rails named_scope ignores eager loading
- by Craig
Two models (Rails 2.3.8):
User; username & disabled properties; User has_one :profile
Profile; full_name & hidden properties
I am trying to create a named_scope that eliminate the disabled=1 and hidden=1 User-Profiles. The User model is usually used in conjunction with the Profile model, so I attempt to eager-load the Profile model (:include = :profile).
I created a named_scope on the User model called 'visible':
named_scope :visible, {
:joins => "INNER JOIN profiles ON users.id=profiles.user_id",
:conditions => ["users.disabled = ? AND profiles.hidden = ?", false, false]
}
I've noticed that when I use the named_scope in a query, the eager-loading instruction is ignored.
Variation 1 - User model only:
# UserController
@users = User.find(:all)
# User's Index view
<% for user in @users %>
<p><%= user.username %></p>
<% end %>
# generates a single query:
SELECT * FROM `users`
Variation 2 - use Profile model in view; lazy load Profile model
# UserController
@users = User.find(:all)
# User's Index view
<% for user in @users %>
<p><%= user.username %></p>
<p><%= user.profile.full_name %></p>
<% end %>
# generates multiple queries:
SELECT * FROM `profiles` WHERE (`profiles`.user_id = 1) ORDER BY full_name ASC LIMIT 1
SHOW FIELDS FROM `profiles`
SELECT * FROM `profiles` WHERE (`profiles`.user_id = 2) ORDER BY full_name ASC LIMIT 1
SELECT * FROM `profiles` WHERE (`profiles`.user_id = 3) ORDER BY full_name ASC LIMIT 1
SELECT * FROM `profiles` WHERE (`profiles`.user_id = 4) ORDER BY full_name ASC LIMIT 1
SELECT * FROM `profiles` WHERE (`profiles`.user_id = 5) ORDER BY full_name ASC LIMIT 1
SELECT * FROM `profiles` WHERE (`profiles`.user_id = 6) ORDER BY full_name ASC LIMIT 1
Variation 3 - eager load Profile model
# UserController
@users = User.find(:all, :include => :profile)
#view; no changes
# two queries
SELECT * FROM `users`
SELECT `profiles`.* FROM `profiles` WHERE (`profiles`.user_id IN (1,2,3,4,5,6))
Variation 4 - use name_scope, including eager-loading instruction
#UserConroller
@users = User.visible(:include => :profile)
#view; no changes
# generates multiple queries
SELECT `users`.* FROM `users` INNER JOIN profiles ON users.id=profiles.user_id WHERE (users.disabled = 0 AND profiles.hidden = 0)
SELECT * FROM `profiles` WHERE (`profiles`.user_id = 1) ORDER BY full_name ASC LIMIT 1
SELECT * FROM `profiles` WHERE (`profiles`.user_id = 2) ORDER BY full_name ASC LIMIT 1
SELECT * FROM `profiles` WHERE (`profiles`.user_id = 3) ORDER BY full_name ASC LIMIT 1
SELECT * FROM `profiles` WHERE (`profiles`.user_id = 4) ORDER BY full_name ASC LIMIT 1
Variation 4 does return the correct number of records, but also appears to be ignoring the eager-loading instruction.
Is this an issue with cross-model named scopes? Perhaps I'm not using it correctly.
Is this sort of situation handled better by Rails 3?
