Default scope¤Î±»º¦ˆó¸æ
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The document discusses issues with default_scope in ActiveRecord when joining tables. Default scopes add conditions automatically that can't easily be removed. The presenter demonstrates different ways to try removing the default scope condition, such as unscoped, except, and unscope, but these don't work when includes or joins are used. The solution is to set the default_scopes array to empty for a subclass to remove the default scope. Default scopes can be convenient for single models but cause problems for more complex queries involving joins. Careful consideration of scopes is advised to avoid these issues.
![default_scope
class Item < ActiveRecord::Base
default_scope -> { order(:order_no) }
end
irb(main)> Item.find(1)
SELECT "items".* FROM ¡°items"
WHERE "items"."id" = ?
ORDER BY ¡°items"."order_no"
DESC LIMIT 1 [["id", 1]]
https://www.?ickr.com/photos/lintmachine/3652702115](https://image.slidesharecdn.com/defaultscope-150328140356-conversion-gate01/85/Default-scope-5-320.jpg)
![https://www.?ickr.com/photos/lintmachine/3652702115
unscoped
irb(main)> Item.unscoped.find(1)
SELECT "items".* FROM ¡°items"
WHERE "items"."id" = ?
DESC LIMIT 1 [["id", 1]]
irb(main)> Item.unscoped { Item.find(1) }
SELECT "items".* FROM ¡°items"
WHERE "items"."id" = ?
LIMIT 1 [["id", 1]]](https://image.slidesharecdn.com/defaultscope-150328140356-conversion-gate01/85/Default-scope-9-320.jpg)
![https://www.?ickr.com/photos/lintmachine/3652702115
except
irb(main)> Item.except(:order).find(1)
SELECT "items".* FROM ¡°items"
WHERE "items"."id" = ?
DESC LIMIT 1 [["id", 1]]](https://image.slidesharecdn.com/defaultscope-150328140356-conversion-gate01/85/Default-scope-10-320.jpg)
![https://www.?ickr.com/photos/lintmachine/3652702115
unscope
irb(main)> Item.unscope(:order).find(1)
SELECT "items".* FROM ¡°items"
WHERE "items"."id" = ?
DESC LIMIT 1 [["id", 1]]](https://image.slidesharecdn.com/defaultscope-150328140356-conversion-gate01/85/Default-scope-11-320.jpg)
![https://www.?ickr.com/photos/lintmachine/3652702115
includes¤·¤Æ¤ß¤ë¤¾
irb(main)> Post.includes(:author)
.where(status: :ok)
.where(authors: {name: ¡®a¡¯})
SELECT "posts"."id" AS t0_r0, ¡
FROM "posts"
LEFT OUTER JOIN "authors"
ON "authors"."id" = ¡°posts"."author_id"
AND "authors"."status" = ?
WHERE "authors"."name" = ?
[["status", 1], ["name", "a"]]](https://image.slidesharecdn.com/defaultscope-150328140356-conversion-gate01/85/Default-scope-17-320.jpg)
![https://www.?ickr.com/photos/lintmachine/3652702115
unscoped
irb(main)> Author.unscoped {
Post.includes(:author)
.where(status: :ok)
.where(authors: {name: ¡®a¡¯}) }
SELECT "posts"."id" AS t0_r0, ¡
FROM "posts"
LEFT OUTER JOIN "authors"
ON "authors"."id" = ¡°posts"."author_id"
AND "authors"."status" = ?
WHERE "authors"."name" = ?
[["status", 1], ["name", "a"]]](https://image.slidesharecdn.com/defaultscope-150328140356-conversion-gate01/85/Default-scope-18-320.jpg)
![https://www.?ickr.com/photos/lintmachine/3652702115
except
irb(main)>
Post.includes(:author).except(:where)
.where(status: :ok)
.where(authors: {name: ¡®a¡¯})
SELECT "posts"."id" AS t0_r0, ¡
FROM "posts"
LEFT OUTER JOIN "authors"
ON "authors"."id" = ¡°posts"."author_id"
AND "authors"."status" = ?
WHERE "authors"."name" = ?
[["status", 1], ["name", "a"]]](https://image.slidesharecdn.com/defaultscope-150328140356-conversion-gate01/85/Default-scope-20-320.jpg)
![https://www.?ickr.com/photos/lintmachine/3652702115
except
irb(main)> Post.includes(:author)
.except(on: :status) #¤Ê¤¤¤è¤Í¡ŸoÒ•¤µ¤ì¤ë
.where(status: :ok)
.where(authors: {name: ¡®a¡¯})
SELECT "posts"."id" AS t0_r0, ¡
FROM "posts"
LEFT OUTER JOIN "authors"
ON "authors"."id" = ¡°posts"."author_id"
AND "authors"."status" = ?
WHERE "authors"."name" = ?
