[postgis-users] problem with st_collect()

[Marc-André Trottier]

I'm viewing the data with Quantum GIS.
But in PgAdmin, the field 'the_geom' is blank over some size.
It,s not a big problem for me but before viewing the data in Quantum i was
thinking there was no geometry.

Marc-André

2009/8/20 Kevin Neufeld <kneufeld at refractions.net>

> Ah.  How are you viewing the table?  Spatially though a GIS application, a
> psql terminal client, or just through PgAdminIII?  PgAdmin has issues
> displaying fields over a certain size.
> -- Kevin
>
> Marc-André Trottier wrote:
>
>> ok thanks for the advise.
>> finally i got a result but the field 'the_geom' is blank in my table.
>> i calculate the size of the geometry with st_mem_size() and when the
>> geometry is bigger than 32000 bytes, approximately, the field 'the_geom' is
>> blank but there is a geometry.
>>
>>
>> Marc-André
>>
>> 2009/8/20 Kevin Neufeld <kneufeld at refractions.net <mailto:
>> kneufeld at refractions.net>>
>>
>>    Be careful with ST_Collect.   As the name implies, it will collect
>>    all the geometries in the set into a single geometry object.   If
>>    your table is gigabytes in size, running over the whole table will
>>    create a single geometry collection that is gigabytes in size ...
>>    which in all likelihood is really rather useless in any GIS
>>    application and will probably overwhelm your postgresql instance.
>>
>>    ST_Collects is definitely useful, but just be sure you really want a
>>    single (potentially very large and clumsy) geometry object.
>>
>>    -- Kevin
>>
>>    Marc-André Trottier wrote:
>>
>>        hi!
>>        i have a problem with this request :
>>        select st_collect(geometryN(setsrid(the_geom, 32198),1)) from
>>        'table_name';
>>
>>        this will return no results if "the_geom" contain  too much rows
>>        or "the_geom" are too complex.
>>        How can i solve this problem ?
>>
>>        thanks
>>
>>        Marc-andré
>>
>>
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