postgresql 错误：运算符不存在：字符变化 = 整数
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Error: operator does not exist: character varying = integer
提问by Lukas Hoffmann
I face a common problem. My Rails app works on my local machine, but after deploying to heroku it crashes:
我面临一个常见的问题。我的 Rails 应用程序在我的本地机器上运行，但在部署到 heroku 后它崩溃了：
<% unless @user.hotels.empty? %>
<% @user.hotels.each do |hotel| %>
<%= "#{hotel.description} #{hotel.name} in #{hotel.city}, #{hotel.country}" %><br />
<% end %>
<% end %>
This is from the heroku logs:
这是来自heroku日志：
ActionView::Template::Error (PGError: ERROR: operator does not exist: character varying = integer
LINE 1: SELECT "hotels".* FROM "hotels" WHERE ("hotels".user_id = 1)
^
HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts.
: SELECT "hotels".* FROM "hotels" WHERE ("hotels".user_id = 1)):
@user.hotels.empty?creates the error. I know, sqlite is pretty forgiving, but PostgreSQL is not. This is the foreign key in the hotel model: user_id :integer
@user.hotels.empty?创建错误。我知道，sqlite 非常宽容，但 PostgreSQL 不是。这是酒店模型中的外键：user_id :integer
Heroku says:
Heroku 说：
Make sure the operator is adequate for the data type. ActiveRecord does this automatically when you use an interpolated condition form.
Array conditions:
:conditions => ['column1 = ? AND column2 = ?', value1, value2]
Hash conditions:
:conditions => { :column1 => value1, :column2 => value2 }
The migration looks like following:
迁移如下所示：
class CreateHotels < ActiveRecord::Migration
def self.up
create_table :hotels do |t|
t.string :name
t.string :vanity_url
t.integer :user_id
....
回答by iwasrobbed
This typically happens when the foreign key in the database is not an integer.
这通常发生在数据库中的外键不是整数时。
For example:
例如：
LINE 1: SELECT "hotels".* FROM "hotels" WHERE ("hotels".user_id = 1)
^
In this case, PostgreSQL expects user_idto be an integer, but it almost looks like it's telling you that it was actually a varchar.
在这种情况下，PostgreSQL 期望user_id是一个整数，但它看起来几乎是在告诉您它实际上是一个 varchar。
I would try removing the column and adding it again.
我会尝试删除该列并再次添加它。
