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documentation warnings against setting it nonzero unless active use of prepared transactions is intended and a suitable transaction manager has been installed. This should help to prevent the type of scenario we've seen several times now where a prepared transaction is forgotten and eventually causes severe maintenance problems (or even anti-wraparound shutdown). The only real reason we had the default be nonzero in the first place was to support regression testing of the feature. To still be able to do that, tweak pg_regress to force a nonzero value during "make check". Since we cannot force a nonzero value in "make installcheck", add a variant regression test "expected" file that shows the results that will be obtained when max_prepared_transactions is zero. Also, extend the HINT messages for transaction wraparound warnings to mention the possibility that old prepared transactions are causing the problem. All per today's discussion.
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. Changes between all PostgreSQL releases are recorded in the file HISTORY. 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/.