Horton

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

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Andres Freund <andres@anarazel.de>
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: 2022-03-31T17:16:59Z
Lists: pgsql-hackers 
On Thu, Mar 31, 2022 at 10:11 AM Andres Freund <andres@anarazel.de> wrote:
> I don't think we should weaken defenses against xids from before relfrozenxid
> in vacuum / amcheck / .... If anything we should strengthen them.
>
> Isn't it also just plainly required for correctness? We'd not necessarily
> trigger a vacuum in time to remove the xid before approaching wraparound if we
> put in an xid before relfrozenxid? That happening in prune_xid is obviously
> les bad than on actual data, but still.

Yeah, you're right. Ambiguity about stuff like this should be avoided
on general principle.

> ISTM we should just use our own xid. Yes, it might delay cleanup a bit
> longer. But unless there's already crud on the page (with prune_xid already
> set, the abort of the speculative insertion isn't likely to make the
> difference?

Speculative insertion abort is pretty rare in the real world, I bet.
The speculative insertion precheck is very likely to work almost
always with real workloads.

-- 
Peter Geoghegan

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