[Mapserver-users] filter with shp

[Jan Hartmann]

John,

As Steve says, you don't need FILTER to select from shapfiles. Just 
define a CLASS like:

CLASS
   ...
   EXPRESSION "([TIMEBEG] < 1500 AND [TIMEEND] >= 1500)"
END


Take care of the syntax! Quoting from the MapFile reference (under CLASS 
/ EXPRESSION):

 > Logical expressions allow you to build fairly complex tests based on
 > one or more attributes and therefore are only available with
 > shapefiles. Logical expressions are delimited by parentheses
 > "(expression)". Attribute names are delimited by square brackets
 > "[ATTRIBUTE]". These names are case sensitive and must match the items
 > in the shapefile. For example: EXPRESSION ([POPULATION] > 50000 AND
 > '[LANGUAGE]' eq 'FRENCH') ... The following logical operators are
 > supported : =,>,<,<=,>=,=,or,and,lt,gt,ge,le,eq. As you might expect
 > this level of complexity is slower to process.


On your second question: you can specify an expression dynamically in 
the calling URL:

http://.../mapserv?map=my.map&layer=...&map_layer_0_class_0.expression="{...)"

See the end of the MapFile reference for this very powerful mechanism.

-------------------------------------------------------------------------

BTW I'm not sure if the FILTER statement works as specified in the CVS 
version of MapServer. I tried the following on a world-map:

FILTERITEM name
FILTER France

and got a map of France. However

FILTER "name='France'"

gave back the whole world. I tried various permutations of quotes, 
brackets and capitals, but always got back the whole world. Am I missing 
something?

Jan


John Hagstrand wrote:
> Hi Steve,
> 
> Thanks for the reply.  I have a shapefile containing 500 polygons.  For 
> any given map request I want to pull out some two or three hundred 
> polygons depending on the value of a field.  So I tried doing this:
> 
> FILTER 'TIMEBEG < 1500 AND TIMEEND >= 1500'
> 
> That gets me an error.  Is there some way I can accomplish this objective?
> 
> Then of course there's another step: I want to vary the 1500 value 
> dynamically.  I wonder if there's a way to do that without rewriting the 
> whole mapfile each time.
> 
> How would you recommend I go about this?
> Thanks
> John
> 
> At 05:26 PM 3/18/2003, Steve Lime wrote:
> 
>> There's not much reason to use FILTER with shapefiles unless you're
>> doing itemquery's. Filters exist primarily as a mechanism to invoke
>> vendor specific SQL engines prior to MapServer getting access to
>> features.
>>
>> Steve
>>
>> >>> John Hagstrand <john.hagstrand at interageresearch.com> 03/16/03
>> 09:15PM >>>
>> Hi,
>>
>> Can you direct me to an example using a FILTER with a shapefile?
>>
>> Thanks
>> John
>>
>> -------------------------------------------------
>> John Hagstrand
>> Interage Research, Inc.
>> 847 838 5371
>> Software Development Consulting for Internet Content Management
>> We make knowledge accessible, useful, and relevant for everyone.
>> http://www.interageresearch.com
>>
>>
>> _______________________________________________
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>> Mapserver-users at lists.gis.umn.edu
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> 
> 
> 
> -------------------------------------------------
> John Hagstrand
> Interage Research, Inc.
> 847 838 5371
> Software Development Consulting for Internet Content Management
> We make knowledge accessible, useful, and relevant for everyone.
> http://www.interageresearch.com
> 
> 
> _______________________________________________
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> 


Jan Hartmann
Department of Geography
University of Amsterdam