module Sequel::Model::ClassMethods

  1. lib/sequel/model/base.rb

Class methods for Sequel::Model that implement basic model functionality.

  • All of the following methods have class methods created that send the method to the model's dataset: all, as_hash, avg, count, cross_join, distinct, each, each_server, empty?, except, exclude, exclude_having, fetch_rows, filter, first, first!, for_update, from, from_self, full_join, full_outer_join, get, graph, grep, group, group_and_count, group_append, group_by, having, import, inner_join, insert, intersect, invert, join, join_table, last, left_join, left_outer_join, limit, lock_style, map, max, min, multi_insert, naked, natural_full_join, natural_join, natural_left_join, natural_right_join, offset, order, order_append, order_by, order_more, order_prepend, paged_each, qualify, reverse, reverse_order, right_join, right_outer_join, select, select_all, select_append, select_group, select_hash, select_hash_groups, select_map, select_more, select_order_map, server, single_record, single_record!, single_value, single_value!, sum, to_hash, to_hash_groups, truncate, unfiltered, ungraphed, ungrouped, union, unlimited, unordered, where, where_all, where_each, where_single_value, with, with_recursive, with_sql


cache_anonymous_models [RW]

Whether to cache the anonymous models created by Sequel::Model(), true by default. This is required for reloading them correctly (avoiding the superclass mismatch).

dataset_method_modules [R]

Array of modules that extend this model's dataset. Stored so that if the model's dataset is changed, it will be extended with all of these modules.

dataset_module_class [R]

The Module subclass to use for #dataset_module blocks.

default_set_fields_options [RW]

The default options to use for Model#set_fields. These are merged with the options given to set_fields.

fast_instance_delete_sql [R]

SQL string fragment used for faster DELETE statement creation when deleting/destroying model instances, or nil if the optimization should not be used. For internal use only.

fast_pk_lookup_sql [R]

SQL string fragment used for faster lookups by primary key, or nil if the optimization should not be used. For internal use only.

instance_dataset [R]

The dataset that instance datasets (#this) are based on. Generally a naked version of the model's dataset limited to one row. For internal use only.

plugins [R]

Array of plugin modules loaded by this class

# => [Sequel::Model, Sequel::Model::Associations]
primary_key [R]

The primary key for the class. Sequel can determine this automatically for many databases, but not all, so you may need to set it manually. If not determined automatically, the default is :id.

raise_on_save_failure [RW]

Whether to raise an error instead of returning nil on a failure to save/create/save_changes/update/destroy due to a validation failure or a before_* hook returning false (default: true).

raise_on_typecast_failure [RW]

Whether to raise an error when unable to typecast data for a column (default: false). This should be set to true if you want to have model setter methods raise errors if the argument cannot be typecast properly.

require_modification [RW]

Whether to raise an error if an UPDATE or DELETE query related to a model instance does not modify exactly 1 row. If set to false, Sequel will not check the number of rows modified (default: true).

require_valid_table [RW]

If true (the default), requires that all models have valid tables, raising exceptions if creating a model without a valid table backing it. Setting this to false will allow the creation of model classes where the underlying table doesn't exist.

simple_pk [R]

Should be the literal primary key column name if this Model's table has a simple primary key, or nil if the model has a compound primary key or no primary key.

simple_table [R]

Should be the literal table name if this Model's dataset is a simple table (no select, order, join, etc.), or nil otherwise. This and #simple_pk are used for an optimization in Model.[].

strict_param_setting [RW]

Whether mass assigning via .create/.new/#set/#update should raise an error if an invalid key is used. A key is invalid if no setter method exists for that key or the access to the setter method is restricted (e.g. due to it being a primary key field). If set to false, silently skip any key where the setter method doesn't exist or access to it is restricted.

typecast_empty_string_to_nil [RW]

Whether to typecast the empty string ('') to nil for columns that are not string or blob. In most cases the empty string would be the way to specify a NULL SQL value in string form (nil.to_s == ''), and an empty string would not usually be typecast correctly for other types, so the default is true.

typecast_on_assignment [RW]

Whether to typecast attribute values on assignment (default: true). If set to false, no typecasting is done, so it will be left up to the database to typecast the value correctly.

use_transactions [RW]

Whether to use a transaction by default when saving/deleting records (default: true). If you are sending database queries in before_* or after_* hooks, you shouldn't change the default setting without a good reason.

Public Instance methods

Model (source)

Lets you create a Model subclass with its dataset already set. source should be an instance of one of the following classes:


Sets the database for this model to source. Generally only useful when subclassing directly from the returned class, where the name of the subclass sets the table name (which is combined with the Database in source to create the dataset to use)


Sets the dataset for this model to source.


