[postgis-users] problem with st_collect()

[Marc-André Trottier]

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>

> 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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