On Fri, Jan 28, 2011 at 2:53 PM, Chris Holmes <[email protected]> wrote:
> +1, sounds like a really great improvement. And I'd say that small
> improvements that give a concrete win without becoming bogged down in the
> end all 'right' thing are becoming 'the geoserver way', and this is a great
> step towards joins.
>
> One question, does the (probably lame) WFS specified join stuff kick in at
> all with this? Like is there overlap between what that does and what this
> provides? Or does that only make sense to implement when we get 'real' join
> support? No worries at all if the answer is 'we could do it with these
> constructs, but we don't care about it', I'm just curious, like if a client
> comes along and says 'I want official WFS Joins', if this could be used as a
> basis for a limited version of that. Though I do remember that joins seemed
> to be one of those less thought out areas of the WFS spec.
Well, I don't know the joins the in wfs spec enough to provide you with a full
answer.
The joins I've seen in WFS 2.0 generate a "tuple", which is a
construct containing
two or more features, equivalent more or less to the following
select a.p1, a.p2, b.p3, b.p4
from a inner join b on <join condition>
and the wfs result would look something like:
<tuple>
<a>
<p1>...</p1>
<p2>...</p2>
</a>
<b>
<p3>...</p3>
<p4>...</p4>
</b>
</tuple>
However the case I'm after is joining only for the sake
of filtering.
Not sure the functions I'm going to build will work
in that case, a generic filter might involve multiple
conditions from two or more feature types, I did not
think about it much but it does not look like it would
be something easy to coax into simple single self contained
call to a single layer (which is what the functions I'm proposing
do).
Cheers
Andrea
--
Ing. Andrea Aime
Technical Lead
GeoSolutions S.A.S.
Via Poggio alle Viti 1187
55054 Massarosa (LU)
Italy
phone: +39 0584962313
fax: +39 0584962313
http://www.geo-solutions.it
http://geo-solutions.blogspot.com/
http://www.linkedin.com/in/andreaaime
http://twitter.com/geowolf
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