[jira] [Created] (HIVE-8419) Hive doesn't properly write NULL values in Parquet files when the type is struct<...>.

["Frédéric TERRAZZONI (JIRA)" <ji...@apache.org>]

Frédéric TERRAZZONI created HIVE-8419:
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             Summary: Hive doesn't properly write NULL values in Parquet files when the type is struct<...>.
                 Key: HIVE-8419
                 URL: https://issues.apache.org/jira/browse/HIVE-8419
             Project: Hive
          Issue Type: Bug
          Components: File Formats
    Affects Versions: 0.13.1
            Reporter: Frédéric TERRAZZONI


Hive doesn't seem to be able to write NULL values in a column of type "struct". Instead, it replaces them by empty objects (= non NULL objects containing only NULL values).

Here is a short example demonstrating the issue. We start with a small Avro table "avro_table".

{code} SELECT  * from avro_table {code}
|| mycol ||
|| struct<field1:string,field2:double> || 
| {"field1":"blabla","field2":1.0} | 
 | {"field1":"blabla","field2":2.0} | 
 | NULL | 
 | {"field1":"blabla","field2":4.0} | 
 | {"field1":"blabla","field2":5.0} | 


As you can see here, the third row contains a NULL cell. Then, let's copy it using Hive (INSERT OVERWRITE ...) into a Parquet table named "parquet_table". 

Finally, when you try to display it:
{code} SELECT  * from parquet_table {code}
|| mycol ||
|| struct<field1:string,field2:double> || 
| {"field1":"blabla","field2":1.0} | 
 | {"field1":"blabla","field2":2.0}  | 
 | {"field1":null,"field2":null} | 
 | {"field1":"blabla","field2":4.0} | 
 | {"field1":"blabla","field2":5.0} | 


I tried to generate a (correct) Parquet file using our software (Dataiku), and Hive had no problem reading null values, even when the column type was "struct". 

Consequently, I suspect the bug to be located in the Parquet writer code.

This bug also recursively propagates to nested types. For instance a NULL cell of type {code} struct<field1:struct<field3:string>,field2:double> {code} will be become {code} {"field1":{"field3":null},"field2":null} {code} when written in a Parquet file.



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