[HACKERS] Query got Killed with CTE.

Hi,

While quering with CTE against PG HEAD , i found that query got killed with this below error logs 

-- Machine Configuration: (d1.xlarge) CUPs : 8 , RAM  : 16GB , SIze : 640GB

postgres=# with x as (select 5 c1 from generate_series(1,1000000) x) select * from x x1 join x x2 using(c1);

Killed

2017-10-17 14:12:33.558 BST [949] LOG:  could not send data to client: Broken pipe

2017-10-17 14:12:33.558 BST [949] STATEMENT:  with x as (select 5 c1 from generate_series(1,1000000) x) select * from x x1 join x x2 using(c1);

2017-10-17 14:12:33.559 BST [949] FATAL:  connection to client lost

2017-10-17 14:12:33.559 BST [949] STATEMENT:  with x as (select 5 c1 from generate_series(1,1000000) x) select * from x x1 join x x2 using(c1);