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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-17185) Purge the seek of the next block reading HFileBlocks
Date Tue, 29 Nov 2016 23:53:59 GMT

     [ https://issues.apache.org/jira/browse/HBASE-17185?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

stack updated HBASE-17185:
--------------------------
    Labels: beginner  (was: )

> Purge the seek of the next block reading HFileBlocks
> ----------------------------------------------------
>
>                 Key: HBASE-17185
>                 URL: https://issues.apache.org/jira/browse/HBASE-17185
>             Project: HBase
>          Issue Type: Improvement
>          Components: HFile
>    Affects Versions: 2.0.0
>            Reporter: stack
>            Assignee: stack
>            Priority: Minor
>              Labels: beginner
>             Fix For: 2.0.0
>
>         Attachments: HBASE-17185.master.001.patch, HBASE-17185.patch
>
>
> When we read HFileBlocks, we read the asked-for block AND the next block's header which
we add to a cache (see HBASE-17072). We do this extra read to get the next block's length
purportedly. This seek of the next block's header complicates the HFileBlock construction
(not to mind other consequences -- again see HBASE-17072).
> Study done in HBASE-17072 shows that we normally do not need this extra read of the next
block's header. In the usual case, the length of the block is gotten from the hfile index.
> A simplification of block reading can be done purging this extra header read. We can
also save some space in cache.



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