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diff --git a/doc/src/sgml/html/plperl-under-the-hood.html b/doc/src/sgml/html/plperl-under-the-hood.html new file mode 100644 index 0000000..6984a23 --- /dev/null +++ b/doc/src/sgml/html/plperl-under-the-hood.html @@ -0,0 +1,111 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>45.8. PL/Perl Under the Hood</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="plperl-event-triggers.html" title="45.7. PL/Perl Event Triggers" /><link rel="next" href="plpython.html" title="Chapter 46. PL/Python — Python Procedural Language" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">45.8. PL/Perl Under the Hood</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="plperl-event-triggers.html" title="45.7. PL/Perl Event Triggers">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="plperl.html" title="Chapter 45. PL/Perl — Perl Procedural Language">Up</a></td><th width="60%" align="center">Chapter 45. PL/Perl — Perl Procedural Language</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 14.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="plpython.html" title="Chapter 46. PL/Python — Python Procedural Language">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="PLPERL-UNDER-THE-HOOD"><div class="titlepage"><div><div><h2 class="title" style="clear: both">45.8. PL/Perl Under the Hood</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="plperl-under-the-hood.html#PLPERL-CONFIG">45.8.1. Configuration</a></span></dt><dt><span class="sect2"><a href="plperl-under-the-hood.html#PLPERL-MISSING">45.8.2. Limitations and Missing Features</a></span></dt></dl></div><div class="sect2" id="PLPERL-CONFIG"><div class="titlepage"><div><div><h3 class="title">45.8.1. Configuration</h3></div></div></div><p> + This section lists configuration parameters that affect <span class="application">PL/Perl</span>. + </p><div class="variablelist"><dl class="variablelist"><dt id="GUC-PLPERL-ON-INIT"><span class="term"> + <code class="varname">plperl.on_init</code> (<code class="type">string</code>) + <a id="id-1.8.10.16.2.3.1.1.3" class="indexterm"></a> + </span></dt><dd><p> + Specifies Perl code to be executed when a Perl interpreter is first + initialized, before it is specialized for use by <code class="literal">plperl</code> or + <code class="literal">plperlu</code>. + The SPI functions are not available when this code is executed. + If the code fails with an error it will abort the initialization of + the interpreter and propagate out to the calling query, causing the + current transaction or subtransaction to be aborted. + </p><p> + The Perl code is limited to a single string. Longer code can be placed + into a module and loaded by the <code class="literal">on_init</code> string. + Examples: +</p><pre class="programlisting"> +plperl.on_init = 'require "plperlinit.pl"' +plperl.on_init = 'use lib "/my/app"; use MyApp::PgInit;' +</pre><p> + </p><p> + Any modules loaded by <code class="literal">plperl.on_init</code>, either directly or + indirectly, will be available for use by <code class="literal">plperl</code>. This may + create a security risk. To see what modules have been loaded you can use: +</p><pre class="programlisting"> +DO 'elog(WARNING, join ", ", sort keys %INC)' LANGUAGE plperl; +</pre><p> + </p><p> + Initialization will happen in the postmaster if the <code class="literal">plperl</code> library is + included in <a class="xref" href="runtime-config-client.html#GUC-SHARED-PRELOAD-LIBRARIES">shared_preload_libraries</a>, in which + case extra consideration should be given to the risk of destabilizing + the postmaster. The principal reason for making use of this feature + is that Perl modules loaded by <code class="literal">plperl.on_init</code> need be + loaded only at postmaster start, and will be instantly available + without loading overhead in individual database sessions. However, + keep in mind that the overhead is avoided only for the first Perl + interpreter used by a database session — either PL/PerlU, or + PL/Perl for the first SQL role that calls a PL/Perl function. Any + additional Perl interpreters created in a database session will have + to execute <code class="literal">plperl.on_init</code> afresh. Also, on Windows there + will be no savings whatsoever from preloading, since the Perl + interpreter created in the postmaster process does not propagate to + child processes. + </p><p> + This parameter can only be set in the <code class="filename">postgresql.conf</code> file