[nonirosenfeldredis]

Summary

• preserve SVS deletions that race with GC after compact returns
• subtract only the deletion count observed before compaction instead of resetting the full counter
• add a deterministic tiered-index regression test for the post-compact deletion window

Testing

• regression test with the original store(0): fails with num_marked_deleted = 0, expected 1
• regression test with the fix: passes
• clang-format dry run and git diff --check pass

The before/after test was run in an isolated build using the repository-pinned SVS revision because the working tree's pre-existing SVS submodule checkout differs from the pinned commit.

---

Note

Medium Risk
Changes concurrent GC accounting for soft deletes on the SVS backend; incorrect logic could delay or skip compaction triggers, though the fix is narrowly scoped and covered by a targeted regression test.

Overview
Fixes a race in SVS garbage collection where runGC() cleared num_marked_deleted to zero after compact(), so a concurrent delete in the post-compact window could be dropped from the counter and GC might not account for that deletion.

runGC() now snapshots the marked-deleted count at GC start and fetch_subs only that amount after compaction instead of a full reset, so newer increments from overlapping deletes are preserved.

Under BUILD_TESTS, adds setAfterCompactCallbackForTest to run code immediately after compact() and a tiered SVS regression test that deletes during that window and checks the counter and a follow-up GC.

^{Reviewed by Cursor Bugbot for commit 6892476. Bugbot is set up for automated code reviews on this repo. Configure here.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.53%. Comparing base (a59dd72) to head (6892476).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1081      +/-   ##
==========================================
+ Coverage   97.52%   97.53%   +0.01%     
==========================================
  Files         143      143              
  Lines        9697     9702       +5     
==========================================
+ Hits         9457     9463       +6     
+ Misses        240      239       -1     

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