Querying MongoDB collection by array intersection - node.js

Question

What I have:
An array of strings that I wish to query with. ['a', 'b', 'c']
Data I'm querying against:
A collection of objects of type foo, all with a bar field. The bar field is an array of strings, the same type as the one I'm querying with, potentially with some of the same elements.
foo1 = { bar: ['a'] }
foo2 = { bar: ['d'] }
foo3 = { bar: ['a', 'c']}
What I need:
A query that returns all foo objects whose entire bar array is contained within the query array. In the example above, I'd want foo1 and foo3 to come back

Answer 1

using aggregation
you might need to use $setIsSubset in aggregate pipeline
db.col.aggregate(
[
{$project : { bar : 1 , isSubset: { $setIsSubset : [ "$bar" , ['a','b','c'] ] }}},
{$match : { isSubset : true}}
]
)
collection
> db.col.find()
{ "_id" : ObjectId("5a6420d984eeec7b0b2f767b"), "bar" : [ "a" ] }
{ "_id" : ObjectId("5a6420d984eeec7b0b2f767c"), "bar" : [ "a", "c" ] }
{ "_id" : ObjectId("5a6420d984eeec7b0b2f767d"), "bar" : [ "d" ] }
aggregate
> db.col.aggregate([{$project : { bar : 1 , isSubset: { $setIsSubset : [ "$bar" , ['a','b','c'] ] }}}, {$match : {isSubset : true}}])
{ "_id" : ObjectId("5a6420d984eeec7b0b2f767b"), "bar" : [ "a" ], "isSubset" : true }
{ "_id" : ObjectId("5a6420d984eeec7b0b2f767c"), "bar" : [ "a", "c" ], "isSubset" : true }
>
EDIT
using find with $expr
db.col.find({$expr : { $setIsSubset : [ "$bar" , ['a','b','c'] ] }})
result
> db.col.find({$expr : { $setIsSubset : [ "$bar" , ['a','b','c'] ] }})
{ "_id" : ObjectId("5a6420d984eeec7b0b2f767b"), "bar" : [ "a" ] }
{ "_id" : ObjectId("5a6420d984eeec7b0b2f767c"), "bar" : [ "a", "c" ] }
>