Mongodb aggregation, Use value from a variable in the expression of $group _id

Question

I am trying to groups documents by two fields, field1 and field2.

myCollection.aggregate([{ $group: { _id: { group1: "$field1", group2: "$field2" }, count: { $sum: 1 } } }])

Which works fine producing the expected results.

But I want to re run the above in a loop, each run will have different $field2, so the following is failing, how can I it be done? Thanks

const field3 = 'someValue'; // <<--- will change in every loop run --- myCollection.aggregate([{ $group: { _id: { group1: "$field1", group2: "$$field3" //<<---------------- }, count: { $sum: 1 } } }])

DAXaholic · Accepted Answer · 2016-09-28 07:42:50Z

The following should work for you

var field3 = 'someValue'; myCollection.aggregate([{ $group: { _id: { group1: "$field1", group2: "$" + field3, }, count: { $sum: 1 } } }])

Collectives™ on Stack Overflow

Mongodb aggregation, Use value from a variable in the expression of $group _id

1 Answer 1

Comments

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Related