пагинация (курсор vs offset): ментальная модель

Question

Accepted Answer

Offset = skip N (slow, shifts on live data). Cursor = after this row (stable, O(1)). Infinite scroll on live feeds — cursors, full stop.

## Разбор

Both = «next slice», different pointer:

- **Offset** — **«skip N, take M»**, absolute *position*. `LIMIT 20 OFFSET 40` = page 3. List changes → positions move.
- **Cursor (keyset)** — **«start after this item»**, pointer to stable value. `WHERE id < 8423 ORDER BY id DESC LIMIT 20`. Row reference, not slot.

```
Offset:  [ · · · · · · · · · · ]   "skip 40, take 20"  ← counts from the start every time
Cursor:  [ · · · · ·│next 20···]   "after id=8423"     ← jumps straight to the boundary
```

Offset = **position in list that can shift**; cursor = **reference to row that stays put**.

## Итог

Live infinite scroll → cursors; admin «page 47 of 200» → offset with eyes open to cost and drift.