Postgresql特定的数据库错误：“ActiveRecord :: StatementInvalid：PGError：ERROR：运算符不存在”

Question

我的州模型看起来像这样：

class State < ActiveRecord::Base
  belongs_to :country
  named_scope :order_by_name, :order => :name

  validates_presence_of [:country, :name]

  def <=>(other)
    name <=> other.name
  end

end

我的国家模型看起来像这样：

class Country < ActiveRecord::Base
  has_many :states
  named_scope :order_by_name, :order => :name  

  def <=>(other)
    name <=> other.name
  end
end

这适用于SQLite环境：

>> Country.find_by_iso("US").states
=> [#<State id: 1, name: "Alaska", abbr: "AK",  #  .....

但是在postgresql环境中，我得到了这个：

>> Country.find_by_iso("US").states
ActiveRecord::StatementInvalid: PGError: ERROR:  operator does not exist: character varying = integer
LINE 1: SELECT * FROM "states" WHERE ("states".country_id = 214) 
                                                          ^
HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
: SELECT * FROM "states" WHERE ("states".country_id = 214) 

有什么想法吗？

Answer 1

错误信息非常清楚，您正在尝试对不同类型进行比较，因此“字符变化=整数”通知。

解决方案：使country_id成为'int'类型的列而不是'varchar'。