Module: ActiveRecord::ConnectionAdapters::SchemaStatements

### Home Classes Methods

### In Files

- lib/active_record/connection_adapters/abstract/schema_statements.rb

### Methods

- #add_column
- #add_index
- #add_timestamps
- #assume_migrated_upto_version
- #change_column
- #change_column_default
- #change_table
- #column_exists?
- #columns
- #create_table
- #distinct
- #drop_table
- #index_exists?
- #index_name_exists?
- #initialize_schema_migrations_table
- #native_database_types
- #options_include_default?
- #quoted_columns_for_index
- #remove_column
- #remove_columns
- #remove_index
- #remove_timestamps
- #rename_column
- #rename_index
- #rename_table
- #structure_dump
- #table_alias_for
- #table_exists?

### Files

- README.rdoc

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# ActiveRecord::ConnectionAdapters::SchemaStatements

### Public Instance Methods

add_column(table_name, column_name, type, options = {}) click to toggle source

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

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 245
    def add_column(table_name, column_name, type, options = {})
      add_column_sql = "ALTER TABLE #{quote_table_name(table_name)} ADD #{quote_column_name(column_name)} #{type_to_sql(type, options[:limit], options[:precision], options[:scale])}"
      add_column_options!(add_column_sql, options)
      execute(add_column_sql)
    end

add_index(table_name, column_name, options = {}) click to toggle source

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 name, 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 column `: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_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))

    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

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 329
    def add_index(table_name, column_name, options = {})
      column_names = Array.wrap(column_name)
      index_name   = index_name(table_name, :column => column_names)

      if Hash === options # legacy support, since this param was a string
        index_type = options[:unique] ? "UNIQUE" : ""
        index_name = options[:name].to_s if options.key?(:name)
      else
        index_type = options
      end

      if index_name.length > index_name_length
        raise ArgumentError, "Index name '#{index_name}' on table '#{table_name}' is too long; the limit is #{index_name_length} characters"
      end
      if index_name_exists?(table_name, index_name, false)
        raise ArgumentError, "Index name '#{index_name}' on table '#{table_name}' already exists"
      end
      quoted_column_names = quoted_columns_for_index(column_names, options).join(", ")

      execute "CREATE #{index_type} INDEX #{quote_column_name(index_name)} ON #{quote_table_name(table_name)} (#{quoted_column_names})"
    end

add_timestamps(table_name) click to toggle source

Adds timestamps (created_at and updated_at) columns to the named table.

##### Examples

    add_timestamps(:suppliers)

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 515
    def add_timestamps(table_name)
      add_column table_name, :created_at, :datetime
      add_column table_name, :updated_at, :datetime
    end

assume_migrated_upto_version(version, migrations_path = ActiveRecord::Migrator.migrations_path) click to toggle source

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 445
    def assume_migrated_upto_version(version, migrations_path = ActiveRecord::Migrator.migrations_path)
      version = version.to_i
      sm_table = quote_table_name(ActiveRecord::Migrator.schema_migrations_table_name)

      migrated = select_values("SELECT version FROM #{sm_table}").map { |v| v.to_i }
      versions = Dir["#{migrations_path}/[0-9]*_*.rb"].map do |filename|
        filename.split('/').last.split('_').first.to_i
      end

      unless migrated.include?(version)
        execute "INSERT INTO #{sm_table} (version) VALUES ('#{version}')"
      end

      inserted = Set.new
      (versions - migrated).each do |v|
        if inserted.include?(v)
          raise "Duplicate migration #{v}. Please renumber your migrations to resolve the conflict."
        elsif v < version
          execute "INSERT INTO #{sm_table} (version) VALUES ('#{v}')"
          inserted << v
        end
      end
    end

change_column(table_name, column_name, type, options = {}) click to toggle source

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)

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 268
    def change_column(table_name, column_name, type, options = {})
      raise NotImplementedError, "change_column is not implemented"
    end

change_column_default(table_name, column_name, default) click to toggle source

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 appropriate SQL statement yourself.

