olap.result, olap.test:

  Added a test case for bug #11543.
sql_select.cc:
  Fixed bug #11543.
  A ROLLUP query could return a wrong result set when
  its GROUP BY clause contained references to the same
  column.

mysql-test/r/olap.result

@@ -504,3 +504,15 @@ IFNULL(a, 'TEST')	COALESCE(b, 'TEST')
 4	TEST
 TEST	TEST
 DROP TABLE t1,t2;
+CREATE TABLE t1 (a INT(10) NOT NULL, b INT(10) NOT NULL);
+INSERT INTO t1 VALUES (1, 1);
+INSERT INTO t1 VALUES (1, 2);
+SELECT a, b, a AS c, COUNT(*) AS count FROM t1 GROUP BY a, b, c WITH ROLLUP;
+a	b	c	count
+1	1	1	1
+1	1	NULL	1
+1	2	1	1
+1	2	NULL	1
+1	NULL	NULL	2
+NULL	NULL	NULL	2
+DROP TABLE t1;

mysql-test/t/olap.test

@@ -238,3 +238,14 @@ SELECT IFNULL(a, 'TEST'), COALESCE(b, 'TEST') FROM t2
 
 DROP TABLE t1,t2;
 
+#
+# Test for bug #11543: ROLLUP query with a repeated column in GROUP BY 
+#
+
+CREATE TABLE t1 (a INT(10) NOT NULL, b INT(10) NOT NULL);
+INSERT INTO t1 VALUES (1, 1);
+INSERT INTO t1 VALUES (1, 2);
+
+SELECT a, b, a AS c, COUNT(*) AS count FROM t1 GROUP BY a, b, c WITH ROLLUP;
+
+DROP TABLE t1;

sql/sql_select.cc

@@ -9322,7 +9322,7 @@ bool JOIN::rollup_init()
     ORDER *group_tmp;
     for (group_tmp= group_list; group_tmp; group_tmp= group_tmp->next)
     {
-      if (item->eq(*group_tmp->item,0))
+      if (*group_tmp->item == item)
         item->maybe_null= 1;
     }
     if (item->type() == Item::FUNC_ITEM)
@@ -9444,7 +9444,7 @@ bool JOIN::rollup_make_fields(List<Item> &fields_arg, List<Item> &sel_fields,
 	for (group_tmp= start_group, i= pos ;
              group_tmp ; group_tmp= group_tmp->next, i++)
 	{
-          if (item->eq(*group_tmp->item,0))
+          if (*group_tmp->item == item)
 	  {
 	    /*
 	      This is an element that is used by the GROUP BY and should be