Given a reference array of strings: ["Comedy", "Horror", "Romance"], I would like to query a Movie model with this schema:
const MovieSchema = new Schema({
_id: {
type: Types.ObjectId,
required: true
},
title: {
type: String,
required: true
},
categories: [{ type: String }],
});
Such that I will get results where I will get Movies with categories in common with the reference array, sorted by the amount of elements it has in common with the reference array. For example:
[
{
_id: "57",
title: "Sample Movie A",
categories: ["Comedy", "Horror", "Romance", "Family"]
},
{
_id: "92",
title: "Sample Movie B",
categories: ["Comedy", "Romance", "Family", "Coming of Age"]
}
]
Note that Movie A is the first in the results because it has 3 items in common with the reference array while Movie B only has 2 items in common.
How can I achieve this query using Mongoose 5.11.16?
You could use $setIntersection to get a count of matching elements, add the resulting array-size as a new field to each document and and then sort by this field.
You could then extend the query to filter matches with a count greater than 0 and remove the categoryCount from the output, e.g.
Movie.aggregate([
{
"$addFields": {
"categoryCount": {
$size: {
$setIntersection: [
[
"Comedy",
"Horror",
"Romance"
],
"$categories"
]
}
}
}
},
{
"$match": {
categoryCount: {
$gt: 0
}
}
},
{
"$sort": {
categoryCount: -1
}
},
{
"$project": {
categoryCount: 0
}
}
])
Example on mongoplayground: https://mongoplayground.net/p/ZlUNfB82FRK
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