If I understand the concept, this feature will not add functionality.
The purpose is to make the statement more efficient
right ?
Andrea Aime writes:
> Andrea Aime ha scritto:
>>> For example:
>>>
>>> SELECT id, name, url, ST_SetSRID(ST_Point(longitude, latitude),4326) as
>>> location FROM non_spatial_table;
>>>
>>> where longitude and latitude are numeric columns.
>>
>> You can, but it would not be worth using performance wise.
>> For example, a bbox filter against the feature type defined
>> above would be turned into the following sql query:
>>
>> select id, name, url, location
>> from
>> (
>> SELECT id, name, url,
>> ST_SetSRID(ST_Point(longitude, latitude),4326) as location
>> FROM non_spatial_table)
>> )
>> where location && <the bbox>
>>
>> which would not give enough info to the db to turn that
>> into a filter against longitude and latitude.
>
> Thinking thinking, evil thinking...
>
> Since we're already giving the user the control to make
> her own query, what about giving her the tools to make her
> own optimizations as well?
> What if, for example, we allow a variable substitution mechanism
> based on the simplest and more common filter, the bbox one?
> We allow the user to add a special part of the definition query
> that is actually expanded only if a bbox filter can be extracted
> from the original gt2 query, and then the user could give the
> jdbc datastore something like:
>
> select id, name, url,
> ST_SetSRID(ST_Point(longitude, latitude),4326) as location
> from non_spatial_table
> {where longitude >= $bbox.minx and longitude <= $bbox.maxx
> and latitude >= $bbox.miny and latitude <= $bbox.maxy}
>
> or something like:
>
> select id, st_buffer(geometry, 1500), name
> from my_spatial_table
> where flow > 143
> {and geometry && $bbox}
>
> Assuming the $bbox would be expanded into the literal representation
> of a bounding box for that database (using the sql dialect).
> Or, to make things a little easier for us, we pass down
> $minx, $miny, $maxx, $maxy and let the user build whatever she
> feels like with them.
>
> Too evil?
>
> Cheers
> Andrea
>
>
>
>
> --
> Andrea Aime
> OpenGeo - http://opengeo.org
> Expert service straight from the developers.
>
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