db.collection.reIndex()¶

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Behavior

db.collection.reIndex()¶

mongo Shell Method

This page documents the mongo shell method, and does not refer to the MongoDB Node.js driver (or any other driver) method. For corresponding MongoDB driver API, refer to your specific MongoDB driver documentation instead.

The db.collection.reIndex() 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 db.collection.reIndex() operation is unnecessary.
Avoid running db.collection.reIndex() against a collection in a replica set.
Do not run db.collection.reIndex() against a collection in a sharded cluster.

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

Behavior¶

Note

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

For MongoDB 2.6 through MongoDB versions with featureCompatibilityVersion (fCV) set to "4.0" or earlier, MongoDB will not create an index on a collection if the index entry for an existing document exceeds the Maximum Index Key Length.

Resource Locking¶

Changed in version 4.2.2.

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

For MongoDB 3.6 and earlier, these operations db.collection.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.