate->es_query_cxt);
+
+	leaf_part_rri = (ResultRelInfo *) palloc0(sizeof(ResultRelInfo));
+	InitResultRelInfo(leaf_part_rri,
+					  partrel,
+					  node ? node->nominalRelation : 1,
+					  rootrel,
+					  estate->es_instrument);
+
+	/*
+	 * Verify result relation is a valid target for an INSERT.  An UPDATE of a
+	 * partition-key becomes a DELETE+INSERT operation, so this check is still
+	 * required when the operation is CMD_UPDATE.
+	 */
+	CheckValidResultRel(leaf_part_rri, CMD_INSERT);
+
+	/*
+	 * Since we've just initialized this ResultRelInfo, it's not in any list
+	 * attached to the estate as yet.  Add it, so that it can be found later.
+	 *
+	 * Note that the entries in this list appear in no predetermined order,
+	 * because partition result rels are initialized as and when they're
+	 * needed.
+	 */
+	estate->es_tuple_routing_result_relations =
+		lappend(estate->es_tuple_routing_result_relations,
+				leaf_part_rri);
+
+	/*
+	 * Open partition indices.  The user may have asked to check for conflicts
+	 * within this leaf partition and do "nothing" instead of throwing an
+	 * error.  Be prepared in that case by initializing the index information
+	 * needed by ExecInsert() to perform speculative insertions.
+	 */
+	if (partrel->rd_rel->relhasindex &&
+		leaf_part_rri->ri_IndexRelationDescs == NULL)
+		ExecOpenIndices(leaf_part_rri,
+						(mtstate != NULL &&
+						 mtstate->mt_onconflict != ONCONFLICT_NONE));
+
+	/*
+	 * Build WITH CHECK OPTION constraints for the partition.  Note that we
+	 * didn't build the withCheckOptionList for partitions within the planner,
+	 * but simple translation of varattnos will suffice.  This only occurs for
+	 * the INSERT case or in the case of UPDATE tuple routing where we didn't
+	 * find a result rel to reuse in ExecSetupPartitionTupleRouting().
+	 */
+	if (node && node->withCheckOptionLists != NIL)
+	{
+		List	   *wcoList;
+		List	   *wcoExprs = NIL;
+		ListCell   *ll;
+		int			firstVarno = mtstate->resultRelInfo[0].ri_RangeTableIndex;
+		Relation	firstResultRel = mtstate->resultRelInfo[0].ri_RelationDesc;
+
+		/*
+		 * In the case of INSERT on a partitioned table, there is only one
+		 * plan.  Likewise, there is only one WCO list, not one per partition.
+		 * For UPDATE, there are as many WCO lists as there are plans.
+		 */
+		Assert((node->operation == CMD_INSERT &&
+				list_length(node->withCheckOptionLists) == 1 &&
+				list_length(node->plans) == 1) ||
+			   (node->operation == CMD_UPDATE &&
+				list_length(node->withCheckOptionLists) ==
+				list_length(node->plans)));
+
+		/*
+		 * Use the WCO list of the first plan as a reference to calculate
+		 * attno's for the WCO list of this partition.  In the INSERT case,
+		 * that refers to the root partitioned table, whereas in the UPDATE
+		 * tuple routing case, that refers to the first partition in the
+		 * mtstate->resultRelInfo array.  In any case, both that relation and
+		 * this partition should have the same columns, so we should be able
+		 * to map attributes successfully.
+		 */
+		wcoList = linitial(node->withCheckOptionLists);
+
+		/*
+		 * Convert Vars in it to contain this partition's attribute numbers.
