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                              { $$ = lappend($1, $3); }
  * between table_ref := '(' joined_table ')' alias_clause
  * and joined_table := '(' joined_table ')'.  So, we must have the
  * redundant-looking productions here instead.
- *
- * Note that the SQL spec does not permit a subselect (<derived_table>)
- * without an alias clause, so we don't either.  This avoids the problem
- * of needing to invent a refname for an unlabeled subselect.
  */
 table_ref:  relation_expr
                                {
@@ -3618,6 +3614,23 @@ table_ref:  relation_expr
                                        $1->name = $2;
                                        $$ = (Node *) $1;
                                }
+               | select_with_parens
+                               {
+                                       /*
+                                        * The SQL spec does not permit a subselect
+                                        * (<derived_table>) 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);