Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1sF8D4-007H2k-7A for pgsql-bugs@arkaria.postgresql.org; Thu, 06 Jun 2024 08:10:59 +0000 Received: from localhost ([127.0.0.1] helo=malur.postgresql.org) by malur.postgresql.org with esmtp (Exim 4.94.2) (envelope-from ) id 1sF8D4-00GKpb-4z for pgsql-bugs@arkaria.postgresql.org; Thu, 06 Jun 2024 08:10:58 +0000 Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29]) by malur.postgresql.org with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1sF8D3-00GKpJ-SP for pgsql-bugs@lists.postgresql.org; Thu, 06 Jun 2024 08:10:57 +0000 Received: from mail-ed1-x531.google.com ([2a00:1450:4864:20::531]) by magus.postgresql.org with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94.2) (envelope-from ) id 1sF8D1-000GJS-Gq for pgsql-bugs@lists.postgresql.org; Thu, 06 Jun 2024 08:10:57 +0000 Received: by mail-ed1-x531.google.com with SMTP id 4fb4d7f45d1cf-57a4d7ba501so633851a12.2 for ; Thu, 06 Jun 2024 01:10:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cybertec-at.20230601.gappssmtp.com; s=20230601; t=1717661454; x=1718266254; darn=lists.postgresql.org; h=mime-version:user-agent:content-transfer-encoding:autocrypt :references:in-reply-to:date:cc:to:from:subject:message-id:from:to :cc:subject:date:message-id:reply-to; bh=OiLKUW2+2tNN+p7QJ6i97yhN4aM0YoAGrvjixVkAQhE=; b=onccxrpaWgJdyR73MxwbpVlfpBNuWawpDIKMuakpcy0JknMW8NKwngNggeAXw3O163 /tQU8/bi1sEYpSmoFL9Zus3RMMTe5j318LbzzYRKwry8omuy7u8IBTpSd6wmPkcgwID0 UhN9cO6HazsYvB7UKCr/HKzYZEHzehi9BGYBaxqk78RK4t44FnXOZ0u+Vd76MvwrYxzC syEU/44F8aEXPC8HUcw58v4HAExKvdIgdrDrq2wCn9q+UmBjrywawDAgaBYuX/RxK0tJ WqyRz3beLQA0zJSpEJr6lIiHC/ZWu1uI76XCFhwSlq6W/YHFAO395lvlutBQCMJf5be7 gbvw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1717661454; x=1718266254; h=mime-version:user-agent:content-transfer-encoding:autocrypt :references:in-reply-to:date:cc:to:from:subject:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=OiLKUW2+2tNN+p7QJ6i97yhN4aM0YoAGrvjixVkAQhE=; b=CbGpIY5OKcUEzaZ1CO7gHuL8/z/R36ia3FuyklZ3NRYfZNH1dVUjORIDtc+yZ8ESrP VeGwWtTSSsu9OJp0tRqx0Hgy7/TMgScqTrPDhezOoP7QiidPS48NCX33iNRaEYOIfxnS MJf+Km7U1G3TGVH3FwMa8wdd3mbHUUoGhLICaJoX3b+1/3oXjj/lWCTu1by6RH746x0O PuUdfCYtkX9ycc7E9cDB5n5L5JKc91XUDR0bxUTA33FCpXHTtSjT/z93Vl85/C02fYQj fpyzzowzjoGoSZn8WbBeAuSuuBmCw1cW3rJktGdezJ56IKe44l/j3viniffLx9ICFqax bNJA== X-Forwarded-Encrypted: i=1; AJvYcCUjbn+//O6fQPwXnMWy3uk+bQaV1zjsVaCnaAY+rL7H2IWUgOK963IFm1EKPL4VJwSUdp1aIxG61irIgn2v1Uy2HLIe2ytCNIcUmzqxcx5h X-Gm-Message-State: AOJu0YyUhonySeWTkmGpCWm1TQVQ1OxiqC948qTHzXci/Z0VQqYRKMXo /dL+PtYo4ltGmAXrlNXP+wi+16hYA0lXuQ1+86gymbl72e6rYeeo8s1Nne7MQoE= X-Google-Smtp-Source: AGHT+IEstMBagtpaqTSnXAzuVkogszESrxIX3puShH9e95ruol/9dvFhIgUH21xnMgN3zyKW/Q5zgA== X-Received: by 2002:a50:99db:0:b0:572:7bda:1709 with SMTP id 4fb4d7f45d1cf-57a8b69cfeamr3269634a12.9.1717661454390; Thu, 06 Jun 2024 01:10:54 -0700 (PDT) Received: from localhost.localdomain ([88.116.133.170]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-57aae102c7esm662957a12.45.2024.06.06.01.10.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 06 Jun 2024 01:10:54 -0700 (PDT) Message-ID: <8807644dd252993a498b4ec77e6ecbc46808b142.camel@cybertec.at> Subject: Re: BUG #18477: A specific SQL query with "ORDER BY ... NULLS FIRST" is performing poorly if an ordering column is n From: Laurenz Albe To: David Rowley , Tom Lane Cc: Alvaro Herrera , Alexander Alexander , pgsql-bugs@lists.postgresql.org Date: Thu, 06 Jun 2024 10:10:53 +0200 In-Reply-To: References: <202405241003.uxtpwvtwcods@alvherre.pgsql> <951329.1717645689@sss.pgh.pa.us> Autocrypt: addr=laurenz.albe@cybertec.at; prefer-encrypt=mutual; keydata=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 bT5UrLvJ2jb99bA9QARzhFaxzyn0F/BUKzuIjRGNs/n6d5dNUFA0kOt8sX+TacmC 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 lDrT4wxdLJ/XCdbPPAyl+lZtOLsaHEEZvYNyTXwZc35dVf3R4/oz20HoG6s7ct8e1 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 36UMAx4ulWMyqJajLNGY0DdG8qIsR5nxRhrnK/mrCidZ8F9/D3bWAl4rjtHlsztN59 +AnW5l0HsQcY9ntFL/zEBOaonjdJf Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.4 (3.50.4-1.fc39) MIME-Version: 1.0 List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Archived-At: Precedence: bulk On Thu, 2024-06-06 at 17:04 +1200, David Rowley wrote: > On Thu, 6 Jun 2024 at 15:48, Tom Lane wrote: > > AFAICS the problem is purely self-inflicted damage: why is the user > > specifying NULLS FIRST if he knows the column is not-null? >=20 > If the user has some genuine reason for creating a NULLS FIRST index > for some other query, then it might be nice if we were able to use > that index for Merge Joins instead of them having to create another > index to speed up the join query. I cannot imagine a genuine reason for creating a NULLS FIRST index on a NOT NULL column, but perhaps I am too narrow-minded. Yours, Laurenz Albe