[jira] [Resolved] (SPARK-4781) Column values become all NULL after doing ALTER TABLE CHANGE for renaming column names (Parquet external table in HiveContext)

["Michael Armbrust (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-4781?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Michael Armbrust resolved SPARK-4781.
-------------------------------------
    Resolution: Won't Fix

This is by design, the alter table command in hive only changes metadata.  From the HiveQL guide:

{code}
The column change command will only modify Hive's metadata, and will not modify data. Users should make sure the actual data layout of the table/partition conforms with the metadata definition.
{code}

If you want to change column names for parquet data you would need to create a VIEW on the base table.

> Column values become all NULL after doing ALTER TABLE CHANGE for renaming column names (Parquet external table in HiveContext)
> ------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: SPARK-4781
>                 URL: https://issues.apache.org/jira/browse/SPARK-4781
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 1.2.0, 1.3.0, 1.2.1
>            Reporter: Jianshi Huang
>
> I have a table say created like follows:
> {code}
> CREATE EXTERNAL TABLE pmt (
>   `sorted::cre_ts` string
> )
> STORED AS PARQUET
> LOCATION '...'
> {code}
> And I renamed the column from sorted::cre_ts to cre_ts by doing:
> {code}
> ALTER TABLE pmt CHANGE `sorted::cre_ts` cre_ts string
> {code}
> After renaming the column, the values in the column become all NULLs.
> {noformat}
> Before renaming:
> scala> sql("select `sorted::cre_ts` from pmt limit 1").collect
> res12: Array[org.apache.spark.sql.Row] = Array([12/02/2014 07:38:54])
> Execute renaming:
> scala> sql("alter table pmt change `sorted::cre_ts` cre_ts string")
> res13: org.apache.spark.sql.SchemaRDD =
> SchemaRDD[972] at RDD at SchemaRDD.scala:108
> == Query Plan ==
> <Native command: executed by Hive>
> After renaming:
> scala> sql("select cre_ts from pmt limit 1").collect
> res16: Array[org.apache.spark.sql.Row] = Array([null])
> {noformat}
> Jianshi



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