Sets the table name for this model to source. The class will use the default database for model classes in order to create the dataset.

The purpose of this method is to set the dataset/database automatically for a model class, if the table name doesn't match the default table name that Sequel would use.

When creating subclasses of Sequel::Model itself, this method is usually called on Sequel itself, using Sequel::Model(:something).

# Using a symbol
class Comment < Sequel::Model(:something)
  table_name # => :something

# Using a dataset
class Comment < Sequel::Model(DB1[:something])
  dataset # => DB1[:something]

# Using a database
class Comment < Sequel::Model(DB1)
  dataset # => DB1[:comments]
[show source]
# File lib/sequel/model/base.rb, line 178
def Model(source)
  if cache_anonymous_models
    cache = Sequel.synchronize{@Model_cache ||= {}}
    if klass = Sequel.synchronize{cache[source]}
      return klass

  klass =

  if source.is_a?(::Sequel::Database)
    klass.db = source

  if cache_anonymous_models
    Sequel.synchronize{cache[source] = klass}

[] (*args)

Returns the first record from the database matching the conditions. If a hash is given, it is used as the conditions. If another object is given, it finds the first record whose primary key(s) match the given argument(s). If no object is returned by the dataset, returns nil.

Artist[1] # SELECT * FROM artists WHERE id = 1
# => #<Artist {:id=>1, ...}>

Artist[name: 'Bob'] # SELECT * FROM artists WHERE (name = 'Bob') LIMIT 1
# => #<Artist {:name=>'Bob', ...}>
[show source]
# File lib/sequel/model/base.rb, line 211
def [](*args)
  args = args.first if args.size <= 1
  args.is_a?(Hash) ? first(args) : (primary_key_lookup(args) unless args.nil?)
call (values)

Initializes a model instance as an existing record. This constructor is used by Sequel to initialize model instances when fetching records. Requires that values be a hash where all keys are symbols. It probably should not be used by external code.

[show source]
# File lib/sequel/model/base.rb, line 220
def call(values)
  o = allocate
  o.instance_variable_set(:@values, values)
clear_setter_methods_cache ()

Clear the #setter_methods cache

[show source]
# File lib/sequel/model/base.rb, line 227
def clear_setter_methods_cache
  @setter_methods = nil unless frozen?
columns ()

Returns the columns in the result set in their original order. Generally, this will use the columns determined via the database schema, but in certain cases (e.g. models that are based on a joined dataset) it will use Dataset#columns to find the columns.

# => [:id, :name]
[show source]
# File lib/sequel/model/base.rb, line 238
def columns
  return @columns if @columns
  return nil if frozen?
create (values = {}, &block)

Creates instance using new with the given values and block, and saves it.

Artist.create(name: 'Bob')
# INSERT INTO artists (name) VALUES ('Bob')

Artist.create do |a| = 'Jim'
end # INSERT INTO artists (name) VALUES ('Jim')
[show source]
# File lib/sequel/model/base.rb, line 252
def create(values = {}, &block)
  new(values, &block).save
dataset ()

Returns the dataset associated with the Model class. Raises an Error if there is no associated dataset for this class. In most cases, you don't need to call this directly, as Model proxies many dataset methods to the underlying dataset.

Artist.dataset.all # SELECT * FROM artists
[show source]
# File lib/sequel/model/base.rb, line 262
def dataset
  @dataset || raise(Error, "No dataset associated with #{self}")
dataset= (ds)

Alias of #set_dataset

[show source]
# File lib/sequel/model/base.rb, line 267
def dataset=(ds)
dataset_module (mod = nil)

Extend the dataset with a module, similar to adding a plugin with the methods defined in DatasetMethods. This is the recommended way to add methods to model datasets.

If given an argument, it should be a module, and is used to extend the underlying dataset. Otherwise an anonymous module is created, and if a block is given, it is module_evaled, allowing you do define dataset methods directly using the standard ruby def syntax. Returns the module given or the anonymous module created.

