Need two indexes on a HABTM join table?

Question

A simple has_and_belongs_to_many association:

Person has_and_belongs_to_many :products
Product has_and_belongs_to_many :persons

Ar

Answer 1

You just need one, unless you are doing unique

add_index :person_products, :person_id
add_index :person_products, :product_id

Or for an index on both columns

add_index :person_products, [:person_id, :product_id]

This will help performance when querying on those columns on the database. It will depend on your query if it includes both columns or just one.

http://apidock.com/rails/ActiveRecord/ConnectionAdapters/SchemaStatements/add_index