Getting a list of unique embedded/nested objects in a MongoDB document

Question

Consider the following MongoDB \"recipes\" collection:

{
  \"title\" : \"Macaroni and Cheese\",
  \"ingredients\" : [
    { \"name\" : \"noodles\", \"qty\" :         


        

Answer 1

The following query would give you the bare list minus any duplicates:

db.recipes.aggregate([{$unwind:"$ingredients"},{$group:{_id:"$ingredients.name"}}])

More work would be necessary to add the quantities. It would be easier if the unit for the quantities was specified separately.