- explains replay, the row chain, how a checkpoint flattens it, and why
replay of a long chain is quadratic
- worked SKU example with the actual record layout and back-pointers,
and a trace of the fold showing first-seen-wins
- states plainly why the checkpoint does not bound the hot-row case:
both triggers are ratios over the whole log and nothing counts
per-row chain length
- records the bounded-memory vs linear-time conflict behind the O(N^2)
replay rather than presenting it as an oversight
- closes with the reviewing lesson, since this shape survived several
rounds: complexity bugs hide in the caller's loop, not in the linear
helper being read
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
(cherry picked from commit e6434403d566b5d72a24e9c0dcad1f25a2c16320)
