postgresql - Elixir -- Ecto -- 复合主键和关系

Question

有没有人成功地创建了与具有复合主键的表之间的关系？我正在努力实现以下目标:

create table(:resources, primary_key: false) do
  add :id, :uuid, primary_key: true
  add :version, :id, primary_key: true 
  # ... other details about the resource
end

create table (:resource_instances, primary_key: false) do
  add :id, :uuid, primary_key: true
  add :resource_id,
      references(:resources, type: :uuid, column: :id),
      null: false

  add :resource_version,
      references(:resources, type: :id, column: :version),
      null: false
  # ... specific details about this instance of the resource
end

运行迁移会产生此日志:

11:24:00.100 [info]  create table my_schema.resources

11:24:00.152 [info]  create table my_schema.resource_instances
** (Postgrex.Error) ERROR 42830 (invalid_foreign_key) there is no unique constraint matching given keys for referenced table "resources"
    (ecto_sql) lib/ecto/adapters/sql.ex:629: Ecto.Adapters.SQL.raise_sql_call_error/1
    (elixir) lib/enum.ex:1336: Enum."-map/2-lists^map/1-0-"/2
    (ecto_sql) lib/ecto/adapters/sql.ex:716: Ecto.Adapters.SQL.execute_ddl/4
    (ecto_sql) lib/ecto/migration/runner.ex:343: Ecto.Migration.Runner.log_and_execute_ddl/3
    (ecto_sql) lib/ecto/migration/runner.ex:117: anonymous fn/6 in Ecto.Migration.Runner.flush/0
    (elixir) lib/enum.ex:1948: Enum."-reduce/3-lists^foldl/2-0-"/3
    (ecto_sql) lib/ecto/migration/runner.ex:116: Ecto.Migration.Runner.flush/0
    (stdlib) timer.erl:166: :timer.tc/1
    (ecto_sql) lib/ecto/migration/runner.ex:25: Ecto.Migration.Runner.run/7
    (ecto_sql) lib/ecto/migrator.ex:342: Ecto.Migrator.attempt/7
    (ecto_sql) lib/ecto/migrator.ex:243: anonymous fn/4 in Ecto.Migrator.do_up/4
    (ecto_sql) lib/ecto/migrator.ex:324: anonymous fn/3 in Ecto.Migrator.run_maybe_in_transaction/6
    (ecto_sql) lib/ecto/adapters/sql.ex:898: anonymous fn/3 in Ecto.Adapters.SQL.checkout_or_transaction/4
    (db_connection) lib/db_connection.ex:1415: DBConnection.run_transaction/4
    (ecto_sql) lib/ecto/migrator.ex:323: Ecto.Migrator.run_maybe_in_transaction/6
    (elixir) lib/task/supervised.ex:90: Task.Supervised.invoke_mfa/2
    (elixir) lib/task/supervised.ex:35: Task.Supervised.reply/5
    (stdlib) proc_lib.erl:249: :proc_lib.init_p_do_apply/3

Answer 1

试试这个:

    create table(:resources, primary_key: false) do
        add :id, :uuid, primary_key: true
        add :version, :id, primary_key: true, auto_generate: true
    end
    create unique_index(:resources, [:id])
    create unique_index(:resources, [:version])

    create table(:resource_instances, primary_key: false) do
        add :resource_id,
            references(:resources, type: :uuid, column: :id),
            null: false
        add :resource_version,
            references(:resources, type: :id, column: :version),
            null: false
    end

似乎因为您正在创建复合键，所以您还需要创建单独的唯一索引才能引用这些索引所以基本上为各个列添加了 unique_indices