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)

-- test updating of unrelated column
UPDATE image SET title = 'beautiful picture' WHERE title = 'beautiful image';
SELECT lo_get(43214);
 lo_get 
--------
 \x
(1 row)

DELETE FROM image;
SELECT lo_get(43214);
ERROR:  large object 43214 does not exist
-- Now let's try it with an AFTER trigger
DROP TRIGGER t_raster ON image;
CREATE CONSTRAINT TRIGGER t_raster AFTER UPDATE OR DELETE ON image
    DEFERRABLE INITIALLY DEFERRED
    FOR EACH ROW EXECUTE PROCEDURE lo_manage(raster);
SELECT lo_create(43223);
 lo_create 
-----------
     43223
(1 row)

SELECT lo_create(43224);
 lo_create 
-----------
     43224
(1 row)

SELECT lo_create(43225);
 lo_create 
-----------
     43225
(1 row)

INSERT INTO image (title, raster) VALUES ('beautiful image', 43223);
SELECT lo_get(43223);
 lo_get 
--------
 \x
(1 row)

UPDATE image SET raster = 43224 WHERE title = 'beautiful image';
SELECT lo_get(43223);  -- gone
ERROR:  large object 43223 does not exist
SELECT lo_get(43224);
 lo_get 
--------
 \x
(1 row)

-- test updating of unrelated column
UPDATE image SET title = 'beautiful picture' WHERE title = 'beautiful image';
SELECT lo_get(43224);
 lo_get 
--------
 \x
(1 row)

-- this case used to be buggy
BEGIN;
UPDATE image SET title = 'beautiful image' WHERE title = 'beautiful picture';
UPDATE image SET raster = 43225 WHERE title = 'beautiful image';
SELECT lo_get(43224);
 lo_get 
--------
 \x
(1 row)

COMMIT;
SELECT lo_get(43224);  -- gone
ERROR:  large object 43224 does not exist
SELECT lo_get(43225);
 lo_get 
--------
 \x
(1 row)

DELETE FROM image;
SELECT lo_get(43225);  -- gone
ERROR:  large object 43225 does not exist
SELECT lo_oid(1::lo);
 lo_oid 
--------
      1
(1 row)

DROP TABLE image;