[Xapian-discuss] DatabaseModifiedError

[Richard Boulton]

On 23 March 2011 10:16, Andrew Betts <andrew.betts at assanka.net> wrote:
> Hi,
>
> I am starting to see more frequent occurrences of a DatabaseModifiedError when users execute searches on my site.  Since our index is being updated all the time, its easy to understand why these happen, but is it possible to ignore this error and execute the search against the stale revision?  It's likely only a few seconds out of date, and if I follow the advice and reopen() the database, it's quite possible that it will have been modified again before I manage to call get_mset.

Xapian can't be told to ignore the error and use the stale revision,
because the error is only thrown when the data Xapian needs from the
old revision has already been overwritten by new data.  If you're
searching on version N, you won't get the error until before version
N+1 has been committed.  After version N+1 has been committed, changes
to the database (ie, leading to version N+2) will start overwriting
blocks which were used in version N (but not in version N+1), and
there is then a risk of the exception being thrown.

Assuming you're updating the index every few seconds, and searches
take no more than a couple of seconds in the worst case you could
perhaps insert a pause after committing a change before performing any
further modifications to the database, to allow readers a chance to
reopen on the new revision before risking overwriting blocks from the
old revision.

-- 
Richard