Module: ActiveRecord::ConnectionAdapters::SchemaStatements

Includes:
Migration::JoinTable
Included in:
AbstractAdapter
Defined in:
activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb

Instance Method Summary collapse

Instance Method Details

#add_check_constraint(table_name, expression, **options) ⇒ Object

Adds a new check constraint to the table. expression is a String representation of verifiable boolean condition.

add_check_constraint :products, "price > 0", name: "price_check"

generates:

ALTER TABLE "products" ADD CONSTRAINT price_check CHECK (price > 0)

The options hash can include the following keys:

:name

The constraint name. Defaults to chk_rails_<identifier>.

:validate

(PostgreSQL only) Specify whether or not the constraint should be validated. Defaults to true.



1229
1230
1231
1232
1233
1234
1235
1236
1237
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1229

def add_check_constraint(table_name, expression, **options)
  return unless supports_check_constraints?

  options = check_constraint_options(table_name, expression, options)
  at = create_alter_table(table_name)
  at.add_check_constraint(expression, options)

  execute schema_creation.accept(at)
end

#add_column(table_name, column_name, type, **options) ⇒ Object

Add a new type column named column_name to table_name.

See ActiveRecord::ConnectionAdapters::TableDefinition.column.

The type parameter is normally one of the migrations native types, which is one of the following: :primary_key, :string, :text, :integer, :bigint, :float, :decimal, :numeric, :datetime, :time, :date, :binary, :blob, :boolean.

You may use a type not in this list as long as it is supported by your database (for example, “polygon” in MySQL), but this will not be database agnostic and should usually be avoided.

Available options are (none of these exists by default):

  • :comment - Specifies the comment for the column. This option is ignored by some backends.

  • :collation - Specifies the collation for a :string or :text column. If not specified, the column will have the same collation as the table.

  • :default - The column’s default value. Use nil for NULL.

  • :limit - Requests a maximum column length. This is the number of characters for a :string column and number of bytes for :text, :binary, :blob, and :integer columns. This option is ignored by some backends.

  • :null - Allows or disallows NULL values in the column.

  • :precision - Specifies the precision for the :decimal, :numeric, :datetime, and :time columns.

  • :scale - Specifies the scale for the :decimal and :numeric columns.

  • :if_not_exists - Specifies if the column already exists to not try to re-add it. This will avoid duplicate column errors.

Note: The precision is the total number of significant digits, and the scale is the number of digits that can be stored following the decimal point. For example, the number 123.45 has a precision of 5 and a scale of 2. A decimal with a precision of 5 and a scale of 2 can range from -999.99 to 999.99.

Please be aware of different RDBMS implementations behavior with :decimal columns:

  • The SQL standard says the default scale should be 0, :scale <= :precision, and makes no comments about the requirements of :precision.

  • MySQL: :precision [1..63], :scale [0..30]. Default is (10,0).

  • PostgreSQL: :precision [1..infinity], :scale [0..infinity]. No default.

  • SQLite3: No restrictions on :precision and :scale, but the maximum supported :precision is 16. No default.

  • Oracle: :precision [1..38], :scale [-84..127]. Default is (38,0).

  • SqlServer: :precision [1..38], :scale [0..38]. Default (38,0).

Examples

add_column(:users, :picture, :binary, limit: 2.megabytes)
# ALTER TABLE "users" ADD "picture" blob(2097152)

add_column(:articles, :status, :string, limit: 20, default: 'draft', null: false)
# ALTER TABLE "articles" ADD "status" varchar(20) DEFAULT 'draft' NOT NULL

add_column(:answers, :bill_gates_money, :decimal, precision: 15, scale: 2)
# ALTER TABLE "answers" ADD "bill_gates_money" decimal(15,2)

add_column(:measurements, :sensor_reading, :decimal, precision: 30, scale: 20)
# ALTER TABLE "measurements" ADD "sensor_reading" decimal(30,20)

# While :scale defaults to zero on most databases, it
# probably wouldn't hurt to include it.
add_column(:measurements, :huge_integer, :decimal, precision: 30)
# ALTER TABLE "measurements" ADD "huge_integer" decimal(30)

# Defines a column that stores an array of a type.
add_column(:users, :skills, :text, array: true)
# ALTER TABLE "users" ADD "skills" text[]

# Defines a column with a database-specific type.
add_column(:shapes, :triangle, 'polygon')
# ALTER TABLE "shapes" ADD "triangle" polygon

# Ignores the method call if the column exists
add_column(:shapes, :triangle, 'polygon', if_not_exists: true)



619
620
621
622
623
624
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 619

def add_column(table_name, column_name, type, **options)
  add_column_def = build_add_column_definition(table_name, column_name, type, **options)
  return unless add_column_def

  execute schema_creation.accept(add_column_def)
end

#add_columns(table_name, *column_names, type:, **options) ⇒ Object

:nodoc:



626
627
628
629
630
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 626

def add_columns(table_name, *column_names, type:, **options) # :nodoc:
  column_names.each do |column_name|
    add_column(table_name, column_name, type, **options)
  end
end

#add_foreign_key(from_table, to_table, **options) ⇒ Object

Adds a new foreign key. from_table is the table with the key column, to_table contains the referenced primary key.

The foreign key will be named after the following pattern: fk_rails_<identifier>. identifier is a 10 character long string which is deterministically generated from the from_table and column. A custom name can be specified with the :name option.

Creating a simple foreign key
add_foreign_key :articles, :authors

generates:

ALTER TABLE "articles" ADD CONSTRAINT fk_rails_e74ce85cbc FOREIGN KEY ("author_id") REFERENCES "authors" ("id")
Creating a foreign key, ignoring method call if the foreign key exists
add_foreign_key(:articles, :authors, if_not_exists: true)
Creating a foreign key on a specific column
add_foreign_key :articles, :users, column: :author_id, primary_key: "lng_id"

generates:

ALTER TABLE "articles" ADD CONSTRAINT fk_rails_58ca3d3a82 FOREIGN KEY ("author_id") REFERENCES "users" ("lng_id")
Creating a cascading foreign key
add_foreign_key :articles, :authors, on_delete: :cascade

generates:

ALTER TABLE "articles" ADD CONSTRAINT fk_rails_e74ce85cbc FOREIGN KEY ("author_id") REFERENCES "authors" ("id") ON DELETE CASCADE

The options hash can include the following keys:

:column

The foreign key column name on from_table. Defaults to to_table.singularize + "_id"

:primary_key

The primary key column name on to_table. Defaults to id.

:name

The constraint name. Defaults to fk_rails_<identifier>.

:on_delete

Action that happens ON DELETE. Valid values are :nullify, :cascade, and :restrict

:on_update

Action that happens ON UPDATE. Valid values are :nullify, :cascade, and :restrict

:if_not_exists

Specifies if the foreign key already exists to not try to re-add it. This will avoid duplicate column errors.

