Chapter 42. Procedural Languages
Table of Contents
PostgreSQL allows user-defined functions to be written in other languages besides SQL and C. These other languages are generically called procedural languages ( PL s). For a function written in a procedural language, the database server has no built-in knowledge about how to interpret the function's source text. Instead, the task is passed to a special handler that knows the details of the language. The handler could either do all the work of parsing, syntax analysis, execution, etc. itself, or it could serve as " glue " between PostgreSQL and an existing implementation of a programming language. The handler itself is a C language function compiled into a shared object and loaded on demand, just like any other C function.
There are currently four procedural languages available in the standard PostgreSQL distribution: PL/pgSQL ( Chapter 43 ), PL/Tcl ( Chapter 44 ), PL/Perl ( Chapter 45 ), and PL/Python ( Chapter 46 ). There are additional procedural languages available that are not included in the core distribution. Appendix H has information about finding them. In addition other languages can be defined by users; the basics of developing a new procedural language are covered in Chapter 56 .