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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;
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