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: 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: 2022-03-31T16:37:15Z
Lists: pgsql-hackers 
Hi,

On 2022-03-30 21:59:15 -0700, Andres Freund wrote:
> On 2022-03-30 21:29:16 -0700, Peter Geoghegan wrote:
> > On Wed, Mar 30, 2022 at 9:20 PM Andres Freund <andres@anarazel.de> wrote:
> > > Perhaps we should just fetch the horizons from the "local" catalog for shared
> > > rels?
> > 
> > Not sure what you mean.
> 
> Basically, instead of relying on the relcache, which for shared relation is
> vulnerable to seeing "too new" horizons due to the shared relcache init file,
> explicitly load relfrozenxid / relminmxid from the the catalog / syscache.
> 
> I.e. fetch the relevant pg_class row in heap_vacuum_rel() (using
> SearchSysCache[Copy1](RELID)). And use that to set vacrel->relfrozenxid
> etc. Whereas right now we only fetch the pg_class row in
> vac_update_relstats(), but use the relcache before.

Perhaps we should explicitly mask out parts of relcache entries in the shared
init file that we know to be unreliable. I.e. set relfrozenxid, relminmxid to
Invalid* or such.

I even wonder if we should just generally move those out of the fields we have
in the relcache, not just for shared rels loaded from the init
fork. Presumably by just moving them into the CATALOG_VARLEN ifdef.

The only place that appears to access rd_rel->relfrozenxid outside of DDL is
heap_abort_speculative().

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