Horton

Re: Removing more vacuumlazy.c special cases, relfrozenxid optimizations

Andres Freund <andres@anarazel.de>

View thread View on postgr.es
From: Andres Freund <andres@anarazel.de>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Justin Pryzby <pryzby@telsasoft.com>, Robert Haas <robertmhaas@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-03-31T04:24:43Z
Lists: pgsql-hackers 
Hi,

On 2022-03-30 21:11:48 -0700, Peter Geoghegan wrote:
> On Wed, Mar 30, 2022 at 9:04 PM Andres Freund <andres@anarazel.de> wrote:
> > (gdb) p vacrel->NewRelfrozenXid
> > $3 = 717
> > (gdb) p vacrel->relfrozenxid
> > $4 = 717
> > (gdb) p OldestXmin
> > $5 = 5112
> > (gdb) p aggressive
> > $6 = false
>
> Does this OldestXmin seem reasonable at this point in execution, based
> on context? Does it look too high? Something else?

Reasonable:
(gdb) p *ShmemVariableCache
$1 = {nextOid = 78969, oidCount = 2951, nextXid = {value = 21411}, oldestXid = 714, xidVacLimit = 200000714, xidWarnLimit = 2107484361,
  xidStopLimit = 2144484361, xidWrapLimit = 2147484361, oldestXidDB = 1, oldestCommitTsXid = 0, newestCommitTsXid = 0, latestCompletedXid = {value = 21408},
  xactCompletionCount = 1635, oldestClogXid = 714}

I think the explanation I just sent explains the problem, without "in-memory"
confusion about what's running and what's not.

Greetings,

Andres Freund

Commits

  1. Have VACUUM warn on relfrozenxid "in the future".

  2. vacuumlazy.c: Further consolidate resource allocation.

  3. Generalize how VACUUM skips all-frozen pages.

  4. Set relfrozenxid to oldest extant XID seen by VACUUM.

  5. Doc: Add relfrozenxid Tip to XID wraparound section.

  6. vacuumlazy.c: document vistest and OldestXmin.

  7. Increase hash_mem_multiplier default to 2.0.

  8. Consolidate VACUUM xid cutoff logic.

  9. Add VACUUM instrumentation for scanned pages, relfrozenxid.

  10. Simplify lazy_scan_heap's handling of scanned pages.

  11. Try to stabilize reloptions test, again.

  12. Unify VACUUM VERBOSE and autovacuum logging.

  13. Fix possible HOT corruption when RECENTLY_DEAD changes to DEAD while pruning.

  14. pg_resetxlog: add option to set oldest xid & use by pg_upgrade

  15. Teach VACUUM to bypass unnecessary index vacuuming.

  16. Centralize horizon determination for temp tables, fixing bug due to skew.

  17. pg_surgery: Try to stabilize regression tests.

  18. Add "split after new tuple" nbtree optimization.

  19. Fix bugs in vacuum of shared rels, by keeping their relcache entries current.

  20. Avoid useless truncation attempts during VACUUM.

  21. Only skip pages marked as clean in the visibility map, if the last 32

  22. Fix recently-understood problems with handling of XID freezing, particularly