Iterating layer features in mapscript effectively

[Tamas Szekeres]

I have posted a report in

http://mapserver.gis.umn.edu/bugs/show_bug.cgi?id=1491


Tamas


On Thu, 6 Oct 2005 16:02:17 -0500, Steve Lime <steve.lime at DNR.STATE.MN.US>
wrote:

>I bumped my head on this one too recently and relied on the query option
as a
>work around. The second pass is a big deal for some sources but can be
mitigated
>a great deal by doing some indexing. That's another bug though...
>
>If you file a bug we can expose the msLayerWhichShapes and
msLayerNextShape
>functions as layer methods. I can take care of the SWIG end of things and
then
>pass the bug on to the PHP folks.
>
>Steve
>
>>>> Frank Warmerdam <warmerdam at POBOX.COM> 09/28/05 7:40 PM >>>
>On 9/28/05, Tamas Szekeres <szekeres.tamas at freemail.hu> wrote:
>> Hi list,
>>
>> I would like to iterate the features of the layers with mapscript in
order
>> to represent the attributes (of the features drawn) in table format for
>> the user. I think the most effective way of this work would be
supporting
>> the proper functions could be mapped to msLayerWhichShapes and
>> msLayerNextShape similar to msDrawLayer accesses features. The only way
I
>> could find is to call layeobj.getFeature which calls msLayerGetShape to
>> provide random access to features, however there is no interface to find
>> out the range of valid record numbers.
>> Performing querying by rect would be an other way, but it involves much
of
>> overhead by copying all of the features into the result cache.
>
>Tamas,
>
>To the best of my knowledge the various queries just copy the set of
>matching feature ids into the results cache, not the whole features
>themselves.
>
>Of course, as I have indicated before, I think there are significant
>performance issues with the current two pass query approach since
>fetches by feature id are expensive from some backend data providers.
>So it would indeed be desirable to have the direct access to features
>that the drawing functions have accessable to mapscript.
>
>Best regards,
>--
>---------------------------------------+----------------------------------
----
>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