Monday, October 4, 2010

Connecting to SQL Server from OS X perl

I've been spending my coding time in the offhours working on Perl instead of Ruby. My coding time in general has been very limited, which is part of the reason for the length of time between updates. :)

My latest project is to pull data out of a Microsoft SQL Server database for analysis. I'm using perl for various reasons: I need a crossplatform environment, and I need certain libraries that only work on perl. Some of the target users for my code run on Windows.

I know that Ruby runs on Windows but it's not the platform of choice for Ruby developers. The vast majority seem to develop either on OS X or Linux. So Ruby on Windows isn't at the maturity that ActiveState perl is on Windows.

In fact, I don't even run native perl anymore on my MacBook Pro. I've switched over to ActiveState perl because I don't need to compile anything every time I want to install new CPAN libraries. And because it's ActiveState, I'm that much more confident it will work on other platforms.

The bottom line is that perl makes the most sense for what I'm trying to do. I vastly prefer ruby to perl but I don't mind working in perl when I have to.

So how to connect to SQL Server from perl? My first thought was that I could use ODBC. My research quickly took me to DBD::ODBC in CPAN. After spending some time Googling for other examples and trying to get it working, I wasn't getting anywhere.

It took me some more research until I realized that DBD::ODBC is only one piece of the whole picture. I also need an ODBC driver manager and an ODBC driver.

The two main ODBC driver managers for Unix/Linux are unixODBC and iODBC. Fortunately, iODBC is already included in OS X.

For the ODBC driver itself, I wound up using FreeTDS. Because FreeTDS is only available as source code, I had to use MacPorts to download and compile the code. MacPorts installs everything in /opt/local by default.

So here was the process:

1. Install FreeTDS. If you are using ActiveState perl as I am, you must force MacPorts to build FreeTDS as 32-bit because ActiveState is 32-bit only. If you go with the default of compiling FreeTDS as 64-bit (or x86_64) then you will get this error when you call the FreeTDS library code from ActiveState perl:

[iODBC][Driver Manager]dlopen(/opt/local/lib/libtdsodbc.so, 6): no suitable image found. Did find:
/opt/local/lib/libtdsodbc.so: mach-o, but wrong architecture (SQL-00000) at test.pl line 26

So to fix this error, edit the MacPorts configuration file:

sudo vi /opt/local/etc/macports/macports.conf

Uncomment this line:

set build_arch i386

Once you build and install FreeTDS, ensure that you can use it to talk with the database. I used tsql:

TDSVER=8.0 tsql -H 10.10.10.1 -p 1433 -U 'DOMAIN\user' -P 'password'

2. After you do this, test your ODBC driver manager and driver. I used iODBC because it comes with OS X. It comes with a utility called iodbctest. I used similar parameters to tsql when testing:

iodbctest "Driver=/opt/local/lib/libtdsodbc.so;Server=10.10.10.1;Port=1433;TDS_Version=8.0;uid=DOMAIN\user;pwd=password;Database=Database"

Note a few things:
  • Other sites tell you to make entries in odbc.ini, odbcinst.ini, or freetds.conf. If you set all parameters on the command line then you don't need to tweak these other config files.
  • The Driver parameter is set to the full path for libtdsodbc.so. This is the actual ODBC driver. The name or path may differ, depending on your OS and ODBC driver software.
  • I haven't created an ODBC data source on my Windows SQL Server host so far. Some sites say you need to do this but I found it worked without this.
3. Use the perl code with DBD::ODBC to call the database. Here's some sample code. Note how I first populate the data source ($dsn) with the parameters I used with iodbctest, and then I pass this to the DBI->connect method.
#!/usr/bin/perl

use strict;
use DBI;

my $user = 'user';
my $pass = 'password';
my $driver = "/opt/local/lib/libtdsodbc.so";
my $db_server = "10.10.10.1";
my $db_name = 'Database';
my $port = 1433;
my $tds_version = "8.0";

my $dsn = join "", ("dbi:ODBC:",
   "Driver=$driver;",
   "Server=$db_server;",
   "Port=$port;",
   "UID=$user;",
   "PWD=$pass;",
   "TDS_Version=$tds_version;",
   "Database=$db_name",
);

my $db_options = {PrintError => 1, RaiseError => 1, AutoCommit => 0, };

my $dbh = DBI->connect($dsn, $db_options);
$dbh->{LongReadLen} = 32768;
my $sql = qq/select * from table/;
my $sth = $dbh->prepare($sql);
$sth->execute();
my @row;
while (@row = $sth->fetchrow_array) {
    print join(", ", @row), "\n";
}
Note on 12/29/10: I added this after the DBI->connect: $dbh->{LongReadLen} = 32768; I was getting "Data truncated" errors when accessing ntext fields. This link was a real help and helped me solve the problem.

1 Comments:

Blogger a said...

Hi,

i'm trying to the same as you above but when i try and test my connection with iODBC i get the error you warn about above even after set build_arch i386. I checked this with file libtdsodbc.so. Do you know why this might be happening?

Thanks

May 26, 2011 at 11:54 AM  

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