Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1npyyv-0001Kd-FN for pgsql-admin@arkaria.postgresql.org; Sat, 14 May 2022 21:07:21 +0000 Received: from localhost ([127.0.0.1] helo=malur.postgresql.org) by malur.postgresql.org with esmtp (Exim 4.92) (envelope-from ) id 1npyyt-0002my-7a for pgsql-admin@arkaria.postgresql.org; Sat, 14 May 2022 21:07:19 +0000 Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29]) by malur.postgresql.org with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1npyys-0002mp-RC for pgsql-admin@lists.postgresql.org; Sat, 14 May 2022 21:07:18 +0000 Received: from mail-ej1-x62f.google.com ([2a00:1450:4864:20::62f]) by magus.postgresql.org with esmtps (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1npyyq-0006Yt-Bh for pgsql-admin@lists.postgresql.org; Sat, 14 May 2022 21:07:18 +0000 Received: by mail-ej1-x62f.google.com with SMTP id g6so22158373ejw.1 for ; Sat, 14 May 2022 14:07:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=WyKmh5uFVmcvsHX/8DlMWUG8J+5gb3McPat5BCkSQt4=; b=PsYI2g2FWDw7onZhPPCNttjLZykTKdvGEq8pi/dgSYF0MNaK0mf3sBjHQdPgevk3qd 347EjCt4xgYlB4BAi6AiBVlCA/tDqPthpq4wbgUm2xO6Ndtc4uZt/bXdj+d2QzGZR0FW E4dKAzcmbCuzVzN0Euro4UifXbesC8Kyh1AS8RwjaP3y52c63oPmF5MTB1SaRv/5uGHR Y1GfZWkRWuFrwnQ2XeAHJ0EtulN9w7F5w5h75tYqBoZGNTRGvhemdVTmj7hf8y+GzpHY e6XTtWXWKPFcxROL3YmBUXE+y99Y2kAmmPEfg/09AsG7+Y3BvROnBexKoLpKgPEChE+G R5qQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=WyKmh5uFVmcvsHX/8DlMWUG8J+5gb3McPat5BCkSQt4=; b=S6BPHhkTNDBEt2tVUihmq6N4fRt7lwgrV/MQ1htjxIc9qPK+IZGEsAqDIN4gIv6InF djhyJxuOY8AmW7KvR7upiYSvlSztIZLQ84humSRKrJ61xZCB5iH3mKm3Awk1/DUazq3d sgoeX43ppfkwU8gfSVvggtn4jfpIZDsOtEXCrC86401iQkYV8MP7lgPcXIHzNGRC85b1 AoiKHaBM9XEt4dAjFVZbn8JQEMcY3B1WrCL4nrGxBboqeBJWmwfkOGeIxw7ln24ZiGGs d8jzXlAwKBhUX1KIeLKQzPTm8d1H1VsGjSFmPwR4CuuEdVCHFw3niFkOuNsPi90Wb2uv 7ChQ== X-Gm-Message-State: AOAM531zhT7Bx2s4lm+0MY59Oqa1OlYwndI2QMspKs0l8JqNeDod0jCO RksZnWqGDI/fx7dOwmJczWMpgufBKDG1t4LRZSmAj3rE4pk= X-Google-Smtp-Source: ABdhPJzgZ3qbJwjViepU4nsNynpUbzWGPRZ7PE65jYWIKLIa22ZXPUVHtrvK6IrW4euUSDLPjKo7ayyKguRibJ+MBms= X-Received: by 2002:a17:906:8301:b0:6e4:896d:59b1 with SMTP id j1-20020a170906830100b006e4896d59b1mr9102873ejx.396.1652562434160; Sat, 14 May 2022 14:07:14 -0700 (PDT) MIME-Version: 1.0 References: <001401d867cf$603ad830$20b08890$@msym.fr> <1019806.1652561174@sss.pgh.pa.us> In-Reply-To: <1019806.1652561174@sss.pgh.pa.us> From: "David G. Johnston" Date: Sat, 14 May 2022 14:06:56 -0700 Message-ID: Subject: Re: "clearing" a relation file ! To: Tom Lane Cc: Michel SALAIS , Pgsql-admin Content-Type: multipart/alternative; boundary="000000000000db79a505deff2cbc" List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Archived-At: Precedence: bulk --000000000000db79a505deff2cbc Content-Type: text/plain; charset="UTF-8" On Sat, May 14, 2022 at 1:46 PM Tom Lane wrote: > "Michel SALAIS" writes: > > \! dd if=/dev/zero of=$file_path bs=1024 count=100 > > The other problem with this specific test is that an all-zero > page is considered to be a valid state. You may consider that > a problem or not, but we're quite unlikely to change it, because > doing so would create false failure reports. See the mechanisms > around file extension. > > Should this detail be mentioned in the docs? https://www.postgresql.org/docs/current/checksums.html Namely (and not confirmed): "A failure mode that produces empty pages will not be detected by this mechanism during normal server operation, but the pg_checksums application will since all normal usage of empty pages is restricted to runtime transient state." David J. --000000000000db79a505deff2cbc Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Sat, May 14, 2022 at 1:46 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
"Michel SALAIS" <msalais@msym.fr> writes:
> \! dd if=3D/dev/zero of=3D$file_path bs=3D1024 count=3D100

The other problem with this specific test is that an all-zero
page is considered to be a valid state.=C2=A0 You may consider that
a problem or not, but we're quite unlikely to change it, because
doing so would create false failure reports.=C2=A0 See the mechanisms
around file extension.


Should this de= tail be mentioned in the docs?

https://www.postgresql.org/docs= /current/checksums.html

Namely (and not confirmed)= :

"A failure mode that produces empty pages will = not be detected by this mechanism during normal server operation, but the p= g_checksums application will since all normal usage of empty pages is restr= icted to runtime transient state."

David J.
=
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