This document discusses using Perl stored procedures with MariaDB. Key points include: - Perl stored procedures are implemented as Perl modules that use DBD::mysql to access the database from within the MariaDB process. This makes them easier to debug than SQL stored routines. - Examples are provided for simple "Hello World" procedures, handling errors, reading and returning data from queries, and modifying data by inserting rows. - Perl stored procedures allow extending MariaDB's functionality by leveraging thousands of modules on CPAN. As an example, the document shows how a procedure could implement a basic monitoring server using HTTP::Daemon to expose server status data via a JSON API.

1. Using Perl Stored
Procedures
with MariaDB
Antony T Curtis <atcurtis@gmail.com>
Special thanks to LinkedIn for permitting personal projects

2. Why Perl?
• CPAN
• "Multiplicity" / Thread-friendly.
• Lots of Perl code already written.
• MySQL UDFs have no access control.
• MySQL UDFs cannot execute dynamic SQL.
• Faster than “native” Stored Procedures.

3. Perl Stored Procedures
• Implemented as Perl modules.
• Use DBD::mysql to access database.
• Runs in-process with MariaDB.
• Easier to debug than SQL stored routines.

4. Hello World
MariaDB [Demo]> CREATE PROCEDURE PerlHello()
-> DYNAMIC RESULT SETS 1
-> NO SQL
-> LANGUAGE Perl
-> EXTERNAL NAME "HelloWorld::test";
Query OK, 0 rows affected (0.02 sec)
MariaDB [Demo]> call PerlHello();
+-----------------------+
| message |
+-----------------------+
| Hello World from Perl |
+-----------------------+
1 row in set (0.03 sec)
Query OK, 0 rows affected (0.03 sec)
package HelloWorld;
# put this file in <prefix>/lib/mysql/perl
use 5.008008;
use strict;
use warnings;
use Symbol qw(delete_package);
require Exporter;
our @ISA = qw(Exporter);
our @EXPORT_OK = qw( );
our @EXPORT = qw( test );
our $VERSION = '0.01';
sub test()
{
return {
'message' => 'Hello World from Perl',
};
}
1;

5. Hello World
MariaDB [Demo]> CREATE PROCEDURE PerlHello()
-> DYNAMIC RESULT SETS 1
-> NO SQL
-> LANGUAGE Perl
-> EXTERNAL NAME "HelloWorld::test";
Query OK, 0 rows affected (0.02 sec)
MariaDB [Demo]> call PerlHello();
+-----------------------+
| message |
+-----------------------+
| Hello World from Perl |
+-----------------------+
1 row in set (0.03 sec)
Query OK, 0 rows affected (0.03 sec)
package HelloWorld;
# put this file in <prefix>/lib/mysql/perl
use 5.008008;
use strict;
use warnings;
use Symbol qw(delete_package);
require Exporter;
our @ISA = qw(Exporter);
our @EXPORT_OK = qw( );
our @EXPORT = qw( test );
our $VERSION = '0.01';
sub test()
{
return {
'message' => 'Hello World from Perl',
};
}
1;

6. Error handling or die
MariaDB [Demo]> CREATE PROCEDURE PerlError()
-> DYNAMIC RESULT SETS 1
-> NO SQL
-> LANGUAGE Perl
-> EXTERNAL NAME "GoodbyeWorld::test";
Query OK, 0 rows affected (0.00 sec)
MariaDB [Demo]> call PerlError();
ERROR 1220 (HY000): Cannot open file: No
such file or directory at /usr/local/mysql/
lib/plugin/perl/GoodbyeWorld.pm line 16.
package GoodbyeWorld;
# put this file in <prefix>/lib/mysql/perl
use 5.008008;
use strict;
use warnings;
use Symbol qw(delete_package);
require Exporter;
our @ISA = qw(Exporter);
our @EXPORT_OK = qw( );
our @EXPORT = qw( test );
our $VERSION = '0.01';
sub test(
{
open FILE, "</something/nonexist"
or die "Cannot open file: $!";
return {
'message' => 'Goodbye World from Perl',
};
}
1;

