Standalone nodes will ignore in-progress index builds so as not to deviate from their original replica sets. On rejoining the replica set, in replset mode, the in-progress index builds will be recovered and finished according to whether the replica set committed or aborted the index builds.
This will also require correct handling of neglected index catalog entries if the createIndexes command is called while in standalone mode.
The behavior is as follows:
- createIndex will fail with a CannotBuildIndex error, explaining that the index must be dropped first.
- dropIndex should succeed