Module: ActiveRecord::ConnectionAdapters::SchemaStatements

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

Instance Method Summary collapse

Instance Method Details

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

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. Use nil for NULL.

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

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

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

  • :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.

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

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

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

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

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

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

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

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

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

Examples

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

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

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

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

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

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

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

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 600

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

  at = create_alter_table table_name
  at.add_column(column_name, type, **options)
  execute schema_creation.accept at
end

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

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

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

Creating a simple foreign key
add_foreign_key :articles, :authors

generates:

ALTER TABLE "articles" ADD CONSTRAINT fk_rails_e74ce85cbc FOREIGN KEY ("author_id") REFERENCES "authors" ("id")
Creating a foreign key on a specific column
add_foreign_key :articles, :users, column: :author_id, primary_key: "lng_id"

generates:

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

generates:

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

The options hash can include the following keys:

:column

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

:primary_key

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

:name

The constraint name. Defaults to fk_rails_<identifier>.

:on_delete

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

:on_update

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

:validate

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1041

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

#add_index(table_name, column_name, options = {}) ⇒ Object

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

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

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

generates:

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

generates:

CREATE INDEX IF NOT EXISTS suppliers_name_index 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 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.

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.


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 821

def add_index(table_name, column_name, options = {})
  index_name, index_type, index_columns, index_if_not_exists_clause, index_options = add_index_options(table_name, column_name, **options)
  execute "CREATE #{index_type} #{index_if_not_exists_clause} #{quote_column_name(index_name)} ON #{quote_table_name(table_name)} (#{index_columns})#{index_options}"
end

#add_index_options(table_name, column_name, comment: nil, **options) ⇒ Object

:nodoc:


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1222

def add_index_options(table_name, column_name, comment: nil, **options) # :nodoc:
  column_names = index_column_names(column_name)

  options.assert_valid_keys(:unique, :order, :name, :where, :length, :internal, :using, :algorithm, :type, :opclass, :if_not_exists)

  index_type = options[:type].to_s if options.key?(:type)
  index_type ||= options[:unique] ? "UNIQUE" : ""
  index_name = options[:name].to_s if options.key?(:name)
  index_name ||= index_name(table_name, column_names)

  if options.key?(:algorithm)
    algorithm = index_algorithms.fetch(options[:algorithm]) {
      raise ArgumentError.new("Algorithm must be one of the following: #{index_algorithms.keys.map(&:inspect).join(', ')}")
    }
  end

  using = "USING #{options[:using]}" if options[:using].present?

  if supports_partial_index?
    index_options = options[:where] ? " WHERE #{options[:where]}" : ""
  end

  if_not_exists_index_clause = options[:if_not_exists] ? "INDEX IF NOT EXISTS" : "INDEX"

  validate_index_length!(table_name, index_name, options.fetch(:internal, false))

  index_columns = quoted_columns_for_index(column_names, **options).join(", ")

  [index_name, index_type, index_columns, if_not_exists_index_clause, index_options, algorithm, using, comment]
end

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

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

The options hash can include the following keys:

:type

The reference column type. Defaults to :bigint.

:index

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

:foreign_key

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

:polymorphic

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

:null

Whether the column allows nulls. Defaults to true.

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 954

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

#add_timestamps(table_name, **options) ⇒ Object

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

add_timestamps(:suppliers, null: true)


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

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

#assume_migrated_upto_version(version, migrations_paths = nil) ⇒ Object 


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1123

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

#change_column(table_name, column_name, type, options = {}) ⇒ Object

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

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

Raises:

  • (NotImplementedError) 

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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 649

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

#change_column_comment(table_name, column_name, comment_or_changes) ⇒ Object

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

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

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

Raises:

  • (NotImplementedError) 

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

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

#change_column_default(table_name, column_name, default_or_changes) ⇒ Object

Sets a new default value for a column:

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

Setting the default to nil effectively drops the default:

change_column_default(:users, :email, nil)

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

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

Raises:

  • (NotImplementedError) 

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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 667

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

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

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

change_column_null(:users, :nickname, false)

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

change_column_null(:users, :nickname, true)

allows them to be NULL (drops the constraint).

