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https://issues.apache.org/jira/browse/CASSANDRA-2850?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13059239#comment-13059239
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David Allsopp commented on CASSANDRA-2850:
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Just a note as to why might matter (in the absence of hard profiling data) - 
hexToBytes() is called in a lot of places in the code, and is sometimes called 
on the entire column value.

A column value of 10MB takes over 750ms to convert on my machine (180ms with 
the patch), so it's significant load - and column values go up to 2GB 
(extrapolating linearly, 2GB could take over 2 minutes to convert, assuming 
you've got the spare RAM!).



> Converting bytes to hex string is unnecessarily slow
> ----------------------------------------------------
>
>                 Key: CASSANDRA-2850
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2850
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 0.7.6, 0.8.1
>            Reporter: David Allsopp
>            Priority: Minor
>             Fix For: 0.8.2
>
>         Attachments: BytesToHexBenchmark.java, cassandra-2850.diff
>
>
> ByteBufferUtil.bytesToHex() is unnecessarily slow - it doesn't pre-size the 
> StringBuilder (so several re-sizes will be needed behind the scenes) and it 
> makes quite a few method calls per byte.
> (OK, this may be a premature optimisation, but I couldn't resist, and it's a 
> small change)
> Will attach patch shortly that speeds it up by about x3, plus benchmarking 
> test.

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