655 lines
16 KiB
Markdown
655 lines
16 KiB
Markdown
**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON https://guides.rubyonrails.org.**
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Active Record and PostgreSQL
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============================
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This guide covers PostgreSQL specific usage of Active Record.
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After reading this guide, you will know:
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* How to use PostgreSQL's datatypes.
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* How to use UUID primary keys.
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* How to implement full text search with PostgreSQL.
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* How to back your Active Record models with database views.
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--------------------------------------------------------------------------------
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In order to use the PostgreSQL adapter you need to have at least version 9.3
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installed. Older versions are not supported.
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To get started with PostgreSQL have a look at the
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[configuring Rails guide](configuring.html#configuring-a-postgresql-database).
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It describes how to properly set up Active Record for PostgreSQL.
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Datatypes
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---------
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PostgreSQL offers a number of specific datatypes. Following is a list of types,
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that are supported by the PostgreSQL adapter.
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### Bytea
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* [type definition](https://www.postgresql.org/docs/current/static/datatype-binary.html)
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* [functions and operators](https://www.postgresql.org/docs/current/static/functions-binarystring.html)
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```ruby
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# db/migrate/20140207133952_create_documents.rb
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create_table :documents do |t|
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t.binary 'payload'
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end
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```
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```ruby
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# app/models/document.rb
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class Document < ApplicationRecord
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end
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```
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```ruby
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# Usage
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data = File.read(Rails.root + "tmp/output.pdf")
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Document.create payload: data
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```
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### Array
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* [type definition](https://www.postgresql.org/docs/current/static/arrays.html)
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* [functions and operators](https://www.postgresql.org/docs/current/static/functions-array.html)
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```ruby
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# db/migrate/20140207133952_create_books.rb
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create_table :books do |t|
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t.string 'title'
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t.string 'tags', array: true
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t.integer 'ratings', array: true
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end
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add_index :books, :tags, using: 'gin'
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add_index :books, :ratings, using: 'gin'
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```
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```ruby
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# app/models/book.rb
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class Book < ApplicationRecord
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end
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```
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```ruby
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# Usage
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Book.create title: "Brave New World",
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tags: ["fantasy", "fiction"],
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ratings: [4, 5]
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## Books for a single tag
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Book.where("'fantasy' = ANY (tags)")
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## Books for multiple tags
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Book.where("tags @> ARRAY[?]::varchar[]", ["fantasy", "fiction"])
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## Books with 3 or more ratings
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Book.where("array_length(ratings, 1) >= 3")
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```
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### Hstore
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* [type definition](https://www.postgresql.org/docs/current/static/hstore.html)
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* [functions and operators](https://www.postgresql.org/docs/current/static/hstore.html#id-1.11.7.26.5)
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NOTE: You need to enable the `hstore` extension to use hstore.
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```ruby
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# db/migrate/20131009135255_create_profiles.rb
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class CreateProfiles < ActiveRecord::Migration[7.0]
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enable_extension 'hstore' unless extension_enabled?('hstore')
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create_table :profiles do |t|
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t.hstore 'settings'
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end
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end
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```
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```ruby
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# app/models/profile.rb
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class Profile < ApplicationRecord
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end
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```
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```irb
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irb> Profile.create(settings: { "color" => "blue", "resolution" => "800x600" })
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irb> profile = Profile.first
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irb> profile.settings
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=> {"color"=>"blue", "resolution"=>"800x600"}
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irb> profile.settings = {"color" => "yellow", "resolution" => "1280x1024"}
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irb> profile.save!
