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ActiveRecord::ConnectionAdapters::SchemaStatements

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Instance Public methods add_belongs_to(table_name, ref_name, **options) Link add_check_constraint(table_name, expression, if_not_exists: false, **options) Link

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.

Source: show | on GitHub

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) Link

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):

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:

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)

Source: show | on GitHub

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_foreign_key(from_table, to_table, **options) Link

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.

Source: show | on GitHub

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) Link

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.

Source: show | on GitHub

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_reference(table_name, ref_name, **options) Link

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 })

Source: show | on GitHub

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

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)

Source: show | on GitHub

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) Link

Source: show | on GitHub

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_create_table_definition(table_name, id: :primary_key, primary_key: nil, force: nil, **options) Link

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.

Source: show | on GitHub

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
change_column(table_name, column_name, type, **options) Link

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)

Source: show | on GitHub

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) Link

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")
change_column_default(table_name, column_name, default_or_changes) Link

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")

Source: show | on GitHub

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) Link

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.

Source: show | on GitHub

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) Link

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.

Source: show | on GitHub

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

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")
check_constraint_exists?(table_name, **options) Link

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

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

Source: show | on GitHub

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_constraints(table_name) Link

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

Source: show | on GitHub

def check_constraints(table_name)
  raise NotImplementedError
end
column_exists?(table_name, column_name, type = nil, **options) Link

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)

Source: show | on GitHub

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) Link

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

Source: show | on GitHub

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
create_join_table(table_1, table_2, column_options: {}, **options) Link

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

Source: show | on GitHub

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_table(table_name, id: :primary_key, primary_key: nil, force: nil, **options, &block) Link

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.

Source: show | on GitHub

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) Link

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

data_source_exists?(:ebooks)

Source: show | on GitHub

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() Link

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

Source: show | on GitHub

def data_sources
  query_values(data_source_sql, "SCHEMA")
rescue NotImplementedError
  tables | views
end
drop_join_table(table_1, table_2, **options) Link

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.

Source: show | on GitHub

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) Link

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.

Source: show | on GitHub

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
foreign_key_exists?(from_table, to_table = nil, **options) Link

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")

Source: show | on GitHub

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

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

Source: show | on GitHub

def foreign_keys(table_name)
  raise NotImplementedError, "foreign_keys is not implemented"
end
index_exists?(table_name, column_name, **options) Link

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)

Source: show | on GitHub

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

Verifies the existence of an index with a given name.

Source: show | on GitHub

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) Link

Returns an array of indexes for the given table.

Source: show | on GitHub

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

Returns the maximum length of an index name in bytes.

native_database_types() Link

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.

options_include_default?(options) Link

Source: show | on GitHub

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

Returns just a table’s primary key

Source: show | on GitHub

def primary_key(table_name)
  pk = primary_keys(table_name)
  pk = pk.first unless pk.size > 1
  pk
end
remove_belongs_to(table_name, ref_name, foreign_key: false, polymorphic: false, **options) Link remove_check_constraint(table_name, expression = nil, if_exists: false, **options) Link

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.

Source: show | on GitHub

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) Link

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 removed.

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

Source: show | on GitHub

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) Link

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)

Source: show | on GitHub

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) Link

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.

Source: show | on GitHub

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) Link

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.

Source: show | on GitHub

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) Link

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)

Source: show | on GitHub

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) Link

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

remove_timestamps(:suppliers)

Source: show | on GitHub

def remove_timestamps(table_name, **options)
  remove_columns table_name, :updated_at, :created_at
end
rename_column(table_name, column_name, new_column_name) Link

Renames a column.

rename_column(:suppliers, :description, :name)

Source: show | on GitHub

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) Link

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'

Source: show | on GitHub

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)

  
  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, **) Link

Renames a table.

rename_table('octopuses', 'octopi')

Source: show | on GitHub

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

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

Source: show | on GitHub

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

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

table_exists?(table_name) Link

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

table_exists?(:developers)

Source: show | on GitHub

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) Link tables() Link

Returns an array of table names defined in the database.

Source: show | on GitHub

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

Source: show | on GitHub

def use_foreign_keys?
  supports_foreign_keys? && foreign_keys_enabled?
end
view_exists?(view_name) Link

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

view_exists?(:ebooks)

Source: show | on GitHub

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() Link

Returns an array of view names defined in the database.

Source: show | on GitHub

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

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