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https://issues.apache.org/jira/browse/HBASE-8012?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13596913#comment-13596913
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Raymond Liu commented on HBASE-8012:
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[~stack] : I think this patch won't do any performance benefit at present. It
just make reseekto 's behavior more correct and simulate the behavior of
seekto. it doesn't need to have extra place to keep tracking whether can we do
reseek or not. reseek it self should always working correctly. ( since seek can
why reseek should not). And I don't see downsides possibility, since the check
need to be done anyway, if not inside reseek than before call reseek.
While, as I mentioned before, If we are allowed to change the seekto and
reseekto 's behavior, we can push this check into even lower level. at that
case, could have micro level performance benefit. Since in some code branch, it
won't need to be checked at all.
> Reseek should position to the beginning of file for the first time it is
> invoked with a KV smaller than the first KV in file
> ----------------------------------------------------------------------------------------------------------------------------
>
> Key: HBASE-8012
> URL: https://issues.apache.org/jira/browse/HBASE-8012
> Project: HBase
> Issue Type: Bug
> Components: regionserver
> Affects Versions: 0.94.5
> Reporter: Raymond Liu
> Assignee: Raymond Liu
> Priority: Minor
> Fix For: 0.98.0
>
> Attachments: HBASE-8012.patch, HBASE-8012.patch, HBASE-8012_v2.patch
>
>
> The storeFileScanner's seekAtOrAfter method will position at the beginning of
> the file when the passed KV is smaller than first KV in file. While for
> reseekAtOrAfter, I think it should also do the same thing when it is the
> first time it been seeked. originally, this is workaround by adding a
> isReseekable property in StoreFileScanner, and is checked upon each
> enforceSeek(), if it is not seeked before, it will go with seek approaching
> instead of reseek approaching. While why not make reseekAtOrAfter working
> correctly for the first time it been reseek (also never been seek before),
> since the file is never seeked before, so position it at the beginning of the
> file don't break the idea of "reseek", say never rewind.
> It will save the effort for HBASE-8001, with this fixed, it won't need to
> check isReseekable any more.
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