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irb> Profile.where("settings->'color' = ?", "yellow")
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=> #<ActiveRecord::Relation [#<Profile id: 1, settings: {"color"=>"yellow", "resolution"=>"1280x1024"}>]>
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```
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### JSON and JSONB
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* [type definition](https://www.postgresql.org/docs/current/static/datatype-json.html)
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* [functions and operators](https://www.postgresql.org/docs/current/static/functions-json.html)
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```ruby
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# db/migrate/20131220144913_create_events.rb
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# ... for json datatype:
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create_table :events do |t|
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t.json 'payload'
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end
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# ... or for jsonb datatype:
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create_table :events do |t|
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t.jsonb 'payload'
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end
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```
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```ruby
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# app/models/event.rb
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class Event < ApplicationRecord
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end
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```
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```irb
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irb> Event.create(payload: { kind: "user_renamed", change: ["jack", "john"]})
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irb> event = Event.first
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irb> event.payload
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=> {"kind"=>"user_renamed", "change"=>["jack", "john"]}
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## Query based on JSON document
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# The -> operator returns the original JSON type (which might be an object), whereas ->> returns text
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irb> Event.where("payload->>'kind' = ?", "user_renamed")
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```
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### Range Types
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* [type definition](https://www.postgresql.org/docs/current/static/rangetypes.html)
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* [functions and operators](https://www.postgresql.org/docs/current/static/functions-range.html)
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This type is mapped to Ruby [`Range`](https://ruby-doc.org/core-2.7.0/Range.html) objects.
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```ruby
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# db/migrate/20130923065404_create_events.rb
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create_table :events do |t|
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t.daterange 'duration'
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end
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```
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```ruby
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# app/models/event.rb
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class Event < ApplicationRecord
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end
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```
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```irb
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irb> Event.create(duration: Date.new(2014, 2, 11)..Date.new(2014, 2, 12))
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irb> event = Event.first
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irb> event.duration
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=> Tue, 11 Feb 2014...Thu, 13 Feb 2014
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## All Events on a given date
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irb> Event.where("duration @> ?::date", Date.new(2014, 2, 12))
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## Working with range bounds
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irb> event = Event.select("lower(duration) AS starts_at").select("upper(duration) AS ends_at").first
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irb> event.starts_at
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=> Tue, 11 Feb 2014
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irb> event.ends_at
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=> Thu, 13 Feb 2014
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```
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### Composite Types
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* [type definition](https://www.postgresql.org/docs/current/static/rowtypes.html)
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Currently there is no special support for composite types. They are mapped to
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normal text columns:
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```sql
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CREATE TYPE full_address AS
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(
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city VARCHAR(90),
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street VARCHAR(90)
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);
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```
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```ruby
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# db/migrate/20140207133952_create_contacts.rb
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execute <<-SQL
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CREATE TYPE full_address AS
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(
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city VARCHAR(90),
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street VARCHAR(90)
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);
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SQL
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create_table :contacts do |t|
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t.column :address, :full_address
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end
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```
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```ruby
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# app/models/contact.rb
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class Contact < ApplicationRecord
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end
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```
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```irb
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irb> Contact.create address: "(Paris,Champs-Élysées)"
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irb> contact = Contact.first
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irb> contact.address
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=> "(Paris,Champs-Élysées)"
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irb> contact.address = "(Paris,Rue Basse)"
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irb> contact.save!
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```
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### Enumerated Types
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* [type definition](https://www.postgresql.org/docs/current/static/datatype-enum.html)
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The type can be mapped as a normal text column, or to an [`ActiveRecord::Enum`](https://api.rubyonrails.org/classes/ActiveRecord/Enum.html).
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```ruby
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# db/migrate/20131220144913_create_articles.rb
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def up
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create_enum :article_status, ["draft", "published"]
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create_table :articles do |t|
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t.enum :status, enum_type: :article_status, default: "draft", null: false
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end
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end
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# There's no built in support for dropping enums, but you can do it manually.
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# You should first drop any table that depends on them.
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def down
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drop_table :articles
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execute <<-SQL
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DROP TYPE article_status;
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SQL
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end
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```
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```ruby
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# app/models/article.rb
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class Article < ApplicationRecord
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enum status: {
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draft: "draft", published: "published"
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}, _prefix: true
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end
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```
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```irb
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irb> Article.create status: "draft"
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irb> article = Article.first
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irb> article.status_draft!
