The PostgreSQL Global Development Group &legal; This part of the manual is the description of the client-side programming interfaces and support libraries for various languages. &libpq; &lobj; &libpqpp; &libpgtcl; &libpgeasy; &ecpg; &odbc; &jdbc; &pygresql; This second part of the manual explains the PostgreSQL approach to extensibility and describe how users can extend PostgreSQL by adding user-defined types, operators, aggregates, and both query language and programming language functions. After a discussion of the PostgreSQL rule system, we discuss the trigger and SPI interfaces. &arch-pg; &extend; &xfunc; &xtypes; &xoper; &xaggr; &rules; &xindex; &indexcost; &gist; &trigger; &spi; This part documents the procedural languages available in the PostgreSQL distribution as well as general issues concerning procedural languages. &xplang; &plsql; &pltcl; &plperl; &plpython;