+		 */
+		wcoList = map_partition_varattnos(wcoList, firstVarno,
+										  partrel, firstResultRel, NULL);
+		foreach(ll, wcoList)
+		{
+			WithCheckOption *wco = castNode(WithCheckOption, lfirst(ll));
+			ExprState  *wcoExpr = ExecInitQual(castNode(List, wco->qual),
+											   mtstate->mt_plans[0]);
+
+			wcoExprs = lappend(wcoExprs, wcoExpr);
+		}
+
+		leaf_part_rri->ri_WithCheckOptions = wcoList;
+		leaf_part_rri->ri_WithCheckOptionExprs = wcoExprs;
+	}
+
+	/*
+	 * Build the RETURNING projection for the partition.  Note that we didn't
+	 * build the returningList for partitions within the planner, but simple
+	 * translation of varattnos will suffice.  This only occurs for the INSERT
+	 * case or in the case of UPDATE tuple routing where we didn't find a
+	 * result rel to reuse in ExecSetupPartitionTupleRouting().
+	 */
+	if (node && node->returningLists != NIL)
+	{
+		TupleTableSlot *slot;
+		ExprContext *econtext;
+		List	   *returningList;
+		int			firstVarno = mtstate->resultRelInfo[0].ri_RangeTableIndex;
+		Relation	firstResultRel = mtstate->resultRelInfo[0].ri_RelationDesc;
+
+		/* See the comment above for WCO lists. */
+		Assert((node->operation == CMD_INSERT &&
+				list_length(node->returningLists) == 1 &&
+				list_length(node->plans) == 1) ||
+			   (node->operation == CMD_UPDATE &&
+				list_length(node->returningLists) ==
+				list_length(node->plans)));
+
+		/*
+		 * Use the RETURNING list of the first plan as a reference to
+		 * calculate attno's for the RETURNING list of this partition.  See
+		 * the comment above for WCO lists for more details on why this is
+		 * okay.
+		 */
+		returningList = linitial(node->returningLists);
+
+		/*
+		 * Convert Vars in it to contain this partition's attribute numbers.
+		 */
+		returningList = map_partition_varattnos(returningList, firstVarno,
+												partrel, firstResultRel,
+												NULL);
+
+		/*
+		 * Initialize the projection itself.
+		 *
+		 * Use the slot and the expression context that would have been set up
+		 * in ExecInitModifyTable() for projection's output.
+		 */
+		Assert(mtstate->ps.ps_ResultTupleSlot != NULL);
+		slot = mtstate->ps.ps_ResultTupleSlot;
+		Assert(mtstate->ps.ps_ExprContext != NULL);
+		econtext = mtstate->ps.ps_ExprContext;
+		leaf_part_rri->ri_projectReturning =
+			ExecBuildProjectionInfo(returningList, econtext, slot,
+									&mtstate->ps, RelationGetDescr(partrel));
+	}
+
+	Assert(proute->partitions[partidx] == NULL);
+	proute->partitions[partidx] = leaf_part_rri;
+
+	/*
+	 * Save a tuple conversion map to convert a tuple routed to this partition
+	 * from the parent's type to the partition's.
+	 */
+	proute->parent_child_tupconv_maps[partidx] =
+		convert_tuples_by_name(RelationGetDescr(rootrel),
+							   RelationGetDescr(partrel),
+							   gettext_noop("could not convert row type"));
+
+	MemoryContextSwitchTo(oldContext);
+
+	return leaf_part_rri;
+}
+
 /*
  * ExecSetupChildParentMapForLeaf -- Initialize the per-leaf-partition
  * child-to-root tuple conversion map array.
@@ -477,6 +618,10 @@ ExecCleanupTupleRouting(PartitionTupleRouting *proute)
 	{
 		ResultRelInfo *resultRelInfo = proute->partitions[i];
 
