Merge epotemkin@bk-internal.mysql.com:/home/bk/mysql-4.0

into moonbone.local:/work/13855-bug-4.0-mysql

mysql-test/r/select.result

@@ -2477,3 +2477,11 @@ a	b	c	d
 1	2	2	1
 1	2	3	1
 DROP TABLE IF EXISTS t1, t2;
+create table t1 (f1 int primary key, f2 int);
+create table t2 (f3 int, f4 int, primary key(f3,f4));
+insert into t1 values (1,1);
+insert into t2 values (1,1),(1,2);
+select distinct count(f2) >0 from t1 left join t2 on f1=f3 group by f1;
+count(f2) >0
+1
+drop table t1,t2;

mysql-test/t/select.test

@@ -2013,3 +2013,12 @@ SELECT t2.a, t2.b, IF(t1.b IS NULL,'',c) AS c, COUNT(*) AS d FROM t2,t1
 WHERE t2.a = t1.a AND t2.b = t1.b GROUP BY a, b, c;
 DROP TABLE IF EXISTS t1, t2;
 
+#
+# Bug #13855 select distinct with group by caused server crash
+#
+create table t1 (f1 int primary key, f2 int);
+create table t2 (f3 int, f4 int, primary key(f3,f4));
+insert into t1 values (1,1);
+insert into t2 values (1,1),(1,2);
+select distinct count(f2) >0 from t1 left join t2 on f1=f3 group by f1;
+drop table t1,t2;

sql/sql_select.cc

@@ -626,6 +626,7 @@ mysql_select(THD *thd,TABLE_LIST *tables,List<Item> &fields,COND *conds,
   {
     order=0;					// The output has only one row
     simple_order=1;
+    select_distinct= 0;                       // No need in distinct for 1 row
   }
 
   calc_group_buffer(&join,group);