Xapian discuss - Apr 2007 - Reasonable Time Expectation for Long Queries?

Hi,

  I am rather new to Xapian, and am using it to index some FAQ material.  I
am using xapian 0.9.10, with the default database, which according to the
documentation on the website, appears to be 'quartz'.  As a first test
experiment I have indexed about 710,000 questions, and now I am testing
retrieval times with queries of varying length.

  Things seem to work OK so long as the queries stay small - 1-4 terms, but
my test set has a large number of queries containing 20-60+ terms, and these
take upwards of 7-8 seconds to parse.  I have tested my text processing
code, and this does not seem to be the root of the problem.

  It looks like, after reading the db documentation, that perhaps my first
move should be to reindex everything in a flint db, as the documentation
says that this will be 'appreciably faster'.  My current query code,
taken
from one of the examples, looks like:
Xapian::Query query(Xapian::Query::OP_OR, &string_tokens[0],
&string_tokens[string_tokens.size()]);

Is there anything else I can do to optimize these simple OP_OR queries?  Are
there any other suggestions for optimization, or pointers to places in the
lists where this has been discussed, with fruitful results?

  many thanks in advance,
    Joe

On Thu, Apr 12, 2007 at 12:33:14PM +0900, Josef Novak
wrote:
>  It looks like, after reading the db documentation, that perhaps my first
> move should be to reindex everything in a flint db, as the documentation
> says that this will be 'appreciably faster'.
It's unlikely to make building Query objects faster though as they don't
touch the database.
> My current query code, taken
> from one of the examples, looks like:
> Xapian::Query query(Xapian::Query::OP_OR, &string_tokens[0],
> &string_tokens[string_tokens.size()]);
> 
> Is there anything else I can do to optimize these simple OP_OR queries? 
Are
> there any other suggestions for optimization, or pointers to places in the
> lists where this has been discussed, with fruitful results?
It sounds like the same issue as this, except that was building the
query up pairwise, and using the "in one go" constructor was the
workaround in that case:

http://thread.gmane.org/gmane.comp.search.xapian.general/3974

I thought I'd worked on a fix for that, but I don't seem to have checked
anything in.  I probably unpatched it to work on something else - I'll
dig it out.

Do you have a self-contained (except for Xapian!) small program which
shows this?  Failing that, some example lists of terms which build into
slow queries?

Cheers,
    Olly