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https://issues.apache.org/jira/browse/HIVE-6389?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13917697#comment-13917697
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Mithun Radhakrishnan commented on HIVE-6389:
--------------------------------------------
Hey, Ashutosh. As a matter of fact, this stack trace is the result of running
"select mymap[ 'xyz' ] from mytable", if mytable has null values for mymap.
Although the bug is in the LazyBinaryObjectInspector for Maps, it doesn't
manifest at the time of read.
The reason you're seeing a fail in LazySimpleSerde is because the results of
the query are being serialized into String (i.e. to console).
The LazyBinaryMapOI returns -1 for NULL maps. WHen the LazySimpleSerde attempts
to convert this Integer into Text, we get this bad-cast exception. The OI
should have been returning nulls for null objects, like the ColumnarSerDe does.
The way I tested this is:
1. create table mytable_text( mymap map<string, string> ) stored as textfile;
2. echo "\N\n\N\n\N" > /tmp/mytable.txt && hdfs dfs -copyFromLocal
/tmp/mytable.txt /user/hive/warehouse/mytable_text
3. create table mytable_rcfile( mymap map<string, string> ) stored as rcfile;
-- LazyBinaryColumnarSerDe
4. insert overwrite table mytable_rcfile select mymap from mytable_text;
5. select mymap['blah'] from mytable_rcfile;
Steps 1-4 is simply to insert a null-map into an RCFile-based table.
Step 5 causes the null-map to be returned by LazyBinaryMapOI as '-1', etc.
This patch brings LazyBinaryMapOI's behaviour in line with LazyMapOI. (This is
likely just a copy-paste error, from getMapSize().
> LazyBinaryColumnarSerDe-based RCFile tables break when looking up elements in
> null-maps.
> ----------------------------------------------------------------------------------------
>
> Key: HIVE-6389
> URL: https://issues.apache.org/jira/browse/HIVE-6389
> Project: Hive
> Issue Type: Bug
> Components: Serializers/Deserializers
> Affects Versions: 0.10.0, 0.11.0, 0.12.0, 0.13.0
> Reporter: Mithun Radhakrishnan
> Assignee: Mithun Radhakrishnan
> Attachments: Hive-6389.patch
>
>
> RCFile tables that use the LazyBinaryColumnarSerDe don't seem to handle
> look-ups into map-columns when the value of the column is null.
> When an RCFile table is created with LazyBinaryColumnarSerDe (as is default
> in 0.12), and queried as follows:
> {code}
> select mymap['1024'] from mytable;
> {code}
> and if the mymap column has nulls, then one is treated to the following
> guttural utterance:
> {code}
> 2014-02-05 21:50:25,050 FATAL mr.ExecMapper (ExecMapper.java:map(194)) -
> org.apache.hadoop.hive.ql.metadata.HiveException: Hive Runtime Error while
> processing row {"id":null,"mymap":null,"isnull":null}
> at org.apache.hadoop.hive.ql.exec.MapOperator.process(MapOperator.java:534)
> at org.apache.hadoop.hive.ql.exec.mr.ExecMapper.map(ExecMapper.java:177)
> at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:54)
> at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:429)
> at org.apache.hadoop.mapred.MapTask.run(MapTask.java:341)
> at
> org.apache.hadoop.mapred.LocalJobRunner$Job$MapTaskRunnable.run(LocalJobRunner.java:235)
> at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
> at java.util.concurrent.FutureTask.run(FutureTask.java:262)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
> at java.lang.Thread.run(Thread.java:744)
> Caused by: java.lang.ClassCastException: java.lang.Integer cannot be cast to
> org.apache.hadoop.io.Text
> at
> org.apache.hadoop.hive.serde2.objectinspector.primitive.WritableStringObjectInspector.getPrimitiveWritableObject(WritableStringObjectInspector.java:41)
> at
> org.apache.hadoop.hive.serde2.lazy.LazyUtils.writePrimitiveUTF8(LazyUtils.java:226)
> at
> org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe.serialize(LazySimpleSerDe.java:486)
> at
> org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe.serializeField(LazySimpleSerDe.java:439)
> at
> org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe.serialize(LazySimpleSerDe.java:423)
> at
> org.apache.hadoop.hive.ql.exec.FileSinkOperator.processOp(FileSinkOperator.java:560)
> at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:790)
> at
> org.apache.hadoop.hive.ql.exec.SelectOperator.processOp(SelectOperator.java:87)
> at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:790)
> at
> org.apache.hadoop.hive.ql.exec.TableScanOperator.processOp(TableScanOperator.java:92)
> at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:790)
> at org.apache.hadoop.hive.ql.exec.MapOperator.process(MapOperator.java:524)
> ... 10 more
> {code}
> A patch is on the way, but the short of it is that the LazyBinaryMapOI needs
> to return nulls if either the map or the lookup-key is null.
> This is handled correctly for Text data, and for RCFiles using ColumnarSerDe.
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