in reply to How to Iterate to Identify Concurrent Users

You could use SQL, as tye hinted. Suppose you load your data into a table named sesn (session) with fields sesn_id, usr_id, sesn_bgn, sesn_end and whatever else you may need, properly indexed etc. Then, a query like the following should do what you want (untested): 
SELECT
    foo.usr_id   AS user,
    foo.sesn_id  AS session1,
    bar.sesn_id  AS session2,
    foo.sesn_bgn AS start1,
    bar.sesn_bgn AS start2,
    foo.sesn_end AS end1,
    bar.sesn_end AS end2
FROM
    sesn foo,
    sesn bar
WHERE
    foo.usr_id = bar.usr_id
    AND bar.sesn_bgn >= foo.sesn_bgn
    AND bar.sesn_bgn <= foo.sesn_end
    AND foo.sesn_id != bar.sesn_id
    -- AND (conditions on min duration etc here)

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Here I have assumed that you are trying to track multiple simultaneous sessions by the same user. If that's not what you meant, adjust accordingly.

Hope this helps. Cheers.

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Re^2: How to Iterate to Identify Concurrent Users (SQL)
by Anonymous Monk on Oct 26, 2007 at 13:32 UTC
    Thanks tye and fenLisesi. I initially started with a database model but found it to be more cumbersome. After your good advice, I created a view and ran fenLisesi query with some modifications. It did the trick. Its slow though but it gets me what I need. I'll benchmark it with Perl code to see which is more efficient. You monks rock!!! 
    create view foo as select session_id, start_session, end_session, user
+_id from bar;

    [download]
    </code> Then I ran
    
SELECT DISTINCT foo.user_id AS user, 
foo.session_id  AS session1,
bar.session_id  AS session2,
foo.start_session AS start1,
bar_.start_session AS start2,
foo.end_session AS end1,
bar_.end_session AS end2 FROM foo,bar

WHERE foo.user_id != bar_.user_id 
AND bar_.start_session >= foo.start_session 
AND bar_.start_session <= foo.end_session 
AND foo.session_id != bar_.session_id 
order by start1 ASC;

    [download]
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[d/l]
[select]

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