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: 2022-11-19T06:05:30Z
Lists: pgsql-hackers 
On Fri, Nov 18, 2022 at 8:20 PM Masahiko Sawada <sawada.mshk@gmail.com>
wrote:
>
> FYI I've not tested the patch you shared today but here are the
> benchmark results I did with the v9 patch in my environment (I used
> the second filter). I splitted 0004 patch into two patches: a patch
> for pure refactoring patch to introduce rt_node_ptr and a patch to do
> pointer tagging.
>
> v9 0003 patch            : 1113 1114 1114
> introduce rt_node_ptr: 1127 1128 1128
> pointer tagging          : 1085 1087 1086 (equivalent to 0004 patch)
>
> In my environment, rt_node_ptr seemed to lead some overhead but
> pointer tagging had performance benefits. I'm not sure the reason why
> the results are different from yours. The radix tree stats shows the
> same as your tests.

There is less than 2% difference from the medial set of results, so it's
hard to distinguish from noise. I did a fresh rebuild and retested with the
same results: about 15% slowdown in v9 0004. That's strange.

On Wed, Nov 16, 2022 at 10:24 PM Masahiko Sawada <sawada.mshk@gmail.com>
wrote:

> > filter = (((uint64) 1<<32) | (0xFF<<24));
> > LOG:  num_keys = 9999944, height = 7, n4 = 47515559, n32 = 6209, n128 =
62632, n256 = 3161
> >
> > 1) Any idea why the tree height would be reported as 7 here? I didn't
expect that.
>
> In my environment, (0xFF<<24) is 0xFFFFFFFFFF000000, not 0xFF000000.
> It seems the filter should be (((uint64) 1<<32) | ((uint64)
> 0xFF<<24)).

Ugh, sign extension, brain fade on my part. Thanks, I'm glad there was a
straightforward explanation.

--
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