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Commit 9a974cbcba005256a19991203583a94b4f9a21a9 arranged to preserve relfilenodes and tablespace OIDs. For similar reasons, also arrange to preserve database OIDs. One problem is that, up until now, the OIDs assigned to the template0 and postgres databases have not been fixed. This could be a problem when upgrading, because pg_upgrade might try to migrate a database from the old cluster to the new cluster while keeping the OID and find a different database with that OID, resulting in a failure. If it finds a database with the same name and the same OID that's OK: it will be dropped and recreated. But the same OID and a different name is a problem. To prevent that, fix the OIDs for postgres and template0 to specific values less than 16384. To avoid running afoul of this rule, these values should not be changed in future releases. It's not a problem that these OIDs aren't fixed in existing releases, because the OIDs that we're assigning here weren't used for either of these databases in any previous release. Thus, there's no chance that an upgrade of a cluster from any previous release will collide with the OIDs we're assigning here. And going forward, the OIDs will always be fixed, so the only potential collision is with a system database having the same name and the same OID, which is OK. This patch lets users assign a specific OID to a database as well, provided however that it can't be less than 16384. I (rhaas) thought it might be better not to expose this capability to users, but the consensus was otherwise, so the syntax is documented. Letting users assign OIDs below 16384 would not be OK, though, because a user-created database with a low-numbered OID might collide with a system-created database in a future release. We therefore prohibit that. Shruthi KC, based on an earlier patch from Antonin Houska, reviewed and with some adjustments by me. Discussion: http://postgr.es/m/CA+TgmoYgTwYcUmB=e8+hRHOFA0kkS6Kde85+UNdon6q7bt1niQ@mail.gmail.com Discussion: http://postgr.es/m/CAASxf_Mnwm1Dh2vd5FAhVX6S1nwNSZUB1z12VddYtM++H2+p7w@mail.gmail.com
PostgreSQL Database Management System ===================================== This directory contains the source code distribution of the PostgreSQL database management system. PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download/ See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.