Fix creation of resjunk tlist entries for inherited mixed UPDATE/DELETE.

rewriteTargetListUD's processing is dependent on the relkind of the query's
target table.  That was fine at the time it was made to act that way, even
for queries on inheritance trees, because all tables in an inheritance tree
would necessarily be plain tables.  However, the 9.5 feature addition
allowing some members of an inheritance tree to be foreign tables broke the
assumption that rewriteTargetListUD's output tlist could be applied to all
child tables with nothing more than column-number mapping.  This led to
visible failures if foreign child tables had row-level triggers, and would
also break in cases where child tables belonged to FDWs that used methods
other than CTID for row identification.

To fix, delay running rewriteTargetListUD until after the planner has
expanded inheritance, so that it is applied separately to the (already
mapped) tlist for each child table.  We can conveniently call it from
preprocess_targetlist.  Refactor associated code slightly to avoid the
need to heap_open the target relation multiple times during
preprocess_targetlist.  (The APIs remain a bit ugly, particularly around
the point of which steps scribble on parse->targetList and which don't.
But avoiding such scribbling would require a change in FDW callback APIs,
which is more pain than it's worth.)

Also fix ExecModifyTable to ensure that "tupleid" is reset to NULL when
we transition from rows providing a CTID to rows that don't.  (That's
really an independent bug, but it manifests in much the same cases.)

Add a regression test checking one manifestation of this problem, which
was that row-level triggers on a foreign child table did not work right.

Back-patch to 9.5 where the problem was introduced.

Etsuro Fujita, reviewed by Ildus Kurbangaliev and Ashutosh Bapat

Discussion: https://postgr.es/m/20170514150525.0346ba72@postgrespro.ru

contrib/postgres_fdw/expected/postgres_fdw.out

@@ -7022,6 +7022,63 @@ update bar set f2 = f2 + 100 returning *;
   7 | 277
 (6 rows)
 
+-- Test that UPDATE/DELETE with inherited target works with row-level triggers
+CREATE TRIGGER trig_row_before
+BEFORE UPDATE OR DELETE ON bar2
+FOR EACH ROW EXECUTE PROCEDURE trigger_data(23,'skidoo');
+CREATE TRIGGER trig_row_after
+AFTER UPDATE OR DELETE ON bar2
+FOR EACH ROW EXECUTE PROCEDURE trigger_data(23,'skidoo');
+explain (verbose, costs off)
+update bar set f2 = f2 + 100;
+                                      QUERY PLAN                                      
+--------------------------------------------------------------------------------------
+ Update on public.bar
+   Update on public.bar
+   Foreign Update on public.bar2
+     Remote SQL: UPDATE public.loct2 SET f2 = $2 WHERE ctid = $1 RETURNING f1, f2, f3
+   ->  Seq Scan on public.bar
+         Output: bar.f1, (bar.f2 + 100), bar.ctid
+   ->  Foreign Scan on public.bar2
+         Output: bar2.f1, (bar2.f2 + 100), bar2.f3, bar2.ctid, bar2.*
+         Remote SQL: SELECT f1, f2, f3, ctid FROM public.loct2 FOR UPDATE
+(9 rows)
+
+update bar set f2 = f2 + 100;
+NOTICE:  trig_row_before(23, skidoo) BEFORE ROW UPDATE ON bar2
+NOTICE:  OLD: (3,333,33),NEW: (3,433,33)
+NOTICE:  trig_row_before(23, skidoo) BEFORE ROW UPDATE ON bar2
+NOTICE:  OLD: (4,344,44),NEW: (4,444,44)
+NOTICE:  trig_row_before(23, skidoo) BEFORE ROW UPDATE ON bar2
+NOTICE:  OLD: (7,277,77),NEW: (7,377,77)
+NOTICE:  trig_row_after(23, skidoo) AFTER ROW UPDATE ON bar2
+NOTICE:  OLD: (3,333,33),NEW: (3,433,33)
+NOTICE:  trig_row_after(23, skidoo) AFTER ROW UPDATE ON bar2
+NOTICE:  OLD: (4,344,44),NEW: (4,444,44)
+NOTICE:  trig_row_after(23, skidoo) AFTER ROW UPDATE ON bar2
+NOTICE:  OLD: (7,277,77),NEW: (7,377,77)
+explain (verbose, costs off)
+delete from bar where f2 < 400;
+                                         QUERY PLAN                                          
+---------------------------------------------------------------------------------------------
+ Delete on public.bar
+   Delete on public.bar
+   Foreign Delete on public.bar2
+     Remote SQL: DELETE FROM public.loct2 WHERE ctid = $1 RETURNING f1, f2, f3
+   ->  Seq Scan on public.bar
+         Output: bar.ctid
+         Filter: (bar.f2 < 400)
+   ->  Foreign Scan on public.bar2
+         Output: bar2.ctid, bar2.*
+         Remote SQL: SELECT f1, f2, f3, ctid FROM public.loct2 WHERE ((f2 < 400)) FOR UPDATE
+(10 rows)
+
+delete from bar where f2 < 400;
+NOTICE:  trig_row_before(23, skidoo) BEFORE ROW DELETE ON bar2
+NOTICE:  OLD: (7,377,77)
+NOTICE:  trig_row_after(23, skidoo) AFTER ROW DELETE ON bar2
+NOTICE:  OLD: (7,377,77)
+-- cleanup
 drop table foo cascade;
 NOTICE:  drop cascades to foreign table foo2
 drop table bar cascade;

