ActiveRecord extension to get more from PostgreSQL.
Ruby Other
Latest commit ccabd52 Mar 27, 2014 Bruce Burdick Merge TMXCredit/pg_power#51 'greyblake/master'
* greyblake/master:
  Escape view defenition with inline document syntax #49



Build Status Dependency Status Code Climate

ActiveRecord extension to get more from PostgreSQL:

  • Create/drop schemas.
  • Set/remove comments on columns and tables.
  • Use foreign keys.
  • Use partial indexes.
  • Run index creation concurrently.

Environment notes

It was tested with Rails 3.1.x and 3.2.x, Ruby 1.8.7 REE and 1.9.3.

NOTE: JRuby is not yet supported. The current ActiveRecord JDBC adapter has its own Rails4-compatible method named "create_schema" which conflicts with this gem.


Create schema

In migrations you can use create_schema and drop_schema methods like this:

class ReplaceDemographySchemaWithPolitics < ActiveRecord::Migration
  def change
    drop_schema 'demography'
    create_schema 'politics'

Create table

Use schema :schema option to specify schema name:

create_table "countries", :schema => "demography" do |t|
  # columns goes here

Move table to another schema

Move table countries from demography schema to public:

move_table_to_schema 'demography.countries', :public

Table and column comments

Provides the following methods to manage comments:

  • set_table_comment(table_name, comment)
  • remove_table_comment(table_name)
  • set_column_comment(table_name, column_name, comment)
  • remove_column_comment(table_name, column_name, comment)
  • set_column_comments(table_name, comments)
  • remove_column_comments(table_name, *comments)


Set a comment on the given table.

set_table_comment :phone_numbers, 'This table stores phone numbers that conform to the North American Numbering Plan.'

Sets a comment on a given column of a given table.

set_column_comment :phone_numbers, :npa, 'Numbering Plan Area Code - Allowed ranges: [2-9] for first digit, [0-9] for second and third digit.'

Removes any comment from the given table.

remove_table_comment :phone_numbers

Removes any comment from the given column of a given table.

remove_column_comment :phone_numbers, :npa

Set comments on multiple columns in the table.

set_column_comments :phone_numbers, :npa => 'Numbering Plan Area Code - Allowed ranges: [2-9] for first digit, [0-9] for second and third digit.',
                                    :nxx => 'Central Office Number'

Remove comments from multiple columns in the table.

remove_column_comments :phone_numbers, :npa, :nxx

PgPower also adds extra methods to change_table.

Set comments:

change_table :phone_numbers do |t|
  t.set_table_comment 'This table stores phone numbers that conform to the North American Numbering Plan.'
  t.set_column_comment :npa, 'Numbering Plan Area Code - Allowed ranges: [2-9] for first digit, [0-9] for second and third digit.'

change_table :phone_numbers do |t|
  t.set_column_comments :npa => 'Numbering Plan Area Code - Allowed ranges: [2-9] for first digit, [0-9] for second and third digit.',
                        :nxx => 'Central Office Number'

Remove comments:

change_table :phone_numbers do |t|
  t.remove_column_comment :npa

change_table :phone_numbers do |t|
  t.remove_column_comments :npa, :nxx

Foreign keys

We imported some code of foreigner gem and patched it to be schema-aware. We also added support for index auto-generation.

You should disable foreigner in your Gemfile if you want to use pg_power.

If you do not want to generate an index, pass the :exclude_index => true option.

The syntax is compatible with foreigner:

Add foreign key from comments to posts using post_id column as key by default:

add_foreign_key(:comments, :posts)

Specify key explicitly:

add_foreign_key(:comments, :posts, :column => :blog_post_id)

Specify name of foreign key constraint:

add_foreign_key(:comments, :posts, :name => "comments_posts_fk")

It works with schemas as expected:

add_foreign_key('blog.comments', 'blog.posts')

Adds the index 'index_comments_on_post_id':

add_foreign_key(:comments, :posts)

Does not add an index:

add_foreign_key(:comments, :posts, :exclude_index => true)

Partial Indexes

We used a Rails 4.x pull request as a starting point, backported to Rails 3.1.x and patched it to be schema-aware.


