Don't scan partitioned tables.

Partitioned tables do not contain any data; only their unpartitioned
descendents need to be scanned.  However, the partitioned tables still
need to be locked, even though they're not scanned.  To make that
work, Append and MergeAppend relations now need to carry a list of
(unscanned) partitioned relations that must be locked, and InitPlan
must lock all partitioned result relations.

Aside from the obvious advantage of avoiding some work at execution
time, this has two other advantages.  First, it may improve the
planner's decision-making in some cases since the empty relation
might throw things off.  Second, it paves the way to getting rid of
the storage for partitioned tables altogether.

Amit Langote, reviewed by me.

Discussion: http://postgr.es/m/6837c359-45c4-8044-34d1-736756335a15@lab.ntt.co.jp

src/backend/executor/execMain.c

@@ -844,6 +844,22 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 		estate->es_num_result_relations = numResultRelations;
 		/* es_result_relation_info is NULL except when within ModifyTable */
 		estate->es_result_relation_info = NULL;
+
+		/*
+		 * In the partitioned result relation case, lock the non-leaf result
+		 * relations too.  We don't however need ResultRelInfos for them.
+		 */
+		if (plannedstmt->nonleafResultRelations)
+		{
+			foreach(l, plannedstmt->nonleafResultRelations)
+			{
+				Index		resultRelationIndex = lfirst_int(l);
+				Oid			resultRelationOid;
+
+				resultRelationOid = getrelid(resultRelationIndex, rangeTable);
+				LockRelationOid(resultRelationOid, RowExclusiveLock);
+			}
+		}
 	}
 	else
 	{
@@ -858,7 +874,11 @@ InitPlan(QueryDesc *queryDesc, int eflags)
 	/*
 	 * Similarly, we have to lock relations selected FOR [KEY] UPDATE/SHARE
 	 * before we initialize the plan tree, else we'd be risking lock upgrades.
-	 * While we are at it, build the ExecRowMark list.
+	 * While we are at it, build the ExecRowMark list.  Any partitioned child
+	 * tables are ignored here (because isParent=true) and will be locked by
+	 * the first Append or MergeAppend node that references them.  (Note that
+	 * the RowMarks corresponding to partitioned child tables are present in
+	 * the same list as the rest, i.e., plannedstmt->rowMarks.)
 	 */
 	estate->es_rowMarks = NIL;
 	foreach(l, plannedstmt->rowMarks)

src/backend/executor/execParallel.c

@@ -161,6 +161,7 @@ ExecSerializePlan(Plan *plan, EState *estate)
 	pstmt->planTree = plan;
 	pstmt->rtable = estate->es_range_table;
 	pstmt->resultRelations = NIL;
+	pstmt->nonleafResultRelations = NIL;
 	pstmt->subplans = estate->es_plannedstmt->subplans;
 	pstmt->rewindPlanIDs = NULL;
 	pstmt->rowMarks = NIL;

src/backend/executor/execUtils.c

@@ -43,6 +43,7 @@
 #include "executor/executor.h"
 #include "nodes/nodeFuncs.h"
 #include "parser/parsetree.h"
+#include "storage/lmgr.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
 
@@ -953,3 +954,58 @@ ShutdownExprContext(ExprContext *econtext, bool isCommit)
 
 	MemoryContextSwitchTo(oldcontext);
 }
+
+/*
+ * ExecLockNonLeafAppendTables
+ *
+ * Locks, if necessary, the tables indicated by the RT indexes contained in
+ * the partitioned_rels list.  These are the non-leaf tables in the partition
+ * tree controlled by a given Append or MergeAppend node.
+ */
+void
+ExecLockNonLeafAppendTables(List *partitioned_rels, EState *estate)
+{
+	PlannedStmt *stmt = estate->es_plannedstmt;
+	ListCell	*lc;
+
+	foreach(lc, partitioned_rels)
+	{
+		ListCell   *l;
+		Index	rti = lfirst_int(lc);
+		bool	is_result_rel = false;
+		Oid		relid = getrelid(rti, estate->es_range_table);
+
+		/* If this is a result relation, already locked in InitPlan */
+		foreach(l, stmt->nonleafResultRelations)
+		{
+			if (rti == lfirst_int(l))
+			{
+				is_result_rel = true;
+				break;
+			}
+		}
+
+		/*
+		 * Not a result relation; check if there is a RowMark that requires
+		 * taking a RowShareLock on this rel.
+		 */
+		if (!is_result_rel)
+		{
+			PlanRowMark *rc = NULL;
+
+			foreach(l, stmt->rowMarks)
+			{
+				if (((PlanRowMark *) lfirst(l))->rti == rti)
+				{
+					rc = lfirst(l);
+					break;
+				}
+			}
+
+			if (rc && RowMarkRequiresRowShareLock(rc->markType))
+				LockRelationOid(relid, RowShareLock);
+			else
+				LockRelationOid(relid, AccessShareLock);
+		}
+	}
+}

src/backend/executor/nodeAppend.c

@@ -128,6 +128,12 @@ ExecInitAppend(Append *node, EState *estate, int eflags)
 	/* check for unsupported flags */
 	Assert(!(eflags & EXEC_FLAG_MARK));
 
+	/*
+	 * Lock the non-leaf tables in the partition tree controlled by this
+	 * node. It's a no-op for non-partitioned parent tables.
+	 */
+	ExecLockNonLeafAppendTables(node->partitioned_rels, estate);
+
 	/*
 	 * Set up empty vector of subplan states
 	 */

src/backend/executor/nodeMergeAppend.c

@@ -71,6 +71,12 @@ ExecInitMergeAppend(MergeAppend *node, EState *estate, int eflags)
 	/* check for unsupported flags */
 	Assert(!(eflags & (EXEC_FLAG_BACKWARD | EXEC_FLAG_MARK)));
 
+	/*
+	 * Lock the non-leaf tables in the partition tree controlled by this
+	 * node.  It's a no-op for non-partitioned parent tables.
+	 */
+	ExecLockNonLeafAppendTables(node->partitioned_rels, estate);
+
 	/*
 	 * Set up empty vector of subplan states
 	 */

src/backend/executor/nodeModifyTable.c

@@ -45,6 +45,7 @@
 #include "foreign/fdwapi.h"
 #include "miscadmin.h"
 #include "nodes/nodeFuncs.h"
+#include "parser/parsetree.h"
 #include "storage/bufmgr.h"
 #include "storage/lmgr.h"
 #include "utils/builtins.h"
@@ -1725,8 +1726,20 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 
 	estate->es_result_relation_info = saved_resultRelInfo;
 
+	/* The root table RT index is at the head of the partitioned_rels list */
+	if (node->partitioned_rels)
+	{
+		Index	root_rti;
+		Oid		root_oid;
+
+		root_rti = linitial_int(node->partitioned_rels);
+		root_oid = getrelid(root_rti, estate->es_range_table);
+		rel = heap_open(root_oid, NoLock);	/* locked by InitPlan */
+	}
+	else
+		rel = mtstate->resultRelInfo->ri_RelationDesc;
+
 	/* Build state for INSERT tuple routing */
-	rel = mtstate->resultRelInfo->ri_RelationDesc;
 	if (operation == CMD_INSERT &&
 		rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
 	{
@@ -1897,6 +1910,10 @@ ExecInitModifyTable(ModifyTable *node, EState *estate, int eflags)
 		mtstate->ps.ps_ExprContext = NULL;
 	}
 
