Can you have a look at dump with parallel option. Parallel option will take a lock on table while invoking lockTableForWorker. May be this is not required for foreign tables. Thoughts?
I tried with -j and found no issue. I guess that the foreign table needs locking anyway to prevent anyone to modify it while is being dumped.
I'm able to get the problem with the following steps:
Bring up a postgres setup with servers running in 5432 & 5433 port.
Execute the following commands in Server1 configured on 5432 port:
CREATE EXTENSION postgres_fdw;
CREATE SERVER foreign_server FOREIGN DATA WRAPPER postgres_fdw OPTIONS (host '127.0.0.1', port '5433', dbname 'postgres');
create user user1 password '123';
alter user user1 with superuser;
CREATE USER MAPPING FOR user1 SERVER foreign_server OPTIONS (user 'user1', password '123');
Execute the following commands in Server2 configured on 5433 port:
create user user1 password '123';
alter user user1 with superuser;
Execute the following commands in Server2 configured on 5433 port as user1 user:
create schema test;
create table test.test1(id int);
insert into test.test1 values(10);
Execute the following commands in Server1 configured on 5432 port as user1 user:
CREATE FOREIGN TABLE foreign_table1 (id integer NOT NULL) SERVER foreign_server OPTIONS (schema_name 'test', table_name 'test1');
Without parallel option, the operation is successful:
pg_dump: error: could not obtain lock on relation "public.foreign_table1" This usually means that someone requested an ACCESS EXCLUSIVE lock on the table after the pg_dump parent process had gotten the initial ACCESS SHARE lock on the table. pg_dump: error: a worker process died unexpectedly
There may be simpler steps than this to reproduce the issue, i have not try to optimize it.
