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

["Sergio Peña (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-8419?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14190410#comment-14190410 ] 

Sergio Peña commented on HIVE-8419:
-----------------------------------

Hi [~Akryus]

Could you attach the avro file (data + schema)? 

Btw, This could have been fixed on HIVE-8359 where it now accepts null values on array elements.

> 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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