Used internally by adapters.
To define an index in a migration, see Ecto.Migration.index/3.
Ecto.Migration.index/3
t() :: %Ecto.Migration.Index{ columns: [atom() | String.t()], comment: String.t() | nil, concurrently: boolean(), include: [atom() | String.t()], name: atom(), options: String.t(), prefix: atom(), table: String.t(), unique: boolean(), using: atom() | String.t(), where: atom() | String.t() }