gistfile1.txt

tasks=# BEGIN;
BEGIN

tasks=# SELECT * FROM tasks WHERE status = 'pending' ORDER BY created_at ASC LIMIT 1 FOR UPDATE SKIP LOCKED;
 id | status  |                              payload                              |         created_at         
----+---------+-------------------------------------------------------------------+----------------------------
 1  | pending | { "action": "feed", "animal": "panda", "food": "kaiserschmarrn" } | 2019-09-19 15:39:49.459537
(1 row)

tasks=# SAVEPOINT task_1;
SAVEPOINT

tasks=# INSERT INTO projects (name)  VALUES ('foobar');
ERROR:  null value in column "namespace_id" violates not-null constraint
DETAIL:  Failing row contains (20, foobar, null).

tasks=# ROLLBACK TO SAVEPOINT task_1;
ROLLBACK

tasks=# UPDATE tasks SET status = 'failed' WHERE id='1';
UPDATE 1

tasks=# COMMIT;
COMMIT

tasks=# SELECT * FROM tasks;
 id | status |                              payload                              |         created_at         
----+--------+-------------------------------------------------------------------+----------------------------
 1  | failed | { "action": "feed", "animal": "panda", "food": "kaiserschmarrn" } | 2019-09-19 15:39:49.459537
(1 row)