BUG#21354: (COUNT(*) = 1) not working in SELECT inside prepared

           statement.

The problem was that during statement re-execution if the result was
empty the old result could be returned for group functions.

The solution is to implement proper cleanup() method in group
functions.


mysql-test/r/ps.result:
  Add result for bug#21354: (COUNT(*) = 1) not working in SELECT inside
  prepared statement.
mysql-test/t/func_gconcat.test:
  Add a comment that the test case is from bug#836.
mysql-test/t/ps.test:
  Add test case for bug#21354: (COUNT(*) = 1) not working in SELECT inside
  prepared statement.
sql/item_sum.cc:
  Call clear() in Item_sum_count::cleanup().
sql/item_sum.h:
  Add comments.
  Add proper cleanup() methods.
  Change Item_sum::no_rows_in_result() to call clear() instead of reset(),
  as the latter also issues add(), and there is nothing to add when there
  are no rows in result.

1 files changed, 1 insertions, 1 deletions

diff --git a/mysql-test/t/func_gconcat.test b/mysql-test/t/func_gconcat.test
index 8f50690dd8b..21ec7362877 100644
--- a/mysql-test/t/func_gconcat.test
+++ b/mysql-test/t/func_gconcat.test
@@ -99,7 +99,7 @@ select ifnull(group_concat(concat(t1.id, ':', t1.name)), 'shortname') as 'withou
 select distinct ifnull(group_concat(concat(t1.id, ':', t1.name)), 'shortname') as 'with distinct: cutoff at length of shortname' from t1;
 drop table t1;
 
-# check zero rows
+# check zero rows (bug#836)
 create table t1(id int);
 create table t2(id int);
 insert into t1 values(0),(1);