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db.collection.dropIndexes()

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  • Definition
  • Behavior

Definition

db.collection.dropIndexes()

Important

mongosh Method

This page documents a mongosh method. This is not the documentation for database commands or language-specific drivers, such as Node.js.

For the database command, see the dropIndexes command.

For MongoDB API drivers, refer to the language-specific MongoDB driver documentation.

For the legacy mongo shell documentation, refer to the documentation for the corresponding MongoDB Server release:

mongo shell v4.4

Drops the specified index or indexes (except the index on the _id field and the last remaining shard key index) from a collection.

You can use the method to:

  • Drop all but the _id index from a collection.

    db.collection.dropIndexes()

  • Drop a specified index from a collection. To specify the index, you can pass the method either:

    • The index specification document (unless the index is a text index in which case, use the index name to drop):

      db.collection.dropIndexes( { a: 1, b: 1 } )

    • The index name:

      db.collection.dropIndexes( "a_1_b_1" )

      Tip

      To get the names of the indexes, use the db.collection.getIndexes() method.

  • Drop specified indexes from a collection. (Available starting in MongoDB 4.2). To specify multiple indexes to drop, pass the method an array of index names:

    db.collection.dropIndexes( [ "a_1_b_1", "a_1", "a_1__id_-1" ] )

    If the array of index names includes a non-existent index, the method errors without dropping any of the specified indexes.

    Tip

    To get the names of the indexes, use the db.collection.getIndexes() method.

The db.collection.dropIndexes() method takes the following optional parameter:

Parameter
Type
Description
indexes
string or document or array of strings

Optional. Specifies the index or indexes to drop.

To drop all but the _id index from the collection, omit the parameter.

To drop a single index, specify either the index name, the index specification document (unless the index is a text index), or an array of the index name. To drop a text index, specify the index name or an array of the index name instead of the index specification document.

To drop multiple indexes (Available starting in MongoDB 4.2), specify an array of the index names.

Behavior

Starting in MongoDB 6.0, db.collection.dropIndexes() raises an error if you attempt to use it to remove the last remaining shard key compatible index. Passing "*" to db.collection.dropIndexes() drops all indexes except the _id index and the last remaining shard key compatible index, if one exists.

Starting in MongoDB 5.2, you can use db.collection.dropIndexes() to drop existing indexes on the same collection even if there is a build in progress on another index. In earlier versions, attempting to drop a different index during an in-progress index build results in a BackgroundOperationInProgressForNamespace error.

Kill related queries only

Starting in MongoDB 4.2, the dropIndexes() operation only kills queries that are using the index being dropped. This may include queries considering the index as part of query planning.

Prior to MongoDB 4.2, dropping an index on a collection would kill all open queries on the collection.

Resource Locking

Changed in version 4.2.

db.collection.dropIndexes() obtains an exclusive lock on the specified collection for the duration of the operation. All subsequent operations on the collection must wait until db.collection.dropIndexes() releases the lock.

Prior to MongoDB 4.2, db.collection.dropIndexes() obtained an exclusive lock on the parent database, blocking all operations on the database and all its collections until the operation completed.

Index Names

If the method is passed an array of index names that includes a non-existent index, the method errors without dropping any of the specified indexes.

_id Index

You cannot drop the default index on the _id field.

text Indexes

To drop a text index, specify the index name instead of the index specification document.

Stop In-Progress Index Builds

If an index specified to db.collection.dropIndexes() is still building, db.collection.dropIndexes() attempts to stop the in-progress build. Stopping an index build has the same effect as dropping the built index.

For replica sets, run db.collection.dropIndexes() on the primary. The primary stops the index build and creates an associated "abortIndexBuild" oplog entry. Secondaries which replicate the "abortIndexBuild" oplog entry stop the in-progress index build and discard the build job. See Index Build Process for detailed documentation on the index build process.

Use currentOp to identify the index builds associated with a createIndexes or db.collection.createIndexes() operation. See Active Indexing Operations for an example.

Hidden Indexes

MongoDB offers the ability to hide or unhide indexes from the query planner. By hiding an index from the planner, you can evaluate the potential impact of dropping an index without actually dropping the index.

If after the evaluation, the user decides to drop the index, you can drop the hidden index; i.e. you do not need to unhide it first to drop it.

If, however, the impact is negative, the user can unhide the index instead of having to recreate a dropped index. And because indexes are fully maintained while hidden, the indexes are immediately available for use once unhidden.

For more information on hidden indexes, see Hidden Indexes.

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