How can I speed-up the table reconstruction in MySQL when altering the schema?

Question

I have a relatively big MySQL InnoDB table (compressed), and I sometimes need to alter its schema (increasing column size or adding a field).

It takes around 1 hour for a 500 MB table with millions of rows, but the server doesn't seem to be very busy (CPU @5%, not much RAM used, and 2.5 MB/s as I/O).

The table is not used in production so there are no concurrent requests at the same time. There is only a primary index (on the first 5 columns) and one foreign key constraint.

Do you have any suggestion on how to speed-up the table alteration process?

Answer 1

在InnoDB被“修复”之前，改变存储引擎（向TokuDB之类的新一代引擎）似乎是必须的。

Answer 2

Would be helpful to know the exact table and primary key/index definitions, and of lesser importance, the row count to the nearest million, although I would guess as the table is only 500mb it's probably less than 20 million rows. Also, your approach to changing the table - are you creating a new schema and inserting into it, or using a alter table etc.

I've had success in this area before with approaches like

• changing the index key composition, adding a unique key
• dropping the indexes first, then changing the table, then adding the indexes back. sometimes independent indexes can be a real performance killer if they are affected by the change.
• optimizing the table structure to remove unneeded or oversized columns
• separating out data (normally columns but you can vertically partition in some circumstances) that won't change from the core structure that might change, so you only churn a smaller part of your table