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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/27117/
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(Updated Oct. 24, 2014, 4:51 p.m.)
Review request for hive and Xuefu Zhang.
Changes
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Thanks Xuefu for the comments. I've updated my patch.
Bugs: HIVE-8457
https://issues.apache.org/jira/browse/HIVE-8457
Repository: hive-git
Description
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Currently, on the Spark branch, each thread it is bound with a thread-local
IOContext, which gets initialized when we generates an input HadoopRDD, and
later used in MapOperator, FilterOperator, etc.
And, given the introduction of HIVE-8118, we may have multiple downstream RDDs
that share the same input HadoopRDD, and we would like to have the HadoopRDD to
be cached, to avoid scanning the same table multiple times. A typical case
would be like the following:
inputRDD inputRDD
| |
MT_11 MT_12
| |
RT_1 RT_2
Here, MT_11 and MT_12 are MapTran from a splitted MapWork,
and RT_1 and RT_2 are two ReduceTran. Note that, this example is simplified, as
we may also have ShuffleTran between MapTran and ReduceTran.
When multiple Spark threads are running, MT_11 may be executed first, and it
will ask for an iterator from the HadoopRDD will trigger the creation of the
iterator, which in turn triggers the initialization of the IOContext associated
with that particular thread.
Now, the problem is: before MT_12 starts executing, it will also ask for an
iterator from the
HadoopRDD, and since the RDD is already cached, instead of creating a new
iterator, it will just fetch it from the cached result. However, this will skip
the initialization of the IOContext associated with this particular thread.
And, when MT_12 starts executing, it will try to initialize the MapOperator,
but since the IOContext is not initialized, this will fail miserably.
Diffs (updated)
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ql/src/java/org/apache/hadoop/hive/ql/exec/spark/SparkMapRecordHandler.java
20ea977
ql/src/java/org/apache/hadoop/hive/ql/exec/spark/SparkPlanGenerator.java
00a6f3d
ql/src/java/org/apache/hadoop/hive/ql/exec/spark/SparkUtilities.java 4de3ad4
ql/src/java/org/apache/hadoop/hive/ql/io/HiveContextAwareRecordReader.java
58e1ceb
ql/src/java/org/apache/hadoop/hive/ql/io/IOContext.java 5fb3b13
Diff: https://reviews.apache.org/r/27117/diff/
Testing
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All multi-insertion related tests are passing on my local machine.
Thanks,
Chao Sun