+	/* Close the root partitioned rel if we opened it above. */
+	if (rel != mtstate->resultRelInfo->ri_RelationDesc)
+		heap_close(rel, NoLock);
+
 	/*
 	 * If needed, Initialize target list, projection and qual for ON CONFLICT
 	 * DO UPDATE.

src/backend/nodes/copyfuncs.c

@@ -90,6 +90,7 @@ _copyPlannedStmt(const PlannedStmt *from)
 	COPY_NODE_FIELD(planTree);
 	COPY_NODE_FIELD(rtable);
 	COPY_NODE_FIELD(resultRelations);
+	COPY_NODE_FIELD(nonleafResultRelations);
 	COPY_NODE_FIELD(subplans);
 	COPY_BITMAPSET_FIELD(rewindPlanIDs);
 	COPY_NODE_FIELD(rowMarks);
@@ -200,6 +201,7 @@ _copyModifyTable(const ModifyTable *from)
 	COPY_SCALAR_FIELD(operation);
 	COPY_SCALAR_FIELD(canSetTag);
 	COPY_SCALAR_FIELD(nominalRelation);
+	COPY_NODE_FIELD(partitioned_rels);
 	COPY_NODE_FIELD(resultRelations);
 	COPY_SCALAR_FIELD(resultRelIndex);
 	COPY_NODE_FIELD(plans);
@@ -235,6 +237,7 @@ _copyAppend(const Append *from)
 	/*
 	 * copy remainder of node
 	 */
+	COPY_NODE_FIELD(partitioned_rels);
 	COPY_NODE_FIELD(appendplans);
 
 	return newnode;
@@ -256,6 +259,7 @@ _copyMergeAppend(const MergeAppend *from)
 	/*
 	 * copy remainder of node
 	 */
+	COPY_NODE_FIELD(partitioned_rels);
 	COPY_NODE_FIELD(mergeplans);
 	COPY_SCALAR_FIELD(numCols);
 	COPY_POINTER_FIELD(sortColIdx, from->numCols * sizeof(AttrNumber));
@@ -2204,6 +2208,20 @@ _copyAppendRelInfo(const AppendRelInfo *from)
 	return newnode;
 }
 
+/*
+ * _copyPartitionedChildRelInfo
+ */
+static PartitionedChildRelInfo *
+_copyPartitionedChildRelInfo(const PartitionedChildRelInfo *from)
+{
+	PartitionedChildRelInfo *newnode = makeNode(PartitionedChildRelInfo);
+
+	COPY_SCALAR_FIELD(parent_relid);
+	COPY_NODE_FIELD(child_rels);
+
+	return newnode;
+}
+
 /*
  * _copyPlaceHolderInfo
  */
@@ -4894,6 +4912,9 @@ copyObject(const void *from)
 		case T_AppendRelInfo:
 			retval = _copyAppendRelInfo(from);
 			break;
+		case T_PartitionedChildRelInfo:
+			retval = _copyPartitionedChildRelInfo(from);
+			break;
 		case T_PlaceHolderInfo:
 			retval = _copyPlaceHolderInfo(from);
 			break;

src/backend/nodes/equalfuncs.c

@@ -895,6 +895,15 @@ _equalAppendRelInfo(const AppendRelInfo *a, const AppendRelInfo *b)
 	return true;
 }
 
+static bool
+_equalPartitionedChildRelInfo(const PartitionedChildRelInfo *a, const PartitionedChildRelInfo *b)
+{
+	COMPARE_SCALAR_FIELD(parent_relid);
+	COMPARE_NODE_FIELD(child_rels);
+
+	return true;
+}
+
 static bool
 _equalPlaceHolderInfo(const PlaceHolderInfo *a, const PlaceHolderInfo *b)
 {
@@ -3104,6 +3113,9 @@ equal(const void *a, const void *b)
 		case T_AppendRelInfo:
 			retval = _equalAppendRelInfo(a, b);
 			break;
+		case T_PartitionedChildRelInfo:
+			retval = _equalPartitionedChildRelInfo(a, b);
+			break;
 		case T_PlaceHolderInfo:
 			retval = _equalPlaceHolderInfo(a, b);
 			break;

src/backend/nodes/outfuncs.c

@@ -252,6 +252,7 @@ _outPlannedStmt(StringInfo str, const PlannedStmt *node)
 	WRITE_NODE_FIELD(planTree);
 	WRITE_NODE_FIELD(rtable);
 	WRITE_NODE_FIELD(resultRelations);
+	WRITE_NODE_FIELD(nonleafResultRelations);
 	WRITE_NODE_FIELD(subplans);
 	WRITE_BITMAPSET_FIELD(rewindPlanIDs);
 	WRITE_NODE_FIELD(rowMarks);
@@ -344,6 +345,7 @@ _outModifyTable(StringInfo str, const ModifyTable *node)
 	WRITE_ENUM_FIELD(operation, CmdType);
 	WRITE_BOOL_FIELD(canSetTag);
 	WRITE_UINT_FIELD(nominalRelation);
+	WRITE_NODE_FIELD(partitioned_rels);
 	WRITE_NODE_FIELD(resultRelations);
 	WRITE_INT_FIELD(resultRelIndex);
 	WRITE_NODE_FIELD(plans);
@@ -368,6 +370,7 @@ _outAppend(StringInfo str, const Append *node)
 
 	_outPlanInfo(str, (const Plan *) node);
 
+	WRITE_NODE_FIELD(partitioned_rels);
 	WRITE_NODE_FIELD(appendplans);
 }
 
@@ -380,6 +383,7 @@ _outMergeAppend(StringInfo str, const MergeAppend *node)
 
 	_outPlanInfo(str, (const Plan *) node);
 
+	WRITE_NODE_FIELD(partitioned_rels);
 	WRITE_NODE_FIELD(mergeplans);
 
 	WRITE_INT_FIELD(numCols);
@@ -1808,6 +1812,7 @@ _outAppendPath(StringInfo str, const AppendPath *node)
 
 	_outPathInfo(str, (const Path *) node);
 
+	WRITE_NODE_FIELD(partitioned_rels);
 	WRITE_NODE_FIELD(subpaths);
 }
 
@@ -1818,6 +1823,7 @@ _outMergeAppendPath(StringInfo str, const MergeAppendPath *node)
 
 	_outPathInfo(str, (const Path *) node);
 
