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Add warning about plperl nested named subroutines

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Andrew Dunstan
This commit is contained in:
Bruce Momjian
2005-10-12 14:28:33 +00:00
parent 0a28eb4622
commit 6b97e437ca
1 changed files with 22 additions and 10 deletions
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32
doc/src/sgml/plperl.sgml
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@ -1,5 +1,5 @@
<!-- <!--
$PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.45 2005/08/24 19:16:49 tgl Exp $ $PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.46 2005/10/12 14:28:33 momjian Exp $
--> -->
<chapter id="plperl"> <chapter id="plperl">
@ -53,22 +53,34 @@ CREATE FUNCTION <replaceable>funcname</replaceable> (<replaceable>argument-types
# PL/Perl function body # PL/Perl function body
$$ LANGUAGE plperl; $$ LANGUAGE plperl;
</programlisting> </programlisting>
The body of the function is ordinary Perl code. A PL/Perl function must The body of the function is ordinary Perl code. In fact, the PL/Perl
glue code wraps it inside a Perl subroutine. A PL/Perl function must
always return a scalar value. You can return more complex structures always return a scalar value. You can return more complex structures
(arrays, records, and sets) by returning a reference, as discussed below. (arrays, records, and sets) by returning a reference, as discussed below.
Never return a list. Never return a list.
</para> </para>
<note>
<para> <para>
The syntax of the <command>CREATE FUNCTION</command> command requires The use of named nested subroutines is dangerous in Perl, especially if
the function body to be written as a string constant. It is usually they refer to lexical variables in the enclosing scope. Because a PL/Perl
most convenient to use dollar quoting (see <xref function is wrapped in a subroutine, any named subroutine you create will
linkend="sql-syntax-dollar-quoting">) for the string constant. be nested. In general, it is far safer to create anonymous subroutines
If you choose to use regular single-quoted string constant syntax, which you call via a coderef. See the <literal>perldiag</literal>
you must escape single quote marks (<literal>'</>) and backslashes man page for more details.
(<literal>\</>) used in the body of the function, typically by
doubling them (see <xref linkend="sql-syntax-strings">).
</para> </para>
</note>
<para>
The syntax of the <command>CREATE FUNCTION</command> command requires
the function body to be written as a string constant. It is usually
most convenient to use dollar quoting (see <xref
linkend="sql-syntax-dollar-quoting">) for the string constant.
If you choose to use regular single-quoted string constant syntax,
you must escape single quote marks (<literal>'</>) and backslashes
(<literal>\</>) used in the body of the function, typically by
doubling them (see <xref linkend="sql-syntax-strings">).
</para>
<para> <para>
Arguments and results are handled as in any other Perl subroutine: Arguments and results are handled as in any other Perl subroutine: