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https://issues.apache.org/jira/browse/SOLR-13132?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17029086#comment-17029086
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Michael Gibney commented on SOLR-13132:
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Thanks for looking into this [~solrtrey]. The merge conflicts were trivial (an
extra accidental change of the word "parallel" to "sweep" in a comment for some
code since removed from master, and the upstream removal of
{{BlockJoinFieldFacetAccumulator}}, which had some incidental changes (obviated
by the removal of the class). I've rebased the original PR ([PR
751|https://github.com/apache/lucene-solr/pull/751]), resolving both conflicts
cleanly in favor of {{master}}.
Sorry for the confusion about the multiple patches. To clear things up, I'd
like to move forward focusing on [PR
751|https://github.com/apache/lucene-solr/pull/751]. PR 751 is functionally
identical to [^SOLR-13132-with-cache-01.patch], with the only changes being
some method name refactoring (I had initially used the word "parallel" to
denote the "single pass" approach to facet collection over multiple DocSet
domains; feedback from several informal reviewers (yourself included iirc,
[~solrtrey]) indicated that the word "parallel" fostered the misconception that
the technique involved had something to do with "parallel _processing_" – i.e.
in the "multithreaded" sense – hence the refactoring in the PR, replacing the
word "parallel" with "sweep").
> Improve JSON "terms" facet performance when sorted by relatedness
> ------------------------------------------------------------------
>
> Key: SOLR-13132
> URL: https://issues.apache.org/jira/browse/SOLR-13132
> Project: Solr
> Issue Type: Improvement
> Components: Facet Module
> Affects Versions: 7.4, master (9.0)
> Reporter: Michael Gibney
> Priority: Major
> Attachments: SOLR-13132-with-cache-01.patch,
> SOLR-13132-with-cache.patch, SOLR-13132.patch
>
> Time Spent: 1h
> Remaining Estimate: 0h
>
> When sorting buckets by {{relatedness}}, JSON "terms" facet must calculate
> {{relatedness}} for every term.
> The current implementation uses a standard uninverted approach (either
> {{docValues}} or {{UnInvertedField}}) to get facet counts over the domain
> base docSet, and then uses that initial pass as a pre-filter for a
> second-pass, inverted approach of fetching docSets for each relevant term
> (i.e., {{count > minCount}}?) and calculating intersection size of those sets
> with the domain base docSet.
> Over high-cardinality fields, the overhead of per-term docSet creation and
> set intersection operations increases request latency to the point where
> relatedness sort may not be usable in practice (for my use case, even after
> applying the patch for SOLR-13108, for a field with ~220k unique terms per
> core, QTime for high-cardinality domain docSets were, e.g.: cardinality
> 1816684=9000ms, cardinality 5032902=18000ms).
> The attached patch brings the above example QTimes down to a manageable
> ~300ms and ~250ms respectively. The approach calculates uninverted facet
> counts over domain base, foreground, and background docSets in parallel in a
> single pass. This allows us to take advantage of the efficiencies built into
> the standard uninverted {{FacetFieldProcessorByArray[DV|UIF]}}), and avoids
> the per-term docSet creation and set intersection overhead.
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