contrib/postgres_fdw/sql/postgres_fdw.sql

@@ -1656,6 +1656,24 @@ explain (verbose, costs off)
 update bar set f2 = f2 + 100 returning *;
 update bar set f2 = f2 + 100 returning *;
 
+-- Test that UPDATE/DELETE with inherited target works with row-level triggers
+CREATE TRIGGER trig_row_before
+BEFORE UPDATE OR DELETE ON bar2
+FOR EACH ROW EXECUTE PROCEDURE trigger_data(23,'skidoo');
+
+CREATE TRIGGER trig_row_after
+AFTER UPDATE OR DELETE ON bar2
+FOR EACH ROW EXECUTE PROCEDURE trigger_data(23,'skidoo');
+
+explain (verbose, costs off)
+update bar set f2 = f2 + 100;
+update bar set f2 = f2 + 100;
+
+explain (verbose, costs off)
+delete from bar where f2 < 400;
+delete from bar where f2 < 400;
+
+-- cleanup
 drop table foo cascade;
 drop table bar cascade;
 drop table loct1;

doc/src/sgml/fdwhandler.sgml

@@ -429,11 +429,14 @@ AddForeignUpdateTargets(Query *parsetree,
      <literal>wholerow</literal>, or
      <literal>wholerow<replaceable>N</replaceable></literal>, as the core system can
      generate junk columns of these names.
+     If the extra expressions are more complex than simple Vars, they
+     must be run through <function>eval_const_expressions</function>
+     before adding them to the targetlist.
     </para>
 
     <para>
-     This function is called in the rewriter, not the planner, so the
+     Although this function is called during planning, the
-     information available is a bit different from that available to the
+     information provided is a bit different from that available to other
      planning routines.
      <literal>parsetree</literal> is the parse tree for the <command>UPDATE</command> or
      <command>DELETE</command> command, while <literal>target_rte</literal> and

doc/src/sgml/rules.sgml

@@ -167,12 +167,12 @@
 
     <para>
         <command>DELETE</command> commands don't need a normal target list
-        because they don't produce any result.  Instead, the rule system
+        because they don't produce any result.  Instead, the planner
         adds a special <acronym>CTID</acronym> entry to the empty target list,
         to allow the executor to find the row to be deleted.
         (<acronym>CTID</acronym> is added when the result relation is an ordinary
-        table.  If it is a view, a whole-row variable is added instead,
+        table.  If it is a view, a whole-row variable is added instead, by
-        as described in <xref linkend="rules-views-update"/>.)
+        the rule system, as described in <xref linkend="rules-views-update"/>.)
     </para>
 
