Q1. I am assuming that this piece of code, is the code we are talking about, and the question is asking about whether a $facet with a $facet is valid?
facet_3: [
{
$facet: {
facet_3_1: [{ bucketAuto: { groupBy: "_id", buckets: 2 } }]
}
}
]
Or have I read the question wrong.
Q2. a $multiply expression takes a document as input, not an array.
Ahhhh - It’s not talking about the arguments, it’s talking about the manner in which the arguments are passed to the $multiply.