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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-04 12:17:33 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-04 12:17:33 +0000
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postgresql-15-5e45211a64149b3c659b90ff2de6fa982a5a93ed.zip
Adding upstream version 15.5.upstream/15.5
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+<?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>45.4. Global Values in PL/Perl</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-builtins.html" title="45.3. Built-in Functions" /><link rel="next" href="plperl-trusted.html" title="45.5. Trusted and Untrusted PL/Perl" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">45.4. Global Values in PL/Perl</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="plperl-builtins.html" title="45.3. Built-in Functions">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 15.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="plperl-trusted.html" title="45.5. Trusted and Untrusted PL/Perl">Next</a></td></tr></table><hr /></div><div class="sect1" id="PLPERL-GLOBAL"><div class="titlepage"><div><div><h2 class="title" style="clear: both">45.4. Global Values in PL/Perl</h2></div></div></div><p>
+ You can use the global hash <code class="varname">%_SHARED</code> to store
+ data, including code references, between function calls for the
+ lifetime of the current session.
+ </p><p>
+ Here is a simple example for shared data:
+</p><pre class="programlisting">
+CREATE OR REPLACE FUNCTION set_var(name text, val text) RETURNS text AS $$
+ if ($_SHARED{$_[0]} = $_[1]) {
+ return 'ok';
+ } else {
+ return "cannot set shared variable $_[0] to $_[1]";
+ }
+$$ LANGUAGE plperl;
+
+CREATE OR REPLACE FUNCTION get_var(name text) RETURNS text AS $$
+ return $_SHARED{$_[0]};
+$$ LANGUAGE plperl;
+
+SELECT set_var('sample', 'Hello, PL/Perl! How''s tricks?');
+SELECT get_var('sample');
+</pre><p>
+ </p><p>
+ Here is a slightly more complicated example using a code reference:
+
+</p><pre class="programlisting">
+CREATE OR REPLACE FUNCTION myfuncs() RETURNS void AS $$
+ $_SHARED{myquote} = sub {
+ my $arg = shift;
+ $arg =~ s/(['\\])/\\$1/g;
+ return "'$arg'";
+ };
+$$ LANGUAGE plperl;
+
+SELECT myfuncs(); /* initializes the function */
+
+/* Set up a function that uses the quote function */
+
+CREATE OR REPLACE FUNCTION use_quote(TEXT) RETURNS text AS $$
+ my $text_to_quote = shift;
+ my $qfunc = $_SHARED{myquote};
+ return &amp;$qfunc($text_to_quote);
+$$ LANGUAGE plperl;
+</pre><p>
+
+ (You could have replaced the above with the one-liner
+ <code class="literal">return $_SHARED{myquote}-&gt;($_[0]);</code>
+ at the expense of readability.)
+ </p><p>
+ For security reasons, PL/Perl executes functions called by any one SQL role
+ in a separate Perl interpreter for that role. This prevents accidental or
+ malicious interference by one user with the behavior of another user's
+ PL/Perl functions. Each such interpreter has its own value of the
+ <code class="varname">%_SHARED</code> variable and other global state. Thus, two
+ PL/Perl functions will share the same value of <code class="varname">%_SHARED</code>
+ if and only if they are executed by the same SQL role. In an application
+ wherein a single session executes code under multiple SQL roles (via
+ <code class="literal">SECURITY DEFINER</code> functions, use of <code class="command">SET ROLE</code>, etc.)
+ you may need to take explicit steps to ensure that PL/Perl functions can
+ share data via <code class="varname">%_SHARED</code>. To do that, make sure that
+ functions that should communicate are owned by the same user, and mark
+ them <code class="literal">SECURITY DEFINER</code>. You must of course take care that
+ such functions can't be used to do anything unintended.
+ </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="plperl-builtins.html" title="45.3. Built-in Functions">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="plperl-trusted.html" title="45.5. Trusted and Untrusted PL/Perl">Next</a></td></tr><tr><td width="40%" align="left" valign="top">45.3. Built-in Functions </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 45.5. Trusted and Untrusted PL/Perl</td></tr></table></div></body></html> \ No newline at end of file