:validate

(PostgreSQL only) Specify whether or not the constraint should be validated. Defaults to true.

:deferrable

(PostgreSQL only) Specify whether or not the foreign key should be deferrable. Valid values are booleans or :deferred or :immediate to specify the default behavior. Defaults to false.



1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1129

def add_foreign_key(from_table, to_table, **options)
  return unless use_foreign_keys?
  return if options[:if_not_exists] == true && foreign_key_exists?(from_table, to_table, **options.slice(:column))

  options = foreign_key_options(from_table, to_table, options)
  at = create_alter_table from_table
  at.add_foreign_key to_table, options

  execute schema_creation.accept(at)
end

#add_index(table_name, column_name, **options) ⇒ Object

Adds a new index to the table. column_name can be a single Symbol, or an Array of Symbols.

The index will be named after the table and the column name(s), unless you pass :name as an option.

Creating a simple index
add_index(:suppliers, :name)

generates:

CREATE INDEX index_suppliers_on_name ON suppliers(name)
Creating a index which already exists
add_index(:suppliers, :name, if_not_exists: true)

generates:

CREATE INDEX IF NOT EXISTS index_suppliers_on_name ON suppliers(name)

Note: Not supported by MySQL.

Creating a unique index
add_index(:accounts, [:branch_id, :party_id], unique: true)

generates:

CREATE UNIQUE INDEX index_accounts_on_branch_id_and_party_id ON accounts(branch_id, party_id)
Creating a named index
add_index(:accounts, [:branch_id, :party_id], unique: true, name: 'by_branch_party')

generates:

CREATE UNIQUE INDEX by_branch_party ON accounts(branch_id, party_id)
Creating an index with specific key length
add_index(:accounts, :name, name: 'by_name', length: 10)

generates:

CREATE INDEX by_name ON accounts(name(10))
Creating an index with specific key lengths for multiple keys
add_index(:accounts, [:name, :surname], name: 'by_name_surname', length: {name: 10, surname: 15})

generates:

CREATE INDEX by_name_surname ON accounts(name(10), surname(15))

Note: only supported by MySQL

Creating an index with a sort order (desc or asc, asc is the default)
add_index(:accounts, [:branch_id, :party_id, :surname], name: 'by_branch_desc_party', order: {branch_id: :desc, party_id: :asc})

generates:

CREATE INDEX by_branch_desc_party ON accounts(branch_id DESC, party_id ASC, surname)

Note: MySQL only supports index order from 8.0.1 onwards (earlier versions accepted the syntax but ignored it).

Creating a partial index
add_index(:accounts, [:branch_id, :party_id], unique: true, where: "active")

generates:

CREATE UNIQUE INDEX index_accounts_on_branch_id_and_party_id ON accounts(branch_id, party_id) WHERE active

Note: Partial indexes are only supported for PostgreSQL and SQLite.

Creating an index that includes additional columns
add_index(:accounts, :branch_id,  include: :party_id)

generates:

CREATE INDEX index_accounts_on_branch_id ON accounts USING btree(branch_id) INCLUDE (party_id)

Note: only supported by PostgreSQL.

Creating an index with a specific method
add_index(:developers, :name, using: 'btree')

generates:

CREATE INDEX index_developers_on_name ON developers USING btree (name) -- PostgreSQL
CREATE INDEX index_developers_on_name USING btree ON developers (name) -- MySQL

Note: only supported by PostgreSQL and MySQL

Creating an index with a specific operator class
add_index(:developers, :name, using: 'gist', opclass: :gist_trgm_ops)
# CREATE INDEX developers_on_name ON developers USING gist (name gist_trgm_ops) -- PostgreSQL

add_index(:developers, [:name, :city], using: 'gist', opclass: { city: :gist_trgm_ops })
# CREATE INDEX developers_on_name_and_city ON developers USING gist (name, city gist_trgm_ops) -- PostgreSQL

add_index(:developers, [:name, :city], using: 'gist', opclass: :gist_trgm_ops)
# CREATE INDEX developers_on_name_and_city ON developers USING gist (name gist_trgm_ops, city gist_trgm_ops) -- PostgreSQL

Note: only supported by PostgreSQL

Creating an index with a specific type
add_index(:developers, :name, type: :fulltext)

generates:

CREATE FULLTEXT INDEX index_developers_on_name ON developers (name) -- MySQL

Note: only supported by MySQL.

Creating an index with a specific algorithm
add_index(:developers, :name, algorithm: :concurrently)
# CREATE INDEX CONCURRENTLY developers_on_name on developers (name)

Note: only supported by PostgreSQL.

Concurrently adding an index is not supported in a transaction.

For more information see the “Transactional Migrations” section.



885
886
887
888
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 885

def add_index(table_name, column_name, **options)
  create_index = build_create_index_definition(table_name, column_name, **options)
  execute schema_creation.accept(create_index)
end

#add_index_options(table_name, column_name, name: nil, if_not_exists: false, internal: false, **options) ⇒ Object

:nodoc:



1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1397

def add_index_options(table_name, column_name, name: nil, if_not_exists: false, internal: false, **options) # :nodoc:
  options.assert_valid_keys(:unique, :length, :order, :opclass, :where, :type, :using, :comment, :algorithm, :include)

  column_names = index_column_names(column_name)

  index_name = name&.to_s
  index_name ||= index_name(table_name, column_names)

  validate_index_length!(table_name, index_name, internal)

  index = IndexDefinition.new(
    table_name, index_name,
    options[:unique],
    column_names,
    lengths: options[:length] || {},
    orders: options[:order] || {},
    opclasses: options[:opclass] || {},
    where: options[:where],
    type: options[:type],
    using: options[:using],
    include: options[:include],
    comment: options[:comment]
  )

  [index, index_algorithm(options[:algorithm]), if_not_exists]
end

#add_reference(table_name, ref_name, **options) ⇒ Object Also known as: add_belongs_to

Adds a reference. The reference column is a bigint by default, the :type option can be used to specify a different type. Optionally adds a _type column, if :polymorphic option is provided. #add_reference and #add_belongs_to are acceptable.

The options hash can include the following keys:

:type

The reference column type. Defaults to :bigint.

:index

Add an appropriate index. Defaults to true. See #add_index for usage of this option.

:foreign_key

Add an appropriate foreign key constraint. Defaults to false, pass true to add. In case the join table can’t be inferred from the association pass :to_table with the appropriate table name.

:polymorphic

Whether an additional _type column should be added. Defaults to false.

:null

Whether the column allows nulls. Defaults to true.

