Horton

Re: shared-memory based stats collector - v66

Kyotaro Horiguchi <horikyota.ntt@gmail.com>

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From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
To: melanieplageman@gmail.com
Cc: andres@anarazel.de, ibrar.ahmad@gmail.com, masao.fujii@oss.nttdata.com, gkokolatos@protonmail.com, pgsql-hackers@lists.postgresql.org
Date: 2022-03-25T05:22:56Z
Lists: pgsql-hackers 
At Thu, 24 Mar 2022 13:21:33 -0400, Melanie Plageman <melanieplageman@gmail.com> wrote in 
> On Thu, Mar 17, 2022 at 3:36 AM Andres Freund <andres@anarazel.de> wrote:
> >
> > The biggest todos are:
> > - Address all the remaining AFIXMEs and XXXs
> 
> Attached is a patch that addresses three of the existing AFIXMEs.

Thanks!

+		.reset_timestamp_cb = pgstat_shared_reset_timestamp_noop,

(I once misunderstood that the "shared" means shared memory area..)

The reset function is type-specific and it must be set.  So don't we
provide all to-be-required reset functions?


+	if (pgstat_shared_ref_get(kind, dboid, objoid, false, NULL))
+	{
+		Oid msg_oid = (kind == PGSTAT_KIND_DB) ? dboid : objoid;

Explicitly using PGSTAT_KIND_DB here is a kind of annoyance.  Since we
always give InvalidOid correctly as the parameters, and objoid alone
is not specific enough, do we warn using both dboid and objoid without
a special treat?

Concretely, I propose to do the following instead.

+	if (pgstat_shared_ref_get(kind, dboid, objoid, false, NULL))
+	{
+		ereport(WARNING,
+				errmsg("resetting existing stats for type %s, db=%d, oid=%d",
+                      pgstat_kind_info_for(kind)->name, dboid, objoid);				



+pgstat_pending_delete(PgStatSharedRef *shared_ref)
+{
+	void	   *pending_data = shared_ref->pending;
+	PgStatKind kind = shared_ref->shared_entry->key.kind;
+
+	Assert(pending_data != NULL);
+	Assert(!pgstat_kind_info_for(kind)->fixed_amount);
+
+	/* PGSTAT_KIND_TABLE has its own callback */
+	Assert(kind != PGSTAT_KIND_TABLE);
+

"kind" is used only in assertion, which requires PG_USED_FOR_ASSERTS_ONLY.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center

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.