[osmosis-dev] pgsnapshot composite index results

[Frederik Ramm]

Hi,

On 22.01.2013 11:17, Paweł Paprota wrote:
> So every WMS map request generates something like this:
>
> SELECT "type",encode(ST_AsBinary(ST_Force_2D("way")),'base64') as "way"
> FROM "public"."view_railways" WHERE  ("way" && ST_GeomFromText('POLYGON
> ((2031543.337480622 6414748.28685562, 2031543.337480622
> 6578323.527363132, 2195118.5779881305 6578323.527
> 363132, 2195118.5779881305 6414748.28685562, 2031543.337480622
> 6414748.28685562))', 900913) AND "type" = 'rail')

Such requests are ideally served by a conditional index (i.e. when you 
create the index with a "WHERE type=rail" clause). Since your WMS is 
probably not running custom queries, you can pre-create these indexes 
and they're not even terribly expensive to create. Having a large number 
of them slows down updates but having them for the 5-10 most 
time-consuming SELECTs is certainly worth it.

Bye
Frederik

-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"