Suggested minor statement change for setting _id about em-mongo

[bcg]

I think ruby-mongo-driver only supports '_id' as the key.

[adriaant]

It handles both. See https://github.com/mongodb/mongo-ruby-driver/blob/master/lib/mongo/collection.rb, statement:
if doc.has_key?(:_id) || doc.has_key?('_id')

[adriaant]

Thanks for the latest changes to em-mongo, it fixes my issue!

[bcg]

No problem. It appears ruby-mongo-driver returns '_id' from find() but creates a :_id when you do an insert(). Not thrilled with the semantics, but better to follow along than to pick a whole new path I suppose. BSON doesn't support symbols at all, so I kind of wish it was an either or proposition in the drivers (all Symbols become Strings or all Strings become Symbols). I may add the option in the future ...

[adriaant]

Yes, it's messy when there are both symbol and string keys without a proper guideline. I personally prefer symbol keys as they're cheaper than strings, but so far there's little consistency among gems.