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irb> article.status
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=> "draft"
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irb> article.status_published?
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=> false
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```
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To add a new value before/after existing one you should use [ALTER TYPE](https://www.postgresql.org/docs/current/static/sql-altertype.html):
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```ruby
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# db/migrate/20150720144913_add_new_state_to_articles.rb
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# NOTE: ALTER TYPE ... ADD VALUE cannot be executed inside of a transaction block so here we are using disable_ddl_transaction!
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disable_ddl_transaction!
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def up
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execute <<-SQL
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ALTER TYPE article_status ADD VALUE IF NOT EXISTS 'archived' AFTER 'published';
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SQL
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end
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```
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NOTE: Enum values can't be dropped. You can read why [here](https://www.postgresql.org/message-id/29F36C7C98AB09499B1A209D48EAA615B7653DBC8A@mail2a.alliedtesting.com).
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Hint: to show all the values of the all enums you have, you should call this query in `bin/rails db` or `psql` console:
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```sql
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SELECT n.nspname AS enum_schema,
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t.typname AS enum_name,
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e.enumlabel AS enum_value
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FROM pg_type t
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JOIN pg_enum e ON t.oid = e.enumtypid
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JOIN pg_catalog.pg_namespace n ON n.oid = t.typnamespace
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```
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### UUID
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* [type definition](https://www.postgresql.org/docs/current/static/datatype-uuid.html)
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* [pgcrypto generator function](https://www.postgresql.org/docs/current/static/pgcrypto.html)
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* [uuid-ossp generator functions](https://www.postgresql.org/docs/current/static/uuid-ossp.html)
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NOTE: You need to enable the `pgcrypto` (only PostgreSQL >= 9.4) or `uuid-ossp`
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extension to use uuid.
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```ruby
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# db/migrate/20131220144913_create_revisions.rb
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create_table :revisions do |t|
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t.uuid :identifier
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end
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```
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```ruby
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# app/models/revision.rb
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class Revision < ApplicationRecord
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end
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```
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```irb
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irb> Revision.create identifier: "A0EEBC99-9C0B-4EF8-BB6D-6BB9BD380A11"
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irb> revision = Revision.first
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irb> revision.identifier
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=> "a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11"
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```
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You can use `uuid` type to define references in migrations:
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```ruby
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# db/migrate/20150418012400_create_blog.rb
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enable_extension 'pgcrypto' unless extension_enabled?('pgcrypto')
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create_table :posts, id: :uuid
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create_table :comments, id: :uuid do |t|
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# t.belongs_to :post, type: :uuid
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t.references :post, type: :uuid
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end
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```
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```ruby
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# app/models/post.rb
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class Post < ApplicationRecord
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has_many :comments
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end
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```
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```ruby
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# app/models/comment.rb
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class Comment < ApplicationRecord
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belongs_to :post
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end
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```
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See [this section](#uuid-primary-keys) for more details on using UUIDs as primary key.
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### Bit String Types
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* [type definition](https://www.postgresql.org/docs/current/static/datatype-bit.html)
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* [functions and operators](https://www.postgresql.org/docs/current/static/functions-bitstring.html)
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```ruby
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# db/migrate/20131220144913_create_users.rb
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create_table :users, force: true do |t|
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t.column :settings, "bit(8)"
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end
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```
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```ruby
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# app/models/user.rb
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class User < ApplicationRecord
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end
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```
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```irb
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irb> User.create settings: "01010011"
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irb> user = User.first
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irb> user.settings
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=> "01010011"
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irb> user.settings = "0xAF"
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irb> user.settings
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=> "10101111"
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irb> user.save!
