How to implement a cascade delete in MongoDB

mongo_cascade_delete.js

// equivalent of cascade delete in MongoDB

/**
 * Let's assume you have 2 related collections with next data structure.
 *
 * - `archive`
 * {
 *     "_id" : ObjectId("5ce5138efe985e8424a79304"),
 *     "type" : "text",
 *     "headline" : "Curabitur non nulla sit amet nisl tempus convallis quis ac lectus."
 * }
 * - `archive_history`
 * {
 *     "_id" : ObjectId("5ce51d46fe985e8438b7b8ed"),
 *     "item_id" : ObjectId("5ce5138efe985e8424a79304"),
 *     "action" : "fetch"
 * }
 *
 * and you want to delete items from `archive` with some condition and also delete related records in `archive_history`.
 * NOTE: limit is used in case of big amount of data..
 * NOTE: if mongo 3.6+, aggregation with `project`, `filter` might be used to avoid using `map`
 **/

var filterCondition = {type: "text"};
var itemsCount = db.getCollection('archive').find(filterCondition).count()
var processed = 0;
var limit = 100;

print('Have ', itemsCount, ' items to delete.')

while (processed < itemsCount) {
    // get `archive` IDs to delete
    var itemsIDList = db.getCollection('archive')
        .find(filterCondition, {_id: 1})
        .limit(limit)
        .map(function (item) {
            return item['_id']
        });
    print('Got ', itemsIDList.length, ' items IDs to delete.')

    // delete related entries in `archive_history`
    db.getCollection('archive_history')
        .deleteMany(
            {
                item_id: {
                    $in: itemsIDList
                }
            }
        )
    print('Deleted related entries in `archive_history`')

    // after all delete items in `archive`
    db.getCollection('archive')
        .deleteMany(
            {
                _id: {
                    $in: itemsIDList
                }
            }
        )
    print('Deleted items in `archive`')

    // step ++
    processed += limit
}

nice idea!

Amazing👌

https://stackoverflow.com/questions/14348516/cascade-style-delete-in-mongoose