Re: [gnome-db] GdaDataModel signals

[Diego Zuccato <diego otello alma unibo it>]

Vivien Malerba ha scritto:
>> Is GdaDataModel a rowset which detects changes into database? Or is it
>> like a CachedRowSet in Java [an offline rowset with no notifications of
>> changes in db data]?
> The data model retuned when executing a query does not detect changes
> made in the database (in fact I don't know if any DBMS offers an API
> to do so, if you have any example, please tell me). I think it's like
> a CachedRowSet in Java.

I did it in Postges using NOTIFY and triggers. But it's quite hard to do
it in a general way. And it's quite limited, too, since the NOTIFY
doesn't allow additional data to be passed :( It's too like a *NIX
kill() call...

> Now there is the GdaDataModelQuery object which lets you run a SELECT
> statement and any modification you make to the data model is
> translated into the correcponding UPDATE, INSERT or DELETE queries, so
> the database is modified in the same way as the data model is
> modified.

But it only reflects LOCAL changes. If another client is updating the
db, then THOSE changes are "lost" for the local client.

>> what about if I insert/update a row from an external sqlite console?
> Then you'll see the changes you made if you execute the query again.

Obviously he could setup a NOTIFY trigger in PG to rescan the table
(this is good only for SMALL tables!). The method I used needed a
trigger to insert the modified ROWID and a timestamp in an auxiliary
table, where another trigger issued the NOTIFY to the clients listening.
After a "long-enough" timeout older entries were deleted.
Depending on his architecture, a multi-daemon or some other sort of IPC
might be better.

BYtE,
 Diego.