– Workload: N workers perform CAS updates
UPDATE … SET s{i}=new WHERE pk=? IF (∀j≠i: s{j}>=guard_j) AND s{i}=prev
at CL=LOCAL_QUORUM / SERIAL=LOCAL_SERIAL. Non-apply without timeout is treated
as contention; “uncertainty” timeouts are resolved via LOCAL_SERIAL read.
- Enable balancing and increase min_tablet_count to force split,
flush and lower min_tablet_count to merge.
- “Uncertainty” timeouts (write timeout due to uncertainty) are resolved via a
LOCAL_SERIAL read to determine whether the CAS actually applied.
- Invariants: after the run, for every pk and column s{i}, the stored value
equals the number of confirmed CAS by worker i (no lost or phantom updates)
despite ongoing tablet moves.
Closesscylladb/scylladb#26113
E2E test runs multi-column CAS workload (LOCAL_QUORUM/LOCAL_SERIAL) while
tablets are repeatedly migrated between nodes. Uncertainty timeouts are
resolved via LOCAL_SERIAL reads; guards use max(row, lower_bound). Final
assertion: s{i} per (pk,i) equals the count of confirmed CAS by worker i
(no lost/phantom updates) despite tablet moves.
Closesscylladb/scylladb#25402