7. Reading Data
MariaDB [employees]> CREATE PROCEDURE employee(
-> empno INT)
-> DYNAMIC RESULT SETS 1
-> READS SQL DATA
-> LANGUAGE Perl
-> EXTERNAL NAME "ReadData::test";
Query OK, 0 rows affected (0.02 sec)
MariaDB [employees]> call employee(10034)G
*************************** 1. row
***************************
birth_date: 1962-12-29
emp_no: 10034
first_name: Bader
gender: M
hire_date: 1988-09-21
last_name: Swan
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
package ReadData;
# put this file in <prefix>/lib/mysql/perl
use 5.008008;
use strict;
use warnings;
use Symbol qw(delete_package);
require Exporter;
our @ISA = qw(Exporter);
our @EXPORT_OK = qw( );
our @EXPORT = qw( test );
our $VERSION = '0.01';
our $DSN = ‘dbi:mysql:employees’;
use DBI;
use DBD::mysql;
sub test($)
{
my($emp_no) = @_;
my $dbh = DBI->connect($DSN, undef, undef) ||
die "Failed in call to DBI->connect, $!";
my $s = $dbh->prepare(
“SELECT * FROM employees WHERE emp_no=?”);
$s->execute(int $emp_no);
return $s->fetchrow_hashref;
}
1;

8. Reading Data
MariaDB [employees]> CREATE PROCEDURE employee(
-> empno INT)
-> DYNAMIC RESULT SETS 1
-> READS SQL DATA
-> LANGUAGE Perl
-> EXTERNAL NAME "ReadData::test";
Query OK, 0 rows affected (0.02 sec)
MariaDB [employees]> call employee(10034)G
*************************** 1. row
***************************
birth_date: 1962-12-29
emp_no: 10034
first_name: Bader
gender: M
hire_date: 1988-09-21
last_name: Swan
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
package ReadData;
# put this file in <prefix>/lib/mysql/perl
use 5.008008;
use strict;
use warnings;
use Symbol qw(delete_package);
require Exporter;
our @ISA = qw(Exporter);
our @EXPORT_OK = qw( );
our @EXPORT = qw( test );
our $VERSION = '0.01';
our $DSN = ‘dbi:mysql:employees’;
use DBI;
use DBD::mysql;
sub test($)
{
my($emp_no) = @_;
my $dbh = DBI->connect($DSN, undef, undef) ||
die "Failed in call to DBI->connect, $!";
my $s = $dbh->prepare(
“SELECT * FROM employees WHERE emp_no=?”);
$s->execute(int $emp_no);
return $s->fetchrow_hashref;
}
1;

9. Modifying Data
MariaDB [employees]> CREATE PROCEDURE
-> makesummary(
-> empno INT)
-> MODIFIES SQL DATA
-> LANGUAGE Perl
-> EXTERNAL NAME "ModifyData::test";
Query OK, 0 rows affected (0.00 sec)
MariaDB [employees]> call makesummary;
sub test()
{
my $dbh = DBI->connect($DSN, undef, undef) ||
die "Failed in call to DBI->connect, $!";
$dbh->begin_work or die $!;
my $ins = $dbh->prepare("INSERT INTO summary VALUES (?,?)");
my $emps = $dbh->selectall_arrayref(
"select emp_no, max(salary) salary from employees ".
"left join salaries using (emp_no) group by emp_no",
{ Slice => {} });
foreach my $emp (@$emps)
{
$ins->execute($emp->{emp_no}, $emp->{salary}) or die $!;
}
$dbh->commit or die $!;
return undef;
}

10. Modifying Data
MariaDB [employees]> CREATE PROCEDURE
-> makesummary(
-> empno INT)
-> MODIFIES SQL DATA
-> LANGUAGE Perl
-> EXTERNAL NAME "ModifyData::test";
Query OK, 0 rows affected (0.00 sec)
MariaDB [employees]> call makesummary;
Query OK, 0 rows affected (18.02 sec)
sub test()
{
my $dbh = DBI->connect($DSN, undef, undef) ||
die "Failed in call to DBI->connect, $!";
$dbh->begin_work or die $!;
my $ins = $dbh->prepare("INSERT INTO summary VALUES (?,?)");
my $emps = $dbh->selectall_arrayref(
"select emp_no, max(salary) salary from employees ".
"left join salaries using (emp_no) group by emp_no",
{ Slice => {} });
foreach my $emp (@$emps)
{
$ins->execute($emp->{emp_no}, $emp->{salary}) or die $!;
}
$dbh->commit or die $!;
return undef;
}