# Usage with existing module
Album.dataset_module Sequel::ColumnsIntrospection

# Usage with anonymous module
Album.dataset_module do
  def foo
# => :bar
# => :bar

Any anonymous modules created are actually instances of Sequel::Model::DatasetModule (a Module subclass), which allows you to call the subset method on them, which defines a dataset method that adds a filter. There are also a number of other methods with the same names as the dataset methods, which can use to define named dataset methods:

Album.dataset_module do
  where(:released, Sequel[:release_date] <= Sequel::CURRENT_DATE)
  order :by_release_date, :release_date
  select :for_select_options, :id, :name, :release_date
# => "SELECT * FROM artists WHERE (release_date <= CURRENT_DATE)"
# => "SELECT * FROM artists ORDER BY release_date"
# => "SELECT id, name, release_date FROM artists"
# => "SELECT id, name, release_date FROM artists WHERE (release_date <= CURRENT_DATE) ORDER BY release_date"

The following methods are supported: distinct, eager, exclude, exclude_having, grep, group, group_and_count, group_append, having, limit, offset, order, order_append, order_prepend, select, select_all, select_append, select_group, where, and server.

The advantage of using these DatasetModule methods to define your dataset methods is that they can take advantage of dataset caching to improve performance.

Any public methods in the dataset module will have class methods created that call the method on the dataset, assuming that the class method is not already defined.

[show source]
# File lib/sequel/model/base.rb, line 326
def dataset_module(mod = nil)
  if mod
    raise Error, "can't provide both argument and block to Model.dataset_module" if block_given?
    @dataset_module ||=
    @dataset_module.module_eval(& if block_given?
db ()

Returns the database associated with the Model class. If this model doesn't have a database associated with it, assumes the superclass's database, or the first object in Sequel::DATABASES. If no Sequel::Database object has been created, raises an error.

Artist.db.transaction do # BEGIN
  Artist.create(name: 'Bob')
  # INSERT INTO artists (name) VALUES ('Bob')
end # COMMIT
[show source]
# File lib/sequel/model/base.rb, line 349
def db
  return @db if @db
  @db = self == Model ? Sequel.synchronize{DATABASES.first} : superclass.db
  raise(Error, "No database associated with #{self}: have you called Sequel.connect or #{self}.db= ?") unless @db
db= (db)

Sets the database associated with the Model class. Should only be used if the Model class currently does not have a dataset defined.

This can be used directly on Sequel::Model to set the default database to be used by subclasses, or to override the database used for specific models:

Sequel::Model.db = DB1
Artist =
Artist.db = DB2

Note that you should not use this to change the model's database at runtime. If you have that need, you should look into Sequel's sharding support, or consider using separate model classes per Database.

[show source]
# File lib/sequel/model/base.rb, line 370
def db=(db)
  raise Error, "Cannot use Sequel::Model.db= on model with existing dataset.  Use Sequel::Model.dataset= instead." if @dataset
  @db = db
db_schema ()

Returns the cached schema information if available or gets it from the database. This is a hash where keys are column symbols and values are hashes of information related to the column. See Database#schema.

# {:id=>{:type=>:integer, :primary_key=>true, ...},
#  :name=>{:type=>:string, :primary_key=>false, ...}}
[show source]
# File lib/sequel/model/base.rb, line 383
def db_schema
  return @db_schema if @db_schema
  return nil if frozen?
  @db_schema = get_db_schema
def_Model (mod)

Define a Model method on the given module that calls the Model method on the receiver. This is how the Sequel::Model() method is defined, and allows you to define Model() methods on other modules, making it easier to have custom model settings for all models under a namespace. Example:

module Foo
  Model =
  DB = Model.db = Sequel.connect(ENV['FOO_DATABASE_URL'])
  Model.plugin :prepared_statements

  class Bar < Model
    # Uses Foo::DB[:bars]

  class Baz < Model(:my_baz)
    # Uses Foo::DB[:my_baz]
[show source]
# File lib/sequel/model/base.rb, line 136
def def_Model(mod)
  model = self
  mod.define_singleton_method(:Model) do |source|
def_column_alias (meth, column)

Create a column alias, where the column methods have one name, but the underlying storage uses a different name.

[show source]
# File lib/sequel/model/base.rb, line 391
def def_column_alias(meth, column)
  overridable_methods_module.module_eval do
    define_method("#{meth}="){|v| self[column] = v}
find (*args, &block)

Finds a single record according to the supplied filter. You are encouraged to use Model.[] or Model.first instead of this method.

Artist.find(name: 'Bob')
# SELECT * FROM artists WHERE (name = 'Bob') LIMIT 1

Artist.find{name > 'M'}
# SELECT * FROM artists WHERE (name > 'M') LIMIT 1
[show source]
# File lib/sequel/model/base.rb, line 407
def find(*args, &block)
  first(*args, &block)
find_or_create (cond, &block)

Like find but invokes create with given conditions when record does not exist. Unlike find in that the block used in this method is not passed to find, but instead is passed to create only if find does not return an object.

