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Fri, 13 Nov 2020 07:15:42 +0000 From: "osumi.takamichi@fujitsu.com" To: "tsunakawa.takay@fujitsu.com" , 'Kyotaro Horiguchi' CC: "sfrost@snowman.net" , "masao.fujii@oss.nttdata.com" , "ashutosh.bapat.oss@gmail.com" , "pgsql-hackers@lists.postgresql.org" Subject: RE: In-placre persistance change of a relation Thread-Topic: In-placre persistance change of a relation Thread-Index: AQHWuAVWyR9iwv1A1kKrC69Bti43RanFeQaAgAAnc4CAAAgCIA== Date: Fri, 13 Nov 2020 07:15:41 +0000 Message-ID: References: <20201111.173317.460890039962481381.horikyota.ntt@gmail.com> <20201113.132201.148696021363404735.horikyota.ntt@gmail.com> In-Reply-To: Accept-Language: ja-JP, en-US Content-Language: ja-JP X-MS-Has-Attach: X-MS-TNEF-Correlator: x-securitypolicycheck: OK by SHieldMailChecker v2.6.3 x-shieldmailcheckermailid: 3d8092fa6a684eaf8190e9d29d5b7548 authentication-results: fujitsu.com; dkim=none (message not signed) header.d=none;fujitsu.com; dmarc=none action=none header.from=fujitsu.com; x-originating-ip: [218.44.52.178] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 9999c0e0-7f9e-4566-7c11-08d887a3ee50 x-ms-traffictypediagnostic: OSBPR01MB3142: x-ms-exchange-transport-forked: True x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:2449; 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x-ms-exchange-antispam-messagedata: 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 Content-Type: text/plain; charset="iso-2022-jp" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: fujitsu.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: OSBPR01MB4888.jpnprd01.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 9999c0e0-7f9e-4566-7c11-08d887a3ee50 X-MS-Exchange-CrossTenant-originalarrivaltime: 13 Nov 2020 07:15:42.0276 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: a19f121d-81e1-4858-a9d8-736e267fd4c7 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: 4D7dbLZ0OXuYZSryz7NfxSC361Nqu96plCwcu3eXpwyIAv6pI9dZgm7t3IabDtsr4+z5+00mYKnvsyBlM0vJBjxw8zWScHu+XoMwTLvIH2E= X-MS-Exchange-Transport-CrossTenantHeadersStamped: OSBPR01MB3142 List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Precedence: bulk Hello, Tsunakawa-San > Do you know the reason why data copy was done before? And, it may be > odd for me to ask this, but I think I saw someone referred to the past > discussion that eliminating data copy is difficult due to some processing= at > commit. I can't find it. I can share 2 sources why to eliminate the data copy is difficult in hacker= s thread. Tom's remark and the context to copy relation's data. https://www.postgresql.org/message-id/flat/31724.1394163360%40sss.pgh.pa.us= #31724.1394163360@sss.pgh.pa.us Amit-San quoted this thread and mentioned that point in another thread. https://www.postgresql.org/message-id/CAA4eK1%2BHDqS%2B1fhs5Jf9o4ZujQT%3DXB= Z6sU0kOuEh2hqQAC%2Bt%3Dw%40mail.gmail.com Best, Takamichi Osumi