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<th align="center" colspan="5">Chapter 40. Procedural Languages</th>
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<h2 class="title">Chapter 40. Procedural Languages</h2>
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<dt><span class="sect1"><a href="/docs/current/xplang-install.html">40.1. Installing Procedural Languages</a></span></dt>
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<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 <em class="firstterm">procedural languages</em> (<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">“<span class="quote">glue</span>”</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 class="xref" href="/docs/current/plpgsql.html" title="Chapter 41. PL/pgSQL — SQL Procedural Language">Chapter 41</a>), <span class="application">PL/Tcl</span> (<a class="xref" href="/docs/current/pltcl.html" title="Chapter 42. PL/Tcl — Tcl Procedural Language">Chapter 42</a>), <span class="application">PL/Perl</span> (<a class="xref" href="/docs/current/plperl.html" title="Chapter 43. PL/Perl — Perl Procedural Language">Chapter 43</a>), and <span class="application">PL/Python</span> (<a class="xref" href="/docs/current/plpython.html" title="Chapter 44. PL/Python — Python Procedural Language">Chapter 44</a>). There are additional procedural languages available that are not included in the core distribution. <a class="xref" href="/docs/current/external-projects.html" title="Appendix H. External Projects">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 class="xref" href="/docs/current/plhandler.html" title="Chapter 57. Writing a Procedural Language Handler">Chapter 57</a>.</p>
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