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```
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### Network Address Types
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* [type definition](https://www.postgresql.org/docs/current/static/datatype-net-types.html)
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The types `inet` and `cidr` are mapped to Ruby
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[`IPAddr`](https://ruby-doc.org/stdlib-2.7.0/libdoc/ipaddr/rdoc/IPAddr.html)
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objects. The `macaddr` type is mapped to normal text.
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```ruby
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# db/migrate/20140508144913_create_devices.rb
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create_table(:devices, force: true) do |t|
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t.inet 'ip'
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t.cidr 'network'
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t.macaddr 'address'
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end
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```
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```ruby
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# app/models/device.rb
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class Device < ApplicationRecord
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end
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```
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```irb
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irb> macbook = Device.create(ip: "192.168.1.12", network: "192.168.2.0/24", address: "32:01:16:6d:05:ef")
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irb> macbook.ip
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=> #<IPAddr: IPv4:192.168.1.12/255.255.255.255>
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irb> macbook.network
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=> #<IPAddr: IPv4:192.168.2.0/255.255.255.0>
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irb> macbook.address
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=> "32:01:16:6d:05:ef"
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```
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### Geometric Types
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* [type definition](https://www.postgresql.org/docs/current/static/datatype-geometric.html)
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All geometric types, with the exception of `points` are mapped to normal text.
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A point is casted to an array containing `x` and `y` coordinates.
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### Interval
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* [type definition](https://www.postgresql.org/docs/current/static/datatype-datetime.html#DATATYPE-INTERVAL-INPUT)
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* [functions and operators](https://www.postgresql.org/docs/current/static/functions-datetime.html)
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This type is mapped to [`ActiveSupport::Duration`](https://api.rubyonrails.org/classes/ActiveSupport/Duration.html) objects.
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```ruby
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# db/migrate/20200120000000_create_events.rb
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create_table :events do |t|
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t.interval 'duration'
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end
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```
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```ruby
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# app/models/event.rb
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class Event < ApplicationRecord
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end
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```
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```irb
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irb> Event.create(duration: 2.days)
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irb> event = Event.first
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irb> event.duration
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=> 2 days
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```
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UUID Primary Keys
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-----------------
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NOTE: You need to enable the `pgcrypto` (only PostgreSQL >= 9.4) or `uuid-ossp`
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extension to generate random UUIDs.
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```ruby
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# db/migrate/20131220144913_create_devices.rb
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enable_extension 'pgcrypto' unless extension_enabled?('pgcrypto')
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create_table :devices, id: :uuid do |t|
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t.string :kind
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end
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```
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```ruby
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# app/models/device.rb
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class Device < ApplicationRecord
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end
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```
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```ruby
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irb> device = Device.create
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irb> device.id
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=> "814865cd-5a1d-4771-9306-4268f188fe9e"
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```
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NOTE: `gen_random_uuid()` (from `pgcrypto`) is assumed if no `:default` option was
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passed to `create_table`.
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Generated Columns
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-----------------
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NOTE: Generated columns are supported since version 12.0 of PostgreSQL.
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```ruby
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# db/migrate/20131220144913_create_users.rb
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create_table :users do |t|
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t.string :name
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t.virtual :name_upcased, type: :string, as: 'upper(name)', stored: true
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end
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# app/models/user.rb
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class User < ApplicationRecord
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end
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# Usage
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user = User.create(name: 'John')
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User.last.name_upcased # => "JOHN"
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```
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Full Text Search
|
|
----------------
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```ruby
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# db/migrate/20131220144913_create_documents.rb
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create_table :documents do |t|
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t.string :title
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t.string :body
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end
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add_index :documents, "to_tsvector('english', title || ' ' || body)", using: :gin, name: 'documents_idx'
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```
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```ruby
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# app/models/document.rb
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class Document < ApplicationRecord
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end
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```
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```ruby
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# Usage
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Document.create(title: "Cats and Dogs", body: "are nice!")
