Fix LATERAL references to target table of UPDATE/DELETE.

I failed to think much about UPDATE/DELETE when implementing LATERAL :-(.
The implemented behavior ended up being that subqueries in the FROM or
USING clause (respectively) could access the update/delete target table as
though it were a lateral reference; which seems fine if they said LATERAL,
but certainly ought to draw an error if they didn't.  Fix it so you get a
suitable error when you omit LATERAL.  Per report from Emre Hasegeli.

3 files changed, 29 insertions, 0 deletions

diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c
index a9d1fecff5c..2d8dc57d690 100644
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -342,6 +342,7 @@ static Query *
 transformDeleteStmt(ParseState *pstate, DeleteStmt *stmt)
 {
 	Query	   *qry = makeNode(Query);
+	ParseNamespaceItem *nsitem;
 	Node	   *qual;
 
 	qry->commandType = CMD_DELETE;
@@ -360,8 +361,15 @@ transformDeleteStmt(ParseState *pstate, DeleteStmt *stmt)
 										 true,
 										 ACL_DELETE);
 
+	/* grab the namespace item made by setTargetTable */
+	nsitem = (ParseNamespaceItem *) llast(pstate->p_namespace);
+
+	/* there's no DISTINCT in DELETE */
 	qry->distinctClause = NIL;
 
+	/* subqueries in USING can see the result relation only via LATERAL */
+	nsitem->p_lateral_only = true;
+
 	/*
 	 * The USING clause is non-standard SQL syntax, and is equivalent in
 	 * functionality to the FROM list that can be specified for UPDATE. The
@@ -370,6 +378,9 @@ transformDeleteStmt(ParseState *pstate, DeleteStmt *stmt)
 	 */
 	transformFromClause(pstate, stmt->usingClause);
 
+	/* remaining clauses can see the result relation normally */
+	nsitem->p_lateral_only = false;
+
 	qual = transformWhereClause(pstate, stmt->whereClause,
 								EXPR_KIND_WHERE, "WHERE");
 
@@ -1889,6 +1900,7 @@ static Query *
 transformUpdateStmt(ParseState *pstate, UpdateStmt *stmt)
 {
 	Query	   *qry = makeNode(Query);
+	ParseNamespaceItem *nsitem;
 	RangeTblEntry *target_rte;
 	Node	   *qual;
 	ListCell   *origTargetList;
@@ -1910,12 +1922,21 @@ transformUpdateStmt(ParseState *pstate, UpdateStmt *stmt)
 										 true,
 										 ACL_UPDATE);
 
+	/* grab the namespace item made by setTargetTable */
+	nsitem = (ParseNamespaceItem *) llast(pstate->p_namespace);
+
+	/* subqueries in FROM can see the result relation only via LATERAL */
+	nsitem->p_lateral_only = true;
+
 	/*
 	 * the FROM clause is non-standard SQL syntax. We used to be able to do
 	 * this with REPLACE in POSTQUEL so we keep the feature.
 	 */
 	transformFromClause(pstate, stmt->fromClause);
 
+	/* remaining clauses can see the result relation normally */
+	nsitem->p_lateral_only = false;
+
 	qry->targetList = transformTargetList(pstate, stmt->targetList,
 										  EXPR_KIND_UPDATE_SOURCE);
 
diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index a9ecc2399db..f2c506f940c 100644
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -207,6 +207,10 @@ setTargetTable(ParseState *pstate, RangeVar *relation,
 
 	/*
 	 * If UPDATE/DELETE, add table to joinlist and namespace.
+	 *
+	 * Note: some callers know that they can find the new ParseNamespaceItem
+	 * at the end of the pstate->p_namespace list.  This is a bit ugly but not
+	 * worth complicating this function's signature for.
 	 */
 	if (alsoSource)
 		addRTEtoQuery(pstate, rte, true, true, true);
diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index d473749e303..8bd3a90feaf 100644
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -1611,6 +1611,10 @@ isLockedRefname(ParseState *pstate, const char *refname)
  * and/or namespace list.  (We assume caller has checked for any
  * namespace conflicts.)  The RTE is always marked as unconditionally
  * visible, that is, not LATERAL-only.
+ *
+ * Note: some callers know that they can find the new ParseNamespaceItem
+ * at the end of the pstate->p_namespace list.  This is a bit ugly but not
+ * worth complicating this function's signature for.
  */
 void
 addRTEtoQuery(ParseState *pstate, RangeTblEntry *rte,