     <para>
@@ -194,7 +194,7 @@
         column = expression</literal> part of the command.  The planner will
         handle missing columns by inserting expressions that copy the values
         from the old row into the new one.  Just as for <command>DELETE</command>,
-        the rule system adds a <acronym>CTID</acronym> or whole-row variable so that
+        a <acronym>CTID</acronym> or whole-row variable is added so that
         the executor can identify the old row to be updated.
     </para>
 

src/backend/executor/nodeModifyTable.c

@@ -1576,7 +1576,7 @@ ExecModifyTable(PlanState *pstate)
 	JunkFilter *junkfilter;
 	TupleTableSlot *slot;
 	TupleTableSlot *planSlot;
-	ItemPointer tupleid = NULL;
+	ItemPointer tupleid;
 	ItemPointerData tuple_ctid;
 	HeapTupleData oldtupdata;
 	HeapTuple	oldtuple;
@@ -1699,6 +1699,7 @@ ExecModifyTable(PlanState *pstate)
 		EvalPlanQualSetSlot(&node->mt_epqstate, planSlot);
 		slot = planSlot;
 
+		tupleid = NULL;
 		oldtuple = NULL;
 		if (junkfilter != NULL)
 		{

src/backend/optimizer/plan/planner.c

@@ -1555,7 +1555,7 @@ grouping_planner(PlannerInfo *root, bool inheritance_update,
 				 double tuple_fraction)
 {
 	Query	   *parse = root->parse;
-	List	   *tlist = parse->targetList;
+	List	   *tlist;
 	int64		offset_est = 0;
 	int64		count_est = 0;
 	double		limit_tuples = -1.0;
@@ -1685,13 +1685,7 @@ grouping_planner(PlannerInfo *root, bool inheritance_update,
 		}
 
 		/* Preprocess targetlist */
-		tlist = preprocess_targetlist(root, tlist);
+		tlist = preprocess_targetlist(root);
-
-		if (parse->onConflict)
-			parse->onConflict->onConflictSet =
-				preprocess_onconflict_targetlist(parse->onConflict->onConflictSet,
-												 parse->resultRelation,
-												 parse->rtable);
 
 		/*
 		 * We are now done hacking up the query's targetlist.  Most of the

src/backend/optimizer/prep/preptlist.c

@@ -4,20 +4,22 @@
  *	  Routines to preprocess the parse tree target list
  *
  * For INSERT and UPDATE queries, the targetlist must contain an entry for
- * each attribute of the target relation in the correct order.  For all query
+ * each attribute of the target relation in the correct order.  For UPDATE and
+ * DELETE queries, it must also contain junk tlist entries needed to allow the
+ * executor to identify the rows to be updated or deleted.  For all query
  * types, we may need to add junk tlist entries for Vars used in the RETURNING
  * list and row ID information needed for SELECT FOR UPDATE locking and/or
  * EvalPlanQual checking.
  *
- * The rewriter's rewriteTargetListIU and rewriteTargetListUD routines
+ * The query rewrite phase also does preprocessing of the targetlist (see
- * also do preprocessing of the targetlist.  The division of labor between
+ * rewriteTargetListIU).  The division of labor between here and there is
- * here and there is partially historical, but it's not entirely arbitrary.
+ * partially historical, but it's not entirely arbitrary.  In particular,
- * In particular, consider an UPDATE across an inheritance tree.  What the
+ * consider an UPDATE across an inheritance tree.  What rewriteTargetListIU
- * rewriter does need be done only once (because it depends only on the
+ * does need be done only once (because it depends only on the properties of
- * properties of the parent relation).  What's done here has to be done over
+ * the parent relation).  What's done here has to be done over again for each
- * again for each child relation, because it depends on the column list of
+ * child relation, because it depends on the properties of the child, which
- * the child, which might have more columns and/or a different column order
+ * might be of a different relation type, or have more columns and/or a
- * than the parent.
+ * different column order than the parent.
  *
  * The fact that rewriteTargetListIU sorts non-resjunk tlist entries by column
  * position, which expand_targetlist depends on, violates the above comment
@@ -47,11 +49,12 @@
 #include "optimizer/var.h"
 #include "parser/parsetree.h"
 #include "parser/parse_coerce.h"
+#include "rewrite/rewriteHandler.h"
 #include "utils/rel.h"
 
 
 static List *expand_targetlist(List *tlist, int command_type,
-				  Index result_relation, List *range_table);
+				  Index result_relation, Relation rel);
 
