WFS performance issue

[Frank Warmerdam]

On Tue, 22 Mar 2005 10:19:01 -0500, Yewondwossen Assefa
<assefa at dmsolutions.ca> wrote:
> Frank,
>
>    The WFS code to modify should not be that bad since the functions to
> transalte from filter encoding xml syntax to mapserver expression are
> localized in separate functions and I could twick the code to generate
> sql statements instead of Mapserver expressions and set the layers'
> FILTER.
>   The problem I have is how would I test this ? I do not have Orcacle
> setup here ? What would be my best option to do testing on this ? Could
> I use OGR layers with underlaying layers other than oracle ?

Assefa,

My suggestion would be that you translate to SQL suitable for use
with PostGIS and test that.  Once that is working smoothly, you
could invoke the same code for Oracle and leave it up to Arnulf
to test it.   Hopefully pure attribute WHERE clauses would be pretty
similar between Oracle and Postgres.

In fact, as you suggest you could also just drive this against OGR
as it understands WHERE style FILTER clauses as long as the
filter string is prepended with "WHERE".  It won't generally give
much performance benefit unless the backend is a database.  But
you could setup tests against a given shapefile using direct
mapserver shapefile access (traditional) and then routing the same
requests for OGR with WHERE clauses to verify that both forms are
giving the same results.

One nice thing about OGR based tests is that it would be easy
to add to a test suite.  Also, OGR SQL is so basic that if an SQL
where clause works against OGR SQL it will likely work fine in
Oracle or Postgres.

I think this would be really exciting progress to make, and I will
help out in any way I can.

Best regards,
--
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent