# 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
module ActiveRecord::ConnectionAdapters::SchemaStatements
Public Instance Methods
Add a new type
column named column_name
to
table_name
.
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
, :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):
-
:limit
- Requests a maximum column length. This is the number of characters for a:string
column and number of bytes for:text
,:binary
, and:integer
columns. This option is ignored by some backends. -
:default
- The column's default value. Usenil
forNULL
. -
:null
- Allows or disallowsNULL
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. -
:collation
- Specifies the collation for a:string
or:text
column. If not specified, the column will have the same collation as the table. -
:comment
- Specifies the comment for the column. This option is ignored by some backends.
Note: The precision is the total number of significant digits, and the scale is the number of digits that can be stored following the decimal point. For example, the number 123.45 has a precision of 5 and a scale of 2. A decimal with a precision of 5 and a scale of 2 can range from -999.99 to 999.99.
Please be aware of different RDBMS implementations behavior with
:decimal
columns:
-
The SQL standard says the default scale should be 0,
:scale
<=:precision
, and makes no comments about the requirements of:precision
. -
MySQL:
:precision
[1..63],:scale
[0..30]. Default is (10,0). -
PostgreSQL:
:precision
[1..infinity],:scale
[0..infinity]. No default. -
SQLite3: No restrictions on
:precision
and:scale
, but the maximum supported:precision
is 16. No default. -
Oracle:
:precision
[1..38],:scale
[-84..127]. Default is (38,0). -
DB2:
:precision
[1..63],:scale
[0..62]. Default unknown. -
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
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 587 def add_column(table_name, column_name, type, **options) at = create_alter_table table_name at.add_column(column_name, type, **options) execute schema_creation.accept at end
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 on a specific column¶ ↑
add_foreign_key :articles, :users, column: :author_id, primary_key: "lng_id"
generates:
ALTER TABLE "articles" ADD CONSTRAINT fk_rails_58ca3d3a82 FOREIGN KEY ("author_id") REFERENCES "users" ("lng_id")
Creating a cascading foreign key¶ ↑
add_foreign_key :articles, :authors, on_delete: :cascade
generates:
ALTER TABLE "articles" ADD CONSTRAINT fk_rails_e74ce85cbc FOREIGN KEY ("author_id") REFERENCES "authors" ("id") ON DELETE CASCADE
The options
hash can include the following keys:
:column
-
The foreign key column name on
from_table
. Defaults toto_table.singularize + "_id"
:primary_key
-
The primary key column name on
to_table
. Defaults toid
. :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
:validate
-
(PostgreSQL only) Specify whether or not the constraint should be validated. Defaults to
true
.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 990 def add_foreign_key(from_table, to_table, **options) return unless supports_foreign_keys? 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
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 suppliers_name_index ON suppliers(name)
Creating a unique index¶ ↑
add_index(:accounts, [:branch_id, :party_id], unique: true)
generates:
CREATE UNIQUE INDEX accounts_branch_id_party_id_index 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: SQLite doesn't support index length.
Creating an index with a sort order (desc or asc, asc is the default)¶ ↑
add_index(:accounts, [:branch_id, :party_id, :surname], 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 3.8.0+.
Creating an index with a specific method¶ ↑
add_index(:developers, :name, using: 'btree')
generates:
CREATE INDEX index_developers_on_name ON developers USING btree (name) -- PostgreSQL CREATE INDEX index_developers_on_name USING btree ON developers (name) -- MySQL
Note: only supported by PostgreSQL and MySQL
Creating an index with a specific operator class¶ ↑
add_index(:developers, :name, using: 'gist', opclass: :gist_trgm_ops) # CREATE INDEX developers_on_name ON developers USING gist (name gist_trgm_ops) -- PostgreSQL add_index(:developers, [:name, :city], using: 'gist', opclass: { city: :gist_trgm_ops }) # CREATE INDEX developers_on_name_and_city ON developers USING gist (name, city gist_trgm_ops) -- PostgreSQL add_index(:developers, [:name, :city], using: 'gist', opclass: :gist_trgm_ops) # CREATE INDEX developers_on_name_and_city ON developers USING gist (name gist_trgm_ops, city gist_trgm_ops) -- PostgreSQL
Note: only supported by PostgreSQL
Creating an index with a specific type¶ ↑
add_index(:developers, :name, type: :fulltext)
generates:
CREATE FULLTEXT INDEX index_developers_on_name ON developers (name) -- MySQL
Note: only supported by MySQL.
