Postgresql Rails 4 迁移： has_and_belongs_to_many table name

我目前正在try 将rails 3.2应用程序切换到rails 4.0.但我有一个问题是has_and_belongs_many型的.

我创建了一个测试应用程序，我也有同样的问题.这就是我所做的:

创建了两个模型:foo_clip和foo_url

class FooClip < ActiveRecord::Base
  has_and_belongs_to_many :foo_urls

  attr_accessible :id, :name
end


class FooUrl < ActiveRecord::Base
  has_and_belongs_to_many :foo_clips

  attr_accessible :url
end

在此之后，我更新了迁移文件:

class CreateFooClips < ActiveRecord::Migration
  def change
    create_table :foo_clips do |t|
      t.string :name
      t.timestamps
    end
  end
end

class CreateFooUrls < ActiveRecord::Migration
  def change
    create_table :foo_urls do |t|
      t.string :url
      t.timestamps
    end
  end
end

现在，我已经为has_和_beans_to _many表创建了迁移文件

class CreateFooClipsFooUrls < ActiveRecord::Migration
  def change
    create_table :foo_clips_foo_urls do |t|
      t.belongs_to :foo_url
      t.belongs_to :foo_clip
    end
  end
end

作为最后一步，我创建了一个用于测试的种子文件:

foourl1 = FooUrl.create!(:url => 'http://www.google.com')
foourl2 = FooUrl.create!(:url => 'http://www.apple.com')

fooclip1 = FooClip.create!(:name => 'TestClip1')

fooclip1.foo_urls << foourl1
fooclip1.foo_urls << foourl2

fooclip1.save

现在我做到了:

rake db:drop
rake db:create
rake db:migrate
rake db:seed

得到了这个错误:

PG::UndefinedTable: ERROR:  relation "foo_clips_urls" does not exist
LINE 5:         WHERE a.attrelid = '"foo_clips_urls"'::regcla...
                                          ^
:               SELECT a.attname, format_type(a.atttypid, a.atttypmod),
               pg_get_expr(d.adbin, d.adrelid), a.attnotnull, a.atttypid, a.atttypmod
                FROM pg_attribute a LEFT JOIN pg_attrdef d
                  ON a.attrelid = d.adrelid AND a.attnum = d.adnum
               WHERE a.attrelid = '"foo_clips_urls"'::regclass
                 AND a.attnum > 0 AND NOT a.attisdropped
               ORDER BY a.attnum

如果我看一下postgres数据库，这个表叫做:foo_clips_foo_url

知道为什么会这样吗？