SQL Server Adapter For Rails
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SQL Server 2005/2008 & Azure Adapter For ActiveRecord

The SQL Server adapter for ActiveRecord. If you need the adapter for SQL Server 2000, you are still in the right spot. Just install the latest 2.3.x version of the adapter. Note, we follow a rational versioning policy that tracks ActiveRecord. That means that our 2.3.x version of the adapter is only for the latest 2.3 version of Rails.

What's New

  • Rails 3.1 prepared statement support leverages cached query plans. If you use DBLIB/TinyTDS, you must use FreeTDS 0.91 !!!!! github.com/rails-sqlserver/tiny_tds/issues/41

  • We now support your native language date/time formats automatically!

  • Default unicode datatypes! Disable with #enable_default_unicode_types to false.

  • New #lowercase_schema_reflection configuration option for legacy DBs.

  • New dblib connection mode using TinyTDS! Default mode too!

Testing Rake Tasks Support

This is a long story, but if you are not working with a legacy database and you can trust your schema.rb to setup you local development or test database, then we have adapter level support for rails :db rake tasks. Please read this wiki page for full details.


Date/Time Data Type Hinting

SQL Server 2005 does not include a native data type for just 'date' or 'time', it only has 'datetime'. To pass the ActiveRecord tests we implemented two simple class methods that can teach your models to coerce column information to be cast correctly. Simply pass a list of symbols to either the coerce_sqlserver_date or coerce_sqlserver_time methods that correspond to 'datetime' columns that need to be cast correctly.

class Topic < ActiveRecord::Base
  coerce_sqlserver_date :last_read
  coerce_sqlserver_time :bonus_time

This implementation has some limitations. To date we can only coerce date/time types for models that conform to the expected ActiveRecord class to table naming conventions. So a table of 'foo_bar_widgets' will look for coerced column types in the FooBarWidget class.

Executing Stored Procedures

Every class that sub classes ActiveRecord::Base will now have an execute_procedure class method to use. This method takes the name of the stored procedure which can be a string or symbol and any number of variables to pass to the procedure. Arguments will automatically be quoted per the connection's standards as normal. For example.

Account.execute_procedure :update_totals, 'admin', nil, true

Native Data Type Support

Currently the following custom data types have been tested for schema definitions.

  • char

  • nchar

  • nvarchar

  • ntext

  • varchar(max)

  • nvarchar(max)

For example:

create_table :sql_server_custom_types, :force => true do |t|
  t.column :ten_code,       :char,      :limit => 10
  t.column :ten_code_utf8,  :nchar,     :limit => 10
  t.column :title_utf8,     :nvarchar
  t.column :body,           :varchar_max    # Creates varchar(max)
  t.column :body_utf8,      :ntext
  t.column :body2_utf8,     :nvarchar_max   # Creates nvarchar(max)

Manually creating a varchar(max) is not necessary since this is the default type created when specifying a :text field. As time goes on we will be testing other SQL Server specific data types are handled correctly when created in a migration.

Native Text/String/Binary Data Type Accessor

To pass the ActiveRecord tests we had to implement an class accessor for the native type created for :text columns. By default any :text column created by migrations will create a 'varchar(max)' data type. This type can be queried using the SQL = operator and has plenty of storage space which is why we made it the default. If for some reason you want to change the data type created during migrations you can configure this line to your liking in a config/initializers file.

ActiveRecord::ConnectionAdapters::SQLServerAdapter.native_text_database_type = 'varchar(8000)'

Also, there is a class attribute setter for the native string database type. This is the same for all SQL Server versions, 'varchar'. However it can be used instead of the #enable_default_unicode_types below for finer grain control over which types you want unicode safe when adding or changing the schema.

ActiveRecord::ConnectionAdapters::SQLServerAdapter.native_string_database_type = 'nvarchar'

By default any :binary column created by migrations will create a 'varbinary(max)' data type. This too can be set using an initializer.

ActiveRecord::ConnectionAdapters::SQLServerAdapter.native_binary_database_type = 'image'

Setting Unicode Types As Default

By default the adapter will use unicode safe data types for :string and :text types when defining/changing the schema!!! This was changed in version 3.1 since it is about time we push better unicode support and since we default to TinyTDS (DBLIB) which supports unicode queries and data. If you choose, you can set the following class attribute in a config/initializers file that will disable this behavior.

