hubert depesz lubaczewski <[email protected]> writes:
> First run of the query generated:
> ...
> -> Index Scan using index_some_table_pending on some_table
> (cost=0.42..178322.57 rows=611988 width=16) (actual time=27962.567..27962.567
> rows=0 loops=1)
> Index Cond: (send_at <= '2025-10-23 12:35:48'::timestamp without
> time zone)
> Buffers: shared hit=4624 read=117838 dirtied=486
> Then, immediately I reran it, without reindex, without analyze, without
> anything. And I got:
> -> Index Scan using index_some_table_pending on some_table
> (cost=0.42..178328.27 rows=612009 width=16) (actual time=0.438..0.438 rows=0
> loops=1)
> Index Cond: (send_at <= '2025-10-23 12:35:48'::timestamp without
> time zone)
> Buffers: shared hit=424
> Time is irrelevant, the point is that we are going down from ~120k buffers
> "touched" to 424 buffers. What is going on?
The first execution probably had to set hint bits on a whole lot
of recently-deleted rows.
regards, tom lane
