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

[Vivien Malerba <vmalerba gmail com>]

On 13 December 2011 22:39, Daniel Espinosa <esodan gmail com> wrote:

2011/12/13 Vivien Malerba <vmalerba gmail com>:

>
>
> On 13 December 2011 18:22, Daniel Espinosa <esodan gmail com> 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