If the backend database is MySQL and the COMMENT column does not use the latin1 character set, you must back up the COLUMNS_V2 table before upgrading. Otherwise, the COMMENT column data might become corrupted and cannot be reverted. In this case, you must modify the MySQL ALTER TABLE statement according to the active character set. For example, if the COMMENT column uses the UTF-8 character set, run the following commands:
ALTER TABLE COLUMNS_V2 MODIFY COLUMN COMMENT varchar(4000) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin DEFAULT NULL, ALGORITHM=COPY;
-- Update the schema version
UPDATE CDH_VERSION SET SCHEMA_VERSION='3.1.3000.7.3.2.0-Update2', VERSION_COMMENT='Hive release version 3.1.3000 for CDH 7.3.2.0-Update2' WHERE VER_ID=1;