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https://issues.apache.org/jira/browse/HIVE-11625?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14709076#comment-14709076
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Cheng Lian commented on HIVE-11625:
-----------------------------------
Sorry, according to the following statements in parquet-format spec
{quote}
The {{key}} field encodes the map's key type. This field must have repetition
{{required}} and must always be present.
{quote}
Map keys written to Parquet must not be null.
Then I think the problem here is that, whether should we silently ignore null
keys when writing a map to a Parquet table like what Hive 0.14.0 does, or throw
an exception (probably a more descriptive one instead of the one mentioned in
the ticket description) like Hive 1.2.1.
> Map instances with null keys are not properly handled for Parquet tables
> ------------------------------------------------------------------------
>
> Key: HIVE-11625
> URL: https://issues.apache.org/jira/browse/HIVE-11625
> Project: Hive
> Issue Type: Sub-task
> Affects Versions: 0.14.0, 0.13.1, 1.0.1, 1.1.1, 1.2.1
> Reporter: Cheng Lian
>
> Hive allows maps with null keys:
> {code:sql}
> hive> select map(null, 'foo', 1, 'bar', null, 'baz');
> {null:"baz",1:"bar"}
> {code}
> However, when written into Parquet tables, map entries with null as keys are
> either dropped or cause exceptions. Below is the result of Hive 0.14.0 and
> 0.13.1:
> {code:sql}
> hive> CREATE TABLE map_test STORED AS PARQUET
> > AS SELECT MAP(null, 'foo', 1, 'bar', null, 'baz');
> ...
> hive> SELECT * from map_test;
> {1:"bar"}
> {code}
> And Hive 1.2.1 throws exception:
> {noformat}
> java.lang.RuntimeException: org.apache.hadoop.hive.ql.metadata.HiveException:
> Hive Runtime Error while processing writable (null)
> at org.apache.hadoop.hive.ql.exec.mr.ExecMapper.map(ExecMapper.java:172)
> at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:50)
> at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:430)
> at org.apache.hadoop.mapred.MapTask.run(MapTask.java:366)
> at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
> at java.security.AccessController.doPrivileged(Native Method)
> at javax.security.auth.Subject.doAs(Subject.java:422)
> at
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1190)
> at org.apache.hadoop.mapred.Child.main(Child.java:249)
> Caused by: org.apache.hadoop.hive.ql.metadata.HiveException: Hive Runtime
> Error while processing writable (null)
> at
> org.apache.hadoop.hive.ql.exec.MapOperator.process(MapOperator.java:516)
> at org.apache.hadoop.hive.ql.exec.mr.ExecMapper.map(ExecMapper.java:163)
> ... 8 more
> Caused by: java.lang.RuntimeException: Parquet record is malformed: empty
> fields are illegal, the field should be ommited completely instead
> at
> org.apache.hadoop.hive.ql.io.parquet.write.DataWritableWriter.write(DataWritableWriter.java:64)
> at
> org.apache.hadoop.hive.ql.io.parquet.write.DataWritableWriteSupport.write(DataWritableWriteSupport.java:59)
> at
> org.apache.hadoop.hive.ql.io.parquet.write.DataWritableWriteSupport.write(DataWritableWriteSupport.java:31)
> at
> parquet.hadoop.InternalParquetRecordWriter.write(InternalParquetRecordWriter.java:121)
> at
> parquet.hadoop.ParquetRecordWriter.write(ParquetRecordWriter.java:123)
> at parquet.hadoop.ParquetRecordWriter.write(ParquetRecordWriter.java:42)
> at
> org.apache.hadoop.hive.ql.io.parquet.write.ParquetRecordWriterWrapper.write(ParquetRecordWriterWrapper.java:111)
> at
> org.apache.hadoop.hive.ql.io.parquet.write.ParquetRecordWriterWrapper.write(ParquetRecordWriterWrapper.java:124)
> at
> org.apache.hadoop.hive.ql.exec.FileSinkOperator.process(FileSinkOperator.java:753)
> at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:837)
> at
> org.apache.hadoop.hive.ql.exec.SelectOperator.process(SelectOperator.java:88)
> at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:837)
> at
> org.apache.hadoop.hive.ql.exec.TableScanOperator.process(TableScanOperator.java:97)
> at
> org.apache.hadoop.hive.ql.exec.MapOperator$MapOpCtx.forward(MapOperator.java:162)
> at
> org.apache.hadoop.hive.ql.exec.MapOperator.process(MapOperator.java:508)
> ... 9 more
> Caused by: parquet.io.ParquetEncodingException: empty fields are illegal, the
> field should be ommited completely instead
> at
> parquet.io.MessageColumnIO$MessageColumnIORecordConsumer.endField(MessageColumnIO.java:244)
