Unique Indexes With Ecto
You can create a unique index in a migration for one or more columns using the unique_index/3
function.
For example, if you are creating a join table for followers
and want to ensure that duplicate follower entries are prevented, you may want to include a unique index like so:
create table(:followers) do
add :followed_user, references(:users), null: false
add :following_user, references(:users), null: false
end
create unique_index(:followers, [:followed_user, :following_user])
Keep in mind that unique_index/3
is a shorthand for index/3
when you set unique: true
.
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