Timely Byte Reclamation After Deletions

Develop database mechanisms that ensure timely byte reclamation after logical deletions, providing explicit guarantees on when the physical storage corresponding to deleted values is reclaimed.

Background

The paper distinguishes between logical deletion (e.g., DELETE statements and MVCC visibility) and physical deletion (actual byte reclamation via processes such as VACUUM in MVCC engines or compaction/tombstone collection in LSM-based engines). It emphasizes that logical removal does not immediately reclaim storage and that the timing of reclamation is governed by background maintenance processes.

Because these processes can be delayed or scheduled unpredictably, there is a nontrivial gap between when data becomes inaccessible at the logical layer and when its bytes are actually removed from storage. The authors explicitly note that achieving timeliness in this reclamation is an open research problem, even though it is orthogonal to the paper’s main focus on inference-aware guarantees.