Merge mysql.com:/home/kgeorge/mysql/5.0/B18068

into  mysql.com:/home/kgeorge/mysql/5.1/B18068

mysql-test/r/distinct.result

@@ -533,3 +533,15 @@ select count(distinct concat(x,y)) from t1;
 count(distinct concat(x,y))
 2
 drop table t1;
+CREATE TABLE t1 (a INT, b INT, PRIMARY KEY (a,b));
+INSERT INTO t1 VALUES (1, 101);
+INSERT INTO t1 SELECT a + 1, a + 101 FROM t1;
+INSERT INTO t1 SELECT a + 2, a + 102 FROM t1;
+INSERT INTO t1 SELECT a + 4, a + 104 FROM t1;
+INSERT INTO t1 SELECT a + 8, a + 108 FROM t1;
+EXPLAIN SELECT DISTINCT a,a FROM t1 WHERE b < 12 ORDER BY a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index	NULL	PRIMARY	8	NULL	16	Using where; Using index
+SELECT DISTINCT a,a FROM t1 WHERE b < 12 ORDER BY a;
+a	a
+DROP TABLE t1;

mysql-test/r/group_min_max.result

@@ -2116,3 +2116,25 @@ COUNT(DISTINCT a)
 1
 DROP TABLE t1;
 DROP PROCEDURE a;
+CREATE TABLE t1 (a varchar(64) NOT NULL default '', PRIMARY KEY(a));
+INSERT INTO t1 (a) VALUES 
+(''), ('CENTRAL'), ('EASTERN'), ('GREATER LONDON'),
+('NORTH CENTRAL'), ('NORTH EAST'), ('NORTH WEST'), ('SCOTLAND'),
+('SOUTH EAST'), ('SOUTH WEST'), ('WESTERN');
+EXPLAIN SELECT DISTINCT a,a FROM t1 ORDER BY a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	NULL	PRIMARY	66	NULL	12	Using index for group-by
+SELECT DISTINCT a,a FROM t1 ORDER BY a;
+a	a
+	
+CENTRAL	CENTRAL
+EASTERN	EASTERN
+GREATER LONDON	GREATER LONDON
+NORTH CENTRAL	NORTH CENTRAL
+NORTH EAST	NORTH EAST
+NORTH WEST	NORTH WEST
+SCOTLAND	SCOTLAND
+SOUTH EAST	SOUTH EAST
+SOUTH WEST	SOUTH WEST
+WESTERN	WESTERN
+DROP TABLE t1;

mysql-test/t/distinct.test

@@ -382,3 +382,19 @@ INSERT INTO t1 VALUES
 select count(distinct x,y) from t1;
 select count(distinct concat(x,y)) from t1;
 drop table t1;
+
+#
+# Bug #18068: SELECT DISTINCT
+#
+CREATE TABLE t1 (a INT, b INT, PRIMARY KEY (a,b));
+
+INSERT INTO t1 VALUES (1, 101);
+INSERT INTO t1 SELECT a + 1, a + 101 FROM t1;
+INSERT INTO t1 SELECT a + 2, a + 102 FROM t1;
+INSERT INTO t1 SELECT a + 4, a + 104 FROM t1;
+INSERT INTO t1 SELECT a + 8, a + 108 FROM t1;
+
+EXPLAIN SELECT DISTINCT a,a FROM t1 WHERE b < 12 ORDER BY a;
+SELECT DISTINCT a,a FROM t1 WHERE b < 12 ORDER BY a;
+
+DROP TABLE t1;

mysql-test/t/group_min_max.test

@@ -782,3 +782,19 @@ SELECT COUNT(DISTINCT a) FROM t1 WHERE a=0;
 
 DROP TABLE t1;
 DROP PROCEDURE a;
+
+#
+# Bug #18068: SELECT DISTINCT
+#
+
+CREATE TABLE t1 (a varchar(64) NOT NULL default '', PRIMARY KEY(a));
+
+INSERT INTO t1 (a) VALUES 
+  (''), ('CENTRAL'), ('EASTERN'), ('GREATER LONDON'),
+  ('NORTH CENTRAL'), ('NORTH EAST'), ('NORTH WEST'), ('SCOTLAND'),
+  ('SOUTH EAST'), ('SOUTH WEST'), ('WESTERN');
+
+EXPLAIN SELECT DISTINCT a,a FROM t1 ORDER BY a;  
+SELECT DISTINCT a,a FROM t1 ORDER BY a;  
+
+DROP TABLE t1;

sql/sql_select.cc

@@ -12803,6 +12803,17 @@ create_distinct_group(THD *thd, Item **ref_pointer_array,
   {
     if (!item->const_item() && !item->with_sum_func && !item->marker)
     {
+      /* 
+        Don't put duplicate columns from the SELECT list into the 
+        GROUP BY list.
+      */
+      ORDER *ord_iter;
+      for (ord_iter= group; ord_iter; ord_iter= ord_iter->next)
+        if ((*ord_iter->item)->eq(item, 1))
+          break;
+      if (ord_iter)
+        continue;
+      
       ORDER *ord=(ORDER*) thd->calloc(sizeof(ORDER));
       if (!ord)
 	return 0;