 
 /*
@@ -59,36 +62,61 @@ static List *expand_targetlist(List *tlist, int command_type,
  *	  Driver for preprocessing the parse tree targetlist.
  *
  *	  Returns the new targetlist.
+ *
+ * As a side effect, if there's an ON CONFLICT UPDATE clause, its targetlist
+ * is also preprocessed (and updated in-place).
  */
 List *
-preprocess_targetlist(PlannerInfo *root, List *tlist)
+preprocess_targetlist(PlannerInfo *root)
 {
 	Query	   *parse = root->parse;
 	int			result_relation = parse->resultRelation;
 	List	   *range_table = parse->rtable;
 	CmdType		command_type = parse->commandType;
+	RangeTblEntry *target_rte = NULL;
+	Relation	target_relation = NULL;
+	List	   *tlist;
 	ListCell   *lc;
 
 	/*
-	 * Sanity check: if there is a result relation, it'd better be a real
+	 * If there is a result relation, open it so we can look for missing
-	 * relation not a subquery.  Else parser or rewriter messed up.
+	 * columns and so on.  We assume that previous code already acquired at
+	 * least AccessShareLock on the relation, so we need no lock here.
 	 */
 	if (result_relation)
 	{
-		RangeTblEntry *rte = rt_fetch(result_relation, range_table);
+		target_rte = rt_fetch(result_relation, range_table);
 
-		if (rte->subquery != NULL || rte->relid == InvalidOid)
+		/*
-			elog(ERROR, "subquery cannot be result relation");
+		 * Sanity check: it'd better be a real relation not, say, a subquery.
+		 * Else parser or rewriter messed up.
+		 */
+		if (target_rte->rtekind != RTE_RELATION)
+			elog(ERROR, "result relation must be a regular relation");
+
+		target_relation = heap_open(target_rte->relid, NoLock);
 	}
+	else
+		Assert(command_type == CMD_SELECT);
+
+	/*
+	 * For UPDATE/DELETE, add any junk column(s) needed to allow the executor
+	 * to identify the rows to be updated or deleted.  Note that this step
+	 * scribbles on parse->targetList, which is not very desirable, but we
+	 * keep it that way to avoid changing APIs used by FDWs.
+	 */
+	if (command_type == CMD_UPDATE || command_type == CMD_DELETE)
+		rewriteTargetListUD(parse, target_rte, target_relation);
 
 	/*
 	 * for heap_form_tuple to work, the targetlist must match the exact order
 	 * of the attributes. We also need to fill in any missing attributes. -ay
 	 * 10/94
 	 */
+	tlist = parse->targetList;
 	if (command_type == CMD_INSERT || command_type == CMD_UPDATE)
 		tlist = expand_targetlist(tlist, command_type,
-								  result_relation, range_table);
+								  result_relation, target_relation);
 
 	/*
 	 * Add necessary junk columns for rowmarked rels.  These values are needed
@@ -193,19 +221,21 @@ preprocess_targetlist(PlannerInfo *root, List *tlist)
 		list_free(vars);
 	}
 
-	return tlist;
-}
-
 	/*
- * preprocess_onconflict_targetlist
+	 * If there's an ON CONFLICT UPDATE clause, preprocess its targetlist too
- *	  Process ON CONFLICT SET targetlist.
+	 * while we have the relation open.
- *
- *	  Returns the new targetlist.
 	 */
-List *
+	if (parse->onConflict)
-preprocess_onconflict_targetlist(List *tlist, int result_relation, List *range_table)
+		parse->onConflict->onConflictSet =
-{
+			expand_targetlist(parse->onConflict->onConflictSet,
-	return expand_targetlist(tlist, CMD_UPDATE, result_relation, range_table);
+							  CMD_UPDATE,
+							  result_relation,
+							  target_relation);
+
+	if (target_relation)
+		heap_close(target_relation, NoLock);
+
+	return tlist;
 }
 
 
@@ -223,11 +253,10 @@ preprocess_onconflict_targetlist(List *tlist, int result_relation, List *range_t
  */
 static List *
 expand_targetlist(List *tlist, int command_type,
-				  Index result_relation, List *range_table)
+				  Index result_relation, Relation rel)
 {
 	List	   *new_tlist = NIL;
 	ListCell   *tlist_item;
-	Relation	rel;
 	int			attrno,
 				numattrs;
 
