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Index Properties

In addition to the numerous index types MongoDB supports, indexes can also have various properties. The following documents detail the index properties that you can select when building an index.

TTL Indexes
The TTL index is used for TTL collections, which expire data after a period of time.
Unique Indexes
A unique index causes MongoDB to reject all documents that contain a duplicate value for the indexed field.
Partial Indexes
A partial index indexes only documents that meet specified filter criteria.
Case Insensitive Indexes
A case insensitive index disregards the case of the index key values.
Sparse Indexes
A sparse index does not index documents that do not have the indexed field.