Re: Repeatable Read Isolation Level "transaction start time"

From: Ron Johnson <ronljohnsonjr(at)gmail(dot)com>
To: pgsql-general <pgsql-general(at)postgresql(dot)org>
Subject: Re: Repeatable Read Isolation Level "transaction start time"
Date: 2024-09-25 21:16:19
Message-ID: CANzqJaCn2ueCeoiH04ipGRKXQzfaaT+kE_GU7EoJ62bVEh8OsQ@mail.gmail.com
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On Wed, Sep 25, 2024 at 4:50 PM Greg Sabino Mullane <htamfids(at)gmail(dot)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 first
>>> "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.

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

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