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## all documents matching 'cat & dog'
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|
Document.where("to_tsvector('english', title || ' ' || body) @@ to_tsquery(?)",
|
|
"cat & dog")
|
|
```
|
|
|
|
Optionally, you can store the vector as automatically generated column (from PostgreSQL 12.0):
|
|
|
|
```ruby
|
|
# db/migrate/20131220144913_create_documents.rb
|
|
create_table :documents do |t|
|
|
t.string :title
|
|
t.string :body
|
|
|
|
t.virtual :textsearchable_index_col,
|
|
type: :tsvector, as: "to_tsvector('english', title || ' ' || body)", stored: true
|
|
end
|
|
|
|
add_index :documents, :textsearchable_index_col, using: :gin, name: 'documents_idx'
|
|
|
|
# Usage
|
|
Document.create(title: "Cats and Dogs", body: "are nice!")
|
|
|
|
## all documents matching 'cat & dog'
|
|
Document.where("textsearchable_index_col @@ to_tsquery(?)", "cat & dog")
|
|
```
|
|
|
|
Database Views
|
|
--------------
|
|
|
|
* [view creation](https://www.postgresql.org/docs/current/static/sql-createview.html)
|
|
|
|
Imagine you need to work with a legacy database containing the following table:
|
|
|
|
```
|
|
rails_pg_guide=# \d "TBL_ART"
|
|
Table "public.TBL_ART"
|
|
Column | Type | Modifiers
|
|
------------+-----------------------------+------------------------------------------------------------
|
|
INT_ID | integer | not null default nextval('"TBL_ART_INT_ID_seq"'::regclass)
|
|
STR_TITLE | character varying |
|
|
STR_STAT | character varying | default 'draft'::character varying
|
|
DT_PUBL_AT | timestamp without time zone |
|
|
BL_ARCH | boolean | default false
|
|
Indexes:
|
|
"TBL_ART_pkey" PRIMARY KEY, btree ("INT_ID")
|
|
```
|
|
|
|
This table does not follow the Rails conventions at all.
|
|
Because simple PostgreSQL views are updateable by default,
|
|
we can wrap it as follows:
|
|
|
|
```ruby
|
|
# db/migrate/20131220144913_create_articles_view.rb
|
|
execute <<-SQL
|
|
CREATE VIEW articles AS
|
|
SELECT "INT_ID" AS id,
|
|
"STR_TITLE" AS title,
|
|
"STR_STAT" AS status,
|
|
"DT_PUBL_AT" AS published_at,
|
|
"BL_ARCH" AS archived
|
|
FROM "TBL_ART"
|
|
WHERE "BL_ARCH" = 'f'
|
|
SQL
|
|
```
|
|
|
|
```ruby
|
|
# app/models/article.rb
|
|
class Article < ApplicationRecord
|
|
self.primary_key = "id"
|
|
def archive!
|
|
update_attribute :archived, true
|
|
end
|
|
end
|
|
```
|
|
|
|
```irb
|
|
irb> first = Article.create! title: "Winter is coming", status: "published", published_at: 1.year.ago
|
|
irb> second = Article.create! title: "Brace yourself", status: "draft", published_at: 1.month.ago
|
|
|
|
irb> Article.count
|
|
=> 2
|
|
irb> first.archive!
|
|
irb> Article.count
|
|
=> 1
|
|
```
|
|
|
|
NOTE: This application only cares about non-archived `Articles`. A view also
|
|
allows for conditions so we can exclude the archived `Articles` directly.
|
|
|
|
Structure dumps
|
|
--------------
|
|
|
|
If your `config.active_record.schema_format` is `:sql`, Rails will call `pg_dump` to generate a
|
|
structure dump.
|
|
|
|
You can use `ActiveRecord::Tasks::DatabaseTasks.structure_dump_flags` to configure `pg_dump`.
|
|
For example, to exclude comments from your structure dump, add this to an initializer:
|
|
|
|
```ruby
|
|
ActiveRecord::Tasks::DatabaseTasks.structure_dump_flags = ['--no-comments']
|
|
```
|