CREATE EXTENSION postgres_fdw;
DO $d$
    BEGIN
        EXECUTE $$CREATE SERVER loopback FOREIGN DATA WRAPPER postgres_fdw
            OPTIONS (dbname '$$||current_database()||$$',
                     port '$$||current_setting('port')||$$'
            )$$;
    END;
$d$;

CREATE SERVER loopback FOREIGN DATA WRAPPER postgres_fdw OPTIONS (port '5432', dbname 'postgres');

CREATE USER MAPPING FOR CURRENT_USER SERVER loopback;

CREATE TABLE format_fdw_parent (c1 int) PARTITION BY RANGE (c1);
CREATE TABLE local_fdw_0_10 PARTITION OF format_fdw_parent FOR VALUES FROM (0) TO (10);
CREATE TABLE foreign_fdw_10_20_remote (c1 int);
create foreign table foreign_fdw_10_20 partition of format_fdw_parent
  FOR VALUES FROM (10) TO (20)
  server loopback options (table_name 'foreign_fdw_10_20_remote');

explain select * from format_fdw_parent;
explain (analyze true, format json) select * from format_fdw_parent;