Create a user_id bigint column without an index
add_reference(:products, :user, index: false)
Create a user_id string column
add_reference(:products, :user, type: :string)
Create supplier_id, supplier_type columns
add_reference(:products, :supplier, polymorphic: true)
Create a supplier_id column with a unique index
add_reference(:products, :supplier, index: { unique: true })
Create a supplier_id column with a named index
add_reference(:products, :supplier, index: { name: "my_supplier_index" })
Create a supplier_id column and appropriate foreign key
add_reference(:products, :supplier, foreign_key: true)
Create a supplier_id column and a foreign key to the firms table
add_reference(:products, :supplier, foreign_key: { to_table: :firms })



1030
1031
1032
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1030

def add_reference(table_name, ref_name, **options)
  ReferenceDefinition.new(ref_name, **options).add(table_name, self)
end

#add_timestamps(table_name, **options) ⇒ Object

Adds timestamps (created_at and updated_at) columns to table_name. Additional options (like :null) are forwarded to #add_column.

add_timestamps(:suppliers, null: true)



1380
1381
1382
1383
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1380

def add_timestamps(table_name, **options)
  fragments = add_timestamps_for_alter(table_name, **options)
  execute "ALTER TABLE #{quote_table_name(table_name)} #{fragments.join(', ')}"
end

#assume_migrated_upto_version(version) ⇒ Object 



1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1292

def assume_migrated_upto_version(version)
  version = version.to_i
  sm_table = quote_table_name(schema_migration.table_name)

  migrated = migration_context.get_all_versions
  versions = migration_context.migrations.map(&:version)

  unless migrated.include?(version)
    execute "INSERT INTO #{sm_table} (version) VALUES (#{quote(version)})"
  end

  inserting = (versions - migrated).select { |v| v < version }
  if inserting.any?
    if (duplicate = inserting.detect { |v| inserting.count(v) > 1 })
      raise "Duplicate migration #{duplicate}. Please renumber your migrations to resolve the conflict."
    end
    execute insert_versions_sql(inserting)
  end
end

#build_add_column_definition(table_name, column_name, type, **options) ⇒ Object

Builds an AlterTable object for adding a column to a table.

This definition object contains information about the column that would be created if the same arguments were passed to #add_column. See #add_column for information about passing a table_name, column_name, type and other options that can be passed.



637
638
639
640
641
642
643
644
645
646
647
648
649
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 637

def build_add_column_definition(table_name, column_name, type, **options) # :nodoc:
  return if options[:if_not_exists] == true && column_exists?(table_name, column_name)

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

  alter_table = create_alter_table(table_name)
  alter_table.add_column(column_name, type, **options)
  alter_table
end

#build_change_column_default_definition(table_name, column_name, default_or_changes) ⇒ Object

Builds a ChangeColumnDefaultDefinition object.

This definition object contains information about the column change that would occur if the same arguments were passed to #change_column_default. See #change_column_default for information about passing a table_name, column_name, type and other options that can be passed.

Raises:

  • (NotImplementedError) 


721
722
723
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 721

def build_change_column_default_definition(table_name, column_name, default_or_changes) # :nodoc:
  raise NotImplementedError, "build_change_column_default_definition is not implemented"
end

#build_create_index_definition(table_name, column_name, **options) ⇒ Object

Builds a CreateIndexDefinition object.

This definition object contains information about the index that would be created if the same arguments were passed to #add_index. See #add_index for information about passing a table_name, column_name, and other additional options that can be passed.



895
896
897
898
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 895

def build_create_index_definition(table_name, column_name, **options) # :nodoc:
  index, algorithm, if_not_exists = add_index_options(table_name, column_name, **options)
  CreateIndexDefinition.new(index, algorithm, if_not_exists)
end

#build_create_join_table_definition(table_1, table_2, column_options: {}, **options) ⇒ Object

Builds a TableDefinition object for a join table.

This definition object contains information about the table that would be created if the same arguments were passed to #create_join_table. See #create_join_table for information about what arguments should be passed.



393
394
395
396
397
398
399
400
401
402
403
404
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 393

def build_create_join_table_definition(table_1, table_2, column_options: {}, **options) # :nodoc:
  join_table_name = find_join_table_name(table_1, table_2, options)
  column_options.reverse_merge!(null: false, index: false)

  t1_ref, t2_ref = [table_1, table_2].map { |t| reference_name_for_table(t) }

  build_create_table_definition(join_table_name, **options.merge!(id: false)) do |td|
    td.references t1_ref, **column_options
    td.references t2_ref, **column_options
    yield td if block_given?
  end
end

#build_create_table_definition(table_name, id: :primary_key, primary_key: nil, force: nil, **options) {|table_definition| ... } ⇒ Object

Returns a TableDefinition object containing information about the table that would be created if the same arguments were passed to #create_table. See #create_table for information about passing a table_name, and other additional options that can be passed.

Yields:

  • (table_definition) 


327
328
329
330
331
332
333
334
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 327

def build_create_table_definition(table_name, id: :primary_key, primary_key: nil, force: nil, **options)
  table_definition = create_table_definition(table_name, **options.extract!(*valid_table_definition_options, :_skip_validate_options))
  table_definition.set_primary_key(table_name, id, primary_key, **options.extract!(*valid_primary_key_options, :_skip_validate_options))

  yield table_definition if block_given?

  table_definition
end

#bulk_change_table(table_name, operations) ⇒ Object

:nodoc:



1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1475

def bulk_change_table(table_name, operations) # :nodoc:
  sql_fragments = []
  non_combinable_operations = []

  operations.each do |command, args|
    table, arguments = args.shift, args
    method = :"#{command}_for_alter"

    if respond_to?(method, true)
      sqls, procs = Array(send(method, table, *arguments)).partition { |v| v.is_a?(String) }
      sql_fragments.concat(sqls)
      non_combinable_operations.concat(procs)
    else
      execute "ALTER TABLE #{quote_table_name(table_name)} #{sql_fragments.join(", ")}" unless sql_fragments.empty?
      non_combinable_operations.each(&:call)
      sql_fragments = []
      non_combinable_operations = []
      send(command, table, *arguments)
    end
  end

  execute "ALTER TABLE #{quote_table_name(table_name)} #{sql_fragments.join(", ")}" unless sql_fragments.empty?
  non_combinable_operations.each(&:call)
end

#change_column(table_name, column_name, type, **options) ⇒ Object

Changes the column’s definition according to the new options. See TableDefinition#column for details of the options you can use.

change_column(:suppliers, :name, :string, limit: 80)
change_column(:accounts, :description, :text)

Raises:

  • (NotImplementedError) 


694
695
696
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 694

def change_column(table_name, column_name, type, **options)
  raise NotImplementedError, "change_column is not implemented"
end

#change_column_comment(table_name, column_name, comment_or_changes) ⇒ Object

Changes the comment for a column or removes it if nil.

