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Class: ActiveRecord::ConnectionAdapters::TableDefinition

Relationships & Source Files
Extension / Inclusion / Inheritance Descendants
Subclasses:
MySQL::TableDefinition, PostgreSQL::TableDefinition, SQLite3::TableDefinition
Super Chains via Extension / Inclusion / Inheritance
Instance Chain:
self, ColumnMethods
Inherits: Object
Defined in: activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb

Overview

Represents the schema of an SQL table in an abstract way. This class provides methods for manipulating the schema representation.

Inside migration files, the t object in create_table is actually of this type:

class SomeMigration < ActiveRecord::Migration[6.0]
  def up
    create_table :foo do |t|
      puts t.class  # => "ActiveRecord::ConnectionAdapters::TableDefinition"
    end
  end

  def down
    #...
  end
end

ColumnMethods - Attributes & Methods

Class Method Summary

Instance Attribute Summary

Instance Method Summary

ColumnMethods - Included

#column

Appends a column or columns of a specified type.
#primary_key

Appends a primary key definition to the table definition.

Constructor Details

.new(conn, name, temporary: false, if_not_exists: false, options: nil, as: nil, comment: nil) ⇒ TableDefinition

[ GitHub ] 

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 301



def initialize(
  conn,
  name,
  temporary: false,
  if_not_exists: false,
  options: nil,
  as: nil,
  comment: nil,
  **
)
  @conn = conn
  @columns_hash = {}
  @indexes = []
  @foreign_keys = []
  @primary_keys = nil
  @check_constraints = []
  @temporary = temporary
  @if_not_exists = if_not_exists
  @options = options
  @as = as
  @name = name
  @comment = comment
end


  







Instance Attribute Details



  

    #as   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 299



attr_reader :name, :temporary, :if_not_exists, :options, :as, :comment, :indexes, :foreign_keys, :check_constraints


  








  

    #check_constraints   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 299



attr_reader :name, :temporary, :if_not_exists, :options, :as, :comment, :indexes, :foreign_keys, :check_constraints


  








  

    #comment   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 299



attr_reader :name, :temporary, :if_not_exists, :options, :as, :comment, :indexes, :foreign_keys, :check_constraints


  








  

    #foreign_keys   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 299



attr_reader :name, :temporary, :if_not_exists, :options, :as, :comment, :indexes, :foreign_keys, :check_constraints


  








  

    #if_not_exists   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 299



attr_reader :name, :temporary, :if_not_exists, :options, :as, :comment, :indexes, :foreign_keys, :check_constraints


  








  

    #indexes   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 299



attr_reader :name, :temporary, :if_not_exists, :options, :as, :comment, :indexes, :foreign_keys, :check_constraints


  








  

    #name   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 299



attr_reader :name, :temporary, :if_not_exists, :options, :as, :comment, :indexes, :foreign_keys, :check_constraints


  








  

    #options   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 299



attr_reader :name, :temporary, :if_not_exists, :options, :as, :comment, :indexes, :foreign_keys, :check_constraints


  








  

    #temporary   (readonly)
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 299



attr_reader :name, :temporary, :if_not_exists, :options, :as, :comment, :indexes, :foreign_keys, :check_constraints


  







Instance Method Details



  

    #[](name)  
  



  

    

Returns a ColumnDefinition for the column with name #name.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 334



def [](name)
  @columns_hash[name.to_s]
end


  








  

    #belongs_to(*args, **options)  
  



  

    

Alias for #references.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 476



alias :belongs_to :references


  








  

    #check_constraint(expression, **options)  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 445



def check_constraint(expression, **options)
  check_constraints << [expression, options]
end


  








  

    #column(name, type, index: nil, **options)  
  



  

    

Instantiates a new column for the table. See connection.add_column for available options.



Additional options are:


  • 

    :index - Create an index for the column. Can be either true or an options hash.
    




This method returns self.



