Thread: document plperl argument and return value representation
The attached docs patch makes clearer how arguments and return values in
pl/perl are escaped. This is to clarify the situation that Theo
Schlossnagle recently reported on -bugs.
If there's no objection I will apply this.
cheers
andrew
? plperldoc.patch
Index: plperl.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/plperl.sgml,v
retrieving revision 2.65
diff -c -r2.65 plperl.sgml
*** plperl.sgml 3 May 2007 15:05:56 -0000 2.65
--- plperl.sgml 3 May 2007 22:19:05 -0000
***************
*** 138,143 ****
--- 138,169 ----
</para>
<para>
+ Anything in a function argument or result that is not a reference is
+ a string, which is in the standard <productname>PostgreSQL</productname>
+ external text representation for the relevant data type. In the case of
+ ordinary numeric or text types, Perl will just do the right thing and
+ the programmer will normally not have to worry about it. However, in
+ other cases the argument will need to be converted into a form that is
+ more usable in Perl, and the return result will need to be converted to
+ the form that <productname>PostgreSQL</productname> expects. For example,
+ here is how to convert an argument of type bytea into unescaped binary
+ data:
+
+ <programlisting>
+ my $arg = shift;
+ $arg =~ s!\\(\d{3})!chr(oct($1))!ge;
+ </programlisting>
+
+ and here is how to escape binary data for a return value of type bytea:
+
+ <programlisting>
+ $retval =~ s!([^ -~])!sprintf("\\%03o",ord($1))!ge;
+ return $retval;
+ </programlisting>
+
+ </para>
+
+ <para>
Perl can return <productname>PostgreSQL</productname> arrays as
references to Perl arrays. Here is an example:
Andrew Dunstan wrote: > > The attached docs patch makes clearer how arguments and return values in > pl/perl are escaped. This is to clarify the situation that Theo > Schlossnagle recently reported on -bugs. I find the mix of arguments and results a bit confusing. Maybe you could put them in separate paragraphs. -- Alvaro Herrera http://www.CommandPrompt.com/ PostgreSQL Replication, Consulting, Custom Development, 24x7 support
Alvaro Herrera wrote:
> Andrew Dunstan wrote:
>
>> The attached docs patch makes clearer how arguments and return values in
>> pl/perl are escaped. This is to clarify the situation that Theo
>> Schlossnagle recently reported on -bugs.
>>
>
> I find the mix of arguments and results a bit confusing. Maybe you
> could put them in separate paragraphs.
>
>
Is this better?
I also took the opportunity to replace an unbalanced quote mark that was
screwing up the syntax highlighting.
cheers
andrew
Index: plperl.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/plperl.sgml,v
retrieving revision 2.65
diff -c -r2.65 plperl.sgml
*** plperl.sgml 3 May 2007 15:05:56 -0000 2.65
--- plperl.sgml 3 May 2007 23:44:04 -0000
***************
*** 138,150 ****
</para>
<para>
Perl can return <productname>PostgreSQL</productname> arrays as
references to Perl arrays. Here is an example:
<programlisting>
CREATE OR REPLACE function returns_array()
RETURNS text[][] AS $$
! return [['a"b','c,d'],['e\\f','g']];
$$ LANGUAGE plperl;
select returns_array();
--- 138,180 ----
</para>
<para>
+ Anything in a function argument that is not a reference is
+ a string, which is in the standard <productname>PostgreSQL</productname>
+ external text representation for the relevant data type. In the case of
+ ordinary numeric or text types, Perl will just do the right thing and
+ the programmer will normally not have to worry about it. However, in
+ other cases the argument will need to be converted into a form that is
+ more usable in Perl. For example, here is how to convert an argument of
+ type bytea into unescaped binary
+ data:
+
+ <programlisting>
+ my $arg = shift;
+ $arg =~ s!\\(\d{3})!chr(oct($1))!ge;
+ </programlisting>
+
+ </para>
+
+ <para>
+ Similarly, values passed back to <productname>PostgreSQL</productname>
+ must be in the external text representation format. For example, here
+ is how to escape binary data for a return value of type bytea:
+
+ <programlisting>
+ $retval =~ s!([^ -~])!sprintf("\\%03o",ord($1))!ge;
+ return $retval;
+ </programlisting>
+
+ </para>
+
+ <para>
Perl can return <productname>PostgreSQL</productname> arrays as
references to Perl arrays. Here is an example:
<programlisting>
CREATE OR REPLACE function returns_array()
RETURNS text[][] AS $$
! return [['a"b','c,d'],['e\\f','g']];
$$ LANGUAGE plperl;
select returns_array();
Andrew Dunstan <andrew@dunslane.net> writes:
> Is this better?
I suggest bytea -> <type>bytea</>, otherwise seems fine.
regards, tom lane
Andrew Dunstan wrote: > > > Alvaro Herrera wrote: > >Andrew Dunstan wrote: > > > >>The attached docs patch makes clearer how arguments and return values in > >>pl/perl are escaped. This is to clarify the situation that Theo > >>Schlossnagle recently reported on -bugs. > >> > > > >I find the mix of arguments and results a bit confusing. Maybe you > >could put them in separate paragraphs. > > Is this better? Yup, looks very nice. This message also serves to test whether I removed the annoying Mail-Followup-To header. It was actually a _feature_ of mutt (followup_to, which fired when I replied to a list to which I'm subscribed), which I disabled. Sorry about that. ETOOMANYWHICH, sorry about that as well :-) -- Alvaro Herrera http://www.CommandPrompt.com/ The PostgreSQL Company - Command Prompt, Inc.