##### Examples

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

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 278
    def change_column_default(table_name, column_name, default)
      raise NotImplementedError, "change_column_default is not implemented"
    end

change_table(table_name) click to toggle source

A block for changing columns in `table`.

### Example

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

##### Examples

###### 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(integer)` 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(integer)` 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 transformation

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 227
    def change_table(table_name)
      yield Table.new(table_name, self)
    end

column_exists?(table_name, column_name, type = nil, options = {}) click to toggle source

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

### Examples

    # 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)

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 66
    def column_exists?(table_name, column_name, type = nil, options = {})
      columns(table_name).any?{ |c| c.name == column_name.to_s &&
                                    (!type                 || c.type == type) &&
                                    (!options[:limit]      || c.limit == options[:limit]) &&
                                    (!options[:precision]  || c.precision == options[:precision]) &&
                                    (!options[:scale]      || c.scale == options[:scale]) }
    end

columns(table_name, name = nil) click to toggle source

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

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 53
    def columns(table_name, name = nil) end

create_table(table_name, options = {}) click to toggle source

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 `has_and_belongs_to_many` should set it to false.

`:primary_key`

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

  Also note that this just sets the primary key in the table. You additionally need to configure the primary key in the model via the `set_primary_key` macro. Models do NOT auto-detect the primary key from their table 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.

##### 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 (
      category_id int,
      supplier_id int
    )

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

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 153
    def create_table(table_name, options = {})
      table_definition = TableDefinition.new(self)
      table_definition.primary_key(options[:primary_key] || Base.get_primary_key(table_name.to_s.singularize)) unless options[:id] == false

      yield table_definition if block_given?

      if options[:force] && table_exists?(table_name)
        drop_table(table_name, options)
      end

      create_sql = "CREATE#{' TEMPORARY' if options[:temporary]} TABLE "
      create_sql << "#{quote_table_name(table_name)} ("
      create_sql << table_definition.to_sql
      create_sql << ") #{options[:options]}"
      execute create_sql
    end

distinct(columns, order_by) click to toggle source

SELECT DISTINCT clause for a given set of columns and a given ORDER BY clause. Both PostgreSQL and Oracle overrides this for custom DISTINCT syntax.

    distinct("posts.id", "posts.created_at desc")

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 508
    def distinct(columns, order_by)
      "DISTINCT #{columns}"
    end

drop_table(table_name, options = {}) click to toggle source

Drops a table from the database.

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 239
    def drop_table(table_name, options = {})
      execute "DROP TABLE #{quote_table_name(table_name)}"
    end

index_exists?(table_name, column_name, options = {}) click to toggle source

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

### Examples

    # 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 41
    def index_exists?(table_name, column_name, options = {})
      column_names = Array.wrap(column_name)
      index_name = options.key?(:name) ? options[:name].to_s : index_name(table_name, :column => column_names)
      if options[:unique]
        indexes(table_name).any?{ |i| i.unique && i.name == index_name }
      else
        indexes(table_name).any?{ |i| i.name == index_name }
      end
    end

index_name_exists?(table_name, index_name, default) click to toggle source

Verify the existence of an index with a given name.

The default argument is returned if the underlying implementation does not define the indexes method, as there’s no way to determine the correct answer in that case.

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 403
    def index_name_exists?(table_name, index_name, default)
      return default unless respond_to?(:indexes)
      index_name = index_name.to_s
      indexes(table_name).detect { |i| i.name == index_name }
    end

initialize_schema_migrations_table() click to toggle source

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

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 422
    def initialize_schema_migrations_table
      sm_table = ActiveRecord::Migrator.schema_migrations_table_name

      unless table_exists?(sm_table)
        create_table(sm_table, :id => false) do |schema_migrations_table|
          schema_migrations_table.column :version, :string, :null => false
        end
        add_index sm_table, :version, :unique => true,
          :name => "#{Base.table_name_prefix}unique_schema_migrations#{Base.table_name_suffix}"

        # Backwards-compatibility: if we find schema_info, assume we've
        # migrated up to that point:
        si_table = Base.table_name_prefix + 'schema_info' + Base.table_name_suffix

        if table_exists?(si_table)

          old_version = select_value("SELECT version FROM #{quote_table_name(si_table)}").to_i
          assume_migrated_upto_version(old_version)
          drop_table(si_table)
        end
      end
    end

native_database_types() click to toggle source

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.

