Horton

Re: [PoC] Improve dead tuple storage for lazy vacuum

John Naylor <john.naylor@enterprisedb.com>

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From: John Naylor <john.naylor@enterprisedb.com>
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: Nathan Bossart <nathandbossart@gmail.com>, Andres Freund <andres@anarazel.de>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Yura Sokolov <y.sokolov@postgrespro.ru>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2023-07-08T02:54:19Z
Lists: pgsql-hackers

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On Fri, Jul 7, 2023 at 2:19 PM Masahiko Sawada <sawada.mshk@gmail.com>
wrote:
>
> On Wed, Jul 5, 2023 at 8:21 PM John Naylor <john.naylor@enterprisedb.com>
wrote:
> > Well, it's going to be a bit of a mess until I can demonstrate it
working (and working well) with bitmap heap scan. Fixing that now is just
going to create conflicts. I do have a couple small older patches laying
around that were quick experiments -- I think at least some of them should
give a performance boost in loading speed, but haven't had time to test.
Would you like to take a look?
>
> Yes, I can experiment with these patches in the meantime.

Okay, here it is in v36. 0001-6 are same as v35.

0007 removes a wasted extra computation newly introduced by refactoring
growing nodes. 0008 just makes 0011 nicer. Not worth testing by themselves,
but better to be tidy.
0009 is an experiment to get rid of slow memmoves in node4, addressing a
long-standing inefficiency. It looks a bit tricky, but I think it's
actually straightforward after drawing out the cases with pen and paper. It
works if the fanout is either 4 or 5, so we have some wiggle room. This may
give a noticeable boost if the input is reversed or random.
0010 allows RT_EXTEND_DOWN to reduce function calls, so should help with
sparse trees.
0011 reduces function calls when growing the smaller nodes. Not sure about
this one -- possibly worth it for node4 only?

If these help, it'll show up more easily in smaller inputs. Large inputs
tend to be more dominated by RAM latency.

--
John Naylor
EDB: http://www.enterprisedb.com

Commits

  1. radixtree: Fix SIGSEGV at update of embeddable value to non-embeddable.

  2. Get rid of anonymous struct

  3. Teach radix tree to embed values at runtime

  4. Teach TID store to skip bitmap for small numbers of offsets

  5. Use bump context for TID bitmaps stored by vacuum

  6. Fix alignment of stack variable

  7. Use TidStore for dead tuple TIDs storage during lazy vacuum.

  8. Rethink create and attach APIs of shared TidStore.

  9. Fix inconsistent function prototypes with function definitions.

  10. Fix a calculation in TidStoreCreate().

  11. Fix potential integer handling issue in radixtree.h.

  12. Add TIDStore, to store sets of TIDs (ItemPointerData) efficiently.

  13. Fix link error for test_radixtree module on Windows

  14. Blind attempt to fix ODR violations

  15. Fix incorrect format specifier for int64

  16. Fix redefinition of typedefs

  17. Add template for adaptive radix tree

  18. Fix signedness error in 9f225e992 for gcc

  19. Introduce helper SIMD functions for small byte arrays

  20. Optimize vacuuming of relations with no indexes.

  21. Add bound check before bsearch() for performance

  22. Allocate consecutive blocks during parallel seqscans