I have a users collection with the following structure:
[
{
name: "xxx",
labels: [
{
category: "Language",
values: ["English", "Spanish"],
},
{
category: "Hobby",
values: ["Read", "Cook", "Read"],
},
]
},
{
name: "yyy",
labels: [
{
category: "Language",
values: ["English", "English"],
},
{
category: "Hobby",
values: ["Read", "Play", "Play"],
},
]
},
]
I want to delete all duplicates from values array, so the result would be:
[
{
name: "xxx",
labels: [
{
category: "Language",
values: ["English", "Spanish"],
},
{
category: "Hobby",
values: ["Read", "Cook"],
},
]
},
{
name: "yyy",
labels: [
{
category: "Language",
values: ["English"],
},
{
category: "Hobby",
values: ["Read", "Play"],
},
]
},
]
I tried to use setUnion and setIntersection, but I didn't know what is the right why to use them with a nested array.
For Mongo version 4.2+ you can use pipeline updates for this, like so:
db.collection.updateMany(
{},
[
{
"$set": {
labels: {
$map: {
input: "$labels",
in: {
$mergeObjects: [
"$$this",
{
values: {
$setUnion: "$$this.values"
}
}
]
}
}
}
}
}
])
For older Mongo versions you'll have to read each document into memory and do this in code, then update each document separately.