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From "jiraposter@reviews.apache.org (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4434) Don't do HFile Scanner next() unless the next KV is needed:
Date Fri, 23 Sep 2011 05:15:28 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4434?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13113160#comment-13113160
] 

jiraposter@reviews.apache.org commented on HBASE-4434:
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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/2034/
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Review request for Michael Stack, Jonathan Gray and Mikhail Bautin.


Summary
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The increase in blocks read in one sub-test case is due to HBASE-4466, which should be fixed
soon. It is primarily an accounting issue, not an extra cache miss.


This addresses bug HBASE-4434.
    https://issues.apache.org/jira/browse/HBASE-4434


Diffs
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  http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/regionserver/StoreFileScanner.java
1174514 
  http://svn.apache.org/repos/asf/hbase/trunk/src/test/java/org/apache/hadoop/hbase/regionserver/TestBlocksRead.java
1174514 

Diff: https://reviews.apache.org/r/2034/diff


Testing
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Ran TestBlocksRead. Will run the entire suite as well. On our 89 based internal branch, the
tests passed without any issues.


Thanks,

Kannan



> Don't do HFile Scanner next() unless the next KV is needed:
> -----------------------------------------------------------
>
>                 Key: HBASE-4434
>                 URL: https://issues.apache.org/jira/browse/HBASE-4434
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Kannan Muthukkaruppan
>            Assignee: Kannan Muthukkaruppan
>
> When a seek/reseek is done on StoreFileScanner, in addition to setting the current KV,
it also does a HFileScanner level next() ahead of time even if the next KV is never actually
required. This inefficiency can potentially result in additional disk seeks and sub-optimal
use of the block cache (primarily for cases where the KVs are large and each occupies an HFile
block of its own).

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