I have a collection that I'm performing an aggregation on and I've basically gotten it down to
{array:[1,2,3], value: 1},
{array:[1,2,3], value: 4}
How would I perform an aggregation match to check if the value is in the array? I tried using {$match: {"array: {$in: ["$value"]}}}
but it doesn't find anything.
I would want the output (if using the above as an example) to be:
{array:[1,2,3], value:1}
A slight variation based on @chridam's answer:
db.test.aggregate([
{ "$unwind": "$array" },
{ "$group": {
_id: { "_id": "$_id", "value": "$value" },
array: { $push: "$array" },
mcount: { $sum: {$cond: [{$eq: ["$value","$array"]},1,0]}}
}
},
{ $match: {mcount: {$gt: 0}}},
{ "$project": { "value": "$_id.value", "array": 1, "_id": 0 }}
])
The idea is to $unwind
and $group
back the array, counting in mcount
the number of items matching the value. After that, a simple $match
on mcount > 0
will filter out unwanted documents.