Disable support for partitionwise joins in problematic cases.

Commit f49842d1, which added support for partitionwise joins, built the
child's tlist by applying adjust_appendrel_attrs() to the parent's.  So in
the case where the parent's included a whole-row Var for the parent, the
child's contained a ConvertRowtypeExpr.  To cope with that, that commit
added code to the planner, such as setrefs.c, but some code paths still
assumed that the tlist for a scan (or join) rel would only include Vars
and PlaceHolderVars, which was true before that commit, causing errors:

* When creating an explicit sort node for an input path for a mergejoin
  path for a child join, prepare_sort_from_pathkeys() threw the 'could not
  find pathkey item to sort' error.
* When deparsing a relation participating in a pushed down child join as a
  subquery in contrib/postgres_fdw, get_relation_column_alias_ids() threw
  the 'unexpected expression in subquery output' error.
* When performing set_plan_references() on a local join plan generated by
  contrib/postgres_fdw for EvalPlanQual support for a pushed down child
  join, fix_join_expr() threw the 'variable not found in subplan target
  lists' error.

To fix these, two approaches have been proposed: one by Ashutosh Bapat and
one by me.  While the former keeps building the child's tlist with a
ConvertRowtypeExpr, the latter builds it with a whole-row Var for the
child not to violate the planner assumption, and tries to fix it up later,
But both approaches need more work, so refuse to generate partitionwise
join paths when whole-row Vars are involved, instead.  We don't need to
handle ConvertRowtypeExprs in the child's tlists for now, so this commit
also removes the changes to the planner.

Previously, partitionwise join computed attr_needed data for each child
separately, and built the child join's tlist using that data, which also
required an extra step for adding PlaceHolderVars to that tlist, but it
would be more efficient to build it from the parent join's tlist through
the adjust_appendrel_attrs() transformation.  So this commit builds that
list that way, and simplifies build_joinrel_tlist() and placeholder.c as
well as part of set_append_rel_size() to basically what they were before
partitionwise join went in.

Back-patch to PG11 where partitionwise join was introduced.

Report by Rajkumar Raghuwanshi.  Analysis by Ashutosh Bapat, who also
provided some of regression tests.  Patch by me, reviewed by Robert Haas.

Discussion: https://postgr.es/m/CAKcux6ktu-8tefLWtQuuZBYFaZA83vUzuRd7c1YHC-yEWyYFpg@mail.gmail.com

contrib/postgres_fdw/expected/postgres_fdw.out

@@ -8337,8 +8337,9 @@ ALTER TABLE fprt2_p1 SET (autovacuum_enabled = 'false');
 ALTER TABLE fprt2_p2 SET (autovacuum_enabled = 'false');
 INSERT INTO fprt2_p1 SELECT i, i, to_char(i/50, 'FM0000') FROM generate_series(0, 249, 3) i;
 INSERT INTO fprt2_p2 SELECT i, i, to_char(i/50, 'FM0000') FROM generate_series(250, 499, 3) i;
-CREATE FOREIGN TABLE ftprt2_p1 PARTITION OF fprt2 FOR VALUES FROM (0) TO (250)
+CREATE FOREIGN TABLE ftprt2_p1 (b int, c varchar, a int)
 	SERVER loopback OPTIONS (table_name 'fprt2_p1', use_remote_estimate 'true');
+ALTER TABLE fprt2 ATTACH PARTITION ftprt2_p1 FOR VALUES FROM (0) TO (250);
 CREATE FOREIGN TABLE ftprt2_p2 PARTITION OF fprt2 FOR VALUES FROM (250) TO (500)
 	SERVER loopback OPTIONS (table_name 'fprt2_p2', use_remote_estimate 'true');
 ANALYZE fprt2;
@@ -8389,28 +8390,42 @@ SELECT t1.a,t2.b,t2.c FROM fprt1 t1 LEFT JOIN (SELECT * FROM fprt2 WHERE a < 10)
  8 |   | 
 (5 rows)
 
--- with whole-row reference
+-- with whole-row reference; partitionwise join does not apply
 EXPLAIN (COSTS OFF)
-SELECT t1,t2 FROM fprt1 t1 JOIN fprt2 t2 ON (t1.a = t2.b and t1.b = t2.a) WHERE t1.a % 25 =0 ORDER BY 1,2;
+SELECT t1.wr, t2.wr FROM (SELECT t1 wr, a FROM fprt1 t1 WHERE t1.a % 25 = 0) t1 FULL JOIN (SELECT t2 wr, b FROM fprt2 t2 WHERE t2.b % 25 = 0) t2 ON (t1.a = t2.b) ORDER BY 1,2;
                        QUERY PLAN                       
----------------------------------------------------------------------------------
+--------------------------------------------------------
  Sort
    Sort Key: ((t1.*)::fprt1), ((t2.*)::fprt2)
+   ->  Hash Full Join
+         Hash Cond: (t1.a = t2.b)
          ->  Append
-         ->  Foreign Scan
-               Relations: (public.ftprt1_p1 t1) INNER JOIN (public.ftprt2_p1 t2)
-         ->  Foreign Scan
-               Relations: (public.ftprt1_p2 t1) INNER JOIN (public.ftprt2_p2 t2)
-(7 rows)
+               ->  Foreign Scan on ftprt1_p1 t1
+               ->  Foreign Scan on ftprt1_p2 t1_1
+         ->  Hash
+               ->  Append
+                     ->  Foreign Scan on ftprt2_p1 t2
+                     ->  Foreign Scan on ftprt2_p2 t2_1
+(11 rows)
 
