Hi Nuno,
given the need to backport to the stable series option 2) is no go, so I
would choose the enumeration, there is always the
option of expanding it later if we need something in GeoTools, and won't
mess with people upgrading GeoTools like
option 1).
Cheers
Andrea
On Mon, Feb 8, 2016 at 10:21 AM, Andrea Aime <andrea.a...@geo-solutions.it>
wrote:
> Forwarding this one on behalf of Nuno, that is having problems sending
> this mail directly
>
> Cheers
> Andrea
>
> ---------- Forwarded message ----------
> From: Nuno Miguel Carvalho Oliveira <nmco51...@gmail.com>
> Date: Fri, Feb 5, 2016 at 6:44 PM
> Subject: Adding "group by" support to the current aggregation visitors
> To: geotools-devel@lists.sourceforge.net
>
>
> Hi,
>
>
> The current aggregation visitors (AverageVisitor, CountVisitor,
> MaxVisitor, MedianVisitor, MinVisitor, StandardDeviationVisitor and
> SumVisitor) don’t support a “group by” behavior. For example, we are able
> to compute the average electrical consumption per building. But we are not
> able to ask the average electrical consumption per building type.
>
>
> We have came up with three solutions to implement this behavior but none
> of them is perfect.
>
>
> The most straightforward solution would be adding the list of “group by”
> attributes to each current aggregator visitor implementation. But this will
> break backward compatibility with custom store implementations that we are
> not aware of. This solution will also make the current visitors
> unnecessarily more complex, each of them will need to know how to handle
> the “group by” behavior (this can also lead to some code duplication).
>
>
> Another solution is to implement a “group by” visitor that will receive
> an aggregation visitor as a prototype (basically a visitor that will be
> cloned) and a list of “group by” attributes. The current visitors have in
> common the FeatureVisitor interface which is not cloneable. In Java 8 we
> could make the FeatureVisitor extends Cloneable interface and implement a
> default method, but this will not work in GeoServer 2.8.x. So if we extend
> the FeatureVisitor to support Cloneable behavior we are breaking backward
> compatibility. An (awful) solution for this could be implement the
> Cloneable interface in every existing visitor and in the “group by” visitor
> do an “instanceof” checking if the visitor is cloneable. If the visitor is
> not cloneable we could throw an exception or (let's be crazy) do a deep
> serialization copy.
>
>
> Another solution is to implement a “group by” visitor that will receive
> an aggregation visitor name (this would be an Enum), the name of the
> attribute that should be used by the aggregation visitor and a list of
> “group by” attributes. The “group by” visitor will be responsible to
> instantiate the aggregation visitor using the attribute name. The drawback
> of this solution is that the list of supported aggregation visitors will be
> an Enum, which will kill pluggability. So if someone wants to use a new
> aggregation visitor with the “group by” visitor the implementation needs to
> be updated.
>
>
> We will also extend the JDBCDataStore current support for aggregation
> functions to support the "group by" clause.
>
>
> Any feedback on this will be highly appreciated.
>
>
> 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 Poggio alle Viti 1187
> 55054 Massarosa (LU)
> Italy
> phone: +39 0584 962313
> fax: +39 0584 1660272
> mob: +39 333 8128928
> http://www.geo-solutions.ithttp://twitter.com/geosolutions_it
>
> -------------------------------------------------------
>
> AVVERTENZE AI SENSI DEL D.Lgs. 196/2003
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>
> The information in this message and/or attachments, is intended solely for
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> the named addressee(s) and may be confidential or proprietary in nature or
> covered by the provisions of privacy act (Legislative Decree
> June, 30 2003, no.196 - Italy's New Data Protection Code).Any use not in
> accord with its purpose, any disclosure, reproduction, copying,
> distribution, or either dissemination, either whole or partial, is strictly
> forbidden except previous formal approval of the named
> addressee(s). If you are not the intended recipient, please contact
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>
>
>
>
> --
> ==
> GeoServer Professional Services from the experts! Visit
> http://goo.gl/it488V for more information.
