Re: New criteria for autovacuum

Hi,

> ... and it is claimed that autovacuum will never be triggered in order
> to set hint bits, assuming we never modify the table again.

Actually I waited a bit and got a better EXPLAIN:

```
Index Only Scan using humidity_idx on humidity (cost=0.42..181.36
rows=1970 width=4) (actual time=0.372..16.869 rows=2904.00 loops=1)
Index Cond: ((ts >= '2022-01-01 00:00:00'::timestamp without time
zone) AND (ts < '2022-05-02 00:00:00'::timestamp without time zone)
AND (city = 'M
oscow'::text))
Heap Fetches: 0
Index Searches: 1
Buffers: shared hit=44
Planning Time: 0.520 ms
Execution Time: 17.980 ms
(7 rows)
```

This happens when CHECKPOINT starts:

```
2025-04-03 18:36:23.435 MSK [209952] LOG: checkpoint starting: time
```

Interestingly it takes unusually long for my toy database:

```
2025-04-03 18:40:53.082 MSK [209952] LOG: checkpoint complete: wrote
3522 buffers (5.4%), wrote 1 SLRU buffers; 0 WAL file(s) added, 0
removed, 5 recycled; write=269.463 s, sync=0.029 s, total=269.647 s;
sync files=32, longest=0.004 s, average=0.001 s; distance=68489 kB,
estimate=68489 kB; lsn=0/F4F3870, redo lsn=0/F167DD0
```

There is nothing in between these two lines.

To my humble knowledge, CHECKOINT shouldn't set hint bits and should
take that long. At this point I don't know what's going on.

This is `master` branch, b82e7eddb023.

--
Best regards,
Aleksander Alekseev