+	WRITE_NODE_FIELD(partitioned_rels);
 	WRITE_NODE_FIELD(subpaths);
 	WRITE_FLOAT_FIELD(limit_tuples, "%.0f");
 }
@@ -2023,6 +2029,7 @@ _outModifyTablePath(StringInfo str, const ModifyTablePath *node)
 	WRITE_ENUM_FIELD(operation, CmdType);
 	WRITE_BOOL_FIELD(canSetTag);
 	WRITE_UINT_FIELD(nominalRelation);
+	WRITE_NODE_FIELD(partitioned_rels);
 	WRITE_NODE_FIELD(resultRelations);
 	WRITE_NODE_FIELD(subpaths);
 	WRITE_NODE_FIELD(subroots);
@@ -2099,6 +2106,7 @@ _outPlannerGlobal(StringInfo str, const PlannerGlobal *node)
 	WRITE_NODE_FIELD(finalrtable);
 	WRITE_NODE_FIELD(finalrowmarks);
 	WRITE_NODE_FIELD(resultRelations);
+	WRITE_NODE_FIELD(nonleafResultRelations);
 	WRITE_NODE_FIELD(relationOids);
 	WRITE_NODE_FIELD(invalItems);
 	WRITE_INT_FIELD(nParamExec);
@@ -2137,6 +2145,7 @@ _outPlannerInfo(StringInfo str, const PlannerInfo *node)
 	WRITE_NODE_FIELD(full_join_clauses);
 	WRITE_NODE_FIELD(join_info_list);
 	WRITE_NODE_FIELD(append_rel_list);
+	WRITE_NODE_FIELD(pcinfo_list);
 	WRITE_NODE_FIELD(rowMarks);
 	WRITE_NODE_FIELD(placeholder_list);
 	WRITE_NODE_FIELD(fkey_list);
@@ -2419,6 +2428,15 @@ _outAppendRelInfo(StringInfo str, const AppendRelInfo *node)
 	WRITE_OID_FIELD(parent_reloid);
 }
 
+static void
+_outPartitionedChildRelInfo(StringInfo str, const PartitionedChildRelInfo *node)
+{
+	WRITE_NODE_TYPE("PARTITIONEDCHILDRELINFO");
+
+	WRITE_UINT_FIELD(parent_relid);
+	WRITE_NODE_FIELD(child_rels);
+}
+
 static void
 _outPlaceHolderInfo(StringInfo str, const PlaceHolderInfo *node)
 {
@@ -3906,6 +3924,9 @@ outNode(StringInfo str, const void *obj)
 			case T_AppendRelInfo:
 				_outAppendRelInfo(str, obj);
 				break;
+			case T_PartitionedChildRelInfo:
+				_outPartitionedChildRelInfo(str, obj);
+				break;
 			case T_PlaceHolderInfo:
 				_outPlaceHolderInfo(str, obj);
 				break;

src/backend/nodes/readfuncs.c

@@ -1444,6 +1444,7 @@ _readPlannedStmt(void)
 	READ_NODE_FIELD(planTree);
 	READ_NODE_FIELD(rtable);
 	READ_NODE_FIELD(resultRelations);
+	READ_NODE_FIELD(nonleafResultRelations);
 	READ_NODE_FIELD(subplans);
 	READ_BITMAPSET_FIELD(rewindPlanIDs);
 	READ_NODE_FIELD(rowMarks);
@@ -1535,6 +1536,7 @@ _readModifyTable(void)
 	READ_ENUM_FIELD(operation, CmdType);
 	READ_BOOL_FIELD(canSetTag);
 	READ_UINT_FIELD(nominalRelation);
+	READ_NODE_FIELD(partitioned_rels);
 	READ_NODE_FIELD(resultRelations);
 	READ_INT_FIELD(resultRelIndex);
 	READ_NODE_FIELD(plans);
@@ -1564,6 +1566,7 @@ _readAppend(void)
 
 	ReadCommonPlan(&local_node->plan);
 
+	READ_NODE_FIELD(partitioned_rels);
 	READ_NODE_FIELD(appendplans);
 
 	READ_DONE();
@@ -1579,6 +1582,7 @@ _readMergeAppend(void)
 
 	ReadCommonPlan(&local_node->plan);
 
+	READ_NODE_FIELD(partitioned_rels);
 	READ_NODE_FIELD(mergeplans);
 	READ_INT_FIELD(numCols);
 	READ_ATTRNUMBER_ARRAY(sortColIdx, local_node->numCols);

src/backend/optimizer/path/allpaths.c

@@ -95,7 +95,8 @@ static void set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 						Index rti, RangeTblEntry *rte);
 static void generate_mergeappend_paths(PlannerInfo *root, RelOptInfo *rel,
 						   List *live_childrels,
-						   List *all_child_pathkeys);
+						   List *all_child_pathkeys,
+						   List *partitioned_rels);
 static Path *get_cheapest_parameterized_child_path(PlannerInfo *root,
 									  RelOptInfo *rel,
 									  Relids required_outer);
@@ -346,6 +347,14 @@ set_rel_size(PlannerInfo *root, RelOptInfo *rel,
 					/* Foreign table */
 					set_foreign_size(root, rel, rte);
 				}
+				else if (rte->relkind == RELKIND_PARTITIONED_TABLE)
+				{
+					/*
+					 * A partitioned table without leaf partitions is marked
+					 * as a dummy rel.
+					 */
+					set_dummy_rel_pathlist(rel);
+				}
 				else if (rte->tablesample != NULL)
 				{
 					/* Sampled relation */
@@ -1259,6 +1268,16 @@ add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
 	List	   *all_child_pathkeys = NIL;
 	List	   *all_child_outers = NIL;
 	ListCell   *l;
+	List	   *partitioned_rels = NIL;
+	RangeTblEntry *rte;
+
+	rte = planner_rt_fetch(rel->relid, root);
+	if (rte->relkind == RELKIND_PARTITIONED_TABLE)
+	{
+		partitioned_rels = get_partitioned_child_rels(root, rel->relid);
+		/* The root partitioned table is included as a child rel */
+		Assert(list_length(partitioned_rels) >= 1);
+	}
 
 	/*
 	 * For every non-dummy child, remember the cheapest path.  Also, identify
@@ -1359,7 +1378,8 @@ add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
 	 * if we have zero or one live subpath due to constraint exclusion.)
 	 */
 	if (subpaths_valid)
-		add_path(rel, (Path *) create_append_path(rel, subpaths, NULL, 0));
+		add_path(rel, (Path *) create_append_path(rel, subpaths, NULL, 0,
+												  partitioned_rels));
 
 	/*
 	 * Consider an append of partial unordered, unparameterized partial paths.
@@ -1386,7 +1406,7 @@ add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
 
 		/* Generate a partial append path. */
 		appendpath = create_append_path(rel, partial_subpaths, NULL,
-										parallel_workers);
+										parallel_workers, partitioned_rels);
 		add_partial_path(rel, (Path *) appendpath);
 	}
 
@@ -1396,7 +1416,8 @@ add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
 	 */
 	if (subpaths_valid)
 		generate_mergeappend_paths(root, rel, live_childrels,
-								   all_child_pathkeys);
+								   all_child_pathkeys,
+								   partitioned_rels);
 
 	/*
 	 * Build Append paths for each parameterization seen among the child rels.
@@ -1438,7 +1459,8 @@ add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
 
 		if (subpaths_valid)
 			add_path(rel, (Path *)
-					 create_append_path(rel, subpaths, required_outer, 0));
+					 create_append_path(rel, subpaths, required_outer, 0,
+										partitioned_rels));
 	}
 }
 
@@ -1468,7 +1490,8 @@ add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
 static void
 generate_mergeappend_paths(PlannerInfo *root, RelOptInfo *rel,
 						   List *live_childrels,
-						   List *all_child_pathkeys)
+						   List *all_child_pathkeys,
+						   List *partitioned_rels)
 {
 	ListCell   *lcp;
 
@@ -1532,13 +1555,15 @@ generate_mergeappend_paths(PlannerInfo *root, RelOptInfo *rel,
 														rel,
 														startup_subpaths,
 														pathkeys,
-														NULL));
+														NULL,
+														partitioned_rels));
 		if (startup_neq_total)
 			add_path(rel, (Path *) create_merge_append_path(root,
 															rel,
 															total_subpaths,
 															pathkeys,
-															NULL));
+															NULL,
+															partitioned_rels));
 	}
 }
 
