Hi!
How can I get the accumulated value of one param? I mean I have a query that get documents from two collections. All documents have a parameter quantity and price. Some add quantity and others rest quantity. I have ordered them by date and I’d like to have a new parameter, say accumSoFar, that is the accumulated value of the quantity. Example:
I’m working with node.js. And although my version of mongodb is 4.0.1, which should support $setWindowFields when I try this approach it just fires an error like: unrecognized name $setWindowFields
const arr = [
{
sign: '+',
quantity: 3
},
{
sign: '+',
quantity: 5
},
{
sign: '2',
quantity: 2
}
]
An the end product should be
const arr = [
{
sign: '+',
quantity: 3,
accumSoFar: 3
},
{
sign: '+',
quantity: 5,
accumSoFar: 8
},
{
sign: '-',
quantity: 2,
accumSoFar: 6
}
]```