MongoDB deleteMany() Method

The deleteMany() method in MongoDB is used to remove all documents from a collection that match a specified filter. It is ideal for bulk deletions, supports multi-document transactions, and ensures efficient data management.

• Deletes multiple documents that match a specified filter.
• Returns a result containing the number of deleted documents.
• Cannot be used on capped collections.
• Supports write concern and collation options.

Syntax

db.collection.deleteMany(<filter>, {writeConcern: <document>, collation: <document>})

• filter: Selection criteria for deletion, {} deletes all documents.
• writeConcern: Sets the write concern level for the operation.
• collation: Defines language-specific rules for string comparison.
• acknowledged: Indicates whether the operation was acknowledged (true by default unless write concern is set to w: 0).
• deletedCount: The total number of documents deleted.

Return Value of deleteMany()

The deleteMany() method returns a document containing:

• acknowledged: A boolean indicating whether the operation was acknowledged based on the write concern.
• deletedCount: The number of documents deleted (can be zero or more depending on the filter).

Examples of MongoDB deleteMany() Method

In the following examples we are working with:

• Database: GeeksforGeeks
• Collection: contributor
• Document: Four documents that contain the details of the contributors in the form of field-value pairs.

Example 1: Deleting Documents That Match a Filter

Deletes all documents in which language field contains C#.

Query:

db.contributor.deleteMany({ language: "C#" });

Output:

• The query { language: "C#" } matches two documents.
• Both matching documents are deleted.
• The operation returns deletedCount: 2, confirming that two documents were removed successfully.

Example 2: Deleting All Documents in a Collection

Deleting all the documents from the contributor collection by passing empty filter in the db.collection.deleteMany() method.

Query:

db.contributor.deleteMany({})

Output:

• Since the filter is {}, it matches all documents.
• Every document in the contributors collection is deleted.
• The output confirms the number of deleted documents.

Note: Use deleteMany({}) to remove all documents while keeping the collection and indexes, whereas drop() removes the entire collection including its structure and indexes.

Example 3: Using Query Operators with deleteMany()

Delete all contributors whose _id is greater than 2.

Query:

db.contributor.deleteMany({ _id: { $gt: 2 } });

Output:

• The condition { _id: { $gt: 2 } } selects documents where _id is greater than 2.
• Two matching documents are found and deleted.
• The operation confirms deletion with deletedCount: 2.

Best Practices for Using deleteMany() in MongoDB

Here are some best practices discussed:

• Always use a filter: An empty {} deletes all documents.
• Use indexes: Index the filter field to speed up deletion.
• Test before deleting: Run find() first to confirm matched documents.
• Set write concern for critical ops: Ensures reliable and consistent writes.
• Use collation when needed: Enables case-insensitive deletions.