+		/* skip further processsing for uninitialized partitions */
+		if (resultRelInfo == NULL)
+			continue;
+
 		/*
 		 * If this result rel is one of the UPDATE subplan result rels, let
 		 * ExecEndPlan() close it. For INSERT or COPY,

src/backend/executor/nodeModifyTable.c

@@ -306,10 +306,18 @@ ExecInsert(ModifyTableState *mtstate,
 
 		/*
 		 * Save the old ResultRelInfo and switch to the one corresponding to
-		 * the selected partition.
+		 * the selected partition.  (We might need to initialize it first.)
 		 */
 		saved_resultRelInfo = resultRelInfo;
 		resultRelInfo = proute->partitions[leaf_part_index];
+		if (resultRelInfo == NULL)
+		{
+			resultRelInfo = ExecInitPartitionInfo(mtstate,
+												  saved_resultRelInfo,
+												  proute, estate,
+												  leaf_part_index);
+			Assert(resultRelInfo != NULL);
+		}
 
 		/* We do not yet have a way to insert into a foreign partition */
 		if (resultRelInfo->ri_FdwRoutine)
@@ -2098,14 +2106,10 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 	ResultRelInfo *saved_resultRelInfo;
 	ResultRelInfo *resultRelInfo;
 	Plan	   *subplan;
-	int			firstVarno = 0;
-	Relation	firstResultRel = NULL;
 	ListCell   *l;
 	int			i;
 	Relation	rel;
 	bool		update_tuple_routing_needed = node->partColsUpdated;
-	PartitionTupleRouting *proute = NULL;
-	int			num_partitions = 0;
 
 	/* check for unsupported flags */
 	Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
@@ -2228,20 +2232,8 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 	 */
 	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE &&
 		(operation == CMD_INSERT || update_tuple_routing_needed))
-	{
-		proute = mtstate->mt_partition_tuple_routing =
-			ExecSetupPartitionTupleRouting(mtstate,
-										   rel, node->nominalRelation,
-										   estate);
-		num_partitions = proute->num_partitions;
-
-		/*
-		 * Below are required as reference objects for mapping partition
-		 * attno's in expressions such as WithCheckOptions and RETURNING.
-		 */
-		firstVarno = mtstate->resultRelInfo[0].ri_RangeTableIndex;
-		firstResultRel = mtstate->resultRelInfo[0].ri_RelationDesc;
-	}
+		mtstate->mt_partition_tuple_routing =
+						ExecSetupPartitionTupleRouting(mtstate, rel);
 
 	/*
 	 * Build state for collecting transition tuples.  This requires having a
@@ -2287,70 +2279,6 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 		i++;
 	}
 
-	/*
-	 * Build WITH CHECK OPTION constraints for each leaf partition rel. Note
-	 * that we didn't build the withCheckOptionList for each partition within
-	 * the planner, but simple translation of the varattnos for each partition
-	 * will suffice.  This only occurs for the INSERT case or for UPDATE row
-	 * movement. DELETEs and local UPDATEs are handled above.
-	 */
-	if (node->withCheckOptionLists != NIL && num_partitions > 0)
-	{
-		List	   *first_wcoList;
-
-		/*
-		 * In case of INSERT on partitioned tables, there is only one plan.
-		 * Likewise, there is only one WITH CHECK OPTIONS list, not one per
-		 * partition. Whereas for UPDATE, there are as many WCOs as there are
-		 * plans. So in either case, use the WCO expression of the first
-		 * resultRelInfo as a reference to calculate attno's for the WCO
-		 * expression of each of the partitions. We make a copy of the WCO
-		 * qual for each partition. Note that, if there are SubPlans in there,
-		 * they all end up attached to the one parent Plan node.
-		 */
-		Assert(update_tuple_routing_needed ||
-			   (operation == CMD_INSERT &&
-				list_length(node->withCheckOptionLists) == 1 &&
-				mtstate->mt_nplans == 1));
-
-		first_wcoList = linitial(node->withCheckOptionLists);
-		for (i = 0; i < num_partitions; i++)
-		{
-			Relation	partrel;
-			List	   *mapped_wcoList;
-			List	   *wcoExprs = NIL;
-			ListCell   *ll;
-
-			resultRelInfo = proute->partitions[i];
-
-			/*
-			 * If we are referring to a resultRelInfo from one of the update
-			 * result rels, that result rel would already have
-			 * WithCheckOptions initialized.
-			 */
-			if (resultRelInfo->ri_WithCheckOptions)
-				continue;
-
-			partrel = resultRelInfo->ri_RelationDesc;
-
-			mapped_wcoList = map_partition_varattnos(first_wcoList,
-													 firstVarno,
-													 partrel, firstResultRel,
-													 NULL);
-			foreach(ll, mapped_wcoList)
-			{
-				WithCheckOption *wco = castNode(WithCheckOption, lfirst(ll));
-				ExprState  *wcoExpr = ExecInitQual(castNode(List, wco->qual),
-												   &mtstate->ps);
-
-				wcoExprs = lappend(wcoExprs, wcoExpr);
-			}
-
-			resultRelInfo->ri_WithCheckOptions = mapped_wcoList;
-			resultRelInfo->ri_WithCheckOptionExprs = wcoExprs;
-		}
-	}
-
 	/*
 	 * Initialize RETURNING projections if needed.
 	 */
@@ -2358,7 +2286,6 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 	{
 		TupleTableSlot *slot;
 		ExprContext *econtext;
-		List	   *firstReturningList;
 
