Despite the "V3" in the type code name,
START_EVENT_V3 currently is used as the type
code not only for v3 start events, but also for v1 start events.
The original symbol for type code 1 was
START_EVENT in the format now known as v1.
Later, when v3 was developed, type code 1 was reused and the
symbol associated with it was renamed from
START_EVENT_V3. The start events for both v1
and v3 therefore have a type code of 1, although the event
structures differ and must be distinguished by examining their
Up to MySQL 5.1.17, event type codes from 20 to 22 were associated with symbols and classes as follows:
In 5.1.18, the symbols and classes were renamed:
Also in 5.1.18, the original symbols were reused with different values and new implementations of the classes that used the original names:
Events with type codes 20 to 22 are obsolete now and appear only in binary logs created by servers from MySQL 5.1.5 to 5.1.17.