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https://issues.apache.org/jira/browse/HBASE-6621?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13438351#comment-13438351
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Lars Hofhansl commented on HBASE-6621:
--------------------------------------
The 2nd observation is that since we also know the keyLength of the KV already
in HFileReaderV2, we might as well pass it to the created KV, further reducing
calls to Bytes.toInt().
> 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
>
>
> 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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