alexey created SOLR-5725:
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Summary: Efficient facets without counts for enum method
Key: SOLR-5725
URL: https://issues.apache.org/jira/browse/SOLR-5725
Project: Solr
Issue Type: Improvement
Components: search
Reporter: alexey
Fix For: 5.0
Shot version:
This improves performance for facet.method=enum when it's enough to know that
facet count>0, for example when you it's when you dynamically populate filters
on search form. New method checks if two bitsets intersect instead of counting
intersection size.
Long version:
We have a dataset containing hundreds of millions of records, we facet by
dozens of fields with many of facet-excludes and have relatively small number
of unique values in fields, around thousands.
Before executing search, users work with "advanced search" form, our goal is
to populate dozens of filters with values which are applicable with other
selected values, so basically this is a use case for facets with mincount=1,
but without need in actual counts.
Our performance tests showed that facet.method=enum works much better than
fc\fcs, probably due to a specific ratio of "docset"\"unique terms count". For
example average execution of query time with method fc=1500ms, fcs=2600ms and
with enum=280ms. Profiling indicated the majority time for enum was spent on
intersecting docsets.
Hers's a patch that introduces an extension to facet calculation for
method=enum. Basically it uses docSetA.intersects(docSetB) instead of docSetA.
intersectionSize (docSetB).
As a result we were able to reduce our average query time from 280ms to 60ms.
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