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From Yonik Seeley <yo...@lucidimagination.com>
Subject Re: Slow facet sorting - lex vs count
Date Wed, 25 Aug 2010 20:25:15 GMT
On Wed, Aug 25, 2010 at 7:22 AM, Eric Grobler <impalaherd@googlemail.com> wrote:
> Hi Solr experts,
>
> There is a huge difference doing facet sorting on lex vs count
> The strange thing is that count sorting is fast when setting a small limit.
> I realize I can do sorting in the client, but I am just curious why this is.
>
> FAST - 16ms
> facet.field=city
> f.city.facet.limit=5000
> f.city.facet.sort=lex
>
> FAST - 20 ms
> facet.field=city
> f.city.facet.limit=50
> f.city.facet.sort=count
>
> SLOW - over 1 second
> facet.field=city
> f.city.facet.limit=5000
> f.city.facet.sort=count

FYI, I just tried my own single-valued faceting test:
10M documents, query matches 1M docs, faceting on a field that has
100,000 unique values:

facet.limit=100 -> 35ms
facet.limit=5000 -> 44ms
facet.limit=50000 -> 100ms

The times are reported via QTime (i.e. they do not include the time to
write out the response to the client).
Maybe you're running into memory issues because of the size of the
BoundedTreeSet, response size, etc, and garbage collection is taking
up a lot of time?

-Yonik
http://lucenerevolution.org  Lucene/Solr Conference, Boston Oct 7-8

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