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From paul-rogers <...@git.apache.org>
Subject [GitHub] drill issue #707: DRILL-5157: Multiple Snappy versions on class path
Date Tue, 21 Feb 2017 01:41:19 GMT
Github user paul-rogers commented on the issue:

    https://github.com/apache/drill/pull/707
  
    @bitblender - The general problem with jar dependencies is that each Maven project depends
on a different version of library x. However, the JVM can load only one version (if everything
goes into the global class loader, as in Drill.) So, we have to exclude all the random versions
to ensure that a single version is included. In general, we must assume that newer versions
are compatible with old versions. Else, we're in a world of hurt. (Guava is a good example:
Guava removes symbols that used to exist, so that a newer version is not usable by code that
needs an older one.)
    
    All we can do is test to ensure that 1) we have a single version of the library, and 2)
everything works with that version. The nature of this PR is that we violated item 1: we have
multiple snappy versions. The one that gets used depends on how the class path is formed:
one goes first in production, a different one in the IDE.


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