Passing a hash containing :from and :to will make this change reversible in migration:

change_column_comment(:posts, :state, from: "old_comment", to: "new_comment")

Raises:

  • (NotImplementedError) 


1457
1458
1459
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1457

def change_column_comment(table_name, column_name, comment_or_changes)
  raise NotImplementedError, "#{self.class} does not support changing column comments"
end

#change_column_default(table_name, column_name, default_or_changes) ⇒ Object

Sets a new default value for a column:

change_column_default(:suppliers, :qualification, 'new')
change_column_default(:accounts, :authorized, 1)

Setting the default to nil effectively drops the default:

change_column_default(:users, :email, nil)

Passing a hash containing :from and :to will make this change reversible in migration:

change_column_default(:posts, :state, from: nil, to: "draft")

Raises:

  • (NotImplementedError) 


712
713
714
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 712

def change_column_default(table_name, column_name, default_or_changes)
  raise NotImplementedError, "change_column_default is not implemented"
end

#change_column_null(table_name, column_name, null, default = nil) ⇒ Object

Sets or removes a NOT NULL constraint on a column. The null flag indicates whether the value can be NULL. For example

change_column_null(:users, :nickname, false)

says nicknames cannot be NULL (adds the constraint), whereas

change_column_null(:users, :nickname, true)

allows them to be NULL (drops the constraint).

The method accepts an optional fourth argument to replace existing NULLs with some other value. Use that one when enabling the constraint if needed, since otherwise those rows would not be valid.

Please note the fourth argument does not set a column’s default.

Raises:

  • (NotImplementedError) 


741
742
743
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 741

def change_column_null(table_name, column_name, null, default = nil)
  raise NotImplementedError, "change_column_null is not implemented"
end

#change_table(table_name, base = self, **options) ⇒ Object

A block for changing columns in table.

# change_table() yields a Table instance
change_table(:suppliers) do |t|
  t.column :name, :string, limit: 60
  # Other column alterations here
end

The options hash can include the following keys:

:bulk

Set this to true to make this a bulk alter query, such as

ALTER TABLE `users` ADD COLUMN age INT, ADD COLUMN birthdate DATETIME ...

Defaults to false.

Only supported on the MySQL and PostgreSQL adapter, ignored elsewhere.

Add a column
change_table(:suppliers) do |t|
  t.column :name, :string, limit: 60
end
Change type of a column
change_table(:suppliers) do |t|
  t.change :metadata, :json
end
Add 2 integer columns
change_table(:suppliers) do |t|
  t.integer :width, :height, null: false, default: 0
end
Add created_at/updated_at columns
change_table(:suppliers) do |t|
  t.timestamps
end
Add a foreign key column
change_table(:suppliers) do |t|
  t.references :company
end

Creates a company_id(bigint) column.

Add a polymorphic foreign key column
change_table(:suppliers) do |t|
  t.belongs_to :company, polymorphic: true
end

Creates company_type(varchar) and company_id(bigint) columns.

Remove a column
change_table(:suppliers) do |t|
  t.remove :company
end
Remove several columns
change_table(:suppliers) do |t|
  t.remove :company_id
  t.remove :width, :height
end
Remove an index
change_table(:suppliers) do |t|
  t.remove_index :company_id
end

See also Table for details on all of the various column transformations.



495
496
497
498
499
500
501
502
503
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 495

def change_table(table_name, base = self, **options)
  if supports_bulk_alter? && options[:bulk]
    recorder = ActiveRecord::Migration::CommandRecorder.new(self)
    yield update_table_definition(table_name, recorder)
    bulk_change_table(table_name, recorder.commands)
  else
    yield update_table_definition(table_name, base)
  end
end

#change_table_comment(table_name, comment_or_changes) ⇒ Object

Changes the comment for a table or removes it if nil.

Passing a hash containing :from and :to will make this change reversible in migration:

change_table_comment(:posts, from: "old_comment", to: "new_comment")

Raises:

  • (NotImplementedError) 


1447
1448
1449
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1447

def change_table_comment(table_name, comment_or_changes)
  raise NotImplementedError, "#{self.class} does not support changing table comments"
end

#check_constraint_exists?(table_name, **options) ⇒ Boolean

Checks to see if a check constraint exists on a table for a given check constraint definition.

check_constraint_exists?(:products, name: "price_check")

Returns:

  • (Boolean) 


1276
1277
1278
1279
1280
1281
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1276

def check_constraint_exists?(table_name, **options)
  if !options.key?(:name) && !options.key?(:expression)
    raise ArgumentError, "At least one of :name or :expression must be supplied"
  end
  check_constraint_for(table_name, **options).present?
end

#check_constraint_options(table_name, expression, options) ⇒ Object

:nodoc:



1239
1240
1241
1242
1243
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1239

def check_constraint_options(table_name, expression, options) # :nodoc:
  options = options.dup
  options[:name] ||= check_constraint_name(table_name, expression: expression, **options)
  options
end

#check_constraints(table_name) ⇒ Object

Returns an array of check constraints for the given table. The check constraints are represented as CheckConstraintDefinition objects.

Raises:

  • (NotImplementedError) 


1211
1212
1213
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1211

def check_constraints(table_name)
  raise NotImplementedError
end

#column_exists?(table_name, column_name, type = nil, **options) ⇒ Boolean

Checks to see if a column exists in a given table.

# Check a column exists
column_exists?(:suppliers, :name)

# Check a column exists of a particular type
#
# This works for standard non-casted types (eg. string) but is unreliable
# for types that may get cast to something else (eg. char, bigint).
column_exists?(:suppliers, :name, :string)

# Check a column exists with a specific definition
column_exists?(:suppliers, :name, :string, limit: 100)
column_exists?(:suppliers, :name, :string, default: 'default')
column_exists?(:suppliers, :name, :string, null: false)
column_exists?(:suppliers, :tax, :decimal, precision: 8, scale: 2)

Returns:

  • (Boolean) 


131
132
133
134
135
136
137
138
139
140
141
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 131

def column_exists?(table_name, column_name, type = nil, **options)
  column_name = column_name.to_s
  checks = []
  checks << lambda { |c| c.name == column_name }
  checks << lambda { |c| c.type == type.to_sym rescue nil } if type
  column_options_keys.each do |attr|
    checks << lambda { |c| c.send(attr) == options[attr] } if options.key?(attr)
  end

  columns(table_name).any? { |c| checks.all? { |check| check[c] } }
end

#columns(table_name) ⇒ Object

Returns an array of Column objects for the table specified by table_name.



