[Mapserver-users] Mapserver WFS performance

[Bart van den Eijnden]

Hi Steve,

just for clarity.

I was not referring to the MAXFEATURES parameter of the Mapserver MAP file.

I was referring to the MAXFEATURES parameter which is part of the OGC WFS 
interface (passed over HTTP GET to the Mapserver WFS).

Maybe ofcourse Mapserver WFS internally passes this the same way to the 
Mapserver core as the MAXFEATURES parameter from the MAP file. This I 
don't know.

Best regards,
Bart

On Mon, 02 Feb 2004 17:04:12 -0600, Steve Lime 
<steve.lime at dnr.state.mn.us> wrote:

> Checkout bug 553 for more discussion on this topic...
>
> Note that MAXFEATURES was always intended for display, not query,
> purposes.
>
> Steve
>
>>>> Frank Warmerdam <warmerdam at pobox.com> 2/2/2004 4:07:34 PM >>>
> Yewondwossen Assefa wrote:
>> Here is how things work :
>>   - the user does a wfs request
>>   - in is translated in mapserver query : the query does not take
> into
>> account the maxfeatures.
>>    - The MAXFEATURES is taken into account when generating the
>> resulting   gml file
>>
>>   So yes, It ends up doing the query on all the shapes in your case.
>>
>>  I think we should modify mapserver low level query functions to be
> able
>> to pass a maxfeature parameter. Some of the query functions have a
> mode
>> (single or mulitple), and this notion should be extended to support a
>
>> maxfeature. Once this is done the wfs interface can take advantage of
> it.
>
> Assefa, and others,
>
> On a vaguely related note, the current query interface seems to make a
> pass generating the 'item ids' for all the features which match the
> query.  Then when the query is returned another pass is made fetching
> the
> shapes by id.  With shapefiles this isn't particularly expensive,
> though it
> does presumably result in the features being parsed from the binary
> twice.
>
> But for some OGR supported formats fetching "by id" can be very
> expensive.
>
> If we are restructuring the query mechanism what are the chances of
> reviewing
> this whole two pass approach?  Since WFS is basically always using the
> query mechanism it seems this is a significant performance issue for
> some
> WFS setups.  Even for "good formats" there is a bunch of overhead.
>
> Of course, I may be mis-understanding how things are working ... I've
> only
> glanced at it.
>
> Best regards,
>



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