[mapserver-dev] WFS GetFeature Performance - BBOX vs. Filter

myOpenLayersUName joanne.mcgraw at SYMPATICO.CA
Thu Oct 13 14:50:06 EDT 2011


Hello Mapserver-Dev folks,

I'm hoping someone can comment on something I'm seeing that I can't
understand.

I'm getting significantly different results in terms of performance when I
make what is essentially the same WFS GetFeature request with two different
parameters to define the area to use for the query. The differences are
quite spectacular. If I use a Bbox parameter, I get an answer back in
seconds. If I use a Filter parameter, it takes minutes (the layer has around
1 million records and I'm accessing it through SDE). The responses for each
are correct (2 features' coordinates and attributes); it's just the times to
complete the query that are so different. I've also tried this on a
Shapefile with a million records and it takes 1-2 seconds to get a response
using a BBOX and over a minute using the filter.

We'd prefer to use the Filter parameter because our application is supposed
to support the use of more complex polygons as well as bounding boxes, but
these differences are pretty significant and may require that we re-think
support for WFS GetFeature requests with more complex polygons.

I am working with MapServer 6.0.1 that includes Changeset 12031 (to allow me
to query through SDE without seg-faulting) and 4011.patch (to allow me to
use the maxFeatures parameter).

Any info regarding why these times are so different and what, if anything, I
can do to reduce them (perhaps my filter definition is atypical somehow?)
would be greatly appreciated.

Cheers,
jtm


/mapserv/httpd/cgi-bin/mapserv -nh
"QUERY_STRING=map=/data/nl18/httpd/apps/myApp/map/myMap.map&service=wfs&version=1.0.0&request=getfeature&typename=myLayer&srsName=EPSG:26914&filter=%3Cogc%3AFilter%20xmlns%3Aogc%3D%22http%3A%2F%2Fwww.opengis.net%2Fogc%22%3E%3Cogc%3ABBOX%3E%3Cogc%3APropertyName%3EmsGeometry%3C%2Fogc%3APropertyName%3E%3Cgml%3AEnvelope%20xmlns%3Agml%3D%22http%3A%2F%2Fwww.opengis.net%2Fgml%22%20srsName%3D%22EPSG%3A26914%22%3E%3Cgml%3AlowerCorner%3E435309.38597013%205522753.8537993%3C%2Fgml%3AlowerCorner%3E%3Cgml%3AupperCorner%3E437373.1348557%205523970.9364754%3C%2Fgml%3AupperCorner%3E%3C%2Fgml%3AEnvelope%3E%3C%2Fogc%3ABBOX%3E%3C%2Fogc%3AFilter%3E&maxFeatures=10"

- and -

/mapserv/httpd/cgi-bin/mapserv -nh
"QUERY_STRING=map=/data/nl18/httpd/apps/myApp/map/myMap.map&service=wfs&version=1.0.0&request=getfeature&typename=myLayer&bbox=435309.38597013,5522753.8537993,437373.1348557,5523970.9364754&maxFeatures=10"




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