107
108
109
110
111
112
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 107

def columns(table_name)
  table_name = table_name.to_s
  column_definitions(table_name).map do |field|
    new_column_from_field(table_name, field)
  end
end

#columns_for_distinct(columns, orders) ⇒ Object

Given a set of columns and an ORDER BY clause, returns the columns for a SELECT DISTINCT. PostgreSQL, MySQL, and Oracle override this for custom DISTINCT syntax - they require the order columns appear in the SELECT.

columns_for_distinct("posts.id", ["posts.created_at desc"])



1352
1353
1354
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1352

def columns_for_distinct(columns, orders) # :nodoc:
  columns
end

#create_join_table(table_1, table_2, column_options: {}, **options) ⇒ Object

Creates a new join table with the name created using the lexical order of the first two arguments. These arguments can be a String or a Symbol.

# Creates a table called 'assemblies_parts' with no id.
create_join_table(:assemblies, :parts)

You can pass an options hash which can include the following keys:

:table_name

Sets the table name, overriding the default.

:column_options

Any extra options you want appended to the columns definition.

:options

Any extra options you want appended to the table definition.

:temporary

Make a temporary table.

:force

Set to true to drop the table before creating it. Defaults to false.

Note that #create_join_table does not create any indices by default; you can use its block form to do so yourself:

create_join_table :products, :categories do |t|
  t.index :product_id
  t.index :category_id
end
Add a backend specific option to the generated SQL (MySQL)
create_join_table(:assemblies, :parts, options: 'ENGINE=InnoDB DEFAULT CHARSET=utf8')

generates:

CREATE TABLE assemblies_parts (
  assembly_id bigint NOT NULL,
  part_id bigint NOT NULL,
) ENGINE=InnoDB DEFAULT CHARSET=utf8



374
375
376
377
378
379
380
381
382
383
384
385
386
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 374

def create_join_table(table_1, table_2, column_options: {}, **options)
  join_table_name = find_join_table_name(table_1, table_2, options)

  column_options.reverse_merge!(null: false, index: false)

  t1_ref, t2_ref = [table_1, table_2].map { |t| reference_name_for_table(t) }

  create_table(join_table_name, **options.merge!(id: false)) do |td|
    td.references t1_ref, **column_options
    td.references t2_ref, **column_options
    yield td if block_given?
  end
end

#create_schema_dumper(options) ⇒ Object

:nodoc:



1461
1462
1463
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1461

def create_schema_dumper(options) # :nodoc:
  SchemaDumper.create(self, options)
end

#create_table(table_name, id: :primary_key, primary_key: nil, force: nil, **options, &block) ⇒ Object

Creates a new table with the name table_name. table_name may either be a String or a Symbol.

There are two ways to work with #create_table. You can use the block form or the regular form, like this:

Block form

# create_table() passes a TableDefinition object to the block.
# This form will not only create the table, but also columns for the
# table.

create_table(:suppliers) do |t|
  t.column :name, :string, limit: 60
  # Other fields here
end

Block form, with shorthand

# You can also use the column types as method calls, rather than calling the column method.
create_table(:suppliers) do |t|
  t.string :name, limit: 60
  # Other fields here
end

Regular form

# Creates a table called 'suppliers' with no columns.
create_table(:suppliers)
# Add a column to 'suppliers'.
add_column(:suppliers, :name, :string, {limit: 60})

The options hash can include the following keys:

:id

Whether to automatically add a primary key column. Defaults to true. Join tables for ActiveRecord::Base.has_and_belongs_to_many should set it to false.

A Symbol can be used to specify the type of the generated primary key column.

:primary_key

The name of the primary key, if one is to be added automatically. Defaults to id. If :id is false, then this option is ignored.

If an array is passed, a composite primary key will be created.

Note that Active Record models will automatically detect their primary key. This can be avoided by using self.primary_key= on the model to define the key explicitly.

:options

Any extra options you want appended to the table definition.

:temporary

Make a temporary table.

:force

Set to true to drop the table before creating it. Set to :cascade to drop dependent objects as well. Defaults to false.

:if_not_exists

Set to true to avoid raising an error when the table already exists. Defaults to false.

:as

SQL to use to generate the table. When this option is used, the block is ignored, as are the :id and :primary_key options.

Add a backend specific option to the generated SQL (MySQL)
create_table(:suppliers, options: 'ENGINE=InnoDB DEFAULT CHARSET=utf8mb4')

generates:

CREATE TABLE suppliers (
  id bigint auto_increment PRIMARY KEY
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4
Rename the primary key column
create_table(:objects, primary_key: 'guid') do |t|
  t.column :name, :string, limit: 80
end

generates:

CREATE TABLE objects (
  guid bigint auto_increment PRIMARY KEY,
  name varchar(80)
)
Change the primary key column type
create_table(:tags, id: :string) do |t|
  t.column :label, :string
end

generates:

CREATE TABLE tags (
  id varchar PRIMARY KEY,
  label varchar
)
Create a composite primary key
create_table(:orders, primary_key: [:product_id, :client_id]) do |t|
  t.belongs_to :product
  t.belongs_to :client
end

generates:

CREATE TABLE orders (
    product_id bigint NOT NULL,
    client_id bigint NOT NULL
);

ALTER TABLE ONLY "orders"
  ADD CONSTRAINT orders_pkey PRIMARY KEY (product_id, client_id);
Do not add a primary key column
create_table(:categories_suppliers, id: false) do |t|
  t.column :category_id, :bigint
  t.column :supplier_id, :bigint
end

generates:

CREATE TABLE categories_suppliers (
  category_id bigint,
  supplier_id bigint
)
Create a temporary table based on a query
create_table(:long_query, temporary: true,
  as: "SELECT * FROM orders INNER JOIN line_items ON order_id=orders.id")

generates:

CREATE TEMPORARY TABLE long_query AS
  SELECT * FROM orders INNER JOIN line_items ON order_id=orders.id

See also TableDefinition#column for details on how to create columns.



292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 292

def create_table(table_name, id: :primary_key, primary_key: nil, force: nil, **options, &block)
  validate_create_table_options!(options)
  validate_table_length!(table_name) unless options[:_uses_legacy_table_name]
  td = build_create_table_definition(table_name, id: id, primary_key: primary_key, force: force, **options, &block)

  if force
    drop_table(table_name, force: force, if_exists: true)
  else
    schema_cache.clear_data_source_cache!(table_name.to_s)
  end

  result = execute schema_creation.accept(td)

  unless supports_indexes_in_create?
    td.indexes.each do |column_name, index_options|
      add_index(table_name, column_name, **index_options, if_not_exists: td.if_not_exists)
    end
  end

  if supports_comments? && !supports_comments_in_create?
    if table_comment = td.comment.presence
      change_table_comment(table_name, table_comment)
    end

    td.columns.each do |column|
      change_column_comment(table_name, column.name, column.comment) if column.comment.present?
    end
  end

  result
end

#data_source_exists?(name) ⇒ Boolean

Checks to see if the data source name exists on the database.

data_source_exists?(:ebooks)

Returns:

  • (Boolean) 


44
45
46
47
48
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 44

def data_source_exists?(name)
  query_values(data_source_sql(name), "SCHEMA").any? if name.present?
rescue NotImplementedError
  data_sources.include?(name.to_s)
end

#data_sources ⇒ Object

Returns the relation names usable to back Active Record models. For most adapters this means all #tables and #views.