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

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

Raises:

  • (NotImplementedError) 

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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 687

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

#change_table(table_name, **options) ⇒ Object

A block for changing columns in table.

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

The options hash can include the following keys:

:bulk

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

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

Defaults to false.

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

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

Creates a company_id(bigint) column.

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

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

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

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 478

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

#change_table_comment(table_name, comment_or_changes) ⇒ Object

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

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

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

Raises:

  • (NotImplementedError) 

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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1263

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

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

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

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

# Check a column exists of a particular type
column_exists?(:suppliers, :name, :string)

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

Returns:

  • (Boolean) 

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

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

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

#columns(table_name) ⇒ Object

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


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# File 'activerecord/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

#columns_for_distinct(columns, orders) ⇒ Object

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

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1189

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

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

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

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

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

:table_name

Sets the table name, overriding the default.

:column_options

Any extra options you want appended to the columns definition.

:options

Any extra options you want appended to the table definition.

:temporary

Make a temporary table.

:force

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

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

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

generates:

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 375

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

#create_schema_dumper(options) ⇒ Object

:nodoc:


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1277

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

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

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

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

Block form

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

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

Block form, with shorthand

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

Regular form

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

The options hash can include the following keys:

:id

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

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

:primary_key

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

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

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

:options

Any extra options you want appended to the table definition.

:temporary

Make a temporary table.

:force

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

:if_not_exists

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

:as

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

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

generates:

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

generates:

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

generates:

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

generates:

CREATE TABLE 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 TableDefinition#column for details on how to create columns.

Yields:

  • (td) 

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

def create_table(table_name, id: :primary_key, primary_key: nil, force: nil, **options)
  td = create_table_definition(
    table_name, **options.extract!(:temporary, :if_not_exists, :options, :as, :comment)
  )

  if id && !td.as
    pk = primary_key || Base.get_primary_key(table_name.to_s.singularize)

    if pk.is_a?(Array)
      td.primary_keys pk
    else
      td.primary_key pk, id, **options
    end
  end

  yield td if block_given?

  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.merge!(if_not_exists: td.if_not_exists))
    end
  end

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

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

  result
end

#data_source_exists?(name) ⇒ Boolean

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

data_source_exists?(:ebooks)

Returns:

  • (Boolean) 

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# File 'activerecord/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

#data_sources ⇒ Object

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


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# File 'activerecord/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

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

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.


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 395

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

#drop_table(table_name, **options) ⇒ Object

Drops a table from the database.

:force

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

:if_exists

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

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 508

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

#dump_schema_information ⇒ Object

:nodoc:


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1114

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

#foreign_key_column_for(table_name) ⇒ Object

:nodoc:


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1102

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

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

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

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

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

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

Returns:

  • (Boolean) 

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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1098

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

#foreign_key_options(from_table, to_table, options) ⇒ Object

:nodoc:


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1107

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

#foreign_keys(table_name) ⇒ Object

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

Raises:

  • (NotImplementedError) 

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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 993

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

#index_exists?(table_name, column_name, options = {}) ⇒ Boolean

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

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

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

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

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

Returns:

  • (Boolean) 

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# File 'activerecord/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

#index_name(table_name, options) ⇒ Object

:nodoc:


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

def index_name(table_name, options) #:nodoc:
  if Hash === options
    if options[:column]
      "index_#{table_name}_on_#{Array(options[:column]) * '_and_'}"
    elsif options[:name]
      options[:name]
    else
      raise ArgumentError, "You must specify the index name"
    end
  else
    index_name(table_name, index_name_options(options))
  end
end

#index_name_exists?(table_name, index_name) ⇒ Boolean

Verifies the existence of an index with a given name.

Returns:

  • (Boolean) 

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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 901

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

#indexes(table_name) ⇒ Object

Returns an array of indexes for the given table.

