MongoDB find document with most matched elements when using $in operator

Question

So, I have the next schema, it's an index of car parts that is used to automatically find the part types according to the keywords.

nameEnglish: {
  type: String
},
keywords: [{
  type: String
}]

I have two documents on the database, one is:

[
  { _id: 1, nameEnglish: 'abcdef', keywords: ['a', 'b', 'c', 'd', 'e', 'f'] },
  { _id: 2, nameEnglish: 'cde', keywords: ['c', 'd', 'e'] }
]

What I am want to do now is query this collection with the MOST number of matched keywords.

myArr = ['b', 'c', 'f'];
db.collection.find({ keywords: { $in: myArr } });

I want this to always return the first document, since it has 3 matched keywords, and the second has only one. How can I achieve this?

s7vr · Accepted Answer · 2018-01-24 06:22:00Z

1

You can try below aggregation using $setIntersection to find the matching elements between keywords array and input array followed by $size to count the matching elements and $sort descending and $limit 1 to output the most matched document.

You can drop the count field using project exclusion {$project:{count:0}} as final stage.

db.col.aggregate(
    [{
        $addFields: {
            "count": {
                $size: {
                    $setIntersection: ["$keywords", myArr]
                }
            }
        }
    }, {
        $sort: {
            "count": -1
        }
    }, {
        $limit: 1
    }]
)

answered Jan 24, 2018 at 6:22

s7vr

76.2k12 gold badges118 silver badges135 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Saravana · Accepted Answer · 2018-01-24 06:21:22Z

1

You need to use aggregation with $setIntersection to get the number of matches, and sort by the no of matches, limit to expected number of results.

db.col.aggregate([
{$addFields : {noOfMatch :{$size :{$setIntersection : ["$keywords", ['b', 'c', 'f']]}}}},
{$sort : {"noOfMatch" : -1}},
{$limit : 1}
])

answered Jan 24, 2018 at 6:21

Saravana

12.8k2 gold badges42 silver badges60 bronze badges

Collectives™ on Stack Overflow

MongoDB find document with most matched elements when using $in operator

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related