@@ -1671,7 +1696,7 @@ set_dummy_rel_pathlist(RelOptInfo *rel)
 	rel->pathlist = NIL;
 	rel->partial_pathlist = NIL;
 
-	add_path(rel, (Path *) create_append_path(rel, NIL, NULL, 0));
+	add_path(rel, (Path *) create_append_path(rel, NIL, NULL, 0, NIL));
 
 	/*
 	 * We set the cheapest path immediately, to ensure that IS_DUMMY_REL()

src/backend/optimizer/path/joinrels.c

@@ -1217,7 +1217,7 @@ mark_dummy_rel(RelOptInfo *rel)
 	rel->partial_pathlist = NIL;
 
 	/* Set up the dummy path */
-	add_path(rel, (Path *) create_append_path(rel, NIL, NULL, 0));
+	add_path(rel, (Path *) create_append_path(rel, NIL, NULL, 0, NIL));
 
 	/* Set or update cheapest_total_path and related fields */
 	set_cheapest(rel);

src/backend/optimizer/plan/createplan.c

@@ -199,7 +199,7 @@ static CteScan *make_ctescan(List *qptlist, List *qpqual,
 			 Index scanrelid, int ctePlanId, int cteParam);
 static WorkTableScan *make_worktablescan(List *qptlist, List *qpqual,
 				   Index scanrelid, int wtParam);
-static Append *make_append(List *appendplans, List *tlist);
+static Append *make_append(List *appendplans, List *tlist, List *partitioned_rels);
 static RecursiveUnion *make_recursive_union(List *tlist,
 					 Plan *lefttree,
 					 Plan *righttree,
@@ -273,7 +273,7 @@ static Result *make_result(List *tlist, Node *resconstantqual, Plan *subplan);
 static ProjectSet *make_project_set(List *tlist, Plan *subplan);
 static ModifyTable *make_modifytable(PlannerInfo *root,
 				 CmdType operation, bool canSetTag,
-				 Index nominalRelation,
+				 Index nominalRelation, List *partitioned_rels,
 				 List *resultRelations, List *subplans,
 				 List *withCheckOptionLists, List *returningLists,
 				 List *rowMarks, OnConflictExpr *onconflict, int epqParam);
@@ -1026,7 +1026,7 @@ create_append_plan(PlannerInfo *root, AppendPath *best_path)
 	 * parent-rel Vars it'll be asked to emit.
 	 */
 
-	plan = make_append(subplans, tlist);
+	plan = make_append(subplans, tlist, best_path->partitioned_rels);
 
 	copy_generic_path_info(&plan->plan, (Path *) best_path);
 
@@ -1134,6 +1134,7 @@ create_merge_append_plan(PlannerInfo *root, MergeAppendPath *best_path)
 		subplans = lappend(subplans, subplan);
 	}
 
+	node->partitioned_rels = best_path->partitioned_rels;
 	node->mergeplans = subplans;
 
 	return (Plan *) node;
@@ -2314,6 +2315,7 @@ create_modifytable_plan(PlannerInfo *root, ModifyTablePath *best_path)
 							best_path->operation,
 							best_path->canSetTag,
 							best_path->nominalRelation,
+							best_path->partitioned_rels,
 							best_path->resultRelations,
 							subplans,
 							best_path->withCheckOptionLists,
@@ -5161,7 +5163,7 @@ make_foreignscan(List *qptlist,
 }
 
 static Append *
-make_append(List *appendplans, List *tlist)
+make_append(List *appendplans, List *tlist, List *partitioned_rels)
 {
 	Append	   *node = makeNode(Append);
 	Plan	   *plan = &node->plan;
@@ -5170,6 +5172,7 @@ make_append(List *appendplans, List *tlist)
 	plan->qual = NIL;
 	plan->lefttree = NULL;
 	plan->righttree = NULL;
+	node->partitioned_rels = partitioned_rels;
 	node->appendplans = appendplans;
 
 	return node;
@@ -6282,7 +6285,7 @@ make_project_set(List *tlist,
 static ModifyTable *
 make_modifytable(PlannerInfo *root,
 				 CmdType operation, bool canSetTag,
-				 Index nominalRelation,
+				 Index nominalRelation, List *partitioned_rels,
 				 List *resultRelations, List *subplans,
 				 List *withCheckOptionLists, List *returningLists,
 				 List *rowMarks, OnConflictExpr *onconflict, int epqParam)
@@ -6308,6 +6311,7 @@ make_modifytable(PlannerInfo *root,
 	node->operation = operation;
 	node->canSetTag = canSetTag;
 	node->nominalRelation = nominalRelation;
+	node->partitioned_rels = partitioned_rels;
 	node->resultRelations = resultRelations;
 	node->resultRelIndex = -1;	/* will be set correctly in setrefs.c */
 	node->plans = subplans;

src/backend/optimizer/plan/planner.c

@@ -212,6 +212,7 @@ standard_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
 	glob->finalrtable = NIL;
 	glob->finalrowmarks = NIL;
 	glob->resultRelations = NIL;
+	glob->nonleafResultRelations = NIL;
 	glob->relationOids = NIL;
 	glob->invalItems = NIL;
 	glob->nParamExec = 0;
@@ -380,6 +381,7 @@ standard_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
 	Assert(glob->finalrtable == NIL);
 	Assert(glob->finalrowmarks == NIL);
 	Assert(glob->resultRelations == NIL);
+	Assert(glob->nonleafResultRelations == NIL);
 	top_plan = set_plan_references(root, top_plan);
 	/* ... and the subplans (both regular subplans and initplans) */
 	Assert(list_length(glob->subplans) == list_length(glob->subroots));
@@ -405,6 +407,7 @@ standard_planner(Query *parse, int cursorOptions, ParamListInfo boundParams)
 	result->planTree = top_plan;
 	result->rtable = glob->finalrtable;
 	result->resultRelations = glob->resultRelations;
+	result->nonleafResultRelations = glob->nonleafResultRelations;
 	result->subplans = glob->subplans;
 	result->rewindPlanIDs = glob->rewindPlanIDs;
 	result->rowMarks = glob->finalrowmarks;
@@ -474,6 +477,7 @@ subquery_planner(PlannerGlobal *glob, Query *parse,
 	root->multiexpr_params = NIL;
 	root->eq_classes = NIL;
 	root->append_rel_list = NIL;
+	root->pcinfo_list = NIL;
 	root->rowMarks = NIL;
 	memset(root->upper_rels, 0, sizeof(root->upper_rels));
 	memset(root->upper_targets, 0, sizeof(root->upper_targets));
@@ -1007,6 +1011,8 @@ inheritance_planner(PlannerInfo *root)
 	RelOptInfo *final_rel;
 	ListCell   *lc;
 	Index		rti;
+	RangeTblEntry *parent_rte;
+	List		  *partitioned_rels = NIL;
 
 	Assert(parse->commandType != CMD_INSERT);
 
