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"
```
### 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.
UUID Primary Keys
-----------------
NOTE: you need to enable the `uuid-ossp` extension to generate UUIDs.
```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"
```
Full Text Search
----------------
```ruby
# db/migrate/20131220144913_create_documents.rb
create_table :documents do |t|
t.string 'title'
t.string 'body'
end
execute "CREATE INDEX documents_idx ON documents USING gin(to_tsvector('english', title || ' ' || body));"
# app/models/document.rb
class Document < ActiveRecord::Base
end
# Usage
Document.create(title: "Cats and Dogs", body: "are nice!")
## all documents matching 'cat & dog'
Document.where("to_tsvector('english', title || ' ' || body) @@ to_tsquery(?)",
"cat & dog")
```
Views
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