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db.collection.dropIndex()

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  • Definition
  • Behavior
  • Example

Definition

db.collection.dropIndex(index)

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 or removes the specified index from a collection.

Note

  • You cannot drop the default index on the _id field.

  • Starting in MongoDB 4.2, you cannot specify db.collection.dropIndex("*") to drop all non-_id indexes. Use db.collection.dropIndexes() instead.

To get the index name or the index specification document for the db.collection.dropIndex() method, use the db.collection.getIndexes() method.

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

Parameter
Type
Description
index
string or document

Required. Specifies the index to drop. You can specify the index either by the index name or by the index specification document.

To drop a text index, specify the index name.

Starting in MongoDB 4.2, you cannot specify "*" to drop all non-_id indexes. Use db.collection.dropIndexes() instead.

If an index specified to db.collection.dropIndex() is still building, db.collection.dropIndex() attempts to stop the in-progress build. Stopping an index build has the same effect as dropping the built index. See Stop In-Progress Index Builds for more complete documentation.

Behavior

Starting in MongoDB 5.2, you can use db.collection.dropIndex() 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.

Resource Locking

Changed in version 4.2.

db.collection.dropIndex() 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.dropIndex() releases the lock.

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

Stop In-Progress Index Builds

If an index specified to db.collection.dropIndex() is still building, db.collection.dropIndex() 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.dropIndex() 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.

Example

Consider a pets collection. Calling the db.collection.getIndexes() method on the pets collection returns the following indexes:

[
   {
      "v" : 2,
      "key" : {
         "_id" : 1
      },
      "name" : "_id_"
   },
   {
      "v" : 2,
      "key" : {
         "cat" : -1
      },
      "name" : "catIdx"
   },
   {
      "v" : 2,
      "key" : {
         "cat" : 1,
         "dog" : -1
      },
      "name" : "cat_1_dog_-1"
   }
]

The single field index on the field cat has the user-specified name of catIdx [1] and the index specification document of { "cat" : -1 }.

To drop the index catIdx, you can use either the index name:

db.pets.dropIndex( "catIdx" )

Or you can use the index specification document { "cat" : -1 }:

db.pets.dropIndex( { "cat" : -1 } )
[1] During index creation, if the user does not specify an index name, the system generates the name by concatenating the index key field and value with an underscore, e.g. cat_1.

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db.collection.drop()