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: PostgreSQL-development <pgsql-hackers@postgresql.org>, Nathan Bossart <nathandbossart@gmail.com>, Andres Freund <andres@anarazel.de>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Yura Sokolov <y.sokolov@postgrespro.ru>
Date: 2024-03-01T06:58:07Z
Lists: pgsql-hackers

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I wrote:

> Secondly, I thought about my recent work to skip checking if we first
> need to create a root node, and that has a harmless (for vacuum at
> least) but slightly untidy behavior: When RT_SET is first called, and
> the key is bigger than 255, new nodes will go on top of the root node.
> These have chunk '0'. If all subsequent keys are big enough, the
> orginal root node will stay empty. If all keys are deleted, there will
> be a chain of empty nodes remaining. Again, I believe this is
> harmless, but to make tidy, it should easy to teach RT_EXTEND_UP to
> call out to RT_EXTEND_DOWN if it finds the tree is empty. I can work
> on this, but likely not today.

This turns out to be a lot trickier than it looked, so it seems best
to allow a trivial amount of waste, as long as it's documented
somewhere. It also wouldn't be terrible to re-add those branches,
since they're highly predictable.

I just noticed there are a lot of unused function parameters
(referring to parent slots) leftover from a few weeks ago. Those are
removed in v64-0009. 0010 makes the obvious name change in those
remaining to "parent_slot". 0011 is a simplification in two places
regarding reserving slots. This should be a bit easier to read and
possibly makes it easier on the compiler.

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