Module: ActiveRecord::ConnectionAdapters::SchemaStatements

Module

ActiveRecord::ConnectionAdapters::SchemaStatements

In:

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

Methods

add_column add_index add_order_by_for_association_limiting! change_column change_column_default columns create_table distinct drop_table initialize_schema_information native_database_types options_include_default? remove_column remove_index rename_column rename_table structure_dump table_alias_for table_alias_length

Public Instance methods

add_column(table_name, column_name, type, options = {})

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

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 121
      def add_column(table_name, column_name, type, options = {})
        add_column_sql = "ALTER TABLE #{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 = {})

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_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)

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 186
      def add_index(table_name, column_name, options = {})
        column_names = Array(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] || index_name
        else
          index_type = options
        end
        quoted_column_names = column_names.map { |e| quote_column_name(e) }.join(", ")
        execute "CREATE #{index_type} INDEX #{quote_column_name(index_name)} ON #{table_name} (#{quoted_column_names})"
      end

add_order_by_for_association_limiting!(sql, options)

ORDER BY clause for the passed order option. PostgreSQL overrides this due to its stricter standards compliance.

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 296
      def add_order_by_for_association_limiting!(sql, options)
        sql << " ORDER BY #{options[:order]}"
      end

change_column(table_name, column_name, type, options = {})

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 activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 139
      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)

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 activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 149
      def change_column_default(table_name, column_name, default)
        raise NotImplementedError, "change_column_default is not implemented"
      end

columns(table_name, name = nil)

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 activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 28
      def columns(table_name, name = nil) end

create_table(name, options = {}) {|table_definition| ...}

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: Whether to automatically add a primary key column. Defaults to true. Join tables for has_and_belongs_to_many should set :id => false.
: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.

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 90
      def create_table(name, options = {})
        table_definition = TableDefinition.new(self)
        table_definition.primary_key(options[:primary_key] || "id") unless options[:id] == false

        yield table_definition

        if options[:force]
          drop_table(name, options) rescue nil
        end

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

distinct(columns, order_by)

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 activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 290
      def distinct(columns, order_by)
        "DISTINCT #{columns}"
      end

drop_table(name, options = {})

Drops a table from the database.

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 115
      def drop_table(name, options = {})
        execute "DROP TABLE #{name}"
      end

initialize_schema_information()

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

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 235
      def initialize_schema_information
        begin
          execute "CREATE TABLE #{ActiveRecord::Migrator.schema_info_table_name} (version #{type_to_sql(:integer)})"
          execute "INSERT INTO #{ActiveRecord::Migrator.schema_info_table_name} (version) VALUES(0)"
        rescue ActiveRecord::StatementInvalid
          # Schema has been initialized
        end
      end

native_database_types()

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 activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 7
      def native_database_types
        {}
      end

remove_column(table_name, column_name)

Removes the column from the table definition.

Examples

 remove_column(:suppliers, :qualification)

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 130
      def remove_column(table_name, column_name)
        execute "ALTER TABLE #{table_name} DROP #{quote_column_name(column_name)}"
      end

remove_index(table_name, options = {})

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 activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 210
      def remove_index(table_name, options = {})
        execute "DROP INDEX #{quote_column_name(index_name(table_name, options))} ON #{table_name}"
      end

rename_column(table_name, column_name, new_column_name)

Renames a column.

Example

 rename_column(:suppliers, :description, :name)

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 156
      def rename_column(table_name, column_name, new_column_name)
        raise NotImplementedError, "rename_column is not implemented"
      end

rename_table(name, new_name)

Renames a table.

Example

 rename_table('octopuses', 'octopi')

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 110
      def rename_table(name, new_name)
        raise NotImplementedError, "rename_table is not implemented"
      end

structure_dump()

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

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 230
      def structure_dump
      end

table_alias_for(table_name)

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

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 17
      def table_alias_for(table_name)
        table_name[0..table_alias_length-1].gsub(/\./, '_')
      end

table_alias_length()

This is the maximum length a table alias can be

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 12
      def table_alias_length
        255
      end

Protected Instance methods

options_include_default?(options)

# File activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb, line 301
        def options_include_default?(options)
          options.include?(:default) && !(options[:null] == false && options[:default].nil?)
        end