PostgreSQL is a free relational database server. It has been actively established for 15 years and over this time has provided evidence of stability and efficiency, gaining an excellent reputation among professionals around the world. PostgreSQL version 8.4 or later is ANSI-SQL 92/99 compliant and has been equipped with a number of advanced mechanisms, including GiST tree indexing and table structure inheritance.

As one of the few, it enables the use of different languages when writing stored procedures (e.g. Java, Perl, Python, C/C+++). PostgreSQL is available in versions for all popular operating systems, and has ready-made interfaces for C/C++, Java, .NET, Perl, Python, Ruby, Tcl, ODBC and other technologies, as well as very good documentation with user comments.