Re: [gnome-db] Gda Column question.

[Bas Driessen <bas driessen xobas com>]

On Thu, 2008-10-09 at 09:52 +0200, Vivien Malerba wrote:
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>     2008/10/8 Bas Driessen <bas driessen xobas com>
> >         
> >     
> >         On Thu, 2008-10-02 at 20:50 +0200, Vivien Malerba wrote: 
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> > >             
> > >             2008/10/1 Vivien Malerba <vmalerba gmail com>
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> > > >                 
> > > >                 2008/10/1 Daniel Espinosa <esodan gmail com> 
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> > > > >                     In V4 you have GdaMetaStore to get columns and others db objects information. In order to get that information you have to do:
> > > > >                     
> > > > >                     - Get a GdaMetaStore from a GdaConnnection using gda_connection_get_meta_store
> > > > >                     - Update meta information gda_connection_update_meta_store
> > > > >                     - Get columns information using gda_meta_store_extract and use GdaDataModel API to access to the required information
> > > > >                     
> > > > >                     The required SQL to do it could be:
> > > > >                     
> > > > >                     SELECT *  FROM _columns WHERE table_schema = ##schema::string AND table_catalog = ##catalog::string AND table_name = ##table::string
> > > > >                     
> > > > >                     For gda_column_get_scale you can use numeric_scale column; sorry but don't know about defined_size.
> > > > >                     
> > > > >                 
> > > >                 
> > > >                 You can use the numeric_precision or numeric_scale columns, with both these columns you should have all the characteristics of a column.
> > > >                 Now, this was to get meta data information. I agree that I've been a bit too quick in simplifying the GdaColumn API and I should bring back the API which handles numeric presicion and scale, but probably not as it was. Let me think about it.
> > > >                 
> > > >             
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> > >             In Rev #3221, I've added functions to set any attribute (as (name, value) pairs) to GdaColumn, GdaHolder and the GdaMetaTableColumn, which means those 3 types of objects (well the last one is not an object) can pass onto the other attributes. For example when creating a GdaDataModelIter, the attributes for each GdaHolder are set from those of the corresponding GdaColumn of the data model the iter is for.
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> >         Looking at these new gda_column_get/set_attribute functions. Still it is not clear to me how to get the size and scale of a column. Again, in V3,  I just use gda_column_get_defined_size and gda_column_get_scale and done. Can you please give a small example/snippet how to use this with these new functions?  How/where can I find out about the attribute names? 
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> >     
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>     const GValue *value;
>     value = gda_column_get_attribute (column, GDA_ATTRIBUTE_NUMERIC_SCALE);
>     You can use any of the predefined attribute names in gda-attributes-manager.h
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>     However, these attributes are not yet AFAIK set by any database provider. 
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Ok, this appears to work. Thanks for that Vivien. As you expected, it has not been implemented yet for the providers.

Can you perhaps give me some (rough) pointers of how/where to implement this GDA_ATTRIBUTE_NUMERIC_SCALE (and other attributes) for some of the database providers? Is there a similar situation in place already that I can use as an example? 

Thanks,
Bas.

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