Creating an index with a specific algorithm¶ ↑
add_index(:developers, :name, algorithm: :concurrently) # CREATE INDEX CONCURRENTLY developers_on_name on developers (name)
Note: only supported by PostgreSQL.
Concurrently adding an index is not supported in a transaction.
For more information see the “Transactional Migrations” section.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 784 def add_index(table_name, column_name, options = {}) index_name, index_type, index_columns, index_options = add_index_options(table_name, column_name, **options) execute "CREATE #{index_type} INDEX #{quote_column_name(index_name)} ON #{quote_table_name(table_name)} (#{index_columns})#{index_options}" end
Adds a reference. The reference column is a bigint by default, the
:type
option can be used to specify a different type.
Optionally adds a _type
column, if :polymorphic
option is provided. add_reference and
add_belongs_to
are acceptable.
The options
hash can include the following keys:
:type
-
The reference column type. Defaults to
:bigint
. :index
-
Add an appropriate index. Defaults to true. See add_index for usage of this option.
:foreign_key
-
Add an appropriate foreign key constraint. Defaults to false.
: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})
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 903 def add_reference(table_name, ref_name, **options) ReferenceDefinition.new(ref_name, **options).add_to(update_table_definition(table_name, self)) end
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)
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1147 def add_timestamps(table_name, **options) options[:null] = false if options[:null].nil? if !options.key?(:precision) && supports_datetime_with_precision? options[:precision] = 6 end add_column table_name, :created_at, :datetime, **options add_column table_name, :updated_at, :datetime, **options end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1072 def assume_migrated_upto_version(version, migrations_paths = nil) unless migrations_paths.nil? ActiveSupport::Deprecation.warn(<<~MSG.squish) Passing migrations_paths to #assume_migrated_upto_version is deprecated and will be removed in Rails 6.1. MSG end version = version.to_i sm_table = quote_table_name(schema_migration.table_name) migrated = migration_context.get_all_versions versions = migration_context.migrations.map(&:version) unless migrated.include?(version) execute "INSERT INTO #{sm_table} (version) VALUES (#{quote(version)})" end inserting = (versions - migrated).select { |v| v < version } if inserting.any? if (duplicate = inserting.detect { |v| inserting.count(v) > 1 }) raise "Duplicate migration #{duplicate}. Please renumber your migrations to resolve the conflict." end execute insert_versions_sql(inserting) end end
Changes the column's definition according to the new options. See ActiveRecord::ConnectionAdapters::TableDefinition#column for details of the options you can use.
change_column(:suppliers, :name, :string, limit: 80) change_column(:accounts, :description, :text)
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 622 def change_column(table_name, column_name, type, options = {}) raise NotImplementedError, "change_column is not implemented" end
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")
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1223 def change_column_comment(table_name, column_name, comment_or_changes) raise NotImplementedError, "#{self.class} does not support changing column comments" end
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")
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 640 def change_column_default(table_name, column_name, default_or_changes) raise NotImplementedError, "change_column_default is not implemented" end
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
NULL
s 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.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 660 def change_column_null(table_name, column_name, null, default = nil) raise NotImplementedError, "change_column_null is not implemented" end
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
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.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 470 def change_table(table_name, **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, self) 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")
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1213 def change_table_comment(table_name, comment_or_changes) raise NotImplementedError, "#{self.class} does not support changing table comments" end
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 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)
# 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
Returns an array of Column
objects for the table specified by
table_name
.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 111 def columns(table_name) table_name = table_name.to_s column_definitions(table_name).map do |field| new_column_from_field(table_name, field) end end
Creates a new join table with the name created using the lexical order of the first two arguments. These arguments can be a String or a Symbol.
# Creates a table called 'assemblies_parts' with no id. create_join_table(:assemblies, :parts)
You can pass an options
hash which can include the following
keys:
:table_name
-
Sets the table name, overriding the default.
:column_options
-
Any extra options you want appended to the columns definition.
:options
-
Any extra options you want appended to the table definition.
:temporary
-
Make a temporary table.
:force
-
Set to true to drop the table before creating it. Defaults to false.
