Thread: Re: Recursive temporal query

Hi,

I am trying to run a recursive cte query on temporal data.

I attach the starting set (temp_station) and the solution set (temp_solution)

A user visits many stations in random order. 

They can enter a station many times but they only exit once. 

After they enter a station X, they can enter other stations or exit other stations, i.e. a station entry/exit can fully contain other stations) but eventually they will exit station X (these are invalid visits to other stations within an entry/exit context for a single station.)

They can validly visit a station multiple times but these visits must not overlap with each other.

The objective is to list the earliest entry time and matching exit time for each valid visit to a station according to the rules above.

My attempt below doesn't recurse and I can't understand what I need to do here. Can anyone shed some light on this?

Regards

Liam

--drop table temp_station;

create table temp_station

(

    station_id int

   ,movement_direction varchar(5)

   ,event_tick char(3)

   ,event_time timestamp with time zone

);

delete from temp_station;

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (1, 'enter', 't01', '2012-10-18 10:23:31');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (1, 'enter', 't02', '2012-10-18 10:31:42');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (1, 'enter', 't03', '2012-10-18 10:41:41');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (1, 'exit', 't04', '2012-10-18 10:48:34');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (2, 'enter', 't05', '2012-10-18 10:54:57');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (2, 'exit', 't06', '2012-10-18 11:01:35');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (3, 'enter', 't07', '2012-10-18 11:10:52');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (3, 'enter', 't08', '2012-10-18 11:20:50');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (4, 'enter', 't09', '2012-10-18 11:29:56');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (3, 'enter', 't10', '2012-10-18 11:37:53');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (7, 'exit', 't11', '2012-10-18 11:44:42');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (3, 'exit', 't12', '2012-10-18 11:53:14');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (4, 'enter', 't13', '2012-10-18 12:02:59');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (4, 'enter', 't14', '2012-10-18 12:12:11');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (4, 'exit', 't15', '2012-10-18 12:20:29');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (2, 'enter', 't16', '2012-10-18 12:26:57');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (2, 'enter', 't17', '2012-10-18 12:34:12');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (9, 'exit', 't18', '2012-10-18 12:40:10');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (2, 'exit', 't19', '2012-10-18 12:48:29');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (5, 'enter', 't20', '2012-10-18 12:54:37');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (5, 'exit', 't21', '2012-10-18 13:00:42');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (6, 'enter', 't22', '2012-10-18 13:06:09');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (6, 'enter', 't23', '2012-10-18 13:15:47');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (6, 'exit', 't24', '2012-10-18 13:23:34');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (6, 'enter', 't25', '2012-10-18 13:29:22');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (6, 'enter', 't26', '2012-10-18 13:37:27');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (5, 'exit', 't27', '2012-10-18 13:45:02');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (6, 'exit', 't28', '2012-10-18 13:53:44');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (7, 'enter', 't29', '2012-10-18 14:00:09');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (7, 'enter', 't30', '2012-10-18 14:08:45');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (8, 'enter', 't31', '2012-10-18 14:14:12');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (8, 'exit', 't32', '2012-10-18 14:20:20');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (7, 'exit', 't33', '2012-10-18 14:28:23');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (2, 'enter', 't34', '2012-10-18 14:35:43');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (2, 'exit', 't35', '2012-10-18 14:44:34');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (8, 'enter', 't36', '2012-10-18 14:51:26');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (8, 'enter', 't37', '2012-10-18 14:59:08');

insert into temp_station (station_id, movement_direction, event_tick, event_time) values (8, 'exit', 't38', '2012-10-18 15:06:10');

--drop table temp_solution;

create table temp_solution

(

    station_id int

   ,movement_direction varchar(5)

   ,event_tick char(3)

   ,event_time timestamp with time zone

);

delete from temp_solution;

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (1, 'enter', 't01', '2012-10-18 10:23:31');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (1, 'exit', 't04', '2012-10-18 10:48:34');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (2, 'enter', 't05', '2012-10-18 10:54:57');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (2, 'exit', 't06', '2012-10-18 11:01:35');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (3, 'enter', 't07', '2012-10-18 11:10:52');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (3, 'exit', 't12', '2012-10-18 11:53:14');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (4, 'enter', 't13', '2012-10-18 12:02:59');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (4, 'exit', 't15', '2012-10-18 12:20:29');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (2, 'enter', 't16', '2012-10-18 12:26:57');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (2, 'exit', 't19', '2012-10-18 12:48:29');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (5, 'enter', 't20', '2012-10-18 12:54:37');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (5, 'exit', 't21', '2012-10-18 13:00:42');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (6, 'enter', 't22', '2012-10-18 13:06:09');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (6, 'exit', 't24', '2012-10-18 13:23:34');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (6, 'enter', 't25', '2012-10-18 13:29:22');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (6, 'exit', 't28', '2012-10-18 13:53:44');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (7, 'enter', 't29', '2012-10-18 14:00:09');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (7, 'exit', 't33', '2012-10-18 14:28:23');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (2, 'enter', 't34', '2012-10-18 14:35:43');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (2, 'exit', 't35', '2012-10-18 14:44:34');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (8, 'enter', 't36', '2012-10-18 14:51:26');

insert into temp_solution (station_id, movement_direction, event_tick, event_time) values (8, 'exit', 't38', '2012-10-18 15:06:10');

with recursive

enter_event as

(

   select row_number() over(order by event_time) as rownum, *

     from temp_station

    where movement_direction = 'enter'

--and station_id in (7, 8)

)

,exit_event as

(

   select row_number() over(order by event_time) as rownum, *

     from temp_station

    where movement_direction = 'exit'

--and station_id in (7, 8)

)

,event_period as

(

select a.rownum, a.station_id, a.event_tick as start_tick, b.event_tick as end_tick, a.event_time as start_time, b.event_time as end_time

  from enter_event a

       join

       exit_event b

          on a.station_id = b.station_id

             -- entry always before exit

             and a.event_time < b.event_time

)

,dtr (rownum, station_id, start_tick, end_tick, start_time, end_time) as

(

select rownum, station_id, start_tick, end_tick, start_time, end_time

  from event_period

 where start_tick = (select min(start_tick) from event_period)

 union all

select a.rownum, a.station_id, a.start_tick, a.end_tick, a.start_time, b.end_time

  from event_period a

      ,dtr b

  where a.end_time < b.start_time

   and a.start_time < a.end_time

   and b.start_time < b.end_time

)

select * from dtr