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https://issues.apache.org/jira/browse/LUCENE-5015?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13668151#comment-13668151
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Shai Erera commented on LUCENE-5015:
------------------------------------
Rob, you don't need to build Lucene to try what Gilad suggested, just modify
your search code to disable complements. The problem is that if complements
indeed kick in, and from the setup your describe it seems that they do because
you search with MADQ, then sampling isn't done at all, yet the accumulator
still corrects the counts.
After you try it, we can tell if the performance overhead is indeed because of
complements or that the counts are corrected. In either case, I think it will
be good to open up the SampleFixer.
> Unexpected performance difference between SamplingAccumulator and
> StandardFacetAccumulator
> ------------------------------------------------------------------------------------------
>
> Key: LUCENE-5015
> URL: https://issues.apache.org/jira/browse/LUCENE-5015
> Project: Lucene - Core
> Issue Type: Bug
> Components: modules/facet
> Affects Versions: 4.3
> Reporter: Rob Audenaerde
> Assignee: Shai Erera
> Priority: Minor
> Attachments: LUCENE-5015.patch, LUCENE-5015.patch, LUCENE-5015.patch,
> LUCENE-5015.patch, LUCENE-5015.patch
>
>
> I have an unexpected performance difference between the SamplingAccumulator
> and the StandardFacetAccumulator.
> The case is an index with about 5M documents and each document containing
> about 10 fields. I created a facet on each of those fields. When searching to
> retrieve facet-counts (using 1 CountFacetRequest), the SamplingAccumulator is
> about twice as fast as the StandardFacetAccumulator. This is expected and a
> nice speed-up.
> However, when I use more CountFacetRequests to retrieve facet-counts for more
> than one field, the speeds of the SampingAccumulator decreases, to the point
> where the StandardFacetAccumulator is faster.
> {noformat}
> FacetRequests Sampling Standard
> 1 391 ms 1100 ms
> 2 531 ms 1095 ms
> 3 948 ms 1108 ms
> 4 1400 ms 1110 ms
> 5 1901 ms 1102 ms
> {noformat}
> Is this behaviour normal? I did not expect it, as the SamplingAccumulator
> needs to do less work?
> Some code to show what I do:
> {code}
> searcher.search( facetsQuery, facetsCollector );
> final List<FacetResult> collectedFacets =
> facetsCollector.getFacetResults();
> {code}
> {code}
> final FacetSearchParams facetSearchParams = new FacetSearchParams(
> facetRequests );
> FacetsCollector facetsCollector;
> if ( isSampled )
> {
> facetsCollector =
> FacetsCollector.create( new SamplingAccumulator( new
> RandomSampler(), facetSearchParams, searcher.getIndexReader(), taxo ) );
> }
> else
> {
> facetsCollector = FacetsCollector.create( FacetsAccumulator.create(
> facetSearchParams, searcher.getIndexReader(), taxo ) );
> {code}
>
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