Re: locking error

[KimSeong Loh]

Maybe you need a separate lock for the 2nd use of the table in UNION, try an alias locking

LOCK TABLES am_queue READ, am_queue AS am_queue2 READ, am_group READ, am_site READ;

(
SELECT ...
FROM am_queue
...
)
UNION (

SELECT ...
FROM am_queue AS am_queue2
...
)
...
UNLOCK TABLES;