This metapackage always depends on the currently supported PostgreSQL
 database documentation package.
 .
 PostgreSQL is a fully featured object-relational database management
 system. It supports a large part of the SQL standard and is designed
 to be extensible by users in many aspects. Some of the features are:
 ACID transactions, foreign keys, views, sequences, subqueries,
 triggers, user-defined types and functions, outer joins, multiversion
 concurrency control. Graphical user interfaces and bindings for many
 programming languages are available as well.