-SELECT t1,t2 FROM fprt1 t1 JOIN fprt2 t2 ON (t1.a = t2.b and t1.b = t2.a) WHERE t1.a % 25 =0 ORDER BY 1,2;
-       t1       |       t2       
+SELECT t1.wr, t2.wr FROM (SELECT t1 wr, a FROM fprt1 t1 WHERE t1.a % 25 = 0) t1 FULL JOIN (SELECT t2 wr, b FROM fprt2 t2 WHERE t2.b % 25 = 0) t2 ON (t1.a = t2.b) ORDER BY 1,2;
+       wr       |       wr       
 ----------------+----------------
  (0,0,0000)     | (0,0,0000)
+ (50,50,0001)   | 
+ (100,100,0002) | 
  (150,150,0003) | (150,150,0003)
+ (200,200,0004) | 
  (250,250,0005) | (250,250,0005)
+ (300,300,0006) | 
+ (350,350,0007) | 
  (400,400,0008) | (400,400,0008)
-(4 rows)
+ (450,450,0009) | 
+                | (75,75,0001)
+                | (225,225,0004)
+                | (325,325,0006)
+                | (475,475,0009)
+(14 rows)
 
 -- join with lateral reference
 EXPLAIN (COSTS OFF)
@@ -8474,6 +8489,34 @@ SELECT t1.a, t1.phv, t2.b, t2.phv FROM (SELECT 't1_phv' phv, * FROM fprt1 WHERE
      |        | 475 | t2_phv
 (14 rows)
 
+-- test FOR UPDATE; partitionwise join does not apply
+EXPLAIN (COSTS OFF)
+SELECT t1.a, t2.b FROM fprt1 t1 INNER JOIN fprt2 t2 ON (t1.a = t2.b) WHERE t1.a % 25 = 0 ORDER BY 1,2 FOR UPDATE OF t1;
+                          QUERY PLAN                          
+--------------------------------------------------------------
+ LockRows
+   ->  Sort
+         Sort Key: t1.a
+         ->  Hash Join
+               Hash Cond: (t2.b = t1.a)
+               ->  Append
+                     ->  Foreign Scan on ftprt2_p1 t2
+                     ->  Foreign Scan on ftprt2_p2 t2_1
+               ->  Hash
+                     ->  Append
+                           ->  Foreign Scan on ftprt1_p1 t1
+                           ->  Foreign Scan on ftprt1_p2 t1_1
+(12 rows)
+
+SELECT t1.a, t2.b FROM fprt1 t1 INNER JOIN fprt2 t2 ON (t1.a = t2.b) WHERE t1.a % 25 = 0 ORDER BY 1,2 FOR UPDATE OF t1;
+  a  |  b  
+-----+-----
+   0 |   0
+ 150 | 150
+ 250 | 250
+ 400 | 400
+(4 rows)
+
 RESET enable_partitionwise_join;
 -- ===================================================================
 -- test partitionwise aggregates

contrib/postgres_fdw/sql/postgres_fdw.sql

@@ -2263,8 +2263,9 @@ ALTER TABLE fprt2_p1 SET (autovacuum_enabled = 'false');
 ALTER TABLE fprt2_p2 SET (autovacuum_enabled = 'false');
 INSERT INTO fprt2_p1 SELECT i, i, to_char(i/50, 'FM0000') FROM generate_series(0, 249, 3) i;
 INSERT INTO fprt2_p2 SELECT i, i, to_char(i/50, 'FM0000') FROM generate_series(250, 499, 3) i;
-CREATE FOREIGN TABLE ftprt2_p1 PARTITION OF fprt2 FOR VALUES FROM (0) TO (250)
+CREATE FOREIGN TABLE ftprt2_p1 (b int, c varchar, a int)
 	SERVER loopback OPTIONS (table_name 'fprt2_p1', use_remote_estimate 'true');
+ALTER TABLE fprt2 ATTACH PARTITION ftprt2_p1 FOR VALUES FROM (0) TO (250);
 CREATE FOREIGN TABLE ftprt2_p2 PARTITION OF fprt2 FOR VALUES FROM (250) TO (500)
 	SERVER loopback OPTIONS (table_name 'fprt2_p2', use_remote_estimate 'true');
 ANALYZE fprt2;
@@ -2281,10 +2282,10 @@ EXPLAIN (COSTS OFF)
 SELECT t1.a,t2.b,t2.c FROM fprt1 t1 LEFT JOIN (SELECT * FROM fprt2 WHERE a < 10) t2 ON (t1.a = t2.b and t1.b = t2.a) WHERE t1.a < 10 ORDER BY 1,2,3;
 SELECT t1.a,t2.b,t2.c FROM fprt1 t1 LEFT JOIN (SELECT * FROM fprt2 WHERE a < 10) t2 ON (t1.a = t2.b and t1.b = t2.a) WHERE t1.a < 10 ORDER BY 1,2,3;
 
--- with whole-row reference
+-- with whole-row reference; partitionwise join does not apply
 EXPLAIN (COSTS OFF)
-SELECT t1,t2 FROM fprt1 t1 JOIN fprt2 t2 ON (t1.a = t2.b and t1.b = t2.a) WHERE t1.a % 25 =0 ORDER BY 1,2;
-SELECT t1,t2 FROM fprt1 t1 JOIN fprt2 t2 ON (t1.a = t2.b and t1.b = t2.a) WHERE t1.a % 25 =0 ORDER BY 1,2;
+SELECT t1.wr, t2.wr FROM (SELECT t1 wr, a FROM fprt1 t1 WHERE t1.a % 25 = 0) t1 FULL JOIN (SELECT t2 wr, b FROM fprt2 t2 WHERE t2.b % 25 = 0) t2 ON (t1.a = t2.b) ORDER BY 1,2;
+SELECT t1.wr, t2.wr FROM (SELECT t1 wr, a FROM fprt1 t1 WHERE t1.a % 25 = 0) t1 FULL JOIN (SELECT t2 wr, b FROM fprt2 t2 WHERE t2.b % 25 = 0) t2 ON (t1.a = t2.b) ORDER BY 1,2;
 
 -- join with lateral reference
 EXPLAIN (COSTS OFF)
@@ -2296,6 +2297,11 @@ EXPLAIN (COSTS OFF)
 SELECT t1.a, t1.phv, t2.b, t2.phv FROM (SELECT 't1_phv' phv, * FROM fprt1 WHERE a % 25 = 0) t1 FULL JOIN (SELECT 't2_phv' phv, * FROM fprt2 WHERE b % 25 = 0) t2 ON (t1.a = t2.b) ORDER BY t1.a, t2.b;
 SELECT t1.a, t1.phv, t2.b, t2.phv FROM (SELECT 't1_phv' phv, * FROM fprt1 WHERE a % 25 = 0) t1 FULL JOIN (SELECT 't2_phv' phv, * FROM fprt2 WHERE b % 25 = 0) t2 ON (t1.a = t2.b) ORDER BY t1.a, t2.b;
 
