eActive Record and PostgreSQL
============================

This guide goes over PostgreSQL specific usage of Active Record.

How to use the PostgreSQL adapter for Active Record is described in the
[configuring Rails guide](configuring.html#configuring-a-postgresql-database).

In order to use the PostgreSQL adapter you need to have at least version 8.2
installed. Older versions are not supported.

Datatypes
---------

PostgreSQL offers a number of specific datatypes. Following is a list of types,
that are supported by the PostgreSQL adapter.

### Bytea

* [type definition](http://www.postgresql.org/docs/9.3/static/datatype-binary.html)
* [functions and operators](http://www.postgresql.org/docs/9.3/static/functions-binarystring.html)

```ruby
# db/migrate/20140207133952_create_documents.rb
create_table :documents do |t|
  t.binary 'payload'
end

# app/models/document.rb
class Document < ActiveRecord::Base
end

# Usage
data = File.read(Rails.root + "tmp/output.pdf")
Document.create payload: data
```

### Array

  * [type definition](http://www.postgresql.org/docs/9.3/static/arrays.html)
  * [functions and operators](http://www.postgresql.org/docs/9.3/static/functions-array.html)

```ruby
# db/migrate/20140207133952_create_books.rb
create_table :book do |t|
  t.string 'title'
  t.string 'tags', array: true
  t.integer 'ratings', array: true
end

# app/models/book.rb
class Book < ActiveRecord::Base
end

# Usage
Book.create title: "Brave New World",
            tags: ["fantasy", "fiction"],
            ratings: [4, 5]

## Books for a single tag
Book.where("'fantasy' = ANY (tags)")

## Books for multiple tags
Book.where("tags @> ARRAY[?]::varchar[]", ["fantasy", "fiction"])

## Books with 3 or more ratings
Book.where("array_length(ratings, 1) >= 3")
```

### Hstore

  * [type definition](http://www.postgresql.org/docs/9.3/static/hstore.html)

```ruby
# db/migrate/20131009135255_create_profiles.rb
ActiveRecord::Schema.define do
  create_table :profiles do |t|
    t.hstore 'settings'
  end
end

# app/models/profile.rb
class Profile < ActiveRecord::Base
end

# Usage
Profile.create(settings: { "color" => "blue", "resolution" => "800x600" })

profile = Profile.first
profile.settings # => {"color"=>"blue", "resolution"=>"800x600"}

profile.settings = {"color" => "yellow", "resulution" => "1280x1024"}
profile.save!

## you need to call _will_change! if you are editing the store in place
profile.settings["color"] = "green"
profile.settings_will_change!
profile.save!
```

### Json

 * [type definition](http://www.postgresql.org/docs/9.3/static/datatype-json.html)
 * [functions and operators](http://www.postgresql.org/docs/9.3/static/functions-json.html)

```ruby
# db/migrate/20131220144913_create_events.rb
create_table :events do |t|
  t.json 'payload'
end

# app/models/event.rb
class Event < ActiveRecord::Base
end

# Usage
Event.create(payload: { kind: "user_renamed", change: ["jack", "john"]})

event = Event.first
event.payload # => {"kind"=>"user_renamed", "change"=>["jack", "john"]}

## Query based on JSON document
Event.where("payload->'kind' = ?", "user_renamed")
```

### Range Types

  * [type definition](http://www.postgresql.org/docs/9.3/static/rangetypes.html)
  * [functions and operators](http://www.postgresql.org/docs/9.3/static/functions-range.html)

This type is mapped to Ruby [`Range`]() objects.

```ruby
# db/migrate/20130923065404_create_events.rb
create_table :events do |t|
  t.daterange 'duration'
end

# app/models/event.rb
class Event < ActiveRecord::Base
end

# Usage
Event.create(duration: Date.new(2014, 2, 11)..Date.new(2014, 2, 12))

event = Event.first
event.duration # => Tue, 11 Feb 2014...Thu, 13 Feb 2014

## All Events on a given date
Event.where("duration @> ?::date", Date.new(2014, 2, 12))

## Working with range bounds
event = Event.
  select("lower(duration) AS starts_at").
  select("upper(duration) AS ends_at").first

event.starts_at # => Tue, 11 Feb 2014
event.ends_at # => Thu, 13 Feb 2014
```

