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From: Ron Johnson <ronljohnsonjr@gmail.com>
Date: Wed, 25 Sep 2024 17:16:19 -0400
Message-ID: <CANzqJaCn2ueCeoiH04ipGRKXQzfaaT+kE_GU7EoJ62bVEh8OsQ@mail.gmail.com>
Subject: Re: Repeatable Read Isolation Level "transaction start time"
To: pgsql-general <pgsql-general@postgresql.org>
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On Wed, Sep 25, 2024 at 4:50=E2=80=AFPM Greg Sabino Mullane <htamfids@gmail=
.com>
wrote:

> Since transactions should be "as short as possible, without being too
>>> short", how much time is there between when you run "BEGIN;" and the fi=
rst
>>> "work statement"?
>>>
>>
> I don't know that it really matters. For something automated, it would be
> a few milliseconds.
>

That's what I'm thinking, too.  It might cause a problem if you're typing
transaction commands in between drinking coffee and poking around other
PgAdmin tabs, but that's *your* fault, not PG's fault.


> Either way, I'm sure most people/apps already think of the initial 'BEGIN
> ...' as the start of the transaction, and act accordingly.
>
> Maybe long-term something like
>
> BEGIN   ISOLATION MODE REPEATABLE READ   SNAPSHOT NOW;
>

Without the "NOW", that's essentially the command used by the legacy rdbms
which I used to work on.

I'm trying to remember, though, if "SET TRANSACTION READ WRITE RESERVING
foo FOR <isolation level>;" (it's syntax for beginning a transaction)
started the transaction, or waited until an "action" statement.  Been too
long.

--=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 4:50=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 class=3D"gmail_quote=
"><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;borde=
r-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir=3D"ltr"><div c=
lass=3D"gmail_quote"><blockquote class=3D"gmail_quote" style=3D"margin:0px =
0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div=
 dir=3D"ltr"><div class=3D"gmail_quote">Since transactions should be &quot;=
as short as possible, without being too short&quot;, how much time is there=
 between when you run &quot;BEGIN;&quot; and the first &quot;work statement=
&quot;?</div></div></blockquote></div></div></blockquote><div><br></div><di=
v>I don&#39;t know that it really matters. For something automated, it woul=
d be a few milliseconds.</div></div></div></blockquote><div><br></div><div>=
That&#39;s what I&#39;m thinking, too.=C2=A0 It might cause a problem if yo=
u&#39;re typing transaction commands in between=C2=A0drinking coffee and po=
king around other PgAdmin tabs, but that&#39;s <i>your</i>=C2=A0fault, not =
PG&#39;s fault.</div><div>=C2=A0</div><blockquote class=3D"gmail_quote" sty=
le=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);paddi=
ng-left:1ex"><div dir=3D"ltr"><div class=3D"gmail_quote"><div> Either way, =
I&#39;m sure most people/apps already think of the initial &#39;BEGIN ...&#=
39; as the=C2=A0start of the transaction, and act accordingly.</div><div><b=
r></div><div>Maybe long-term something like</div><div><br></div><div>BEGIN=
=C2=A0 =C2=A0ISOLATION MODE REPEATABLE READ=C2=A0 =C2=A0SNAPSHOT NOW;</div>=
</div></div></blockquote><div><br></div><div>Without the &quot;NOW&quot;, t=
hat&#39;s essentially the command used by the legacy rdbms which I used to =
work on.</div></div><div><br></div><div>I&#39;m trying to remember, though,=
 if &quot;SET TRANSACTION READ WRITE RESERVING foo FOR &lt;isolation level&=
gt;;&quot; (it&#39;s syntax for beginning a transaction) started the transa=
ction, or waited until an &quot;action&quot; statement.=C2=A0 Been too long=
.</div><div><br></div><span class=3D"gmail_signature_prefix">-- </span><br>=
<div dir=3D"ltr" class=3D"gmail_signature"><div dir=3D"ltr">Death to &lt;Re=
dacted&gt;, and butter sauce.<div>Don&#39;t boil me, I&#39;m still alive.<b=
r><div><div>&lt;Redacted&gt; crustacean!</div></div></div></div></div></div=
>

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