@@ -1064,6 +1070,18 @@ inheritance_planner(PlannerInfo *root)
 		}
 	}
 
+	/*
+	 * If the parent RTE is a partitioned table, we should use that as the
+	 * nominal relation, because the RTEs added for partitioned tables
+	 * (including the root parent) as child members of the inheritance set
+	 * do not appear anywhere else in the plan.  The situation is exactly
+	 * the opposite in the case of non-partitioned inheritance parent as
+	 * described below.
+	 */
+	parent_rte = rt_fetch(parentRTindex, root->parse->rtable);
+	if (parent_rte->relkind == RELKIND_PARTITIONED_TABLE)
+		nominalRelation = parentRTindex;
+
 	/*
 	 * And now we can get on with generating a plan for each child table.
 	 */
@@ -1071,7 +1089,6 @@ inheritance_planner(PlannerInfo *root)
 	{
 		AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(lc);
 		PlannerInfo *subroot;
-		RangeTblEntry *parent_rte;
 		RangeTblEntry *child_rte;
 		RelOptInfo *sub_final_rel;
 		Path	   *subpath;
@@ -1216,15 +1233,25 @@ inheritance_planner(PlannerInfo *root)
 		grouping_planner(subroot, true, 0.0 /* retrieve all tuples */ );
 
 		/*
-		 * We'll use the first child relation (even if it's excluded) as the
-		 * nominal target relation of the ModifyTable node.  Because of the
-		 * way expand_inherited_rtentry works, this should always be the RTE
-		 * representing the parent table in its role as a simple member of the
-		 * inheritance set.  (It would be logically cleaner to use the
-		 * inheritance parent RTE as the nominal target; but since that RTE
-		 * will not be otherwise referenced in the plan, doing so would give
-		 * rise to confusing use of multiple aliases in EXPLAIN output for
-		 * what the user will think is the "same" table.)
+		 * Set the nomimal target relation of the ModifyTable node if not
+		 * already done.  We use the inheritance parent RTE as the nominal
+		 * target relation if it's a partitioned table (see just above this
+		 * loop).  In the non-partitioned parent case, we'll use the first
+		 * child relation (even if it's excluded) as the nominal target
+		 * relation.  Because of the way expand_inherited_rtentry works, the
+		 * latter should be the RTE representing the parent table in its role
+		 * as a simple member of the inheritance set.
+		 *
+		 * It would be logically cleaner to *always* use the inheritance
+		 * parent RTE as the nominal relation; but that RTE is not otherwise
+		 * referenced in the plan in the non-partitioned inheritance case.
+		 * Instead the duplicate child RTE created by expand_inherited_rtentry
+		 * is used elsewhere in the plan, so using the original parent RTE
+		 * would give rise to confusing use of multiple aliases in EXPLAIN
+		 * output for what the user will think is the "same" table.  OTOH,
+		 * it's not a problem in the partitioned inheritance case, because
+		 * the duplicate child RTE added for the parent does not appear
+		 * anywhere else in the plan tree.
 		 */
 		if (nominalRelation < 0)
 			nominalRelation = appinfo->child_relid;
@@ -1298,6 +1325,13 @@ inheritance_planner(PlannerInfo *root)
 		Assert(!parse->onConflict);
 	}
 
+	if (parent_rte->relkind == RELKIND_PARTITIONED_TABLE)
+	{
+		partitioned_rels = get_partitioned_child_rels(root, parentRTindex);
+		/* The root partitioned table is included as a child rel */
+		Assert(list_length(partitioned_rels) >= 1);
+	}
+
 	/* Result path must go into outer query's FINAL upperrel */
 	final_rel = fetch_upper_rel(root, UPPERREL_FINAL, NULL);
 
@@ -1351,6 +1385,7 @@ inheritance_planner(PlannerInfo *root)
 									 parse->commandType,
 									 parse->canSetTag,
 									 nominalRelation,
+									 partitioned_rels,
 									 resultRelations,
 									 subpaths,
 									 subroots,
@@ -2046,6 +2081,7 @@ grouping_planner(PlannerInfo *root, bool inheritance_update,
 										parse->commandType,
 										parse->canSetTag,
 										parse->resultRelation,
+										NIL,
 										list_make1_int(parse->resultRelation),
 										list_make1(path),
 										list_make1(root),
@@ -3348,7 +3384,8 @@ create_grouping_paths(PlannerInfo *root,
 				create_append_path(grouped_rel,
 								   paths,
 								   NULL,
-								   0);
+								   0,
+								   NIL);
 			path->pathtarget = target;
 		}
 		else
@@ -5470,3 +5507,33 @@ plan_cluster_use_sort(Oid tableOid, Oid indexOid)
 
 	return (seqScanAndSortPath.total_cost < indexScanPath->path.total_cost);
 }
+
+/*
+ * get_partitioned_child_rels
+ *		Returns a list of the RT indexes of the partitioned child relations
+ *		with rti as the root parent RT index.
+ *
+ * Note: Only call this function on RTEs known to be partitioned tables.
+ */
+List *
+get_partitioned_child_rels(PlannerInfo *root, Index rti)
+{
+	List	   *result = NIL;
+	ListCell   *l;
+
+	foreach(l, root->pcinfo_list)
+	{
+		PartitionedChildRelInfo	*pc = lfirst(l);
+
+		if (pc->parent_relid == rti)
+		{
+			result = pc->child_rels;
+			break;
+		}
+	}
+
+	/* The root partitioned table is included as a child rel */
+	Assert(list_length(result) >= 1);
+
+	return result;
+}

src/backend/optimizer/plan/setrefs.c

@@ -835,6 +835,10 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 				splan->nominalRelation += rtoffset;
 				splan->exclRelRTI += rtoffset;
 
+				foreach(l, splan->partitioned_rels)
+				{
+					lfirst_int(l) += rtoffset;
+				}
 				foreach(l, splan->resultRelations)
 				{
 					lfirst_int(l) += rtoffset;
@@ -863,6 +867,15 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 				root->glob->resultRelations =
 					list_concat(root->glob->resultRelations,
 								list_copy(splan->resultRelations));
+
+				/*
+				 * If the main target relation is a partitioned table, the
+				 * following list contains the RT indexes of partitioned child
+				 * relations, which are not included in the above list.
+				 */
+				root->glob->nonleafResultRelations =
+					list_concat(root->glob->nonleafResultRelations,
+								list_copy(splan->partitioned_rels));
 			}
 			break;
 		case T_Append:
@@ -875,6 +888,10 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 				 */
 				set_dummy_tlist_references(plan, rtoffset);
 				Assert(splan->plan.qual == NIL);
+				foreach(l, splan->partitioned_rels)
+				{
+					lfirst_int(l) += rtoffset;
+				}
 				foreach(l, splan->appendplans)
 				{
 					lfirst(l) = set_plan_refs(root,
@@ -893,6 +910,10 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 				 */
 				set_dummy_tlist_references(plan, rtoffset);
 				Assert(splan->plan.qual == NIL);
+				foreach(l, splan->partitioned_rels)
+				{
+					lfirst_int(l) += rtoffset;
+				}
 				foreach(l, splan->mergeplans)
 				{
 					lfirst(l) = set_plan_refs(root,

src/backend/optimizer/prep/prepunion.c

@@ -566,7 +566,7 @@ generate_union_path(SetOperationStmt *op, PlannerInfo *root,
 	/*
 	 * Append the child results together.
 	 */
-	path = (Path *) create_append_path(result_rel, pathlist, NULL, 0);
+	path = (Path *) create_append_path(result_rel, pathlist, NULL, 0, NIL);
 