Note that create_join_table does not create any indices by default; you can use its block form to do so yourself:
create_join_table :products, :categories do |t| t.index :product_id t.index :category_id end
Add a backend specific option to the generated SQL (MySQL)¶ ↑
create_join_table(:assemblies, :parts, options: 'ENGINE=InnoDB DEFAULT CHARSET=utf8')
generates:
CREATE TABLE assemblies_parts ( assembly_id bigint NOT NULL, part_id bigint NOT NULL, ) ENGINE=InnoDB DEFAULT CHARSET=utf8
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 373 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| t.to_s.singularize } 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
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 order ( 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 ActiveRecord::ConnectionAdapters::TableDefinition#column for details on how to create columns.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 293 def create_table(table_name, **options) td = create_table_definition(table_name, **options) if options[:id] != false && !options[:as] pk = options.fetch(:primary_key) do Base.get_primary_key table_name.to_s.singularize end if pk.is_a?(Array) td.primary_keys pk else td.primary_key pk, options.fetch(:id, :primary_key), **options.except(:comment) end end yield td if block_given? if options[:force] drop_table(table_name, **options, if_exists: true) 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) end end if supports_comments? && !supports_comments_in_create? if table_comment = options[: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
Checks to see if the data source name
exists on the database.
data_source_exists?(:ebooks)
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 45 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
Returns the relation names useable to back Active Record models. For most adapters this means all tables and views.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 35 def data_sources query_values(data_source_sql, "SCHEMA") rescue NotImplementedError tables | views end
Drops the join table specified by the given arguments. See create_join_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.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 393 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) end
Drops a table from the database.
:force
-
Set to
:cascade
to drop dependent objects as well. Defaults to false. :if_exists
-
Set to
true
to only drop the table if it exists. Defaults to false.
Although this command ignores most options
and the block if
one is given, it can be helpful to provide these in a migration's
change
method so it can be reverted. In that case,
options
and the block will be used by create_table.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 500 def drop_table(table_name, **options) execute "DROP TABLE#{' IF EXISTS' if options[:if_exists]} #{quote_table_name(table_name)}" end
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")
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1047 def foreign_key_exists?(from_table, to_table = nil, **options) foreign_key_for(from_table, to_table: to_table, **options).present? end
Returns an array of foreign keys for the given table. The foreign keys are represented as ForeignKeyDefinition objects.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 942 def foreign_keys(table_name) raise NotImplementedError, "foreign_keys is not implemented" end
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")
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 100 def index_exists?(table_name, column_name, options = {}) column_names = Array(column_name).map(&:to_s) checks = [] checks << lambda { |i| Array(i.columns) == column_names } checks << lambda { |i| i.unique } if options[:unique] checks << lambda { |i| i.name == options[:name].to_s } if options[:name] indexes(table_name).any? { |i| checks.all? { |check| check[i] } } end
Verifies the existence of an index with a given name.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 852 def index_name_exists?(table_name, index_name) index_name = index_name.to_s indexes(table_name).detect { |i| i.name == index_name } end
Returns an array of indexes for the given table.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 82 def indexes(table_name) raise NotImplementedError, "#indexes is not implemented" end
Returns a hash of mappings from the abstract data types to the native database types. See ActiveRecord::ConnectionAdapters::TableDefinition#column for details on the recognized abstract data types.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 15 def native_database_types {} end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1203 def options_include_default?(options) options.include?(:default) && !(options[:null] == false && options[:default].nil?) end
Returns just a table's primary key
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. Indexes on
the column are automatically removed.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 612 def remove_column(table_name, column_name, type = nil, **options) execute "ALTER TABLE #{quote_table_name(table_name)} #{remove_column_for_alter(table_name, column_name, type, **options)}" end
Removes the given columns from the table definition.
remove_columns(:suppliers, :qualification, :experience)
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 597 def remove_columns(table_name, *column_names) raise ArgumentError.new("You must specify at least one column name. Example: remove_columns(:people, :first_name)") if column_names.empty? column_names.each do |column_name| remove_column(table_name, column_name) end end
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
The options
hash accepts the same keys as #add_foreign_key
with an addition of
:to_table
-
The name of the table that contains the referenced primary key.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1025 def remove_foreign_key(from_table, to_table = nil, **options) return unless supports_foreign_keys? 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
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 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.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 816 def remove_index(table_name, options = {}) index_name = index_name_for_remove(table_name, options) execute "DROP INDEX #{quote_column_name(index_name)} ON #{quote_table_name(table_name)}" end
Removes the reference(s). Also removes a type
column if one
exists. remove_reference
and remove_belongs_to
are acceptable.
