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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9000) Linear reseek in Memstore
Date Tue, 29 Oct 2013 22:05:25 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9000?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13808517#comment-13808517

Lars Hofhansl commented on HBASE-9000:

bq. or let's just do a backport: change the current always "far" behivor into a similar manner
like 0.89-fb's here
What does this entail? reseeking can be useful in many cases, I would not want to generally
go back and disable that.
We should also investigate other data structures for the memstore.
And lastly, in a typical system only a small fraction of the data is in the memstore, the
majority of the data will in HFiles and hence be scanned with StoreFileScanners - if that
would not be the case I would not advocate the use of HBase and suggest something like memcached,
etc, instead.

That all said, opportunistically performing a few nexts and only then issueing a reseek would
be a good addition. Could use MAX_VERSIONS as guidepost here, or make it configurable (there
are usecases where many versions/columns might be kept in HBase).

> 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
> 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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