Rails：使用迁移创建关联

Question

I have a User table and a Product table. There is a has_many :products and a belongs_to :user relationship. I defined the Product and User models correctly...my question is about setting up the migration so that the schema comes out right. I tried and this was the extra line in the schema that i got.

add_index "product", ["user_id"], name: "index_product_on_user_id"

I then had a look online and instead of add_index other code had add_reference...does that matter? And not sure about the name: "index_product_on_user_id". Thanks!

Answer 1

add_reference adds the required columns and (optionally) creates an index whereas add_index just creates the index, so if you want to use add_index you need to create the column separately.

You almost never need to set the index name - it doesn't affect how the index works or is used (one case is where the autogenerated index name exceeds the maximum index length).