Create an index on a huge MySQL production table without table locking

Question

I need to create an index on a ~5M rows MySQL table. It is a production table, and I fear a complete block of everything if I run a CREATE INDEX statement...

Is the

Answer 1

pt-online-schema-change is the way to go if you really want to make sure that the migration will not bring down the site.

As I wrote in the above comment, I have several experiences with pt-online-schema-change in production. We have our main table of 20M+ records and a master -> 2 read-only replication slaves. I've done at least a dozens of migrations with pt-online-schema-change from adding a new column, changing charset, to adding several indices. We serve tons of traffic during the migration time as well and we have not had any hiccup. Of course you'd have to test all the scripts very thoroughly before running on production.

I tried to batch up the changes into 1 script so that pt-online-schema-change only have to copy the data once. And be very careful with changing column name since you will loose your data. However, adding an index should be fine.