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, Justin Pryzby <pryzby@telsasoft.com>, Thomas Munro <thomas.munro@gmail.com>, "David G. Johnston" <david.g.johnston@gmail.com>, pgsql-hackers@lists.postgresql.org
Date: 2022-04-06T22:12:25Z
Lists: pgsql-hackers 
Hi,

On 2022-04-05 20:00:08 -0700, Andres Freund wrote:
> It'll be a few hours to get to the main commit - but except for 0001 it
> doesn't make sense to push without intending to push later changes too. I
> might squash a few commits togther.

I just noticed an existing incoherency that I'm wondering about fixing as part
of 0007 "pgstat: prepare APIs used by pgstatfuncs for shared memory stats."

The SQL functions to reset function and relation stats
pg_stat_reset_single_table_counters() and
pg_stat_reset_single_function_counters() respectively both make use of
pgstat_reset_single_counter().

Note that the SQL function uses plural "counters" (which makes sense, it
resets all counters for that object), whereas the C function they call to
perform the the reset uses singular.

Similarly pg_stat_reset_slru(), pg_stat_reset_replication_slot(),
pg_stat_reset_subscription_stats() SQL function use
pgstat_reset_subscription_counter(), pgstat_reset_replslot_counter() and
pgstat_reset_subscription_counter() to reset either the stats for one or all
SLRUs/slots.

This is relevant for the commit mentioned above because it separates the
functions to reset the stats for one slru / slot / sub from the function to
reset all slrus / slots / subs. Going with the existing naming I'd just named
them pgstat_reset_*_counters(). But that doesn't really make sense.


If it were just existing code I'd just not touch this for now. But because the
patch introduces further functions, I'd rather not introducing more weird
function names.

I'd go for
pgstat_reset_slru_counter() -> pgstat_reset_slru()
pgstat_reset_subscription_counter() -> pgstat_reset_subscription()
pgstat_reset_subscription_counters() -> pgstat_reset_all_subscriptions()
pgstat_reset_replslot_counter() -> pgstat_reset_replslot()
pgstat_reset_replslot_counters() -> pgstat_reset_all_replslots()

We could leave out the _all_ and just use plural too, but I think it's a bit
nicer with _all_ in there.

Not quite sure what to do with pgstat_reset_single_counter(). I'd either go
for the minimal pgstat_reset_single_counters() or pgstat_reset_one()?

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.