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https://issues.apache.org/jira/browse/FLINK-13161?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jark Wu resolved FLINK-13161.
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Resolution: Fixed
Fix Version/s: 1.10.0
Fixed in 1.10.0: 18ace00455aeba00ac459623c46f762900981aec
Fixed in 1.9.0: ca6016c7878245715301e5dfd1743b18106fd2bb
> numBuckets calculate wrong in BinaryHashBucketArea
> --------------------------------------------------
>
> Key: FLINK-13161
> URL: https://issues.apache.org/jira/browse/FLINK-13161
> Project: Flink
> Issue Type: Bug
> Components: Table SQL / Runtime
> Affects Versions: 1.9.0
> Reporter: Louis Xu
> Assignee: Louis Xu
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.9.0, 1.10.0
>
> Attachments: result.log
>
> Time Spent: 40m
> Remaining Estimate: 0h
>
> The original code is:
>
> {code:java}
> int minNumBuckets = (int) Math.ceil((estimatedRowCount / loadFactor /
> NUM_ENTRIES_PER_BUCKET));
> int bucketNumSegs = Math.max(1, Math.min(maxSegs, (minNumBuckets >>>
> table.bucketsPerSegmentBits) +
> ((minNumBuckets & table.bucketsPerSegmentMask) == 0 ? 0 : 1)));
> int numBuckets = MathUtils.roundDownToPowerOf2(bucketNumSegs <<
> table.bucketsPerSegmentBits);
> {code}
> default value: loadFactor=0.75, NUM_ENTRIES_PER_BUCKET=15，maxSegs =
> 33(suppose, only need big than the number which calculated by minBunBuckets)
> We suppose table.bucketsPerSegmentBits = 3, table.bucketsPerSegmentMask =
> 0b111. It means buckets in a segment is 8.
> When set estimatedRowCount loop from 1 to 1000, we will see the result in
> attach file.
> I will take an example:
> {code:java}
> estimatedRowCount: 200, minNumBuckets: 18, bucketNumSegs: 3, numBuckets: 16
> {code}
> We can see it request 3 segment, but only 2 segment needed(16 / 8), left one
> segment wasted.
> And consider the segment is preallocated, it means some segments will never
> used.
>
>
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