问题
I have recently moved to MongoDB part of the back-end of a web app, the web app itself is a validation tool, and the workflow looks like:
- the user uploads a file (typically hundreds of thousands of lines)
- the validator checks it outputting a lot of messages (possibly more than one per line)
- ...and finally provide a few statistics
I modelled my application so that each user has it's own DB containing:
- The file (saved through GridFS)
- A collection containing the messages (possibly over a million lines, in some cases)
- A collection with the statistics
We have a few hundreds of users, so MongoDB will end up having a few hundreds DBs.
Of course I could have hold all the data in the same DB, using namespaces to separate data from different users. However I felt it was handy to send the DB in the connection URI, and I found more intuitive to issue a "drop database" statement to purge a user, rather than searching and removing its data in the large DB.
I am pretty new to MongoDB, so my question is: is there any drawback in having several DBs in the same MongoDB instance? Or is there any special consideration that I should give to the problem?
回答1:
I'm not familiar with MongoDB specifically. In general, openning a connection to a database is a relatively slow operation and ties up system resources. Whether this is enough to matter in your case I can't say.
Having a different db for each user would make it difficult to perform queries that access data for multiple users. Maybe you have no need to do this.
Still, I would think it would be a whole lot simpler in general to just put a user id in each record rather than create a separate database. What's the gain of separate databases? Okay, deleting a user means saying "drop database". But deleting a user from a single database should mean saying "delete from tableX where user=?; delete from tableY where user=?" etc for however many relevant tables you have. I can't imagine it's hundreds, right? Maybe half a dozen lines of code or so?
来源：https://stackoverflow.com/questions/15221236/mongodb-data-modelling-any-drawbacks-in-using-lots-of-databases