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From: Amit Langote <amitlangote09@gmail.com>
Date: Tue, 30 Sep 2025 22:35:52 +0900
Message-ID: 
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Subject: Re: Batching in executor
To: Tomas Vondra <tomas@vondra.me>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
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On Tue, Sep 30, 2025 at 11:11=E2=80=AFAM Amit Langote <amitlangote09@gmail.=
com> wrote:
> Hi Tomas,
>
> Thanks a lot for your comments and benchmarking.
>
> I plan to reply to your detailed comments and benchmark results

For now, I reran a few benchmarks with the master branch as an
explicit baseline, since Tomas reported possible regressions with
executor_batching=3Doff. I can reproduce that on my side:

5 aggregates, no where:
select avg(a), avg(b), avg(c), avg(d), avg(e) from bar;

parallel_workers=3D0, jit=3Doff
Rows    master    batching off    batching on    master vs off    master vs=
 on
1M      47.118    48.545          39.531         +3.0%            -16.1%
2M      95.098    97.241          80.189         +2.3%            -15.7%
3M      141.821   148.540         122.005        +4.7%            -14.0%
4M      188.969   197.056         163.779        +4.3%            -13.3%
5M      240.113   245.902         213.645        +2.4%            -11.0%
10M     556.738   564.120         486.359        +1.3%            -12.6%

parallel_workers=3D2, jit=3Don
Rows    master    batching off    batching on    master vs off    master vs=
 on
1M      21.147    22.278          20.737         +5.3%            -1.9%
2M      40.319    41.509          37.851         +3.0%            -6.1%
3M      61.582    63.026          55.927         +2.3%            -9.2%
4M      96.363    95.245          78.494         -1.2%            -18.5%
5M      117.226   117.649         97.968         +0.4%            -16.4%
10M     245.503   246.896         196.335        +0.6%            -20.0%

1 aggregate, no where:
select count(*) from bar;

parallel_workers=3D0, jit=3Doff
Rows    master    batching off    batching on    master vs off    master vs=
 on
1M      17.071    20.135          6.698          +17.9%           -60.8%
2M      36.905    41.522          15.188         +12.5%           -58.9%
3M      56.094    63.110          23.485         +12.5%           -58.1%
4M      74.299    83.912          32.950         +12.9%           -55.7%
5M      94.229    108.621         41.338         +15.2%           -56.1%
10M     234.425   261.490         117.833        +11.6%           -49.7%

parallel_workers=3D2, jit=3Don
Rows    master    batching off    batching on    master vs off    master vs=
 on
1M      8.820     9.832           5.324          +11.5%           -39.6%
2M      16.368    18.001          9.526          +10.0%           -41.8%
3M      24.810    28.193          14.482         +13.6%           -41.6%
4M      34.369    35.741          23.212         +4.0%            -32.5%
5M      41.595    45.103          27.918         +8.4%            -32.9%
10M     99.494    112.226         94.081         +12.8%           -5.4%

The regression is more noticeable in the single aggregate case, where
more time is spent in scanning.

Looking into it.

--=20
Thanks, Amit Langote