In Get Size Stats for a Collection, we saw how to use db.collection.stats() and its scale parameter to get a useful size metric for a given collection.

We can combine some of this concepts with some scripting to list human-readable size metrics for all of our database's collections:

> db.getCollectionNames().forEach(function (collectionName) {
    sizeInMb = db[collectionName].stats({ scale: 1024 * 1024 }).size;
    print(collectionName   ": "   sizeInMb   "MB");
  })
books: 10MB
authors: 2MB
genres: 1MB

This snippet gets all the collections for the current database and iterates over them. For each collection name, it looks up the size stat for that collection scaled to megabytes and then prints it all out with some contextual information.

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