+-- test FOR UPDATE; partitionwise join does not apply
+EXPLAIN (COSTS OFF)
+SELECT t1.a, t2.b FROM fprt1 t1 INNER JOIN fprt2 t2 ON (t1.a = t2.b) WHERE t1.a % 25 = 0 ORDER BY 1,2 FOR UPDATE OF t1;
+SELECT t1.a, t2.b FROM fprt1 t1 INNER JOIN fprt2 t2 ON (t1.a = t2.b) WHERE t1.a % 25 = 0 ORDER BY 1,2 FOR UPDATE OF t1;
+
 RESET enable_partitionwise_join;
 
 

src/backend/nodes/outfuncs.c

@@ -2368,6 +2368,7 @@ _outRelOptInfo(StringInfo str, const RelOptInfo *node)
 	WRITE_UINT_FIELD(baserestrict_min_security);
 	WRITE_NODE_FIELD(joininfo);
 	WRITE_BOOL_FIELD(has_eclass_joins);
+	WRITE_BOOL_FIELD(consider_partitionwise_join);
 	WRITE_BITMAPSET_FIELD(top_parent_relids);
 	WRITE_NODE_FIELD(partitioned_child_rels);
 }

src/backend/optimizer/path/allpaths.c

@@ -909,6 +909,17 @@ set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
 		did_pruning = true;
 	}
 
+	/*
+	 * If this is a partitioned baserel, set the consider_partitionwise_join
+	 * flag; currently, we only consider partitionwise joins with the baserel
+	 * if its targetlist doesn't contain a whole-row Var.
+	 */
+	if (enable_partitionwise_join &&
+		rel->reloptkind == RELOPT_BASEREL &&
+		rte->relkind == RELKIND_PARTITIONED_TABLE &&
+		rel->attr_needed[InvalidAttrNumber - rel->min_attr] == NULL)
+		rel->consider_partitionwise_join = true;
+
 	/*
 	 * Initialize to compute size estimates for whole append relation.
 	 *
@@ -956,54 +967,6 @@ set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
 		childrel = find_base_rel(root, childRTindex);
 		Assert(childrel->reloptkind == RELOPT_OTHER_MEMBER_REL);
 
-		if (rel->part_scheme)
-		{
-			AttrNumber	attno;
-
-			/*
-			 * We need attr_needed data for building targetlist of a join
-			 * relation representing join between matching partitions for
-			 * partitionwise join. A given attribute of a child will be needed
-			 * in the same highest joinrel where the corresponding attribute
-			 * of parent is needed. Hence it suffices to use the same Relids
-			 * set for parent and child.
-			 */
-			for (attno = rel->min_attr; attno <= rel->max_attr; attno++)
-			{
-				int			index = attno - rel->min_attr;
-				Relids		attr_needed = rel->attr_needed[index];
-
-				/* System attributes do not need translation. */
-				if (attno <= 0)
-				{
-					Assert(rel->min_attr == childrel->min_attr);
-					childrel->attr_needed[index] = attr_needed;
-				}
-				else
-				{
-					Var		   *var = list_nth_node(Var,
-													appinfo->translated_vars,
-													attno - 1);
-					int			child_index;
-
-					/*
-					 * Ignore any column dropped from the parent.
-					 * Corresponding Var won't have any translation. It won't
-					 * have attr_needed information, since it can not be
-					 * referenced in the query.
-					 */
-					if (var == NULL)
-					{
-						Assert(attr_needed == NULL);
-						continue;
-					}
-
-					child_index = var->varattno - childrel->min_attr;
-					childrel->attr_needed[child_index] = attr_needed;
-				}
-			}
-		}
-
 		/*
 		 * Copy/Modify targetlist. Even if this child is deemed empty, we need
 		 * its targetlist in case it falls on nullable side in a child-join
@@ -1180,6 +1143,22 @@ set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
 								   (Node *) rel->joininfo,
 								   1, &appinfo);
 
+		/*
+		 * Note: we could compute appropriate attr_needed data for the child's
+		 * variables, by transforming the parent's attr_needed through the
+		 * translated_vars mapping.  However, currently there's no need
+		 * because attr_needed is only examined for base relations not
+		 * otherrels.  So we just leave the child's attr_needed empty.
+		 */
+
+		/*
+		 * If we consider partitionwise joins with the parent rel, do the same
+		 * for partitioned child rels.
+		 */
+		if (rel->consider_partitionwise_join &&
+			childRTE->relkind == RELKIND_PARTITIONED_TABLE)
+			childrel->consider_partitionwise_join = true;
+
 		/*
 		 * If parallelism is allowable for this query in general, see whether
 		 * it's allowable for this childrel in particular.  But if we've
@@ -3538,6 +3517,9 @@ generate_partitionwise_join_paths(PlannerInfo *root, RelOptInfo *rel)
 	if (!IS_PARTITIONED_REL(rel))
 		return;
 
+	/* The relation should have consider_partitionwise_join set. */
+	Assert(rel->consider_partitionwise_join);
+
 	/* Guard against stack overflow due to overly deep partition hierarchy. */
 	check_stack_depth();
 

src/backend/optimizer/path/joinrels.c

@@ -1322,6 +1322,9 @@ try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
 	if (!IS_PARTITIONED_REL(joinrel))
 		return;
 
+	/* The join relation should have consider_partitionwise_join set. */
+	Assert(joinrel->consider_partitionwise_join);
+
 	/*
 	 * Since this join relation is partitioned, all the base relations
 	 * participating in this join must be partitioned and so are all the
@@ -1330,6 +1333,10 @@ try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
 	Assert(IS_PARTITIONED_REL(rel1) && IS_PARTITIONED_REL(rel2));
 	Assert(REL_HAS_ALL_PART_PROPS(rel1) && REL_HAS_ALL_PART_PROPS(rel2));
 
