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https://issues.apache.org/jira/browse/SOLR-6968?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Hoss Man reopened SOLR-6968:
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Doing some perf testing, i found that the SPARSE representation of HLL can
cause some heinous response times for large sets -- a minor part of the issue
seems to be the slower insertion rate compared to the FULL representation
(documented), but a much bigger factor is that _merging_ multiple (large)
SPARSE HLLs is almost 10x slower then merging FULL HLLs of the same size.
it might be worth adding tuning options and/or hueristics to control if/when
SPARSE representation should be used (in cases where folks have smaller sets
and care more about memory then speed), but for now i'm just going disable it.
> add hyperloglog in statscomponent as an approximate count
> ---------------------------------------------------------
>
> Key: SOLR-6968
> URL: https://issues.apache.org/jira/browse/SOLR-6968
> Project: Solr
> Issue Type: Sub-task
> Reporter: Hoss Man
> Assignee: Hoss Man
> Fix For: Trunk, 5.2
>
> Attachments: SOLR-6968.patch, SOLR-6968.patch, SOLR-6968.patch,
> SOLR-6968.patch, SOLR-6968.patch, SOLR-6968.patch
>
>
> stats component currently supports "calcDistinct" but it's terribly
> inefficient -- especially in distib mode.
> we should add support for using hyperloglog to compute an approximate count
> of distinct values (using localparams via SOLR-6349 to control the precision
> of the approximation)
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