Horton

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

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Robert Haas <robertmhaas@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-02-18T22:11:17Z
Lists: pgsql-hackers 
Hi,

On 2022-02-18 13:09:45 -0800, Peter Geoghegan wrote:
> 0001 is tricky in the sense that there are a lot of fine details, and
> if you get any one of them wrong the result might be a subtle bug. For
> example, the heap_tuple_needs_freeze() code path is only used when we
> cannot get a cleanup lock, which is rare -- and some of the branches
> within the function are relatively rare themselves. The obvious
> concern is: What if some detail of how we track the new relfrozenxid
> value (and new relminmxid value) in this seldom-hit codepath is just
> wrong, in whatever way we didn't think of?

I think it'd be good to add a few isolationtest cases for the
can't-get-cleanup-lock paths. I think it shouldn't be hard using cursors. The
slightly harder part is verifying that VACUUM did something reasonable, but
that still should be doable?

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