Xapian discuss - Aug 2023 - DatabaseModifiedError while iterating on mset

I'm already retrying the ->get_mset operations; but now I'm
wondering where I'd hit DatabaseModifiedErrors while inside a
Xapian::MSetIterator loop.

I assume ->get_document is a place where it gets thrown;
but once a document is retrieved, can iterating through
terms in one document (using TermIterator) also throw DB modified?

I'm dumping multiple terms per-document to a stream.
While retrying ->get_document seems straightforward, retrying
midway through a documents terms would require me to introduce
extra checks/buffering to avoid duplicate terms on reopen+retry.

I'm actually redoing some stuff using C++; Perl's method dispatch
gets awfully slow for this.

Thanks.

On Wed, Aug 23, 2023 at 01:53:27PM +0000, Eric Wong
wrote:
> I'm already retrying the ->get_mset operations; but now I'm
> wondering where I'd hit DatabaseModifiedErrors while inside a
> Xapian::MSetIterator loop.
> 
> I assume ->get_document is a place where it gets thrown;
> but once a document is retrieved, can iterating through
> terms in one document (using TermIterator) also throw DB modified?
If you only look at the terms and wdfs then you could only get
DatabaseModifiedError on the call to create the TermIterator since the
list of terms and wdfs is stored in a single entry per document which
is fetched when the iterator is created (it is conceivable this might
be different for a new database backend in the future I suppose).

If you call methods like get_doclength() which need to consult the
database those could throw.

Cheers,
    Olly