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CDO object query [message #420537]

Wed, 02 July 2008 09:45

Balazs Molnar

Messages: 28
Registered: July 2009

Junior Member

Hello,

Suppose I have larger collections I would persist in an RDB (maybe with
Hibernate) and would like to retrieve data using some method similar to
SQL where and join conditions. How can I do that in CDO ?

I know I should look this up in manuals but did not have much success.

Thank you in advance,
Balázs

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Re: CDO object query [message #420539 is a reply to message #420537]

Wed, 02 July 2008 10:02

Eike Stepper

Messages: 6682
Registered: July 2009

Senior Member

Hi Balázs,

Comments below...

Balázs Molnár schrieb:
> Hello,
>
> Suppose I have larger collections I would persist in an RDB (maybe
> with Hibernate) and would like to retrieve data using some method
> similar to SQL where and join conditions. How can I do that in CDO ?
Support for extensible query languages is underway (first review/merge
planned this week):

233273: [QUERY] Develop Query mechanism
https://bugs.eclipse.org/bugs/show_bug.cgi?id=233273

Simon may appreciate to go into more detail...

> I know I should look this up in manuals but did not have much success.
Gosh, it's certinly me to be blamed ;-)
Simon took over many of the new 2.0 features to enable me to focus on
maintenance and documentation.

Cheers
/Eike

Cheers
/Eike

----
http://www.esc-net.de
http://thegordian.blogspot.com
http://twitter.com/eikestepper

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Re: CDO object query [message #420542 is a reply to message #420539]

Wed, 02 July 2008 10:15

Balazs Molnar

Messages: 28
Registered: July 2009

Junior Member

Just out of curiosity: why OCL and not EMF Query ?

regards,
Balázs

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Re: CDO object query [message #420544 is a reply to message #420542]

Wed, 02 July 2008 10:32

Eike Stepper

Messages: 6682
Registered: July 2009

Senior Member

Balázs Molnár schrieb:
> Just out of curiosity: why OCL and not EMF Query ?
OCL will not be the only query language supported by CDO.
But it will certainly be the default language since it is the only one
that the repository will be able to serve without special support of the
used IStore.
Other query languages can be contributed by the IStore implementations, e.g.
DBStore --> SQL
HibernateStore --> HQL
...

I'm not very familiar with EMF Query, but my understanding is that it is
a pure client side technology.
As such it *should* be usable with CDO out-of-the-box since CDO models
look to the client like normal EMF models.
But the characeristics of a query mechanism that performs the query on
server side and just returns the found object graphs to the client is
expected to be much better in terms of performance and scalability.

Cheers
/Eike

Cheers
/Eike

----
http://www.esc-net.de
http://thegordian.blogspot.com
http://twitter.com/eikestepper

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Re: CDO object query [message #420579 is a reply to message #420544]

Wed, 02 July 2008 16:40

Ed Merks

Messages: 33142
Registered: July 2009

Senior Member

Eike,

Yes, I don't think EMF Query is as interesting as the general name would
seem to imply.

Eike Stepper wrote:
> Balázs Molnár schrieb:
>> Just out of curiosity: why OCL and not EMF Query ?
> OCL will not be the only query language supported by CDO.
> But it will certainly be the default language since it is the only one
> that the repository will be able to serve without special support of
> the used IStore.
> Other query languages can be contributed by the IStore
> implementations, e.g.
> DBStore --> SQL
> HibernateStore --> HQL
> ...
>
> I'm not very familiar with EMF Query, but my understanding is that it
> is a pure client side technology.
> As such it *should* be usable with CDO out-of-the-box since CDO models
> look to the client like normal EMF models.
> But the characeristics of a query mechanism that performs the query on
> server side and just returns the found object graphs to the client is
> expected to be much better in terms of performance and scalability.
>
> Cheers
> /Eike
>

Ed Merks
Professional Support: https://www.macromodeling.com/

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Re: CDO object query [message #420730 is a reply to message #420539]

Wed, 09 July 2008 03:22

Simon Mc Duff

Messages: 596
Registered: July 2009

Senior Member

Hi Bal

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Re: CDO object query [message #420736 is a reply to message #420730]

Wed, 09 July 2008 10:17

Ed Merks

Messages: 33142
Registered: July 2009

Senior Member

This is a multi-part message in MIME format.
--------------010601050706070803040607
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 8bit

Simon,

Comments below.

Simon McDuff wrote:
> Hi Bal

Ed Merks
Professional Support: https://www.macromodeling.com/

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