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Allow the COMMUTATOR, NEGATOR, MERGES, and HASHES attributes to be set by ALTER OPERATOR. However, we don't allow COMMUTATOR/NEGATOR to be changed once set, nor allow the MERGES/HASHES flags to be unset once set. Changes like that might invalidate plans already made, and dealing with the consequences seems like more trouble than it's worth. The main use-case we foresee for this is to allow addition of missed properties in extension update scripts, such as extending an existing operator to support hashing. So only transitions from not-set to set states seem very useful. This patch also causes us to reject some incorrect cases that formerly resulted in inconsistent catalog state, such as trying to set the commutator of an operator to be some other operator that already has a (different) commutator. While at it, move the InvokeObjectPostCreateHook call for CREATE OPERATOR to not occur until after we've fixed up commutator or negator links as needed. The previous ordering could only be justified by thinking of the OperatorUpd call as a kind of ALTER OPERATOR step; but we don't call InvokeObjectPostAlterHook therein. It seems better to let the hook see the final state of the operator object. In the documentation, move the discussion of how to establish commutator pairs from xoper.sgml to the CREATE OPERATOR ref page. Tommy Pavlicek, reviewed and editorialized a bit by me Discussion: https://postgr.es/m/CAEhP-W-vGVzf4udhR5M8Bdv88UYnPrhoSkj3ieR3QNrsGQoqdg@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/.