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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6621) Reduce calls to Bytes.toInt
Date Tue, 21 Aug 2012 06:48:38 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6621?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13438491#comment-13438491
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Lars Hofhansl commented on HBASE-6621:
--------------------------------------

Using a qualifier filter that just filters each qualifier (to eliminate variance from the
network and the driver client), I see 7.30ms vs 7.65ms per, a ~4% improvement.

This was a repeated get of a row with 200.000 columns, all of which are filtered by a QualifierFilter
(i.e. all KVs are read at the server, but none are returned to the client).

                
> Reduce calls to Bytes.toInt
> ---------------------------
>
>                 Key: HBASE-6621
>                 URL: https://issues.apache.org/jira/browse/HBASE-6621
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>            Priority: Minor
>             Fix For: 0.96.0, 0.94.2
>
>         Attachments: 6621-0.96.txt, 6621-0.96-v2.txt, 6621-0.96-v3.txt, 6621-0.96-v4.txt
>
>
> Bytes.toInt shows up quite often in a profiler run.
> It turns out that one source is HFileReaderV2$ScannerV2.getKeyValue().
> Notice that we call the KeyValue(byte[], int) constructor, which forces the constructor
to determine its size by reading some of the header information and calculate the size. In
this case, however, we already know the size (from the call to readKeyValueLen), so we could
just use that.
> In the extreme case of 10000's of columns this noticeably reduces CPU. 

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