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transaction as aborted. Since we only call XactLockTableWait on XIDs that we believe to be currently running, the odds of this code ever actually firing are minimal. It's certainly unnecessary, since a transaction that's not either running or committed will be presumed aborted anyway. What's more, it's not hard to imagine scenarios where this could result in corrupting pg_clog: for instance, if a bogus XID somehow got passed to XactLockTableWait. I think the code probably dates from the ancient era when we didn't have TransactionIdIsInProgress; back then it may have been necessary, but now I think it's a waste of cycles and potentially dangerous. Per discussion with Qingqing Zhou and Karsten Hilbert.
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. The JDBC, ODBC, C++, Python, and Tcl interfaces have been moved to the PostgreSQL Projects Web Site at http://gborg.postgresql.org for separate maintenance. A Perl DBI/DBD driver is available from CPAN. 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 ftp://ftp.postgresql.org/pub/. For more information look at our web site located at http://www.postgresql.org/.