Examples



# Assuming {td} is an instance of TableDefinition
td.column(:granted, :boolean, index: true)



Short-hand examples



Instead of calling #column directly, you can also work with the short-hand definitions for the default types. They use the type as the method name instead of as a parameter and allow for multiple columns to be defined in a single statement.



What can be written like this with the regular calls to column:



create_table :products do |t|
  t.column :shop_id,     :integer
  t.column :creator_id,  :integer
  t.column :item_number, :string
  t.column :name,        :string, default: "Untitled"
  t.column :value,       :string, default: "Untitled"
  t.column :created_at,  :datetime
  t.column :updated_at,  :datetime
end
add_index :products, :item_number



can also be written as follows using the short-hand:



create_table :products do |t|
  t.integer :shop_id, :creator_id
  t.string  :item_number, index: true
  t.string  :name, :value, default: "Untitled"
  t.timestamps null: false
end



There’s a short-hand method for each of the type values declared at the top. And then there’s #timestamps that’ll add created_at and updated_at as datetimes.



#references will add an appropriately-named _id column, plus a corresponding _type column if the :polymorphic option is supplied. If :polymorphic is a hash of options, these will be used when creating the _type column. The :index option will also create an index, similar to calling add_index. So what can be written like this:



create_table :taggings do |t|
  t.integer :tag_id, :tagger_id, :taggable_id
  t.string  :tagger_type
  t.string  :taggable_type, default: 'Photo'
end
add_index :taggings, :tag_id, name: 'index_taggings_on_tag_id'
add_index :taggings, [:tagger_id, :tagger_type]



Can also be written as follows using references:



create_table :taggings do |t|
  t.references :tag, index: { name: 'index_taggings_on_tag_id' }
  t.references :tagger, polymorphic: true
  t.references :taggable, polymorphic: { default: 'Photo' }, index: false
end


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 405



def column(name, type, index: nil, **options)
  name = name.to_s
  type = type.to_sym if type

  if @columns_hash[name]
    if @columns_hash[name].primary_key?
      raise ArgumentError, "you can't redefine the primary key column '#{name}'. To define a custom primary key, pass { id: false } to create_table."
    else
      raise ArgumentError, "you can't define an already defined column '#{name}'."
    end
  end

  @columns_hash[name] = new_column_definition(name, type, **options)

  if index
    index_options = index.is_a?(Hash) ? index : {}
    index(name, **index_options)
  end

  self
end


  








  

    #columns  
  



  

    

Returns an array of ColumnDefinition objects for the columns of the table.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 331



def columns; @columns_hash.values; end


  








  

    #index(column_name, **options)  
  



  

    

Adds index options to the indexes hash, keyed by column name This is primarily used to track indexes that need to be created after the table



index(:, name: 'index_projects_on_account_id')


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 437



def index(column_name, **options)
  indexes << [column_name, options]
end


  








  

    #numeric  
  

  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 260



alias :numeric :decimal


  








  

    #references(*args, **options)  
    Also known as: #belongs_to
  



  

    

Adds a reference.



t.references(:user)
t.belongs_to(:supplier, foreign_key: true)
t.belongs_to(:supplier, foreign_key: true, type: :integer)



See connection.add_reference for details of the options you can use.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 471



def references(*args, **options)
  args.each do |ref_name|
    ReferenceDefinition.new(ref_name, **options).add_to(self)
  end
end


  








  

    #remove_column(name)  
  



  

    

remove the column #name from the table.



remove_column(:)


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 429



def remove_column(name)
  @columns_hash.delete name.to_s
end


  








  

    #timestamps(**options)  
  



  

    

Appends :datetime columns :created_at and :updated_at to the table. See connection.add_timestamps



t.timestamps null: false


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb', line 453



def timestamps(**options)
  options[:null] = false if options[:null].nil?

  if !options.key?(:precision) && @conn.supports_datetime_with_precision?
    options[:precision] = 6
  end

  column(:created_at, :datetime, **options)
  column(:updated_at, :datetime, **options)
end