Hi,

Been reading through the High Performance book and stumbled on the part suggestion using IN(...) in order to make subsequent columns in the index accessible.

I have some questions - given the table parts with columns (id, sizes, created_at) and an index on (sizes, created_at) - if the column sizes can have values 1 through 4, would the following perform equally well:

SELECT * FROM parts WHERE sizes IN (3,4)
SELECT * FROM parts WHERE sizes > 2

This is to understand the case where there's no need for not doing the range scan, ie. there's no need to use a subsequent column in the index.

Another range scan question: Using != will result in a "bad range scan" right? Example:

-- Bad
SELECT * FROM parts WHERE sizes != 4 AND created_at > ...

-- Good
SELECT * FROM parts WHERE sizes IN (1,2,3) AND created_at > ...

Is this understanding correct or did I not get the subtleties right?

Thank you.