# Default
ActiveRecord::ConnectionAdapters::SQLServerAdapter.enable_default_unicode_types = true
ActiveRecord::ConnectionAdapters::SQLServerAdapter.native_text_database_type = 'nvarchar(max)'
ActiveRecord::ConnectionAdapters::SQLServerAdapter.native_string_database_type = 'nvarchar'

# Disabled
ActiveRecord::ConnectionAdapters::SQLServerAdapter.enable_default_unicode_types = false
ActiveRecord::ConnectionAdapters::SQLServerAdapter.native_text_database_type = 'varchar(max)'
ActiveRecord::ConnectionAdapters::SQLServerAdapter.native_string_database_type = 'varchar'

It is important to remember that unicode types in SQL Server have approximately half the storage capacity as their counter parts. So where a normal string would max out at (8000) a unicode string will top off at (4000).

Force Schema To Lowercase

Although it is not necessary, the Ruby convention is to use lowercase method names. If your database schema is in upper or mixed case, we can force all table and column names during the schema reflection process to be lowercase. Add this to your config/initializers file for the adapter.

ActiveRecord::ConnectionAdapters::SQLServerAdapter.lowercase_schema_reflection = true

Schemas & Users

Depending on your user and schema setup, it may be needed to use a table name prefix of “dbo.”. So something like this in your initializer file for ActiveRecord or the adapter.

ActiveRecord::Base.table_name_prefix = 'dbo.'

Schema Information Logging

By default all queries to the INFORMATION_SCHEMA table is silenced. If you think logging these queries are useful, you can enable it by adding this like to a initializer file.

ActiveRecord::ConnectionAdapters::SQLServerAdapter.log_info_schema_queries = true

Auto Connecting

By default the adapter will auto connect to lost DB connections. For every query it will retry at intervals of 2, 4, 8, 16 and 32 seconds. During each retry it will callback out to ActiveRecord::Base.did_retry_sqlserver_connection(connection,count). When all retries fail, it will callback to ActiveRecord::Base.did_lose_sqlserver_connection(connection). Both implementations of these methods are to write to the rails logger, however, they make great override points for notifications like Hoptoad. If you want to disable automatic reconnections use the following in an initializer.

ActiveRecord::ConnectionAdapters::SQLServerAdapter.auto_connect = false


The adapter follows a rational versioning policy that also tracks ActiveRecord's major and minor version. That means the latest 3.1.x version of the adapter will always work for the latest 3.1.x version of ActiveRecord.


The adapter has no strict gem dependencies outside of ActiveRecord. You will have to pick a connection mode, the default is dblib which uses the TinyTDS gem. Just bundle the gem and the adapter will use it.

gem 'tiny_tds'
gem 'activerecord-sqlserver-adapter', '~> 3.1.0'

If you want to use ruby ODBC, please use at least version 0.99992 since that contains fixes for both native types as well as fixes for proper encoding support under 1.9. If you have any troubles installing the lower level libraries for the adapter, please consult the wiki pages for various platform installation guides. Tons of good info can be found and we ask that you contribute too!



If you’d like to contribute a feature or bugfix, thanks! To make sure your fix/feature has a high chance of being added, please read the following guidelines. First, ask on the Google list, IRC, or post a ticket on github issues. Second, make sure there are tests! We will not accept any patch that is not tested. Please read the RUNNING_UNIT_TESTS file for the details of how to run the unit tests.

Credits & Contributions

Many many people have contributed. If you do not see your name here and it should be let us know. Also, many thanks go out to those that have pledged financial contributions.


Up-to-date list of contributors: github.com/rails-sqlserver/activerecord-sqlserver-adapter/contributors

  • metaskills (Ken Collins)

  • h-lame (Murray Steele)

  • vegantech

  • cjheath (Clifford Heath)

  • jrafanie (Joe Rafaniello)

  • nerdrew (Andrew Ryan)

  • snowblink (Jonathan Lim)

  • koppen (Jakob Skjerning)

  • ebryn (Erik Bryn)

  • adzap (Adam Meehan)

  • neomindryan (Ryan Findley)

  • jeremydurham (Jeremy Durham)




Copyright © 2008-2011. It is free software, and may be redistributed under the terms specified in the MIT-LICENSE file.