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: 2024-03-29T07:21:32Z
Lists: pgsql-hackers

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On Thu, Mar 28, 2024 at 12:55 PM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
> I think the patch is in good shape. Do you have other comments or
> suggestions, John?

--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1918,11 +1918,6 @@ include_dir 'conf.d'
         too high.  It may be useful to control for this by separately
         setting <xref linkend="guc-autovacuum-work-mem"/>.
        </para>
-       <para>
-        Note that for the collection of dead tuple identifiers,
-        <command>VACUUM</command> is only able to utilize up to a maximum of
-        <literal>1GB</literal> of memory.
-       </para>
       </listitem>
      </varlistentry>

This is mentioned twice for two different GUCs -- need to remove the
other one, too. Other than that, I just have minor nits:

- * The major space usage for vacuuming is storage for the array of dead TIDs
+ * The major space usage for vacuuming is TID store, a storage for dead TIDs

I think I've helped edit this sentence before, but I still don't quite
like it. I'm thinking now "is storage for the dead tuple IDs".

- * set upper bounds on the number of TIDs we can keep track of at once.
+ * set upper bounds on the maximum memory that can be used for keeping track
+ * of dead TIDs at once.

I think "maximum" is redundant with "upper bounds".

I also feel the commit message needs more "meat" -- we need to clearly
narrate the features and benefits. I've attached how I would write it,
but feel free to use what you like to match your taste.

I've marked it Ready for Committer.

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