Xapian discuss - Aug 2007 - Closing a DB

Hi, 

As part of my whole indexing thing, I want to move the databases 
around, from within the code. So, I figured that the safest bet 
would be to close the DB before attempting to move it. 

But there's no Xapian::Database::close() or even 
Xapian::WritableDatabase::close().

I have a global variable that holds the database, and I open it
in the main():

// globals
Xapian::WritableDatabase g_Xap;

int main( int argc, char ** argv )
{
    g_Xap = Xapian::WritableDatabase( ... );
}

So, I was thinking, in order to close it successfully, i 
could do this:

g_Xap = Xapian::WritableDatabase();

But that doesn't force a close, it just does the whole refcount 
thing, which could potentially leave it open if someone still 
has it laying around.

Why is there no close() method? What's the "official" way to 
close a DB?

Cheers.

I was actually having this similar issue today as well (but using PHP).
Inside a loop, I open certain databases based on a variable, which could
have a re-occuring value. On those occasions that the value re-occurs, it
tries to create a new XapianWriteableDatabase object with that value again
but fails and throws an exception saying there is already a lock on that
database. I was thinking that I needed a way to close the database before
the last lines of the loop.

Anyone know the proper way to close a database?

Benny

On 8/8/07, David Morris <dmorris@sirca.org.au>
wrote:
>
> Hi,
>
> As part of my whole indexing thing, I want to move the databases
> around, from within the code. So, I figured that the safest bet
> would be to close the DB before attempting to move it.
>
> But there's no Xapian::Database::close() or even
> Xapian::WritableDatabase::close().
>
> I have a global variable that holds the database, and I open it
> in the main():
>
> // globals
> Xapian::WritableDatabase g_Xap;
>
> int main( int argc, char ** argv )
> {
>     g_Xap = Xapian::WritableDatabase( ... );
> }
>
> So, I was thinking, in order to close it successfully, i
> could do this:
>
> g_Xap = Xapian::WritableDatabase();
>
> But that doesn't force a close, it just does the whole refcount
> thing, which could potentially leave it open if someone still
> has it laying around.
>
> Why is there no close() method? What's the "official" way to
> close a DB?
>
> Cheers.
>
>
> _______________________________________________
> Xapian-discuss mailing list
> Xapian-discuss@lists.xapian.org
> http://lists.xapian.org/mailman/listinfo/xapian-discuss
>

David Morris wrote:
> As part of my whole indexing thing, I want to move the databases 
> around, from within the code. So, I figured that the safest bet 
> would be to close the DB before attempting to move it. 
> 
> But there's no Xapian::Database::close() or even 
> Xapian::WritableDatabase::close().
...
> g_Xap = Xapian::WritableDatabase();
> 
> But that doesn't force a close, it just does the whole refcount 
> thing, which could potentially leave it open if someone still 
> has it laying around.
It's worse that that - in fact, if there is any xapian object _derived_ 
from the WritableDatabase (like a PostingIterator) still around, the 
database won't get closed (though you won't be able to access it).
> Why is there no close() method? What's the "official" way to 
> close a DB?
It would definitely be good to add a close() method.  There is an open 
bug about this issue: see 
http://www.xapian.org/cgi-bin/bugzilla/show_bug.cgi?id=173

Unfortunately, it's not that easy to add a close() method, because it 
would also require all the objects which use a database to cope with the 
database being closed underneath them.  It'll get implemented at some 
stage, but we've been trying to think of a neat way of doing so...

[Actually, bug #173 only discusses adding a close() method to the 
bindings, but I think the only plausible way of doing that would be to 
add a close() method to the C++ interface, and wrap it.]

Feel free to comment on #173 if you have any thoughts.

-- 
Richard