CREATE EXTENSION lo;

CREATE TABLE image (title text, raster lo);

CREATE TRIGGER t_raster BEFORE UPDATE OR DELETE ON image

FOR EACH ROW EXECUTE PROCEDURE lo_manage(raster);

SELECT lo_create(43213);

lo_create

-----------

43213

(1 row)

SELECT lo_create(43214);

lo_create

-----------

43214

(1 row)

INSERT INTO image (title, raster) VALUES ('beautiful image', 43213);

SELECT lo_get(43213);

lo_get

--------

\x

(1 row)

SELECT lo_get(43214);

lo_get

--------

\x

(1 row)

UPDATE image SET raster = 43214 WHERE title = 'beautiful image';

SELECT lo_get(43213);

ERROR: large object 43213 does not exist

SELECT lo_get(43214);

lo_get

--------

\x

(1 row)

DELETE FROM image;

SELECT lo_get(43214);

ERROR: large object 43214 does not exist

DROP TABLE image;