sql: Add mx_update_job2 trigger

This commit removes the -> `CANCELLED` housekeeping from the
`mx_update_job` trigger as we no longer set the state to `CANCELLED` by
code.

Instead, a new trigger is added, which transitions a job from `INQ` to
`CANCELLED` when the `job_cancelled` flag is set.

For jobs that are `RUNNING`, the `job_cancelled` flag needs to be
handled by the daemon, which kills the job. Note that the job will
transition into `KILLED` not into `CANCELLED`.

This approach eliminates the need for any code for jobs getting killed
in the `LOADED` or `ASSIGNED` states, as these will either transition
into `RUNNING` or - in very exceptional cases - back into INQ.

mysql/create_trigger.sql

@@ -87,17 +87,6 @@ CREATE TRIGGER mxq_update_job BEFORE UPDATE ON mxq_job
                     stats_total_real_sec  = stats_total_real_sec  + NEW.stats_real_sec
                 WHERE group_id = NEW.group_id;
 
-            -- INQ(0) | ASSIGNED(100) | CANCELLING(989) -> CANCELLED(990)
-            ELSEIF NEW.job_status = 990 AND OLD.job_status IN (0, 100, 989) THEN
-
-                SET NEW.date_start = NOW();
-                SET NEW.date_end   = NEW.date_start;
-
-                UPDATE mxq_group SET
-                    group_jobs_inq       = group_jobs_inq       - 1,
-                    group_jobs_cancelled = group_jobs_cancelled + 1
-                WHERE group_id = NEW.group_id;
-
             -- LOADED(150) | RUNNING(200)  -> UNKNOWN(999)
             ELSEIF NEW.job_status = 999 AND OLD.job_status IN (150, 200) THEN
 
@@ -162,5 +151,17 @@ CREATE TRIGGER mxq_update_job BEFORE UPDATE ON mxq_job
         END IF;
     END;
 |
+
+DROP TRIGGER IF EXISTS mxq_update_job2|
+CREATE TRIGGER mxq_update_job2 BEFORE UPDATE ON mxq_job
+    FOR EACH ROW FOLLOWS mxq_update_job
+        IF NEW.job_status = 0 AND NEW.job_cancelled THEN
+            SET NEW.job_status = 990;                     -- CANCELLED
+            UPDATE mxq_group SET
+                group_jobs_inq = group_jobs_inq - 1,
+                group_jobs_cancelled = group_jobs_cancelled + 1
+                WHERE group_id = NEW.group_id;
+        END IF;
+|
 DELIMITER ;
 UNLOCK TABLES;