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This patch adds the pseudo-types anycompatible, anycompatiblearray, anycompatiblenonarray, and anycompatiblerange. They work much like anyelement, anyarray, anynonarray, and anyrange respectively, except that the actual input values need not match precisely in type. Instead, if we can find a common supertype (using the same rules as for UNION/CASE type resolution), then the parser automatically promotes the input values to that type. For example, "myfunc(anycompatible, anycompatible)" can match a call with one integer and one bigint argument, with the integer automatically promoted to bigint. With anyelement in the definition, the user would have had to cast the integer explicitly. The new types also provide a second, independent set of type variables for function matching; thus with "myfunc(anyelement, anyelement, anycompatible) returns anycompatible" the first two arguments are constrained to be the same type, but the third can be some other type, and the result has the type of the third argument. The need for more than one set of type variables was foreseen back when we first invented the polymorphic types, but we never did anything about it. Pavel Stehule, revised a bit by me Discussion: https://postgr.es/m/CAFj8pRDna7VqNi8gR+Tt2Ktmz0cq5G93guc3Sbn_NVPLdXAkqA@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/.