Re: [gnome-db] Branch 5.x series?

On 13 December 2011 22:39, Daniel Espinosa <[email protected]> wrote:

> 2011/12/13 Vivien Malerba <[email protected]>:
> >
> >
> > On 13 December 2011 18:22, Daniel Espinosa <[email protected]> wrote:
> >>
> >> I'm continue in development of Vala extensions on libgda-vala branch,
> >> I can't tell that is API stable, then I don't merge soon.
> >>
> >> But what about to branch 5.0 development and make master point to 6.0
> >> unstable. May we can make API/ABI changes like the ones on GdaNumeric,
> >> I would like to do the same for most GDA structs (GdaBlob and others)
> >> to add API to access its members.
> >
> >
> > I've just created the LIBGDA_5.0 branch for the next 5.0.x releases, and
> now
> > the master branch will be used for the 5.2 release later on, so you'll
> have
> > to merge your branch into master without any perturbation to the 5.0.x
> > versions.
> >
>
> Thanks I'll do it ASAP.
>
> >>
> >>
> >> Even I figure out how to make GdaDataModel a Gee Collection like or
> >> even add LINQ[1] features to Vala using Gee interfaces and GDA as
> >> backend.
> >
> >
> > I'm afraid you'll have to illustrate with an example so I can understand
> > fully what you did.
> >
>
> I did:
>
> * Added a DataModelIterable, this object can be used in foreach
> instructions in Vala or using while instrucctions using standard Gee
> Iterators, to filter GValues or chop a number of GValues. This makes a
> DataModel a linear collection of GValue where you can traverse through
> one per one. This is a proof of concept about to use Gee Collection
> interfaces.
>

The GdaDataModelIter object is an iterator over data models. Did you "wrap"
it or create a new object?


>
> * Added a DataObject to create persistence database objects, you
> derive objects form Gda.DataObject to modify values in a row in a
> table.
>

Could you illustrate its usage with an example?


>
> Work in progress:
>
> * Implementing GdaDataModel Interface in the iterable object (just
> wraps an internal reference to a GdaDataModel)
>
> * Implementing Gee.Collection interface to manage DataModel's GValue
> as a Collection
>
> Future Ideas:
>
> * How to make use of GDA a Collection provider. Programers will be able to:
>
>   - Access GValue stored in a table by using Gee interfaces
>   - Access Rows in the table and filter them by using fields value
> expressions. This may requires to modify or add a new interface to Gee
> like a Collection of Hashes, each hash have field name as key and a
> GValue as value
>   - Filter Data from a database using commands like LINQ by compling
> using Vala. GDA can be called by Vala to pass a string representation
> of the query to execute a query to the database and return a
> Gee.Collection. This may require for GDA to parse these kind of SQL
> commands. A LINQ example code from Wikipedia is:
>
> int someValue = 5;
>
> var results =  from c in SomeCollection
>               where c.SomeProperty < someValue * 2
>               select new {c.SomeProperty, c.OtherProperty};
>
> foreach (var result in results)
> {
>        Console.WriteLine(result);
> }
>
>
> * Ideally All providers could return just Iterable and Collection
> DataModels, but that requires to modify providers implementation. As
> Vala can create C code to refer to, may be using conditionals  is
> possible to include libgdadata.h to return iterable objects.
>

All providers return a GdaDataSelect object, which can be used to write
data back to the database. This object is quite complicated, and I don't
plan to remove it, but if you need some more features out of it, it can of
course be modified.

There is one last question I have: are your extensions to be used only by
programmers using Vala, or (as Vala generates C code) are they also
available to any language like Libgda currently is (through GObject
introspection)?

Regards,

Vivien

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