Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1stWGB-00H3g2-5q for pgsql-general@arkaria.postgresql.org; Wed, 25 Sep 2024 17:57:07 +0000 Received: from localhost ([127.0.0.1] helo=malur.postgresql.org) by malur.postgresql.org with esmtp (Exim 4.94.2) (envelope-from ) id 1stWGA-00C7Z5-Eo for pgsql-general@arkaria.postgresql.org; Wed, 25 Sep 2024 17:57:06 +0000 Received: from makus.postgresql.org ([2001:4800:3e1:1::229]) by malur.postgresql.org with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1stWGA-00C7Yw-3i for pgsql-general@lists.postgresql.org; Wed, 25 Sep 2024 17:57:06 +0000 Received: from mail-oi1-x22f.google.com ([2607:f8b0:4864:20::22f]) by makus.postgresql.org with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94.2) (envelope-from ) id 1stWG6-0011tQ-TD for pgsql-general@lists.postgresql.org; Wed, 25 Sep 2024 17:57:04 +0000 Received: by mail-oi1-x22f.google.com with SMTP id 5614622812f47-3e03981dad2so711161b6e.1 for ; Wed, 25 Sep 2024 10:57:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1727287022; x=1727891822; darn=lists.postgresql.org; h=to:subject:message-id:date:from:in-reply-to:references:mime-version :from:to:cc:subject:date:message-id:reply-to; bh=X8fFtKmfNpsGVx/h1wj+ssBUtLp+PdqBwJTW3I2ji3U=; b=cRsmVYH6wDIBG+hyooicVWxJ45su8W/AELMereH3pUNzwdb6k/gfDuXNc4uiYDlg6k MO9GCDi9aPQyKemw/Vrralf+GsxoS3OPv8/vBYcTewSP+cWphzLL1OhvHSKfu4DF62B+ D0SV0tVeudgIuKxsr7W9eR56I76o/Gj/+NHo2ty5W3EbHkiTJPko1WeYV39I9kH+Z1AC hSXPtzy1cQ4DTpKqnR45tUzH5/oqDqmYHdCnQQNhebYR2vjJHo3jSTWbKwQLWp8Mq8GL CF61+PStb/aV8Pdo1cJ+i/mKNomI8SkdpSbCQK5QfA/sMD3K1SvZg8J6zYRXvKca1X00 ADdw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1727287022; x=1727891822; h=to:subject:message-id:date:from:in-reply-to:references:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=X8fFtKmfNpsGVx/h1wj+ssBUtLp+PdqBwJTW3I2ji3U=; b=jPnPvCdQmGtR9/ET7Qp/JvyhtEpPymm3d0iqs1A0E51hpyizsJmwJYl3PoZF64dwGZ TUEXesPjR7w5Ar8zR2WPRRBuxHkUYfuMESyngPk3hqXTeM9EpCs+tBgFtTymjsumoC5E cO7Lh4y5Z9nSQswX37Jb7hMNdjty9uY4WhDmoiXSCnN+/jyyFDKph/LR/O/VqlezXanQ uCB8L6REsAt8NPHx12KBijK95eDp0Lm1qU13A2xY9/ks5xbshbDthtbH3aJlMt4rCb/z wUKumovdYmj4GrcHcmguvagskxNZNwy1scesM1b+AbF0Pm+9JV+H+IS6WLbq116Fho4R Tc9w== X-Gm-Message-State: AOJu0YysZRQXOGoSzD4HjqNBdcGGpyxyWM83vDWVd4IPv0M2BcHbP6Gd jDKoEBX8DD0WfLlwXO9RPECZVdaxfW3g0+Mmv4vUzDbvTRxgN/MR1uGi2VATe1N/ohHM3PB/o1I ePu++p+uzTeHTNR4yQW4cM9InC8T8zA== X-Google-Smtp-Source: AGHT+IG8rr0lqTxYuOJYHO9gLEBTd3argYHdVpQNRprz6Z0CMdS8H6ljQqPEOfUaVnn+w56iHbdPvdNKhfvaF6/EOO8= X-Received: by 2002:a05:6808:13c1:b0:3e0:45d3:ce28 with SMTP id 5614622812f47-3e2a332dbb1mr271220b6e.11.1727287021889; Wed, 25 Sep 2024 10:57:01 -0700 (PDT) MIME-Version: 1.0 References: <9CEBFAC7-4372-4FF0-8124-FFFE834B03C6@gmail.com> <3346993.1727188126@sss.pgh.pa.us> <28109.1727286817@sss.pgh.pa.us> In-Reply-To: <28109.1727286817@sss.pgh.pa.us> From: Ron Johnson Date: Wed, 25 Sep 2024 13:56:51 -0400 Message-ID: Subject: Re: Repeatable Read Isolation Level "transaction start time" To: "pgsql-generallists.postgresql.org" Content-Type: multipart/alternative; boundary="0000000000005d73210622f55902" List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Archived-At: Precedence: bulk --0000000000005d73210622f55902 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, Sep 25, 2024 at 1:53=E2=80=AFPM Tom Lane wrote: > Ron Johnson writes: > > But why does "SELECT 1;" need a snapshot? Heck, why does "SELECT > > ;" need a snapshot? > > 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. > Perfectly reasonable. --=20 Death to , and butter sauce. Don't boil me, I'm still alive. crustacean! --0000000000005d73210622f55902 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Wed, Sep 25, 2024 at 1:53=E2=80=AFPM T= om Lane <tgl@sss.pgh.pa.us> = wrote:
Ron Johnson <ronljohnsonjr@gmail.com> writes:
> But why does "SELECT 1;" need a snapshot?=C2=A0 Heck, why do= es "SELECT
> <immutable>;" need a snapshot?

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.=C2=A0 If it says SELECT, it gets a snapshot.
=C2=A0
Perfectly reasonable.

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