Rails, add_index (mysql, innodb). 50-100 thousand lines, how long should it take?

Question

MySQL

Ubuntu
Mysql 5.5 (innodb)
Rails 3.2
Spree 1.3
I'm doing add index on a table with 50-100 thousand rows on a working machine.
The migration has been hanging for an hour now.
Iron is average, I / O operations, I mean not very (on win7 they showed a score of 3.7, the rest of the parameters were 5-7)
How to add indexes correctly? How can you roughly estimate the time (since different sources write very differently)?
PS If e-commerce is used with a large number of selects, frequent searches, etc. and relatively rare insert, update, delete, does it make sense to migrate to myiasam?

Answer 1

rails 4, mariaDB is there a possibility to move?