 	/* We have to manually jam the right tlist into the path; ick */
 	path->pathtarget = create_pathtarget(root, tlist);
@@ -678,7 +678,7 @@ generate_nonunion_path(SetOperationStmt *op, PlannerInfo *root,
 	/*
 	 * Append the child results together.
 	 */
-	path = (Path *) create_append_path(result_rel, pathlist, NULL, 0);
+	path = (Path *) create_append_path(result_rel, pathlist, NULL, 0, NIL);
 
 	/* We have to manually jam the right tlist into the path; ick */
 	path->pathtarget = create_pathtarget(root, tlist);
@@ -1364,6 +1364,9 @@ expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte, Index rti)
 	List	   *inhOIDs;
 	List	   *appinfos;
 	ListCell   *l;
+	bool		need_append;
+	PartitionedChildRelInfo *pcinfo;
+	List	   *partitioned_child_rels = NIL;
 
 	/* Does RT entry allow inheritance? */
 	if (!rte->inh)
@@ -1435,6 +1438,7 @@ expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte, Index rti)
 
 	/* Scan the inheritance set and expand it */
 	appinfos = NIL;
+	need_append = false;
 	foreach(l, inhOIDs)
 	{
 		Oid			childOID = lfirst_oid(l);
@@ -1483,36 +1487,46 @@ expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte, Index rti)
 		childRTindex = list_length(parse->rtable);
 
 		/*
-		 * Build an AppendRelInfo for this parent and child.
+		 * Build an AppendRelInfo for this parent and child, unless the child
+		 * is a partitioned table.
 		 */
-		appinfo = makeNode(AppendRelInfo);
-		appinfo->parent_relid = rti;
-		appinfo->child_relid = childRTindex;
-		appinfo->parent_reltype = oldrelation->rd_rel->reltype;
-		appinfo->child_reltype = newrelation->rd_rel->reltype;
-		make_inh_translation_list(oldrelation, newrelation, childRTindex,
-								  &appinfo->translated_vars);
-		appinfo->parent_reloid = parentOID;
-		appinfos = lappend(appinfos, appinfo);
-
-		/*
-		 * Translate the column permissions bitmaps to the child's attnums (we
-		 * have to build the translated_vars list before we can do this). But
-		 * if this is the parent table, leave copyObject's result alone.
-		 *
-		 * Note: we need to do this even though the executor won't run any
-		 * permissions checks on the child RTE.  The insertedCols/updatedCols
-		 * bitmaps may be examined for trigger-firing purposes.
-		 */
-		if (childOID != parentOID)
+		if (childrte->relkind != RELKIND_PARTITIONED_TABLE)
 		{
-			childrte->selectedCols = translate_col_privs(rte->selectedCols,
+			need_append = true;
+			appinfo = makeNode(AppendRelInfo);
+			appinfo->parent_relid = rti;
+			appinfo->child_relid = childRTindex;
+			appinfo->parent_reltype = oldrelation->rd_rel->reltype;
+			appinfo->child_reltype = newrelation->rd_rel->reltype;
+			make_inh_translation_list(oldrelation, newrelation, childRTindex,
+									  &appinfo->translated_vars);
+			appinfo->parent_reloid = parentOID;
+			appinfos = lappend(appinfos, appinfo);
+
+			/*
+			 * Translate the column permissions bitmaps to the child's attnums
+			 * (we have to build the translated_vars list before we can do
+			 * this). But if this is the parent table, leave copyObject's
+			 * result alone.
+			 *
+			 * Note: we need to do this even though the executor won't run any
+			 * permissions checks on the child RTE.  The
+			 * insertedCols/updatedCols bitmaps may be examined for
+			 * trigger-firing purposes.
+			 */
+			if (childOID != parentOID)
+			{
+				childrte->selectedCols = translate_col_privs(rte->selectedCols,
 												   appinfo->translated_vars);
-			childrte->insertedCols = translate_col_privs(rte->insertedCols,
+				childrte->insertedCols = translate_col_privs(rte->insertedCols,
 												   appinfo->translated_vars);
-			childrte->updatedCols = translate_col_privs(rte->updatedCols,
+				childrte->updatedCols = translate_col_privs(rte->updatedCols,
 												   appinfo->translated_vars);
+			}
 		}
+		else
+			partitioned_child_rels = lappend_int(partitioned_child_rels,
+												 childRTindex);
 
 		/*
 		 * Build a PlanRowMark if parent is marked FOR UPDATE/SHARE.
@@ -1529,7 +1543,13 @@ expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte, Index rti)
 			newrc->allMarkTypes = (1 << newrc->markType);
 			newrc->strength = oldrc->strength;
 			newrc->waitPolicy = oldrc->waitPolicy;
-			newrc->isParent = false;
+
+			/*
+			 * We mark RowMarks for partitioned child tables as parent RowMarks
+			 * so that the executor ignores them (except their existence means
+			 * that the child tables be locked using appropriate mode).
+			 */
+			newrc->isParent = (childrte->relkind == RELKIND_PARTITIONED_TABLE);
 
 			/* Include child's rowmark type in parent's allMarkTypes */
 			oldrc->allMarkTypes |= newrc->allMarkTypes;
@@ -1545,18 +1565,37 @@ expand_inherited_rtentry(PlannerInfo *root, RangeTblEntry *rte, Index rti)
 	heap_close(oldrelation, NoLock);
 
 	/*
-	 * If all the children were temp tables, pretend it's a non-inheritance
-	 * situation.  The duplicate RTE we added for the parent table is
-	 * harmless, so we don't bother to get rid of it; ditto for the useless
-	 * PlanRowMark node.
+	 * If all the children were temp tables or a partitioned parent did not
+	 * have any leaf partitions, pretend it's a non-inheritance situation; we
+	 * don't need Append node in that case.  The duplicate RTE we added for
+	 * the parent table is harmless, so we don't bother to get rid of it;
+	 * ditto for the useless PlanRowMark node.
 	 */
-	if (list_length(appinfos) < 2)
+	if (!need_append)
 	{
 		/* Clear flag before returning */
 		rte->inh = false;
 		return;
 	}
 
+	/*
+	 * We keep a list of objects in root, each of which maps a partitioned
+	 * parent RT index to the list of RT indexes of its partitioned child
+	 * tables.  When creating an Append or a ModifyTable path for the parent,
+	 * we copy the child RT index list verbatim to the path so that it could
+	 * be carried over to the executor so that the latter could identify
+	 * the partitioned child tables.
+	 */
+	if (partitioned_child_rels != NIL)
+	{
+		pcinfo = makeNode(PartitionedChildRelInfo);
+
+		Assert(rte->relkind == RELKIND_PARTITIONED_TABLE);
+		pcinfo->parent_relid = rti;
+		pcinfo->child_rels = partitioned_child_rels;
+		root->pcinfo_list = lappend(root->pcinfo_list, pcinfo);
+	}
+
 	/* Otherwise, OK to add to root->append_rel_list */
 	root->append_rel_list = list_concat(root->append_rel_list, appinfos);
 }

src/backend/optimizer/util/pathnode.c

@@ -1201,7 +1201,7 @@ create_tidscan_path(PlannerInfo *root, RelOptInfo *rel, List *tidquals,
  */
 AppendPath *
 create_append_path(RelOptInfo *rel, List *subpaths, Relids required_outer,
-				   int parallel_workers)
+				   int parallel_workers, List *partitioned_rels)
 {
 	AppendPath *pathnode = makeNode(AppendPath);
 	ListCell   *l;
@@ -1216,6 +1216,7 @@ create_append_path(RelOptInfo *rel, List *subpaths, Relids required_outer,
 	pathnode->path.parallel_workers = parallel_workers;
 	pathnode->path.pathkeys = NIL;		/* result is always considered
 										 * unsorted */
+	pathnode->partitioned_rels = partitioned_rels;
 	pathnode->subpaths = subpaths;
 