+	/* The joining relations should have consider_partitionwise_join set. */
+	Assert(rel1->consider_partitionwise_join &&
+		   rel2->consider_partitionwise_join);
+
 	/*
 	 * The partition scheme of the join relation should match that of the
 	 * joining relations.

src/backend/optimizer/plan/setrefs.c

@@ -41,9 +41,6 @@ typedef struct
 	int			num_vars;		/* number of plain Var tlist entries */
 	bool		has_ph_vars;	/* are there PlaceHolderVar entries? */
 	bool		has_non_vars;	/* are there other entries? */
-	bool		has_conv_whole_rows;	/* are there ConvertRowtypeExpr
-										 * entries encapsulating a whole-row
-										 * Var? */
 	tlist_vinfo vars[FLEXIBLE_ARRAY_MEMBER];	/* has num_vars entries */
 } indexed_tlist;
 
@@ -143,7 +140,6 @@ static List *set_returning_clause_references(PlannerInfo *root,
 								int rtoffset);
 static bool extract_query_dependencies_walker(Node *node,
 								  PlannerInfo *context);
-static bool is_converted_whole_row_reference(Node *node);
 
 /*****************************************************************************
  *
@@ -1997,7 +1993,6 @@ build_tlist_index(List *tlist)
 	itlist->tlist = tlist;
 	itlist->has_ph_vars = false;
 	itlist->has_non_vars = false;
-	itlist->has_conv_whole_rows = false;
 
 	/* Find the Vars and fill in the index array */
 	vinfo = itlist->vars;
@@ -2016,8 +2011,6 @@ build_tlist_index(List *tlist)
 		}
 		else if (tle->expr && IsA(tle->expr, PlaceHolderVar))
 			itlist->has_ph_vars = true;
-		else if (is_converted_whole_row_reference((Node *) tle->expr))
-			itlist->has_conv_whole_rows = true;
 		else
 			itlist->has_non_vars = true;
 	}
@@ -2033,10 +2026,7 @@ build_tlist_index(List *tlist)
  * This is like build_tlist_index, but we only index tlist entries that
  * are Vars belonging to some rel other than the one specified.  We will set
  * has_ph_vars (allowing PlaceHolderVars to be matched), but not has_non_vars
- * (so nothing other than Vars and PlaceHolderVars can be matched). In case of
- * DML, where this function will be used, returning lists from child relations
- * will be appended similar to a simple append relation. That does not require
- * fixing ConvertRowtypeExpr references. So, those are not considered here.
+ * (so nothing other than Vars and PlaceHolderVars can be matched).
  */
 static indexed_tlist *
 build_tlist_index_other_vars(List *tlist, Index ignore_rel)
@@ -2053,7 +2043,6 @@ build_tlist_index_other_vars(List *tlist, Index ignore_rel)
 	itlist->tlist = tlist;
 	itlist->has_ph_vars = false;
 	itlist->has_non_vars = false;
-	itlist->has_conv_whole_rows = false;
 
 	/* Find the desired Vars and fill in the index array */
 	vinfo = itlist->vars;
@@ -2256,7 +2245,6 @@ static Node *
 fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
 {
 	Var		   *newvar;
-	bool		converted_whole_row;
 
 	if (node == NULL)
 		return NULL;
@@ -2326,12 +2314,8 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
 	}
 	if (IsA(node, Param))
 		return fix_param_node(context->root, (Param *) node);
-
 	/* Try matching more complex expressions too, if tlists have any */
-	converted_whole_row = is_converted_whole_row_reference(node);
-	if (context->outer_itlist &&
-		(context->outer_itlist->has_non_vars ||
-		 (context->outer_itlist->has_conv_whole_rows && converted_whole_row)))
+	if (context->outer_itlist && context->outer_itlist->has_non_vars)
 	{
 		newvar = search_indexed_tlist_for_non_var((Expr *) node,
 												  context->outer_itlist,
@@ -2339,9 +2323,7 @@ fix_join_expr_mutator(Node *node, fix_join_expr_context *context)
 		if (newvar)
 			return (Node *) newvar;
 	}
-	if (context->inner_itlist &&
-		(context->inner_itlist->has_non_vars ||
-		 (context->inner_itlist->has_conv_whole_rows && converted_whole_row)))
+	if (context->inner_itlist && context->inner_itlist->has_non_vars)
 	{
 		newvar = search_indexed_tlist_for_non_var((Expr *) node,
 												  context->inner_itlist,
@@ -2461,9 +2443,7 @@ fix_upper_expr_mutator(Node *node, fix_upper_expr_context *context)
 		/* If no match, just fall through to process it normally */
 	}
 	/* Try matching more complex expressions too, if tlist has any */
-	if (context->subplan_itlist->has_non_vars ||
-		(context->subplan_itlist->has_conv_whole_rows &&
-		 is_converted_whole_row_reference(node)))
+	if (context->subplan_itlist->has_non_vars)
 	{
 		newvar = search_indexed_tlist_for_non_var((Expr *) node,
 												  context->subplan_itlist,
@@ -2670,33 +2650,3 @@ extract_query_dependencies_walker(Node *node, PlannerInfo *context)
 	return expression_tree_walker(node, extract_query_dependencies_walker,
 								  (void *) context);
 }
-
-/*
- * is_converted_whole_row_reference
- *		If the given node is a ConvertRowtypeExpr encapsulating a whole-row
- *		reference as implicit cast, return true. Otherwise return false.
- */
-static bool
-is_converted_whole_row_reference(Node *node)
-{
-	ConvertRowtypeExpr *convexpr;
-
-	if (!node || !IsA(node, ConvertRowtypeExpr))
-		return false;
-
-	/* Traverse nested ConvertRowtypeExpr's. */
-	convexpr = castNode(ConvertRowtypeExpr, node);
-	while (convexpr->convertformat == COERCE_IMPLICIT_CAST &&
-		   IsA(convexpr->arg, ConvertRowtypeExpr))
-		convexpr = castNode(ConvertRowtypeExpr, convexpr->arg);
-
-	if (IsA(convexpr->arg, Var))
-	{
-		Var		   *var = castNode(Var, convexpr->arg);
-
-		if (var->varattno == 0)
-			return true;
-	}
-
-	return false;
-}

src/backend/optimizer/util/placeholder.c

@@ -20,7 +20,6 @@
 #include "optimizer/pathnode.h"
 #include "optimizer/placeholder.h"
 #include "optimizer/planmain.h"
-#include "optimizer/prep.h"
 #include "optimizer/var.h"
 #include "utils/lsyscache.h"
 
