PgPower

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.

Schemas

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'
  end
end

Create table

Use schema :schema option to specify schema name:

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

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)

Examples

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.'
end

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'
end

Remove comments:

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

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

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.

Examples

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.

Examples

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.

Examples

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.

Examples

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"

Tools

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

Running tests:

• Ensure your postgresql has postgres-contrib (Ubuntu) package installed. Tests depend on btree_gist and fuzzystrmatch extensions
• 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.

TODO:

Support for JRuby:

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

Credits

• Potapov Sergey - schema support
• Arthur Shagall - thanks for pg_comment
• Matthew Higgins - thanks for foreigner, which was used as a base for the foreign key support
• Artem Ignatyev - extension modules load/unload support
• Marcelo Silveira - thanks for rails partial index support that was backported into this gem

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.

Contributing

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.