checkpoint

The inclusive boundary checkpoint that the scan has fully covered within the request's effective interval, in the request's ordering direction: an ascending scan has emitted every matching item in the interval at checkpoints <= checkpoint (strictly greater ones may still hold matches); a descending scan has emitted every matching item in the interval at checkpoints >= checkpoint. This boundary never regresses in the scan direction, but it may repeat while the cursor advances.

Unset until the scan's first checkpoint is fully covered. For example, a scan resumed from a cursor that lands mid-checkpoint leaves this unset until the next checkpoint boundary in the scan direction is fully covered. A watermark still has a valid resume cursor while this field is unset.