Puedes probar debajo de la agregación
Básicamente necesitas $filter
los products
matriz y busque el $cond
ition si no contiene ningún elemento o igual a []
entonces tienes que $slice
con el primer elemento de los products
matriz.
db.collection.aggregate([
{ "$addFields": {
"products": {
"$cond": [
{
"$eq": [
{ "$filter": {
"input": "$products",
"cond": { "$eq": ["$$this.product_id", 2] }
}},
[]
]
},
{ "$slice": ["$products", 1] },
{ "$filter": {
"input": "$products",
"cond": { "$eq": ["$$this.product_id", 2] }
}}
]
}
}}
])
o incluso usando $let
agregación
db.collection.aggregate([
{ "$addFields": {
"products": {
"$let": {
"vars": {
"filt": {
"$filter": {
"input": "$products",
"cond": { "$eq": ["$$this.product_id", 2] }
}
}
},
"in": {
"$cond": [
{ "$eq": ["$$filt", []] },
{ "$slice": ["$products", 1] },
"$$filt"
]
}
}
}
}}
])