I have a large (3M rows) InnoDB table in MySQL 5.6.21 in production and I want to add some columns.
From the MySQL Documentation on
Overview of Online DDL I understand that, even if this is an expensive operation that might degrade performance, concurrent DML is allowed as long as I don't add auto-increment columns, and concurrent queries (SELECTs) are always allowed.
Is this right? Do I have to explicitly state
LOCK=NONE in the alter operation for this to be possible?
I'll be adding mainly unindexed, not null VARCHAR columns.