ActiveRecord enum / PostgreSQL enum

map_ar_enum_to_pg_enum.rb

# require 'pg'; PG.connect(dbname: 'postgres').exec('create database josh_testing') # <-- uncomment to create the db (only needs to run once)

# ===== Setup ActiveRecord =====
require 'active_record'
require 'logger'
ActiveRecord::Base.establish_connection adapter: 'postgresql', database: 'josh_testing'
ActiveRecord::Base.logger = Logger.new $stdout
ActiveSupport::LogSubscriber.colorize_logging = false

# ===== Migration =====
ActiveRecord::Schema.define do
  self.verbose = false

  # reset db
  drop_table :tasks, if_exists: true
  execute "drop type if exists task_status;"

  # create the type
  execute "create type task_status as enum ('completed', 'in_progress', 'pending', 'open', 'rescheduled');"

  # create the table
  create_table :tasks do |t|
    t.column :status, :task_status, null: false
  end
end

# ===== Model =====
class Task < ActiveRecord::Base
  enum status: {
    completed:   'completed',
    in_progress: 'in_progress',
    pending:     'pending',
    open:        'open',
    rescheduled: 'rescheduled',
  }
end

# ===== Create some tasks =====
Task.create! [
  {status: 'completed'},
  {status: 'completed'},
  {status: 'pending'},
  {status: 'open' },
]

# ===== Querying =====
Task.completed.to_sql
# => "SELECT \"tasks\".* FROM \"tasks\" WHERE \"tasks\".\"status\" = 'completed'"

Task.completed
# => [#<Task:0x00007ff3ae0e8090 id: 1, status: "completed">,
#     #<Task:0x00007ff3ae0f3e18 id: 2, status: "completed">]
Task.pending
# => [#<Task:0x00007ff3ae10a960 id: 3, status: "pending">]
Task.open
# => [#<Task:0x00007ff3ada2bc70 id: 4, status: "open">]

# ===== Invalid Values =====
# All three of these seem like strange behaviour to me, feels like it should just add a validation
Task.new(status: 'something_else') rescue $! # => #<ArgumentError: 'something_else' is not a valid status>
Task.new.valid?                              # => true
Task.new.save rescue $!                      # => #<ActiveRecord::NotNullViolation: PG::NotNullViolation: ERROR:  null value in column "status" violates not-null constraint\nDETAIL:  Failing row co...

# We can address the last two with our own validation
Task.validates :status, inclusion: { in: Task.statuses.keys }

Task.new(status: 'something_else') rescue $! # => #<ArgumentError: 'something_else' is not a valid status>
t = Task.new
t.valid?                                     # => false
t.errors.full_messages                       # => ["Status is not included in the list"]

# >> D, [2019-07-31T10:39:04.582684 #89309] DEBUG -- :    (4.4ms)  DROP TABLE IF EXISTS "tasks"
# >> D, [2019-07-31T10:39:04.585073 #89309] DEBUG -- :    (1.9ms)  drop type if exists task_status;
# >> D, [2019-07-31T10:39:04.588222 #89309] DEBUG -- :    (2.7ms)  create type task_status as enum ('completed', 'in_progress', 'pending', 'open', 'rescheduled');
# >> D, [2019-07-31T10:39:04.594838 #89309] DEBUG -- :    (5.9ms)  CREATE TABLE "tasks" ("id" bigserial primary key, "status" task_status NOT NULL)
# >> D, [2019-07-31T10:39:04.634232 #89309] DEBUG -- :   ActiveRecord::InternalMetadata Load (0.5ms)  SELECT  "ar_internal_metadata".* FROM "ar_internal_metadata" WHERE "ar_internal_metadata"."key"...
# >> D, [2019-07-31T10:39:04.674247 #89309] DEBUG -- :    (0.4ms)  BEGIN
# >> D, [2019-07-31T10:39:04.675448 #89309] DEBUG -- :    (0.2ms)  COMMIT
# >> W, [2019-07-31T10:39:04.676516 #89309]  WARN -- : Creating scope :open. Overwriting existing method Task.open.
# >> D, [2019-07-31T10:39:04.684591 #89309] DEBUG -- :    (0.2ms)  BEGIN
# >> D, [2019-07-31T10:39:04.686838 #89309] DEBUG -- :   Task Create (0.7ms)  INSERT INTO "tasks" ("status") VALUES ($1) RETURNING "id"  [["status", "completed"]]
# >> D, [2019-07-31T10:39:04.688405 #89309] DEBUG -- :    (1.2ms)  COMMIT
# >> D, [2019-07-31T10:39:04.688896 #89309] DEBUG -- :    (0.1ms)  BEGIN
# >> D, [2019-07-31T10:39:04.689679 #89309] DEBUG -- :   Task Create (0.3ms)  INSERT INTO "tasks" ("status") VALUES ($1) RETURNING "id"  [["status", "completed"]]
# >> D, [2019-07-31T10:39:04.691084 #89309] DEBUG -- :    (1.2ms)  COMMIT
# >> D, [2019-07-31T10:39:04.691541 #89309] DEBUG -- :    (0.1ms)  BEGIN
# >> D, [2019-07-31T10:39:04.692292 #89309] DEBUG -- :   Task Create (0.3ms)  INSERT INTO "tasks" ("status") VALUES ($1) RETURNING "id"  [["status", "pending"]]
# >> D, [2019-07-31T10:39:04.693792 #89309] DEBUG -- :    (1.2ms)  COMMIT
# >> D, [2019-07-31T10:39:04.694248 #89309] DEBUG -- :    (0.1ms)  BEGIN
# >> D, [2019-07-31T10:39:04.694988 #89309] DEBUG -- :   Task Create (0.3ms)  INSERT INTO "tasks" ("status") VALUES ($1) RETURNING "id"  [["status", "open"]]
# >> D, [2019-07-31T10:39:04.696737 #89309] DEBUG -- :    (1.5ms)  COMMIT
# >> D, [2019-07-31T10:39:04.698658 #89309] DEBUG -- :   Task Load (0.3ms)  SELECT "tasks".* FROM "tasks" WHERE "tasks"."status" = $1  [["status", "completed"]]
# >> D, [2019-07-31T10:39:04.699880 #89309] DEBUG -- :   Task Load (0.3ms)  SELECT "tasks".* FROM "tasks" WHERE "tasks"."status" = $1  [["status", "pending"]]
# >> D, [2019-07-31T10:39:04.700838 #89309] DEBUG -- :   Task Load (0.3ms)  SELECT "tasks".* FROM "tasks" WHERE "tasks"."status" = $1  [["status", "open"]]
# >> D, [2019-07-31T10:39:04.701720 #89309] DEBUG -- :    (0.2ms)  BEGIN
# >> D, [2019-07-31T10:39:04.702980 #89309] DEBUG -- :   Task Create (0.6ms)  INSERT INTO "tasks" DEFAULT VALUES RETURNING "id"
# >> D, [2019-07-31T10:39:04.703311 #89309] DEBUG -- :    (0.2ms)  ROLLBACK