Horton

Re: shared-memory based stats collector - v70

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: melanieplageman@gmail.com, pryzby@telsasoft.com, thomas.munro@gmail.com, david.g.johnston@gmail.com, pgsql-hackers@lists.postgresql.org
Date: 2022-04-07T01:58:52Z
Lists: pgsql-hackers 
Hi,

On 2022-04-07 10:36:30 +0900, Kyotaro Horiguchi wrote:
> At Wed, 6 Apr 2022 09:04:09 -0700, Andres Freund <andres@anarazel.de> wrote in 
> > > +	 * Don't define an INVALID value so switch() statements can warn if some
> > > +	 * cases aren't covered. But define the first member to 1 so that
> > > +	 * uninitialized values can be detected more easily.
> > > 
> > > FWIW, I like this.
> > 
> > I think there's no switches left now, so it's not actually providing too much.
> 
> (Ouch!)

I think it's great that there's no switches left - means we're pretty close to
pgstat being runtime extensible...


> > > 0010:
> > > (I didn't look this closer. The comments arised while looking other
> > > patches.)
> > > 
> > > +pgstat_kind_from_str(char *kind_str)
> > > 
> > > I don't think I like "str" so much.  Don't we spell it as
> > > "pgstat_kind_from_name"?
> >
> > name makes me think of NameData.  What do you dislike about str? We seem to use
> > str in plenty places?
> 
> For clarity, I don't dislike it so much.  So, I'm fine with the
> current name.
> 
> I found that you meant a type by the "str".  I thought it as an
> instance (I'm not sure I can express my feeling correctly here..) and
> the following functions were in my mind.
> 
> char *get_namespace/rel/collation/func_name(Oid someoid)
> char *pgstat_slru_name(int slru_idx)
> 
> Another instance of the same direction is
> 
> ForkNumber forkname_to_number(const char *forkName)

It's now pgstat_get_kind_from_str().

It was harder to see earlier (I certainly didn't really see it) - because
there were so many "violations" - but most of pgstat is
pgstat_<verb>_<subject>() or just <verb>_<subject>. I'd already moved most of
the patch series over to that (maybe in v68 or so). Now I also did that with
the internal functions.

There's a few functions breaking that pattern, partially because I added them
:(, but since they're not touched in these patches I've not renamed them. But
it's probably worth doing so tomorrow.

Greetings,

Andres Freund

Commits

  1. Improve comment about dropped entries in pgstat.c

  2. Fix temporary memory leak in system table index scans

  3. pgstat: set timestamps of fixed-numbered stats after a crash.

  4. pgstat: Update docs to match the shared memory stats reality.

  5. pgstat: Hide instability in stats.spec with -DCATCACHE_FORCE_RELEASE.

  6. pgstat: add/extend tests for resetting various kinds of stats.

  7. Add minimal tests for recovery conflict handling.

  8. pgstat: test stats interactions with physical replication.

  9. pgstat: add tests for handling of restarts, including crashes.

  10. pgstat: add tests for transaction behaviour, 2PC, function stats.

  11. pgstat: add pg_stat_have_stats() test helper.

  12. pgstat: add pg_stat_force_next_flush(), use it to simplify tests.

  13. pgstat: move pgstat.c to utils/activity.

  14. pgstat: store statistics in shared memory.

  15. pgstat: remove stats_temp_directory.

  16. pgstat: rename STATS_COLLECTOR GUC group to STATS_CUMULATIVE.

  17. pgstat: revise replication slot API in preparation for shared memory stats.

  18. pgstat: scaffolding for transactional stats creation / drop.

  19. pgstat: introduce PgStat_Kind enum.

  20. pgstat: prepare APIs used by pgstatfuncs for shared memory stats.

  21. pgstat: add pgstat_copy_relation_stats().

  22. pgstat: rename some pgstat_send_* functions to pgstat_report_*.

  23. pgstat: stats collector references in comments.

  24. pgstat: move transactional code into pgstat_xact.c.

  25. dsm: allow use in single user mode.

  26. dshash: revise sequential scan support.

  27. pgstat: remove some superflous comments from pgstat.h.

  28. pgstat: reorder pgstat.[ch] contents.

  29. pgstat: split different types of stats into separate files.

  30. pgstat: introduce pgstat_relation_should_count().

  31. pgstat: separate "xact level" handling out of relation specific functions.

  32. pgstat: rename pgstat_initstats() to pgstat_relation_init().

  33. pgstat: split out WAL handling from pgstat_{initialize,report_stat}.

  34. pgstat: run pgindent on pgstat.c/h.

  35. pgstat: split relation, database handling out of pgstat_report_stat().

  36. Move code around in StartupXLOG().

  37. pgstat: Prepare to use mechanism for truncated rels also for droppped rels.

  38. pgstat: Split out relation stats handling from AtEO[Sub]Xact_PgStat() etc.

  39. pgstat: Schedule per-backend pgstat shutdown via before_shmem_exit().

  40. Schedule ShutdownXLOG() in single user mode using before_shmem_exit().

  41. Make parallel worker shutdown complete entirely via before_shmem_exit().

  42. pgstat: Bring up pgstat in BaseInit() to fix uninitialized use of pgstat by AV.

  43. pgstat: split reporting/fetching of bgwriter and checkpointer stats.

  44. Split backend status and progress related functionality out of pgstat.c.

  45. Split wait event related code from pgstat.[ch] into wait_event.[ch].

  46. Make archiver process an auxiliary process.

  47. Force to send remaining WAL stats to the stats collector at walwriter exit.

  48. Add pg_stat_database counters for sessions and session time

  49. Collect statistics about SLRU caches

  50. Don't run atexit callbacks in quickdie signal handlers.

  51. Create a "fast path" for acquiring weak relation locks.