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 1mzJhA-00021A-8u for pgsql-hackers@arkaria.postgresql.org; Mon, 20 Dec 2021 14:31:20 +0000 Received: from localhost ([127.0.0.1] helo=malur.postgresql.org) by malur.postgresql.org with esmtp (Exim 4.92) (envelope-from ) id 1mzJh9-0002tU-5J for pgsql-hackers@arkaria.postgresql.org; Mon, 20 Dec 2021 14:31:19 +0000 Received: from makus.postgresql.org ([2001:4800:3e1:1::229]) by malur.postgresql.org with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1mzJh8-0002tL-RJ for pgsql-hackers@lists.postgresql.org; Mon, 20 Dec 2021 14:31:18 +0000 Received: from out5-smtp.messagingengine.com ([66.111.4.29]) by makus.postgresql.org with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1mzJh6-0003JO-2s for pgsql-hackers@lists.postgresql.org; Mon, 20 Dec 2021 14:31:17 +0000 Received: from compute5.internal (compute5.nyi.internal [10.202.2.45]) by mailout.nyi.internal (Postfix) with ESMTP id 9AD2E5C0135; Mon, 20 Dec 2021 09:31:14 -0500 (EST) Received: from mailfrontend1 ([10.202.2.162]) by compute5.internal (MEProxy); Mon, 20 Dec 2021 09:31:14 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:content-transfer-encoding:content-type :date:from:in-reply-to:message-id:mime-version:references :subject:to:x-me-proxy:x-me-proxy:x-me-sender:x-me-sender :x-sasl-enc; s=fm1; bh=uQgq7hvTMgds5INHC/kinQgd9ZVm+zUe9qZugnl3s Og=; b=nUjlwpvbqjLLVCuSvJlWxE+N+fv5XjqtOfd7KexYb21WfjKiJyZM9GElZ GfalAXbZM0ULn5gu6qjnedkpQ/cSAOlIVvKR2V4gHUR1a4hmLKGoickCTXfWQUY0 FWb83ScIlxwXQRTQjxrjFPOwYAbA5D8xt0eAFq41BUbIoRISK7cnpaglLi/0ORvl su09M5D40gwTeeZGu+jCwnbYYEkNFt//1Ad0OE3jAcS4lfpiyzJTV6WMJZUCjLV4 ie6pS9Ns2/bVmDovCRoSVpD7h1xsV6thxq8N0MFWaKmQ9CXccigj24ij7WBqsLCh u/qXPGMh8DrFyqggnSDi+slRqWhww== X-ME-Sender: X-ME-Received: X-ME-Proxy-Cause: gggruggvucftvghtrhhoucdtuddrgedvuddruddtvddgieehucetufdoteggodetrfdotf fvucfrrhhofhhilhgvmecuhfgrshhtofgrihhlpdfqfgfvpdfurfetoffkrfgpnffqhgen uceurghilhhouhhtmecufedttdenucesvcftvggtihhpihgvnhhtshculddquddttddmne cujfgurhepkfffgggfuffvfhfhjggtgfesthejredttdefjeenucfhrhhomheprfgvthgv rhcugfhishgvnhhtrhgruhhtuceophgvthgvrhdrvghishgvnhhtrhgruhhtsegvnhhtvg hrphhrihhsvggusgdrtghomheqnecuggftrfgrthhtvghrnhepfeejgeehteeuhfevvedu leeufedtjeetiefftedvudfhtdeifefgueettdevgefgnecuvehluhhsthgvrhfuihiivg eptdenucfrrghrrghmpehmrghilhhfrhhomhepphgvthgvrhdrvghishgvnhhtrhgruhht segvnhhtvghrphhrihhsvggusgdrtghomh X-ME-Proxy: Received: by mail.messagingengine.com (Postfix) with ESMTPA; Mon, 20 Dec 2021 09:31:12 -0500 (EST) Message-ID: Date: Mon, 20 Dec 2021 15:31:11 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.3.2 Subject: Re: sequences vs. synchronous replication Content-Language: en-US To: Tomas Vondra , Tom Lane Cc: PostgreSQL Hackers References: <712cad46-a9c8-1389-aef8-faf0203c9be9@enterprisedb.com> <1452362.1639803168@sss.pgh.pa.us> <38a6a779-ee8d-de3c-fbd7-709285be88fa@enterprisedb.com> <7869761b-fdc7-6f7d-dc95-9ba8315a8ecf@enterprisedb.com> <1637476.1639862832@sss.pgh.pa.us> <8e24a470-b092-3c9f-0614-acd9df3f724f@enterprisedb.com> From: Peter Eisentraut In-Reply-To: <8e24a470-b092-3c9f-0614-acd9df3f724f@enterprisedb.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Archived-At: Precedence: bulk On 18.12.21 22:48, Tomas Vondra wrote: > What do you mean by "not caching unused sequence numbers"? Reducing > SEQ_LOG_VALS to 1, i.e. WAL-logging every sequence increment? > > That'd work, but I wonder how significant the impact will be. It'd bet > it hurts the patch adding logical decoding of sequences quite a bit. It might be worth testing. This behavior is ancient and has never really been scrutinized since it was added.