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Commit 71f4c8c6f74b (which implemented DETACH CONCURRENTLY) added code to create a separate table constraint when a table is detached concurrently, identical to the partition constraint, on the theory that such a constraint was needed in case the optimizer had constructed any query plans that depended on the constraint being there. However, that theory was apparently bogus because any such plans would be invalidated. For hash partitioning, those constraints are problematic, because their expressions reference the OID of the parent partitioned table, to which the detached table is no longer related; this causes all sorts of problems (such as inability of restoring a pg_dump of that table, and the table no longer working properly if the partitioned table is later dropped). We'd like to get rid of all those constraints. In fact, for branch master, do that -- no longer create any substitute constraints. However, out of fear that some users might somehow depend on these constraints for other partitioning strategies, for stable branches (back to 14, which added DETACH CONCURRENTLY), only do it for hash partitioning. (If you repeatedly DETACH CONCURRENTLY and then ATTACH a partition, then with this constraint addition you don't need to scan the table in the ATTACH step, which presumably is good. But if users really valued this feature, they would have requested that it worked for non-concurrent DETACH also.) Author: Haiyang Li <mohen.lhy@alibaba-inc.com> Reported-by: Fei Changhong <feichanghong@qq.com> Reported-by: Haiyang Li <mohen.lhy@alibaba-inc.com> Backpatch-through: 14 Discussion: https://postgr.es/m/18371-7fef49f63de13f02@postgresql.org Discussion: https://postgr.es/m/19070-781326347ade7c57@postgresql.org
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/.