34
35
36
37
38
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 34

def data_sources
  query_values(data_source_sql, "SCHEMA")
rescue NotImplementedError
  tables | views
end

#distinct_relation_for_primary_key(relation) ⇒ Object

:nodoc:



1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1356

def distinct_relation_for_primary_key(relation) # :nodoc:
  values = columns_for_distinct(
    visitor.compile(relation.table[relation.primary_key]),
    relation.order_values
  )

  limited = relation.reselect(values).distinct!
  limited_ids = select_rows(limited.arel, "SQL").map(&:last)

  if limited_ids.empty?
    relation.none!
  else
    relation.where!(relation.primary_key => limited_ids)
  end

  relation.limit_value = relation.offset_value = nil
  relation
end

#drop_join_table(table_1, table_2, **options) ⇒ Object

Drops the join table specified by the given arguments. See #create_join_table and #drop_table for details.

Although this command ignores the block if one is given, it can be helpful to provide one in a migration’s change method so it can be reverted. In that case, the block will be used by #create_join_table.



412
413
414
415
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 412

def drop_join_table(table_1, table_2, **options)
  join_table_name = find_join_table_name(table_1, table_2, options)
  drop_table(join_table_name, **options)
end

#drop_table(table_name, **options) ⇒ Object

Drops a table from the database.

:force

Set to :cascade to drop dependent objects as well. Defaults to false.

:if_exists

Set to true to only drop the table if it exists. Defaults to false.

Although this command ignores most options and the block if one is given, it can be helpful to provide these in a migration’s change method so it can be reverted. In that case, options and the block will be used by #create_table.



525
526
527
528
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 525

def drop_table(table_name, **options)
  schema_cache.clear_data_source_cache!(table_name.to_s)
  execute "DROP TABLE#{' IF EXISTS' if options[:if_exists]} #{quote_table_name(table_name)}"
end

#dump_schema_information ⇒ Object

:nodoc:



1283
1284
1285
1286
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1283

def dump_schema_information # :nodoc:
  versions = schema_migration.versions
  insert_versions_sql(versions) if versions.any?
end

#foreign_key_column_for(table_name) ⇒ Object

:nodoc:



1197
1198
1199
1200
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1197

def foreign_key_column_for(table_name) # :nodoc:
  name = strip_table_name_prefix_and_suffix(table_name)
  "#{name.singularize}_id"
end

#foreign_key_exists?(from_table, to_table = nil, **options) ⇒ Boolean

Checks to see if a foreign key exists on a table for a given foreign key definition.

# Checks to see if a foreign key exists.
foreign_key_exists?(:accounts, :branches)

# Checks to see if a foreign key on a specified column exists.
foreign_key_exists?(:accounts, column: :owner_id)

# Checks to see if a foreign key with a custom name exists.
foreign_key_exists?(:accounts, name: "special_fk_name")

Returns:

  • (Boolean) 


1193
1194
1195
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1193

def foreign_key_exists?(from_table, to_table = nil, **options)
  foreign_key_for(from_table, to_table: to_table, **options).present?
end

#foreign_key_options(from_table, to_table, options) ⇒ Object

:nodoc:



1202
1203
1204
1205
1206
1207
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1202

def foreign_key_options(from_table, to_table, options) # :nodoc:
  options = options.dup
  options[:column] ||= foreign_key_column_for(to_table)
  options[:name]   ||= foreign_key_name(from_table, options)
  options
end

#foreign_keys(table_name) ⇒ Object

Returns an array of foreign keys for the given table. The foreign keys are represented as ForeignKeyDefinition objects.

Raises:

  • (NotImplementedError) 


1071
1072
1073
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1071

def foreign_keys(table_name)
  raise NotImplementedError, "foreign_keys is not implemented"
end

#index_algorithm(algorithm) ⇒ Object

:nodoc:



1424
1425
1426
1427
1428
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1424

def index_algorithm(algorithm) # :nodoc:
  index_algorithms.fetch(algorithm) do
    raise ArgumentError, "Algorithm must be one of the following: #{index_algorithms.keys.map(&:inspect).join(', ')}"
  end if algorithm
end

#index_exists?(table_name, column_name, **options) ⇒ Boolean

Checks to see if an index exists on a table for a given index definition.

# Check an index exists
index_exists?(:suppliers, :company_id)

# Check an index on multiple columns exists
index_exists?(:suppliers, [:company_id, :company_type])

# Check a unique index exists
index_exists?(:suppliers, :company_id, unique: true)

# Check an index with a custom name exists
index_exists?(:suppliers, :company_id, name: "idx_company_id")

# Check a valid index exists (PostgreSQL only)
index_exists?(:suppliers, :company_id, valid: true)

Returns:

  • (Boolean) 


102
103
104
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 102

def index_exists?(table_name, column_name, **options)
  indexes(table_name).any? { |i| i.defined_for?(column_name, **options) }
end

#index_name(table_name, options) ⇒ Object

:nodoc:



962
963
964
965
966
967
968
969
970
971
972
973
974
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 962

def index_name(table_name, options) # :nodoc:
  if Hash === options
    if options[:column]
      generate_index_name(table_name, options[:column])
    elsif options[:name]
      options[:name]
    else
      raise ArgumentError, "You must specify the index name"
    end
  else
    index_name(table_name, index_name_options(options))
  end
end

#index_name_exists?(table_name, index_name) ⇒ Boolean

Verifies the existence of an index with a given name.

Returns:

  • (Boolean) 


977
978
979
980
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 977

def index_name_exists?(table_name, index_name)
  index_name = index_name.to_s
  indexes(table_name).detect { |i| i.name == index_name }
end

#indexes(table_name) ⇒ Object

Returns an array of indexes for the given table.

Raises:

  • (NotImplementedError) 


81
82
83
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 81

def indexes(table_name)
  raise NotImplementedError, "#indexes is not implemented"
end

#internal_string_options_for_primary_key ⇒ Object

:nodoc:



1288
1289
1290
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1288

def internal_string_options_for_primary_key # :nodoc:
  { primary_key: true }
end

#max_index_name_size ⇒ Object

Returns the maximum length of an index name in bytes.



