Currently there is no an easy way to convert on upgrade old TIME, DATETIME, TIMESTAMP (handled by Field_time, Field_datetime, Field_timestamp) columns to new columns (handled by Field_timef, Field_datetimef, Field_timestampf).

Conversion is necessary in some scenarios:

• To import InnoDB table spaces
• For replication purposes (as old temporal formats did not replicate fractional second precision in the data type metadata)

Possible conversion options:

• dump followed by restore
• "ALTER TABLE t1 MODIFY time_column TIME", i.e. using MODIFY with "same" data type.

Both ways are not convenient.

We'll fix ALTER TABLE t1 FORCE to replace old temporal columns according to the current @@mysql56_temporal_format settings:

• If @@mysql56_temporal_format is true, all TIME, DATETIME, TIMESTAMP columns will be replaced to the new format.
• If @@mysql56_temporal_format is false, all TIME, DATETIME, TIMESTAMP columns will be replaced to the old format.