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https://issues.apache.org/jira/browse/KYLIN-1379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15184780#comment-15184780
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hongbin ma commented on KYLIN-1379:
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i think it's quite comprehensive now, looking forward for the patch:)
> More stable precise count distinct implements after KYLIN-1186
> --------------------------------------------------------------
>
> Key: KYLIN-1379
> URL: https://issues.apache.org/jira/browse/KYLIN-1379
> Project: Kylin
> Issue Type: Improvement
> Components: Job Engine
> Affects Versions: v2.1, v1.3
> Reporter: Yerui Sun
> Assignee: Yerui Sun
>
> After KYLIN-1186, we've gained the ability to count distinct Int type columns
> precisely.
> However, the implements of KYLIN-1186 is not stable, especially in
> 2.x-staging branch.
> The reason is that the measure's maxlength is used to allocate memory in 2.x
> version, and the BitmapMeasure is hardcoded to 8MB in KYLIN-1186, causing OOM
> when cube building.
> To resolve this problem, we have introduce precision on the bitmap measure,
> such as bitmap(100), bitmap(10000), bitmap(1000000), meaning the measure
> could accept 100/10000/1M cardinality at most. This solution should be fine,
> considering the reality, if the count value over 1000000, the hyperloglog
> measure which produce approx. result should be acceptable.
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