Re: EXPLAIN: showing ReadStream / prefetch stats - Mailing list pgsql-hackers

Hi,

On 2026-09-22 11:35:29 -0400, Peter Geoghegan wrote:
> On Tue, Sep 22, 2026 at 11:23 AM Tomas Vondra <tomas@vondra.me> wrote:
> > In other words, I/O and buffers may disagree - that's not a bug. Those
> > counters are tracking different things.

+1

> > To handle this correctly, we'd need to find a way to not issue the I/O
> > at all (since 862092932c9479b79732f3b441da05453ea5e06d we discard I/O
> > that was not initiated yet).
> 
> Isn't this what Andres' experimental "Make read_stream_reset()/end()
> not wait for IO" patch does? See:
> 
> https://www.postgresql.org/message-id/f3xxfrkafjxpyqxywcxricxgyizjirfceychyxsgn7bwjp5eda@kwbduhy7tfmu
> 
> This is one of the patches that I've been posting as part of the index
> prefetching patch series for some time now.

They're still issued in that patch, we just don't wait for them anymore. But I
think even so, they should still be accounted for.

Greetings,

Andres Freund