Question

如何在使用kaminari进行分页时使用预先加载？我知道kaminari需要Relation个对象才能工作，如何检索模型：include并返回Relation个对象？
第二个问题，为什么：include为evry定义的模型创建sql查询而不是创建一个大的连接查询？

# match.rb
class Match < ActiveRecord::Base
  has_many :rounds
  has_many :participations
  has_many :players, :through => :participations
  has_many :scores
  has_many :clans, :through => :scores
  belongs_to :clan_1, :class_name => "Clan", :foreign_key => "clan_1_id"
  belongs_to :clan_2, :class_name => "Clan", :foreign_key => "clan_2_id"
  belongs_to :winner, :class_name => "Clan", :foreign_key => "winner_id"
  belongs_to :league
  belongs_to :tournament

# matches_controller.rb
@matches = Match.all(:include=>[:clans,:scores])

这是Match.includes(:clans)的日志输出：

Match Load (18.2ms)  SELECT "matches".* FROM "matches"
Score Load (4.5ms)  SELECT "scores".* FROM "scores" WHERE ("scores".match_id IN (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115))
Clan Load (0.5ms)  SELECT "clans".* FROM "clans" WHERE ("clans"."id" IN (1,7,9,2,5,3,4,8,10,6,11,12,13,14,15,16,17,18,19,20))

Answer 1

在Rails 3.x中有新的查询语法。所以试试这个

@matches = Match.includes(:clans,:scores)

Answer 2

试试这个：

@matches = Match.includes([:clans,:scores]).all()
@matches_paginated = Kaminari.paginate_array(@matches).page(params[:page] || 1).per(20)

# And then
@matches_paginated.each do |m|
  m.clans.each do |c| # should not generate a new query
    c.name # should not generate a new query
  end
end

唯一的问题是，这会急切地加载所有其他页面（你真的不需要）

Rails渴望装载和kaminari

2 个答案: