Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1VjBB8-0007GN-Vs for pgsql-hackers@arkaria.postgresql.org; Wed, 20 Nov 2013 17:03:03 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.80) (envelope-from ) id 1VjBB8-0000JR-ER for pgsql-hackers@arkaria.postgresql.org; Wed, 20 Nov 2013 17:03:02 +0000 Received: from makus.postgresql.org ([2001:4800:7903:4::125]) by malur.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1VjBB6-0000G7-0O for pgsql-hackers@postgresql.org; Wed, 20 Nov 2013 17:03:00 +0000 Received: from smtp-outbound-1.vmware.com ([208.91.2.12]) by makus.postgresql.org with esmtp (Exim 4.80) (envelope-from ) id 1VjBAu-0002Hy-C5 for pgsql-hackers@postgresql.org; Wed, 20 Nov 2013 17:02:58 +0000 Received: from sc9-mailhost1.vmware.com (sc9-mailhost1.vmware.com [10.113.161.71]) by smtp-outbound-1.vmware.com (Postfix) with ESMTP id 5AA95986A6; Wed, 20 Nov 2013 09:02:47 -0800 (PST) Received: from zcs-prod-ext-mta-1.vmware.com (zcs-prod-ext-mta-1.vmware.com [10.113.62.223]) by sc9-mailhost1.vmware.com (Postfix) with ESMTP id 56937180DC; Wed, 20 Nov 2013 09:02:47 -0800 (PST) Received: from zcs-prod-ext-mta-1.vmware.com (localhost.localdomain [127.0.0.1]) by zcs-prod-ext-mta-1.vmware.com (Postfix) with ESMTP id F1D69120033; Wed, 20 Nov 2013 09:02:51 -0800 (PST) Received: from [192.168.1.90] (zimbra-prod-ext-proxy-vip.vmware.com [10.113.63.87]) by zcs-prod-ext-mta-1.vmware.com (Postfix) with ESMTPSA; Wed, 20 Nov 2013 09:02:50 -0800 (PST) Message-ID: <528CEB34.7080702@vmware.com> Date: Wed, 20 Nov 2013 19:02:44 +0200 From: Heikki Linnakangas Organization: VMware User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20131005 Icedove/17.0.9 MIME-Version: 1.0 To: Alvaro Herrera CC: Alexander Korotkov , Tomas Vondra , pgsql-hackers Subject: Re: GIN improvements part 1: additional information References: <524E7C3B.7060402@vmware.com> <5250A7A1.2010701@fuzzy.cz> <52546434.1000303@vmware.com> <52548F79.6030407@fuzzy.cz> <52569635.5090808@vmware.com> <527A03AF.9010501@vmware.com> <20131106153604.GM5809@eldon.alvh.no-ip.org> In-Reply-To: <20131106153604.GM5809@eldon.alvh.no-ip.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Pg-Spam-Score: -7.4 (-------) List-Archive: List-Help: List-ID: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: X-Mailing-List: pgsql-hackers Precedence: bulk Sender: pgsql-hackers-owner@postgresql.org On 06.11.2013 17:36, Alvaro Herrera wrote: > Just for my own illumination, can someone explain this bit? > > + If a posting list is too large to store in-line in a key entry, a posting tree > + is created. A posting tree is a B-tree structure, where the ItemPointer is > + used as the key. At the leaf-level, item pointers are stored compressed, in > + "varbyte encoding". > > I think the first ItemPointer mentioned (the key) refers to a TID > pointing to the index, and "item pointers stored compressed" refers to > the TIDs pointing to the heap (the data). Is that correct? No, they both refer to TIDs pointing to the heap. > I'm also interested in the "FIXME explain varbyte encoding" explanation > currently missing, if somebody can write it down ... Alexander's latest version filled in that explanation (haven't read it myself yet) - Heikki -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers