List MongoDB collections in order of size on disk (for collection and indexes)

gistfile1.sh

DB=your_mongo_database
for coll in `mongo ${DB} --quiet --eval "db.getCollectionNames()" | tr ',' ' '`; do
  echo -n `mongo ${DB} --quiet --eval "db['${coll}'].stats(1024)['size'] + db['${coll}'].stats(1024)['totalIndexSize']"`
  echo ": ${coll}"
done | sort -n -r 

In Mongoid:

Mongoid.default_session.collections.map { |c| s = Mongoid.default_session.command(collstats: c.name); [ c.name, s["size"] + s["totalIndexSize"]] }.sort_by { |n, s| -s }.take(10).each { |n, s| puts "#{n}: #{s}" }; nil

Update for Mongoid:

Mongoid.default_client.collections.map { |c| s = Mongoid.default_client.command(collstats: c.name).documents[0]; [s['ns'], s['size'] + s['totalIndexSize']] }.sort_by { |n, s| -s }.take(10).each { |n, s| puts "#{n}: #{s}" }; nil