Give a good error message for what's likely to be a common syntax error,

namely omitting the alias clause for a sub-SELECT in FROM.

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index c608a927d1ffc0e92bfe3df46429eb1fbc3ffc5c..36690cf1e68df47a1781fc1bc93dcbfc7d70a414 100644 (file)
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.216 2001/01/17 17:26:45 momjian Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/parser/gram.y,v 2.217 2001/01/20 17:37:52 tgl Exp $
  *
  * HISTORY
  *   AUTHOR            DATE            MAJOR EVENT
@@ -3604,10 +3604,6 @@ from_list:  from_list ',' table_ref              { $$ = lappend($1, $3); }
  * between table_ref := '(' joined_table ')' alias_clause
  * and joined_table := '(' joined_table ')'.  So, we must have the
  * redundant-looking productions here instead.
- *
- * Note that the SQL spec does not permit a subselect ()
- * without an alias clause, so we don't either.  This avoids the problem
- * of needing to invent a refname for an unlabeled subselect.
  */
 table_ref:  relation_expr
                {
@@ -3618,6 +3614,23 @@ table_ref:  relation_expr
                    $1->name = $2;
                    $$ = (Node *) $1;
                }
+       | select_with_parens
+               {
+                   /*
+                    * The SQL spec does not permit a subselect
+                    * () without an alias clause,
+                    * so we don't either.  This avoids the problem
+                    * of needing to invent a unique refname for it.
+                    * That could be surmounted if there's sufficient
+                    * popular demand, but for now let's just implement
+                    * the spec and see if anyone complains.
+                    * However, it does seem like a good idea to emit
+                    * an error message that's better than "parse error".
+                    */
+                   elog(ERROR, "sub-SELECT in FROM must have an alias"
+                        "\n\tFor example, FROM (SELECT ...) [AS] foo");
+                   $$ = NULL;
+               }
        | select_with_parens alias_clause
                {
                    RangeSubselect *n = makeNode(RangeSubselect);