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When ALTER TABLE ... SET DATA TYPE affects a column referenced by constraints and indexes, it drop those constraints and indexes and recreates them afterwards, so that the definitions match the new data type. The original code did this by dropping one object at a time (commit 077db40fa1f3 of May 2004), which worked fine because the dependencies between the objects were pretty straightforward, and ordering the objects in a specific way was enough to make this work. However, when there are foreign key constraints in partitioned tables, the dependencies are no longer so straightforward, and we were getting errors when attempted: ERROR: cache lookup failed for constraint 16398 This can be fixed by doing all the drops in one pass instead, using performMultipleDeletions (introduced by df18c51f2955 of Aug 2006). With this change we can also remove the code to carefully order the list of objects to be deleted. Reported-by: Rajkumar Raghuwanshi <rajkumar.raghuwanshi@enterprisedb.com> Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/CAKcux6nWS_m+s=1Udk_U9B+QY7pA-Ac58qR5BdUfOyrwnWHDew@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/.