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ReadNewTransactionId from GetSnapshotData --- with a "latestCompletedXid" variable that is updated during transaction commit or abort. Since latestCompletedXid is written only in places that had to lock ProcArrayLock exclusively anyway, and is read only in places that had to lock ProcArrayLock shared anyway, it adds no new locking requirements to the system despite being cluster-wide. Moreover, removing ReadNewTransactionId from snapshot acquisition eliminates the need to take both XidGenLock and ProcArrayLock at the same time. Since XidGenLock is sometimes held across I/O this can be a significant win. Some preliminary benchmarking suggested that this patch has no effect on average throughput but can significantly improve the worst-case transaction times seen in pgbench. Concept by Florian Pflug, implementation by Tom Lane. |
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| COPYRIGHT | ||
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| README | ||
| README.CVS | ||
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 including some of the more common listed below: C++ - http://thaiopensource.org/development/libpqxx/ JDBC - http://jdbc.postgresql.org ODBC - http://odbc.postgresql.org Perl - http://search.cpan.org/~dbdpg/ PHP - http://www.php.net Python - http://www.initd.org/ Ruby - http://ruby.scripting.ca/postgres/ Other language binding are available from a variety of contributing parties. PostgreSQL also has a great number of procedural languages available, a short but not complete list is below: PL/pgSQL - included in PostgreSQL source distribution PL/Perl - included in PostgreSQL source distribution PL/PHP - http://projects.commandprompt.com/projects/public/plphp PL/Python - included in PostgreSQL source distribution PL/Java - http://gborg.postgresql.org/project/pljava/projdisplay.php PL/Tcl - included in PostgreSQL source distribution 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/.