Commit aff8dbe1 authored by evgen@moonbone.local's avatar evgen@moonbone.local
Browse files

Fix bug #13855 select distinct with group by caused server crash 

DISTINCT wasn't optimized away and caused creation of tmp table in wrong
case. This result in integer overrun and running out of memory.

Fix backported from 4.1. Now if optimizer founds that in result be only 1
row it removes distinct.
parent 0f9a3c1c

mysql-test/r/select.result

+8 −0
Original line number Diff line number Diff line
@@ -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

+9 −0
Original line number Diff line number Diff line
@@ -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

+1 −0
Original line number Diff line number Diff line
@@ -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);