@@ -415,10 +414,6 @@ add_placeholders_to_joinrel(PlannerInfo *root, RelOptInfo *joinrel,
 	Relids		relids = joinrel->relids;
 	ListCell   *lc;
 
-	/* This function is called only on the parent relations. */
-	Assert(!IS_OTHER_REL(joinrel) && !IS_OTHER_REL(outer_rel) &&
-		   !IS_OTHER_REL(inner_rel));
-
 	foreach(lc, root->placeholder_list)
 	{
 		PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(lc);
@@ -464,56 +459,3 @@ add_placeholders_to_joinrel(PlannerInfo *root, RelOptInfo *joinrel,
 		}
 	}
 }
-
-/*
- * add_placeholders_to_child_joinrel
- *		Translate the PHVs in parent's targetlist and add them to the child's
- *		targetlist. Also adjust the cost
- */
-void
-add_placeholders_to_child_joinrel(PlannerInfo *root, RelOptInfo *childrel,
-								  RelOptInfo *parentrel)
-{
-	ListCell   *lc;
-	AppendRelInfo **appinfos;
-	int			nappinfos;
-
-	Assert(IS_JOIN_REL(childrel) && IS_JOIN_REL(parentrel));
-	Assert(IS_OTHER_REL(childrel));
-
-	/* Nothing to do if no PHVs. */
-	if (root->placeholder_list == NIL)
-		return;
-
-	appinfos = find_appinfos_by_relids(root, childrel->relids, &nappinfos);
-	foreach(lc, parentrel->reltarget->exprs)
-	{
-		PlaceHolderVar *phv = lfirst(lc);
-
-		if (IsA(phv, PlaceHolderVar))
-		{
-			/*
-			 * In case the placeholder Var refers to any of the parent
-			 * relations, translate it to refer to the corresponding child.
-			 */
-			if (bms_overlap(phv->phrels, parentrel->relids) &&
-				childrel->reloptkind == RELOPT_OTHER_JOINREL)
-			{
-				phv = (PlaceHolderVar *) adjust_appendrel_attrs(root,
-																(Node *) phv,
-																nappinfos,
-																appinfos);
-			}
-
-			childrel->reltarget->exprs = lappend(childrel->reltarget->exprs,
-												 phv);
-		}
-	}
-
-	/* Adjust the cost and width of child targetlist. */
-	childrel->reltarget->cost.startup = parentrel->reltarget->cost.startup;
-	childrel->reltarget->cost.per_tuple = parentrel->reltarget->cost.per_tuple;
-	childrel->reltarget->width = parentrel->reltarget->width;
-
-	pfree(appinfos);
-}

src/backend/optimizer/util/relnode.c

@@ -57,6 +57,11 @@ static void add_join_rel(PlannerInfo *root, RelOptInfo *joinrel);
 static void build_joinrel_partition_info(RelOptInfo *joinrel,
 							 RelOptInfo *outer_rel, RelOptInfo *inner_rel,
 							 List *restrictlist, JoinType jointype);
+static void build_child_join_reltarget(PlannerInfo *root,
+						   RelOptInfo *parentrel,
+						   RelOptInfo *childrel,
+						   int nappinfos,
+						   AppendRelInfo **appinfos);
 
 
 /*
@@ -188,6 +193,7 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptInfo *parent)
 	rel->baserestrict_min_security = UINT_MAX;
 	rel->joininfo = NIL;
 	rel->has_eclass_joins = false;
+	rel->consider_partitionwise_join = false; /* might get changed later */
 	rel->part_scheme = NULL;
 	rel->nparts = 0;
 	rel->boundinfo = NULL;
@@ -602,6 +608,7 @@ build_join_rel(PlannerInfo *root,
 	joinrel->baserestrict_min_security = UINT_MAX;
 	joinrel->joininfo = NIL;
 	joinrel->has_eclass_joins = false;
+	joinrel->consider_partitionwise_join = false; /* might get changed later */
 	joinrel->top_parent_relids = NULL;
 	joinrel->part_scheme = NULL;
 	joinrel->nparts = 0;
@@ -732,6 +739,9 @@ build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
 	/* Only joins between "other" relations land here. */
 	Assert(IS_OTHER_REL(outer_rel) && IS_OTHER_REL(inner_rel));
 
+	/* The parent joinrel should have consider_partitionwise_join set. */
+	Assert(parent_joinrel->consider_partitionwise_join);
+
 	joinrel->reloptkind = RELOPT_OTHER_JOINREL;
 	joinrel->relids = bms_union(outer_rel->relids, inner_rel->relids);
 	joinrel->rows = 0;
@@ -773,6 +783,7 @@ build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
 	joinrel->baserestrictcost.per_tuple = 0;
 	joinrel->joininfo = NIL;
 	joinrel->has_eclass_joins = false;
+	joinrel->consider_partitionwise_join = false; /* might get changed later */
 	joinrel->top_parent_relids = NULL;
 	joinrel->part_scheme = NULL;
 	joinrel->nparts = 0;
@@ -789,14 +800,13 @@ build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
 	/* Compute information relevant to foreign relations. */
 	set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
 
