codekingpro/portable-devtools

1<?xml version="1.0" encoding="UTF-8" standalone="no"?>2<!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 16.3 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 <a href="#PLPERL-GLOBAL" class="id_link">#</a></h2></div></div></div><p>3    You can use the global hash <code class="varname">%_SHARED</code> to store4    data, including code references, between function calls for the5    lifetime of the current session.6  </p><p>7    Here is a simple example for shared data:8</p><pre class="programlisting">9CREATE OR REPLACE FUNCTION set_var(name text, val text) RETURNS text AS $$10    if ($_SHARED{$_[0]} = $_[1]) {11        return 'ok';12    } else {13        return "cannot set shared variable $_[0] to $_[1]";14    }15$$ LANGUAGE plperl;16 17CREATE OR REPLACE FUNCTION get_var(name text) RETURNS text AS $$18    return $_SHARED{$_[0]};19$$ LANGUAGE plperl;20 21SELECT set_var('sample', 'Hello, PL/Perl!  How''s tricks?');22SELECT get_var('sample');23</pre><p>24  </p><p>25   Here is a slightly more complicated example using a code reference:26 27</p><pre class="programlisting">28CREATE OR REPLACE FUNCTION myfuncs() RETURNS void AS $$29    $_SHARED{myquote} = sub {30        my $arg = shift;31        $arg =~ s/(['\\])/\\$1/g;32        return "'$arg'";33    };34$$ LANGUAGE plperl;35 36SELECT myfuncs(); /* initializes the function */37 38/* Set up a function that uses the quote function */39 40CREATE OR REPLACE FUNCTION use_quote(TEXT) RETURNS text AS $$41    my $text_to_quote = shift;42    my $qfunc = $_SHARED{myquote};43    return &amp;$qfunc($text_to_quote);44$$ LANGUAGE plperl;45</pre><p>46 47   (You could have replaced the above with the one-liner48   <code class="literal">return $_SHARED{myquote}-&gt;($_[0]);</code>49   at the expense of readability.)50  </p><p>51   For security reasons, PL/Perl executes functions called by any one SQL role52   in a separate Perl interpreter for that role.  This prevents accidental or53   malicious interference by one user with the behavior of another user's54   PL/Perl functions.  Each such interpreter has its own value of the55   <code class="varname">%_SHARED</code> variable and other global state.  Thus, two56   PL/Perl functions will share the same value of <code class="varname">%_SHARED</code>57   if and only if they are executed by the same SQL role.  In an application58   wherein a single session executes code under multiple SQL roles (via59   <code class="literal">SECURITY DEFINER</code> functions, use of <code class="command">SET ROLE</code>, etc.)60   you may need to take explicit steps to ensure that PL/Perl functions can61   share data via <code class="varname">%_SHARED</code>.  To do that, make sure that62   functions that should communicate are owned by the same user, and mark63   them <code class="literal">SECURITY DEFINER</code>.  You must of course take care that64   such functions can't be used to do anything unintended.65  </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 16.3 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 45.5. Trusted and Untrusted PL/Perl</td></tr></table></div></body></html>