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.

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.

Changed in version 2.6: Reindexing operations will error if the index entry for an indexed field exceeds the Maximum Index Key Length. Reindexing operations occur as part of compact and repairDatabase commands as well as the db.collection.reIndex() method.

Because these operations drop all the indexes from a collection and then recreate them sequentially, the error from the Maximum Index Key Length prevents these operations from rebuilding any remaining indexes for the collection and, in the case of the repairDatabase command, from continuing with the remainder of the process.