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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-10322) skipBytes is used extensively, but is slow
Date Wed, 16 Sep 2015 11:52:45 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-10322?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14747365#comment-14747365
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Benedict commented on CASSANDRA-10322:
--------------------------------------

For information, [this graph|http://cstar.datastax.com/graph?stats=a63084c2-5c4e-11e5-9b80-42010af0688f&metric=op_rate&operation=3_user&smoothing=1&show_aggregates=true&xmin=0&xmax=174.24&ymin=0&ymax=110044]
demonstrates a useful bump from this patch (the purple line). Of course, still not up to 2.2
speed, and 2.2 could also have the optimisation if we wanted to backport it (which perhaps
we should, so we have a good yardstick to continue to measure from).

> skipBytes is used extensively, but is slow
> ------------------------------------------
>
>                 Key: CASSANDRA-10322
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-10322
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Benedict
>            Assignee: Benedict
>            Priority: Trivial
>             Fix For: 3.0.x
>
>
> We skip a great deal to avoid materializing data. Ironically, however, skipping is just
as (perhaps more) expensive, as it allocates a temporary array of the size of the number of
bytes we want to skip.
> This trivial patch implements {{skipBytes}} more efficiently, and simplifies {{FileUtils.skipBytesFully}}



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