@@ -238,12 +267,8 @@ expand_targetlist(List *tlist, int command_type,
 	 * order; but we have to insert TLEs for any missing attributes.
 	 *
 	 * Scan the tuple description in the relation's relcache entry to make
-	 * sure we have all the user attributes in the right order.  We assume
+	 * sure we have all the user attributes in the right order.
-	 * that the rewriter already acquired at least AccessShareLock on the
-	 * relation, so we need no lock here.
 	 */
-	rel = heap_open(getrelid(result_relation, range_table), NoLock);
-
 	numattrs = RelationGetNumberOfAttributes(rel);
 
 	for (attrno = 1; attrno <= numattrs; attrno++)
@@ -386,8 +411,6 @@ expand_targetlist(List *tlist, int command_type,
 		tlist_item = lnext(tlist_item);
 	}
 
-	heap_close(rel, NoLock);
-
 	return new_tlist;
 }
 

src/backend/rewrite/rewriteHandler.c

@@ -72,8 +72,6 @@ static TargetEntry *process_matched_tle(TargetEntry *src_tle,
 static Node *get_assignment_input(Node *node);
 static void rewriteValuesRTE(RangeTblEntry *rte, Relation target_relation,
 				 List *attrnos);
-static void rewriteTargetListUD(Query *parsetree, RangeTblEntry *target_rte,
-					Relation target_relation);
 static void markQueryForLocking(Query *qry, Node *jtnode,
 					LockClauseStrength strength, LockWaitPolicy waitPolicy,
 					bool pushedDown);
@@ -707,6 +705,13 @@ adjustJoinTreeList(Query *parsetree, bool removert, int rt_index)
  * rewritten targetlist: an integer list of the assigned-to attnums, in
  * order of the original tlist's non-junk entries.  This is needed for
  * processing VALUES RTEs.
+ *
+ * Note that for an inheritable UPDATE, this processing is only done once,
+ * using the parent relation as reference.  It must not do anything that
+ * will not be correct when transposed to the child relation(s).  (Step 4
+ * is incorrect by this light, since child relations might have different
+ * colun ordering, but the planner will fix things by re-sorting the tlist
+ * for each child.)
  */
 static List *
 rewriteTargetListIU(List *targetList,
@@ -1293,14 +1298,15 @@ rewriteValuesRTE(RangeTblEntry *rte, Relation target_relation, List *attrnos)
  * This function adds a "junk" TLE that is needed to allow the executor to
  * find the original row for the update or delete.  When the target relation
  * is a regular table, the junk TLE emits the ctid attribute of the original
- * row.  When the target relation is a view, there is no ctid, so we instead
+ * row.  When the target relation is a foreign table, we let the FDW decide
- * emit a whole-row Var that will contain the "old" values of the view row.
+ * what to add.
- * If it's a foreign table, we let the FDW decide what to add.
  *
- * For UPDATE queries, this is applied after rewriteTargetListIU.  The
+ * We used to do this during RewriteQuery(), but now that inheritance trees
- * ordering isn't actually critical at the moment.
+ * can contain a mix of regular and foreign tables, we must postpone it till
+ * planning, after the inheritance tree has been expanded.  In that way we
+ * can do the right thing for each child table.
  */
-static void
+void
 rewriteTargetListUD(Query *parsetree, RangeTblEntry *target_rte,
 					Relation target_relation)
 {
@@ -1358,19 +1364,6 @@ rewriteTargetListUD(Query *parsetree, RangeTblEntry *target_rte,
 			attrname = "wholerow";
 		}
 	}
-	else
-	{
-		/*
-		 * Emit whole-row Var so that executor will have the "old" view row to
-		 * pass to the INSTEAD OF trigger.
-		 */
-		var = makeWholeRowVar(target_rte,
-							  parsetree->resultRelation,
-							  0,
-							  false);
-
-		attrname = "wholerow";
-	}
 
 	if (var != NULL)
 	{
@@ -1497,6 +1490,8 @@ ApplyRetrieveRule(Query *parsetree,
 				 parsetree->commandType == CMD_DELETE)
 		{
 			RangeTblEntry *newrte;
+			Var		   *var;
+			TargetEntry *tle;
 
 			rte = rt_fetch(rt_index, parsetree->rtable);
 			newrte = copyObject(rte);
@@ -1527,6 +1522,20 @@ ApplyRetrieveRule(Query *parsetree,
 			ChangeVarNodes((Node *) parsetree->returningList, rt_index,
 						   parsetree->resultRelation, 0);
 
