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plpgsql's historical method for converting datatypes during assignments was to apply the source type's output function and then the destination type's input function. Aside from being miserably inefficient in most cases, this method failed outright in many cases where a user might expect it to work; an example is that "declare x int; ... x := 3.9;" would fail, not round the value to 4. Instead, let's convert by applying the appropriate assignment cast whenever there is one. To avoid breaking compatibility unnecessarily, fall back to the I/O conversion method if there is no assignment cast. So far as I can tell, there is just one case where this method produces a different result than the old code in a case where the old code would not have thrown an error. That is assignment of a boolean value to a string variable (type text, varchar, or bpchar); the old way gave boolean's output representation, ie 't'/'f', while the new way follows the behavior of the bool-to-text cast and so gives 'true' or 'false'. This will need to be called out as an incompatibility in the 9.5 release notes. Aside from handling many conversion cases more sanely, this method is often significantly faster than the old way. In part that's because of more effective caching of the conversion info.
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: http://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 http://www.postgresql.org/download/. For more information look at our web site located at http://www.postgresql.org/.