utf-8 string getting truncated in MySQL table using Perl/DBI

Question

I am trying to write utf-8 strings to a MySQL table using perl/DBI. For some reason the string is getting truncated at the first non-ascii character.

For example, if I set up the following table:

CREATE DATABASE testdb DEFAULT CHARSET=utf8;
CREATE TABLE testdb.testtable (textval CHAR(30)) DEFAULT CHARSET=utf8;

And then run the following perl code:

#!/usr/bin/perl
use strict;
use DBI;
my $dbh = DBI->connect('DBI:mysql:host=localhost;database=testdb', 'testuser', 'somepassword', {mysql_enable_utf8 => 1}) or die $DBI::errstr;
$dbh->do('SET NAMES utf8');
$dbh->do("INSERT INTO testtable (textval) VALUES ('the N\xFCrburgring')");

It actually writes "the N". (when it should be writing "the Nürburgring")

Looking in the MySQL query log, I see this:

271 Query INSERT INTO testtable (textval) VALUES ('the Nürburgring')

So the string is reaching the DB server intact.

If I enter the same query directly in the MySQL console:

INSERT INTO testtable (textval) VALUES ('the Nürburgring');

The entire string is written correctly. Any idea what I'm doing wrong?

Answer 1

You set the attribute mysql_enable_utf8, so you promised the interface that you will give it a Perl string of characters. However, this is a buffer of octets in Latin1 encoding.

use Devel::Peek qw(Dump);
Dump "the N\xfcrburgring";
#  FLAGS = (POK,READONLY,pPOK)
#  PV = 0x208e4f0 "the N\374rburgring"\0

The fix is simple. Either notate literal characters without \x escapes, use the utf8 pragma to tell Perl that your source code is in UTF-8 and save the source in UTF-8 encoding with your editor…

use utf8;
use Devel::Peek qw(Dump);
Dump "the Nürburgring";
#  FLAGS = (POK,READONLY,pPOK,UTF8)
#  PV = 0x20999f0 "the N\303\274rburgring"\0 [UTF8 "the N\x{fc}rburgring"]

… or decode the octets into a string. Most of the time you're dealing not with literals, but with data coming from the outside, so better learn about the whole topic of encoding.

use Encode qw(decode);
use Devel::Peek qw(Dump);
Dump decode 'Latin1', "the N\xfcrburgring";
#  FLAGS = (TEMP,POK,pPOK,UTF8)
#  PV = 0x208f6b0 "the N\303\274rburgring"\0 [UTF8 "the N\x{fc}rburgring"]