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在 Ruby on Rails 框架中使用 PostgreSQL 特定資料類型
2024/05/06 00:43
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Ruby on Rails 是一個使用 Ruby 語言編寫的開源 Web 應用程式框架。

PostgreSQL 是一個強大、開源的物件關聯式資料庫系統,擁有超過 35 年的活躍開發歷程,並以其可靠性、功能強大性和效能而享有盛譽。

PostgreSQL 提供許多特定資料類型,以下是 Rails 支援的 PostgreSQL 類型清單。

1. Bytea

# db/migrate/20140207133952_create_documents.rb create_table :documents do |t| t.binary payload end 
# app/models/document.rb class Document < ApplicationRecord end 
# Usage data = File.read(Rails.root + "tmp/output.pdf") Document.create payload: data 

2. 陣列

# db/migrate/20140207133952_create_books.rb create_table :books do |t| t.string title t.string tags, array: true t.integer ratings, array: true end add_index :books, :tags, using: gin add_index :books, :ratings, using: gin 
# app/models/book.rb class Book < ApplicationRecord 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") 

3. Hstore

需要啟用 hstore 擴充功能才能使用 hstore

# db/migrate/20131009135255_create_profiles.rb class CreateProfiles < ActiveRecord::Migration[7.0] enable_extension hstore unless extension_enabled?(hstore) create_table :profiles do |t| t.hstore settings end end 
# app/models/profile.rb class Profile < ApplicationRecord end 
irb> Profile.create(settings: { "color" => "blue", "resolution" => "800x600" })  irb> profile = Profile.first irb> profile.settings => {"color"=>"blue", "resolution"=>"800x600"} irb> profile.settings = {"color" => "yellow", "resolution" => "1280x1024"} irb> profile.save!  irb> Profile.where("settings->color = ?", "yellow") => #<ActiveRecord::Relation [#<Profile id: 1, settings: {"color"=>"yellow", "resolution"=>"1280x1024"}>]> 

4. JSON 和 JSONB

# db/migrate/20131220144913_create_events.rb # ... for json datatype: create_table :events do |t| t.json payload end # ... or for jsonb datatype: create_table :events do |t| t.jsonb payload end 
# app/models/event.rb class Event < ApplicationRecord end 
irb> Event.create(payload: { kind: "user_renamed", change: ["jack", "john"]})  irb> event = Event.first irb> event.payload => {"kind"=>"user_renamed", "change"=>["jack", "john"]} ## Query based on JSON document # The -> operator returns the original JSON type (which might be an object), whereas ->> returns text irb> Event.where("payload->>kind = ?", "user_renamed") 

5. 範圍類型

此類型對應到 Ruby Range 物件。

# db/migrate/20130923065404_create_events.rb create_table :events do |t| t.daterange duration end 
# app/models/event.rb class Event < ApplicationRecord end 
irb> Event.create(duration: Date.new(2014, 2, 11)..Date.new(2014, 2, 12)) irb> event = Event.first irb> event.duration => Tue, 11 Feb 2014...Thu, 13 Feb 2014 ## All Events on a given date irb> Event.where("duration @> ?::date", Date.new(2014, 2, 12)) ## Working with range bounds irb> event = Event.select("lower(duration) AS starts_at").select("upper(duration) AS ends_at").first irb> event.starts_at => Tue, 11 Feb 2014 irb> event.ends_at => Thu, 13 Feb 2014 

6. 複合類型

目前沒有特別支援複合類型,它們對應到一般的文字欄位。

CREATE TYPE full_address AS ( city VARCHAR(90), street VARCHAR(90) ); 
# 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 < ApplicationRecord end 
irb> Contact.create address: "(Paris,Champs-Élysées)" irb> contact = Contact.first irb> contact.address => "(Paris,Champs-Élysées)" irb> contact.address = "(Paris,Rue Basse)" irb> contact.save! 

7. 列舉類型

類型可以對應到一般的文字欄位,或對應到 ActiveRecord::Enum

# db/migrate/20131220144913_create_articles.rb def change create_enum :article_status, ["draft", "published", "archived"] create_table :articles do |t| t.enum :status, enum_type: :article_status, default: "draft", null: false end end 

你也可以建立列舉類型,並將列舉欄位新增到現有的資料表。

# db/migrate/20230113024409_add_status_to_articles.rb def change create_enum :article_status, ["draft", "published", "archived"] add_column :articles, :status, :enum, enum_type: :article_status, default: "draft", null: false end 

上述的遷移都是可逆的,但你可以在需要時定義個別的 #up 和 #down 方法。請務必在刪除列舉類型之前移除任何依賴於該列舉類型的欄位或資料表。

def down drop_table :articles # OR: remove_column :articles, :status drop_enum :article_status end 

在模型中宣告列舉屬性會新增輔助方法,並防止將無效值指定給類別的執行個體。

# app/models/article.rb class Article < ApplicationRecord enum :status, { draft: "draft", published: "published", archived: "archived" }, prefix: true end 
irb> article = Article.create irb> article.status => "draft" # default status from PostgreSQL, as defined in migration above irb> article.status_published! irb> article.status => "published" irb> article.status_archived? => false irb> article.status = "deleted" ArgumentError: deleted is not a valid status 

