bzr commit into mysql-5.0-bugteam branch (Alexey.Kopytov:2842) Bug#48475

[Alexey Kopytov]

#At file:///data/src/bzr/bugteam/bug48475/my50-bug48475/ based on revid:timothy.smith@stripped

 2842 Alexey Kopytov	2009-11-06
      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
        Added a test case for bug #48475.
     @ mysql-test/t/olap.test
        Added a test case for bug #48475.
     @ sql/sql_select.cc
        Disabled const-only table optimizations for the WITH ROLLUP
        case.

    modified:
      mysql-test/r/olap.result
      mysql-test/t/olap.test
      sql/sql_select.cc
=== modified file 'mysql-test/r/olap.result'
--- a/mysql-test/r/olap.result	2009-10-30 15:54:53 +0000
+++ b/mysql-test/r/olap.result	2009-11-06 06:44:01 +0000
@@ -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

=== modified file 'mysql-test/t/olap.test'
--- a/mysql-test/t/olap.test	2009-10-30 15:54:53 +0000
+++ b/mysql-test/t/olap.test	2009-11-06 06:44:01 +0000
@@ -390,4 +390,17 @@ SELECT DISTINCT b FROM t1, t2 GROUP BY a
 
 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

=== modified file 'sql/sql_select.cc'
--- a/sql/sql_select.cc	2009-11-03 16:58:54 +0000
+++ b/sql/sql_select.cc	2009-11-06 06:44:01 +0000
@@ -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)
   {
-    DBUG_PRINT("error", ("Error: rollup_process_fields() failed"));
-    DBUG_RETURN(1);
+    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);
   }
 
-  /* 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,


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