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:

Cc: Peter Geoghegan <pg@bowt.ie>, 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: 2025-04-01T22:08:55Z

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 →

nbtree: Always set skipScan flag on rescan.
- 454c046094ab 19 (unreleased) landed
- bee763aea13f 18.0 landed
meson: Build numeric.c with -ftree-vectorize.
- 9016fa7e3bcd 19 (unreleased) cited
Fix "variable not found in subplan target lists" in semijoin de-duplication.
- b8a1bdc458e3 19 (unreleased) cited
Revert "nbtree: Remove useless row compare arg."
- dd2ce3792754 18.0 landed
nbtree: Remove useless row compare arg.
- 54c6ea8c81db 18.0 cited
Prevent premature nbtree array advancement.
- 5f4d98d4f371 18.0 landed
nbtree: tighten up array recheck rules.
- 7e25c9363a82 18.0 landed
Avoid treating nonrequired nbtree keys as required.
- 0f08df406822 18.0 landed
Adjust overstrong nbtree skip array assertion.
- 9d924dbb3710 18.0 landed
Make NULL tuple values always advance skip arrays.
- b75fedcab791 18.0 cited
Avoid extra index searches through preprocessing.
- b3f1a13f22f9 18.0 landed
Improve nbtree skip scan primitive scan scheduling.
- 21a152b37f36 18.0 landed
Further optimize nbtree search scan key comparisons.
- 8a510275dd6b 18.0 landed
Add nbtree skip scan optimization.
- 92fe23d93aa3 18.0 landed
Improve nbtree array primitive scan scheduling.
- 9a2e2a285a14 18.0 landed
nbtree: Make BTMaxItemSize into object-like macro.
- 426ea611171d 18.0 landed
Show index search count in EXPLAIN ANALYZE, take 2.
- 0fbceae841cb 18.0 landed
Make parallel nbtree index scans use an LWLock.
- 67fc4c9fd7fa 18.0 landed
Show index search count in EXPLAIN ANALYZE.
- 5ead85fbc811 18.0 landed
Avoid nbtree parallel scan currPos confusion.
- b5ee4e52026b 18.0 cited
nbtree: Remove useless 'strat' local variable.
- b6558e4f837e 18.0 landed
Normalize nbtree truncated high key array behavior.
- 79fa7b3b1a44 18.0 landed
Refactor handling of nbtree array redundancies.
- b524974106ac 18.0 landed
Fix nbtree pgstats accounting with parallel scans.
- c00c54a9ac1e 18.0 landed
- fb4f5e58af97 17.0 landed
Avoid parallel nbtree index scan hangs with SAOPs.
- d8adfc18bebf 18.0 landed
- a24bffc021d9 17.0 landed
Show Parallel Bitmap Heap Scan worker stats in EXPLAIN ANALYZE
- 5a1e6df3b84c 18.0 cited
Enhance nbtree ScalarArrayOp execution.
- 5bf748b86bc6 17.0 cited
Skip checking of scan keys required for directional scan in B-tree
- e0b1ee17dc3a 17.0 cited
Instead of using a numberOfRequiredKeys count to distinguish required
- 7ccaf13a06b8 8.2.0 cited

On Tue, 1 Apr 2025 at 23:56, Matthias van de Meent
<boekewurm+postgres@gmail.com> wrote:
>
> On Tue, 1 Apr 2025 at 04:02, Peter Geoghegan <pg@bowt.ie> wrote:
> >
> > On Fri, Mar 28, 2025 at 5:59 PM Peter Geoghegan <pg@bowt.ie> wrote:
> > > Attached is v32, which has very few changes, but does add a new patch:
> > > a patch that adds skip-array-specific primitive index scan heuristics
> > > to _bt_advance_array_keys (this is
> > > v32-0003-Improve-skip-scan-primitive-scan-scheduling.patch).
> >
> > Attached is v33
>
> 0001:
>
> I just realised we never check whether skip keys' high/low_compare
> values generate valid quals, like what you'd see generated for WHERE a
> > 5 AND a < 3 AND b = 2;
>
> This causes a performance regression in the patched version:

Apparently it's not a regression, as we don't have this check in place
in the master branch. So, that's an optimization for PG19.

Sorry for the noise.

Kind regards,

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