Add a partial index to a table

add_index(:comments, [:country_id, :user_id], :where => 'active')

Add a partial index to a schema table

add_index('blog.comments', :user_id, :where => 'active')

Indexes on Expressions

PostgreSQL supports indexes on expressions. Right now, only basic functional expressions are supported.


Add an index to a column with a function

add_index(:comments, "lower(text)")

You can also specify index access method

create_extension 'btree_gist'
create_extension 'fuzzystrmatch'
add_index(:comments, 'dmetaphone(author)', :using => 'gist')

Concurrent index creation

PostgreSQL supports concurent index creation. We added that feature to migration DSL on index and foreign keys creation.


Add an index concurrently to a table

add_index :table, :column_id, :concurrently => true

Add an index concurrently along with foreign key

add_foreign_key :table1, :table2, :column => :column_id, :concurrent_index => true

Loading/Unloading postgresql extension modules

Postgresql is shipped with a number of extension modules. PgPower provides some tools to load/unload such modules by the means of migrations.

Please note. CREATE/DROP EXTENSION command has been introduced in postgresql 9.1 only. So this functionality will not be available for the previous versions.


Load fuzzystrmatch extension module and create its objects in schema public:

create_extension "fuzzystrmatch"

Load version 1.0 of the btree_gist extension module and create its objects in schema demography.

create_extension "btree_gist", :schema_name => "demography", :version => "1.0"

Unload extension module:

drop_extension "fuzzystrmatch"


Version 1.6.0 introduces experimental support for creating views. This API should only be used with the understanding that it is preliminary 'alpha' at best.


create_view "demography.citizens_view", "select * from demography.citizens"


PgPower::Tools provides number of useful methods:

PgPower::Tools.create_schema "services"                 # => create new PG schema "services"
PgPower::Tools.create_schema "nets"                     # => create new PG schema "nets"
PgPower::Tools.drop_schema "services"                   # => remove the PG schema "services"
PgPower::Tools.schemas                                  # => ["public", "information_schema", "nets"]
PgPower::Tools.index_exists?(table, columns, options)   # => returns true if an index exists for the given params

Rails 3

If you are using rails 3.x, use previous pg_power version:

gem 'pg_power', '~> 1.6.4'

Running tests:

  • Ensure your postgresql has postgres-contrib (Ubuntu) package installed. Tests depend on btree_gist and fuzzystrmatch extensions
    • If on Mac, see below for installing contrib packages
  • Configure spec/dummy/config/database.yml for development and test environments.
  • Run rake spec.
  • Make sure migrations don't raise exceptions and all specs pass.

Installing contrib packages on Mac OS X:

  • This assumes you are using MacPorts to install Postgres. If using homebrew or the Postgres App, you will need to adjust the instructions accordingly (please add to this README when you do)
  • Assuming you installed with default options (including auto-clean), you will need to rebuild the postgresql port and keep the build files
    • sudo port -k -s build postgresql91
    • (adjust the version number above appropriately)
  • Now you can make and install the btree_gist and any other contrib modules
    • cd port work postgresql91/postgresql-9.1.7/contrib/btree_gist
    • (again, you may need to adjust the version number to your specific version)
    • sudo make all
    • sudo make install
  • Done!


Support for JRuby:

  • Jdbc driver provides its own create_schema(schema, user) method - solve conflicts.


Copyright and License

  • Copyright (c) 2012 TMX Credit.
  • Initial foreign key code taken from foreigner, Copyright (c) 2009 Matthew Higgins
  • pg_comment Copyright (c) 2011 Arthur Shagall
  • Partial index Copyright (c) 2012 Marcelo Silveira

Released under the MIT License. See the MIT-LICENSE file for more details.


Contributions are welcome. However, before issuing a pull request, please make sure of the following:

  • All specs are passing (under both ree and 1.9.3)
  • Any new features have test coverage.
  • Anything that breaks backward compatibility has a very good reason for doing so.