diff options
Diffstat (limited to 'doc/src/sgml/html/plperl-global.html')
| -rw-r--r-- | doc/src/sgml/html/plperl-global.html | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/doc/src/sgml/html/plperl-global.html b/doc/src/sgml/html/plperl-global.html new file mode 100644 index 0000000..da913c2 --- /dev/null +++ b/doc/src/sgml/html/plperl-global.html @@ -0,0 +1,65 @@ +<?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 $$ + my $text_to_quote = shift; + my $qfunc = $_SHARED{myquote}; + return &$qfunc($text_to_quote); +$$ LANGUAGE plperl; +</pre><p> + + (You could have replaced the above with the one-liner + <code class="literal">return $_SHARED{myquote}->($_[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 |