[["status", 1], ["name", "a"]]](https://image.slidesharecdn.com/defaultscope-150328140356-conversion-gate01/85/Default-scope-22-320.jpg)
![https://www.?ickr.com/photos/lintmachine/3652702115
unscope
irb(main)> Post.includes(:author)
.unscope(where: :status)
.where(status: :ok)
.where(authors: {name: ¡®a¡¯})
SELECT "posts"."id" AS t0_r0 ¡
FROM "posts"
LEFT OUTER JOIN "authors"
ON "authors"."id" = "posts"."author_id"
AND "authors"."status" = ?
WHERE "authors"."name" = ?
[["status", 1], ["name", "a"]]](https://image.slidesharecdn.com/defaultscope-150328140356-conversion-gate01/85/Default-scope-24-320.jpg)
![https://www.?ickr.com/photos/lintmachine/3652702115
„e¤ÎévßB¤Ä¤¯¤Ã¤Æ¡
irb(main)> Post.includes(:unscoped_author)
.where(status: :ok)
.where(authors: {name: ¡®a¡¯})
SELECT "posts"."id" AS t0_r0, ¡
FROM "posts"
LEFT OUTER JOIN "authors"
ON "authors"."id" = ¡°posts"."author_id"
AND "authors"."status" = ?
WHERE "authors"."name" = ?
[["status", 1], ["name", "a"]]](https://image.slidesharecdn.com/defaultscope-150328140356-conversion-gate01/85/Default-scope-26-320.jpg)
![default_scopes =[]
class Author < ActiveRecord::Base
has_many :posts
default_scope -> { where(status: :ok) }
end
class UnscopedAuthor < Author
# ¡ý¤³¤³¤¬¥Ý¥¤¥ó¥È
self.default_scopes = []
end
class Post < ActiveRecord::Base
belongs_to :author
belongs_to :unscoped_author,
foreign_key :author_id
end https://www.?ickr.com/photos/lintmachine/3652702115](https://image.slidesharecdn.com/defaultscope-150328140356-conversion-gate01/85/Default-scope-31-320.jpg)
Default scope¤Î±»º¦ˆó¸æ
- 2. ×Ô¼º½B½é ? ŸoÁ¿¾®?½¡(¤à¤ê¤ç¤¦¤¤?¤±¤ó) ? ÓÀºÍ¥·¥¹¥Æ¥à¥Þ¥Í¥¸¥á¥ó¥È 7¥öÔÂÄ¿ ? RubyévÎ÷, évÎ÷Ruby»á×h04?05, ¤ë¤Ó¤Þ etc ? ÐÝÈդϡ¢µÍ™C„ÓÐÍÇÞ¤¿¤¤ê¶þ•rég¥µ¥¹¥Ú¥ó¥¹ŽüÈË
- 5. default_scope class Item < ActiveRecord::Base default_scope -> { order(:order_no) } end irb(main)> Item.find(1) SELECT "items".* FROM ¡°items" WHERE "items"."id" = ? ORDER BY ¡°items"."order_no" DESC LIMIT 1 [["id", 1]] https://www.?ickr.com/photos/lintmachine/3652702115
- 9. https://www.?ickr.com/photos/lintmachine/3652702115 unscoped irb(main)> Item.unscoped.find(1) SELECT "items".* FROM ¡°items" WHERE "items"."id" = ? DESC LIMIT 1 [["id", 1]] irb(main)> Item.unscoped { Item.find(1) } SELECT "items".* FROM ¡°items" WHERE "items"."id" = ? LIMIT 1 [["id", 1]]
- 10. https://www.?ickr.com/photos/lintmachine/3652702115 except irb(main)> Item.except(:order).find(1) SELECT "items".* FROM ¡°items" WHERE "items"."id" = ? DESC LIMIT 1 [["id", 1]]
- 11. https://www.?ickr.com/photos/lintmachine/3652702115 unscope irb(main)> Item.unscope(:order).find(1) SELECT "items".* FROM ¡°items" WHERE "items"."id" = ? DESC LIMIT 1 [["id", 1]]
- 16. includes¤·¤Æ¤ß¤ë¤¾ class Author < ActiveRecord::Base has_many :posts default_scope -> { where(status: :ok) } end class Post < ActiveRecord::Base belongs_to :author end https://www.?ickr.com/photos/lintmachine/3652702115
- 17. https://www.?ickr.com/photos/lintmachine/3652702115 includes¤·¤Æ¤ß¤ë¤¾ irb(main)> Post.includes(:author) .where(status: :ok) .where(authors: {name: ¡®a¡¯}) SELECT "posts"."id" AS t0_r0, ¡ FROM "posts" LEFT OUTER JOIN "authors" ON "authors"."id" = ¡°posts"."author_id" AND "authors"."status" = ? WHERE "authors"."name" = ? [["status", 1], ["name", "a"]]
