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reIndex

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  • Behavior
reIndex

Tip

In the mongo Shell, this command can also be run through the db.collection.reIndex() helper method.

Helper methods are convenient for mongo users, but they may not return the same level of information as database commands. In cases where the convenience is not needed or the additional return fields are required, use the database command.

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:

{ reIndex: <collection> }

The command takes the following fields:

Field
Description
reIndex
The name of the collection to reindex.

Behavior

Note

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

Resource Locking

Changed in version 4.2.2.

For MongoDB 4.2.2 and later, reIndex obtains an exclusive (W) lock on the collection and blocks other operations on the collection until it completes.

For MongoDB 4.0.0 through 4.2.1, reIndex obtains a global exclusive (W) lock and blocks other operations on the mongod until it completes.

For MongoDB 3.6 and earlier, reIndex obtains an exclusive (W) lock on the database and blocks other operations on the database until finished.

For more information on locking in MongoDB, see FAQ: Concurrency.

Tip

See:

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

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