[Xapian-devel] about 'DatabaseModifiedError' and 'reopen'

[Bron Gondwana]

On Thu, Oct 23, 2014, at 10:52 PM, 没有锂称 wrote:
> Hello! I found a problem when write and read at the same time. When I
> read the Database, there will appear 'DatabaseModifiedError' at
> sometimes. then I had to catch the 'DatabaseModifiedError', reopen the
> Database and repeat the last operation. But when the number of
> concurrent of the write is very high, the error
> 'DatabaseModifiedError' will often appear. So, it seems not a good
> idea to catch and reopen the Database. Is there another method to
> resolve the problem?‍

We just use a separate external locking system, which is kind of sad -
but it gets the job done :)

Here's the full comment before we take the lock (which used to pass
/*read*/0 as the last param)

/* we grab an activefile writelock to index. Strictly we don't need it,
but * doing this guarantees we never write under a client which is
reading, which * avoids this: * * IOERROR: Xapian: caught exception: :
DatabaseModifiedError: The revision * being read has been discarded -
you should call Xapian::Database::reopen() * and retry the operation * *
in theory, this will go away eventually, and we can switch back to
write: 0 * in this code. * *
http://grokbase.com/t/xapian/xapian-discuss/0667ppbks8/#20060608j8x5aeept49dv5fm8d02xkczgr
* * "This is almost invariably caused by updating a database while
reading * from it. If two updates are committed before the read
completes, you * get this error (it's DatabaseModifiedError). It's a bit
of a pain * and will be going away in the future, but it's not too hard
to design * to avoid it happening at least." */ active =
activefile_open(mailbox->name, mailbox->part, &tr->activefile,
/*write*/1);

Cheers,

Bron.

--
Bron Gondwana brong at fastmail.fm


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