Artist.find_or_create(name: 'Bob')
# SELECT * FROM artists WHERE (name = 'Bob') LIMIT 1
# INSERT INTO artists (name) VALUES ('Bob')

Artist.find_or_create(name: 'Jim'){|a| a.hometown = 'Sactown'}
# SELECT * FROM artists WHERE (name = 'Jim') LIMIT 1
# INSERT INTO artists (name, hometown) VALUES ('Jim', 'Sactown')
[show source]
# File lib/sequel/model/base.rb, line 423
def find_or_create(cond, &block)
  find(cond) || create(cond, &block)
freeze ()

Freeze a model class, disallowing any further changes to it.

[show source]
# File lib/sequel/model/base.rb, line 428
def freeze
  return self if frozen?

  if @dataset
    @setter_methods = [].freeze


implicit_table_name ()

Returns the implicit table name for the model class, which is the demodulized, underscored, pluralized name of the class.

Artist.implicit_table_name # => :artists
Foo::ArtistAlias.implicit_table_name # => :artist_aliases
[show source]
# File lib/sequel/model/base.rb, line 501
def implicit_table_name
include (*mods)

Clear the #setter_methods cache when a module is included, as it may contain setter methods.

[show source]
# File lib/sequel/model/base.rb, line 450
def include(*mods)
inherited (subclass)

If possible, set the dataset for the model subclass as soon as it is created. Also, make sure the inherited class instance variables are copied into the subclass.

Sequel queries the database to get schema information as soon as a model class is created:

class Artist < Sequel::Model # Causes schema query
[show source]
# File lib/sequel/model/base.rb, line 464
def inherited(subclass)
  ivs = subclass.instance_variables
  inherited_instance_variables.each do |iv, dup|
    next if ivs.include?(iv)
    if (sup_class_value = instance_variable_get(iv)) && dup
      sup_class_value = case dup
      when :dup
      when :hash_dup
        h = {}
        sup_class_value.each{|k,v| h[k] = v.dup}
      when Proc
        raise Error, "bad inherited instance variable type: #{dup.inspect}"
    subclass.instance_variable_set(iv, sup_class_value)

  unless ivs.include?("@dataset")
    if @dataset && self != Model
      subclass.set_dataset(@dataset.clone, :inherited=>true)
    elsif (n = && !n.to_s.empty?
load (values)

Calls call with the values hash.

[show source]
# File lib/sequel/model/base.rb, line 506
def load(values)
method_added (meth)

Clear the #setter_methods cache when a setter method is added.

[show source]
# File lib/sequel/model/base.rb, line 511
def method_added(meth)
  clear_setter_methods_cache if meth.to_s.end_with?('=')
no_primary_key ()

Mark the model as not having a primary key. Not having a primary key can cause issues, among which is that you won't be able to update records.

Artist.primary_key # => :id
Artist.primary_key # => nil
[show source]
# File lib/sequel/model/base.rb, line 522
def no_primary_key
  self.simple_pk = @primary_key = nil
plugin (plugin, *args, &block)

Loads a plugin for use with the model class, passing optional arguments to the plugin. If the plugin is a module, load it directly. Otherwise, require the plugin from sequel/plugins/#{plugin} and then attempt to load the module using a the camelized plugin name under Sequel::Plugins.

[show source]
# File lib/sequel/model/base.rb, line 531
def plugin(plugin, *args, &block)
  m = plugin.is_a?(Module) ? plugin : plugin_module(plugin)
  unless @plugins.include?(m)
    @plugins << m
    m.apply(self, *args, &block) if m.respond_to?(:apply)
    extend(m::ClassMethods) if m.const_defined?(:ClassMethods, false)
    include(m::InstanceMethods) if m.const_defined?(:InstanceMethods, false)
    if m.const_defined?(:DatasetMethods, false)
      dataset_extend(m::DatasetMethods, :create_class_methods=>false)
  m.configure(self, *args, &block) if m.respond_to?(:configure)
primary_key_hash (value)

Returns primary key attribute hash. If using a composite primary key value such be an array with values for each primary key in the correct order. For a standard primary key, value should be an object with a compatible type for the key. If the model does not have a primary key, raises an Error.

Artist.primary_key_hash(1) # => {:id=>1}
Artist.primary_key_hash([1, 2]) # => {:id1=>1, :id2=>2}
[show source]
# File lib/sequel/model/base.rb, line 553
def primary_key_hash(value)
  case key = @primary_key
  when Symbol
    {key => value}
  when Array
    hash = {}{|k,v| hash[k] = v}
    raise(Error, "#{self} does not have a primary key")
qualified_primary_key_hash (value, qualifier=table_name)

Return a hash where the keys are qualified column references. Uses the given qualifier if provided, or the #table_name otherwise. This is useful if you plan to join other tables to this table and you want the column references to be qualified.

