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https://issues.apache.org/jira/browse/HBASE-17765?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15907030#comment-15907030
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Edward Bortnikov commented on HBASE-17765:
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Merge means that only the index data is restructured. We create a larger
segment with one index - but no data is copied. Also, we avoid using the SQM
scan (more expensive), so duplicate data versions are not eliminated. Bottom
line - (1) the overhead and the space savings are both between BASIC and EAGER,
and (2) the tail read latency problem is solved.
We'll be publishing the perf results shortly. Following that, let's
collectively decide whether MERGE should be a level between BASIC and EAGER, or
maybe just become the new BASIC, for simplicity.
Thanks.
> Reviving the merge possibility in the CompactingMemStore
> --------------------------------------------------------
>
> Key: HBASE-17765
> URL: https://issues.apache.org/jira/browse/HBASE-17765
> Project: HBase
> Issue Type: Sub-task
> Reporter: Anastasia Braginsky
> Assignee: Anastasia Braginsky
> Fix For: 2.0.0
>
> Attachments: HBASE-17765-V01.patch
>
>
> According to the new performance results presented in the HBASE-16417 we see
> that the read latency of the 90th percentile of the BASIC policy is too big
> due to the need to traverse through too many segments in the pipeline. In
> this JIRA we correct the bug in the merge sizing calculations and allow
> pipeline size threshold to be a configurable parameter.
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