Improve performance when Insert into ... select ...

[Lyu Joey]

my case is:

a database, the table's engine is INNODB, each table has an AUTO_INCREMENT PK, and some of tables have indexs, each table's data comes from other databases by "insert into ... select ...". The source database's table has hundreds of thousands rows at most. I process all of these datas day by day, and each select will retrieve thousands rows.

Now, I found the performance is very low. So, how to improve performance in this case?

Thanks.