-	/* Build targetlist */
-	build_joinrel_tlist(root, joinrel, outer_rel);
-	build_joinrel_tlist(root, joinrel, inner_rel);
-	/* Add placeholder variables. */
-	add_placeholders_to_child_joinrel(root, joinrel, parent_joinrel);
+	appinfos = find_appinfos_by_relids(root, joinrel->relids, &nappinfos);
+
+	/* Set up reltarget struct */
+	build_child_join_reltarget(root, parent_joinrel, joinrel,
+							   nappinfos, appinfos);
 
 	/* Construct joininfo list. */
-	appinfos = find_appinfos_by_relids(root, joinrel->relids, &nappinfos);
 	joinrel->joininfo = (List *) adjust_appendrel_attrs(root,
 														(Node *) parent_joinrel->joininfo,
 														nappinfos,
@@ -826,7 +836,6 @@ build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
 	/* Child joinrel is parallel safe if parent is parallel safe. */
 	joinrel->consider_parallel = parent_joinrel->consider_parallel;
 
-
 	/* Set estimates of the child-joinrel's size. */
 	set_joinrel_size_estimates(root, joinrel, outer_rel, inner_rel,
 							   sjinfo, restrictlist);
@@ -895,15 +904,9 @@ static void
 build_joinrel_tlist(PlannerInfo *root, RelOptInfo *joinrel,
 					RelOptInfo *input_rel)
 {
-	Relids		relids;
+	Relids		relids = joinrel->relids;
 	ListCell   *vars;
 
-	/* attrs_needed refers to parent relids and not those of a child. */
-	if (joinrel->top_parent_relids)
-		relids = joinrel->top_parent_relids;
-	else
-		relids = joinrel->relids;
-
 	foreach(vars, input_rel->reltarget->exprs)
 	{
 		Var		   *var = (Var *) lfirst(vars);
@@ -919,54 +922,23 @@ build_joinrel_tlist(PlannerInfo *root, RelOptInfo *joinrel,
 
 		/*
 		 * Otherwise, anything in a baserel or joinrel targetlist ought to be
-		 * a Var. Children of a partitioned table may have ConvertRowtypeExpr
-		 * translating whole-row Var of a child to that of the parent.
-		 * Children of an inherited table or subquery child rels can not
-		 * directly participate in a join, so other kinds of nodes here.
+		 * a Var.  (More general cases can only appear in appendrel child
+		 * rels, which will never be seen here.)
 		 */
-		if (IsA(var, Var))
-		{
-			baserel = find_base_rel(root, var->varno);
-			ndx = var->varattno - baserel->min_attr;
-		}
-		else if (IsA(var, ConvertRowtypeExpr))
-		{
-			ConvertRowtypeExpr *child_expr = (ConvertRowtypeExpr *) var;
-			Var		   *childvar = (Var *) child_expr->arg;
-
-			/*
-			 * Child's whole-row references are converted to look like those
-			 * of parent using ConvertRowtypeExpr. There can be as many
-			 * ConvertRowtypeExpr decorations as the depth of partition tree.
-			 * The argument to the deepest ConvertRowtypeExpr is expected to
-			 * be a whole-row reference of the child.
-			 */
-			while (IsA(childvar, ConvertRowtypeExpr))
-			{
-				child_expr = (ConvertRowtypeExpr *) childvar;
-				childvar = (Var *) child_expr->arg;
-			}
-			Assert(IsA(childvar, Var) &&childvar->varattno == 0);
-
-			baserel = find_base_rel(root, childvar->varno);
-			ndx = 0 - baserel->min_attr;
-		}
-		else
+		if (!IsA(var, Var))
 			elog(ERROR, "unexpected node type in rel targetlist: %d",
 				 (int) nodeTag(var));
 
+		/* Get the Var's original base rel */
+		baserel = find_base_rel(root, var->varno);
 
-		/* Is the target expression still needed above this joinrel? */
+		/* Is it still needed above this joinrel? */
+		ndx = var->varattno - baserel->min_attr;
 		if (bms_nonempty_difference(baserel->attr_needed[ndx], relids))
 		{
 			/* Yup, add it to the output */
 			joinrel->reltarget->exprs = lappend(joinrel->reltarget->exprs, var);
-
-			/*
-			 * Vars have cost zero, so no need to adjust reltarget->cost. Even
-			 * if it's a ConvertRowtypeExpr, it will be computed only for the
-			 * base relation, costing nothing for a join.
-			 */
+			/* Vars have cost zero, so no need to adjust reltarget->cost */
 			joinrel->reltarget->width += baserel->attr_widths[ndx];
 		}
 	}
@@ -1626,16 +1598,18 @@ build_joinrel_partition_info(RelOptInfo *joinrel, RelOptInfo *outer_rel,
 
 	/*
 	 * We can only consider this join as an input to further partitionwise
-	 * joins if (a) the input relations are partitioned, (b) the partition
-	 * schemes match, and (c) we can identify an equi-join between the
-	 * partition keys.  Note that if it were possible for
-	 * have_partkey_equi_join to return different answers for the same joinrel
-	 * depending on which join ordering we try first, this logic would break.
-	 * That shouldn't happen, though, because of the way the query planner
-	 * deduces implied equalities and reorders the joins. Please see
-	 * optimizer/README for details.
+	 * joins if (a) the input relations are partitioned and have
+	 * consider_partitionwise_join=true, (b) the partition schemes match, and
+	 * (c) we can identify an equi-join between the partition keys.  Note that
+	 * if it were possible for have_partkey_equi_join to return different
+	 * answers for the same joinrel depending on which join ordering we try
+	 * first, this logic would break.  That shouldn't happen, though, because
+	 * of the way the query planner deduces implied equalities and reorders
+	 * the joins.  Please see optimizer/README for details.
 	 */
 	if (!IS_PARTITIONED_REL(outer_rel) || !IS_PARTITIONED_REL(inner_rel) ||
+		!outer_rel->consider_partitionwise_join ||
+		!inner_rel->consider_partitionwise_join ||
 		outer_rel->part_scheme != inner_rel->part_scheme ||
 		!have_partkey_equi_join(joinrel, outer_rel, inner_rel,
 								jointype, restrictlist))
@@ -1687,6 +1661,12 @@ build_joinrel_partition_info(RelOptInfo *joinrel, RelOptInfo *outer_rel,
 	joinrel->part_rels =
 		(RelOptInfo **) palloc0(sizeof(RelOptInfo *) * joinrel->nparts);
 
