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我刚刚注意到，在具有joins的查询上使用.size或.count会产生意外的结果。使用activerecord连接后计算对象
User.some_scope.size #=> 10
User.joins(:associations).some_scope.size #=> 10 + associated object count
无论我加入表格，我如何获得适合范围的用户数？
一些实际代码：
class User < ActiveRecord::Base
has_many :tracking_logs, class_name: "Tracking::Log", dependent: :destroy
end
class Tracking::Log < ActiveRecord::Base
belongs_to :user
end
User.where(created_at: Time.now-1.day..Time.now).size #=> 18
SQL: SELECT COUNT(*) FROM "users" WHERE ("users"."created_at" BETWEEN '2015-05-25 10:40:11.423142' AND '2015-05-26 10:40:11.423741')
User.joins(:tracking_logs).where(created_at: Time.now-1.day..Time.now).size #=> 3188
SQL: SELECT COUNT(*) FROM "users" INNER JOIN "tracking_logs" ON "tracking_logs"."user_id" = "users"."id" WHERE ("users"."created_at" BETWEEN '2015-05-25 10:41:15.260113' AND '2015-05-26 10:41:15.260684')
我希望.size将只适用于基本模型我呼吁查询，别的就是混乱。
NB，明确要检查哪个模型的created_at不会改变结果，例如，
User.joins(:tracking_logs).where(users: { created_at: Time.now-1.day..Time.now }).size #=> 3188
SQL: SELECT COUNT(*) FROM "users" INNER JOIN "tracking_logs" ON "tracking_logs"."user_id" = "users"."id" WHERE ("users"."created_at" BETWEEN '2015-05-25 10:49:29.485508' AND '2015-05-26 10:49:29.486120')
User attributes:
:id => :integer,
:category => :string,
:email => :string,
:created_at => :datetime,
:updated_at => :datetime,
:locale => :string,
:original_email => :text,
:registration_id => :integer,
:first_name => :text,
:login_count => :integer,
:offer_type => :text,
:cid => :string,
:fb_like_status => :integer,
:product_purchases => :text
Tracking::Log attributes:
:id => :integer,
:user_id => :integer,
:tracking_referer_id => :integer,
:to => :string,
:controller_name => :string,
:action_name => :string,
:tracking_activity_id => :integer,
:time_since_last_log => :integer,
:created_at => :datetime,
:updated_at => :datetime
是，同样的结果。 – Epigene
你能提供一些你的代码吗？就像它发生的模型和数据一样？我似乎无法重现这个问题。 – IngoAlbers
同样在这里。你可以尝试使用'ActiveRecord :: Base.logger = Logger.new（STDOUT）'开启日志记录并显示为第一个和第二个查询生成的SQL吗？ – SkyWriter