For background, I have to create a field in a collection, but ONLY if another known field (an array) is not empty. I'm trying to make a boolean filter with the $and and some conditions:
$set: {
clientsAllowed: {
$cond: {
if: {
$and: [
{
businessAllowed: { $exists: true },
},
{
businessAllowed: { $type: "array" },
},
{
businessAllowed: { $ne: [] },
},
],
},
then: [...],
else: [...],
},
}
}
But I get this error:
Invalid $set :: caused by :: Unrecognized expression '$exists'
Is the $exists wrongly formatted? Or is the $and stage? Any ideas?
Type cond for businessAllowed is enough. You don't need to check exists or not.
db.collection.aggregate([
{
$set: {
clientsAllowed: {
$cond: {
if: {
$and: [
{
"$eq": [
{
$type: "$businessAllowed"
},
"array"
]
},
{
$ne: [
"$businessAllowed",
[]
]
}
]
},
then: [],
else: []
}
}
}
}
])