Elixir Ecto: PostgreSQL大自增長主鍵的設定

要解決的問題

資料庫中儲存的行數超過了 serial 型別所能容納的數量, 因此需要採用 bigserial 型別的整數作為主鍵
serial 的取值範圍為: 1 到 2147483647
bigserial 的取值範圍為: 1 到 9223372036854775807

完整的 Postgresql 欄位的資料型別, 可以參考這裡

遷移指令碼

defmodule ElectricProto.Repo.Migrations.AddStationTable do
  use Ecto.Migration

  def up do
    create table(:station, primary_key: false) do
      add :id,          :bigserial, primary_key: true
      timestamps
    end
  end

  def down do
    drop table(:station)
  end
end

要點

1. create table的引數primary_key要設定為false,

2. 通過add巨集指定主鍵列id, 型別為bigserial

模型的宣告

@primary_key {:id, :id, autogenerate: true}

schema "station" do
  field :area,        :string,  default: ""
  field :carrier,     :string,  default: ""
  field :city,        :string,  default: ""
  field :deployed,    :boolean, default: false
  field :description, :string,  default: ""
  field :device_auth, :string,  default: ""
  field :device_type, :string,  default: ""
  field :geolocation, :string,  default: ""
  field :ip_addr,     :string,  default: ""
  field :qrcode,      :string,  default: ""
  field :station_id,  :string,  default: ""
  field :status,      :string,  default: ""
  timestamps
end

要點

1. 主鍵要宣告為:id型別, @primary_key {:id, :id, autogenerate: true}

完!