MongoDB Drop Index

Summary: in this tutorial, you’ll learn how to use the MongoDB dropIndex() method to drop an index from a collection.

Introduction to the MongoDB drop index

To drop an index from a collection, you use the db.collection.dropIndex() method:

db.collection.dropIndex(index)
Code language: CSS (css)

In this syntax, the index specifies an index to be dropped. The index can be either a string that specifies the name of an index or a document that describes the specification of the index that you want to drop.

Note that you cannot drop the default index on the _id field.

Starting in MongoDB 4.2, you cannot use the db.collection.dropIndex('*') to drop all non-_id indexes. Instead, you use the dropIndexes() method:

db.collection.dropIndexes()
Code language: CSS (css)

MongoDB drop index examples

Let’s take some examples of dropping one or more indexes from a collection.

1) Drop an index example

First, create a new index for the year field in the movies collection:

db.movies.createIndex({year: 1})
Code language: CSS (css)

Output:

year_1

In this example, the createIndex() method creates an index with the name year_1.

Second, show all the indexes of the movies collection by using the getIndexes() method:

db.movies.getIndexes()
Code language: CSS (css)

Output:

[
  { v: 2, key: { _id: 1 }, name: '_id_' },
  { v: 2, key: { year: 1 }, name: 'year_1' }
]
Code language: JavaScript (javascript)

Third, drop the year_1 index using the dropIndex() method:

db.movies.dropIndex('year_1')
Code language: JavaScript (javascript)

Output:

{ nIndexesWas: 2, ok: 1 }
Code language: CSS (css)

The output shows that one index has been dropped.

Finally, verify the index deletion using the getIndexes() method:

db.movies.getIndexes()
Code language: CSS (css)

Output:

[ { v: 2, key: { _id: 1 }, name: '_id_' } ]
Code language: CSS (css)

The output shows that the year_1 index was deleted and is not in the index list of the movies collection.

2) Drop an index by the index specification

First, create an index for runtime field in the movies collection:

db.movies.createIndex({runtime: -1})
Code language: CSS (css)

Second, list the indexes of the movies collection:

db.movies.getIndexes()
Code language: CSS (css)

Output:

[
  { v: 2, key: { _id: 1 }, name: '_id_' },
  { v: 2, key: { runtime: -1 }, name: 'runtime_-1' }
]
Code language: JavaScript (javascript)

Third, drop the index runtime_-1 but use the index specification instead of the index name:

db.movies.dropIndex({runtime: -1});
Code language: CSS (css)

Output:

{ nIndexesWas: 2, ok: 1 }
Code language: CSS (css)

3) Drop all non-_id indexes example

First, create two indexes for the year and runtime fields of the movies collection:

db.movies.createIndex({year: 1})
db.movies.createIndex({runtime: 1})
Code language: CSS (css)

Second, show the indexes of the movies collection:

db.movies.getIndexes()
Code language: CSS (css)

Output:

[
  { v: 2, key: { _id: 1 }, name: '_id_' },
  { v: 2, key: { year: 1 }, name: 'year_1' },
  { v: 2, key: { runtime: 1 }, name: 'runtime_1' }
]
Code language: JavaScript (javascript)

Third, drop all non-_id indexes of movies collection using the dropIndexes() method:

db.movies.dropIndexes()
Code language: CSS (css)

Output:

{
  nIndexesWas: 3,
  msg: 'non-_id indexes dropped for collection',
  ok: 1
}
Code language: CSS (css)

Summary

• Use the dropIndex() to drop an index specified by name or specification from a collection.
• The default index for the _id field cannot be dropped.
• Use the dropIndexes() to drop all non-_id indexes of a collection.