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db.collection.dropIndexes()

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  • Definition
  • Behavior

MongoDB with drivers

This page documents a mongosh method. To see the equivalent method in a MongoDB driver, see the corresponding page for your programming language:

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Definition

db.collection.dropIndexes()

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. 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, specify an array of the index names.

Behavior

Cannot Drop Ready Indexes During In-Progress Index Builds

Starting in MongoDB 5.0, dropIndexes raises an error if you attempt to use it to remove the last remaining shard key compatible index. Passing "*" to dropIndexes drops all indexes except the _id index and the last remaining shard key compatible index, if one exists.

Kill related queries only

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.

Resource Locking

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.

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.

Aborts In-Progress Index Builds

New in version 4.4: If an index specified to db.collection.dropIndexes() is still building, dropIndexes() attempts to abort the in-progress build. Aborting an index build has the same effect as dropping the built index. Prior to MongoDB 4.4, dropIndexes() would return an error if the collection had any in-progress index builds.

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

The indexes specified to dropIndexes() must be the entire set of in-progress builds associated to a single createIndexes or db.collection.createIndexes() operation. To drop a specific index out of a set of related in-progress builds, wait until the index builds complete and specify that index to dropIndexes()

For example, a createIndexes / createIndexes() operation creates three indexes. Assuming all three index builds are in-progress, dropIndexes() must specify all three indexes to abort the index builds and drop the indexes.

Use currentOp to identify the index builds associated to a createIndexes / 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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