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Date: Thu, 10 Oct 2024 22:47:00 +0800
From: Zhang Mingli <zmlpostgres@gmail.com>
To: Ba Jinsheng <bajinsheng@u.nus.edu>,
 "=?utf-8?Q?pgsql-bugs=40lists.postgresql.org?="
 <pgsql-bugs@lists.postgresql.org>, Tomas Vondra <tomas@vondra.me>
Message-ID: <3c7df680-97e6-4f20-ab27-65fb8282f95e@Spark>
In-Reply-To: <20f9671d-6f40-429b-a749-a2f53086e0dd@vondra.me>
References: 
 <SEZPR06MB64945FE5A48A367A8C0EE8FC8A782@SEZPR06MB6494.apcprd06.prod.outlook.com>
 <SEZPR06MB6494C5B80077EC08B21772888A782@SEZPR06MB6494.apcprd06.prod.outlook.com>
 <20f9671d-6f40-429b-a749-a2f53086e0dd@vondra.me>
Subject: Re: Question of Parallel Hash Join on TPC-H Benchmark
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Hi,


Zhang Mingli
www.hashdata.xyz
On Oct 10, 2024 at 22:41 +0800, Tomas Vondra <tomas=40vondra.me>, wrote:
>
> You can try setting parallel=5Fsetup=5Fcost and parallel=5Ftuple=5Fcost=
 to 0,
> and reducing min=5Fparallel=5F=7Btable,index=7D=5Fscan=5Fsize. That sho=
uld force a
> parallel plan, and you'll see if parallelism is helpful.
In addition to this, it seems you=E2=80=99r eager a parallel-aware HashJo=
in.
Check if=C2=A0=C2=A0enable=5Fparallel=5Fhash =3D on, an explain(verbose) =
will show related GUCs.

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<html xmlns=3D=22http://www.w3.org/1999/xhtml=22>
<head>
<title></title>
</head>
<body>
<div name=3D=22messageBodySection=22>
<div dir=3D=22auto=22>Hi,</div>
</div>
<div name=3D=22messageSignatureSection=22><br />
<div class=3D=22match=46ont=22>
<div dir=3D=22auto=22><br /></div>
Zhang Mingli
<div dir=3D=22auto=22><span style=3D=22color: var(--textColor); backgroun=
d-color: var(--backgroundColor);=22>www.hashdata.xyz</span><br /></div>
</div>
</div>
<div name=3D=22messageReplySection=22>
<div dir=3D=22auto=22>On Oct 10, 2024 at 22:41 +0800, Tomas Vondra &lt;to=
mas=40vondra.me&gt;, wrote:</div>
<blockquote style=3D=22border-left-color: rgb(26, 188, 156); margin: 5px;=
 padding-left: 10px; border-left-width: thin; border-left-style: solid;=22=
><br />
You can try setting parallel=5Fsetup=5Fcost and parallel=5Ftuple=5Fcost t=
o 0,<br />
and reducing min=5Fparallel=5F=7Btable,index=7D=5Fscan=5Fsize. That shoul=
d force a<br />
parallel plan, and you'll see if parallelism is helpful.</blockquote>
<div dir=3D=22auto=22>In addition to this, it seems you=E2=80=99r eager a=
 parallel-aware HashJoin.<br />
Check if&=23160;&=23160;enable=5Fparallel=5Fhash =3D on, an explain(verbo=
se) will show related GUCs.</div>
</div>
</body>
</html>

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