Re: pgBufferUsage.blk_{read|write}_time are zero although there are pgBufferUsage.local_blks_{read|written}

Hi,

On Thu, 19 Oct 2023 at 08:26, Michael Paquier <michael@paquier.xyz> wrote:
>
> On Wed, Oct 18, 2023 at 02:56:42PM +0900, Michael Paquier wrote:
> > Thanks for the new versions.  I have applied 0001 and backpatched it
> > for now.  0002 and 0003 look in much cleaner shape than previously.
>
> 0002 and 0003 have now been applied.  I have split 0003 into two parts
> at the end, mainly on clarity grounds: one for the counters with
> EXPLAIN and a second for pg_stat_statements.
>
> There were a few things in the patch set.  Per my notes:
> - Some incorrect indentation.
> - The additions of show_buffer_usage() did not handle correctly the
> addition of a comma before/after the local timing block.  The code
> area for has_local_timing needs to check for has_temp_timing, while
> the area of has_shared_timing needs to check for (has_local_timing ||
> has_temp_timing).
> - explain.sgml was missing an update for the information related to
> the read/write timings of the local blocks.

Thanks for the changes, push and feedback!

>
> Remains what we should do about the "shared/local" string in
> show_buffer_usage() for v16 and v15, as "local" is unrelated to that.
> Perhaps we should just switch to "shared" in this case or just remove
> the string entirely?  Still that implies changing the output of
> EXPLAIN on a stable branch in this case, so there could be an argument
> for leaving this stuff alone.

I think switching it to 'shared' makes sense. That shouldn't confuse
existing monitoring queries much as the numbers won't change, right?
Also, if we keep 'shared/local' there could be similar complaints to
this thread in the future; so, at least adding comments can be
helpful.

Regards,
Nazir Bilal Yavuz
Microsoft