Hi Jody,
No sure I understand your comment:
1. you mean there is already something similar that can be done with query
hints ?
2. or you mean we could use a query hint for this ?
That say, one my first approaches was to take advantage of query hints but I step on to many
limitations, just to /name/// a few:
* query hints at best allows us to say, please happen this to the final query
that will be send to
the data store, but doesn't allow us to build a filter the way we need it
(OR, AND, nested, etc ...)
* the native filter provides a more harmonized approach, the query hint would
have to be managed
explicitly in every part of the code where the final query that will be send
to the data store
is created, this would quickly become a nightmare (note this is not specific
to JDBC data store)
* having a filter allows us to take advantage of all the existing wiring and
processing that
involves filters visitors, e.g. capabilities support, filters splitter, etc
...
Another thing that is worth mentioning, is that for most of the use cases I can think of being able
to use a filter is more /compatible/ for the invokers than setting up a query hint.
Kind regards,
Nuno Oliveira
On 03/21/2018 01:59 AM, Jody Garnett wrote:
do we not have query hints for this purpose?
On Tue, Mar 20, 2018 at 12:07 PM Nuno Oliveira <nuno.olive...@geo-solutions.it
<mailto:nuno.olive...@geo-solutions.it>> wrote:
Hi Andrea,
thanks for the feedback, please see my answers bellow:
On 03/20/2018 10:21 AM, Andrea Aime wrote:
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.
Thanks, yes default methods help indeed.
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?
My idea is to create an interface (this will help with filter visitors):
public interface NativeFilter extends Filter {
Expression getNative();
}
and then provide a default implementation for it, this default
implementation should be
enough for most use cases.
The JDBC data store will be the first one receiving support for it.
* 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
Yes this is an important point indeed, no XML binds or CQL support will be
implemented. The
Filter to CQL visitor will throw an exception.
* 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.
Yep.
Cheers
Andrea
On Mon, Mar 19, 2018 at 11:07 PM, Nuno Oliveira
<nuno.olive...@geo-solutions.it
<mailto:nuno.olive...@geo-solutions.it>> 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
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55054 Massarosa (LU)
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The information in this message and/or attachments, is intended solely for
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nature or covered by
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Italy's New Data
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reproduction,
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==
GeoServer Professional Services from the experts! Visithttp://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
fax: +39 0584 1660272
http://www.geo-solutions.it
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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
fax: +39 0584 1660272
http://www.geo-solutions.it
http://twitter.com/geosolutions_it
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