1 files changed, 51 insertions, 9 deletions

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 7ff36bc8422..8b1bad0d794 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -509,7 +509,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <ival>	sub_type opt_materialized
 %type <value>	NumericOnly
 %type <list>	NumericOnly_list
-%type <alias>	alias_clause opt_alias_clause
+%type <alias>	alias_clause opt_alias_clause opt_alias_clause_for_join_using
 %type <list>	func_alias_clause
 %type <sortby>	sortby
 %type <ielem>	index_elem index_elem_options
@@ -12144,6 +12144,7 @@ joined_table:
 					n->larg = $1;
 					n->rarg = $4;
 					n->usingClause = NIL;
+					n->join_using_alias = NULL;
 					n->quals = NULL;
 					$$ = n;
 				}
@@ -12155,9 +12156,16 @@ joined_table:
 					n->larg = $1;
 					n->rarg = $4;
 					if ($5 != NULL && IsA($5, List))
-						n->usingClause = (List *) $5; /* USING clause */
+					{
+						 /* USING clause */
+						n->usingClause = linitial_node(List, castNode(List, $5));
+						n->join_using_alias = lsecond_node(Alias, castNode(List, $5));
+					}
 					else
-						n->quals = $5; /* ON clause */
+					{
+						/* ON clause */
+						n->quals = $5;
+					}
 					$$ = n;
 				}
 			| table_ref JOIN table_ref join_qual
@@ -12169,9 +12177,16 @@ joined_table:
 					n->larg = $1;
 					n->rarg = $3;
 					if ($4 != NULL && IsA($4, List))
-						n->usingClause = (List *) $4; /* USING clause */
+					{
+						/* USING clause */
+						n->usingClause = linitial_node(List, castNode(List, $4));
+						n->join_using_alias = lsecond_node(Alias, castNode(List, $4));
+					}
 					else
-						n->quals = $4; /* ON clause */
+					{
+						/* ON clause */
+						n->quals = $4;
+					}
 					$$ = n;
 				}
 			| table_ref NATURAL join_type JOIN table_ref
@@ -12182,6 +12197,7 @@ joined_table:
 					n->larg = $1;
 					n->rarg = $5;
 					n->usingClause = NIL; /* figure out which columns later... */
+					n->join_using_alias = NULL;
 					n->quals = NULL; /* fill later */
 					$$ = n;
 				}
@@ -12194,6 +12210,7 @@ joined_table:
 					n->larg = $1;
 					n->rarg = $4;
 					n->usingClause = NIL; /* figure out which columns later... */
+					n->join_using_alias = NULL;
 					n->quals = NULL; /* fill later */
 					$$ = n;
 				}
@@ -12229,6 +12246,22 @@ opt_alias_clause: alias_clause						{ $$ = $1; }
 		;
 
 /*
+ * The alias clause after JOIN ... USING only accepts the AS ColId spelling,
+ * per SQL standard.  (The grammar could parse the other variants, but they
+ * don't seem to be useful, and it might lead to parser problems in the
+ * future.)
+ */
+opt_alias_clause_for_join_using:
+			AS ColId
+				{
+					$$ = makeNode(Alias);
+					$$->aliasname = $2;
+					/* the column name list will be inserted later */
+				}
+			| /*EMPTY*/								{ $$ = NULL; }
+		;
+
+/*
  * func_alias_clause can include both an Alias and a coldeflist, so we make it
  * return a 2-element list that gets disassembled by calling production.
  */
@@ -12272,15 +12305,24 @@ opt_outer: OUTER_P
 
 /* JOIN qualification clauses
  * Possibilities are:
- *	USING ( column list ) allows only unqualified column names,
+ *	USING ( column list ) [ AS alias ]
+ *						  allows only unqualified column names,
  *						  which must match between tables.
  *	ON expr allows more general qualifications.
  *
- * We return USING as a List node, while an ON-expr will not be a List.
+ * We return USING as a two-element List (the first item being a sub-List
+ * of the common column names, and the second either an Alias item or NULL).
+ * An ON-expr will not be a List, so it can be told apart that way.
  */
 
-join_qual:	USING '(' name_list ')'					{ $$ = (Node *) $3; }
-			| ON a_expr								{ $$ = $2; }
+join_qual: USING '(' name_list ')' opt_alias_clause_for_join_using
+				{
+					$$ = (Node *) list_make2($3, $5);
+				}
+			| ON a_expr
+				{
+					$$ = $2;
+				}
 		;