Re: Performance issues when the number of records are around 10 Million

Venu,

For starters,

1) You have used the e.cid twice in ORDER BY clause.
2) If you want last twenty records in the table matching the criteria of timestamp, why do you need the offset?
3) Do you have indexes on sig_id, signature and timestamp fields?

If you do not get a good response after that, please post the EXPLAIN ANALYZE for the query.

Thanks,

Shrirang Chitnis
Sr. Manager, Applications Development
HOV Services
Office: (866) 808-0935 Ext: 39210
shrirang.chitnis@hovservices.com
www.hovservices.com


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From: pgsql-performance-owner@postgresql.org [mailto:pgsql-performance-owner@postgresql.org] On Behalf Of venu madhav
Sent: Tuesday, May 11, 2010 2:18 PM
To: pgsql-performance@postgresql.org
Subject: [PERFORM] Performance issues when the number of records are around 10 Million

Hi all,
      In my database application, I've a table whose records can reach 10M and insertions can happen at a faster rate
like100 insertions per second in the peak times. I configured postgres to do auto vacuum on hourly basis. I have
frontendGUI application in CGI which displays the data from the database. When I try to get the last twenty records
fromthe database, it takes around 10-15  mins to complete the operation.This is the query which is used: 

select e.cid, timestamp, s.sig_class, s.sig_priority, s.sig_name, e.sniff_ip, e.sniff_channel, s.sig_config,
e.wifi_addr_1,
e.wifi_addr_2, e.view_status, bssid  FROM event e, signature s WHERE s.sig_id = e.signature   AND e.timestamp >=
'1270449180'AND e.timestamp < '1273473180'  ORDER BY e.cid DESC,  e.cid DESC limit 21 offset 10539780; 

Can any one suggest me a better solution to improve the performance.

Please let me know if you've any further queries.


Thank you,
Venu