Horton

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

Natalya Aksman <natalya@tigerdata.com>

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From: Natalya Aksman <natalya@tigerdata.com>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Masahiro Ikeda <ikedamsh@oss.nttdata.com>, Tomas Vondra <tomas@vondra.me>, Masahiro.Ikeda@nttdata.com, pgsql-hackers@lists.postgresql.org, Masao.Fujii@nttdata.com
Date: 2025-09-10T19:41:30Z
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

Fantastic, the patch is working, it fixes our issue!

Thank you,
Natalya Aksman.

On Wed, Sep 10, 2025 at 3:12 PM Peter Geoghegan <pg@bowt.ie> wrote:

> On Wed, Sep 10, 2025 at 2:59 PM Natalya Aksman <natalya@tigerdata.com>
> wrote:
> > But after btrescan resets "so->numberOfKeys = 0", so->skipScan is not
> reset to "false" in  _bt_preprocess_keys because of this code:
> https://github.com/postgres/postgres/blob/9016fa7e3bcde8ae4c3d63c707143af147486a10/src/backend/access/nbtree/nbtpreprocesskeys.c#L1847
> > After we set "so->numberOfKeys = 0" we quit on line 1847 before we get
> to the line 1874 where we do "so->skipScan = (numSkipArrayKeys > 0);"
> https://github.com/postgres/postgres/blob/9016fa7e3bcde8ae4c3d63c707143af147486a10/src/backend/access/nbtree/nbtpreprocesskeys.c#L1874
>
> It sounds like the patch that I posted fixes the problem, without you
> having to set so->skipScan externally (which sounds like a big
> kludge). Can you confirm that it actually does fix the problem that
> you're seeing?
>
> TimescaleDB isn't following the letter of the law here. But I do still
> see the argument for consistently setting so->skipScan during
> preprocessing. That at least makes sense on general robustness
> grounds.
>
> --
> Peter Geoghegan
>