Description
According to https://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:1770086700346491686 (reported in HIVE-12274)
The alter table command to change the column datatype from VARCHAR to CLOB may not work. So the correct way to accomplish this is to add a new temp column, copy the value from the current column, drop the current column and rename the new column to old column.