Problem

From investigation of https://jira.mongodb.org/browse/TOOLS-3965, a timeseries created in server versions from 6.3 on will have an implicitly-created compound index on (time,metadata) which counts against the limit of 64 indexes.

If mongorestore tries to restore a timeseries which doesn't have this index, but has 64 other indexes, then it fail with a server error for "too many indexes".

Solution & Acceptance Criteria

This is a weird edge case, but one possible solution is for mongorestore to check for attempted restore with 64 indexes, and in that case explicitly drop the (time,metadata) index so that there's a slot for all the user-specified indexes.

Impact

Avoid problem in the weird case where a user is trying to have all 64 indexes on a timeseries and restore into 6.3+

Optional Permalinks

https://jira.mongodb.org/browse/TOOLS-3965