1513
1514
1515
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1513

def max_index_name_size
  62
end

#native_database_types ⇒ Object

Returns a hash of mappings from the abstract data types to the native database types. See TableDefinition#column for details on the recognized abstract data types.



14
15
16
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 14

def native_database_types
  {}
end

#options_include_default?(options) ⇒ Boolean

Returns:

  • (Boolean) 


1437
1438
1439
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1437

def options_include_default?(options)
  options.include?(:default) && !(options[:null] == false && options[:default].nil?)
end

#primary_key(table_name) ⇒ Object

Returns just a table’s primary key



144
145
146
147
148
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 144

def primary_key(table_name)
  pk = primary_keys(table_name)
  pk = pk.first unless pk.size > 1
  pk
end

#quoted_columns_for_index(column_names, options) ⇒ Object

:nodoc:



1430
1431
1432
1433
1434
1435
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1430

def quoted_columns_for_index(column_names, options) # :nodoc:
  quoted_columns = column_names.each_with_object({}) do |name, result|
    result[name.to_sym] = quote_column_name(name).dup
  end
  add_options_for_index_columns(quoted_columns, **options).values.join(", ")
end

#remove_check_constraint(table_name, expression = nil, **options) ⇒ Object

Removes the given check constraint from the table. Removing a check constraint that does not exist will raise an error.

remove_check_constraint :products, name: "price_check"

To silently ignore a non-existent check constraint rather than raise an error, use the if_exists option.

remove_check_constraint :products, name: "price_check", if_exists: true

The expression parameter will be ignored if present. It can be helpful to provide this in a migration’s change method so it can be reverted. In that case, expression will be used by #add_check_constraint.



1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1258

def remove_check_constraint(table_name, expression = nil, **options)
  return unless supports_check_constraints?

  return if options[:if_exists] && !check_constraint_exists?(table_name, **options)

  chk_name_to_delete = check_constraint_for!(table_name, expression: expression, **options).name

  at = create_alter_table(table_name)
  at.drop_check_constraint(chk_name_to_delete)

  execute schema_creation.accept(at)
end

#remove_column(table_name, column_name, type = nil, **options) ⇒ Object

Removes the column from the table definition.

remove_column(:suppliers, :qualification)

The type and options parameters will be ignored if present. It can be helpful to provide these in a migration’s change method so it can be reverted. In that case, type and options will be used by #add_column. Depending on the database you’re using, indexes using this column may be automatically removed or modified to remove this column from the index.

If the options provided include an if_exists key, it will be used to check if the column does not exist. This will silently ignore the migration rather than raising if the column was already used.

remove_column(:suppliers, :qualification, if_exists: true)



682
683
684
685
686
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 682

def remove_column(table_name, column_name, type = nil, **options)
  return if options[:if_exists] == true && !column_exists?(table_name, column_name)

  execute "ALTER TABLE #{quote_table_name(table_name)} #{remove_column_for_alter(table_name, column_name, type, **options)}"
end

#remove_columns(table_name, *column_names, type: nil, **options) ⇒ Object

Removes the given columns from the table definition.

remove_columns(:suppliers, :qualification, :experience)

type and other column options can be passed to make migration reversible.

remove_columns(:suppliers, :qualification, :experience, type: :string, null: false)



658
659
660
661
662
663
664
665
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 658

def remove_columns(table_name, *column_names, type: nil, **options)
  if column_names.empty?
    raise ArgumentError.new("You must specify at least one column name. Example: remove_columns(:people, :first_name)")
  end

  remove_column_fragments = remove_columns_for_alter(table_name, *column_names, type: type, **options)
  execute "ALTER TABLE #{quote_table_name(table_name)} #{remove_column_fragments.join(', ')}"
end

#remove_foreign_key(from_table, to_table = nil, **options) ⇒ Object

Removes the given foreign key from the table. Any option parameters provided will be used to re-add the foreign key in case of a migration rollback. It is recommended that you provide any options used when creating the foreign key so that the migration can be reverted properly.

Removes the foreign key on accounts.branch_id.

remove_foreign_key :accounts, :branches

Removes the foreign key on accounts.owner_id.

remove_foreign_key :accounts, column: :owner_id

Removes the foreign key on accounts.owner_id.

remove_foreign_key :accounts, to_table: :owners

Removes the foreign key named special_fk_name on the accounts table.

remove_foreign_key :accounts, name: :special_fk_name

Checks if the foreign key exists before trying to remove it. Will silently ignore indexes that don’t exist.

remove_foreign_key :accounts, :branches, if_exists: true

The options hash accepts the same keys as SchemaStatements#add_foreign_key with an addition of

:to_table

The name of the table that contains the referenced primary key.



1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1170

def remove_foreign_key(from_table, to_table = nil, **options)
  return unless use_foreign_keys?
  return if options.delete(:if_exists) == true && !foreign_key_exists?(from_table, to_table)

  fk_name_to_delete = foreign_key_for!(from_table, to_table: to_table, **options).name

  at = create_alter_table from_table
  at.drop_foreign_key fk_name_to_delete

  execute schema_creation.accept(at)
end

#remove_index(table_name, column_name = nil, **options) ⇒ Object

Removes the given index from the table.

Removes the index on branch_id in the accounts table if exactly one such index exists.

remove_index :accounts, :branch_id

Removes the index on branch_id in the accounts table if exactly one such index exists.

remove_index :accounts, column: :branch_id

Removes the index on branch_id and party_id in the accounts table if exactly one such index exists.

remove_index :accounts, column: [:branch_id, :party_id]

Removes the index named by_branch_party in the accounts table.

remove_index :accounts, name: :by_branch_party

Removes the index on branch_id named by_branch_party in the accounts table.

remove_index :accounts, :branch_id, name: :by_branch_party

Checks if the index exists before trying to remove it. Will silently ignore indexes that don’t exist.

remove_index :accounts, if_exists: true

Removes the index named by_branch_party in the accounts table concurrently.

remove_index :accounts, name: :by_branch_party, algorithm: :concurrently

Note: only supported by PostgreSQL.

Concurrently removing an index is not supported in a transaction.

For more information see the “Transactional Migrations” section.



936
937
938
939
940
941
942
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 936

def remove_index(table_name, column_name = nil, **options)
  return if options[:if_exists] && !index_exists?(table_name, column_name, **options)

  index_name = index_name_for_remove(table_name, column_name, options)

  execute "DROP INDEX #{quote_column_name(index_name)} ON #{quote_table_name(table_name)}"
end

#remove_reference(table_name, ref_name, foreign_key: false, polymorphic: false, **options) ⇒ Object Also known as: remove_belongs_to

Removes the reference(s). Also removes a type column if one exists. #remove_reference and #remove_belongs_to are acceptable.

