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From "Chao Shi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9000) Linear reseek in Memstore
Date Tue, 05 Nov 2013 06:00:25 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9000?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13813676#comment-13813676

Chao Shi commented on HBASE-9000:

Hi [~zjushch],

bq. How to decide the config value?
I think most users should use the default value. This patch optimize performance on scenario
that reseek on MemStore is the bottleneck, for example, scan with a filter that skips a lot
of KVs. In this case, you need to tweak this value and make sure linear seeks happen rather
than reseeks (i.e.. set this value to be greater than #versions in MemStore, if you are using
SEEK_NEXT_COL). As most users don't have much versions per KV in their MemStore, I think the
default value should play well.

bq. IMPO, the new code in MemStore seems not friendly
Could you please explain more on what can be improved?

> Linear reseek in Memstore
> -------------------------
>                 Key: HBASE-9000
>                 URL: https://issues.apache.org/jira/browse/HBASE-9000
>             Project: HBase
>          Issue Type: Improvement
>    Affects Versions: 0.89-fb
>            Reporter: Shane Hogan
>            Priority: Minor
>             Fix For: 0.89-fb
>         Attachments: hbase-9000-benchmark-program.patch, hbase-9000-port-fb.patch, hbase-9000.patch
> This is to address the linear reseek in MemStoreScanner. Currently reseek iterates over
the kvset and the snapshot linearly by just calling next repeatedly. The new solution is to
do this linear seek up to a configurable maximum amount of times then if the seek is not yet
complete fall back to logarithmic seek.

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