riaksearch performace when numFound is high

Greg Pascale greg at clipboard.com
Wed Jul 6 14:43:53 EDT 2011


Hi,

I'm looking at ways to improve riaksearch queries that produce a lot of
matches.

In my use case, I only ever want the top 20 results for any query, and
results should be ordered by date (which is encoded in the key). For
searches with few matches (numFound < ~1000), performance is great. For
searches with more matches (numFound > ~10000), performance starts to lag
even though I only ever want the top 20. I assume this is because the system
needs to fetch and sort all of the results to know what the top 20 are, but
I'm hoping I can exploit the constraints of my use case in some way to
increase performance. I've looked at the following approaches.

1) AND the "text:" term with a small date range (e.g. text:<common word> AND
date:[<yesterday to today>]). This reduces the result set, but performance
does not improve. At best, the performance is as good as simply doing the
"text:<common word>" search without the date range, and in some cases worse.

2) Same as above, but make the date an inline field. From what I could find
on the topic, it sounded like this is exactly what inline fields or for, but
I was disappointed to discover it performed far worse than even the compound
query above.

3) In this article <http://blog.inagist.com/searching-with-riaksearch>,
which I was linked to from somewhere on the basho site, the author describes
a technique in which he calls search_fold directly and stops after he's
received enough results. He claims this is possible in his case because
results are returned in key order, and he's chosen his keys to match the
desired ordering of his results. My keys have the same property, as I'm
already using the presort=key option. Is this behavior of search_fold a
lucky side-effect, or is this actually guaranteed to work?

Am I simply expecting too much of riaksearch here, or is there a way to make
this work? If all else fails, I suppose I could divide my data into more
buckets, but I'm hoping to avoid that as it would make querying much more
complex.

Thanks,
-Greg
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