1f66c657f2
This restriction is implicit in the check-only-once implementation we use for table and domain constraints, but it wasn't spelled out anywhere, nor was there any advice about how to alter a constraint's behavior safely. Improve that. I was also dissatisfied with the documentation of ALTER DOMAIN VALIDATE CONSTRAINT, which entirely failed to explain the use of that feature; and thence decided that ALTER TABLE VALIDATE CONSTRAINT could be documented better as well. Perhaps we should back-patch this, along with the related commit 36d442a25, but for now I refrained. Discussion: https://postgr.es/m/12539.1544107316@sss.pgh.pa.us
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/.