How do you convert an existing string column to the enum type ?

[happysalada]

just modifying the column to the created enum type gives an error

** (Postgrex.Error) ERROR 42804 (datatype_mismatch): column "origin" cannot be cast automatically to type origin
    (ecto) lib/ecto/adapters/sql.ex:200: Ecto.Adapters.SQL.query!/5
    (ecto) lib/ecto/adapters/postgres.ex:85: anonymous fn/4 in Ecto.Adapters.Postgres.execute_ddl/3
    (elixir) lib/enum.ex:1899: Enum."-reduce/3-lists^foldl/2-0-"/3
    (ecto) lib/ecto/adapters/postgres.ex:85: Ecto.Adapters.Postgres.execute_ddl/3
    (ecto) lib/ecto/migration/runner.ex:104: anonymous fn/2 in Ecto.Migration.Runner.flush/0
    (elixir) lib/enum.ex:1899: Enum."-reduce/3-lists^foldl/2-0-"/3
    (ecto) lib/ecto/migration/runner.ex:102: Ecto.Migration.Runner.flush/0
    (stdlib) timer.erl:181: :timer.tc/2
    (ecto) lib/ecto/migration/runner.ex:26: Ecto.Migration.Runner.run/6
    (ecto) lib/ecto/migrator.ex:128: Ecto.Migrator.attempt/6
    (ecto) lib/ecto/migrator.ex:72: anonymous fn/4 in Ecto.Migrator.do_up/4
    (ecto) lib/ecto/adapters/sql.ex:576: anonymous fn/3 in Ecto.Adapters.SQL.do_transaction/3
    (db_connection) lib/db_connection.ex:1283: DBConnection.transaction_run/4
    (db_connection) lib/db_connection.ex:1207: DBConnection.run_begin/3
    (db_connection) lib/db_connection.ex:798: DBConnection.transaction/3
    (ecto) lib/ecto/migrator.ex:261: anonymous fn/4 in Ecto.Migrator.migrate/4
    (elixir) lib/enum.ex:1294: Enum."-map/2-lists^map/1-0-"/2
    (ecto) lib/mix/tasks/ecto.migrate.ex:83: anonymous fn/4 in Mix.Tasks.Ecto.Migrate.run/2
    (elixir) lib/enum.ex:737: Enum."-each/2-lists^foreach/1-0-"/2
    (elixir) lib/enum.ex:737: Enum.each/2
[error] GenServer Union.Repo terminating
** (Postgrex.Error) ERROR 42804 (datatype_mismatch): column "origin" cannot be cast automatically to type origin
    (ecto) lib/ecto/adapters/sql.ex:200: Ecto.Adapters.SQL.query!/5
    (ecto) lib/ecto/adapters/postgres.ex:85: anonymous fn/4 in Ecto.Adapters.Postgres.execute_ddl/3
    (elixir) lib/enum.ex:1899: Enum."-reduce/3-lists^foldl/2-0-"/3
    (ecto) lib/ecto/adapters/postgres.ex:85: Ecto.Adapters.Postgres.execute_ddl/3
    (ecto) lib/ecto/migration/runner.ex:104: anonymous fn/2 in Ecto.Migration.Runner.flush/0
    (elixir) lib/enum.ex:1899: Enum."-reduce/3-lists^foldl/2-0-"/3
    (ecto) lib/ecto/migration/runner.ex:102: Ecto.Migration.Runner.flush/0
    (stdlib) timer.erl:181: :timer.tc/2
    (ecto) lib/ecto/migration/runner.ex:26: Ecto.Migration.Runner.run/6
    (ecto) lib/ecto/migrator.ex:128: Ecto.Migrator.attempt/6
    (ecto) lib/ecto/migrator.ex:72: anonymous fn/4 in Ecto.Migrator.do_up/4
    (ecto) lib/ecto/adapters/sql.ex:576: anonymous fn/3 in Ecto.Adapters.SQL.do_transaction/3
    (db_connection) lib/db_connection.ex:1283: DBConnection.transaction_run/4
    (db_connection) lib/db_connection.ex:1207: DBConnection.run_begin/3
    (db_connection) lib/db_connection.ex:798: DBConnection.transaction/3
    (ecto) lib/ecto/migrator.ex:261: anonymous fn/4 in Ecto.Migrator.migrate/4
    (elixir) lib/enum.ex:1294: Enum."-map/2-lists^map/1-0-"/2
    (ecto) lib/mix/tasks/ecto.migrate.ex:83: anonymous fn/4 in Mix.Tasks.Ecto.Migrate.run/2
