Executive summary: Do not upgrade DBD::DB2 unless you have verified that your application works as expected with the new version. There is no test suite to help you detect errors or unexpected results.

DBD::DB2 is the database driver for IBM DB2 UDB. The database runs on a variety of platforms, including Unix (AIX), Windows, Linux and z/OS.

To my big surprise, DBD::DB2 has no real test suite, and recently there was discovered a bug where newer versions of the module return incorrect results for certain versions of the database for the clob data-type.

I claim that this bug could have easily been discovered during development if the module had even the simplest of tests (which in this case would be to insert a value, then retrieve the value, and test for equality), e.g. like this: 

  # -- Prepare test data: 
  # create table dbddb2_clob (
  #    id        integer   not null,
  #    data      clob      not null  ,
  #    constraint pk_dbddb2_clob primary key (id)
  # );
  # insert into dbddb2_clob values (1, 'fubar_clob');

  my $sth = $dbh->prepare(q{select id,data from dbddb2_clob});
  $sth->execute();
  is_deeply($sth->fetchall_arrayref(), 
            [[1,'fubar_clob']], 
            q{Expect 1 row (1,'fubar_clob') returned});

[download]

Citing dhoss (here):

The benefit of test driven development is, you *know* your code will work before you ship it.
I will turn that around: The benefit of test driven development is, you detect when your code does not work as expected.

Let this serve as a reminder of how important it is to have a test suite, and a kind request to the module maintainers to start building one.

Update Fri Mar 20 12:21:46 CET 2009: The IBM OPENDEV team has responded to the bug and produced a patch that seems to fix the problem, and they deserve credit for doing so.

In reply to DBD::DB2 truncates clob values - on the importance testing by andreas1234567

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