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https://issues.apache.org/jira/browse/AVRO-939?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13420861#comment-13420861
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Thiruvalluvan M. G. commented on AVRO-939:
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We seem to violate principles of good programming by using something that is
not a part of published API and by accessing private stuff through reflection.
The designers of Unsafe would have thought enough and decided to keep it out of
the published API and declaring the function private.
This is setting a bad precedent. The code will not compile where com.sun.Unsafe
is not available. There is no guarantee that it will be present in any Java
distribution. Neither is there a guarantee that this will be present in Sun's
(Oracle's) distribution in later releases.
Traditionally, Java has done not so great job in defining module boundaries.
(Package-private is of some use, but not really a great facility). Hadoop
community, for example, has taken pains to annotate classes and interfaces to
indicate their accessibility outside the module. Java language is trying to fix
it in Java 8 using Jigsaw. Once that is in, probably this patch won't work.
I'm not sure if marginal performance improvement in a micro-benchmark is a good
enough reason. Do we have evidence that this patch would significantly improve
performance in a real application?
Probably, this debate has happened and settled in the Hadoop community or they
considered it a Guava's internal matter. Since we decided to use "Unsafe"
directly, we should have an opinion. I'm raising it here because even if we
accept this patch, I think, we should acknowledge that we are doing it with
full knowledge of its consequences.
> Java: optimize BinaryData#compareBytes() to use sun.misc.Unsafe when available
> ------------------------------------------------------------------------------
>
> Key: AVRO-939
> URL: https://issues.apache.org/jira/browse/AVRO-939
> Project: Avro
> Issue Type: New Feature
> Components: java
> Affects Versions: 1.7.1
> Reporter: Doug Cutting
> Attachments: AVRO-939-1.patch, AVRO-939-2.patch, AVRO-939-3.patch,
> AVRO-939-4.patch, AVRO-939.patch
>
>
> Google's Guava libraries include an optimized implementation of lexicographic
> byte comparison based on sun.misc.Unsafe that's ~4x faster than the normal
> Java implementation.
> http://hiroshiyamauchi.blogspot.com/2010/08/fast-unsigned-byte-lexicographical.html
> http://www.google.com/codesearch#UKMs0lhE9bg/trunk/src/com/google/common/primitives/UnsignedBytes.java&l=276
> We might similarly optimize BinaryData#compareBytes().
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