or on the server command line. + </p></dd><dt id="GUC-PLPERL-ON-PLPERL-INIT"><span class="term"> + <code class="varname">plperl.on_plperl_init</code> (<code class="type">string</code>) + <a id="id-1.8.10.16.2.3.2.1.3" class="indexterm"></a> + <br /></span><span class="term"> + <code class="varname">plperl.on_plperlu_init</code> (<code class="type">string</code>) + <a id="id-1.8.10.16.2.3.2.2.3" class="indexterm"></a> + </span></dt><dd><p> + These parameters specify Perl code to be executed when a Perl + interpreter is specialized for <code class="literal">plperl</code> or + <code class="literal">plperlu</code> respectively. This will happen when a PL/Perl or + PL/PerlU function is first executed in a database session, or when + an additional interpreter has to be created because the other language + is called or a PL/Perl function is called by a new SQL role. This + follows any initialization done by <code class="literal">plperl.on_init</code>. + The SPI functions are not available when this code is executed. + The Perl code in <code class="literal">plperl.on_plperl_init</code> is executed after + <span class="quote">“<span class="quote">locking down</span>”</span> the interpreter, and thus it can only perform + trusted operations. + </p><p> + If the code fails with an error it will abort the initialization and + propagate out to the calling query, causing the current transaction or + subtransaction to be aborted. Any actions already done within Perl + won't be undone; however, that interpreter won't be used again. + If the language is used again the initialization will be attempted + again within a fresh Perl interpreter. + </p><p> + Only superusers can change these settings. Although these settings + can be changed within a session, such changes will not affect Perl + interpreters that have already been used to execute functions. + </p></dd><dt id="GUC-PLPERL-USE-STRICT"><span class="term"> + <code class="varname">plperl.use_strict</code> (<code class="type">boolean</code>) + <a id="id-1.8.10.16.2.3.3.1.3" class="indexterm"></a> + </span></dt><dd><p> + When set true subsequent compilations of PL/Perl functions will have + the <code class="literal">strict</code> pragma enabled. This parameter does not affect + functions already compiled in the current session. + </p></dd></dl></div></div><div class="sect2" id="PLPERL-MISSING"><div class="titlepage"><div><div><h3 class="title">45.8.2. Limitations and Missing Features</h3></div></div></div><p> + The following features are currently missing from PL/Perl, but they + would make welcome contributions. + + </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> + PL/Perl functions cannot call each other directly. + </p></li><li class="listitem"><p> + SPI is not yet fully implemented. + </p></li><li class="listitem"><p> + If you are fetching very large data sets using + <code class="literal">spi_exec_query</code>, you should be aware that + these will all go into memory. You can avoid this by using + <code class="literal">spi_query</code>/<code class="literal">spi_fetchrow</code> as + illustrated earlier. + </p><p> + A similar problem occurs if a set-returning function passes a + large set of rows back to PostgreSQL via <code class="literal">return</code>. You + can avoid this problem too by instead using + <code class="literal">return_next</code> for each row returned, as shown + previously. + </p></li><li class="listitem"><p> + When a session ends normally, not due to a fatal error, any + <code class="literal">END</code> blocks that have been defined are executed. + Currently no other actions are performed. Specifically, + file handles are not automatically flushed and objects are + not automatically destroyed. + </p></li></ul></div><p> + </p></div></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="plperl-event-triggers.html" title="45.7. PL/Perl Event Triggers">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="plperl.html" title="Chapter 45. PL/Perl — Perl Procedural Language">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="plpython.html" title="Chapter 46. PL/Python — Python Procedural Language">Next</a></td></tr><tr><td width="40%" align="left" valign="top">45.7. PL/Perl Event Triggers </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 14.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> Chapter 46. PL/Python — Python Procedural Language</td></tr></table></div></body></html>
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