public inbox for [email protected]
help / color / mirror / Atom feedFrom: Peter J. Holzer <[email protected]>
To: [email protected]
Subject: Re: Repeatable Read Isolation Level "transaction start time"
Date: Wed, 25 Sep 2024 23:55:54 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
<[email protected]>
<CAKAnmmLt2ezcf7-LgJkO_oeqK+Ei+XB6F3pHk2mnyadRq3corQ@mail.gmail.com>
<[email protected]>
<CANzqJaBjwtzLg_bZHkokUJbtA8gy6RpHjirfdBH9OJGfn5=tmw@mail.gmail.com>
<[email protected]>
<CAKAnmmLDpwgqu071t_Q7Fq349dYAgQim1x46U1DCAiiTcUmU2A@mail.gmail.com>
<CANzqJaAAQFD_JvK=ChmfdGCRNP0G5gMtVBgF52bZiFjQxH8N_Q@mail.gmail.com>
<CAKAnmmL05Lt89EOnMW111qdUOau+dYG7u8ff5o+ckKKohnNwGg@mail.gmail.com>
<[email protected]>
On 2024-09-25 13:53:30 -0700, Christophe Pettus wrote:
> > On Sep 25, 2024, at 13:49, Greg Sabino Mullane <[email protected]> wrote:
> > BEGIN ISOLATION MODE REPEATABLE READ SNAPSHOT NOW;
>
> This might well be a failure of imagination on my part, but when would
> it pragmatically matter that the snapshot is taken at the first
> statement as opposed to at BEGIN?
It may make a difference if you're comparing timestamps.
For example, if you're using isolation level REPEATABLE READ and
(mistakenly) assume that the snapshot is taken at BEGIN, you would
expect any transaction_timestamp() written by a different transaction
and readable by this transaction to be earlier than the
transaction_timestamp() of this transaction.
But that's wrong because the other transaction could have happened
entirely in the time between your BEGIN and the statement which actually
triggers the snapshot.
hp
--
_ | Peter J. Holzer | Story must make more sense than reality.
|_|_) | |
| | | [email protected] | -- Charles Stross, "Creative writing
__/ | http://www.hjp.at/ | challenge!"
Attachments:
[application/pgp-signature] signature.asc (833B, 2-signature.asc)
download
view thread (11+ messages)
reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: [email protected]
Cc: [email protected], [email protected]
Subject: Re: Repeatable Read Isolation Level "transaction start time"
In-Reply-To: <[email protected]>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox