Horton

Re: Adding skip scan (including MDAM style range skip scan) to nbtree

Matthias van de Meent <boekewurm+postgres@gmail.com>

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From: Matthias van de Meent <boekewurm+postgres@gmail.com>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Tomas Vondra <tomas@vondra.me>, Mark Dilger <mark.dilger@enterprisedb.com>, Heikki Linnakangas <hlinnaka@iki.fi>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Alexander Korotkov <aekorotkov@gmail.com>
Date: 2025-05-22T17:57:57Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. nbtree: Always set skipScan flag on rescan.

  2. meson: Build numeric.c with -ftree-vectorize.

  3. Fix "variable not found in subplan target lists" in semijoin de-duplication.

  4. Revert "nbtree: Remove useless row compare arg."

  5. nbtree: Remove useless row compare arg.

  6. Prevent premature nbtree array advancement.

  7. nbtree: tighten up array recheck rules.

  8. Avoid treating nonrequired nbtree keys as required.

  9. Adjust overstrong nbtree skip array assertion.

  10. Make NULL tuple values always advance skip arrays.

  11. Avoid extra index searches through preprocessing.

  12. Improve nbtree skip scan primitive scan scheduling.

  13. Further optimize nbtree search scan key comparisons.

  14. Add nbtree skip scan optimization.

  15. Improve nbtree array primitive scan scheduling.

  16. nbtree: Make BTMaxItemSize into object-like macro.

  17. Show index search count in EXPLAIN ANALYZE, take 2.

  18. Make parallel nbtree index scans use an LWLock.

  19. Show index search count in EXPLAIN ANALYZE.

  20. Avoid nbtree parallel scan currPos confusion.

  21. nbtree: Remove useless 'strat' local variable.

  22. Normalize nbtree truncated high key array behavior.

  23. Refactor handling of nbtree array redundancies.

  24. Fix nbtree pgstats accounting with parallel scans.

  25. Avoid parallel nbtree index scan hangs with SAOPs.

  26. Show Parallel Bitmap Heap Scan worker stats in EXPLAIN ANALYZE

  27. Enhance nbtree ScalarArrayOp execution.

  28. Skip checking of scan keys required for directional scan in B-tree

  29. Instead of using a numberOfRequiredKeys count to distinguish required

On Tue, 20 May 2025, 22:14 Peter Geoghegan, <pg@bowt.ie> wrote:
>
> On Mon, May 12, 2025 at 8:58 AM Peter Geoghegan <pg@bowt.ie> wrote:
> > I wonder if we can fix this problem by getting rid of the old support
> > routine #5, "options". It currently doesn't do anything, and I always
> > thought it was strange that it was added "for uniformity" with other
> > index AMs.
>
> Attached patch completely removes the nbtree "options" support
> function, while changing the support function number of skip support:
> it becomes support function #5 (the number previously used by
> "options"). This patch should fix the regression that Tomas complained
> about in an expedient way.

> It's likely that somebody else will run into the same problem in the
> future, the next time that a new support function is needed. But I
> think that it makes sense to do this much now -- we need a short term
> solution for Postgres 18.

Didn't we have different solutions already? E.g. dropping the
allocation requirement from IndexAM (and indeed, making it
non-required), as seen in my 0001? It's a bit of a hassle, but has
shown to have the same effect in PG18b1,  doesn't break compatibility
with existing amproc registrations, and even improves the memory
situation for all other index types.

> Usually I would never suggest breaking
> compatibility like this, but, remarkably, we have never actually done
> anything with our current support function 5. It's not possible to
> break compatibility with code that can never be called in the first
> place, so I see no compatibility to preserve.

I disagree. An extension or user may well have registered FUNCTION 5
for their opclass or opfamily as blanket future-proofed
implementation, which will now break after pg_upgrade. We never
rejected this registration before, and while there won't be issues
with the proc signature across the versions (options' expected
signature is equivalent to that of skipsupport), it will probably
cause issues when it's called with unexpected inputs.

Kind regards,

Matthias van de Meent
Neon (https://neon.tech)