Ecto migration with unique_index on multiple fields.

20160922000000_branches_street_address_unique_constraint.exs

defmodule VetMapper.Repo.Migrations.BranchesStreetAddressUniqueConstraint do
  use Ecto.Migration

  def up do
    create unique_index(:branches, [:country, :state, :city, :street_name, :street_number], name: :index_branches_on_address)
  end
  
  def down do
    drop index(:branches, [:country, :state, :city, :street_name, :street_number], name: :index_branches_on_address)
  end
  
end

Mock models can be found here: https://gist.github.com/Ivor/6c59b45e2aa982b13e27e06fc486b3f2
Blog post: https://medium.com/@ivorpaul/ecto-how-to-validate-unique-combinations-of-multiple-fields-8002c74c6757#.f1iwh3dzf