Horton

Re: pg_stat_bgwriter.buffers_backend is pretty meaningless (and more?)

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Melanie Plageman <melanieplageman@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, vignesh21@gmail.com, pryzby@telsasoft.com, lukas@fittl.com, alvherre@alvh.no-ip.org, magnus@hagander.net, pgsql-hackers@postgresql.org, thomas.munro@gmail.com, m.sakrejda@gmail.com
Date: 2023-02-27T19:58:30Z
Lists: pgsql-hackers 
Melanie Plageman <melanieplageman@gmail.com> writes:
> On Mon, Feb 27, 2023 at 10:30 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> The risk of needing to cast when using the "int" loop variable
>> as an enum is obviously the downside of that approach, but we have
>> not seen any indication that any compilers actually do warn.
>> It's interesting that you did see such a warning ... I wonder which
>> compiler you were using at the time?

> so, pretty much any version of clang I tried with
> -Wsign-conversion produces a warning.

> <source>:35:32: warning: implicit conversion changes signedness: 'int'
> to 'IOOp' (aka 'enum IOOp') [-Wsign-conversion]

Oh, interesting --- so it's not about the implicit conversion to enum
but just about signedness.  I bet we could silence that by making the
loop variables be "unsigned int".  I doubt it's worth any extra keystrokes
though, because we are not at all clean about sign-conversion warnings.
I tried enabling -Wsign-conversion on Apple's clang 14.0.0 just now,
and counted 13462 such warnings just in the core build :-(.  I don't
foresee anybody trying to clean that up.

> I didn't do the casts in the attached patch since they aren't done elsewhere.

Agreed.  I'll push this along with the earlier patch if there are
not objections.

			regards, tom lane

Commits

  1. Stabilize pg_stat_io writes test

  2. Fix flakey pg_stat_io test

  3. Suppress more compiler warnings in new pgstats code.

  4. Suppress compiler warnings in new pgstats code.

  5. Add tests for pg_stat_io

  6. Create regress_tblspc in test_setup

  7. Add pg_stat_io view, providing more detailed IO statistics

  8. pgstat: Track more detailed relation IO statistics

  9. pgstat: Infrastructure for more detailed IO statistics

  10. doc: Fix some issues in logical replication section

  11. Manual cleanup and pgindent of pgstat and bufmgr related code

  12. Have the planner consider Incremental Sort for DISTINCT

  13. Use actual backend IDs in pg_stat_get_backend_idset() and friends.

  14. Remove redundant call to pgstat_report_wal()

  15. Add BackendType for standalone backends

  16. Initialize backend status reporting during bootstrap.