Question

我有一个简单的连接查询，在某些情况下返回具有未初始化关联的ActiveRecord对象，我试着理解为什么。（我的设置：使用MySQL的rails 2.3.8）

以下是我的模特：

class Member
has_many :twitter_status_relations
 //has some more unrelated associations
end

class TwitterStatus
  has_many :twitter_status_relations 
end

class TwitterStatusRelation
 belongs_to :member
 belongs_to :twitter_status
end

以下是我执行的查询：

 result = TwitterStatusRelation.all(:joins => :twitter_status, 
:conditions=>{:twitter_statuses=>{:sent_at=>1.month.ago..DateTime.now}}, :include=>:member,:group=>"twitter_status_relations.member_id")

现在，当我第一次在应用程序中运行时，它运行正常：

print result[0].member, result[0].member.class.reflect_on_all_associations(:has_many)
#=> <Member...>, [<ActiveRecord::Reflection::AssociationReflection,...]

但是，当我再次运行它，并尝试访问该成员的任何关联时，我得到零例外。打印显示以下内容：

print result[0].member, result[0].member.class.reflect_on_all_associations(:has_many)
#=> <Member...>, [-- empty ---]

看起来成员对象没有任何关联，因此当我尝试访问其中任何一个时，我得到一个例外。

您是否知道为什么ActiveRecord在某些情况下不会初始化返回对象的关联？我很感激任何半想法，因为我被卡住了。

Answer 1

以下是上述查询生成的SQL（Ran代表我发布了问题）。 SQL有更多的字段然后查询，因为我在发布时简化了查询，删除了与问题无关的条件。

SELECT `twitter_status_relations`.`id` AS t0_r0,
twitter_status_relations。twitter_status_id AS t0_r1， twitter_status_relations。source_twitter_identity_id AS t0_r2， twitter_status_relations。relation_type AS t0_r3， twitter_status_relations。relation_data AS t0_r4， twitter_status_relations。linked_twitter_identity_id AS t0_r5， twitter_status_relations。user_id AS t0_r6， twitter_status_relations。linked_member_id AS t0_r7，members。id AS t1_r0，members。user_id AS t1_r1，members。name AS t1_r2， members。email AS t1_r3，members。member_rating AS t1_r4， members。created_at AS t1_r5，members。updated_at AS t1_r6， members。merged_with_member_id AS t1_r7，members。engage_rating AS t1_r8，members。support_rating AS t1_r9， members。user_engage_rating AS t1_r10， members。user_support_rating AS t1_r11， members。influence_rating AS t1_r12，members。twitter_username AS t1_r13，members。lead_rating AS t1_r14， members。follow_rating AS t1_r15，members。unfollow_rating AS t1_r16，members。followers_count AS t1_r17，members。hidden AS t1_r18 FROM twitter_status_relations LEFT OUTER JOIN members ON members。id = twitter_status_relations。linked_member_id WHERE （twitter_status_relations。user_id = 1 AND twitter_status_relations。relation_type IN（ '提及'，'回复'，'received_dm'，'转推'，'链接'，'术语'，'＃标签'）和twitter_status_relations。linked_member_id IN（ 83995,128457,21421,138316,128455,97475,128453,436231,82236,441208,138564,138337,436223,436222,441093,21194,441088,441092,438998,442752,138331,138327,138325,444897,9277， 12,509521,13,15,534511,7606,7447,200,7,4,17200,5,652302,1,5536,18770,652301,214082,150870,436228,81204,436225,662513,138608,138338 ））和twitter_status_relations。身份证明（8304,26493,113492,113638， 1,6,41213,113493,20,26173）GROUP BY twitter_status_relations.linked_member_id ORDER BY members.member_rating

ActiveRecord返回具有未初始化关联的模型对象

1 个答案: