hello， I have 2 tables need to do "join" operation by their primary key, the primary key of these 2 tables are both type "String".
There are 200 million pieces of data in the big table and only 20 throusand pieces of data in the small table. This join operation is quite slow. I want to know does index be used when doing "join" operation between a big table and a small table? And how to confirm whether index be used? sunerhan1...@sina.com
