[VSJoin-Exec] Mechanism I gap closure: bounded-staleness read/write decoupling

[ZeroJustMe]

Theme

Mechanism I: Bounded-Staleness Read/Write Decoupling

Problem to close

Current implementation/writeup still has ambiguous mapping between foreground path (insert/probe/verify) and background periodic rebuild path.

Implementation Tasks

• Add or verify explicit staleness knobs in VSJoin config:
  • rebuild period
  • snapshot validity filtering policy
  • optional max-staleness guardrail
• Ensure foreground path remains lock-light and non-blocking w.r.t rebuild.
• Add metrics:
  • staleness age distribution
  • rebuild duration
  • foreground p50/p95/p99 latency under rebuild
• Document non-goal: no event-triggered global rebuild in foreground.

Validation

• Integration test for periodic rebuild visibility semantics.
• Throughput/latency comparison with rebuild on/off and different periods.
• Correctness regression gate under tested settings.

Paper Follow-up (Ch3/Ch4/Ch5)

• Ch3: clarify bounded-staleness objective and trade-off.
• Ch4: add control knobs + runtime behavior.
• Ch5: proposition and figure/table bound to staleness knobs.

Acceptance Criteria

• Reviewer can trace claim -> mechanism -> metric -> figure without gaps.