看Perl代码严重上自尊了。为了抚慰下受伤的心灵， 就来学习下Python & MongoDB. 

1. MongoDB does not support joins.

2. MongoDB does not support transactions. It does have some support for atomicoperations, however.

3. MongoDB schemas are flexible. Not all documents in a collection must adhere to the same schema.

4.  MongoDB is a document-oriented database.

5. The comparison between mongodb and the usual sql.

暂时先写到这里，现在回去继续看Perl还有Dancer。