queryByAttributes...

[Sean Gillies]

On Apr 12, 2005, at 12:07 PM, Paul james wrote:

> Thank you Sean... I thoung '1' means sucess ...
>
> so, my queryByAttributes() is always returning 1 (Failure)... I dont
> know why... I think is problem with any parameter...
>
> string value = "'[state]' = 'test'";
> layer.queryByAttributes(mp,"state", value, 0)
>
> I have a state column in my table :  > state varchar
> And I have a 'test' line as well ... And the 'test' point is in my
> extents mp ...
> so, any other idea?
>
> thank you...
>
> On Apr 12, 2005 2:45 PM, Sean Gillies <sgillies at frii.com> wrote:
>> On Apr 12, 2005, at 11:17 AM, Paul james wrote:
>>
>>> I=B4m with problems using queryByAttributes... getResult(0) always
>>> return n=
>>> ull...
>>> any idea?
>>> ps.: using c#
>>>
>>> thx
>>>
>>> =20
>>>
>>> layer =3D mp.getLayerByName("layer");
>>> string value =3D "'[oid]' =3D '32141'";
>>> if ((layer.queryByAttributes(mp,"oid", value, 0))=3D=3D1)
>>> {
>>>       resultCacheMemberObj result =3D new resultCacheMemberObj();
>>>       result =3Dlayer.getResult(0);
>>> }
>>>
>>>
>>
>> Is it just me, or is the listserv mangling this (and other) emails?
>>
>> I'm assuming you are using MapServer 4.4.  First, of all, you should
>> generally compare integer results from mapscript to
>> mapscript.MS_SUCCESS (0) and mapscript.MS_FAILURE (1).  Second, I
>> think
>> you really should be doing something like this:
>>
>>     layerObj layer = mp.getLayerByName("layer");
>>     ...
>>     layer.queryByAttributes(...);
>>     resultCacheObj results = layer.getResults();
>>     if (results)
>>     {
>>         resultCacheMemberObj result = results.getResult(0);
>>     }
>>
>> Keep in mind that the extents of your 'mp' map are used to filter
>> results.  If you query by attributes for a feature outside the map
>> extents, it will not be found.
>>
>> cheers,
>> Sean
>>

1 is just a number :)  MapServer follows an old C convention for
success and failure.

I overlooked that you have a PostGIS layer.  The qstring parameter of
queryByAttributes becomes, during the query, the layer's filter.  You
can't use a mapserver logical expression for a postgis layer filter.
You must use a snippet of SQL instead, like this:

     string qstring = "state = 'test'";
     layer.queryByAttributes(mp, "state", qstring, 0);

the qstring is turned into an SQL clause: "WHERE state = 'test'".  So
that's the crux of it, use your layer's specific filter syntax in
queryByAttributes.

cheers,
Sean

--
Sean Gillies
sgillies at frii dot com
http://users.frii.com/sgillies