Hi Nuno,
last time a new type of filter was in this commit:
https://github.com/geotools/geotools/commit/47e9259d74482b92244b4dd301363b434e382baf
Thankfully now there are default methods, allowing for quite a bit less
painful extension.
Overall I see where this need comes from and agree with it, a few
notes/questions off the top of my head:
- Can you share how you intend to implement NativeFilter? Is it an
interface with store specific implementations, or does it have a single
one? Which stores will receive a sample implementation of the concept?
- Make sure the functionality is open for programmers but not from the
web (e.g., one cannot setup a XML or CQL filter using it
- Properly document the intended usage of it including notion of
pre/post filter splitting, e.g., if a NativeFilter is supported, but it's
OR-ed with another bit using an unsupported filter function, it will end in
the post, in memory evaluation, and will blow up.This is unavoidable, but
should not be a surprise for users.
Cheers
Andrea
On Mon, Mar 19, 2018 at 11:07 PM, Nuno Oliveira <
[email protected]> wrote:
> Hi all,
>
> Recently I have been dealing with some use cases that require the ability
> to inject some native filters,
> specific for each feature type and non static over time, to the final
> native query build by GeoTools and
> send to the data store.
>
> For example, the content of a feature type is partially controlled by an
> external service who provides a non
> static native query (the request changes over time) that filters the
> content that should be show.
>
> Another use case is a complex authorization rules system where the
> authorization rules are SQL
> expressions that need to be append to the final SQL WHERE clause build by
> GeoTools, the system
> provides SQL expressions for different databases (Oracle, PostgreSQL,
> MySQL, etc ...).
>
> Most of the native filters of this use cases are quite complex and can't
> be translated to OGC filters.
>
> Since we have a pattern here that can be applied to several use cases and
> data stores I have think about
> an approach that would allow extensions, external code, etc ... to inject
> the necessary native filter(s)
> and allow data stores implementations to handle those native filters in an
> harmonized way.
>
> I have come up with the idea of a new filter named *NativeFilter*:
>
> - this filter will NOT be directly usable by the final users, for
> example in WFS requests
>
>
> - if any code try to evaluate it in memory an exception will be throw
>
>
> - it will not break any API and data stores will be free to implement
> is support has needed
>
>
> - it will have a method getNative() that will return a String
> containing the native filter
>
> A new default method would need to be added to the *FilterVisitor*
> interface and a default
> implementation would need to be added to *AsbtractFilterVisitor and
> DuplicatingFilterVisitor *
> classes (like for any other filter).
>
> The data store who wants to supports this filter will need to extends it
> custom visitor, for example,
> for relational databases we only need to add a new visit method to
> *FilterToSQL* visitor.
>
> This gives the necessary flexibility for third party code (codes that use
> GeoTools) to inject native
> filters without any specific extension points or cumbersome handling. It
> is also worth notice unless
> some code is using native filters this will have no impact on other usages.
>
> Any thoughts on this ? Objections ?
>
> King regards,
>
> Nuno Oliveira
>
> --
> Regards,
> Nuno Oliveira
> ==
> GeoServer Professional Services from the experts! Visit http://goo.gl/it488V
> for more information.
> ==
>
> Nuno Miguel Carvalho Oliveira
> @nmcoliveira
> Software Engineer
>
> GeoSolutions S.A.S.
> Via di Montramito 3/A
> 55054 Massarosa (LU)
> Italy
> phone: +39 0584 962313 <+39%200584%20962313>
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> http://www.geo-solutions.ithttp://twitter.com/geosolutions_it
>
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Regards,
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==
GeoServer Professional Services from the experts! Visit http://goo.gl/it488V
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==
Ing. Andrea Aime
@geowolf
Technical Lead
GeoSolutions S.A.S.
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proprietary in nature or covered by the provisions of privacy act
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Code).Any use not in accord with its purpose, any disclosure, reproduction,
copying, distribution, or either dissemination, either whole or partial, is
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