readConcern property

ReadConcern? readConcern
final

Starting in MongoDB 3.6, the readConcern option has the following syntax: readConcern: { level:

  • "local". This is the default read concern level for read operations against primary and read operations against secondaries when associated with causally consistent sessions.
  • "available". This is the default for reads against secondaries when when not associated with causally consistent sessions. The query returns the instance’s most recent data.
  • "majority". Available for replica sets that use WiredTiger storage engine.
  • "linearizable". Available for read operations on the primary only. For more formation on the read concern levels, see Read Concern Levels.

Starting in MongoDB 4.2, the $out stage cannot be used in conjunction with read concern "linearizable". That is, if you specify "linearizable" read concern for db.collection.aggregate(), you cannot include the $out stage in the pipeline.

The $merge stage cannot be used in conjunction with read concern "linearizable". That is, if you specify "linearizable" read concern for db.collection.aggregate(), you cannot include the $merge stage in the pipeline.

Implementation

final ReadConcern? readConcern;