 	/*
@@ -1258,7 +1259,8 @@ create_merge_append_path(PlannerInfo *root,
 						 RelOptInfo *rel,
 						 List *subpaths,
 						 List *pathkeys,
-						 Relids required_outer)
+						 Relids required_outer,
+						 List *partitioned_rels)
 {
 	MergeAppendPath *pathnode = makeNode(MergeAppendPath);
 	Cost		input_startup_cost;
@@ -1274,6 +1276,7 @@ create_merge_append_path(PlannerInfo *root,
 	pathnode->path.parallel_safe = rel->consider_parallel;
 	pathnode->path.parallel_workers = 0;
 	pathnode->path.pathkeys = pathkeys;
+	pathnode->partitioned_rels = partitioned_rels;
 	pathnode->subpaths = subpaths;
 
 	/*
@@ -3105,7 +3108,7 @@ create_lockrows_path(PlannerInfo *root, RelOptInfo *rel,
 ModifyTablePath *
 create_modifytable_path(PlannerInfo *root, RelOptInfo *rel,
 						CmdType operation, bool canSetTag,
-						Index nominalRelation,
+						Index nominalRelation, List *partitioned_rels,
 						List *resultRelations, List *subpaths,
 						List *subroots,
 						List *withCheckOptionLists, List *returningLists,
@@ -3172,6 +3175,7 @@ create_modifytable_path(PlannerInfo *root, RelOptInfo *rel,
 	pathnode->operation = operation;
 	pathnode->canSetTag = canSetTag;
 	pathnode->nominalRelation = nominalRelation;
+	pathnode->partitioned_rels = partitioned_rels;
 	pathnode->resultRelations = resultRelations;
 	pathnode->subpaths = subpaths;
 	pathnode->subroots = subroots;

src/backend/utils/cache/plancache.c

@@ -1514,7 +1514,8 @@ AcquireExecutorLocks(List *stmt_list, bool acquire)
 			 * fail if it's been dropped entirely --- we'll just transiently
 			 * acquire a non-conflicting lock.
 			 */
-			if (list_member_int(plannedstmt->resultRelations, rt_index))
+			if (list_member_int(plannedstmt->resultRelations, rt_index) ||
+				list_member_int(plannedstmt->nonleafResultRelations, rt_index))
 				lockmode = RowExclusiveLock;
 			else if ((rc = get_plan_rowmark(plannedstmt->rowMarks, rt_index)) != NULL &&
 					 RowMarkRequiresRowShareLock(rc->markType))

src/include/executor/executor.h

@@ -375,6 +375,7 @@ extern void RegisterExprContextCallback(ExprContext *econtext,
 extern void UnregisterExprContextCallback(ExprContext *econtext,
 							  ExprContextCallbackFunction function,
 							  Datum arg);
+extern void ExecLockNonLeafAppendTables(List *partitioned_rels, EState *estate);
 
 /*
  * prototypes from functions in execIndexing.c

src/include/nodes/nodes.h

@@ -275,6 +275,7 @@ typedef enum NodeTag
 	T_PlaceHolderVar,
 	T_SpecialJoinInfo,
 	T_AppendRelInfo,
+	T_PartitionedChildRelInfo,
 	T_PlaceHolderInfo,
 	T_MinMaxAggInfo,
 	T_PlannerParamItem,

src/include/nodes/plannodes.h

@@ -65,6 +65,9 @@ typedef struct PlannedStmt
 	/* rtable indexes of target relations for INSERT/UPDATE/DELETE */
 	List	   *resultRelations;	/* integer list of RT indexes, or NIL */
 
+	/* rtable indexes of non-leaf target relations for INSERT/UPDATE/DELETE */
+	List	   *nonleafResultRelations;
+
 	List	   *subplans;		/* Plan trees for SubPlan expressions */
 
 	Bitmapset  *rewindPlanIDs;	/* indices of subplans that require REWIND */
@@ -202,6 +205,8 @@ typedef struct ModifyTable
 	CmdType		operation;		/* INSERT, UPDATE, or DELETE */
 	bool		canSetTag;		/* do we set the command tag/es_processed? */
 	Index		nominalRelation;	/* Parent RT index for use of EXPLAIN */
+	/* RT indexes of non-leaf tables in a partition tree */
+	List	   *partitioned_rels;
 	List	   *resultRelations;	/* integer list of RT indexes */
 	int			resultRelIndex; /* index of first resultRel in plan's list */
 	List	   *plans;			/* plan(s) producing source data */
@@ -227,6 +232,8 @@ typedef struct ModifyTable
 typedef struct Append
 {
 	Plan		plan;
+	/* RT indexes of non-leaf tables in a partition tree */
+	List	   *partitioned_rels;
 	List	   *appendplans;
 } Append;
 
@@ -238,6 +245,8 @@ typedef struct Append
 typedef struct MergeAppend
 {
 	Plan		plan;
+	/* RT indexes of non-leaf tables in a partition tree */
+	List	   *partitioned_rels;
 	List	   *mergeplans;
 	/* remaining fields are just like the sort-key info in struct Sort */
 	int			numCols;		/* number of sort-key columns */
@@ -937,11 +946,12 @@ typedef enum RowMarkType
  * When the planner discovers that a relation is the root of an inheritance
  * tree, it sets isParent true, and adds an additional PlanRowMark to the
  * list for each child relation (including the target rel itself in its role
- * as a child).  The child entries have rti == child rel's RT index and
- * prti == parent's RT index, and can therefore be recognized as children by
- * the fact that prti != rti.  The parent's allMarkTypes field gets the OR
- * of (1<<markType) across all its children (this definition allows children
- * to use different markTypes).
+ * as a child).  isParent is also set to true for the partitioned child
+ * relations, which are not scanned just like the root parent.  The child
+ * entries have rti == child rel's RT index and prti == parent's RT index,
+ * and can therefore be recognized as children by the fact that prti != rti.
+ * The parent's allMarkTypes field gets the OR of (1<<markType) across all
+ * its children (this definition allows children to use different markTypes).
  *
  * The planner also adds resjunk output columns to the plan that carry
  * information sufficient to identify the locked or fetched rows.  When

src/include/nodes/relation.h

@@ -107,6 +107,8 @@ typedef struct PlannerGlobal
 
 	List	   *resultRelations;	/* "flat" list of integer RT indexes */
 
+	List   *nonleafResultRelations; /* "flat" list of integer RT indexes */
+
 	List	   *relationOids;	/* OIDs of relations the plan depends on */
 
 	List	   *invalItems;		/* other dependencies, as PlanInvalItems */
@@ -248,6 +250,8 @@ typedef struct PlannerInfo
 
 	List	   *append_rel_list;	/* list of AppendRelInfos */
 
+	List	   *pcinfo_list;	/* list of PartitionedChildRelInfos */
+
 	List	   *rowMarks;		/* list of PlanRowMarks */
 
