8.5 Workflow for the Location Tracking Server

The typical location tracking workflow involves several operations, some required and others optional.

The typical workflow contains several steps:

1. Create a tracking set.

2. Optionally, show the tracking set tables that were created.

3. Start the tracking set.

4. Optionally, show the queues used by the tracking set.

5. Optionally, show the Scheduler jobs used by the tracking set.

6. Insert polygons for various regions.

7. Create object-region pairs to be tracked.

8. Optionally, show the object-region pairs in the tracking set.

9. Send location messages.

10. Optionally, show the location messages that have been sent.

11. Dequeue the notification messages into the notifications table.

12. Optionally, disable the tracking server's object-region pairs.

13. Stop the tracking set.

14. Drop the tracking set.

The following is a simple example of the location tracking server workflow.

Example 8-1 Location Tracking Server Workflow

-- Create a tracking set named sample with one tracker/process
-- queue pair and one location queue.
EXEC sdo_trkr.create_tracking_set('sample', 1, 1);

-- Optional: Show the tracking sets tables that were created
SELECT table_name 
FROM user_tables 
WHERE table_name LIKE ‘SAMPLE%’
ORDER BY table_name;

TABLE_NAME
----------------------
SAMPLE_LOCATION_QT_1    - AQ queue table for location queue
SAMPLE_NOTIFICATIONS    - Auxiliary table to store notification messages
SAMPLE_NOTIFICATION_QT  - AQ queue table for the notification queue 	
SAMPLE_PROC_QT_1        - AQ queue table for the process queue
SAMPLE_TRACKER          - Table, will contain object-region tracking pairs
SAMPLE_TRACKER_LOG      - Table, contains log messages from the server 
SAMPLE_TRACKER_QT_1     - AQ queue table for the tracker queue
SAMPLE_TRACKER_QUEUES   - Table, contains tracking sets queue metadata
SAMPLE_TRACKING_REGIONS - Table, will contain the regions geometry
SAMPLE_TRAJECTORY       - Table, currently unused

-- Start the tracking set
EXEC sdo_trkr.start_tracking_set(‘sample’);

-- Optional: Show the queues used by the tracking set
SELECT name
FROM user_queues
WHERE name LIKE 'SAMPLE%'
ORDER BY name;

NAME
---------------------
SAMPLE_LOCATION_Q_1
SAMPLE_NOTIFICATION_Q
SAMPLE_PROC_Q_1
SAMPLE_TRACKER_Q_1

-- Optional: Show the scheduler jobs used by the tracking set
SELECT job_name, state 
FROM user_scheduler_jobs 
WHERE job_name LIKE 'SAMPLE%'
ORDER BY job_name;

JOB_NAME	    STATE
--------------------------
SAMPLE_LOC_JOB_1   RUNNING
SAMPLE_TRKR_JOB_1  RUNNING


-- Insert a polygon for region 1. This polygon must be geodetic (using SRID 8307) 
-- and two dimensional. The region may also be a multi-polygon.
INSERT INTO SAMPLE_TRACKING_REGIONS VALUES (1,
  MDSYS.SDO_GEOMETRY(2003, 8307, null,
    sdo_elem_info_array(1, 1003, 1),
    sdo_ordinate_array(0,0, 5,0, 5,5, 0,5, 0,0)));
-- Create two objects, object 1 and 2 that are tracked in region 1.
-- Object 1 sends notification messages when it is inside region 1. 
-- Object 2 sends notification messages when it is outside region 1.
EXEC sdo_trkr.send_tracking_msg(
  'SAMPLE', mdsys.tracker_msg(1, 1, 'I'));
EXEC sdo_trkr.send_tracking_msg(
  'SAMPLE', mdsys.tracker_msg(2, 1, 'O'));
-- Optional: Show the object-region pairs used in the tracking set
SELECT object_id, region_id, alert_when  FROM sample_tracker;

OBJECT_ID  REGION_ID  ALERT_WHEN
---------- ---------- -----------
     1	         1        I
     2	         1        O

-- Send 2 location messages.
–- Object 1 moves to (1, 1).
–- Object 2 moves to (8, 8).
EXEC sdo_trkr.send_location_msgs('SAMPLE',
  mdsys.location_msg_arr(
    mdsys.location_msg(1, '01-AUG-16 01.01.46.000000 PM', 1, 1),
    mdsys.location_msg(2, '01-AUG-16 01.02.46.000000 PM', 8, 8)));

-- Optional: Show that 2 notification message were generated
SELECT a.name, b.ready
FROM user_queues a, v$aq b 
WHERE a.name='SAMPLE_NOTIFICATION_Q' AND a.qid=b.qid
ORDER BY a.name;

NAME                   READY
---------------------- ------
SAMPLE_NOTIFICATION_Q    2

-- Dequeue the notification messages into the notifications table
DECLARE
  message       mdsys.notification_msg;
BEGIN
  LOOP   
    sdo_trkr.get_notification_msg(
      tracking_set_name => 'SAMPLE', 
      message => message, 
      deq_wait =>2);	-- wait at most 2 seconds for a message

    IF (message IS NULL) THEN
      EXIT;
    END IF;

    INSERT INTO sample_notifications (
                  object_id, region_id, time, x, y, state) 
      (SELECT message.object_id, message.region_id, 
              message.time, message.x, message.y, message.state);
  END LOOP;
END;
-- Query the object id, region id, (x, y) coordinate and the objects
-- relationship to the region sorted by the time that was sent with
-- the objects location message.
SELECT object_id, region_id, x, y, state 
FROM sample_notifications 
ORDER BY time; 
OBJECT_ID  REGION_ID	X   Y   STATE
---------- ---------- --- --- -------
  1	      1	        1   1   INSIDE
  2	      1	        8   8   OUTSIDE
-- Optional: Disable the tracking server's object-region pairs
EXEC sdo_trkr.send_tracking_msg('SAMPLE', 
  mdsys.tracker_msg(1, 1, 'D'));
EXEC sdo_trkr.send_tracking_msg('SAMPLE', 
  mdsys.tracker_msg(2, 1, 'D'));
-- Stop the tracking set. This stops the tracking sets
-- queues and its scheduler jobs. Running stop_tracking_set 
-- does not delete the tables and queues used by the tracking
-- server so start_tracking_set can be rerun and all of the 
-- object and region data is still available.
-- This must be done before dropping a tracking set
EXEC sdo_trkr.stop_tracking_set('sample');

-- Drop the tracking set. This completely deletes the tracking
-- sets queues and tables. Once completed all traces of the tracking
-- set are removed except for the log table which is left intact for
-- debugging purposes. If another tracking set of the same name is
-- created the log table is truncated.
EXEC sdo_trkr.drop_tracking_set('sample');