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

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

From: Matthias van de Meent <boekewurm+postgres@gmail.com>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>, 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: 2025-03-18T17:01:00Z
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 Mon, 17 Mar 2025 at 23:51, Matthias van de Meent
<boekewurm+postgres@gmail.com> wrote:
>
> On Tue, 11 Mar 2025 at 16:53, Peter Geoghegan <pg@bowt.ie> wrote:
> >
> > On Sat, Mar 8, 2025 at 11:43 AM Peter Geoghegan <pg@bowt.ie> wrote:
> > > I plan on committing this one soon. It's obviously pretty pointless to
> > > make the BTMaxItemSize operate off of a page header, and not requiring
> > > it is more flexible.
> >
> > Committed. And committed a revised version of "Show index search count
> > in EXPLAIN ANALYZE" that addresses the issues with non-parallel-aware
> > index scan executor nodes that run from a parallel worker.
> >
> > Attached is v28. This is just to keep the patch series applying
> > cleanly -- no real changes here.
>
> You asked off-list for my review of 0003. I'd already reviewed 0001
> before that, so that review also included. I'll see if I can spend
> some time on the other patches too

My comments on 0004:

> _bt_skiparray_strat_decrement
> _bt_skiparray_strat_increment

In both functions the generated value isn't used when the in/decrement
overflows (and thus invalidates the qual), or when the opclass somehow
doesn't have a <= or >= operator, respectively.
For byval types that's not much of an issue, but for by-ref types
(such as uuid, or bigint on 32-bit systems) that's not great, as btree
explicitly allows no leaks for the in/decrement functions, and now we
use those functions and leak the values.

Additionally, the code is essentially duplicated between the
functions, with as only differences which sksup function to call;
which opstrategies to check, and where to retrieve/put the value. It's
only 2 instances total, but if you figure out how to make a nice
single function from the two that'd be appreciated, as it reduces
duplication and chances for divergence.

Kind regards,

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