PostgreSQL特有的數據庫錯誤： 「的ActiveRecord :: StatementInvalid：PGError：ERROR：運營商不存在」

Question

我的狀態模型看起來是這樣的：

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 

我國模型是這樣的：

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

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

這個工作在SQLite的環境：

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

但在PostgreSQL的環境中，我得到這個：

>> 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) 

有什麼想法？

Answer 1

錯誤消息非常明顯，您試圖在不同類型之間進行比較，因此「字符變化=整數」通知。

解決方案：使country_id成爲'int'類型的列而不是'varchar'。