Postgres_fdw join pushdown - getting server crash in left outer join of three table

Hi,

I am testing postgres_fdw join pushdown feature for PostgreSQL 9.6 DB, and
I observed below issue.

*Observation:* If do a left outer join on foreign tables more than two
times. It is causing the server crash.

Added below statement in contrib/postgres_fdw/postgres_fdw.sql and ran make
check, did a server crash

-- left outer join three tables
EXPLAIN (COSTS false, VERBOSE)
SELECT t1.c1,t2.c1,t3.c1 FROM ft2 t1 LEFT JOIN ft2 t2 ON (t1.c1 = t2.c1)
LEFT JOIN ft2 t3 ON (t2.c1 = t3.c1) OFFSET 10 LIMIT 10;
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
connection to server was lost

Facing the same crash while doing left outer join, right outer join or
combination of left-right outer joins for three tables and one local and
two foreign tables.

Thanks & Regards,
Rajkumar Raghuwanshi
QMG, EnterpriseDB Corporation