db.collection.reIndex()¶

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Behavior

db.collection.reIndex()¶

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.

Important

db.collection.reIndex() always builds indexes in the foreground due to the logic described in Multiple Index Builds.

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

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.