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https://issues.apache.org/jira/browse/LUCENE-5015?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13666190#comment-13666190
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Shai Erera commented on LUCENE-5015:
------------------------------------
Looking at SamplingParams, isn't overSampleFactor enough to decide whether to
over sample or not? It can default to not oversample, with the default
Amortized fixer or some other default (2.0?) if fixer is Takmi. Then user can
change it, and if he passes a fixer which requires over sampling, he should set
that too.
> 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
>
>
> 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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