Creating a unique constraint on two columns together in Ecto

Question

How do you create a unique index on two columns in Ecto, which would correspond to this:

CREATE TABLE someTable (     col1 int NOT NULL,     col2 int NOT NULL,     primary key (col1, col2) ) 

?

Answer 1

A Little follow up on Patrick's answer

Using only create unique_index on your model will ultimately throw an exception instead of giving you an error.

To get an error add a constraint on your changeset but as a paremeter you can give the index name created by unique_index.

So in your migration file :

create unique_index(:your_table, [:col1, :col2], name: :your_index_name) 

Then in your changeset :

def changeset(model, param \\ :empty) do   model   |> cast(params, @required_fields, @optional_fields)   |> unique_constraint(:name_your_constraint, name: :your_index_name) end