Efficient way to remove all entries from MongoDB?

MongoDB provides two main methods to remove all entries from a collection: drop() and remove(). The key difference is that drop() deletes the entire collection including indexes, while remove() only deletes documents but preserves the collection structure and indexes.

Syntax

// Method 1: Drop entire collection (fastest)
db.collection.drop()

// Method 2: Remove all documents (preserves indexes)
db.collection.remove({})

// Method 3: Delete all documents (modern approach)
db.collection.deleteMany({})

Method 1: Using drop() (Recommended for Complete Removal)

Let us first create a collection with documents and indexes ?

db.dropWorkingDemo.createIndex({"FirstName":1});
db.dropWorkingDemo.insertOne({"FirstName":"John"});

{
    "createdCollectionAutomatically" : true,
    "numIndexesBefore" : 1,
    "numIndexesAfter" : 2,
    "ok" : 1
}
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5cdd8742bf3115999ed511e9")
}

Display all documents to verify ?

db.dropWorkingDemo.find();

{ "_id" : ObjectId("5cdd8742bf3115999ed511e9"), "FirstName" : "John" }

Now use drop() to remove everything ?

db.dropWorkingDemo.drop();

true

Check if indexes still exist ?

db.dropWorkingDemo.getIndexes();

[ ]

The collection and all indexes are completely removed.

Method 2: Using remove() (Preserves Structure)

Create a new collection with documents and indexes ?

db.removeDemo.createIndex({"FirstName":1});
db.removeDemo.insertOne({"FirstName":"John"});

{
    "createdCollectionAutomatically" : true,
    "numIndexesBefore" : 1,
    "numIndexesAfter" : 2,
    "ok" : 1
}
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5cdd8868bf3115999ed511ea")
}

Use remove() to delete all documents ?

db.removeDemo.remove({});

WriteResult({ "nRemoved" : 1 })

Check if indexes are preserved ?

db.removeDemo.getIndexes();

[
    {
        "v" : 2,
        "key" : {
            "_id" : 1
        },
        "name" : "_id_",
        "ns" : "test.removeDemo"
    },
    {
        "v" : 2,
        "key" : {
            "FirstName" : 1
        },
        "name" : "FirstName_1",
        "ns" : "test.removeDemo"
    }
]

Yes, both the default _id index and custom FirstName index are preserved.

Key Differences

Conclusion

Use drop() for complete collection removal when you don't need indexes. Use remove({}) when you want to preserve the collection structure and indexes for future use.