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: PostgreSQL-development <pgsql-hackers@postgresql.org>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, 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: 2023-10-28T08:56:42Z
Lists: pgsql-hackers

Attachments

I wrote:

> Seems fine at a glance, thanks. I will build on this to implement variable-length values. I have already finished one prerequisite which is: public APIs passing pointers to values.

Since my publishing schedule has not kept up, I'm just going to share
something similar to what I mentioned earlier, just to get things
moving again.

0001-0009 are from earlier versions, except for 0007 which makes a
bunch of superficial naming updates, similar to those done in a recent
other version. Somewhere along the way I fixed long-standing git
whitespace warnings, but I don't remember if that's new here. In any
case, let's try to preserve that.

0010 is some minor refactoring to reduce duplication

0011-0014 add public functions that give the caller more control over
the input and responsibility for locking. They are not named well, but
I plan these to be temporary: They are currently used for the tidstore
only, since that has much simpler tests than the standard radix tree
tests. One thing to note: since the tidstore has always done it's own
locking within a larger structure, these patches don't bother to do
locking at the radix tree level. Locking twice seems...not great.
These patches are the main prerequisite for variable-length values.
Once that is working well, we can switch the standard tests to the new
APIs.

Next steps include (some of these were briefly discussed off-list with
Sawada-san):

- template parameter for varlen values
- some callers to pass length in bytes
- block entries to have num_elems for # of bitmap words
- a way for updates to re-alloc values when needed
- aset allocation for values when appropriate

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