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>Chapter 38. Procedural Languages</H1
><P
> <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> allows user-defined functions
to be written in other languages besides SQL and C. These other
languages are generically called <I
CLASS="FIRSTTERM"
>procedural
languages</I
> (<ACRONYM
CLASS="ACRONYM"
>PL</ACRONYM
>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 <SPAN
CLASS="QUOTE"
>"glue"</SPAN
> between
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> 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.
</P
><P
> There are currently four procedural languages available in the
standard <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> distribution:
<SPAN
CLASS="APPLICATION"
>PL/pgSQL</SPAN
> (<A
HREF="plpgsql.html"
>Chapter 39</A
>),
<SPAN
CLASS="APPLICATION"
>PL/Tcl</SPAN
> (<A
HREF="pltcl.html"
>Chapter 40</A
>),
<SPAN
CLASS="APPLICATION"
>PL/Perl</SPAN
> (<A
HREF="plperl.html"
>Chapter 41</A
>), and
<SPAN
CLASS="APPLICATION"
>PL/Python</SPAN
> (<A
HREF="plpython.html"
>Chapter 42</A
>).
There are additional procedural languages available that are not
included in the core distribution. <A
HREF="external-projects.html"
>Appendix H</A
>
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 <A
HREF="plhandler.html"
>Chapter 49</A
>.
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