Commits on Aug 6, 2026

1. Fix the race condition of updating slot minimum LSN

   Previously, there is a race condition: if a backend creates a new slot and
   attempts to initialize the slot.restart_lsn during WAL reservation, but
   meanwhile, another backend invokes ReplicationSlotsComputeRequiredLSN(), the
   slot minimum LSN may be initially updated by the newly created slot, only to be
   subsequently overwritten by the backend running
   ReplicationSlotsComputeRequiredLSN() with an more recent LSN. This scenario
   could lead to the premature removal of WALs reserved by the new slot during a
   checkpoint, resulting in the newly created slot being invalidated.
   The commit closes this race condition by acquiring an exclusive
   ReplicationSlotControlLock when updating slot.restart_lsn during WAL
   reservation. Additionally, XLogSetReplicationSlotMinimumLSN() is placed under
   the protection of the ReplicationSlotControlLock. This serializes the update of
   slot.restart_lsn and the computation of the minimum LSN in other backends,
   ensuring that a more recent minimum LSN isn't computed while an older one is
   still being reserved.

   

   authored and Commitfest Bot committed

   Aug 6, 2026
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