我面临着共同的问题.我的Rails应用程序在我的本地机器上工作,但是在部署到heroku之后它崩溃了：
<% unless @user.hotels.empty? %>
<% @user.hotels.each do |hotel| %>
<%= "#{hotel.description} #{hotel.name} in #{hotel.city},#{hotel.country}" %><br />
<% end %>
<% end %>
这是从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？创建错误.我知道,sqlite是相当原谅,但Postgresql不是.这是酒店型号的外键：user_id：integer
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 }
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
....