I have a patch for postgresql-snapshot(1999-10-22).

This patch fix a TODO list item.
* require SELECT DISTINCT target list to have all ORDER BY columns

example
ogawa=> select distinct x from t1 order by y;
ERROR:  ORDER BY columns must appear in SELECT DISTINCT target list

---
Atsushi Ogawa

diff --git a/src/backend/parser/parse_clause.c b/src/backend/parser/parse_clause.c
index 81f3f88669d68c06306f61bc83d5e91a7c4cd251..a0e2bab371e34d9239f76beda82147bea51f63f1 100644 (file)
--- a/src/backend/parser/parse_clause.c
+++ b/src/backend/parser/parse_clause.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *   $Header: /cvsroot/pgsql/src/backend/parser/parse_clause.c,v 1.46 1999/10/07 04:23:12 tgl Exp $
+ *   $Header: /cvsroot/pgsql/src/backend/parser/parse_clause.c,v 1.47 1999/10/22 11:51:35 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -31,7 +31,8 @@
 static char *clauseText[] = {"ORDER", "GROUP"};
 
 static TargetEntry *findTargetlistEntry(ParseState *pstate, Node *node,
-                                       List *tlist, int clause);
+                                       List *tlist, int clause,
+                                       char *uniqFlag);
 static void parseFromClause(ParseState *pstate, List *frmList, Node **qual);
 static char    *transformTableEntry(ParseState *pstate, RangeVar *r);
 static List *addTargetToSortList(TargetEntry *tle, List *sortlist,
@@ -363,7 +364,8 @@ parseFromClause(ParseState *pstate, List *frmList, Node **qual)
  * clause  identifies clause type for error messages.
  */
 static TargetEntry *
-findTargetlistEntry(ParseState *pstate, Node *node, List *tlist, int clause)
+findTargetlistEntry(ParseState *pstate, Node *node, List *tlist, int clause,
+                   char *uniqueFlag)
 {
    TargetEntry *target_result = NULL;
    List       *tl;
@@ -462,6 +464,10 @@ findTargetlistEntry(ParseState *pstate, Node *node, List *tlist, int clause)
     * the end of the target list.   This target is set to be  resjunk =
     * TRUE so that it will not be projected into the final tuple.
     */
+   if(clause == ORDER_CLAUSE && uniqueFlag) {
+       elog(ERROR, "ORDER BY columns must appear in SELECT DISTINCT target list");
+   }
+
    target_result = transformTargetEntry(pstate, node, expr, NULL, true);
    lappend(tlist, target_result);
 
@@ -485,7 +491,7 @@ transformGroupClause(ParseState *pstate, List *grouplist, List *targetlist)
        TargetEntry *tle;
 
        tle = findTargetlistEntry(pstate, lfirst(gl),
-                                 targetlist, GROUP_CLAUSE);
+                                 targetlist, GROUP_CLAUSE, NULL);
 
        /* avoid making duplicate grouplist entries */
        if (! exprIsInSortList(tle->expr, glist, targetlist))
@@ -527,7 +533,7 @@ transformSortClause(ParseState *pstate,
        TargetEntry    *tle;
 
        tle = findTargetlistEntry(pstate, sortby->node,
-                                 targetlist, ORDER_CLAUSE);
+                                 targetlist, ORDER_CLAUSE, uniqueFlag);
 
        sortlist = addTargetToSortList(tle, sortlist, targetlist,
                                       sortby->useOp);