 		/*
 		 * Initialize result tuple slot and assign its rowtype using the first
@@ -2388,44 +2315,6 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 										resultRelInfo->ri_RelationDesc->rd_att);
 			resultRelInfo++;
 		}
-
-		/*
-		 * Build a projection for each leaf partition rel.  Note that we
-		 * didn't build the returningList for each partition within the
-		 * planner, but simple translation of the varattnos for each partition
-		 * will suffice.  This only occurs for the INSERT case or for UPDATE
-		 * row movement. DELETEs and local UPDATEs are handled above.
-		 */
-		firstReturningList = linitial(node->returningLists);
-		for (i = 0; i < num_partitions; i++)
-		{
-			Relation	partrel;
-			List	   *rlist;
-
-			resultRelInfo = proute->partitions[i];
-
-			/*
-			 * If we are referring to a resultRelInfo from one of the update
-			 * result rels, that result rel would already have a returningList
-			 * built.
-			 */
-			if (resultRelInfo->ri_projectReturning)
-				continue;
-
-			partrel = resultRelInfo->ri_RelationDesc;
-
-			/*
-			 * Use the returning expression of the first resultRelInfo as a
-			 * reference to calculate attno's for the returning expression of
-			 * each of the partitions.
-			 */
-			rlist = map_partition_varattnos(firstReturningList,
-											firstVarno,
-											partrel, firstResultRel, NULL);
-			resultRelInfo->ri_projectReturning =
-				ExecBuildProjectionInfo(rlist, econtext, slot, &mtstate->ps,
-										resultRelInfo->ri_RelationDesc->rd_att);
-		}
 	}
 	else
 	{

src/include/executor/execPartition.h

@@ -58,6 +58,7 @@ typedef struct PartitionDispatchData *PartitionDispatch;
  *								partition tree.
  * num_dispatch					number of partitioned tables in the partition
  *								tree (= length of partition_dispatch_info[])
+ * partition_oids				Array of leaf partitions OIDs
  * partitions					Array of ResultRelInfo* objects with one entry
  *								for every leaf partition in the partition tree.
  * num_partitions				Number of leaf partitions in the partition tree
@@ -91,6 +92,7 @@ typedef struct PartitionTupleRouting
 {
 	PartitionDispatch *partition_dispatch_info;
 	int			num_dispatch;
+	Oid		   *partition_oids;
 	ResultRelInfo **partitions;
 	int			num_partitions;
 	TupleConversionMap **parent_child_tupconv_maps;
@@ -103,12 +105,15 @@ typedef struct PartitionTupleRouting
 } PartitionTupleRouting;
 
 extern PartitionTupleRouting *ExecSetupPartitionTupleRouting(ModifyTableState *mtstate,
-							   Relation rel, Index resultRTindex,
-							   EState *estate);
+							   Relation rel);
 extern int ExecFindPartition(ResultRelInfo *resultRelInfo,
 				  PartitionDispatch *pd,
 				  TupleTableSlot *slot,
 				  EState *estate);
+extern ResultRelInfo *ExecInitPartitionInfo(ModifyTableState *mtstate,
+					ResultRelInfo *resultRelInfo,
+					PartitionTupleRouting *proute,
+					EState *estate, int partidx);
 extern void ExecSetupChildParentMapForLeaf(PartitionTupleRouting *proute);
 extern TupleConversionMap *TupConvMapForLeaf(PartitionTupleRouting *proute,
 				  ResultRelInfo *rootRelInfo, int leaf_index);