question Re: Hive Alter column type in Archives of Support Questions (Read Only)

Hive Alter column type

ahmed_missaoui_ — Fri, 29 Jan 2016 21:18:18 GMT

hello,

I am using hive 1.2.1.

I executed the following command to change the type of a column from timestamp to date

ALTER TABLE table_name CHANGE column_name column_name date CASCADE;

the command was executed successfully.

when i want to retrieve the data from the table using: select * from table_name

I got the following error:

Failed with exception java.io.IOException:org.apache.hadoop.hive.ql.metadata.HiveException: java.lang.ClassCastException: org.apache.hadoop.hive.serde2.io.TimestampWritable cannot be cast to org.apache.hadoop.hive.serde2.io.DateWritable

thanks for help.

Re: Hive Alter column type

nsabharwal — Fri, 29 Jan 2016 21:22:52 GMT

@Ahmed Missaoui

It has to do with the dataset in the table. Check if date has proper fields.

Good reference

Re: Hive Alter column type

ahmed_missaoui_ — Fri, 29 Jan 2016 21:39:10 GMT

Thanks a lot for your help.

Effectively, if the data was stored already with timetamp type and the we change the type, the select will not work and we will have the ClassCastException.

If no data was alreday stored with the timestamp type (all values are null) and then we change the type , the select works fine.