Working with pre-CQL 3 applications
Internally, CQL does not change the row and column mapping from the Thrift API mapping. CQL and Thrift use the same storage engine. CQL supports the same query-driven, denormalized data modeling principles as Thrift. Existing applications do not have to be upgraded to CQL version 3.0. The abstraction layer makes CQL easier to use for new applications. For an in-depth comparison of Thrift and CQL, see A Thrift to CQL 3 Upgrade Guide and CQL 3 for Cassandra experts.
Creating a legacy table
You can create Thrift/CLI-compatible tables in CQL 3 using the COMPACT STORAGE directive. The compact storage directive used with the CREATE TABLE command provides backward compatibility with older Cassandra applications; new applications should generally avoid it.
Compact storage stores an entire row in a single column on disk instead of storing each non-primary key column in a column that corresponds to one column on disk. Using compact storage prevents you from adding new columns that are not part of the PRIMARY KEY.