Github user srowen commented on a diff in the pull request:
https://github.com/apache/spark/pull/7929#discussion_r36273851
--- Diff:
sql/hive/src/main/scala/org/apache/spark/sql/hive/client/ClientWrapper.scala ---
@@ -62,6 +64,52 @@ private[hive] class ClientWrapper(
extends ClientInterface
with Logging {
+ overrideHadoopShims()
+
+ // !! HACK ALERT !!
+ //
+ // This method is a surgical fix for Hadoop version 2.0.0-mr1-cdh4.1.1,
which is used by Spark EC2
+ // scripts. We should remove this after upgrading Spark EC2 scripts to
some more recent Hadoop
+ // version in the future.
+ //
+ // Internally, Hive `ShimLoader` tries to load different versions of
Hadoop shims by checking
+ // version information gathered from Hadoop jar files. If the major
version number is 1,
+ // `Hadoop20SShims` will be loaded. Otherwise, if the major version
number is 2, `Hadoop23Shims`
+ // will be chosen.
+ //
+ // However, part of APIs in Hadoop 2.0.x and 2.1.x versions were in flux
due to historical
+ // reasons. So 2.0.0-mr1-cdh4.1.1 is actually more Hadoop-1-like and
should be used together with
--- End diff --
My gut is that there's much more reason to believe other 2.0.x builds work
the same way. The method in question here (as far as I understand) never
appeared in any 2.0.x release. Occam's razor would suggest not special casing
here. I don't know that CDH4 is the only relevant 2.0.x release; certainly
upstream Apache Hadoop made a number of 2.0.x releases that this change would
(again as far as I understand) affect as well and would be left out.
At the least, let's get the comment updated. Also, `mr1` really isn't
relevant. I would not special-case cdh4, since the comments will say it's not
special.
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