要重新命名列舉,你可以使用 rename_enum,並同時更新任何模型用法。

# db/migrate/20150718144917_rename_article_status.rb def change rename_enum :article_status, to: :article_state end 

要新增新值,你可以使用 add_enum_value

# db/migrate/20150720144913_add_new_state_to_articles.rb def up add_enum_value :article_state, "archived" # will be at the end after published add_enum_value :article_state, "in review", before: "published" add_enum_value :article_state, "approved", after: "in review" end 

列舉值無法刪除,這也表示 add_enum_value 是不可逆的。

若要重新命名值,可以使用 rename_enum_value

# db/migrate/20150722144915_rename_article_state.rb def change rename_enum_value :article_state, from: "archived", to: "deleted" end 

提示:若要顯示所有列舉的所有值,可以在 bin/rails db 或 psql 主控台中呼叫此查詢。

SELECT n.nspname AS enum_schema, t.typname AS enum_name, e.enumlabel AS enum_value FROM pg_type t JOIN pg_enum e ON t.oid = e.enumtypid JOIN pg_catalog.pg_namespace n ON n.oid = t.typnamespace 

8. UUID

如果你使用的是早於版本 13.0 的 PostgreSQL,你可能需要啟用特殊擴充功能才能使用 UUID。啟用 pgcrypto 擴充功能(PostgreSQL >= 9.4)或 uuid-ossp 擴充功能(適用於更早的版本)。

# db/migrate/20131220144913_create_revisions.rb create_table :revisions do |t| t.uuid :identifier end 
# app/models/revision.rb class Revision < ApplicationRecord end 
irb> Revision.create identifier: "A0EEBC99-9C0B-4EF8-BB6D-6BB9BD380A11"  irb> revision = Revision.first irb> revision.identifier => "a0eebc99-9c0b-4ef8-bb6d-6bb9bd380a11" 

你可以在遷移中使用 uuid 類型來定義參考。

# db/migrate/20150418012400_create_blog.rb enable_extension pgcrypto unless extension_enabled?(pgcrypto) create_table :posts, id: :uuid create_table :comments, id: :uuid do |t| # t.belongs_to :post, type: :uuid t.references :post, type: :uuid end 
# app/models/post.rb class Post < ApplicationRecord has_many :comments end 
# app/models/comment.rb class Comment < ApplicationRecord belongs_to :post end 

9. 位元字串類型

# db/migrate/20131220144913_create_users.rb create_table :users, force: true do |t| t.column :settings, "bit(8)" end 
# app/models/user.rb class User < ApplicationRecord end 
irb> User.create settings: "01010011" irb> user = User.first irb> user.settings => "01010011" irb> user.settings = "0xAF" irb> user.settings => "10101111" irb> user.save! 

10. 網路位址類型

inet 和 cidr 類型會對應到 Ruby IPAddr 物件。macaddr 類型會對應到一般文字。

# db/migrate/20140508144913_create_devices.rb create_table(:devices, force: true) do |t| t.inet ip t.cidr network t.macaddr address end 
# app/models/device.rb class Device < ApplicationRecord end 
irb> macbook = Device.create(ip: "192.168.1.12", network: "192.168.2.0/24", address: "32:01:16:6d:05:ef")  irb> macbook.ip => #<IPAddr: IPv4:192.168.1.12/255.255.255.255> irb> macbook.network => #<IPAddr: IPv4:192.168.2.0/255.255.255.0> irb> macbook.address => "32:01:16:6d:05:ef" 

11. 幾何類型

除了 points 之外,所有幾何類型都會對應到一般文字。點會轉換為包含 x 和 y 座標的陣列。

12. 間隔

此類型會對應到 ActiveSupport::Duration 物件。

# db/migrate/20200120000000_create_events.rb create_table :events do |t| t.interval duration end 
# app/models/event.rb class Event < ApplicationRecord end 
irb> Event.create(duration: 2.days)  irb> event = Event.first irb> event.duration => 2 days

https://chihyuanyip.github.io/2024/05/05/using-postgresql-specific-data-types-in-the-ruby-on-rails-framework.html

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6樓. 環保阿嬤金鳳姨
2024/06/01 11:56
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環保阿嬤金鳳姨
5樓. 環保阿嬤金鳳姨
2024/05/30 16:18
祝福您健康快樂, 
4樓. 環保阿嬤金鳳姨
2024/05/25 15:04
祝您時時開心天天快樂, 
3樓. 麥克侯
2024/05/17 15:35

有時真的隔行如隔山,還得有興趣,才有研究的動力。

謝謝分享!

2樓. 環保阿嬤金鳳姨
2024/05/12 13:34
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祝福天下母親每天都是快樂的


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1樓. 亦言亦詩
2024/05/12 02:05

比較Java, Scala等,Ruby有優越性嗎?

我的印象,Ruby的使用者不多。


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