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 1klc04-0003TD-6r for pgsql-docs@arkaria.postgresql.org; Sat, 05 Dec 2020 18:09:40 +0000 Received: from localhost ([127.0.0.1] helo=malur.postgresql.org) by malur.postgresql.org with esmtp (Exim 4.92) (envelope-from ) id 1klc02-0007aK-Le for pgsql-docs@arkaria.postgresql.org; Sat, 05 Dec 2020 18:09:38 +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 1klc02-0007aC-Gf for pgsql-docs@lists.postgresql.org; Sat, 05 Dec 2020 18:09:38 +0000 Received: from sss.pgh.pa.us ([66.207.139.130]) by makus.postgresql.org with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1klc00-0000ss-CB for pgsql-docs@lists.postgresql.org; Sat, 05 Dec 2020 18:09:37 +0000 Received: from sss1.sss.pgh.pa.us (localhost [127.0.0.1]) by sss.pgh.pa.us (8.15.2/8.15.2) with ESMTP id 0B5I9YEF2303585; Sat, 5 Dec 2020 13:09:34 -0500 From: Tom Lane To: hus.mhd@gmail.com cc: pgsql-docs@lists.postgresql.org Subject: Re: TOAST pointer size In-reply-to: <160712558528.686.9567660182316195384@wrigleys.postgresql.org> References: <160712558528.686.9567660182316195384@wrigleys.postgresql.org> Comments: In-reply-to PG Doc comments form message dated "Fri, 04 Dec 2020 23:46:25 +0000" MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <2303583.1607191774.1@sss.pgh.pa.us> Content-Transfer-Encoding: quoted-printable Date: Sat, 05 Dec 2020 13:09:34 -0500 Message-ID: <2303584.1607191774@sss.pgh.pa.us> List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Precedence: bulk PG Doc comments form writes: > It would be nice to add a break-down of why the TOAST Pointer size is 18 > bytes Use the source, Luke. The useful pointer data is indeed 16 bytes: https://git.postgresql.org/gitweb/?p=3Dpostgresql.git;a=3Dblob;f=3Dsrc/inc= lude/postgres.h;h=3Dc48f47e930ad05d3ae2e24b0c0c85662cd058a7b;hb=3DHEAD#l67 but there's varlena tag overhead: https://git.postgresql.org/gitweb/?p=3Dpostgresql.git;a=3Dblob;f=3Dsrc/inc= lude/postgres.h;h=3Dc48f47e930ad05d3ae2e24b0c0c85662cd058a7b;hb=3DHEAD#l15= 9 This doesn't seem like appropriate detail for the user docs. regards, tom lane