使用哪个？mongo mapper? mongoid? mongomastic?
在一个新项目中使用mongodb, 选择Object mapper的时候，看到官方的推荐，我凌乱了：

Several mappers are available:

MongoMapper from John Nunemaker
Mongoid from Durran Jordan
Mongomatic from Ben Myles
MongoODM from Carlos Paramio
MongoModel from Sam Pohlenz
DriverAPILayer from Alexey Petrushin

搜索了一下，“哪个OM最好？”这样的问题在stackoverflow上被关闭了，不过这个文章非常有帮助：
http://stackoverflow.com/questions/1958365/mongoid-or-mongomapper

问：mongoid 还是用mongomapper

17票， Aynat答：
I have used MongoMapper for awhile but decided to migrate to MongoId. The reason is hidden issues plus arrogance towards users. I had to jump through hoops to make MongoMapper work with Cucumber (succeeded in the end) and to put a couple of patches even the project was simple, but it's not the point. When I tried to submit a bug fix (due to incompatibility with ActiveRecord), they seemingly got pissed off that I found a problem and I was pushed around. While I was testing, I also encountered a major bug with their query implementation, while their testing was tuned in a way that the tests pass. After my previous experience, didn't dare to submit it.


我用MongoMapper已经有一段日子了，不过最近决定要换成MongId。 mongomapper的人太自大，她们有BUG（比如不能跟cucumber兼容）也不愿意改，我提了PATCH他们反而觉得很愤怒，估计他们自我感觉太好，自认为产品美文体。而且mongomapper的查询接口太差劲。我还得做一些修改才能让代码工作。我不介意修改代码，但是由于之前的不好的经验，这次我不敢提PATCH了。。。 而且， mongoid的社区（提交代码的人啊啥的）比mongomapper的强太多了。

5票， mtkd答：
Did some testing with MongoMapper last week, it was stable but I found the query interface a little limited (also some of the AR logic was quirky), switched to Mongoid today and it feels much better to use - and more intuitive if you are used to AR.

上周对MongoMapper做了些测试，它确实稳定，但是查询接口还是不太理想（而且有的active record的逻辑也很奇怪）， 今天我换到了mongid上，用起来舒服多了。而且对于熟悉AR的朋友也很直观。

30票，Nader答：
(2010年一月答案）i've been using both for the past couple weeks. Mongomapper has better support for relational associations (non-embedded) and has greater third-party support. Mongoid has better query support, much better documentation (MM has close to none, though a website is supposedly in the works), Rail 3 support (and thus Devise support) and a slightly more active community on Google Groups.

I ended up going with Mongoid.

这两个我都用了几周。Mongomapper对于关联支持的很好，而且被很多第三方工具支持。 Mongoid的查询接口做的更好，而且文档也强多了（MongoMapper的文档都关掉了(?)）。Mongoid还支持RAILS3，它的论坛也更活跃。

(2011年一月追加答案）
Since I originally wrote this answer Mongoid has picked up lots of third-party support and the difference in the communities is even greater. In my opinion Mongoid is more of a clear choice today. Performance should be relatively the same as they both go through the Ruby driver. Though you need to be careful with OM not to construct horrendous documents. Nader Feb 1 '11 at 0:53

过去一年里，MongoID 被更多的第三方工具支持，所以它们的差距是越来越大了。在我看来，现在Mongid更好了。我们应该毫不犹豫的选择它。 它们在性能上估计差距不大，因为用的都是RUBY的驱动。

其他几个答案也很吸引我，可惜被关掉了：
Which Rails Object Mapper to choose for MongoDB? [closed]

从这个文章（http://praktikanten.brueckenschlaeger.org/2010/11/23/do-i-use-mongoid-mongomapper-or-mongomatic-as-my-ruby-orm-for-mongodb） 中 有 三者的对比（mongoid, mongomapper, mongomatic). 其中对于mongomatic的说法是：简单：

mongoid:

better support for embedded documents
better support for very large documents (>500kb)
closer to activerecord, by making use of active model and an arel like query syntax
very nice and lean documentation to be found on the project website..
( 对embedded documents支持的更好
对大数据量的documents支持的更好（ 》 500 KB）
更activerecord非常类似。使用了arel查询。
简明扼要的教程，非常棒。)

mongomapper:

better support for reference associations
supposedly it has a bigger community, or at least still had a bigger community last summer
better plugin interface
(对关联支持的更好， 社区很大（起码在写文章的时候，2010年夏天）， 对PLUGIN支持的更好）

mongomatic

supposedly it’s faster. there is a benchmark posted on some blog. The benchmark itself can be downloaded on Github
it says it focusses on simplicity

（据说是最快的，官方文档说，它注重的是使用简单）

更多的文章都是2010年的了。。。呃。。。有点儿老旧，我还是用mongoid的（忙高一的）