-- Function to generate a long string
CREATE OR REPLACE FUNCTION string_long(length integer) RETURNS text AS 
$$
DECLARE
  result text := '';
  i integer := 0;
BEGIN
  if length < 0 then
    raise exception 'Given length cannot be less than 0';
  end if;
  for i in 1..length loop
    result := result || 'X';
  end loop;
  return result;
END;
$$ LANGUAGE plpgsql IMMUTABLE;

-- Some data
CREATE TABLE aa (a int, b text);
ALTER TABLE aa ALTER COLUMN b SET STORAGE EXTERNAL;
INSERT INTO aa values (generate_series(1, 100000), string_long(4000));
SELECT * FROM aa WHERE a = 14000;

-- DROP TABLE aa;