How can I use Postgres "ROLLBACK TO SAVEPOINT" with "FOR UPDATE SKIP LOCKED"?

[Andrew Stuart]

Postgres 10

I am trying to use "FOR UPDATE SKIP LOCKED" to make a work queue in
Postgres.

My goal is to be able to set status to 'complete' or 'failed' as the
outcome by using "ROLLBACK TO SAVEPOINT;" in the event that processing
fails.

I expected the code below  to result in a final status of "failed", but it
appears the final status is "waiting".

    BEGIN;
          DROP TABLE IF EXISTS foo;
          SELECT id
          INTO foo
          FROM jobs
          WHERE status = 'waiting'
          AND status != 'failed'
          ORDER BY created ASC
          FOR UPDATE SKIP LOCKED
          LIMIT 1;

        UPDATE jobs SET status = 'failed' WHERE id = (SELECT id from foo)
RETURNING *;
        SAVEPOINT blah;
        UPDATE jobs SET status = 'complete' WHERE id = (SELECT id from foo)
RETURNING *;


    ROLLBACK TO SAVEPOINT blah;


Can anyone please suggest what I can do to use either COMMIT to for status
to be 'complete' or ROLLBACK TO SAVEPOINT blah for statgus to be 'failed'?

thanks!