# SELECT * FROM artists WHERE ( = 1)
[show source]
# File lib/sequel/model/base.rb, line 573
def qualified_primary_key_hash(value, qualifier=table_name)
  case key = @primary_key
  when Symbol
    {, key) => value}
  when Array
    hash = {}{|k,v| hash[, k)] = v}
    raise(Error, "#{self} does not have a primary key")
restrict_primary_key ()

Restrict the setting of the primary key(s) when using mass assignment (e.g. set). Because this is the default, this only make sense to use in a subclass where the parent class has used unrestrict_primary_key.

[show source]
# File lib/sequel/model/base.rb, line 589
def restrict_primary_key
  @restrict_primary_key = true
restrict_primary_key? ()

Whether or not setting the primary key(s) when using mass assignment (e.g. set) is restricted, true by default.

[show source]
# File lib/sequel/model/base.rb, line 596
def restrict_primary_key?
set_dataset (ds, opts=OPTS)

Sets the dataset associated with the Model class. ds can be a Symbol, LiteralString, SQL::Identifier, SQL::QualifiedIdentifier, SQL::AliasedExpression (all specifying a table name in the current database), or a Dataset. If a dataset is used, the model's database is changed to the database of the given dataset. If a dataset is not used, a dataset is created from the current database with the table name given. Other arguments raise an Error. Returns self.

It also attempts to determine the database schema for the model, based on the given dataset.

Note that you should not use this to change the model's dataset at runtime. If you have that need, you should look into Sequel's sharding support, or creating a separate Model class per dataset

You should avoid calling this method directly if possible. Instead you should set the table name or dataset when creating the model class:

# table name
class Artist < Sequel::Model(:tbl_artists)

# dataset
class Artist < Sequel::Model(DB[:tbl_artists])
[show source]
# File lib/sequel/model/base.rb, line 626
def set_dataset(ds, opts=OPTS)
  inherited = opts[:inherited]
  @dataset = convert_input_dataset(ds)
  @require_modification = @dataset.provides_accurate_rows_matched? if require_modification.nil?
  if inherited
    self.simple_table = superclass.simple_table
    @columns = superclass.instance_variable_get(:@columns)
    @db_schema = superclass.instance_variable_get(:@db_schema)
    @dataset = @dataset.with_extend(*@dataset_method_modules.reverse) if @dataset_method_modules
    @db_schema = get_db_schema

set_primary_key (key)

Sets the primary key for this model. You can use either a regular or a composite primary key. To not use a primary key, set to nil or use no_primary_key. On most adapters, Sequel can automatically determine the primary key to use, so this method is not needed often.

class Person < Sequel::Model
  # regular key
  set_primary_key :person_id

class Tagging < Sequel::Model
  # composite key
  set_primary_key [:taggable_id, :tag_id]
[show source]
# File lib/sequel/model/base.rb, line 657
def set_primary_key(key)
  if key.is_a?(Array)
    if key.length < 2
      key = key.first
      key = key.dup.freeze
  self.simple_pk = if key && !key.is_a?(Array)
    (@dataset || db).literal(key).freeze
  @primary_key = key
setter_methods ()

Cache of setter methods to allow by default, in order to speed up mass assignment.

[show source]
# File lib/sequel/model/base.rb, line 673
def setter_methods
  return @setter_methods if @setter_methods
  @setter_methods = get_setter_methods
table_name ()

Returns name of primary table for the dataset. If the table for the dataset is aliased, returns the aliased name.

Artist.table_name # => :artists
Sequel::Model(:foo).table_name # => :foo
Sequel::Model(Sequel[:foo].as(:bar)).table_name # => :bar
[show source]
# File lib/sequel/model/base.rb, line 684
def table_name
unrestrict_primary_key ()

Allow the setting of the primary key(s) when using the mass assignment methods. Using this method can open up security issues, be very careful before using it.

Artist.set(id: 1) # Error
Artist.set(id: 1) # No Error
[show source]
# File lib/sequel/model/base.rb, line 694
def unrestrict_primary_key
  @restrict_primary_key = false
with_pk (pk)

Return the model instance with the primary key, or nil if there is no matching record.

[show source]
# File lib/sequel/model/base.rb, line 700
def with_pk(pk)
with_pk! (pk)

Return the model instance with the primary key, or raise NoMatchingRow if there is no matching record.

[show source]
# File lib/sequel/model/base.rb, line 705
def with_pk!(pk)
  with_pk(pk) || raise(