[Xapian-discuss] Re: Re: get_docid over multi-database search

[Olly Betts]

On Thu, Dec 20, 2007 at 02:12:30PM +0000, James Aylett wrote:
> I don't actually know how the matcher deals with multiple databases
> right now, but I suspect it does it in a sort of pseudo-parallel [1],

Actually, we process databases sequentially in this case.  After the
first database, we'll usually have an MSet full and so a decent minimum
weight bound, so processing subsequent databases will usually be much
quicker.

This is likely to be more friendly if the databases are on the same
disk(s), though it probably doesn't parallelise load so well if they
aren't.  But if your query load is high, concurrent queries will
tend to do that for you anyway.

I don't think we've tried processing databases in parallel, so it could
be that would work better.  It would be an interesting experiment if
somebody wanted to try it.

Cheers,
    Olly