Size dont work with aggregation
Mongodb 4.2.8
db.Col.aggregate( [
{ $match: { "Symbol" : "x" }},
{ $group: { _id: "$GroupTime", total: { $size: "$MyArray" } } }
])
return error
“errmsg” : “unknown group operator ‘$size’”,
“code” : 15952,
Size dont work with aggregation
Mongodb 4.2.8
db.Col.aggregate( [
{ $match: { "Symbol" : "x" }},
{ $group: { _id: "$GroupTime", total: { $size: "$MyArray" } } }
])
return error
“errmsg” : “unknown group operator ‘$size’”,
“code” : 15952,
It is not a group operator. These are the group operators: Accumulators $group. But, you can use the $size
in a $project
(or $addFields
) stage.
What is it you are trying to do?
how will be look like query with $addFields ?
In general, you use the $size
operator with a field MyArray
in a document: { _id: 1, MyArray: [ "apples", "bananas", "oranges" ] }
The size of the array can be determined as follows:
{ $addFields: { arraySize: { $size: "$MyArray" } } }
This will get the output as: arraySize: 3