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https://issues.apache.org/jira/browse/HIVE-4423?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13739221#comment-13739221
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tagus wang commented on HIVE-4423:
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this has a bug in this:
System.arraycopy(buffer, buffer.length - prefix - 1, buffer, 0, prefix);
it should be
System.arraycopy(buffer, buffer.length - prefix, buffer, 0, prefix);
> Improve RCFile::sync(long) 10x
> ------------------------------
>
> Key: HIVE-4423
> URL: https://issues.apache.org/jira/browse/HIVE-4423
> Project: Hive
> Issue Type: Improvement
> Environment: Ubuntu LXC (1 SSD, 1 disk, 32 gigs of RAM)
> Reporter: Gopal V
> Assignee: Gopal V
> Priority: Minor
> Labels: optimization
> Fix For: 0.12.0
>
> Attachments: HIVE-4423.patch
>
>
> RCFile::sync(long) takes approx ~1 second everytime it gets called because of
> the inner loops in the function.
> From what was observed with HDFS-4710, single byte reads are an order of
> magnitude slower than larger 512 byte buffer reads.
> Even when disk I/O is buffered to this size, there is overhead due to the
> synchronized read() methods in BlockReaderLocal & RemoteBlockReader classes.
> Removing the readByte() calls in RCFile.sync(long) with a readFully(512 byte)
> call will speed this function >10x.
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