[mapserver-users] WFS Filter Encoding and resulting DB-queries

[Stephan Holl]

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[1], 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.

> > Using URL-substitutions of the Search-keyword and apply it to a
> > FILTER-element the resulting SQL-query has the given WHERE-filter
> > set. But this opens the door for SQL-injections AFAIK. Setting the
> > validation pattern is a little prevention.
> >
> > Are there any other ways to realize a keyword-driven search with
> > MapServer beside FE IsLike or FILTER-substitution?
> >

Best

	Stephan

[1]
http://demo.mapserver.org/cgi-bin/wfs?&VERSION=1.0.0&SERVICE=WFS&REQUEST=GetFeature&TYPENAME=cities&Filter=%3CFilter%3E%3CPropertyIsLike%20wildcard=%27*%27%20singleChar=%27.%27%20escape=%27!%27%3E%3CPropertyName%3ENAME%3C/PropertyName%3E%3CLiteral%3ESyd*%3C/Literal%3E%3C/PropertyIsLike%3E%3C/Filter%3E

-- 
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
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