Right - if you split a table to a lot of more selective tables, it can often dramatically change the plan options (e.g. - in a single table, selectivity for a query may be 1% and require an expensive nested loop while in the more restrictive table it may match 14% of the data and do a cheaper scan).
Also - don't forget that just rebuilding a database cleanly can dramatically improve performance. The only dbms I know that indexes views is MS SQL Server 2000, where it is a limited form of materialized queries. pg doesn't do MQs, but check out functional indices. /Aaron ----- Original Message ----- From: "Gregory S. Williamson" <[EMAIL PROTECTED]> To: "Igor Maciel Macaubas" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Thursday, October 14, 2004 2:45 PM Subject: Re: [PERFORM] Performance vs Schemas Igor, I'm not sure if it is proper to state that schemas are themselves speeding things up. As an example, we have data that is usually accessed by county; when we put all of the data into one big table and select from it using a code for a county of interest, the process is fairly slow as there are several hundred thousand candidate rows from that county in a table with many millions of rows. When we broke out certain aspects of the data into schemas (one per county) the searches become very fast indeed because we can skip the searching for a specific county code with the relevant tables and there is less (unneeded) data in the table being searched. As always, "EXPLAIN ANALYZE ..." is your friend in understanding what the planner is doing with a given query. See <http://www.varlena.com/varlena/GeneralBits/Tidbits/> for some useful information, especially under the performance tips section. HTH, Greg Williamson DBA GlobeXplorer LLC -----Original Message----- From: Igor Maciel Macaubas [mailto:[EMAIL PROTECTED] Sent: Thu 10/14/2004 11:38 AM To: [EMAIL PROTECTED] Cc: Subject: [PERFORM] Performance vs Schemas Hi all, I recently migrated my database from schema 'public' to multiple schema. I have around 100 tables, and divided them in 14 different schemas, and then adapted my application to use schemas as well. I could percept that the query / insert / update times get pretty much faster then when I was using the old unique schema, and I'd just like to confirm with you if using schemas speed up the things. Is that true ? What else I can do to speed up the query processing, best pratices, recommendations ... ? What about indexed views, does postgresql supports it? Regards, Igor -- [EMAIL PROTECTED] ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]