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 9
    def native_database_types
      {}
    end

remove_column(table_name, *column_names) click to toggle source

Removes the column(s) from the table definition.

##### Examples

    remove_column(:suppliers, :qualification)
    remove_columns(:suppliers, :qualification, :experience)

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 255
    def remove_column(table_name, *column_names)
      raise ArgumentError.new("You must specify at least one column name.  Example: remove_column(:people, :first_name)") if column_names.empty?
      column_names.flatten.each do |column_name|
        execute "ALTER TABLE #{quote_table_name(table_name)} DROP #{quote_column_name(column_name)}"
      end
    end

Also aliased as: remove_columns
remove_columns(table_name, *column_names) click to toggle source
Alias for: remove_column
remove_index(table_name, options = {}) click to toggle source

Remove the given index from the table.

Remove the suppliers_name_index in the suppliers table.

    remove_index :suppliers, :name

Remove the index named accounts_branch_id_index in the accounts table.

    remove_index :accounts, :column => :branch_id

Remove the index named accounts_branch_id_party_id_index in the accounts table.

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

Remove the index named by_branch_party in the accounts table.

    remove_index :accounts, :name => :by_branch_party

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 361
    def remove_index(table_name, options = {})
      index_name = index_name(table_name, options)
      unless index_name_exists?(table_name, index_name, true)
        raise ArgumentError, "Index name '#{index_name}' on table '#{table_name}' does not exist"
      end
      remove_index!(table_name, index_name)
    end

remove_timestamps(table_name) click to toggle source

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

##### Examples

    remove_timestamps(:suppliers)

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 523
    def remove_timestamps(table_name)
      remove_column table_name, :updated_at
      remove_column table_name, :created_at
    end

rename_column(table_name, column_name, new_column_name) click to toggle source

Renames a column.

##### Example

    rename_column(:suppliers, :description, :name)

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 285
    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) click to toggle source

Rename 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 377
    def rename_index(table_name, old_name, new_name)
      # this is a naive implementation; some DBs may support this more efficiently (Postgres, for instance)
      old_index_def = indexes(table_name).detect { |i| i.name == old_name }
      return unless old_index_def
      remove_index(table_name, :name => old_name)
      add_index(table_name, old_index_def.columns, :name => new_name, :unique => old_index_def.unique)
    end

rename_table(table_name, new_name) click to toggle source

Renames a table.

##### Example

    rename_table('octopuses', 'octopi')

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 234
    def rename_table(table_name, new_name)
      raise NotImplementedError, "rename_table is not implemented"
    end

structure_dump() click to toggle source

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

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 411
    def structure_dump
    end

table_alias_for(table_name) click to toggle source

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

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 14
    def table_alias_for(table_name)
      table_name[0..table_alias_length-1].gsub(/\./, '_')
    end

table_exists?(table_name) click to toggle source

def tables(name = nil) end

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 20
    def table_exists?(table_name)
      tables.include?(table_name.to_s)
    end

### Protected Instance Methods

options_include_default?(options) click to toggle source

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 534
    def options_include_default?(options)
      options.include?(:default) && !(options[:null] == false && options[:default].nil?)
    end

quoted_columns_for_index(column_names, options = {}) click to toggle source

Overridden by the mysql adapter for supporting index lengths

    # File lib/active_record/connection_adapters/abstract/schema_statements.rb, line 530
    def quoted_columns_for_index(column_names, options = {})
      column_names.map {|name| quote_column_name(name) }
    end

[Validate]

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