Horton

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

Justin Pryzby <pryzby@telsasoft.com>

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From: Justin Pryzby <pryzby@telsasoft.com>
To: Andres Freund <andres@anarazel.de>
Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>, melanieplageman@gmail.com, vignesh21@gmail.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: 2023-02-22T01:50:35Z
Lists: pgsql-hackers 
On Sat, Feb 11, 2023 at 10:24:37AM -0800, Andres Freund wrote:
> On 2023-02-08 21:03:19 -0800, Andres Freund wrote:
> > Pushed the first (and biggest) commit. More tomorrow.
> 
> Just pushed the actual pg_stat_io view, the splitting of the tablespace test,
> and the pg_stat_io tests.

pg_stat_io says:

         * Some BackendTypes do not currently perform any IO in certain
         * IOContexts, and, while it may not be inherently incorrect for them to
         * do so, excluding those rows from the view makes the view easier to use.

        if (bktype == B_AUTOVAC_LAUNCHER && io_context == IOCONTEXT_VACUUM)
                return false;

        if ((bktype == B_AUTOVAC_WORKER || bktype == B_AUTOVAC_LAUNCHER) &&
                io_context == IOCONTEXT_BULKWRITE)
                return false;

What about these combinations?  Aren't these also "can't happen" ?

 relation      | bulkread   | autovacuum worker
 relation      | bulkread   | autovacuum launcher
 relation      | vacuum     | startup

-- 
Justin

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.