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From "jiraposter@reviews.apache.org (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4434) seek optimization: don't do eager HFile Scanner next() unless the next KV is needed
Date Fri, 23 Sep 2011 19:51:28 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4434?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13113701#comment-13113701
] 

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/#review2056
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Ship it!


- Michael


On 2011-09-23 05:13:36, Kannan Muthukkaruppan wrote:
bq.  
bq.  -----------------------------------------------------------
bq.  This is an automatically generated e-mail. To reply, visit:
bq.  https://reviews.apache.org/r/2034/
bq.  -----------------------------------------------------------
bq.  
bq.  (Updated 2011-09-23 05:13:36)
bq.  
bq.  
bq.  Review request for Michael Stack, Jonathan Gray and Mikhail Bautin.
bq.  
bq.  
bq.  Summary
bq.  -------
bq.  
bq.  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.
bq.  
bq.  
bq.  This addresses bug HBASE-4434.
bq.      https://issues.apache.org/jira/browse/HBASE-4434
bq.  
bq.  
bq.  Diffs
bq.  -----
bq.  
bq.    http://svn.apache.org/repos/asf/hbase/trunk/src/main/java/org/apache/hadoop/hbase/regionserver/StoreFileScanner.java
1174514 
bq.    http://svn.apache.org/repos/asf/hbase/trunk/src/test/java/org/apache/hadoop/hbase/regionserver/TestBlocksRead.java
1174514 
bq.  
bq.  Diff: https://reviews.apache.org/r/2034/diff
bq.  
bq.  
bq.  Testing
bq.  -------
bq.  
bq.  Ran TestBlocksRead. Will run the entire suite as well. On our 89 based internal branch,
the tests passed without any issues.
bq.  
bq.  
bq.  Thanks,
bq.  
bq.  Kannan
bq.  
bq.



> seek optimization: don't do eager 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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