This ticket originated from issues 5 and 6 from the "Known situations where contracts unmet" section of the MongoDB Server read and write semantics doc.

This issue applies to read operations using coll scan or _id index scan with "rc:local", "rc:majority", and "rc:linearizable" running inside or outside of a transaction.

Such read operations, when run concurrently with shard key value updates, can miss documents or visit the same document multiple times, violating the semantics in the read/write semantics doc (linked above).

The goal of this ticket is to improve the implementation of read operations using coll scan or _id index scan so that such read operations do not miss documents or visit the same documents multiple times when there are concurrent shard key value updates running.