Module: ActiveRecord::ConnectionAdapters::SchemaStatements

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

Instance Method Summary collapse

Instance Method Details

#add_check_constraint(table_name, expression, if_not_exists: false, **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>.

:if_not_exists

Silently ignore if the constraint already exists, rather than raise an error.

:validate

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



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1293

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

  options = check_constraint_options(table_name, expression, options)
  return if if_not_exists && check_constraint_exists?(table_name, **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..65], :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)



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 636

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:



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 643

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 composite foreign key
Assuming "carts" table has "(shop_id, user_id)" as a primary key.

add_foreign_key :orders, :carts, primary_key: [:shop_id, :user_id]

generates:

ALTER TABLE "orders" ADD CONSTRAINT fk_rails_6f5e4cb3a4 FOREIGN KEY ("cart_shop_id", "cart_user_id") REFERENCES "carts" ("shop_id", "user_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". Pass an array to create a composite foreign key.

:primary_key

The primary key column name on to_table. Defaults to id. Pass an array to create a composite foreign key.

: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.



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1173

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 where NULLs are treated equally
add_index(:people, :last_name, nulls_not_distinct: true)

generates:

CREATE INDEX index_people_on_last_name ON people (last_name) NULLS NOT DISTINCT

Note: only supported by PostgreSQL version 15.0.0 and greater.

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) -- PostgreSQL

add_index(:developers, :name, algorithm: :inplace)
# CREATE INDEX `index_developers_on_name` ON `developers` (`name`) ALGORITHM = INPLACE -- MySQL

Note: only supported by PostgreSQL and MySQL.

Concurrently adding an index is not supported in a transaction.

For more information see the “Transactional Migrations” section.



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 915

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:



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1470

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, :nulls_not_distinct)

  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],
    nulls_not_distinct: options[:nulls_not_distinct],
    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.

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 })



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1063

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)



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1453

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 



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1358

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

  migration_context = pool.migration_context
  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.



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 654

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) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 738

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.



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 925

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.



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 408

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) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 333

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:



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1549

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) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 711

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) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1531

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) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 729

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) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 758

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.



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

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) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1521

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) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1342

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:



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1305

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) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1273

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) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 132

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.



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 107

def columns(table_name)
  table_name = table_name.to_s
  definitions = column_definitions(table_name)
  definitions.map do |field|
    new_column_from_field(table_name, field, definitions)
  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"])



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1419

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)

# Creates a table called 'paper_boxes_papers' with no id.
create_join_table('papers', 'paper_boxes')

A duplicate prefix is combined into a single prefix. This is useful for namespaced models like Music::Artist and Music::Record:

# Creates a table called 'music_artists_records' with no id.
create_join_table('music_artists', 'music_records')

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



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 389

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:



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1535

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.



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 293

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]

  if force && options.key?(:if_not_exists)
    raise ArgumentError, "Options `:force` and `:if_not_exists` cannot be used simultaneously."
  end

  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) 


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# File '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.



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# File '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:



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1423

def distinct_relation_for_primary_key(relation) # :nodoc:
  primary_key_columns = Array(relation.primary_key).map do |column|
    visitor.compile(relation.table[column])
  end

  values = columns_for_distinct(
    primary_key_columns,
    relation.order_values
  )

  limited = relation.reselect(values).distinct!
  limited_ids = select_rows(limited.arel, "SQL").map do |results|
    results.last(Array(relation.primary_key).length) # ignores order values for MySQL and PostgreSQL
  end

  if limited_ids.empty?
    relation.none!
  else
    relation.where!(**Array(relation.primary_key).zip(limited_ids.transpose).to_h)
  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.



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 427

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_names, **options) ⇒ Object

Drops a table or tables 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 except if you provide more than one table which is not supported.



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 540

def drop_table(*table_names, **options)
  table_names.each do |table_name|
    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
end

#dump_schema_information ⇒ Object

:nodoc:



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1349

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

#foreign_key_column_for(table_name, column_name) ⇒ Object

:nodoc:



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1241

def foreign_key_column_for(table_name, column_name) # :nodoc:
  name = strip_table_name_prefix_and_suffix(table_name)
  "#{name.singularize}_#{column_name}"
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) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1237

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:



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1246

def foreign_key_options(from_table, to_table, options) # :nodoc:
  options = options.dup

  if options[:primary_key].is_a?(Array)
    options[:column] ||= options[:primary_key].map do |pk_column|
      foreign_key_column_for(to_table, pk_column)
    end
  else
    options[:column] ||= foreign_key_column_for(to_table, "id")
  end

  options[:name]   ||= foreign_key_name(from_table, options)

  if options[:column].is_a?(Array) || options[:primary_key].is_a?(Array)
    if Array(options[:primary_key]).size != Array(options[:column]).size
      raise ArgumentError, <<~MSG.squish
        For composite primary keys, specify :column and :primary_key, where
        :column must reference all the :primary_key columns from #{to_table.inspect}
      MSG
    end
  end

  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) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1103

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

#index_algorithm(algorithm) ⇒ Object

:nodoc:



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1498

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) 


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# File '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:



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 992

def index_name(table_name, options) # :nodoc:
  if Hash === options
    if options[:column]
      if options[:_uses_legacy_index_name]
        "index_#{table_name}_on_#{Array(options[:column]) * '_and_'}"
      else
        generate_index_name(table_name, options[:column])
      end
    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) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1011

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) 


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# File '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:



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

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.



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1587

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.



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

def native_database_types
  {}
end

#options_include_default?(options) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1511

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



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 145

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:



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

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, if_exists: false, **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.



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1324

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

  return if 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)



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 699

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)



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 675

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.



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1214

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.



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 966

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 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)



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1082

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)



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

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) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 766

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'



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 980

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) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 524

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.



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1545

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.



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# File '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.



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# File '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) 


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# File '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 



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# File '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.



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# File '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:



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1379

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:



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

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

#use_foreign_keys? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1539

def use_foreign_keys?
  supports_foreign_keys? && foreign_keys_enabled?
end

#valid_column_definition_options ⇒ Object

:nodoc:



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1578

def valid_column_definition_options # :nodoc:
  ColumnDefinition::OPTION_NAMES
end

#valid_primary_key_options ⇒ Object

:nodoc:



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1582

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

#valid_table_definition_options ⇒ Object

:nodoc:



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# File 'lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1574

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) 


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# File '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.



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

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