+	/*
+	 * Set the consider_partitionwise_join flag.
+	 */
+	Assert(outer_rel->consider_partitionwise_join);
+	Assert(inner_rel->consider_partitionwise_join);
+	joinrel->consider_partitionwise_join = true;
 
 	/*
 	 * Construct partition keys for the join.
@@ -1768,3 +1748,26 @@ build_joinrel_partition_info(RelOptInfo *joinrel, RelOptInfo *outer_rel,
 		joinrel->nullable_partexprs[cnt] = nullable_partexpr;
 	}
 }
+
+/*
+ * build_child_join_reltarget
+ *	  Set up a child-join relation's reltarget from a parent-join relation.
+ */
+static void
+build_child_join_reltarget(PlannerInfo *root,
+						   RelOptInfo *parentrel,
+						   RelOptInfo *childrel,
+						   int nappinfos,
+						   AppendRelInfo **appinfos)
+{
+	/* Build the targetlist */
+	childrel->reltarget->exprs = (List *)
+		adjust_appendrel_attrs(root,
+							   (Node *) parentrel->reltarget->exprs,
+							   nappinfos, appinfos);
+
+	/* Set the cost and width fields */
+	childrel->reltarget->cost.startup = parentrel->reltarget->cost.startup;
+	childrel->reltarget->cost.per_tuple = parentrel->reltarget->cost.per_tuple;
+	childrel->reltarget->width = parentrel->reltarget->width;
+}

src/include/nodes/relation.h

@@ -687,8 +687,12 @@ typedef struct RelOptInfo
 								 * involving this rel */
 	bool		has_eclass_joins;	/* T means joininfo is incomplete */
 
-	/* used by "other" relations */
-	Relids		top_parent_relids;	/* Relids of topmost parents */
+	/* used by partitionwise joins: */
+	bool		consider_partitionwise_join;	/* consider partitionwise
+												 * join paths? (if
+												 * partitioned rel) */
+	Relids		top_parent_relids;	/* Relids of topmost parents (if "other"
+									 * rel) */
 
 	/* used for partitioned relations */
 	PartitionScheme part_scheme;	/* Partitioning scheme. */

src/test/regress/expected/partition_aggregate.out

@@ -449,6 +449,38 @@ SELECT t1.x, sum(t1.y), count(*) FROM pagg_tab1 t1, pagg_tab2 t2 WHERE t1.x = t2
  24 |  900 |   100
 (5 rows)
 
+-- Check with whole-row reference; partitionwise aggregation does not apply
+EXPLAIN (COSTS OFF)
+SELECT t1.x, sum(t1.y), count(t1) FROM pagg_tab1 t1, pagg_tab2 t2 WHERE t1.x = t2.y GROUP BY t1.x ORDER BY 1, 2, 3;
+                         QUERY PLAN                          
+-------------------------------------------------------------
+ Sort
+   Sort Key: t1.x, (sum(t1.y)), (count(((t1.*)::pagg_tab1)))
+   ->  HashAggregate
+         Group Key: t1.x
+         ->  Hash Join
+               Hash Cond: (t1.x = t2.y)
+               ->  Append
+                     ->  Seq Scan on pagg_tab1_p1 t1
+                     ->  Seq Scan on pagg_tab1_p2 t1_1
+                     ->  Seq Scan on pagg_tab1_p3 t1_2
+               ->  Hash
+                     ->  Append
+                           ->  Seq Scan on pagg_tab2_p1 t2
+                           ->  Seq Scan on pagg_tab2_p2 t2_1
+                           ->  Seq Scan on pagg_tab2_p3 t2_2
+(15 rows)
+
+SELECT t1.x, sum(t1.y), count(t1) FROM pagg_tab1 t1, pagg_tab2 t2 WHERE t1.x = t2.y GROUP BY t1.x ORDER BY 1, 2, 3;
+ x  | sum  | count 
+----+------+-------
+  0 |  500 |   100
+  6 | 1100 |   100
+ 12 |  700 |   100
+ 18 | 1300 |   100
+ 24 |  900 |   100
+(5 rows)
+
 -- GROUP BY having other matching key
 EXPLAIN (COSTS OFF)
 SELECT t2.y, sum(t1.y), count(*) FROM pagg_tab1 t1, pagg_tab2 t2 WHERE t1.x = t2.y GROUP BY t2.y ORDER BY 1, 2, 3;

src/test/regress/expected/partition_join.out

@@ -62,33 +62,28 @@ SELECT t1.a, t1.c, t2.b, t2.c FROM prt1 t1, prt2 t2 WHERE t1.a = t2.b AND t1.b =
  450 | 0450 | 450 | 0450
 (4 rows)
 
--- left outer join, with whole-row reference
+-- left outer join, with whole-row reference; partitionwise join does not apply
 EXPLAIN (COSTS OFF)
 SELECT t1, t2 FROM prt1 t1 LEFT JOIN prt2 t2 ON t1.a = t2.b WHERE t1.b = 0 ORDER BY t1.a, t2.b;
                     QUERY PLAN                    
 --------------------------------------------------
  Sort
    Sort Key: t1.a, t2.b
-   ->  Append
    ->  Hash Right Join
          Hash Cond: (t2.b = t1.a)
+         ->  Append
                ->  Seq Scan on prt2_p1 t2
+               ->  Seq Scan on prt2_p2 t2_1
+               ->  Seq Scan on prt2_p3 t2_2
          ->  Hash
+               ->  Append
                      ->  Seq Scan on prt1_p1 t1
                            Filter: (b = 0)
-         ->  Hash Right Join
-               Hash Cond: (t2_1.b = t1_1.a)
-               ->  Seq Scan on prt2_p2 t2_1
-               ->  Hash
                      ->  Seq Scan on prt1_p2 t1_1
                            Filter: (b = 0)
-         ->  Hash Right Join
-               Hash Cond: (t2_2.b = t1_2.a)
-               ->  Seq Scan on prt2_p3 t2_2
-               ->  Hash
                      ->  Seq Scan on prt1_p3 t1_2
                            Filter: (b = 0)
-(21 rows)
+(16 rows)
 
