Sql 它本身（间接地）查询了花名册\成员\姓名。我将该行更改为直接查询花名册信息，如下所示：m.花名册信息.成员名称。再次感谢你的努力！尽管如此，我还是奖励了你，因为你的建议让我更深入地挖掘，并最终确定了问题和解决方案。再次感谢！ subscribers = [

---

它本身（间接地）查询了

花名册\成员\姓名
。我将该行更改为直接查询
花名册信息
，如下所示：
m.花名册信息.成员名称
。再次感谢你的努力！尽管如此，我还是奖励了你，因为你的建议让我更深入地挖掘，并最终确定了问题和解决方案。再次感谢！
subscribers = []
mailgroup.mailgroup_members.opted_to_receive_email.includes(:roster_contact, :roster_info).each { |m|
  subscribers << { :EmailAddress => m.roster_contact.member_email,
                   :Name => m.roster_contact.member_name,
                   :CustomFields => [ { :Key => 'gender', 
                                        :Value => m.roster_info.gender.present? ? m.roster_info.gender : 'X' 
                                    } ] 
                  } if m.roster_contact.member_email.present?
}
subscribers

SELECT `ROSTER_INFO`.* FROM `ROSTER_INFO` WHERE `ROSTER_INFO`.`ID` IN ('1450', '1000', '1111')

RosterInfo Load (84.8ms)  SELECT `ROSTER_INFO`.* FROM `ROSTER_INFO` WHERE `ROSTER_INFO`.`ID` = '1450' LIMIT 1
RosterInfo Load (59.2ms)  SELECT `ROSTER_INFO`.* FROM `ROSTER_INFO` WHERE `ROSTER_INFO`.`ID` = '1000' LIMIT 1
RosterInfo Load (56.8ms)  SELECT `ROSTER_INFO`.* FROM `ROSTER_INFO` WHERE `ROSTER_INFO`.`ID` = '1111' LIMIT 1

class RosterInfo < ActiveRecord::Base
  self.primary_key = 'ID'
end

class RosterContact < ActiveRecord::Base
  self.primary_key = 'ID'

  has_many :mailgroup_members, foreign_key: 'rosterID'
  has_many :mailgroups, through: :mailgroup_members

  has_one :roster_info, foreign_key: 'ID'     # can use this line
  #belongs_to :roster_info, foreign_key: 'ID' # or this with no difference

  def member_name                             # I added this method to this
    roster_info.member_name                   # question only *after* having
  end                                         # figured out the problem.
end

class RosterWeb < ActiveRecord::Base
  self.primary_key = 'ID'
end

class Mailgroup < ActiveRecord::Base
  self.primary_key = 'ID'

  has_many :mailgroup_members, foreign_key: 'mailCatID'

  has_one :mailing_list, foreign_key: :legacy_id
end

class MailgroupMember < ActiveRecord::Base
  self.primary_key = 'ID'

  belongs_to :mailgroup, foreign_key: 'mailCatID'
  belongs_to :roster_contact, foreign_key: 'rosterID'
  belongs_to :roster_info, foreign_key: 'rosterID'
  belongs_to :roster_web, foreign_key: 'rosterID'

  scope :opted_to_receive_email, joins(:roster_web).where('ROSTER_WEB.receiveEmail=?', 1)
end

class RosterInfo < ActiveRecord::Base
  has_one :roster_contact, foreign_key: 'ID'  
end

class RosterContact < ActiveRecord::Base
  has_one :roster_info, foreign_key: 'ID' 
end

:Name => m.roster_contact.member_name,

:Name => m.roster_info.member_name,