CODEWITHSUNDEEP
javascriptarraysmongodbsorting
user2402616
user2402616

Reputation: 1563

MongoDB Sort certain Documents to top first

Let's say I have the following collection

Collection = [
    {name: 'Ann'},
    {name: 'Bob'},
    {name: 'Cecil'},
    {name: 'KEY: John'},
    {name: 'KEY: Cecil'},
    {name: 'Susan'},
    {name: 'Zack'}
];

Is there any way to use sort in MongoDB so that I can have all Documents that have their name field start with KEY: get returned first? And then I'd like the rest of the Collection to be sorted how it currently is.

I.e

Collection = [
        {name: 'KEY: John'},
        {name: 'KEY: Cecil'},
        {name: 'Ann'},
        {name: 'Bob'},
        {name: 'Cecil'},
        {name: 'Susan'},
        {name: 'Zack'}
    ];

From what I've read there's no way to do a custom sort in MongoDB. If not, is there a simple way to do this in JS using underscore or some other library. I'd prefer that than the accepted answer here Sort an array to have specific items first in the array where another array(s) has to be built.

Any ideas?

Upvotes: 2

Views: 734

Answers (1)

mickl
mickl

Reputation: 49975

You can use $addFields to evaluate new field your collection will be sorted by. The $indexOfBytes operator can be used to determine if string starts with KEY:

db.collection.aggregate([
    {
        $addFields: {
            startsWithKey: { $eq: [ { $indexOfBytes: [ "$name", "KEY", 0 ] } ]}
        }
    },
    {
        $sort: {
            startsWithKey: -1
        }
    }
])

Mongo Playground

Upvotes: 3

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