Adam:

I dont fully agree with you. If the process can be improved, why dont do?
I've set my new field as "not null default = 0". At least gbak should see if
there are "default values" and apply them during restore!
I dont know how other DB engines resolves that problems, but I'm prety sure
that dont do what gbak does (At least SQL Server doesnt).

Regards!

2006/11/30, Adam <s3057043@...>:

>
> --- In firebird-support@yahoogroups.com, Jorge Andres Brugger
> <jorge.brugger@...> wrote:
> >
> > You can add a field to a table, and set it to "not null", even if that
> > table already has data. Ok. Backup that database, and you cant restore
> > it because that "not null" field containing nulls. If you use the
> switch
> > of gbak to skip data validation, you lost _all_ your checks (not only
> > problematic ones).
> > If live database can contains nulls where it shoudnt be, then backup
> > should restore database exactly as there was before backup.
> > Or, at least, no restore only that problematic checks.
> >
> > Maybe you have a better solution? I'm waiting to read it! :)
> >
>
> Pick up the toppled bottle rather than mopping it up every time the
> floor becomes too wet.
>
> It is indeed a 'gotcha', that one can add a not null field yet fail to
> do something about pre-existing data. Until there is a DDL to convert
> an existing field to not null though, there is no other option but to
> say remember to do an update statement. If such DDL existed, you could
> disable adding a not null field. Instead, you add a nullable field,
> and attempt to convert it to not null, which would fail if there were
> any nulls.
>
> You should always as matter of process test that your backup can be
> restored to a temporary location as part of your backup procedure.
>
> In any case, even if you lose all your checks, you should still have
> access to your data. Run appropriate DML statement(s) to fix your
> data, then pump it using a data pumping tool into an empty database
> using something like CleverComponents IBDatapump.
>
> Or if your database is fine, do it in the live one then take a backup
> and restore to a temp location until you get no errors.
>
> There is a backup model in Firebird 2 for what you want, something
> that backs up the file and restores it 'as is'. It is called NBackup,
> and simply makes it safe to XCopy the database. But you don't get the
> advantages of a backup-restore cycle.
>
> Adam
>
>
>
>
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