Rob Audenaerde created LUCENE-5015:
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Summary: 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
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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