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 1tZows-00DMDe-Rk for pgsql-admin@arkaria.postgresql.org; Mon, 20 Jan 2025 10:24:03 +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 1tZovt-000WoQ-AA for pgsql-admin@arkaria.postgresql.org; Mon, 20 Jan 2025 10:23:01 +0000 Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29]) by malur.postgresql.org with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1tZovs-000WoI-SH for pgsql-admin@lists.postgresql.org; Mon, 20 Jan 2025 10:23:01 +0000 Received: from mail-oi1-x22f.google.com ([2607:f8b0:4864:20::22f]) by magus.postgresql.org with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.96) (envelope-from ) id 1tZovq-000W4J-2O for pgsql-admin@lists.postgresql.org; Mon, 20 Jan 2025 10:23:01 +0000 Received: by mail-oi1-x22f.google.com with SMTP id 5614622812f47-3ebc07d3d0cso576771b6e.0 for ; Mon, 20 Jan 2025 02:22:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1737368577; x=1737973377; darn=lists.postgresql.org; h=to:subject:message-id:date:from:mime-version:from:to:cc:subject :date:message-id:reply-to; bh=9Gt7CuULO2NiZsTboM4FPNESxt4zUh9JIXtrWY9aX8c=; b=lpvrrrCkB4fdJXpnSppYskKZNodV81zqoYcR3DQ2/l6NL7tdkgoPVSSg1o/q9XykFr RrpN1rGh0gyX5Dj2E6nMAgVKXja8SnaGYrtxFOhnoT/94wXP5qlx6Z7smopw9TqICPTE k8vW01dvFSIizZbqE14ArQbb47309ogaS0TmSElfGMZnKwAMxWj9FOdK/g6VQY0XNwrB Ea1nhod7jdRxCwlzIpQqC2ABd8cbjm5niy2j28Fi6B0uv+dDF97KlfGbi+sM5kiD7L4z UuffnA1jvQ5Py2Bp5Vh7QbBh3vrOQAISAHXe30tL8UFBNb8cipgIyXaTYjYMZ6un5Fd4 4/4w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1737368577; x=1737973377; h=to:subject:message-id:date:from:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=9Gt7CuULO2NiZsTboM4FPNESxt4zUh9JIXtrWY9aX8c=; b=OMQVzFmy6wLVIgM1sWd2RDkhAhZmXz9XH8xtC8GQnuW6YsRHXdsQxUDI9wRDntejRe T2etEkmGj5bcqg14+qRQxAVH8POo43HTXgfFXdNHCsWIHSFwDnFYZru8T9VTOfYEAYLw 8sRfum/sHIAc9IxegSgyqH1iOSt5Oi1xoam9Z5KX4TAwXTlso/Ow+wrp8JKSnnGc3wuR EEGWu+oBu02i2OIeQSa6lZaYv2l+PHHnBUu/vMsSnZHhKwJ2PNq9hjIm95hIlTKSigEx st5wTNtjmStpjGTHK5vEqikKK+RHlzk1h2LObgRy/0mS9uHNw8lX6jyH+EunHZTSvzpE nxhA== X-Gm-Message-State: AOJu0YxdFFUMl9ec7koQjtZk1JZqN58gm8eZj6V8Bw4BCUBeIRd6hKcX 7tyEOcpdd1mTOzq4WUagBjxdrrxyYsa3W4iGlaP2wuGneaGm/5iJbx3WUWtFuv62YylMJeiCF5+ AF2wkKvLzevNESTSgbJ4K0nkwEyOWnUQ2 X-Gm-Gg: ASbGncvjLfHRxgNlytRMbmp4kCd2PdOfNF7lY6hQXHtc3SXwubEVDNuVyq9o1DaSaTy 9U81yYQUW6Mp/UR0M0AgqchUFxZcZxqPnANADV635DQ+Hvthavg== X-Google-Smtp-Source: AGHT+IFna6vhkErS4kA9NTNirOawg8I9Z5PDJaetym6458dzTgevGJwvwyxZGMMEV7vIkE9SQ754drJfrAEowpFirqQ= X-Received: by 2002:a05:6870:5706:b0:29e:3d1c:24cb with SMTP id 586e51a60fabf-2b1c0cddaa2mr2440009fac.11.1737368577281; Mon, 20 Jan 2025 02:22:57 -0800 (PST) MIME-Version: 1.0 From: Fabrice Chapuis Date: Mon, 20 Jan 2025 11:22:46 +0100 X-Gm-Features: AbW1kvYRDJ1CqWGBARjBMoT3cfc69M_hHF_YYO9uJDt8tyuhWVlcagaWa1TlBbA Message-ID: Subject: wal_compression To: pgsql-admin@lists.postgresql.org Content-Type: multipart/alternative; boundary="000000000000e499f9062c20a45f" List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Archived-At: Precedence: bulk --000000000000e499f9062c20a45f Content-Type: text/plain; charset="UTF-8" In Postgres 17 doc, for wal_compression parameter it's written: "Turning this parameter on can reduce the WAL volume without increasing the risk of unrecoverable data corruption" If wal_compression = on then when a full page is written in the wal, it will be compressed. What I do not understand is that the wal file keeps the same size 16Mb. What is the interest to activate wal_compression? Thanks in advance for explanation Fabrice --000000000000e499f9062c20a45f Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
In Postgres 17 d= oc, for wal_compression parameter it's written:
"Turning this parameter on can reduce the WA= L volume without increasing the risk of unrecoverable data corruption"=
If=C2=A0wal_compression=C2=A0=3D on then when a full page is written in the wal, it will be = compressed. What I do not understand is that the wal file keeps the same si= ze 16Mb. What is the interest to activate wal_compression?

= Thanks in advance for explanation

=
Fabrice
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