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[86.49.228.162]) by smtp.gmail.com with ESMTPSA id h12-20020a5d688c000000b002b9b9445149sm7633262wru.54.2023.02.05.17.51.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 05 Feb 2023 17:51:28 -0800 (PST) Message-ID: <0f54129f-255d-2d8f-94a0-d18b6f388745@enterprisedb.com> Date: Mon, 6 Feb 2023 02:51:27 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: pglz compression performance, take two Content-Language: en-US To: Andrey Borodin Cc: Ian Lawrence Barwick , Andrey Borodin , Mark Dilger , Justin Pryzby , pgsql-hackers@postgresql.org References: <25991595-1848-4178-AA57-872B10309DA2@yandex-team.ru> <20201230043930.GG25152@telsasoft.com> <20210122024811.GE27167@telsasoft.com> <88C049C6-1B86-4EF7-940D-585B07FEB81B@yandex-team.ru> <90649B7F-EF71-40F7-93D0-1029AD0D90F3@enterprisedb.com> <84aa2da0-004d-c8f8-48c8-aa2861d1ff73@enterprisedb.com> <120DD821-48F4-446C-865A-093E560A2143@yandex-team.ru> From: Tomas Vondra In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CLOUD-SEC-AV-Info: enterprisedb,google_mail,monitor X-CLOUD-SEC-AV-Sent: true X-Gm-Spam: 0 X-Gm-Phishy: 0 List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Archived-At: Precedence: bulk On 2/5/23 19:36, Andrey Borodin wrote: > On Fri, Jan 6, 2023 at 10:02 PM Andrey Borodin wrote: >> >> Hello! Please find attached v8. > > I got some interesting feedback from some patch users. > There was an oversight that frequently yielded results that are 1,2 or > 3 bytes longer than expected. > Looking closer I found that the correctness of the last 3-byte tail is > checked in two places. PFA fix for this. Previously compressed data > was correct, however in some cases few bytes longer than the result of > current pglz implementation. > Thanks. What were the consequences of the issue? Lower compression ratio, or did we then fail to decompress the data (or would current pglz implementation fail to decompress it)? regards -- Tomas Vondra EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company