performance issues with DBI module when data too big

<div style="background-color:"><div><div><div></div><div></div><p>Hi all,<p>I have developped a perl script to populate
adatabase with two tables: sessions and actions.<p>the table actions contains the following columns: session_id, url,
timestamp.The column session_id references to the table sessions. <p>the table sessions contains the following columns:
session_id,remote_ip, phone_type, phone_number. The column session_id is serial.<p>The lines of the table actions which
arepart of the same session have the same session_id.<p>There are then more lines in the table actions than in the
tablesession.<p><br />To fill the two tables, I first need to know if the session already exists for a certain
phone_type,a certain remote_ip and a certain phone_number:<p>SELECT session_id FROM sessions WHERE (phone_number =
?) AND(remote_ip  = ?) AND (phone_type = ?) ORDER BY session_id;<p>I also need to apply a criteria to know if I have
to adda new entry in the table sessions or not:<p>SELECT (max(timestamp) + ?)<? FROM actions WHERE (session_id = ?);
 <p> <p>If the session already exists I add a line in the table actions with a INSERT<p>If the session doesn't exist or
ifthe criteria is true, I add a line in the table sessions with an INSERT, retrieve the session_id of the line just
addedwith the following request<p>SELECT session_id FROM sessions where (msisdn=?) AND (remote_ip=?) AND
(user_agent=?) ORDER BYsession_id DESC LIMIT 1<p>and the add with a INSERT a line in the table actions.<p>I have put
indexeson sessions(session_id), sessions(msisdn), actions(session_id).<p>My problem is that populating my database is
slower when the data gets bigger and the performance falls dramatically. I thought that is would be improve with my
indexesbut the problem still persists.<p>Could you please give me some clues that could solve this
issue.<p>Thanks.<p><br/> <br /><br />Nicolas Nolst <div></div><div></div><img
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