DBSchema-Normalizer

WELCOME TO THE NORMALIZER

DBSchema::Normalizer is a Perl module to help you through the process of transforming a MySQL database table from 1st to 2nd (and eventually 3rd) normal form.

It is a tool for the database designer, who is supposed to know what it has to be done. The Normalizer does not give you support for deciding which tables need to be normalized and which fields to move across tables.

What you get from DBSchema::Normalizer is a quick way of performing the operations you have identified as needed. You can also have a certain degree of flexibility, since the Normalizer can also simulate the operation instead of executing it, giving you plenty of information to decide whether you want to go on or not.

DATABASE THEORY

You won't find database theory here. There are plenty of other places where to get such information.
(http://www.palslib.com/Fundamentals/Database_Design.html is one of them. A sort of crash course on normalization with an elegant example on how to face this problem from a practical side can be found at www.perlmonks.org/index.pl?node_id=129454)

I assume that you know what needs to be done, and that this knowledge comes to you by either a regular course or long practice. Either way, lacking the room to spread around some base theory, I feel that, having some hands-on examples on normalization will help you gather some insight on this process, which is too often explained only from a designer point of view, leaving helpless the ones with practical needs.

INSTALLATION

The usual procedure.

        perl Makefile.PL
        make
        make install
        make test

USAGE

     use DBSchema::Normalizer;
     my $norm = DBSchema::Normalizer->new (\%param_hash); 
     $norm->do();

%param_hash must contain at least the information to connect successfully to a mysql database through the DBI. For example, the following two calls are equivalent. The first one assumes that you have a MySQL configuration file (.my.cnf) in your home directory. This syntax is Unix specific. For other operating systems, please refer to the MySQL manual.

        # using a configuration file
        my $norm = DBSchema::Normalizer->new ({
            DSN           => "DBI:mysql:music;host=localhost;"
                             . "mysql_read_default_file=$ENV{HOME}/.my.cnf", 
            src_table     => "MP3",
            index_field   => "album_id",
            lookup_fields => "artist,album,genre",
            lookup_table  => "tmp_albums", 
            dest_table    => "songs",
            copy_indexes  =>  1,
            simulate      =>  1
         });

        # passing username and password explicitly
        my $norm = DBSchema::Normalizer->new ({
            DSN           => "DBI:mysql:music;host=localhost"
            username      => "itsme",
            password      => "secret",
            src_table     => "MP3",
            index_field   => "album_id",
            lookup_fields => "artist,album,genre",
            lookup_table  => "tmp_albums", 
            dest_table    => "songs",
            copy_indexes  =>  1,
            simulate      =>  1
         });

Examples of usage can be found in the DBSchema::Normalizer module itself

perldoc DBSchema::Normalizer

DISTRIBUTION LIST

     Changes                           Version log
     MANIFEST                          List of files in this package
     Makefile.PL                       (non) installation script
     Normalizer.pm                     The Module Itself
     README                            this file
     test.pl                           test dependencies for DBSchema::Normalizer
     docs/Normalizer.html              documentation in HTML format
     docs/Normalizer.pod               documentation in POD format
     docs/Normalizer.txt               plain text documentation
     examples/mp3.mysql                sample database script MySQL 
     examples/test_normalizer.pl       test with sample database

DOCUMENTATION

All the documentation is embedded into the module itself in POD format, which you can enjoy by typing

perldoc DBSchema::Normalizer

I decided to spare you some milliseconds of CPU usage (and waste some kilobytes of mass storage in the process) and therefore you also have the same documentation in the following formats:

        Normalizer.pod  POD format, in case you have some CPU cycles to spare and want to
                        produce your own docs.
                    
        Normalizer.html Browsable version
    
        Normalizer.txt  If you are using a limited resources connection, or if you just 
                        like it, there is a plain text version.

And of course the best documentation is the code itself, which you are welcome to peek at. However, try to use only the documented subs and leave the private ones alone (the ones starting by "_"). Please refer to the normal documentation, under "Architecture," to have an idea of the terrible things that expect you if you don't follow my advice.

DEPENDENCIES AND REQUIREMENTS

Normalizer.pm is built with direct references to MySQL databases, which are accessed through DBI and DBD::mysql. Failing those dependencies, it won't work. You may get the modules from the CPAN, but to try the Normalizer you must have access to a MySQL database, either in your computer or over a network connection.

Your account must have SELECT, INSERT, CREATE and DROP privileges in order to use the Normalizer.

SETTING UP THE EXAMPLES

DBSchema::Normalizer is distributed into a compressed package, containing, among other things, two files that will let you experience a close encounter with the practical side of Data Designing.

        mp3.mysql
        test_normalizer.pl

mp3.mysql is a sample from a MP3 table. It contains non-normalized data referring to MP3 files. To install it, you need to have a valid account to a MySQL database (with SELECT, CREATE, DROP and INSERT privileges) and run, at your shell prompt

$ mysql [-u username] [-p] [-h hostname] < mp3.mysql

This command will create a database "music" (if it does not exists,) and a table "MP3" populated with a few dozen records.

That done, if you have a MySQL configuration file with username and password in your home directory, you can run the test_normalizer.pl without further steps. If you don't, or if you aren't using "localhost", then you need to edit the script and enter your DSN.

The unedited example will not perform any changes in your database. It will run in "Simulation mode." (refer to the documentation for details.) You can use its output for the purposes that suit you better. If you turn simulation mode off ({simulate => 0}) then the Normalizer will act on your behalf.

Make sure to read the documentation and to understand what is behind it before venturing into something you may regret.

Note: Since I don't want to disrupt existing data, the MP3 table is not created if it already exists. If this is the case, please edit both the SQL and the Perl scripts to adjust them to your needs.

AUTHOR

My contact for bugs, comments, advice: gmax@karma.oltrelinux.com