Horton

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

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Tomas Vondra <tomas@vondra.me>
Cc: Matthias van de Meent <boekewurm+postgres@gmail.com>, Mark Dilger <mark.dilger@enterprisedb.com>, Heikki Linnakangas <hlinnaka@iki.fi>, pgsql-hackers@lists.postgresql.org, Alexander Korotkov <aekorotkov@gmail.com>
Date: 2025-05-20T20:13:41Z
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

Attachments

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. 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.

Questions for Alexander about the "options" support function:

* Why did you invent the whole idea of an "options" support function,
given that it doesn't actually do anything? I get that it might be a
good idea to add these kinds of functions in the future, but why
didn't you wait until nbtree *actually had a use* for them?

* I've removed some of the tests that you added, that (for whatever
reason) cover nbtree specifically. The test from alter_generic.sql.
There might be some kind of loss of test coverage. What do you think?

-- 
Peter Geoghegan