Remove the reference
remove_reference(:products, :user, index: false)
Remove polymorphic reference
remove_reference(:products, :supplier, polymorphic: true)
Remove the reference with a foreign key
remove_reference(:products, :user, foreign_key: true)



1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1050

def remove_reference(table_name, ref_name, foreign_key: false, polymorphic: false, **options)
  conditional_options = options.slice(:if_exists, :if_not_exists)

  if foreign_key
    reference_name = Base.pluralize_table_names ? ref_name.to_s.pluralize : ref_name
    if foreign_key.is_a?(Hash)
      foreign_key_options = foreign_key.merge(conditional_options)
    else
      foreign_key_options = { to_table: reference_name, **conditional_options }
    end
    foreign_key_options[:column] ||= "#{ref_name}_id"
    remove_foreign_key(table_name, **foreign_key_options)
  end

  remove_column(table_name, "#{ref_name}_id", **conditional_options)
  remove_column(table_name, "#{ref_name}_type", **conditional_options) if polymorphic
end

#remove_timestamps(table_name, **options) ⇒ Object

Removes the timestamp columns (created_at and updated_at) from the table definition.

remove_timestamps(:suppliers)



1389
1390
1391
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1389

def remove_timestamps(table_name, **options)
  remove_columns table_name, :updated_at, :created_at
end

#rename_column(table_name, column_name, new_column_name) ⇒ Object

Renames a column.

rename_column(:suppliers, :description, :name)

Raises:

  • (NotImplementedError) 


749
750
751
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 749

def rename_column(table_name, column_name, new_column_name)
  raise NotImplementedError, "rename_column is not implemented"
end

#rename_index(table_name, old_name, new_name) ⇒ Object

Renames an index.

Rename the index_people_on_last_name index to index_users_on_last_name:

rename_index :people, 'index_people_on_last_name', 'index_users_on_last_name'



950
951
952
953
954
955
956
957
958
959
960
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 950

def rename_index(table_name, old_name, new_name)
  old_name = old_name.to_s
  new_name = new_name.to_s
  validate_index_length!(table_name, new_name)

  # this is a naive implementation; some DBs may support this more efficiently (PostgreSQL, for instance)
  old_index_def = indexes(table_name).detect { |i| i.name == old_name }
  return unless old_index_def
  add_index(table_name, old_index_def.columns, name: new_name, unique: old_index_def.unique)
  remove_index(table_name, name: old_name)
end

#rename_table(table_name, new_name) ⇒ Object

Renames a table.

rename_table('octopuses', 'octopi')

Raises:

  • (NotImplementedError) 


509
510
511
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 509

def rename_table(table_name, new_name, **)
  raise NotImplementedError, "rename_table is not implemented"
end

#schema_creation ⇒ Object

Returns an instance of SchemaCreation, which can be used to visit a schema definition object and return DDL.



1471
1472
1473
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1471

def schema_creation # :nodoc:
  SchemaCreation.new(self)
end

#table_alias_for(table_name) ⇒ Object

Truncates a table alias according to the limits of the current adapter.



28
29
30
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 28

def table_alias_for(table_name)
  table_name[0...table_alias_length].tr(".", "_")
end

#table_comment(table_name) ⇒ Object

Returns the table comment that’s stored in database metadata.



23
24
25
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 23

def table_comment(table_name)
  nil
end

#table_exists?(table_name) ⇒ Boolean

Checks to see if the table table_name exists on the database.

table_exists?(:developers)

Returns:

  • (Boolean) 


59
60
61
62
63
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 59

def table_exists?(table_name)
  query_values(data_source_sql(table_name, type: "BASE TABLE"), "SCHEMA").any? if table_name.present?
rescue NotImplementedError
  tables.include?(table_name.to_s)
end

#table_options(table_name) ⇒ Object 



18
19
20
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 18

def table_options(table_name)
  nil
end

#tables ⇒ Object

Returns an array of table names defined in the database.



51
52
53
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 51

def tables
  query_values(data_source_sql(type: "BASE TABLE"), "SCHEMA")
end

#type_to_sql(type, limit: nil, precision: nil, scale: nil) ⇒ Object

:nodoc:



1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1312

def type_to_sql(type, limit: nil, precision: nil, scale: nil, **) # :nodoc:
  type = type.to_sym if type
  if native = native_database_types[type]
    column_type_sql = (native.is_a?(Hash) ? native[:name] : native).dup

    if type == :decimal # ignore limit, use precision and scale
      scale ||= native[:scale]

      if precision ||= native[:precision]
        if scale
          column_type_sql << "(#{precision},#{scale})"
        else
          column_type_sql << "(#{precision})"
        end
      elsif scale
        raise ArgumentError, "Error adding decimal column: precision cannot be empty if scale is specified"
      end

    elsif [:datetime, :timestamp, :time, :interval].include?(type) && precision ||= native[:precision]
      if (0..6) === precision
        column_type_sql << "(#{precision})"
      else
        raise ArgumentError, "No #{native[:name]} type has precision of #{precision}. The allowed range of precision is from 0 to 6"
      end
    elsif (type != :primary_key) && (limit ||= native.is_a?(Hash) && native[:limit])
      column_type_sql << "(#{limit})"
    end

    column_type_sql
  else
    type.to_s
  end
end

#update_table_definition(table_name, base) ⇒ Object

:nodoc:



1393
1394
1395
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1393

def update_table_definition(table_name, base) # :nodoc:
  Table.new(table_name, base)
end

#use_foreign_keys? ⇒ Boolean

Returns:

  • (Boolean) 


1465
1466
1467
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1465

def use_foreign_keys?
  supports_foreign_keys? && foreign_keys_enabled?
end

#valid_column_definition_options ⇒ Object

:nodoc:



1504
1505
1506
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1504

def valid_column_definition_options # :nodoc:
  ColumnDefinition::OPTION_NAMES
end

#valid_primary_key_options ⇒ Object

:nodoc:



1508
1509
1510
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1508

def valid_primary_key_options # :nodoc:
  [:limit, :default, :precision]
end

#valid_table_definition_options ⇒ Object

:nodoc:



1500
1501
1502
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1500

def valid_table_definition_options # :nodoc:
  [:temporary, :if_not_exists, :options, :as, :comment, :charset, :collation]
end

#view_exists?(view_name) ⇒ Boolean

Checks to see if the view view_name exists on the database.

view_exists?(:ebooks)

Returns:

  • (Boolean) 


74
75
76
77
78
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 74

def view_exists?(view_name)
  query_values(data_source_sql(view_name, type: "VIEW"), "SCHEMA").any? if view_name.present?
rescue NotImplementedError
  views.include?(view_name.to_s)
end

#views ⇒ Object

Returns an array of view names defined in the database.



66
67
68
 
# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 66

def views
  query_values(data_source_sql(type: "VIEW"), "SCHEMA")
end