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From: Ron Johnson <ronljohnsonjr@gmail.com>
Date: Wed, 25 Sep 2024 16:36:20 -0400
Message-ID: <CANzqJaAAQFD_JvK=ChmfdGCRNP0G5gMtVBgF52bZiFjQxH8N_Q@mail.gmail.com>
Subject: Re: Repeatable Read Isolation Level "transaction start time"
To: "pgsql-generallists.postgresql.org" <pgsql-general@lists.postgresql.org>
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On Wed, Sep 25, 2024 at 4:23=E2=80=AFPM Greg Sabino Mullane <htamfids@gmail=
.com>
wrote:

> On Wed, Sep 25, 2024 at 1:53=E2=80=AFPM Tom Lane <tgl@sss.pgh.pa.us> wrot=
e:
>
>> Because we're not going to analyze the statement in the amount of depth
>> needed to make that distinction before we crank up the
>> transactional machinery.  If it says SELECT, it gets a snapshot.
>>
>
> Ok, thanks. So to the original poster's point, perhaps the path with the
> least side effects / best Principle of Least Surprise (POLS) support is t=
o
> start the transaction, and immediately call a "SELECT 1;" or perhaps bett=
er
> still, a 'SELECT timeofday();'
>

Since transactions should be "as short as possible, without being too
short", how much time is there between when you run "BEGIN;" and the first
"work statement"?

--=20
Death to <Redacted>, and butter sauce.
Don't boil me, I'm still alive.
<Redacted> crustacean!

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<div dir=3D"ltr"><div dir=3D"ltr">On Wed, Sep 25, 2024 at 4:23=E2=80=AFPM G=
reg Sabino Mullane &lt;<a href=3D"mailto:htamfids@gmail.com">htamfids@gmail=
.com</a>&gt; wrote:<br></div><div class=3D"gmail_quote"><blockquote class=
=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rg=
b(204,204,204);padding-left:1ex"><div dir=3D"ltr"><div dir=3D"ltr">On Wed, =
Sep 25, 2024 at 1:53=E2=80=AFPM Tom Lane &lt;<a href=3D"mailto:tgl@sss.pgh.=
pa.us" target=3D"_blank">tgl@sss.pgh.pa.us</a>&gt; wrote:<br></div><div cla=
ss=3D"gmail_quote"><blockquote class=3D"gmail_quote" style=3D"margin:0px 0p=
x 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Becaus=
e we&#39;re not going to analyze the statement in the amount of depth neede=
d to make that distinction before we crank up the<br>
transactional machinery.=C2=A0 If it says SELECT, it gets a snapshot.<br></=
blockquote><div><br></div><div>Ok, thanks. So to the original poster&#39;s =
point, perhaps the path with the least side effects / best Principle of Lea=
st Surprise (POLS) support is to start the transaction, and immediately cal=
l a &quot;SELECT 1;&quot; or perhaps better still, a &#39;SELECT timeofday(=
);&#39;</div></div></div></blockquote><div>=C2=A0</div><div>Since transacti=
ons should be &quot;as short as possible, without being too short&quot;, ho=
w much time is there between when you run &quot;BEGIN;&quot; and the first =
&quot;work statement&quot;?</div><div><br></div></div><span class=3D"gmail_=
signature_prefix">-- </span><br><div dir=3D"ltr" class=3D"gmail_signature">=
<div dir=3D"ltr">Death to &lt;Redacted&gt;, and butter sauce.<div>Don&#39;t=
 boil me, I&#39;m still alive.<br><div><div>&lt;Redacted&gt; crustacean!</d=
iv></div></div></div></div></div>

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