[Xapian-discuss] Re: Closing a DB

[Olly Betts]

On Fri, Aug 10, 2007 at 10:14:52AM +0100, Richard Boulton wrote:
> David Morris wrote:
> >Is there a method to get
> >information from the DB object? As in, is it open, etc, etc. That way I can
> >assert for it in my tests.
> 
> No - because if you have the DB object around, you have a reference to 
> it, so it won't be closed...

You could try to open the DB for writing if you want to test that it's
actually been closed, but that's a bit heavyweight for an assertion.

> >Thing is, if the database has been explicitly closed, any access to
> >it can throw an exception, and none of the objects will have cope
> >with anything, right?
> >
> >(I haven't actually looked at the internals, but) this would mean
> >that every call would have a little bit of overhead to check to see
> >if the DB has been closed, but that's about it.
> 
> Yes - however, some of the accesses are performed very frequently in 
> performance critical situations: eg, access to posting lists is 
> performed very frequently when doing a match.  It may not make much of 
> an impact to add a check, but I'm wary of doing so without first 
> measuring the effect...

I'm not too concerned about that (it should simply be a flag check
or comparing a pointer to NULL or similar) though it would be good to
check that the extra overhead isn't measurable.

The main issue I see here is simply that this is likely to touch a lot
of places in the code, which makes it potentially rather disruptive.  

It would certainly be good to be able to sort this out though.

Cheers,
    Olly