Random record from MongoDB

Question

I am looking to get a random record from a huge (100 million record) mongodb.

What is the fastest and most efficient way to do so? The data is already t

Answer 1

My PHP/MongoDB sort/order by RANDOM solution. Hope this helps anyone.

Note: I have numeric ID's within my MongoDB collection that refer to a MySQL database record.

First I create an array with 10 randomly generated numbers

    $randomNumbers = [];
    for($i = 0; $i < 10; $i++){
        $randomNumbers[] = rand(0,1000);
    }

In my aggregation I use the $addField pipeline operator combined with $arrayElemAt and $mod (modulus). The modulus operator will give me a number from 0 - 9 which I then use to pick a number from the array with random generated numbers.

    $aggregate[] = [
        '$addFields' => [
            'random_sort' => [ '$arrayElemAt' => [ $randomNumbers, [ '$mod' => [ '$my_numeric_mysql_id', 10 ] ] ] ],
        ],
    ];

After that you can use the sort Pipeline.

    $aggregate[] = [
        '$sort' => [
            'random_sort' => 1
        ]
    ];