79580

Performance and Concurrency Considerations for Online DDL

Online DDL improves several aspects of MySQL operation, such as performance, concurrency, availability, and scalability:

•    Because queries and DML operations on the table can proceed while the DDL is in progress,

applications that access the table are morę responsive. Reduced locking and warting for other

resources all throughout the MySQL server leads to greater scalability, even for operations not involving the table being altered.

•    For in-place operations, by avoiding the disk 1/0 and CPU cycles to rebuild the table, you minimize

the overall load on the database and maintain good performance and high throughput during the DDL operation.

•    For in-place operations, because less data is read into the buffer pool than if all the data was copied,

you avoid purging frequently accessed data from memory, which formerly could cause a temporary performance dip after a DDL operation.