11. Modifying Data
MariaDB [employees]> CREATE PROCEDURE
-> makesummary(
-> empno INT)
-> MODIFIES SQL DATA
-> LANGUAGE Perl
-> EXTERNAL NAME "ModifyData::test";
Query OK, 0 rows affected (0.00 sec)
MariaDB [employees]> call makesummary;
Query OK, 0 rows affected (18.02 sec)
MariaDB [employees]> select count(*)
-> from summary;
+----------+
| count(*) |
+----------+
| 300024 |
+----------+
1 row in set (0.15 sec)
sub test()
{
my $dbh = DBI->connect($DSN, undef, undef) ||
die "Failed in call to DBI->connect, $!";
$dbh->begin_work or die $!;
my $ins = $dbh->prepare("INSERT INTO summary VALUES (?,?)");
my $emps = $dbh->selectall_arrayref(
"select emp_no, max(salary) salary from employees ".
"left join salaries using (emp_no) group by emp_no",
{ Slice => {} });
foreach my $emp (@$emps)
{
$ins->execute($emp->{emp_no}, $emp->{salary}) or die $!;
}
$dbh->commit or die $!;
return undef;
}

12. Modifying Data
MariaDB [employees]> CREATE PROCEDURE
-> makesummary(
-> empno INT)
-> MODIFIES SQL DATA
-> LANGUAGE Perl
-> EXTERNAL NAME "ModifyData::test";
Query OK, 0 rows affected (0.00 sec)
MariaDB [employees]> call makesummary;
Query OK, 0 rows affected (18.02 sec)
MariaDB [employees]> select count(*)
-> from summary;
+----------+
| count(*) |
+----------+
| 300024 |
+----------+
1 row in set (0.15 sec)
sub test()
{
my $dbh = DBI->connect($DSN, undef, undef) ||
die "Failed in call to DBI->connect, $!";
$dbh->begin_work or die $!;
my $ins = $dbh->prepare("INSERT INTO summary VALUES (?,?)");
my $emps = $dbh->selectall_arrayref(
"select emp_no, max(salary) salary from employees ".
"left join salaries using (emp_no) group by emp_no",
{ Slice => {} });
foreach my $emp (@$emps)
{
$ins->execute($emp->{emp_no}, $emp->{salary}) or die $!;
}
$dbh->commit or die $!;
return undef;
}
select statement - 2 seconds
300k inserts in 16 seconds
== 18k inserts per second

13. More than just procs
• CPAN is a large library...
• Can extend MariaDB’s functionality.
• How about using HTTP::Daemon?

14. Server Monitoring
sub daemon()
{
my $d = HTTP::Daemon->new(
LocalAddr => '127.0.0.1',
LocalPort => 8080,
) ||
die "Failed in call to HTTP::Daemon->new, $!";
my $dbh = DBI->connect("dbi:mysql:mysql", undef, undef) ||
die "Failed in call to DBI->connect, $!";
while (my $c = $d->accept)
{
while (my $r = $c->get_request)
{
if (exists $pages{$r->url->path})
{
$pages{$r->url->path}->($dbh, $c, $r);
}
else
{
$c->send_error(RC_NOT_FOUND);
}
}
$c->close;
undef $c;
}
}
What if we can use
HTTP::Daemon?

15. Server Monitoring
'/statusz' => sub {
my ($dbh,$c,$r) = @_;
return $c->send_error(RC_FORBIDDEN)
if $r->method ne 'GET';
my $sth = $dbh->prepare_cached(q{
SELECT VARIABLE_NAME name, VARIABLE_VALUE value
FROM INFORMATION_SCHEMA.GLOBAL_STATUS
}, { Slice => {} });
$sth->execute() || die $sth->errstr;
my $response = HTTP::Response->new(200, undef,
HTTP::Headers->new(
Content_Type => "application/json",
));
my $result = {};
while (my $row = $sth->fetchrow_arrayref)
{
$result->{$row->[0]} = $row->[1];
}
$response->add_content(to_json($result,
{ ascii => 1, pretty => 1 }));
return $c->send_response($response);
},
Fetching current
server status could be
as simple as fetching
http://127.0.0.1/statusz

16. Status
• Code hosted at LaunchPad.
• Contributing to MariaDB 10.0 soon.
• Stuff needs to be tidied up.
• Future steps include better Table Functions.