导轨创造schema_migrations - Mysql2 ::错误：指定的键过长 [英] Rails creating schema_migrations - Mysql2::Error: Specified key was too long

问题描述

我用Rails 3.2.6和MySQL 6.0.9（但我有完全在MySQL 5.2.25同样的错误）

I am using Rails 3.2.6 and Mysql 6.0.9 (but I have exactly the same error on MySQL 5.2.25)

当我创建新的数据库（耙分贝：创建），然后当我尝试加载模式（耙模式：负载）我得到这个错误：

When I create new database (rake db:create) and then when I try to load the schema (rake schema:load) I get this error:

Mysql2::Error: Specified key was too long; max key length is 767 bytes: CREATE UNIQUE INDEX `unique_schema_migrations` ON `schema_migrations` (`version`)

在时间和研究时间，我发现这些解决方案：

After hours and hours of research I found these solutions:

这没有奏效。我试了一下我的Linux服务器，我的Mac上，甚至在Windows上 - 这是行不通的。

This didn't work. I tried it on my Linux server, my Mac and even on Windows - it just doesn't work.

我不需要版本列255长（当它是UTF-8，那么就需要4 * 255 = 1020字节，超过了MySQL的限制767字节键）。我并不需要它是UTF-8两种，但在数据库中的所有其他表都是UTF-8。我将utf8_czech_ci是默认排序规则。

I do not need the version column to be 255 long (when it is UTF-8, then it takes 4*255 = 1020 bytes and exceeds the MySQL limit of 767 byte for keys). I do not need it to be UTF-8 either, but all other tables in the DB are UTF-8 and I have set utf8_czech_ci to be the default collation.

这实际创建schema_migrations表的方法是这样的：

The method that actually creates the schema_migrations table looks like this:

def self.create_table
  unless connection.table_exists?(table_name)
    connection.create_table(table_name, :id => false) do |t|
      t.column :version, :string, :null => false
    end
    connection.add_index table_name, :version, :unique => true, :name => index_name
  end
end

您可以读取整个文件<一个href="https://github.com/rails/rails/blob/master/activerecord/lib/active_record/schema_migration.rb">Github导轨/导轨

于是，我就添加：上限=＆GT; 100 到 t.column 语句，但是我没有这个解决方案成功要么。问题是，我不能让这个补丁负荷时originial已经到位。换句话说 - 我的补丁负荷的在的ActiveRecord的:: SchemaMigration所以它是覆盖

So I tried to add :limit => 100 to the t.column statement, but I did not succeed with this solution either. The problem is that I cannot make this patch load when the originial is already in place. In other words - my patch loads before ActiveRecord::SchemaMigration so it is overwritten.

当我把这个配置/初始化/补丁/ schema_migration.rb ：

require 'active_record/scoping/default'
require 'active_record/scoping/named'
require 'active_record/base'

module ActiveRecord
  class SchemaMigration < ActiveRecord::Base
    def self.create_table
      unless connection.table_exists?(table_name)
        connection.create_table(table_name, :id => false) do |t|
          t.column :version, :string, :null => false, :limit => 100
        end
        connection.add_index table_name, :version, :unique => true, :name => index_name
      end
    end
  end
end

据加载成功，但它被覆盖时，原来的ActiveRecord :: SchemaMigration被加载。

It is successfully loaded, but the it is overwritten when the original ActiveRecord::SchemaMigration is loaded.

我试图乱用ActiveSupport.on_load（：active_record）。但是这似乎并没有擦出火花

I tried to mess up with ActiveSupport.on_load(:active_record) but that doesn't seem to work either.

有没有办法来加载originial的ActiveRecord后，这个文件:: SchemaMigration到位，使这个补丁的工作？

你有什么建议吗？我可以澄清任何部分这个问题，如果它是没有意义的你。只是问我。我一直坚持这个太久了。

Do you have any suggestions? I can clarify any part of this question, if it makes no sense to you. Just ask me. I've been stuck with this for too long.

推荐答案

767键应该工作。请确保您使用 UTF8 编码，而不是 UTF16 。 我有同样的问题，我的错误是，我无意中创建 UTF16 数据库

767 key should work. Make sure you use utf8 encoding, and not utf16. I had same problem, and my mistake was that I accidently created utf16 database

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