Week 03 Lecture (21)

PostgreSQL page replacement strategy: clock-sweep

treat buffer pool as circular list of buffer slots
NextVictimBuffer holds index of next possible evictee
if page is pinned or "popular", leave it
- usage_count implements "popularity/recency" measure
- incremented on each access to buffer (up to small limit)
- decremented each time considered for eviction
increment NextVictimBuffer and try again (wrap at end)

For specialised kinds of access (e.g. sequential scan), can allocate a private "buffer ring" with different replacement strategy.