[gnome-db] Update meta store (again)

[Piotr Pokora <piotrek pokora gmail com>]

Hi!

I am quite confused with meta store functionality.
First, all operations are very slow (if you compare to direct RDBM
queries) and frnakly speaking I have no idea how to improve them.
Second, I have problems with GdaConnection options.

All is working fine, when I open connection with GDA_CONNECTION_OPTIONS_NONE

and update meta store on demand:
https://github.com/midgardproject/midgard-core/blob/ratatoskr/src/midgard_core_query.c#L58

I tried to set up the same database as meta store, which seems to
improve performance a bit, but fails with postgres provider:

syntax error at or near "'Nullable'"
LINE 1: ...eric_precision, c.numeric_scale, c.is_nullable AS
'Nullable'...^,
No:(-1), src:gda-postgres, SQL: 42601

Setting GDA_CONNECTION_OPTIONS_AUTO_META_DATA doesn't help, as meta
store has to be updated still after any table layout change.

I am finding some examples here and there, and my question is:
What is the best way to manage meta store?
Code complexity doesn't matter. It should work and have acceptable
performance.

For now, I should support libgda 4.0.12 (Debian stable), 4.2 and 5.x.

Piotras