Bug #48475: DISTINCT is ignored with GROUP BY WITH ROLLUP and

            only const tables

The problem was caused by two shortcuts in the optimizer that
are inapplicable in the ROLLUP case.

Normally in a case when only const tables are involved in a
query, DISTINCT clause can be safely optimized away since there
may be only one row produced by the join. Similarly, we don't
need to create a temporary table to resolve DISTINCT/GROUP
BY/ORDER BY. Both of these are inapplicable when the WITH
ROLLUP modifier is present.

Fixed by disabling the said optimizations for the WITH ROLLUP
case.

mysql-test/r/olap.result

@@ -753,4 +753,16 @@ b
 100
 NULL
 DROP TABLE t1, t2;
+#
+# Bug #48475: DISTINCT is ignored with GROUP BY WITH ROLLUP
+#             and only const tables
+CREATE TABLE t1 (a INT);
+CREATE TABLE t2 (b INT);
+INSERT INTO t1 VALUES (1);
+INSERT INTO t2 VALUES (1);
+SELECT DISTINCT b FROM t1, t2 GROUP BY a, b WITH ROLLUP;
+b
+1
+NULL
+DROP TABLE t1, t2;
 End of 5.0 tests

mysql-test/t/olap.test

@@ -390,4 +390,17 @@ SELECT DISTINCT b FROM t1, t2 GROUP BY a, b WITH ROLLUP;
 
 DROP TABLE t1, t2;
 
+--echo #
+--echo # Bug #48475: DISTINCT is ignored with GROUP BY WITH ROLLUP
+--echo #             and only const tables
+
+CREATE TABLE t1 (a INT);
+CREATE TABLE t2 (b INT);
+INSERT INTO t1 VALUES (1);
+INSERT INTO t2 VALUES (1);
+
+SELECT DISTINCT b FROM t1, t2 GROUP BY a, b WITH ROLLUP;
+
+DROP TABLE t1, t2;
+
 --echo End of 5.0 tests

sql/sql_select.cc

@@ -929,14 +929,20 @@ JOIN::optimize()
     DBUG_RETURN(1);
   }
 
-  if (select_lex->olap == ROLLUP_TYPE && rollup_process_const_fields())
+  if (rollup.state != ROLLUP::STATE_NONE)
+  {
+    if (rollup_process_const_fields())
     {
       DBUG_PRINT("error", ("Error: rollup_process_fields() failed"));
       DBUG_RETURN(1);
     }
-
+  }
+  else
+  {
     /* Remove distinct if only const tables */
     select_distinct= select_distinct && (const_tables != tables);
+  }
+
   thd_proc_info(thd, "preparing");
   if (result->initialize_tables(this))
   {
@@ -1216,11 +1222,14 @@ JOIN::optimize()
     - We are using an ORDER BY or GROUP BY on fields not in the first table
     - We are using different ORDER BY and GROUP BY orders
     - The user wants us to buffer the result.
+    When the WITH ROLLUP modifier is present, we cannot skip temporary table
+    creation for the DISTINCT clause just because there are only const tables.
   */
-  need_tmp= (const_tables != tables &&
+  need_tmp= ((const_tables != tables &&
 	     ((select_distinct || !simple_order || !simple_group) ||
 	      (group_list && order) ||
-	      test(select_options & OPTION_BUFFER_RESULT)));
+	      test(select_options & OPTION_BUFFER_RESULT))) ||
+             rollup.state != ROLLUP::STATE_NONE && select_distinct);
 
   // No cache for MATCH
   make_join_readinfo(this,