Module ActiveRecord::ConnectionAdapters::SchemaStatements
In: lib/active_record/connection_adapters/abstract/schema_statements.rb

Methods

Public Instance methods

Adds a new column to the named table. See TableDefinition#column for details of the options you can use.

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 first column names, unless you pass +:name+ as an option.

When creating an index on multiple columns, the first column is used as a name for the index. For example, when you specify an index on two columns [+:first+, +:last+], the DBMS creates an index for both columns as well as an index for the first colum +:first+. Using just the first name for this index makes sense, because you will never have to create a singular index with this name.

Examples
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_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)

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

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

Sets a new default value for a column. If you want to set the default value to NULL, you are out of luck. You need to DatabaseStatements#execute the apppropriate SQL statement yourself.

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

Returns an array of Column objects for the table specified by table_name. See the concrete implementation for details on the expected parameter values.

Creates a new table 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() yields a TableDefinition instance
 create_table(:suppliers) do |t|
   t.column :name, :string, :limit => 60
   # Other fields here
 end

Regular form

 create_table(:suppliers)
 add_column(:suppliers, :name, :string, {:limit => 60})

The options hash can include the following keys:

:id
Set to true or false to add/not add a primary key column automatically. Defaults to true.
:primary_key
The name of the primary key, if one is to be added automatically. Defaults to id.
:options
Any extra options you want appended to the table definition.
:temporary
Make a temporary table.
:force
Set to true or false to drop the table before creating it. Defaults to false.
Examples
Add a backend specific option to the generated SQL (MySQL)
 create_table(:suppliers, :options => 'ENGINE=InnoDB DEFAULT CHARSET=utf8')

generates:

 CREATE TABLE suppliers (
   id int(11) DEFAULT NULL 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 int(11) DEFAULT NULL auto_increment PRIMARY KEY,
   name varchar(80)
 )
Do not add a primary key column
 create_table(:categories_suppliers, :id => false) do |t|
   t.column :category_id, :integer
   t.column :supplier_id, :integer
 end

generates:

 CREATE TABLE categories_suppliers_join (
   category_id int,
   supplier_id int
 )

See also TableDefinition#column for details on how to create columns.

Drops a table from the database.

Should not be called normally, but this operation is non-destructive. The migrations module handles this automatically.

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.

Removes the column from the table definition.

Examples
 remove_column(:suppliers, :qualification)

Remove the given index from the table.

Remove the suppliers_name_index in the suppliers table (legacy support, use the second or third forms).

  remove_index :suppliers, :name

Remove the index named accounts_branch_id in the accounts table.

  remove_index :accounts, :column => :branch_id

Remove the index named by_branch_party in the accounts table.

  remove_index :accounts, :name => :by_branch_party

You can remove an index on multiple columns by specifying the first column.

  add_index :accounts, [:username, :password]
  remove_index :accounts, :username

Renames a column.

Example
 rename_column(:suppliers, :description, :name)

Renames a table.

Example
 rename_table('octopuses', 'octopi')

Returns a string of CREATE TABLE SQL statement(s) for recreating the entire structure of the database.

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

This is the maximum length a table alias can be

[Validate]