Remove the reference¶ ↑
remove_reference(:products, :user, index: false)
Remove polymorphic reference¶ ↑
remove_reference(:products, :supplier, polymorphic: true)
Remove the reference with a foreign key¶ ↑
remove_reference(:products, :user, foreign_key: true)
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 923 def remove_reference(table_name, ref_name, foreign_key: false, polymorphic: false, **options) 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 else foreign_key_options = { to_table: reference_name } end foreign_key_options[:column] ||= "#{ref_name}_id" remove_foreign_key(table_name, **foreign_key_options) end remove_column(table_name, "#{ref_name}_id") remove_column(table_name, "#{ref_name}_type") if polymorphic end
Removes the timestamp columns (created_at
and
updated_at
) from the table definition.
remove_timestamps(:suppliers)
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1162 def remove_timestamps(table_name, **options) remove_column table_name, :updated_at remove_column table_name, :created_at end
Renames a column.
rename_column(:suppliers, :description, :name)
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 668 def rename_column(table_name, column_name, new_column_name) raise NotImplementedError, "rename_column is not implemented" end
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'
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 827 def rename_index(table_name, old_name, new_name) 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
Renames a table.
rename_table('octopuses', 'octopi')
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 484 def rename_table(table_name, new_name) raise NotImplementedError, "rename_table is not implemented" end
Truncates a table alias according to the limits of the current adapter.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 29 def table_alias_for(table_name) table_name[0...table_alias_length].tr(".", "_") end
Returns the table comment that's stored in database metadata.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 24 def table_comment(table_name) nil end
Checks to see if the table table_name
exists on the database.
table_exists?(:developers)
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 60 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
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 19 def table_options(table_name) nil end
Returns an array of table names defined in the database.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 52 def tables query_values(data_source_sql(type: "BASE TABLE"), "SCHEMA") end
Checks to see if the view view_name
exists on the database.
view_exists?(:ebooks)
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 75 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
Returns an array of view names defined in the database.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 67 def views query_values(data_source_sql(type: "VIEW"), "SCHEMA") end
Private Instance Methods
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1438 def add_column_for_alter(table_name, column_name, type, **options) td = create_table_definition(table_name) cd = td.new_column_definition(column_name, type, **options) schema_creation.accept(AddColumnDefinition.new(cd)) end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1236 def add_index_sort_order(quoted_columns, **options) orders = options_for_index_columns(options[:order]) quoted_columns.each do |name, column| column << " #{orders[name].upcase}" if orders[name].present? end end
Overridden by the MySQL adapter for supporting index lengths and by the PostgreSQL adapter for supporting operator classes.
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1253 def add_options_for_index_columns(quoted_columns, **options) if supports_index_sort_order? quoted_columns = add_index_sort_order(quoted_columns, **options) end quoted_columns end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1452 def add_timestamps_for_alter(table_name, **options) options[:null] = false if options[:null].nil? if !options.key?(:precision) && supports_datetime_with_precision? options[:precision] = 6 end [ add_column_for_alter(table_name, :created_at, :datetime, **options), add_column_for_alter(table_name, :updated_at, :datetime, **options) ] end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1413 def bulk_change_table(table_name, operations) 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 << 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
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1409 def can_remove_index_by_name?(options) options.is_a?(Hash) && options.key?(:name) && options.except(:name, :algorithm).empty? end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1232 def column_options_keys [:limit, :precision, :scale, :default, :null, :collation, :comment] end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1328 def create_alter_table(name) AlterTable.new create_table_definition(name) end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1324 def create_table_definition(*args, **options) TableDefinition.new(self, *args, **options) end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1482 def data_source_sql(name = nil, type: nil) raise NotImplementedError end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1384 def extract_foreign_key_action(specifier) case specifier when "CASCADE"; :cascade when "SET NULL"; :nullify when "RESTRICT"; :restrict end end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1400 def extract_new_default_value(default_or_changes) if default_or_changes.is_a?(Hash) && default_or_changes.has_key?(:from) && default_or_changes.has_key?