[mapserver-users] WFS Filter Encoding and resulting DB-queries
stephan.holl at intevation.de
Wed Mar 2 10:25:47 EST 2011
Yewondwossen Assefa <yassefa at dmsolutions.ca>, [20110223 - 22:52:33]
> On 23/02/2011 8:06 AM, Stephan Holl wrote:
> > Hello Assefa,
> > Yewondwossen Assefa<yassefa at dmsolutions.ca>, [20110223 - 07:26:34]
> >> Hi Stephan,
> >> On 22/02/2011 3:44 AM, Stephan Holl wrote:
> >>> Hello list,
> >>> while playing with MapServer WFS Filter Encoding capabilities I
> >>> found some strange things when it comes to form the DB-queries
> >>> (the requested layer is PostGIS-driven).
> >>> It seems that there will always be a full table-scan and later on
> >>> the FE will be applied. Is this done by design?
> >> Filters that do include spatial filters end up using the
> >> mapserver experssions. 'Simple' filters should end be using
> >> traslated into the layer's filter expression and end up being used
> >> by postgis as part of the data selection. What does the filter
> >> encoding looks like?
> > It is not a spatial-filter we use currently. It is an
> > attribute-based IsLike-Filter like seen here, but we use it with
> > POST. So adding a BBOX-related filter as another AND-filter will
> > result in optimized SQL-Query with only the subset fetched from the
> > database? If so, this seems worth to document though.
> The filter you sent as example should use the layer's filter
> element and that should be used when retrieving the data at the
> postgis level. When the layer is in debug mode, MapServer 5.6.x logs
> in this case shows something like (which indicates that the filter is
> used at the postgis level)
> msPostGISLayerWhichShapes query: select .... and ( (NAME like 'Syd%'
> escape '!') )
yes, I will get the above query-entries. But before of that there is
another query stated in the logs:
select * from "projects_with_location" where false limit 0
which pointed me to a (false) conclusion.
Thank you for clarifying thouh.
Stephan Holl <stephan.holl at intevation.de> | Tel.: +49 (0)541-33 508 3663
Intevation GmbH, Neuer Graben 17, 49074 OS | AG Osnabrück - HR B 18998
Geschäftsführer: Frank Koormann, Bernhard Reiter, Dr. Jan-Oliver Wagner
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