- 18. https://www.?ickr.com/photos/lintmachine/3652702115 unscoped irb(main)> Author.unscoped { Post.includes(:author) .where(status: :ok) .where(authors: {name: ¡®a¡¯}) } SELECT "posts"."id" AS t0_r0, ¡ FROM "posts" LEFT OUTER JOIN "authors" ON "authors"."id" = ¡°posts"."author_id" AND "authors"."status" = ? WHERE "authors"."name" = ? [["status", 1], ["name", "a"]]
- 20. https://www.?ickr.com/photos/lintmachine/3652702115 except irb(main)> Post.includes(:author).except(:where) .where(status: :ok) .where(authors: {name: ¡®a¡¯}) SELECT "posts"."id" AS t0_r0, ¡ FROM "posts" LEFT OUTER JOIN "authors" ON "authors"."id" = ¡°posts"."author_id" AND "authors"."status" = ? WHERE "authors"."name" = ? [["status", 1], ["name", "a"]]
- 22. https://www.?ickr.com/photos/lintmachine/3652702115 except irb(main)> Post.includes(:author) .except(on: :status) #¤Ê¤¤¤è¤Í¡ŸoÒ•¤µ¤ì¤ë .where(status: :ok) .where(authors: {name: ¡®a¡¯}) SELECT "posts"."id" AS t0_r0, ¡ FROM "posts" LEFT OUTER JOIN "authors" ON "authors"."id" = ¡°posts"."author_id" AND "authors"."status" = ? WHERE "authors"."name" = ? [["status", 1], ["name", "a"]]
- 23. https://www.?ickr.com/photos/lintmachine/3652702115 unscope irb(main)> Post.includes(:author) .unscope(on: :status) #¤Ê¤¤¤è¤Í¡ .where(status: :ok) .where(authors: {name: ¡®a¡¯}) ArgumentError: Hash arguments in .unscope(*args) must have :where as the key.
- 24. https://www.?ickr.com/photos/lintmachine/3652702115 unscope irb(main)> Post.includes(:author) .unscope(where: :status) .where(status: :ok) .where(authors: {name: ¡®a¡¯}) SELECT "posts"."id" AS t0_r0 ¡ FROM "posts" LEFT OUTER JOIN "authors" ON "authors"."id" = "posts"."author_id" AND "authors"."status" = ? WHERE "authors"."name" = ? [["status", 1], ["name", "a"]]
- 25. „e¤ÎévßB¤Ä¤¯¤Ã¤Æ¡ class Author < ActiveRecord::Base has_many :posts default_scope -> { where(status: :ok) } end class Post < ActiveRecord::Base belongs_to :author belongs_to :unscoped_author, -> { unscope(where: :status) }, foreign_key: :author_id, class_name: ¡®Author¡¯ end https://www.?ickr.com/photos/lintmachine/3652702115
- 26. https://www.?ickr.com/photos/lintmachine/3652702115 „e¤ÎévßB¤Ä¤¯¤Ã¤Æ¡ irb(main)> Post.includes(:unscoped_author) .where(status: :ok) .where(authors: {name: ¡®a¡¯}) SELECT "posts"."id" AS t0_r0, ¡ FROM "posts" LEFT OUTER JOIN "authors" ON "authors"."id" = ¡°posts"."author_id" AND "authors"."status" = ? WHERE "authors"."name" = ? [["status", 1], ["name", "a"]]
- 31. default_scopes =[] class Author < ActiveRecord::Base has_many :posts default_scope -> { where(status: :ok) } end class UnscopedAuthor < Author # ¡ý¤³¤³¤¬¥Ý¥¤¥ó¥È self.default_scopes = [] end class Post < ActiveRecord::Base belongs_to :author belongs_to :unscoped_author, foreign_key :author_id end https://www.?ickr.com/photos/lintmachine/3652702115
- 32. default_scope¤µ¤ó¡ ? ¤³¤ó¤ÊÁF¤¬¤¢¤ê¤Þ¤·¤¿¡ ? …gÒ»¥â¥Ç¥ë¤·¤«—ÊË÷¤·¤Ê¤¤ég¤Ï±ãÀû¤µ¤·¤«¸Ð¤¸¤Ê¤¤ ¤«¤â¤·¤ì¤Þ¤»¤ó¤¬¡SQLµÄ¤ËJOIN¤¹¤ë¤³¤È¤Ë¤Ê¤ë ¤ÈÃæµ¹¤Ê¤³¤È¤Ë¤Ê¤ê¤Þ¤¹(¤Ê¤ê¤Þ¤·¤¿) ? ÉÙ¤·Ãæµ¹¤Ê¥¯¥¨¥ê¤ò¿¼¤¨¤ë¤È¤¤ËÖ±Ã椹¤ë¤Î¤Ç¤¹¤è ¡¤³¤Î†–î} ? áá»Ú¤·¤Ê¤¤¤è¤¦¤Ë¡¢scope¤òš°»Ø¤Ä¤±¤ë¤«ÔOÓ‹¤ò ÒŠÖ±¤¹¤Û¤¦¤¬Á¼¤¤¤È˼¤¤¤Þ¤¹ https://www.?ickr.com/photos/71508688@N00/5139944772