Raises:

  • (NotImplementedError) 

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

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

#internal_string_options_for_primary_key ⇒ Object

:nodoc:


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1119

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

#native_database_types ⇒ Object

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


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

def native_database_types
  {}
end

#options_include_default?(options) ⇒ Boolean

Returns:

  • (Boolean) 

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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1253

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

#primary_key(table_name) ⇒ Object

Returns just a table's primary key


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# File 'activerecord/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

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

Removes the column from the table definition.

remove_column(:suppliers, :qualification)

The type and options parameters will be ignored if present. It can be helpful to provide these in a migration's change method so it can be reverted. In that case, type and options will be used by #add_column. Indexes on the column are automatically removed.

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

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 637

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, **options) ⇒ Object

Removes the given columns from the table definition.

remove_columns(:suppliers, :qualification, :experience)

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

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

Raises:

  • (ArgumentError) 

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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 615

def remove_columns(table_name, *column_names, **options)
  raise ArgumentError.new("You must specify at least one column name. Example: remove_columns(:people, :first_name)") if column_names.empty?
  type = options.delete(:type)
  column_names.each do |column_name|
    remove_column(table_name, column_name, type, **options)
  end
end

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

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

Removes the foreign key on accounts.branch_id.

remove_foreign_key :accounts, :branches

Removes the foreign key on accounts.owner_id.

remove_foreign_key :accounts, column: :owner_id

Removes the foreign key on accounts.owner_id.

remove_foreign_key :accounts, to_table: :owners

Removes the foreign key named special_fk_name on the accounts table.

remove_foreign_key :accounts, name: :special_fk_name

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

:to_table

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1076

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

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

Removes the given index from the table.

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

remove_index :accounts, :branch_id

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

remove_index :accounts, column: :branch_id

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

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

Removes the index named by_branch_party in the accounts table.

remove_index :accounts, name: :by_branch_party

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

remove_index :accounts, :branch_id, name: :by_branch_party

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

remove_index :accounts, if_exists: true

Removes the index named by_branch_party in the accounts table concurrently.

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

Note: only supported by PostgreSQL.

Concurrently removing an index is not supported in a transaction.

For more information see the “Transactional Migrations” section.


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 862

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

  index_name = index_name_for_remove(table_name, column_name, options)

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

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

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

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


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 974

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

#remove_timestamps(table_name, **options) ⇒ Object

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

remove_timestamps(:suppliers)


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

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

#rename_column(table_name, column_name, new_column_name) ⇒ Object

Renames a column.

rename_column(:suppliers, :description, :name)

Raises:

  • (NotImplementedError) 

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

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

#rename_index(table_name, old_name, new_name) ⇒ Object

Renames an index.

Rename the index_people_on_last_name index to index_users_on_last_name:

rename_index :people, 'index_people_on_last_name', 'index_users_on_last_name'


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 876

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

#rename_table(table_name, new_name) ⇒ Object

Renames a table.

rename_table('octopuses', 'octopi')

Raises:

  • (NotImplementedError) 

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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 492

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

#table_alias_for(table_name) ⇒ Object

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


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# File 'activerecord/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

#table_comment(table_name) ⇒ Object

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


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

def table_comment(table_name)
  nil
end

#table_exists?(table_name) ⇒ Boolean

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

table_exists?(:developers)

Returns:

  • (Boolean) 

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# File 'activerecord/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

#table_options(table_name) ⇒ Object 


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

def table_options(table_name)
  nil
end

#tables ⇒ Object

Returns an array of table names defined in the database.


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

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

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

:nodoc:


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1149

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

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

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

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

    column_type_sql
  else
    type.to_s
  end
end

#update_table_definition(table_name, base) ⇒ Object

:nodoc:


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# File 'activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb', line 1218

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

#view_exists?(view_name) ⇒ Boolean

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

view_exists?(:ebooks)

Returns:

  • (Boolean) 

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# File 'activerecord/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

#views ⇒ Object

Returns an array of view names defined in the database.


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

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