reIndex¶

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Behavior

reIndex¶

The reIndex command drops all indexes on a collection and recreates them. This operation may be expensive for collections that have a large amount of data and/or a large number of indexes.

Warning

For most users, the reIndex command is unnecessary.
Avoid running reIndex for a replica set.
Do not run reIndex against a collection in a sharded cluster.

Changed in version 4.2: MongoDB disallows reIndex to be run on a mongos, implementing a stronger restriction against running reIndex for a collection in a sharded cluster.

Use the following syntax:

copy

{ reIndex: <collection>, writeConcern: <document>}

The command takes the following fields:

Field	Description
reIndex	The name of the collection to reindex.
writeConcern	Optional. A document expressing the write concern of the `drop` command. Omit to use the default write concern.

The mongo shell provides a wrapper db.collection.reIndex().

Behavior¶

Note

For replica sets, reIndex will not propagate from the primary to secondaries. reIndex will only affect a single mongod instance.

Important

reIndex always builds indexes in the foreground due to the logic described in Multiple Index Builds.

Starting in MongoDB 4.0, reIndex takes a global exclusive (W) lock and will block other operations until it finishes.

See

Index Builds on Populated Collections for more information on the behavior of indexing operations in MongoDB.

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