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 4.96) (envelope-from ) id 1vdhI5-003bH3-1J for pgsql-performance@arkaria.postgresql.org; Thu, 08 Jan 2026 04:06:30 +0000 Received: from localhost ([127.0.0.1] helo=malur.postgresql.org) by malur.postgresql.org with esmtp (Exim 4.96) (envelope-from ) id 1vdhI4-00HPKu-1E for pgsql-performance@arkaria.postgresql.org; Thu, 08 Jan 2026 04:06:29 +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 4.96) (envelope-from ) id 1vdhEr-00HLNj-0C for pgsql-performance@lists.postgresql.org; Thu, 08 Jan 2026 04:03:09 +0000 Received: from mail-pl1-x62e.google.com ([2607:f8b0:4864:20::62e]) by magus.postgresql.org with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.96) (envelope-from ) id 1vdhEp-005Cny-1e for pgsql-performance@lists.postgresql.org; Thu, 08 Jan 2026 04:03:09 +0000 Received: by mail-pl1-x62e.google.com with SMTP id d9443c01a7336-2a0bae9aca3so20994515ad.3 for ; Wed, 07 Jan 2026 20:03:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1767844985; x=1768449785; darn=lists.postgresql.org; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=kzjpu8EJjtITkY9AVeLEAqVM8CeDXDdQy1lf/bVQ++U=; b=UFlLpukWiYJ0cVTFtkZ+Hvufs2Vv5AwfDMtxu1jbpWiwPmNTnUCuuAwgMJT1BdpAWP 9IqQqEFn0H4GDK3yQbm2zzBqC/QuFP3HlHXgKICCSmZVi4omUdxW2c8Bnpn6nLnSWOXs Mz+wc8oMfLRKMUOt3ut4p6HnoAFf8hrpJyk3LA4rgIdIc6EOQBdhNBwxcpo1JNhYTAlC Of2LEdmhdqkHG1E2F5U0CFdXM5tG1BHQ8zh2hB1F+34a01KlphSKhDBVf1y6DzVNmRmu Bs/KgTIkcK6eFwbOhDxsSB1zt469xzFR3UwoOU683CONCIYD3T94FiRrWkQSQqC/4nKX XXvw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1767844985; x=1768449785; h=content-transfer-encoding:in-reply-to:from:content-language :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=kzjpu8EJjtITkY9AVeLEAqVM8CeDXDdQy1lf/bVQ++U=; b=I9UTAVgrGoPEq322NukhH5OlST9ckitq5IFGYYU9AO6ysZTq+JcicnhSVbuxpEYiIJ ++63rJzYtGDUgmZ975379PCGujTIZHJu0WVjtYDSta/4ChJp5dWT1ww7SgysdazHBii6 5A2GQ9X/ve8qnlcQM18GlFwqDfKKNr9R7iPF1L6h/nhVmA4OeckzRfL9VgRqN2LztoKo 87CAsMunvBLCe2XgP8SraZb/bpy0SOAe2bT2RTDGMK8GFXo6qxomcTz/u3Bdrk6s0Knl xp9xVd9SzIp38VIrblyQg73cYP0EzrO8PhZ14kgPtznnjOEsPLc7Oez8HptXcvgWy4ir MGAQ== X-Gm-Message-State: AOJu0YxZ1ooH8HnJvWrKLGhmwK9hKGLLK8Do7dmO+0NlIr0BnOTUcgSK RQ4YL1e7CdIJPjEUsgtle1EqKt/8agtBXccN5si0a9qdinj2vVsaEoBV X-Gm-Gg: AY/fxX5G99JPIj4WfcpV4HQQWfKzxYFNkduE+mLU85hcU53kZGOB3NbgnMdf4zEhwBl dbKo+LDu+lHa+YH4x66OrLQDP5ZzYIRWDOuVoTbPfyxW01QfSYWwKETDlBn/XVhC1sJ7S/KXd8d qp/Fcg67CROf6qd4Mm1VExRz3Mz8M2GjiOoKYbyLtqnw/Z3pUfMqAMgcWwuZDdK2CWnk07XwCnW MIYAo8fqAe5lfulCxCspYd+FJY/W3U6FVkiwJxzm0XqAFD3H8E06TO2xEqA43N76gP4RDjZ6GQJ BfiA29i0hfLGllAIetQswl1/OgSf10Q4gmCd6dxSaj8Bk115iNjAl7sQ24qEvQoBuREK9nCs1rh oAkvrO7aVoJffjXJk4F1DsTHhv2i7ENlYFCDtw+Zf25Td3sTFWfrsCLXSEX3+pUhxLIhF7RYiax OSVp5tFFwDc6KT/SvfC0UiRe6r73UqOtbzhhDNATQcC6ptAck+Plxl4wjUeMCJNqeLcw== X-Google-Smtp-Source: AGHT+IHPIwkJhJoCH98titH64pVhRRhlIaqDJnwawgkjf/Z/zwf/NH/W8bsxMGT0NwY5R+T1Uga5Wg== X-Received: by 2002:a17:903:3884:b0:295:290d:4afa with SMTP id d9443c01a7336-2a3ee46179fmr43112875ad.23.1767844985327; Wed, 07 Jan 2026 20:03:05 -0800 (PST) Received: from ?IPV6:2404:4400:414b:1700:b092:c6d0:7613:982b? ([2404:4400:414b:1700:b092:c6d0:7613:982b]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2a3e3cb2c5bsm64282805ad.58.2026.01.07.20.03.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 07 Jan 2026 20:03:04 -0800 (PST) Message-ID: Date: Thu, 8 Jan 2026 17:03:01 +1300 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Unexpected planner choice in simple JOIN To: David Rowley Cc: pgsql-performance@lists.postgresql.org References: <71afdb09-0583-4af2-a3b3-50da4f987b9b@gmail.com> Content-Language: en-US From: Mark Kirkwood In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Archived-At: Precedence: bulk I don't think so - while the case I posted used a hash index on the child table, exactly the sane behaviour happens if it is a btree (I probably should have mentioned that sorry). Background is I discovered this while playing about with hash indexes...which I must say - someone has done excellent work on as in this *particular cases* they are getting me better query performance! regards Mark On 08/01/2026 16:56, David Rowley wrote: > On Thu, 8 Jan 2026 at 16:34, Mark Kirkwood wrote: >> This does seem to be related to parallel planning: > Isn't it just a case of hash indexes not allowing parallel scans? > > David