Performance hints please

[Clint Johnson]

I don't know of any.  Optimizing the map server configuration is could 
be the wrong way of going about solving your problem

Look into optimizing your database.  Sure there are indexes; but are 
they being used? "explain" can help you determine that
(ie 
http://www.redhat.com/docs/manuals/database/RHDB-7.1.3-Manual/sql/sql-explain.html)


- Are there joins or subqueries going on "under the hood"?  Joins are an 
expensive operation whether there is an index or no index.
- Perhaps an expensive trigger is getting fired for every select?
- etc.

Ed is right, "The amount of geometry involved is so small, the 
bottleneck has to be the raster processing" --  is a bad assumption.  
Retrieving a small amount of data from a large table will take while 
(indexes help).  Performing a join takes even longer.

Explain will explain.








Stephen Davies wrote:
> G'day all.
>
> Does anybody have a howto on Mapserver performance enhancement?
>
> My particular environment of interest is a relatively small set of 
> geometries in a PostGIS database and a collection of geotiff aerial 
> photography images onto which I overlay the geometries.
>
> The geometries are fully indexed, relatively static and vacuum analyzed 
> every night.
>
> One of the options that users have is to request a "movie" of up to 20 
> frames; each of which consists of a background raster plus up to about 
> five circular geometries, about five points and maybe ten other 
> lines/polygons.
>
> The amount of geometry involved is so small, the bottleneck has to be 
> the raster processing. The images are 2m/pixel and are typically 20 - 
> 150 Mb each. The frame extents include most if not all of an image so 
> tiling does not seem relevant.
>
> I have specified 80% JPEG as the output to minimise final image size and 
> this seems successful (at least in terms of size and hence download 
> time)
>
> I am looking for ways to reduce the time taken in the image generation 
> phase.
>
> TIA,
> Stephen Davies
>
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-- 
Clint Johnson
Refractions Research Inc.
Cjohnson at refractions.net