#explain command
pp db[:zips].find(:state => 'MD').explain
#List all indexes: db[:zips].indexes.each do |index|
p index #drop_one
db[:zips].indexes.drop_one('state_1')
#unique command
db[:users].indexes.create_one({ "user_id":1}, {unique: true})
#sparse index
db[:users].indexes.create_one({ "user_id:1}, { sparse: true})
#TTL index
db[:users].indexes.create_one({ "user_id:1}, { expireAfterSeconds: 3600})