why does create index with SET FOREIGN_KEY_CHECKS=0; and SET UNIQUE_CHECKS = 0; take a lot of time? i am adding index to a very large table , around 25 M records and 60 GB of data.
i am using MYSQL version 5.6 InnoDB , my statement is :

SET FOREIGN_KEY_CHECKS=0;
SET UNIQUE_CHECKS = 0;
ALTER TABLE `my_table`
ADD   KEY `my_idx` (`site_id`,`name`);


and i am running it like this :

mysql --host=**.database.azure.com -u *** -p*** my_db &lt; my_file.sql


but it take around 1 hour , the same time as without this statement , what am i missing ?
SET FOREIGN_KEY_CHECKS=0; and SET UNIQUE_CHECKS = 0; are meant for speeding up imports (typically INSERT statements) into tables where foreign keys and unique indexes already exist. They are not meant to speed up the creation of indexes.