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CREATE FUNCTION concurrent_lock_check(p_dest_table text, p_lock_wait int DEFAULT NULL) RETURNS boolean
LANGUAGE plpgsql SECURITY DEFINER
AS $$
DECLARE
v_adv_lock boolean;
v_dest_table text;
v_lock_iter int;
BEGIN
SELECT dest_table INTO v_dest_table FROM @extschema@.refresh_config WHERE dest_table = p_dest_table;
IF v_dest_table IS NULL THEN
RAISE EXCEPTION 'Destination table given in argument (%) is not managed by mimeo', p_dest_table;
END IF;
v_adv_lock := pg_try_advisory_xact_lock(hashtext('mimeo advisory lock'), hashtext(v_dest_table));
IF v_adv_lock = 'false' AND p_lock_wait IS NOT NULL THEN
IF p_lock_wait > 0 THEN
-- Use the "try" advisory lock since we want to check at intervals whether it's available
v_lock_iter = 0;
WHILE (v_adv_lock = 'false') AND (v_lock_iter >= p_lock_wait) LOOP
v_lock_iter := v_lock_iter + 1;
v_adv_lock := pg_try_advisory_xact_lock(hashtext('mimeo advisory lock'), hashtext(v_dest_table));
PERFORM pg_sleep(1);
END LOOP;
ELSE
-- Since we want to wait indefinitely, can just call normal transaction advisory lock since it waits forever for true
PERFORM pg_advisory_xact_lock(hashtext('mimeo advisory lock'), hashtext(v_dest_table));
v_adv_lock := 'true';
END IF; -- END p_lock_wait > 0 check check
END IF; -- END v_adv_lock check
RETURN v_adv_lock;
END
$$;
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