func_gconcat.result, func_gconcat.test:

  Added a test case for bug #12095.
sql_class.h:
  Fixed bug #12095: a join query with GROUP_CONCAT over a single row table.
  Added a flag to the TMP_TABLE_PARAM class forcing to put constant
  items generated after elimination of a single row table into temp table
  in some cases (e.g. when GROUP_CONCAT is calculated over a single row
  table).
  bk ci sql/item_sum.cc
  Fixed bug #12095: a join query with GROUP_CONCAT over a single row table.
  If GROUP_CONCAT is calculated we always put its argument into a temp
  table, even when the argument is a constant item.
sql_select.cc:
  Fixed bug #12095: a join query with GROUP_CONCAT over one row table.
  If temp table is used to calculate GROUP_CONCAT the argument should
  be always put into this table, even when it is a constant item.

1 files changed, 33 insertions, 0 deletions

diff --git a/mysql-test/t/func_gconcat.test b/mysql-test/t/func_gconcat.test
index e93ffcb17b3..9793d0d0a2c 100644
--- a/mysql-test/t/func_gconcat.test
+++ b/mysql-test/t/func_gconcat.test
@@ -310,4 +310,37 @@ select a, group_concat(b order by b) from t1 group by a with rollup;
 select a, group_concat(distinct b order by b) from t1 group by a with rollup;
 drop table t1;
 
+#
+# Bug #12095: GROUP_CONCAT for one row table 
+#
+
+CREATE TABLE t1 (
+  aID smallint(5) unsigned NOT NULL auto_increment,
+  sometitle varchar(255) NOT NULL default '',
+  bID smallint(5) unsigned NOT NULL,
+  PRIMARY KEY  (aID),
+  UNIQUE KEY sometitle (sometitle)
+);
+INSERT INTO t1 SET sometitle = 'title1', bID = 1;
+INSERT INTO t1 SET sometitle = 'title2', bID = 1;
+
+CREATE TABLE t2 (
+  bID smallint(5) unsigned NOT NULL auto_increment,
+  somename varchar(255) NOT NULL default '',
+  PRIMARY KEY  (bID),
+  UNIQUE KEY somename (somename)
+);
+INSERT INTO t2 SET somename = 'test';
+
+SELECT COUNT(*), GROUP_CONCAT(DISTINCT t2.somename SEPARATOR ' |')
+  FROM t1 JOIN t2 ON t1.bID = t2.bID;
+INSERT INTO t2 SET somename = 'test2';
+SELECT COUNT(*), GROUP_CONCAT(DISTINCT t2.somename SEPARATOR ' |')
+  FROM t1 JOIN t2 ON t1.bID = t2.bID;
+DELETE FROM t2 WHERE somename = 'test2';
+SELECT COUNT(*), GROUP_CONCAT(DISTINCT t2.somename SEPARATOR ' |')
+  FROM t1 JOIN t2 ON t1.bID = t2.bID;
+
+DROP TABLE t1,t2;
+
 # End of 4.1 tests