Performance hints please

[Frank Warmerdam]

Stephen Davies wrote:
> Thanks for the feedback. I have been distracted by easter and other 
> priorities and have only just got back to this question.
> Here is a sample explain output. I think it says that my DB structure is 
> OK. (The statement is taken from a log of a mapserver session.)
> 
> The biggest geometry table in this database has only 166 rows.
> 
> I don't know whether the connection is persistent or not. How does 
> mapserv manage connections?

Stephen,

Persistent connections are not important for PostGIS.  Connection cost
for postgres is very modest.  The situation is very different for
Oracle or any SDE fronted database.

> The TIFF rasters that I am using are included in their entirety. That 
> is, the map extent is the same or bigger than the image. Are overviews 
> still relevant in this context?

It depends how large the rasters are.  If they are large then this is
exactly the circumstance in which overviews would help a lot.  When I
say "if they are large" I really mean are they substantially higher
resolution then the map image you want to generate.

> What is the significance of the OID use? This table (and all others) has 
> a proper unique key.

I'm afraid I don't know anything about this.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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