When implementing validation for CSI, we found two collections which apparently do not update indexes when written to, namely:

• local.replset.oplogTruncateAfterPoint
• config.transactions

geert.bosch@mongodb.com commented in a discussion with charlie.swanson@mongodb.com that such behavior is not unexpected in local.replset.oplogTruncateAfterPoint , but we don't know for sure about config.transaction. We'd like to get someone to confirm this.

We have a failpoint which puts CSI on all collections for testing, but these two collections are exempt (via this helper function). We want to be sure that is the correct thing to do.