(:to) default_or_changes[:to] else default_or_changes end end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1332 def fetch_type_metadata(sql_type) cast_type = lookup_cast_type(sql_type) SqlTypeMetadata.new( sql_type: sql_type, type: cast_type.type, limit: cast_type.limit, precision: cast_type.precision, scale: cast_type.scale, ) end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1374 def foreign_key_for(from_table, **options) return unless supports_foreign_keys? foreign_keys(from_table).detect { |fk| fk.defined_for?(**options) } end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1379 def foreign_key_for!(from_table, to_table: nil, **options) foreign_key_for(from_table, to_table: to_table, **options) || raise(ArgumentError, "Table '#{from_table}' has no foreign key for #{to_table || options}") end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1365 def foreign_key_name(table_name, options) options.fetch(:name) do identifier = "#{table_name}_#{options.fetch(:column)}_fk" hashed_identifier = Digest::SHA256.hexdigest(identifier).first(10) "fk_rails_#{hashed_identifier}" end end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1343 def index_column_names(column_names) if column_names.is_a?(String) && /\W/.match?(column_names) column_names else Array(column_names) end end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1268 def index_name_for_remove(table_name, options = {}) return options[:name] if can_remove_index_by_name?(options) checks = [] if options.is_a?(Hash) checks << lambda { |i| i.name == options[:name].to_s } if options.key?(:name) column_names = index_column_names(options[:column]) else column_names = index_column_names(options) end if column_names.present? checks << lambda { |i| index_name(table_name, i.columns) == index_name(table_name, column_names) } end raise ArgumentError, "No name or columns specified" if checks.none? matching_indexes = indexes(table_name).select { |i| checks.all? { |check| check[i] } } if matching_indexes.count > 1 raise ArgumentError, "Multiple indexes found on #{table_name} columns #{column_names}. " \ "Specify an index name from #{matching_indexes.map(&:name).join(', ')}" elsif matching_indexes.none? raise ArgumentError, "No indexes found on #{table_name} with the options provided." else matching_indexes.first.name end end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1351 def index_name_options(column_names) if column_names.is_a?(String) && /\W/.match?(column_names) column_names = column_names.scan(/\w+/).join("_") end { column: column_names } end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1469 def insert_versions_sql(versions) sm_table = quote_table_name(schema_migration.table_name) if versions.is_a?(Array) sql = +"INSERT INTO #{sm_table} (version) VALUES\n" sql << versions.map { |v| "(#{quote(v)})" }.join(",\n") sql << ";\n\n" sql else "INSERT INTO #{sm_table} (version) VALUES (#{quote(versions)});" end end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1243 def options_for_index_columns(options) if options.is_a?(Hash) options.symbolize_keys else Hash.new { |hash, column| hash[column] = options } end end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1261 def quoted_columns_for_index(column_names, **options) return [column_names] if column_names.is_a?(String) quoted_columns = Hash[column_names.map { |name| [name.to_sym, quote_column_name(name).dup] }] add_options_for_index_columns(quoted_columns, **options).values end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1486 def quoted_scope(name = nil, type: nil) raise NotImplementedError end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1444 def remove_column_for_alter(table_name, column_name, type = nil, **options) "DROP COLUMN #{quote_column_name(column_name)}" end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1448 def remove_columns_for_alter(table_name, *column_names, **options) column_names.map { |column_name| remove_column_for_alter(table_name, column_name) } end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1465 def remove_timestamps_for_alter(table_name, **options) remove_columns_for_alter(table_name, :updated_at, :created_at) end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1307 def rename_column_indexes(table_name, column_name, new_column_name) column_name, new_column_name = column_name.to_s, new_column_name.to_s indexes(table_name).each do |index| next unless index.columns.include?(new_column_name) old_columns = index.columns.dup old_columns[old_columns.index(new_column_name)] = column_name generated_index_name = index_name(table_name, column: old_columns) if generated_index_name == index.name rename_index table_name, generated_index_name, index_name(table_name, column: index.columns) end end end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1298 def rename_table_indexes(table_name, new_name) indexes(new_name).each do |index| generated_index_name = index_name(table_name, column: index.columns) if generated_index_name == index.name rename_index new_name, generated_index_name, index_name(new_name, column: index.columns) end end end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1320 def schema_creation SchemaCreation.new(self) end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1359 def strip_table_name_prefix_and_suffix(table_name) prefix = Base.table_name_prefix suffix = Base.table_name_suffix table_name.to_s =~ /#{prefix}(.+)#{suffix}/ ? $1 : table_name.to_s end
# File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1392 def validate_index_length!(table_name, new_name, internal = false) max_index_length = internal ? index_name_length : allowed_index_name_length if new_name.length > max_index_length raise ArgumentError, "Index name '#{new_name}' on table '#{table_name}' is too long; the limit is #{allowed_index_name_length} characters" end end