Patch for Bug#13805127: Stored program cache produces wrong result in same THD.

Background:

  - as described in MySQL Internals Prepared Stored
    (http://forge.mysql.com/wiki/MySQL_Internals_Prepared_Stored),
    the Optimizer sometimes does destructive changes to the parsed
    LEX-object (Item-tree), which makes it impossible to re-use
    that tree for PS/SP re-execution.

  - in order to be able to re-use the Item-tree, the destructive
    changes are remembered and rolled back after the statement execution.

The problem, discovered by this bug, was that the objects representing
GROUP-BY clause did not restored after query execution. So, the GROUP-BY
part of the statement could not be properly re-initialized for re-execution
after destructive changes.

Those objects do not take part in the Item-tree, so they can not be saved
using the approach for Item-tree.

The fix is as follows:

  - introduce a new array in st_select_lex to store the original
    ORDER pointers, representing the GROUP-BY clause;

  - Initialize this array in fix_prepare_information().

  - restore the list of GROUP-BY items in reinit_stmt_before_use().

1 files changed, 88 insertions, 0 deletions

diff --git a/mysql-test/t/ps.test b/mysql-test/t/ps.test
index 7fff7472caf..ffedf8016f8 100644
--- a/mysql-test/t/ps.test
+++ b/mysql-test/t/ps.test
@@ -3364,6 +3364,94 @@ disconnect con1;
 SELECT *
 FROM (SELECT 1 UNION SELECT 2) t;
 
+--echo
+--echo # Bug#13805127: Stored program cache produces wrong result in same THD
+--echo
+
+PREPARE s1 FROM 
+"
+SELECT c1, t2.c2, count(c3)
+FROM
+  (
+  SELECT 3 as c2 FROM dual WHERE @x = 1
+  UNION
+  SELECT 2       FROM dual WHERE @x = 1 OR @x = 2
+  ) AS t1,
+  (
+  SELECT '2012-03-01 01:00:00' AS c1, 3 as c2, 1 as c3 FROM dual
+  UNION
+  SELECT '2012-03-01 02:00:00',       3,       2       FROM dual
+  UNION
+  SELECT '2012-03-01 01:00:00',       2,       1       FROM dual
+  ) AS t2
+WHERE t2.c2 = t1.c2
+GROUP BY c1, c2
+";
+
+--echo
+SET @x = 1;
+SELECT c1, t2.c2, count(c3)
+FROM
+  (
+  SELECT 3 as c2 FROM dual WHERE @x = 1
+  UNION
+  SELECT 2       FROM dual WHERE @x = 1 OR @x = 2
+  ) AS t1,
+  (
+  SELECT '2012-03-01 01:00:00' AS c1, 3 as c2, 1 as c3 FROM dual
+  UNION
+  SELECT '2012-03-01 02:00:00',       3,       2       FROM dual
+  UNION
+  SELECT '2012-03-01 01:00:00',       2,       1       FROM dual
+  ) AS t2
+WHERE t2.c2 = t1.c2
+GROUP BY c1, c2;
+--echo
+EXECUTE s1;
+
+--echo
+SET @x = 2;
+SELECT c1, t2.c2, count(c3)
+FROM
+  (
+  SELECT 3 as c2 FROM dual WHERE @x = 1
+  UNION
+  SELECT 2       FROM dual WHERE @x = 1 OR @x = 2
+  ) AS t1,
+  (
+  SELECT '2012-03-01 01:00:00' AS c1, 3 as c2, 1 as c3 FROM dual
+  UNION
+  SELECT '2012-03-01 02:00:00',       3,       2       FROM dual
+  UNION
+  SELECT '2012-03-01 01:00:00',       2,       1       FROM dual
+  ) AS t2
+WHERE t2.c2 = t1.c2
+GROUP BY c1, c2;
+--echo
+EXECUTE s1;
+
+--echo
+SET @x = 1;
+SELECT c1, t2.c2, count(c3)
+FROM
+  (
+  SELECT 3 as c2 FROM dual WHERE @x = 1
+  UNION
+  SELECT 2       FROM dual WHERE @x = 1 OR @x = 2
+  ) AS t1,
+  (
+  SELECT '2012-03-01 01:00:00' AS c1, 3 as c2, 1 as c3 FROM dual
+  UNION
+  SELECT '2012-03-01 02:00:00',       3,       2       FROM dual
+  UNION
+  SELECT '2012-03-01 01:00:00',       2,       1       FROM dual
+  ) AS t2
+WHERE t2.c2 = t1.c2
+GROUP BY c1, c2;
+--echo
+EXECUTE s1;
+
+DEALLOCATE PREPARE s1;
 
 --echo #
 --echo # End of 5.5 tests.