> ==
>
> Ing. Andrea Aime
> @geowolf
> Technical Lead
>
> GeoSolutions S.A.S.
> Via Poggio alle Viti 1187
> 55054 Massarosa (LU)
> Italy
> phone: +39 0584 962313
> fax: +39 0584 1660272
> mob: +39 339 8844549
>
> http://www.geo-solutions.it
> http://twitter.com/geosolutions_it
>
> *AVVERTENZE AI SENSI DEL D.Lgs. 196/2003*
>
> Le informazioni contenute in questo messaggio di posta elettronica e/o
> nel/i file/s allegato/i sono da considerarsi strettamente riservate. Il
> loro utilizzo è consentito esclusivamente al destinatario del messaggio,
> per le finalità indicate nel messaggio stesso. Qualora riceviate questo
> messaggio senza esserne il destinatario, Vi preghiamo cortesemente di
> darcene notizia via e-mail e di procedere alla distruzione del messaggio
> stesso, cancellandolo dal Vostro sistema. Conservare il messaggio stesso,
> divulgarlo anche in parte, distribuirlo ad altri soggetti, copiarlo, od
> utilizzarlo per finalità diverse, costituisce comportamento contrario ai
> principi dettati dal D.Lgs. 196/2003.
>
>
>
> The information in this message and/or attachments, is intended solely for
> the attention and use of the named addressee(s) and may be confidential or
> proprietary in nature or covered by the provisions of privacy act
> (Legislative Decree June, 30 2003, no.196 - Italy's New Data Protection
> Code).Any use not in accord with its purpose, any disclosure, reproduction,
> copying, distribution, or either dissemination, either whole or partial, is
> strictly forbidden except previous formal approval of the named
> addressee(s). If you are not the intended recipient, please contact
> immediately the sender by telephone, fax or e-mail and delete the
> information in this message that has been received in error. The sender
> does not give any warranty or accept liability as the content, accuracy or
> completeness of sent messages and accepts no responsibility for changes
> made after they were sent or for other risks which arise as a result of
> e-mail transmission, viruses, etc.
>
> -------------------------------------------------------
>
--
==
GeoServer Professional Services from the experts! Visit
http://goo.gl/it488V for more information.
==
Ing. Andrea Aime
@geowolf
Technical Lead
GeoSolutions S.A.S.
Via Poggio alle Viti 1187
55054 Massarosa (LU)
Italy
phone: +39 0584 962313
fax: +39 0584 1660272
mob: +39 339 8844549
http://www.geo-solutions.it
http://twitter.com/geosolutions_it
*AVVERTENZE AI SENSI DEL D.Lgs. 196/2003*
Le informazioni contenute in questo messaggio di posta elettronica e/o
nel/i file/s allegato/i sono da considerarsi strettamente riservate. Il
loro utilizzo è consentito esclusivamente al destinatario del messaggio,
per le finalità indicate nel messaggio stesso. Qualora riceviate questo
messaggio senza esserne il destinatario, Vi preghiamo cortesemente di
darcene notizia via e-mail e di procedere alla distruzione del messaggio
stesso, cancellandolo dal Vostro sistema. Conservare il messaggio stesso,
divulgarlo anche in parte, distribuirlo ad altri soggetti, copiarlo, od
utilizzarlo per finalità diverse, costituisce comportamento contrario ai
principi dettati dal D.Lgs. 196/2003.
The information in this message and/or attachments, is intended solely for
the attention and use of the named addressee(s) and may be confidential or
proprietary in nature or covered by the provisions of privacy act
(Legislative Decree June, 30 2003, no.196 - Italy's New Data Protection
Code).Any use not in accord with its purpose, any disclosure, reproduction,
copying, distribution, or either dissemination, either whole or partial, is
strictly forbidden except previous formal approval of the named
addressee(s). If you are not the intended recipient, please contact
immediately the sender by telephone, fax or e-mail and delete the
information in this message that has been received in error. The sender
does not give any warranty or accept liability as the content, accuracy or
completeness of sent messages and accepts no responsibility for changes
made after they were sent or for other risks which arise as a result of
e-mail transmission, viruses, etc.
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