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From: Steve Midgley <science@misuse.org>
Date: Sun, 10 Apr 2022 09:03:04 -0700
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 <CAJexoS+mG=4AKfjAb0+i5DKhHB_8qSxZz3g5Ny+MZirGBj7Vdg@mail.gmail.com>
Subject: Re: How best to do parallel query given tens of thousands of
 iteration of a loop of recursive queries?
To: Shaozhong SHI <shishaozhong@gmail.com>
Cc: pgsql-sql <pgsql-sql@lists.postgresql.org>
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On Sun, Apr 10, 2022, 6:50 AM Shaozhong SHI <shishaozhong@gmail.com> wrote:

> There is a plpgsql script that have a loop to carry out the same recursive
> queries.
>
> The estimation of iteration is in the order of tens of thousands.
>
> What is the best way of making using parallel query strategy.
>
> Any examples?
>

Can you provide some sample ddl, data and sql to illustrate your question?

You mention in one place "iteration" and "parallel" but in another you
mention recursion.. Recursion (by definition?) involves pushing state data
forward into each successive iteration.. Therefore you can't run recursion
in parallel.

If you can provide examples maybe we can see which if parallelism is a
possibility..

Steve

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<div dir=3D"auto"><br><br><div class=3D"gmail_quote" dir=3D"auto"><div dir=
=3D"ltr" class=3D"gmail_attr">On Sun, Apr 10, 2022, 6:50 AM Shaozhong SHI &=
lt;<a href=3D"mailto:shishaozhong@gmail.com">shishaozhong@gmail.com</a>&gt;=
 wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8=
ex;border-left:1px #ccc solid;padding-left:1ex"><div dir=3D"ltr">There is a=
 plpgsql script that have a loop to carry out the same recursive queries.<d=
iv><br></div><div>The estimation of iteration is in the order of tens of th=
ousands.</div><div><br></div><div>What is the best way of making using para=
llel query strategy.</div><div><br></div><div>Any examples?</div></div></bl=
ockquote></div><div dir=3D"auto"><br></div><div dir=3D"auto">Can you provid=
e some sample ddl, data and sql to illustrate your question?=C2=A0</div><di=
v dir=3D"auto"><br></div><div dir=3D"auto">You mention in one place &quot;i=
teration&quot; and &quot;parallel&quot; but in another you mention recursio=
n.. Recursion (by definition?) involves pushing state data forward into eac=
h successive iteration.. Therefore you can&#39;t run recursion in parallel.=
=C2=A0</div><div dir=3D"auto"><br></div><div dir=3D"auto">If you can provid=
e examples maybe we can see which if parallelism is a possibility..=C2=A0</=
div><div dir=3D"auto"><br></div><div dir=3D"auto">Steve=C2=A0</div><div cla=
ss=3D"gmail_quote" dir=3D"auto"></div></div>

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