Where is the documentation page for ActiveRecord data types?

I can't find the active record documenation page that has a list of all the data types.

Can someone help me out?

If you're talking about the types for migrations, e.g. string, integer, datetime, etc, then you want ActiveRecord::ConnectionAdapters::TableDefinition, the column method. (Rails 5 edit: see also connection.add_column.)

As of this update, the standard types are:

• :primary_key
• :string
• :text
• :integer
• :bigint
• :float
• :decimal
• :numeric
• :datetime
• :time
• :date
• :binary
• :boolean

The implementation of :decimal is different with each database, so I'd avoid it if possible. 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 also be avoided.

You can also see ActiveRecord data types in sources. Each DBMS adapter contains its own mapping. For example, in MySQL case look at this file: https://github.com/rails/rails/blob/master/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb#L148 or get it by this line of code for current DBMS adapter:

ActiveRecord::Base.connection.native_database_types.keys

Here is the default mappings of types for database adapters:

> Note this is based on Rails Source Code dated 13th Feb 2015 (Rails > 4.2)

In case someone wants to see how these datatypes get mapped into the database you are using.

You can grab easily at rails source code at github.

For example

> Rails data types to mysql datatyes mapping.

NATIVE_DATABASE_TYPES = {
        :primary_key => "int(11) auto_increment PRIMARY KEY",
        :string      => { :name => "varchar", :limit => 255 },
        :text        => { :name => "text" },
        :integer     => { :name => "int", :limit => 4 },
        :float       => { :name => "float" },
        :decimal     => { :name => "decimal" },
        :datetime    => { :name => "datetime" },
        :time        => { :name => "time" },
        :date        => { :name => "date" },
        :binary      => { :name => "blob" },
        :boolean     => { :name => "tinyint", :limit => 1 }
      }

Found at https://github.com/rails/rails/blob/master/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb#L148

And if some one wants postgreSQL here you go.

NATIVE_DATABASE_TYPES = {
        primary_key: "serial primary key",
        bigserial: "bigserial",
        string:      { name: "character varying" },
        text:        { name: "text" },
        integer:     { name: "integer" },
        float:       { name: "float" },
        decimal:     { name: "decimal" },
        datetime:    { name: "timestamp" },
        time:        { name: "time" },
        date:        { name: "date" },
        daterange:   { name: "daterange" },
        numrange:    { name: "numrange" },
        tsrange:     { name: "tsrange" },
        tstzrange:   { name: "tstzrange" },
        int4range:   { name: "int4range" },
        int8range:   { name: "int8range" },
        binary:      { name: "bytea" },
        boolean:     { name: "boolean" },
        bigint:      { name: "bigint" },
        xml:         { name: "xml" },
        tsvector:    { name: "tsvector" },
        hstore:      { name: "hstore" },
        inet:        { name: "inet" },
        cidr:        { name: "cidr" },
        macaddr:     { name: "macaddr" },
        uuid:        { name: "uuid" },
        json:        { name: "json" },
        jsonb:       { name: "jsonb" },
        ltree:       { name: "ltree" },
        citext:      { name: "citext" },
        point:       { name: "point" },
        bit:         { name: "bit" },
        bit_varying: { name: "bit varying" },
        money:       { name: "money" },
      }