PHP - MonogoDB - Remove duplicates

removeDuplicates.php

<?php

/**
 * This example assumes:
 *    _id:    entry unique key
 *    field:  a field that is not unique, but you want to remove all
 *            entries that have the same value while keeping the first entry.
 */

$duplicates = $collection->aggregate([
    [
        '$group' => [
            '_id' => [ 'field' => '$field' ],
            'dups' => [ '$addToSet' => '$_id' ],
            'count' => [ '$sum' => 1 ]
        ]
    ],
    [
        '$match' => [
            'count' => [ '$gt' => 1 ]
        ]
    ]
]);

foreach ($duplicates as $duplicate) {
    unset($duplicate->dups[0]);
    $collection->deleteMany([
        '_id' => [ '$in' => $duplicate->dups ]
    ]);
}