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Patch to the pl/perl documents that clarifies the scope of global data and

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gives an example of storing a code reference

by David Fetter
This commit is contained in:
Peter Eisentraut
2004-12-11 20:03:37 +00:00
parent e82cd783a1
commit d89042b443
1 changed files with 37 additions and 3 deletions
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40
doc/src/sgml/plperl.sgml
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@ -1,5 +1,5 @@
<!-- <!--
$PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.32 2004/11/21 21:17:01 tgl Exp $ $PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.33 2004/12/11 20:03:37 petere Exp $
--> -->
<chapter id="plperl"> <chapter id="plperl">
@ -315,8 +315,14 @@ $$ LANGUAGE plperl;
<title>Global Values in PL/Perl</title> <title>Global Values in PL/Perl</title>
<para> <para>
You can use the global hash <varname>%_SHARED</varname> to store You can use the global hash <varname>%_SHARED</varname> to store
data between function calls. For example: data, including code references, between function calls for the
lifetime of the current session, which is bounded from below by
the lifetime of the current transaction.
</para>
<para>
Here is a simple example for shared data:
<programlisting> <programlisting>
CREATE OR REPLACE FUNCTION set_var(name text, val text) RETURNS text AS $$ CREATE OR REPLACE FUNCTION set_var(name text, val text) RETURNS text AS $$
if ($_SHARED{$_[0]} = $_[1]) { if ($_SHARED{$_[0]} = $_[1]) {
@ -334,6 +340,34 @@ SELECT set_var('sample', 'Hello, PL/Perl! How's tricks?');
SELECT get_var('sample'); SELECT get_var('sample');
</programlisting> </programlisting>
</para> </para>
<para>
Here is a slightly more complicated example using a code reference:
<programlisting>
CREATE OR REPLACE FUNCTION myfuncs() RETURNS void AS $$
$_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;
</programlisting>
(You could have replaced the above with the one-liner
<literal>return $_SHARED{myquote}->($_[0]);</literal>
at the expense of readability.)
</para>
</sect1> </sect1>
<sect1 id="plperl-trusted"> <sect1 id="plperl-trusted">