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From: "David G. Johnston" <david.g.johnston@gmail.com>
Date: Sun, 30 Mar 2025 22:10:54 -0700
Message-ID: <CAKFQuwYCj-gXZuyrwpP-jycbgH2_HmEsNWvJNDqr0WT2fEp8_A@mail.gmail.com>
Subject: Re: SQL Server's WITH (NOLOCK) equivalent in PostgreSQL?
To: =?UTF-8?B?7J207ZiE7KeE?= <jemie9812@gmail.com>
Cc: "pgsql-general@lists.postgresql.org" <pgsql-general@lists.postgresql.org>
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On Sunday, March 30, 2025, =EC=9D=B4=ED=98=84=EC=A7=84 <jemie9812@gmail.com=
> wrote:

>
> Since PostgreSQL uses MVCC, I'm wondering what the best practice is for
> non-blocking reads,
> and whether there's an equivalent to dirty reads or READ UNCOMMITTED.
>

https://www.postgresql.org/docs/current/transaction-iso.html

We are unable to implement read uncommitted because of our choice to
implement MVCC.  There is no equivalent because the fundamental operating
decisions doesn=E2=80=99t allow for one.

If you don=E2=80=99t pre-suppose the solution of dirty reads and instead su=
pply a
use case and desired constraints maybe an alternative approach for that use
case could be suggested.

David J.

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On Sunday, March 30, 2025, =EC=9D=B4=ED=98=84=EC=A7=84 &lt;<a href=3D"mailt=
o:jemie9812@gmail.com">jemie9812@gmail.com</a>&gt; wrote:<br><blockquote cl=
ass=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;p=
adding-left:1ex"><div dir=3D"ltr"><br></div><div dir=3D"ltr">Since PostgreS=
QL uses MVCC, I&#39;m wondering what the best practice is for non-blocking =
reads, <br>and whether there&#39;s an equivalent to dirty reads or READ UNC=
OMMITTED.<br></div></blockquote><div><br></div><div><a href=3D"https://www.=
postgresql.org/docs/current/transaction-iso.html">https://www.postgresql.or=
g/docs/current/transaction-iso.html</a></div><div><br></div><div>We are una=
ble to implement read uncommitted because of our choice to implement MVCC.=
=C2=A0 There is no equivalent because the fundamental operating decisions d=
oesn=E2=80=99t allow for one.</div><div><br></div><div>If you don=E2=80=99t=
 pre-suppose the solution of dirty reads and instead supply a use case and =
desired constraints maybe an alternative approach for that use case could b=
e suggested.</div><div><br></div><div>David J.</div><div><br></div>

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