 	List	   *placeholder_list;		/* list of PlaceHolderInfos */
@@ -1116,6 +1120,8 @@ typedef struct CustomPath
 typedef struct AppendPath
 {
 	Path		path;
+	/* RT indexes of non-leaf tables in a partition tree */
+	List	   *partitioned_rels;
 	List	   *subpaths;		/* list of component Paths */
 } AppendPath;
 
@@ -1134,6 +1140,8 @@ typedef struct AppendPath
 typedef struct MergeAppendPath
 {
 	Path		path;
+	/* RT indexes of non-leaf tables in a partition tree */
+	List	   *partitioned_rels;
 	List	   *subpaths;		/* list of component Paths */
 	double		limit_tuples;	/* hard limit on output tuples, or -1 */
 } MergeAppendPath;
@@ -1482,6 +1490,8 @@ typedef struct ModifyTablePath
 	CmdType		operation;		/* INSERT, UPDATE, or DELETE */
 	bool		canSetTag;		/* do we set the command tag/es_processed? */
 	Index		nominalRelation;	/* Parent RT index for use of EXPLAIN */
+	/* RT indexes of non-leaf tables in a partition tree */
+	List	   *partitioned_rels;
 	List	   *resultRelations;	/* integer list of RT indexes */
 	List	   *subpaths;		/* Path(s) producing source data */
 	List	   *subroots;		/* per-target-table PlannerInfos */
@@ -1836,10 +1846,10 @@ typedef struct SpecialJoinInfo
  *
  * When we expand an inheritable table or a UNION-ALL subselect into an
  * "append relation" (essentially, a list of child RTEs), we build an
- * AppendRelInfo for each child RTE.  The list of AppendRelInfos indicates
- * which child RTEs must be included when expanding the parent, and each
- * node carries information needed to translate Vars referencing the parent
- * into Vars referencing that child.
+ * AppendRelInfo for each non-partitioned child RTE.  The list of
+ * AppendRelInfos indicates which child RTEs must be included when expanding
+ * the parent, and each node carries information needed to translate Vars
+ * referencing the parent into Vars referencing that child.
  *
  * These structs are kept in the PlannerInfo node's append_rel_list.
  * Note that we just throw all the structs into one list, and scan the
@@ -1913,6 +1923,25 @@ typedef struct AppendRelInfo
 	Oid			parent_reloid;	/* OID of parent relation */
 } AppendRelInfo;
 
+/*
+ * For a partitioned table, this maps its RT index to the list of RT indexes
+ * of the partitioned child tables in the partition tree.  We need to
+ * separately store this information, because we do not create AppendRelInfos
+ * for the partitioned child tables of a parent table, since AppendRelInfos
+ * contain information that is unnecessary for the partitioned child tables.
+ * The child_rels list must contain at least one element, because the parent
+ * partitioned table is itself counted as a child.
+ *
+ * These structs are kept in the PlannerInfo node's pcinfo_list.
+ */
+typedef struct PartitionedChildRelInfo
+{
+	NodeTag		type;
+
+	Index		parent_relid;
+	List	   *child_rels;
+} PartitionedChildRelInfo;
+
 /*
  * For each distinct placeholder expression generated during planning, we
  * store a PlaceHolderInfo node in the PlannerInfo node's placeholder_list.

src/include/optimizer/pathnode.h

@@ -64,12 +64,14 @@ extern BitmapOrPath *create_bitmap_or_path(PlannerInfo *root,
 extern TidPath *create_tidscan_path(PlannerInfo *root, RelOptInfo *rel,
 					List *tidquals, Relids required_outer);
 extern AppendPath *create_append_path(RelOptInfo *rel, List *subpaths,
-				   Relids required_outer, int parallel_workers);
+				   Relids required_outer, int parallel_workers,
+				   List *partitioned_rels);
 extern MergeAppendPath *create_merge_append_path(PlannerInfo *root,
 						 RelOptInfo *rel,
 						 List *subpaths,
 						 List *pathkeys,
-						 Relids required_outer);
+						 Relids required_outer,
+						 List *partitioned_rels);
 extern ResultPath *create_result_path(PlannerInfo *root, RelOptInfo *rel,
 				   PathTarget *target, List *resconstantqual);
 extern MaterialPath *create_material_path(RelOptInfo *rel, Path *subpath);
@@ -232,7 +234,7 @@ extern LockRowsPath *create_lockrows_path(PlannerInfo *root, RelOptInfo *rel,
 extern ModifyTablePath *create_modifytable_path(PlannerInfo *root,
 						RelOptInfo *rel,
 						CmdType operation, bool canSetTag,
-						Index nominalRelation,
+						Index nominalRelation, List *partitioned_rels,
 						List *resultRelations, List *subpaths,
 						List *subroots,
 						List *withCheckOptionLists, List *returningLists,

src/include/optimizer/planner.h

@@ -57,4 +57,6 @@ extern Expr *preprocess_phv_expression(PlannerInfo *root, Expr *expr);
 
 extern bool plan_cluster_use_sort(Oid tableOid, Oid indexOid);
 
+extern List *get_partitioned_child_rels(PlannerInfo *root, Index rti);
+
 #endif   /* PLANNER_H */

src/test/regress/expected/tablesample.out

@@ -322,12 +322,10 @@ explain (costs off)
                 QUERY PLAN                 
 -------------------------------------------
  Append
-   ->  Sample Scan on parted_sample
-         Sampling: bernoulli ('100'::real)
    ->  Sample Scan on parted_sample_1
          Sampling: bernoulli ('100'::real)
    ->  Sample Scan on parted_sample_2
          Sampling: bernoulli ('100'::real)
-(7 rows)
+(5 rows)
 
 drop table parted_sample, parted_sample_1, parted_sample_2;

src/test/regress/sql/inherit.sql

@@ -128,6 +128,34 @@ where bar.f1 = ss.f1;
 
 select tableoid::regclass::text as relname, bar.* from bar order by 1,2;
 
+-- Check UPDATE with *partitioned* inherited target and an appendrel subquery
+create table some_tab (a int);
+insert into some_tab values (0);
+create table some_tab_child () inherits (some_tab);
+insert into some_tab_child values (1);
+create table parted_tab (a int, b char) partition by list (a);
+create table parted_tab_part1 partition of parted_tab for values in (1);
+create table parted_tab_part2 partition of parted_tab for values in (2);
+create table parted_tab_part3 partition of parted_tab for values in (3);
+insert into parted_tab values (1, 'a'), (2, 'a'), (3, 'a');
+
+update parted_tab set b = 'b'
+from
+  (select a from some_tab union all select a+1 from some_tab) ss (a)
+where parted_tab.a = ss.a;
+select tableoid::regclass::text as relname, parted_tab.* from parted_tab order by 1,2;
+
+truncate parted_tab;
+insert into parted_tab values (1, 'a'), (2, 'a'), (3, 'a');
+update parted_tab set b = 'b'
+from
+  (select 0 from parted_tab union all select 1 from parted_tab) ss (a)
+where parted_tab.a = ss.a;
+select tableoid::regclass::text as relname, parted_tab.* from parted_tab order by 1,2;
+
+drop table parted_tab;
+drop table some_tab cascade;
+
 /* Test multiple inheritance of column defaults */
 
 CREATE TABLE firstparent (tomorrow date default now()::date + 1);