Fix truncation on MongoDB 3

[andreale]

As reported on the mongoDB documentation, the collection system.namespaces is deprecated and can no longer be used to list the database collections.

This PR addresses the deprecation issue by using the command listCollections instead. This allow DatabaseCleaner to work with MongoDB 3 with WiredTiger storage engine.

[zjx20]

Thanks! This really helps a whole lot!

[bejmuller]

+1

[FlammenB]

👍

[lifegiver]

🆗

[simonmorley]

+1

[saschaknobloch]

This regexp isn't matching system.<something> collections. It should be collection_name =~ /.?system\.|\$/

For MongoDB 3.x.x using Wired Tiger storage engine this PR is sufficient, because by default there are no .system. collections. But if using MongoDB 3.x.x with MMapV1 storage engine, it will fail, because there still is the system.indexes collection.

[andreale]

Hi @saschaknobloch, thanks for your feedback.

I just reused the (already present) regexp that filters out any xxxxxx.system.indexes and xxxxxx.yyyyyy.$_id_ collection. This should make my change also compatible with MMAPv1 collections (by excluding those collections form the truncation).

Could you please clarify better the issue?

[saschaknobloch]

Hey @andreale,

here is a link to rubular with the regexp provided with this code, check out yourself:

http://rubular.com/r/qpc2cGb38J

[saschaknobloch]

BTW: the command listCollections allows also for setting a filter

http://docs.mongodb.org/manual/reference/command/listCollections/#dbcmd.listCollections

This gives us the chance to solve this problem more elegant (but still the regex provided with this PR doesn't work for me ;) ):

session.command(listCollections: 1, filter: {"name"=> {"$not"=>/.?system\.|\$/}})['cursor']['firstBatch'].map do |collection| 
...
end 

[andreale]

Thanks @saschaknobloch.

I could reproduce the issue on another dev machine (where we also get a <database_name.$cmd collection) and confirm your updated regexp is working. I'm updating my PR, with also the filter at mongo-level.

• Ale

[lucke84]

+1

[dot]

+1

[saschaknobloch]

Since there is no progress on supporting MongoDB 3, we've released our own implementation:

https://github.com/td-berlin/mongoid_cleaner

We've added drop strategy, which improves the performance (compared to truncation strategy) by factor 3-5 for our projects.

It only supports Mongoid and MongoDB 3. It's tested with:

• Ruby 2.1
• Ruby 2.2
• JRuby
• Ruby-Head

Each against WiredTiger and MMAPv1.

Feel free to use and contribute.

[etagwerker]

@andreale Thank you!