Parquet/parquet-mr — pull request #337 by tongjiechen (2014-03-27 03:19:20+00:00)
Title:  issue #324, move ParquetStringInspector to org.apache.hadoop.hive.serde...

When a hive table's SerDe is ParquetHiveSerDe, while some partitions are of other SerDe, AND if this table has string column[s], hive generates confusing error message:

"Failed with exception java.io.IOException:java.lang.ClassCastException: parquet.hive.serde.primitive.ParquetStringInspector cannot be cast to org.apache.hadoop.hive.serde2.objectinspector.primitive.SettableTimestampObjectInspector"

This is confusing because timestamp is mentioned even if it is not been used by the table. The reason is when there is SerDe difference between table and partition, hive tries to convert objectinspector of two SerDes. ParquetHiveSerDe's object inspector for string type is ParquetStringInspector (newly introduced), neither a subclass of WritableStringObjectInspector nor JavaStringObjectInspector, which ObjectInspectorConverters expect for string category objector inspector. There is no break statement in STRING case statement, hence the following TIMESTAMP case statement is executed, generating confusing error message.

see more details here:
https://github.com/Parquet/parquet-mr/issues/324

To fix that it is relatively easy, just make ParquetStringInspector subclass of JavaStringObjectInspector instead of AbstractPrimitiveJavaObjectInspector. But because constructor of class JavaStringObjectInspector is package scope instead of public or protected, we would need to move ParquetStringInspector to the same package with JavaStringObjectInspector.

Also ArrayWritableObjectInspector's setStructFieldData needs to also accept List data, since the corresponding setStructFieldData and create methods return a list. This is also needed when table SerDe is ParquetHiveSerDe, and partition SerDe is something else.