[gnome-db] Updates to Postgres provider

[Vivien MALERBA <malerba gnome-db org>]

Hi!

I've been working on the updates to the postgres provider regarding the
extended schemas (Bug 84357). I've also looked at what the MySQL
provider does and the docs. Here what I have modified/implemented so
far:

* GDA_CONNECTION_SCHEMA_TYPES:
No param taken into account (that should be added), the returned set
holds the following columns:
     - unique ID for the data type (actually a Postgres OID)
     - type name
     - owner name
     - type description

* GDA_CONNECTION_SCHEMA_PROCEDURES:
No param is taken into account (that should be added), the returned set
holds the following columns:
     - unique ID for the procedure (actually a Postgres OID)
     - name of the procedure
     - owner name
     - proc. description
     - return type name
     - number of input arguments
     - list of arguments' types (names separated by a space, and '-'
       when any data type is accepted)
     - definition of the procedure

* GDA_CONNECTION_SCHEMA_AGGREGATES:
No param is taken into account (that should be added), the returned set
holds the following columns:
     - unique ID for the aggregate (actually a Postgres OID)
     - name of the aggretage
     - owner name
     - aggregate's description
     - input type name ('-' if any data type is accepted like for
       COUNT)
     - output type name

* GDA_CONNECTION_SCHEMA_TABLES:
No param is taken into account (that should be added), the returned set
holds the following columns:
     - table name
     - name of the owner
     - table description
     - table definition (NULL field, to be fixed)

* GDA_CONNECTION_SCHEMA_FIELDS:
I haven't modified anything, and so the default value does not appear
anymore as it used to in versions for Gnome 1.4. Maybe we should add it
back?

* GDA_CONNECTION_SCHEMA_VIEWS:
Same as GDA_CONNECTION_SCHEMA_TABLES.

* GDA_CONNECTION_SCHEMA_SEQUENCES:
Same as GDA_CONNECTION_SCHEMA_TABLES.


This differs slightly from what the libgda doc says, but I need the
extra infos for Mergeant. How about updating the sets returned by the
other providers to be the same as for Postgres?

Also, there is no Id column returned for the TABLES, FIELDS (for a given
table), VIEWS and SEQUENCES because their name should be unique; if you
have any example where this is not the case, tell me and we will change
that.

Cheers,

Vivien