DDL commands like:
ALTER TABLE test SET TBLPROPERTIES('serialization.null.format'='');
are silently ignored if the database backing Metastore is Oracle. This appears to be because Oracle treats an empty string as null.
Unlike when using MySql, no entry is created in the TBL_PARAMS table.
Steps to reproduce:
Create a table with a string field.
eg table mytable, field mystringfield.
ALTER TABLE mytable SET TBLPROPERTIES('serialization.null.format'='');
DESCRIBE FORMATTED mytable;
with mysql backed Metastore, the entry will be displayed:
and an entry is created in the TBL_PARAMS for the parameter.
With Oracle backed metastore, it is not, and no entry is created in TBL_PARAMS.