 SELECT t1, t2 FROM prt1 t1 LEFT JOIN prt2 t2 ON t1.a = t2.b WHERE t1.b = 0 ORDER BY t1.a, t2.b;
       t1      |      t2      
@@ -1042,6 +1037,40 @@ SELECT t1.a, t2.b FROM (SELECT * FROM prt1 WHERE a < 450) t1 LEFT JOIN (SELECT *
  400 |    
 (9 rows)
 
+-- merge join when expression with whole-row reference needs to be sorted;
+-- partitionwise join does not apply
+EXPLAIN (COSTS OFF)
+SELECT t1.a, t2.b FROM prt1 t1, prt2 t2 WHERE t1::text = t2::text AND t1.a = t2.b ORDER BY t1.a;
+                                       QUERY PLAN                                        
+-----------------------------------------------------------------------------------------
+ Merge Join
+   Merge Cond: ((t1.a = t2.b) AND (((((t1.*)::prt1))::text) = ((((t2.*)::prt2))::text)))
+   ->  Sort
+         Sort Key: t1.a, ((((t1.*)::prt1))::text)
+         ->  Result
+               ->  Append
+                     ->  Seq Scan on prt1_p1 t1
+                     ->  Seq Scan on prt1_p2 t1_1
+                     ->  Seq Scan on prt1_p3 t1_2
+   ->  Sort
+         Sort Key: t2.b, ((((t2.*)::prt2))::text)
+         ->  Result
+               ->  Append
+                     ->  Seq Scan on prt2_p1 t2
+                     ->  Seq Scan on prt2_p2 t2_1
+                     ->  Seq Scan on prt2_p3 t2_2
+(16 rows)
+
+SELECT t1.a, t2.b FROM prt1 t1, prt2 t2 WHERE t1::text = t2::text AND t1.a = t2.b ORDER BY t1.a;
+ a  | b  
+----+----
+  0 |  0
+  6 |  6
+ 12 | 12
+ 18 | 18
+ 24 | 24
+(5 rows)
+
 RESET enable_hashjoin;
 RESET enable_nestloop;
 --

src/test/regress/sql/partition_aggregate.sql

@@ -111,6 +111,11 @@ EXPLAIN (COSTS OFF)
 SELECT t1.x, sum(t1.y), count(*) FROM pagg_tab1 t1, pagg_tab2 t2 WHERE t1.x = t2.y GROUP BY t1.x ORDER BY 1, 2, 3;
 SELECT t1.x, sum(t1.y), count(*) FROM pagg_tab1 t1, pagg_tab2 t2 WHERE t1.x = t2.y GROUP BY t1.x ORDER BY 1, 2, 3;
 
+-- Check with whole-row reference; partitionwise aggregation does not apply
+EXPLAIN (COSTS OFF)
+SELECT t1.x, sum(t1.y), count(t1) FROM pagg_tab1 t1, pagg_tab2 t2 WHERE t1.x = t2.y GROUP BY t1.x ORDER BY 1, 2, 3;
+SELECT t1.x, sum(t1.y), count(t1) FROM pagg_tab1 t1, pagg_tab2 t2 WHERE t1.x = t2.y GROUP BY t1.x ORDER BY 1, 2, 3;
+
 -- GROUP BY having other matching key
 EXPLAIN (COSTS OFF)
 SELECT t2.y, sum(t1.y), count(*) FROM pagg_tab1 t1, pagg_tab2 t2 WHERE t1.x = t2.y GROUP BY t2.y ORDER BY 1, 2, 3;

src/test/regress/sql/partition_join.sql

@@ -34,7 +34,7 @@ EXPLAIN (COSTS OFF)
 SELECT t1.a, t1.c, t2.b, t2.c FROM prt1 t1, prt2 t2 WHERE t1.a = t2.b AND t1.b = 0 ORDER BY t1.a, t2.b;
 SELECT t1.a, t1.c, t2.b, t2.c FROM prt1 t1, prt2 t2 WHERE t1.a = t2.b AND t1.b = 0 ORDER BY t1.a, t2.b;
 
--- left outer join, with whole-row reference
+-- left outer join, with whole-row reference; partitionwise join does not apply
 EXPLAIN (COSTS OFF)
 SELECT t1, t2 FROM prt1 t1 LEFT JOIN prt2 t2 ON t1.a = t2.b WHERE t1.b = 0 ORDER BY t1.a, t2.b;
 SELECT t1, t2 FROM prt1 t1 LEFT JOIN prt2 t2 ON t1.a = t2.b WHERE t1.b = 0 ORDER BY t1.a, t2.b;
@@ -160,6 +160,12 @@ EXPLAIN (COSTS OFF)
 SELECT t1.a, t2.b FROM (SELECT * FROM prt1 WHERE a < 450) t1 LEFT JOIN (SELECT * FROM prt2 WHERE b > 250) t2 ON t1.a = t2.b WHERE t1.b = 0 ORDER BY t1.a, t2.b;
 SELECT t1.a, t2.b FROM (SELECT * FROM prt1 WHERE a < 450) t1 LEFT JOIN (SELECT * FROM prt2 WHERE b > 250) t2 ON t1.a = t2.b WHERE t1.b = 0 ORDER BY t1.a, t2.b;
 
+-- merge join when expression with whole-row reference needs to be sorted;
+-- partitionwise join does not apply
+EXPLAIN (COSTS OFF)
+SELECT t1.a, t2.b FROM prt1 t1, prt2 t2 WHERE t1::text = t2::text AND t1.a = t2.b ORDER BY t1.a;
+SELECT t1.a, t2.b FROM prt1 t1, prt2 t2 WHERE t1::text = t2::text AND t1.a = t2.b ORDER BY t1.a;
+
 RESET enable_hashjoin;
 RESET enable_nestloop;