Current version of PostgreSQL supports only one collation per database cluster set by initdb. This does not meet the requirements of some users developing multi-lingual applications.

The goal of the work will be to implement collation at database level and make foundations for further national language support development. User will be able to set collation when creating database or change collation of existing one. Particulary commands CREATE DATABASE... COLLATE … and ALTER DATABASE … COLLATE … regarding ANSI standard.
Work will also implement.possibility of creating users's own collation collection – commands CREATE COLLATION … FROM … USING and DROP COLLATION regaring ANSI standard.