Five years after the release of PostgreSQL 8.0, the developers are preparing for the next major version jump with the release of a beta version of PostgreSQL 9.0. The most prominent feature in the new release is integrated replication using "Hot Standby" and "Streaming Replication".

Streaming Replication allows a slave system to connect to the primary server and receive a stream of WAL (Write Ahead Log) records as they are generated, rather than having to wait for those records to be written to disk and picked up later. This allows the standby to be more up to date. Hot Standby allows connection to a server which is in recovery mode. While still in recovery mode the server can process read-only queries and can move to normal operations without disconnection users.

Other changes include the moving of LISTEN / NOTIFY events from a system table to a memory queue for better performance, an added ability for NOTIFY to pass an optional string to listeners, the implementation of anonymous functions using the DO statement and SQL compliant per-column triggers. Server side language support has been enhanced; stored procedures can now be written in Python 3 and Perl procedures can now use use strict and require .

The CREATE TABLE statement now allows developers to specify EXCLUDE as non-traditional constraint. The documentation gives an example of using EXCLUDE as way of ensuring that no two records contain overlapping circles.

The release notes contain the full details of the changes. To move to PostgreSQL 9.0 from a previous version requires a pg_dump to export from the older database into the new version. Alternatively, the data directory can be updated directly using pg_migrator . The source for the new beta is available on line as is a Windows installer and binaries for other platforms.

PostgreSQL is an open-source Object-Relational DBMS supporting almost all SQL constructs. The PostgreSQL development includes employees of Red Hat, F-Secure and EnterpriseDB. PostgreSQL is released under the PostgreSQL License, a liberal Open Source license, similar to the BSD or MIT licenses.

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