### Composite Types

  * [type definition](http://www.postgresql.org/docs/9.3/static/rowtypes.html)

Currently there is no special support for composite types. They are mapped to as
normal text columns:

```sql
CREATE TYPE full_address AS
(
  city VARCHAR(90),
  street VARCHAR(90)
);
```

```ruby
# db/migrate/20140207133952_create_contacts.rb
execute <<-SQL
 CREATE TYPE full_address AS
 (
   city VARCHAR(90),
   street VARCHAR(90)
 );
SQL
create_table :contacts do |t|
  t.column :address, :full_address
end

# app/models/contact.rb
class Contact < ActiveRecord::Base
end

# Usage
Contact.create address: "(Paris,Champs-Élysées)"
contact = Contact.first
contact.address # => "(Paris,Champs-Élysées)"
contact.address = "(Paris,Rue Basse)"
contact.save!
```

### Enumerated Types

  * [type definition](http://www.postgresql.org/docs/9.3/static/datatype-enum.html)

Currently there is no special support for enumerated types. They are mapped as
normal text columns:

```ruby
# db/migrate/20131220144913_create_events.rb
execute <<-SQL
  CREATE TYPE article_status AS ENUM ('draft', 'published');
SQL
create_table :articles do |t|
  t.column :status, :article_status
end

# app/models/article.rb
class Article < ActiveRecord::Base
end

# Usage
Article.create status: "draft"
article = Article.first
article.status # => "draft"

article.status = "published"
article.save!
```

### UUID

  * [type definition](http://www.postgresql.org/docs/9.3/static/datatype-uuid.html)
  * [generator functions](http://www.postgresql.org/docs/9.3/static/uuid-ossp.html)


```ruby
# db/migrate/20131220144913_create_revisions.rb
create_table :revisions do |t|
  t.column :identifier, :uuid
end

# app/models/revision.rb
class Revision < ActiveRecord::Base
end

# Usage
Revision.create identifier: "A0EEBC99-9C0B-4EF8-BB6D-6BB9BD380A11"

revision = Revision.first
revision.identifier # => "a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11"
```

#### as primary key

```ruby
# db/migrate/20131220144913_create_devices.rb
enable_extension 'uuid-ossp' unless extension_enabled?('uuid-ossp')
create_table :devices, id: :uuid, default: 'uuid_generate_v4()' do |t|
  t.string :kind
end

# app/models/device.rb
class Device < ActiveRecord::Base
end

# Usage
device = Device.create
device.id # => "814865cd-5a1d-4771-9306-4268f188fe9e"
```

### Bit String Types

  * [type definition](http://www.postgresql.org/docs/9.3/static/datatype-bit.html)
  * [functions and operators](http://www.postgresql.org/docs/9.3/static/functions-bitstring.html)

```ruby
# db/migrate/20131220144913_create_users.rb
create_table :users, force: true do |t|
  t.column :settings, "bit(8)"
end

# app/models/device.rb
class User < ActiveRecord::Base
end

# Usage
User.create settings: "01010011"
user = User.first
user.settings # => "(Paris,Champs-Élysées)"
user.settings = "0xAF"
user.settings # => 10101111
user.save!
```

### Network Address Types

  * [type definition](http://www.postgresql.org/docs/9.3/static/datatype-net-types.html)

The types `inet` and `cidr` are mapped to Ruby [`IPAddr`]() objects. The
`macaddr` type is mapped to normal text.

### Geometric Types

  * [type definition](http://www.postgresql.org/docs/9.3/static/datatype-geometric.html)

All geometric types are mapped to normal text.

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