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Condition variables provide a flexible way to sleep until a cooperating process causes an arbitrary condition to become true. In simple cases, this can be accomplished with a WaitLatch/ResetLatch loop; the cooperating process can call SetLatch after performing work that might cause the condition to be satisfied, and the waiting process can recheck the condition each time. However, if the process performing the work doesn't have an easy way to identify which processes might be waiting, this doesn't work, because it can't identify which latches to set. Condition variables solve that problem by internally maintaining a list of waiters; a process that may have caused some waiter's condition to be satisfied must "signal" or "broadcast" on the condition variable. Robert Haas and Thomas Munro
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/.