    (elixir) lib/enum.ex:737: Enum."-each/2-lists^foreach/1-0-"/2
    (elixir) lib/enum.ex:737: Enum.each/2
Last message: {:EXIT, #PID<0.73.0>, {%Postgrex.Error{connection_id: 42580, message: nil, postgres: %{code: :datatype_mismatch, file: "tablecmds.c", hint: "You might need to specify \"USING origin::origin\".", line: "8007", message: "column \"origin\" cannot be cast automatically to type origin", pg_code: "42804", routine: "ATPrepAlterColumnType", severity: "ERROR", unknown: "ERROR"}}, [{Ecto.Adapters.SQL, :query!, 5, [file: 'lib/ecto/adapters/sql.ex', line: 200]}, {Ecto.Adapters.Postgres, :"-execute_ddl/3-fun-0-", 4, [file: 'lib/ecto/adapters/postgres.ex', line: 85]}, {Enum, :"-reduce/3-lists^foldl/2-0-", 3, [file: 'lib/enum.ex', line: 1899]}, {Ecto.Adapters.Postgres, :execute_ddl, 3, [file: 'lib/ecto/adapters/postgres.ex', line: 85]}, {Ecto.Migration.Runner, :"-flush/0-fun-1-", 2, [file: 'lib/ecto/migration/runner.ex', line: 104]}, {Enum, :"-reduce/3-lists^foldl/2-0-", 3, [file: 'lib/enum.ex', line: 1899]}, {Ecto.Migration.Runner, :flush, 0, [file: 'lib/ecto/migration/runner.ex', line: 102]}, {:timer, :tc, 2, [file: 'timer.erl', line: 181]}, {Ecto.Migration.Runner, :run, 6, [file: 'lib/ecto/migration/runner.ex', line: 26]}, {Ecto.Migrator, :attempt, 6, [file: 'lib/ecto/migrator.ex', line: 128]}, {Ecto.Migrator, :"-do_up/4-fun-1-", 4, [file: 'lib/ecto/migrator.ex', line: 72]}, {Ecto.Adapters.SQL, :"-do_transaction/3-fun-1-", 3, [file: 'lib/ecto/adapters/sql.ex', line: 576]}, {DBConnection, :transaction_run, 4, [file: 'lib/db_connection.ex', line: 1283]}, {DBConnection, :run_begin, 3, [file: 'lib/db_connection.ex', line: 1207]}, {DBConnection, :transaction, 3, [file: 'lib/db_connection.ex', line: 798]}, {Ecto.Migrator, :"-migrate/4-fun-0-", 4, [file: 'lib/ecto/migrator.ex', line: 261]}, {Enum, :"-map/2-lists^map/1-0-", 2, [file: 'lib/enum.ex', line: 1294]}, {Mix.Tasks.Ecto.Migrate, :"-run/2-fun-1-", 4, [file: 'lib/mix/tasks/ecto.migrate.ex', line: 83]}, {Enum, :"-each/2-lists^foreach/1-0-", 2, [file: 'lib/enum.ex', line: 737]}, {Enum, :each, 2, [file: 'lib/enum.ex', line: 737]}]}}
State: {:state, {:local, Union.Repo}, :one_for_one, [{:child, #PID<0.259.0>, DBConnection.Poolboy, {:poolboy, :start_link, [[name: {:local, Union.Repo.Pool}, strategy: :fifo, size: 1, max_overflow: 0, worker_module: DBConnection.Poolboy.Worker], {Postgrex.Protocol, [types: Ecto.Adapters.Postgres.TypeModule, port: 5432, name: Union.Repo.Pool, otp_app: :union, repo: Union.Repo, timeout: 15000, pool_timeout: 5000, adapter: Ecto.Adapters.Postgres, username: "postgres", password: "92009gtk9", database: "mylocaldb", hostname: "localhost", pool_size: 1, pool: DBConnection.Poolboy]}]}, :permanent, 5000, :worker, [:poolboy]}], :undefined, 3, 5, [], 0, Ecto.Repo.Supervisor, {Union.Repo, :union, Ecto.Adapters.Postgres, [pool_size: 1]}}

[gabrielpra1]

This is how I did to change the column role from my users table from string to UserRoleEnum.

def up do
  UserRoleEnum.create_type
  execute "alter table users alter column role type role using (role::role)"
end

def down do
  execute "alter table users alter column role type character varying(255)"
  UserRoleEnum.drop_type
end