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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
and:numeric
columns. -
:scale
- Specifies the scale for the:decimal
and:numeric
columns. -
: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
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
-
(Postgres only) Specify whether or not the constraint should be validated. Defaults to
true
.
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 968 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)
generates:
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 })
generates:
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)
generates:
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.
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 771 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
add_reference(:products, :user)
Create a user_id string column
add_reference(:products, :user, type: :string)
Create supplier_id, supplier_type columns and appropriate index
add_reference(:products, :supplier, polymorphic: true, index: 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})
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 activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1123 def add_timestamps(table_name, options = {}) options[:null] = false if options[:null].nil? add_column table_name, :created_at, :datetime, options add_column table_name, :updated_at, :datetime, options end
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 1045 def assume_migrated_upto_version(version, migrations_paths) migrations_paths = Array(migrations_paths) version = version.to_i sm_table = quote_table_name(ActiveRecord::SchemaMigration.table_name) migrated = ActiveRecord::SchemaMigration.all_versions.map(&:to_i) versions = migration_context.migration_files.map do |file| migration_context.parse_migration_filename(file).first.to_i end 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 if supports_multi_insert? execute insert_versions_sql(inserting) else inserting.each do |v| execute insert_versions_sql(v) end end 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)
Changes the comment for a column or removes it if nil
.
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")
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.
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 activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 464 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
.
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 activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 131 def column_exists?(table_name, column_name, type = nil, options = {}) column_name = column_name.to_s checks = [] checks << lambda { |c| c.name == column_name } checks << lambda { |c| c.type == type } 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
.
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 activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 367 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. :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=utf8')
generates:
CREATE TABLE suppliers (
id bigint auto_increment PRIMARY KEY
) ENGINE=InnoDB DEFAULT CHARSET=utf8
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 activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 289 def create_table(table_name, comment: nil, **options) td = create_table_definition table_name, options[:temporary], options[:options], options[:as], comment: comment 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 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? change_table_comment(table_name, comment) if comment.present? 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)
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.
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.
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 an array of foreign keys for the given table. The foreign keys are represented as ForeignKeyDefinition objects.
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 activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 99 def index_exists?(table_name, column_name, options = {}) column_names = Array(column_name).map(&:to_s) checks = [] checks << lambda { |i| 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.
Returns an array of indexes for the given table.
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.
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.
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 601 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 activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 587 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 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.
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 996 def remove_foreign_key(from_table, options_or_to_table = {}) return unless supports_foreign_keys? fk_name_to_delete = foreign_key_for!(from_table, options_or_to_table).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
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 794 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: true)
Remove polymorphic reference
remove_reference(:products, :supplier, polymorphic: true)
Remove the reference with a foreign key
remove_reference(:products, :user, index: true, foreign_key: true)
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 901 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)
Renames a column.
rename_column(:suppliers, :description, :name)
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 activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 805 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')
Truncates a table alias according to the limits of the current adapter.
Returns the table comment that's stored in database metadata.
Checks to see if the table table_name
exists on the database.
table_exists?(:developers)
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 59 def table_exists?(table_name) query_values(data_source_sql(table_name, type: "BASE TABLE"), "SCHEMA").any? if table_name.present? rescue NotImplementedError tables.include?(table_name.to_s) end
Returns an array of table names defined in the database.
Checks to see if the view view_name
exists on the database.
view_exists?(:ebooks)
# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 74 def view_exists?(view_name) query_values(data_source_sql(view_name, type: "VIEW"), "SCHEMA").any? if view_name.present? rescue NotImplementedError views.include?(view_name.to_s) end