How can I group boolean fields in mongodb? - mongodb

Question

Here's a very simple data example.
[
{
"aaa": true,
"bbb": 111,
},
{
"aaa": false,
"bbb": 111,
}
]
Then, what query should be executed so that I can get the result like this?
[
{
"_id": "0",
"bbb_sum": 222,
"aaa_and": false,
"aaa_or": true
}
]
Actually, I've tried with a query like this
db.collection.aggregate([
{
"$group": {
"_id": "0",
"bbb_sum": {
"$sum": "$bbb"
},
"aaa_and": {
"$and": ["$aaa", true]
},
"aaa_or": {
"$or": ["$aaa", false]
}
}
}
])
But the Mongo Playground complains query failed: (Location40237) The $and accumulator is a unary operator, that's quite confusing.
You can also find this simple test case here https://mongoplayground.net/p/8dqtXJ93vIx
Also, I've searched for similar questions on both Google and Stackoverflow, but I can't find one.
Thanks in advance!

Answer 1

Not like "$sum","$and" and "$or" are not aggregation operators that can be used in "$group". You can temporary save all the "aaa" field into an array and then use "$project" operator to process the data.
db.collection.aggregate([
{
"$group": {
"_id": "0",
"sum": {
"$sum": "$bbb"
},
"aaa_all": {
"$push": "$aaa"
}
}
},
{
"$project": {
"sum": 1,
"aaa_and": {
"$allElementsTrue": "$aaa_all"
},
"aaa_or": {
"$anyElementTrue": "$aaa_all"
}
}
}
])
Here is the case: https://mongoplayground.net/p/Y-Fs_Ch9lwk

Answer 2

$min and $max operators actually work with booleans too, false being considered smaller than true
thinking of them as 0 and 1 might be easier to understand :
$min: [a,…,n] will return 1/true only if all elements are 1/true => this is a AND
$max: [a,…,n] will return 0/false only if all elements are 0/false => this is a OR
(the operators will return booleans if input booleans, the analogy with numbers is only for the sake of comprehension)
So your request can simply become :
db.collection.aggregate([
{
"$group": {
"_id": "0",
"bbb_sum": {
"$sum": "$bbb"
},
"aaa_and": {
"$min": "$aaa"
},
"aaa_or": {
"$max": "$aaa"
}
}
}
])

Answer 3

You can do some logics as below
db.collection.aggregate([
{
"$group": {//Group by desired id
"_id": null,
"sum": {//Sum the value
"$sum": "$bbb"
},
"aaa_and": {
"$sum": {
"$cond": {
"if": {
"$eq": [
"$aaa",
true
]
},
"then": 1, //If true returns 1
"else": 0 // else 0
}
}
},
"total": { //helper to do the logic
$sum: 1
}
}
},
{
$project: {
aaa_and: {
"$eq": [//If total matches with number of true, all are true
"$total",
"$aaa_and"
]
},
aaa_or: {
"$ne": [//if value greater than 0, then there is at least one true
"$aaa_and",
"0"
]
},
sum: 1
}
}
])
playground