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[84.123.234.224]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-441b2af306bsm59077315e9.21.2025.05.01.06.37.52 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 01 May 2025 06:37:53 -0700 (PDT) Message-ID: <8e9f46ce-e087-4dd5-b0c2-4459170da11f@gmail.com> Date: Thu, 1 May 2025 15:37:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Add estimated hit ratio to Memoize in EXPLAIN to explain cost adjustment To: Ilia Evdokimov , David Rowley Cc: Robert Haas , Tom Lane , Lukas Fittl , Daniel Gustafsson , PostgreSQL Hackers , Nikolay Samokhvalov References: <3ba16aa7-3cb2-4289-b773-522ae2f03a77@tantorlabs.com> <81ef0f5a-b6a1-4417-ae3a-2bae9b8d419e@gmail.com> <67b5c84a-dedd-4103-af7e-0117046102fe@tantorlabs.com> <580fe72c-85be-45a8-9e00-6b5417690557@tantorlabs.com> <3ea66a50-e4b0-4f20-ae0c-4d9cbaf81cfb@tantorlabs.com> <0e8dc4fa-3655-4e9f-9424-9b32a15e6acd@tantorlabs.com> <7e995158-157e-4ec6-a7c8-266c1a6f7b43@tantorlabs.com> <06840539-e321-4930-9f89-cfc783c5b80a@tantorlabs.com> <15e0422a-31ec-4e82-b0cf-0839f636b185@tantorlabs.com> Content-Language: en-AU From: Andrei Lepikhov In-Reply-To: <15e0422a-31ec-4e82-b0cf-0839f636b185@tantorlabs.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Archived-At: Precedence: bulk On 5/1/25 14:22, Ilia Evdokimov wrote: >     Estimated Hit Percent: 50.00 > > Any suggestions? I still think that two meaningful digits are enough for an EXPLAIN. We usually need to estimate the tuple set's size, not a precise number of tuples or groups. And definitely, not an arbitrarily chosen two digits after the point. So, IMO, good examples may look like the following: 50%, 5.0%, 0.00051%. -- regards, Andrei Lepikhov