Limitation

• New schema must have a PRIMARY KEY or at least UNIQUE KEY
• Rename column is not supported
• Both original and new schema must NOT have existing TRIGGER
• Both original and new schema must NOT referencing or being referenced by a FOREIGN KEY
• Only one instance of OSC can work on a MySQL instance at the same time. (We will support parallel schema changes when better throttling is ready)
• Running OSC for the same table on Master and Slave at the same time will break replication.
• OSC will stop replication on slave by default to avoid MDL lock chaining on slaves
• OSC is not able to run schema change together with RBR on any MySQL version other than Facebook's MySQL. See more detail in Q&A