Query Array to Contain "only" Elements within a Range - mongodb

Question

Suppose I have the following documents.
{ "_id" : 1, "score" : [ -1, 3 ] }
{ "_id" : 2, "score" : [ 1, 5 ] }
{ "_id" : 3, "score" : [ 5, 5 ] }
{"_id" : 4, "score" : [ 2, 1, 5 ]}
If I want to find documents with all elements in score array are between 3 and 6 inclusive, how can I create a query with {$gte:3} and {$lte:6} ?
So, it should return only:
{ "_id" : 3, "score" : [ 5, 5 ] }

Answer 1

The general case here is that you probably "should" generate the "range" that falls in between and then test that the array does NOT contain any of those possible numbers:
var start = 3,
end = 6;
var range = Array(end - start + 1).fill(1).map(e => start++);
db.scores.find({
"score": {
"$elemMatch": { "$gte": start, "$lte": end },
"$not": {
"$elemMatch": { "$nin": range }
}
}
})
Would return:
{ "_id" : 3, "score" : [ 5, 5 ] }
Since that is the only element which contains something that falls within that range "only".
IF you have a restriction where the items have too many possible values to list the entire "range", then you either use a $not on the "range condition":
db.scores.find({
"score": {
"$elemMatch": { "$gte": 3, "$lte": 6 },
"$not": {
"$elemMatch": {
"$not": { "$gte": 3, "$lte": 6 }
}
}
}
})
Or alternately process with an additional calculated condition,
Either using $expr:
db.scores.find({
"score": { "$elemMatch": { "$gte": 3, "$lte": 6 } },
"$expr": {
"$allElementsTrue": {
"$map": {
"input": "$score",
"in": {
"$and": [
{ "$gte": [ "$$this", 3 ] },
{ "$lte": [ "$$this", 6 ] }
]
}
}
}
}
})
Or $redact prior to MongoDB 3.6
db.scores.aggregate([
{ "$match": { "score": { "$elemMatch": { "$gte": 3, "$lte": 6 } } } },
{ "$redact": {
"$cond": {
"if": {
"$allElementsTrue": {
"$map": {
"input": "$score",
"in": {
"$and": [
{ "$gte": [ "$$this", 3 ] },
{ "$lte": [ "$$this", 6 ] }
]
}
}
}
},
"then": "$$KEEP",
"else": "$$PRUNE"
}
}}
])
Or even $where using a JavaScript condition for matching where your MongoDB does not support any of the above:
db.scores.find({
"score": { "$elemMatch": { "$gte": 3, "$lte": 6 } },
"$where": function() {
return this.score.every(e => e >= 3 && e <= 6)
}
})
In all cases you actually want that "positive" condition on the $elemMatch in order to find those elements "within the range" by ideally searching the index on that field. None of the other methods either employing the $not and $nin or via the $allElementsTrue aggregation condition or the Array.every() can actually look at the "index" in order to satisfy the condition. They are merely used in all cases as the "additional filter" from which to "rule out" any "potential" matched documents via the "range" from the eventual results.