> at
> org.apache.hadoop.hive.ql.io.parquet.write.DataWritableWriter.writeMap(DataWritableWriter.java:228)
> at
> org.apache.hadoop.hive.ql.io.parquet.write.DataWritableWriter.writeValue(DataWritableWriter.java:116)
> at
> org.apache.hadoop.hive.ql.io.parquet.write.DataWritableWriter.writeGroupFields(DataWritableWriter.java:89)
> at
> org.apache.hadoop.hive.ql.io.parquet.write.DataWritableWriter.write(DataWritableWriter.java:60)
> ... 23 more
> java.lang.RuntimeException: org.apache.hadoop.hive.ql.metadata.HiveException:
> Hive Runtime Error while processing writable (null)
> at org.apache.hadoop.hive.ql.exec.mr.ExecMapper.map(ExecMapper.java:172)
> at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:50)
> at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:430)
> at org.apache.hadoop.mapred.MapTask.run(MapTask.java:366)
> at org.apache.hadoop.mapred.Child$4.run(Child.java:255)
> at java.security.AccessController.doPrivileged(Native Method)
> at javax.security.auth.Subject.doAs(Subject.java:422)
> at
> org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1190)
> at org.apache.hadoop.mapred.Child.main(Child.java:249)
> Caused by: org.apache.hadoop.hive.ql.metadata.HiveException: Hive Runtime
> Error while processing writable (null)
> at
> org.apache.hadoop.hive.ql.exec.MapOperator.process(MapOperator.java:516)
> at org.apache.hadoop.hive.ql.exec.mr.ExecMapper.map(ExecMapper.java:163)
> ... 8 more
> Caused by: java.lang.RuntimeException: Parquet record is malformed: empty
> fields are illegal, the field should be ommited completely instead
> at
> org.apache.hadoop.hive.ql.io.parquet.write.DataWritableWriter.write(DataWritableWriter.java:64)
> at
> org.apache.hadoop.hive.ql.io.parquet.write.DataWritableWriteSupport.write(DataWritableWriteSupport.java:59)
> at
> org.apache.hadoop.hive.ql.io.parquet.write.DataWritableWriteSupport.write(DataWritableWriteSupport.java:31)
> at
> parquet.hadoop.InternalParquetRecordWriter.write(InternalParquetRecordWriter.java:121)
> at
> parquet.hadoop.ParquetRecordWriter.write(ParquetRecordWriter.java:123)
> at parquet.hadoop.ParquetRecordWriter.write(ParquetRecordWriter.java:42)
> at
> org.apache.hadoop.hive.ql.io.parquet.write.ParquetRecordWriterWrapper.write(ParquetRecordWriterWrapper.java:111)
> at
> org.apache.hadoop.hive.ql.io.parquet.write.ParquetRecordWriterWrapper.write(ParquetRecordWriterWrapper.java:124)
> at
> org.apache.hadoop.hive.ql.exec.FileSinkOperator.process(FileSinkOperator.java:753)
> at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:837)
> at
> org.apache.hadoop.hive.ql.exec.SelectOperator.process(SelectOperator.java:88)
> at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:837)
> at
> org.apache.hadoop.hive.ql.exec.TableScanOperator.process(TableScanOperator.java:97)
> at
> org.apache.hadoop.hive.ql.exec.MapOperator$MapOpCtx.forward(MapOperator.java:162)
> at
> org.apache.hadoop.hive.ql.exec.MapOperator.process(MapOperator.java:508)
> ... 9 more
> Caused by: parquet.io.ParquetEncodingException: empty fields are illegal, the
> field should be ommited completely instead
> at
> parquet.io.MessageColumnIO$MessageColumnIORecordConsumer.endField(MessageColumnIO.java:244)
> at
> org.apache.hadoop.hive.ql.io.parquet.write.DataWritableWriter.writeMap(DataWritableWriter.java:228)
> at
> org.apache.hadoop.hive.ql.io.parquet.write.DataWritableWriter.writeValue(DataWritableWriter.java:116)
> at
> org.apache.hadoop.hive.ql.io.parquet.write.DataWritableWriter.writeGroupFields(DataWritableWriter.java:89)
> at
> org.apache.hadoop.hive.ql.io.parquet.write.DataWritableWriter.write(DataWritableWriter.java:60)
> ... 23 more
> {noformat}
> The problematic method is
> [{{DataWritableWriter.writeMap()}}|https://github.com/apache/hive/blob/release-1.2.1/ql/src/java/org/apache/hadoop/hive/ql/io/parquet/write/DataWritableWriter.java#L223-L237].
> Although the key value entry is not null, either key or value can be null.
> And null keys are not properly handled.
> Changing [these 3
> lines|https://github.com/apache/hive/blob/release-1.2.1/ql/src/java/org/apache/hadoop/hive/ql/io/parquet/write/DataWritableWriter.java#L226-L228]
> to
> {code:java}
> if (keyElement != null) {
> recordConsumer.startField(keyName, 0);
> writeValue(keyElement, keyInspector, keyType);
> recordConsumer.endField(keyName, 0);
> }
> {code}
> should fix this issue.
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