Horton

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

John Naylor <johncnaylorls@gmail.com>

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From: John Naylor <johncnaylorls@gmail.com>
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: Noah Misch <noah@leadboat.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2024-04-25T03:17:06Z
Lists: pgsql-hackers 
On Thu, Apr 25, 2024 at 9:50 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> > I saw a SIGSEGV there when using tidstore to write a fix for something else.
> > Patch attached.
>
> Great find, thank you for the patch!

+1

(This occurred to me a few days ago, but I was far from my computer.)

With the purge function that  Noah proposed, I believe we can also get
rid of the comment at the top of the .sql test file warning of a
maintenance hazard:
..."To avoid adding duplicates,
-- each call to do_set_block_offsets() should use different block
-- numbers."

I found that it doesn't add any measurable time to run the test.

> The fix looks good to me. I think we can improve regression tests for
> better coverage. In TidStore on a 64-bit machine, we can store 3
> offsets in the header and these values are embedded to the leaf page.
> With more than 3 offsets, the value size becomes more than 16 bytes
> and a single value leaf. Therefore, if we can add the test with the
> array[1,2,3,4,100], we can cover the case of replacing a single-value
> leaf with a different size new single-value leaf. Now we add 9 pairs

Good idea.

> of do_gset_block_offset() and check_set_block_offsets(). If these are
> annoying, we can remove the cases of array[1] and array[1,2].

Let's keep those -- 32-bit platforms should also exercise this path.

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