Create ("force") island in "gaps and island" problem - oracle

Question

I have code that's partitioning my data for a gaps and island solution. The data itself is reporting on user activity, time spent working, and idle time based on logged timestamps and activities. My code is working great, but every once in a while I have a user_id that logs a string of activities for one application, goes idle, then returns to the same application to log additional activity. Based on my current code, it looks like the user spent nearly two hours in one application when in reality there was significant downtime in the middle. I want to "force" the creation of an island, restarting the partition if there is a lapse of greater than 30 minutes between activities.
ACTIVITY_DATE | USER_ID | APPL_ID | PR1 | PR2
---------------------------------------------------
11/20/2020 10:55 A 9340 1 1
11/20/2020 10:55 A 9340 2 2
11/20/2020 10:58 A 9340 3 3
11/20/2020 10:58 A 9340 4 4
11/20/2020 10:59 A 9340 5 5
11/20/2020 13:09 A 9340 6 6
11/20/2020 13:09 A 9340 7 7
11/20/2020 13:10 A 9340 8 8
11/20/2020 13:10 A 9340 9 9
11/20/2020 17:12 A 8354 10 1
11/20/2020 17:14 A 8354 11 2
11/20/2020 17:14 A 8354 12 3
The final result needs to restart the partition for column PR2 at the sixth row in this example because the gap between logged activities exceeds 30min for the same appl_id:
ACTIVITY_DATE | USER_ID | APPL_ID | PR1 | PR2
---------------------------------------------------
11/20/2020 10:55 A 9340 1 1
11/20/2020 10:55 A 9340 2 2
11/20/2020 10:58 A 9340 3 3
11/20/2020 10:58 A 9340 4 4
11/20/2020 10:59 A 9340 5 5
11/20/2020 13:09 A 9340 6 1
11/20/2020 13:09 A 9340 7 2
11/20/2020 13:10 A 9340 8 3
11/20/2020 13:10 A 9340 9 4
11/20/2020 17:12 A 8354 10 1
11/20/2020 17:14 A 8354 11 2
11/20/2020 17:14 A 8354 12 3
Here's my current code:
select activity_date, user_id, appl_id,
row_number() over(partition by user_id order by activity_date) rn1,
row_number() over(partition by user_id, appl_id order by activity_date) rn2
from
(select
activity_date, user_id, appl_id, count(*)
from mytable tt
where
user_id in ('A', 'B', 'C')
and activity_date >= trunc(sysdate - 4,'DD')
and activity_date <= trunc(sysdate - 3,'DD')
group by
activity_date, user_id, appl_id) tt

Answer 1

You can use MATCH_RECOGNIZE:
SELECT activity_date,
user_id,
appl_id,
pr1,
ROW_NUMBER() OVER ( PARTITION BY user_id, appl_id, mno ORDER BY pr1 )
AS pr2
FROM (
SELECT t.*,
ROW_NUMBER() OVER ( PARTITION BY user_id ORDER BY activity_date) AS pr1
FROM table_name t
)
MATCH_RECOGNIZE(
PARTITION BY user_id, appl_id
ORDER BY pr1
MEASURES
MATCH_NUMBER() AS mno
ALL ROWS PER MATCH
PATTERN ( activities* last_activity )
DEFINE activities AS
NEXT(activity_date) <= LAST(activity_date) + INTERVAL '30' MINUTE
)
ORDER BY user_id, pr1;
Which, for the sample data:
CREATE TABLE table_name ( ACTIVITY_DATE, USER_ID, APPL_ID ) AS
SELECT DATE '2020-11-20' + INTERVAL '10:55' HOUR TO MINUTE, 'A', 9340 FROM DUAL UNION ALL
SELECT DATE '2020-11-20' + INTERVAL '10:55' HOUR TO MINUTE, 'A', 9340 FROM DUAL UNION ALL
SELECT DATE '2020-11-20' + INTERVAL '10:58' HOUR TO MINUTE, 'A', 9340 FROM DUAL UNION ALL
SELECT DATE '2020-11-20' + INTERVAL '10:58' HOUR TO MINUTE, 'A', 9340 FROM DUAL UNION ALL
SELECT DATE '2020-11-20' + INTERVAL '10:59' HOUR TO MINUTE, 'A', 9340 FROM DUAL UNION ALL
SELECT DATE '2020-11-20' + INTERVAL '13:09' HOUR TO MINUTE, 'A', 9340 FROM DUAL UNION ALL
SELECT DATE '2020-11-20' + INTERVAL '13:09' HOUR TO MINUTE, 'A', 9340 FROM DUAL UNION ALL
SELECT DATE '2020-11-20' + INTERVAL '13:10' HOUR TO MINUTE, 'A', 9340 FROM DUAL UNION ALL
SELECT DATE '2020-11-20' + INTERVAL '13:10' HOUR TO MINUTE, 'A', 9340 FROM DUAL UNION ALL
SELECT DATE '2020-11-20' + INTERVAL '17:12' HOUR TO MINUTE, 'A', 8354 FROM DUAL UNION ALL
SELECT DATE '2020-11-20' + INTERVAL '17:14' HOUR TO MINUTE, 'A', 8354 FROM DUAL UNION ALL
SELECT DATE '2020-11-20' + INTERVAL '17:14' HOUR TO MINUTE, 'A', 8354 FROM DUAL;
Outputs:
ACTIVITY_DATE | USER_ID | APPL_ID | PR1 | PR2
:------------------ | :------ | ------: | --: | --:
2020-11-20 10:55:00 | A | 9340 | 1 | 1
2020-11-20 10:55:00 | A | 9340 | 2 | 2
2020-11-20 10:58:00 | A | 9340 | 3 | 3
2020-11-20 10:58:00 | A | 9340 | 4 | 4
2020-11-20 10:59:00 | A | 9340 | 5 | 5
2020-11-20 13:09:00 | A | 9340 | 6 | 1
2020-11-20 13:09:00 | A | 9340 | 7 | 2
2020-11-20 13:10:00 | A | 9340 | 8 | 3
2020-11-20 13:10:00 | A | 9340 | 9 | 4
2020-11-20 17:12:00 | A | 8354 | 10 | 1
2020-11-20 17:14:00 | A | 8354 | 11 | 2
2020-11-20 17:14:00 | A | 8354 | 12 | 3
db<>fiddle here