indexOptionDefaults property
Allows users to specify a default configuration for indexes when creating a collection. The indexOptionDefaults option accepts a storageEngine document, which should take the following form:
{ <storage-engine-name>: <options> }
Storage engine configuration specified when creating indexes are validated and logged to the oplog during replication to support replica sets with members that use different storage engines.
New in version 3.2.
Implementation
final Map<String, dynamic>? indexOptionDefaults;