+			/*
+			 * To allow the executor to compute the original view row to pass
+			 * to the INSTEAD OF trigger, we add a resjunk whole-row Var
+			 * referencing the original RTE.  This will later get expanded
+			 * into a RowExpr computing all the OLD values of the view row.
+			 */
+			var = makeWholeRowVar(rte, rt_index, 0, false);
+			tle = makeTargetEntry((Expr *) var,
+								  list_length(parsetree->targetList) + 1,
+								  pstrdup("wholerow"),
+								  true);
+
+			parsetree->targetList = lappend(parsetree->targetList, tle);
+
 			/* Now, continue with expanding the original view RTE */
 		}
 		else
@@ -2966,26 +2975,6 @@ rewriteTargetView(Query *parsetree, Relation view)
 	new_rte->securityQuals = view_rte->securityQuals;
 	view_rte->securityQuals = NIL;
 
-	/*
-	 * For UPDATE/DELETE, rewriteTargetListUD will have added a wholerow junk
-	 * TLE for the view to the end of the targetlist, which we no longer need.
-	 * Remove it to avoid unnecessary work when we process the targetlist.
-	 * Note that when we recurse through rewriteQuery a new junk TLE will be
-	 * added to allow the executor to find the proper row in the new target
-	 * relation.  (So, if we failed to do this, we might have multiple junk
-	 * TLEs with the same name, which would be disastrous.)
-	 */
-	if (parsetree->commandType != CMD_INSERT)
-	{
-		TargetEntry *tle = (TargetEntry *) llast(parsetree->targetList);
-
-		Assert(tle->resjunk);
-		Assert(IsA(tle->expr, Var) &&
-			   ((Var *) tle->expr)->varno == parsetree->resultRelation &&
-			   ((Var *) tle->expr)->varattno == 0);
-		parsetree->targetList = list_delete_ptr(parsetree->targetList, tle);
-	}
-
 	/*
 	 * Now update all Vars in the outer query that reference the view to
 	 * reference the appropriate column of the base relation instead.
@@ -3347,11 +3336,10 @@ RewriteQuery(Query *parsetree, List *rewrite_events)
 									parsetree->override,
 									rt_entry_relation,
 									parsetree->resultRelation, NULL);
-			rewriteTargetListUD(parsetree, rt_entry, rt_entry_relation);
 		}
 		else if (event == CMD_DELETE)
 		{
-			rewriteTargetListUD(parsetree, rt_entry, rt_entry_relation);
+			/* Nothing to do here */
 		}
 		else
 			elog(ERROR, "unrecognized commandType: %d", (int) event);

src/include/optimizer/prep.h

@@ -38,10 +38,7 @@ extern Expr *canonicalize_qual(Expr *qual);
 /*
  * prototypes for preptlist.c
  */
-extern List *preprocess_targetlist(PlannerInfo *root, List *tlist);
+extern List *preprocess_targetlist(PlannerInfo *root);
-
-extern List *preprocess_onconflict_targetlist(List *tlist,
-								 int result_relation, List *range_table);
 
 extern PlanRowMark *get_plan_rowmark(List *rowmarks, Index rtindex);
 

src/include/rewrite/rewriteHandler.h

@@ -23,6 +23,9 @@ extern void AcquireRewriteLocks(Query *parsetree,
 					bool forUpdatePushedDown);
 
 extern Node *build_column_default(Relation rel, int attrno);
+extern void rewriteTargetListUD(Query *parsetree, RangeTblEntry *target_rte,
+					Relation target_relation);
+
 extern Query *get_view_query(Relation view);
 extern const char *view_query_is_auto_updatable(Query *viewquery,
 							 bool check_cols);