[Xapian-discuss] Chert backend

[Olly Betts]

On Mon, Oct 18, 2010 at 10:57:03AM +0200, Felix Antonius Wilhelm Ostmann wrote:
> Am 16.10.2010 14:44, schrieb Olly Betts:
> > Chert indexes are smaller.  Chert is faster in almost all cases, and in
> > some cases substantially so.
> 
> Are we talking about 1-5% or 20-50%? Whould you recommend all to change
> to chert if it is possible?

It depends on your queries, but those involving values will probably be
sped up most - for example, a query consisting of just a valuerange was
benchmarked as 70 *times* faster (i.e. 7000%), but that's likely to be
atypical for most real situations.

If you see cases with flint which are disappointingly slow, then there's
a good chance chert will help (and if not, please do report them, so we
can investigate and hopefully improve these cases too).

Generally, it's probably a good idea to consider how and when to migrate
to chert as flint is unlikely to be supported beyond the 1.2 release
series.  If it's easy for you to migrate or performance is particularly
critical, it makes sense to move sooner rather than later.

Note that you can convert a database with copydatabase, but it is quite
slow:

http://xapian.org/docs/admin_notes#converting-a-flint-database-to-a-chert-database

Cheers,
    Olly