NAME

       DBIx::Class::DeploymentHandler::Manual::Intro - Introduction to DBIx::Class::DeploymentHandler

Why is DBIx::Class::DeploymentHandler worth using?

       The most obvious reasons for using DBIx::Class::DeploymentHandler are that it can run multiple SQL
       scripts as well as Perl scripts, unlike DBIx::Class::Schema::Versioned, which only allows for a single
       SQL script.  It is also extremely extensible, and is an opportunity for a break from backwards
       compatibility, so some regrettable decisions are avoided.

Sample database

       Follow DBIx::Class::Manual::Intro except for the parts setting up the database.  After you are done, You
       should have the following files.

        MyDatabase/
        |-- Main
        |   |-- Result
        |   |   |-- Artist.pm
        |   |   |-- Cd.pm
        |   |   `-- Track.pm
        |   `-- ResultSet
        `-- Main.pm

       Add a line like the following in your MyDatabase::Main file:

        our $VERSION = 1;

       or if you are using a newer Perl you can use the prettier syntax:

        package MyDatabase::Main 1;

       By default DBIx::Class::DeploymentHandler only uses integers for versions, this makes versioning much
       simpler for figuring out what version is next (or previous.) However, if you are using decimal numbers
       for versioning, you will need to create a separate DeploymentHandler class, as per
       DBIx::Class::DeploymentHandler::Cookbook::CustomResultSource, and set the VersionHandler class_name from
       Monotonic to ExplicitVersions or DatabaseToSchemaVersions, as these handle version numbers as strings
       instead of integers.

install.pl

       Our first script, "install.pl" reads our schema file and creates the tables in the database.

        #!/usr/bin/env perl

        use strict;
        use warnings;
        use aliased 'DBIx::Class::DeploymentHandler' => 'DH';
        use Getopt::Long;
        use FindBin;
        use lib "$FindBin::Bin/../lib";
        use MyDatabase::Main;

        my $force_overwrite = 0;

        unless ( GetOptions( 'force_overwrite!' => \$force_overwrite ) ) {
            die "Invalid options";
        }

        my $schema = MyDatabase::Main->connect('dbi:SQLite:mydb.db');

        my $dh = DH->new(
            {
                schema              => $schema,
                script_directory    => "$FindBin::Bin/../dbicdh",
                databases           => 'SQLite',
                sql_translator_args => { add_drop_table => 0 },
                force_overwrite     => $force_overwrite,
            }
        );

        $dh->prepare_install;
        $dh->install;

   dbicdh - Our migration scripts
       Running "install.pl" should create the following:

        dbicdh/
        |-- SQLite
        |   `-- deploy
        |       `-- 1
        |           `-- 001-auto.sql
        `-- _source
            `-- deploy
                `-- 1
                    `-- 001-auto.yml

       You may wish to turn on debug logging before running this script by setting the environment variable
       "DBICDH_TRACE" to 1.

       001-auto.sql

       DBIx::Class::DeploymentHandler automatically generates SQL from our schema that is suitable for SQLite

       001-auto.yml

       This contains all of the raw information about our schema that is then translated into the sql.

       Population

       To truly take advantage of all DBIx::Class::DeploymentHandler offers, you should probably be using it for
       population.  To do that all you need to do is create a file called
       "dbicdh/_common/deploy/1/create_artists.pl":

         sub {
            my $schema = shift;
            $schema->resultset('Artist')->populate([
               ['artistid', 'name'],
               [1,          'Marillion'],
               [2,          'The Moutain Goats'],
               [3,          'Ladyhawke'],
            ]);
         };

Upgrading

       Add a line to MyDatabase/Main/Result/Cd.pm below

        __PACKAGE__->add_columns(qw/ cdid artist title /);

       with

        __PACKAGE__->add_column(isbn => { is_nullable => 1 });

       Aside: It must be nullable or have a default - otherwise the upgrade will fail for logical reasons.  To
       be clear, if you add a column to a database and it is not nullable and has no default, what will the
       existing rows contain for that column?

       Now you need to modify the schema version in your MyDatabase::Main file to tell
       DBIx::Class::DeploymentHandler the new schema version number. You will want to remember the earlier
       advice about integer version numbers.

        our $VERSION = 2;

       So here is our next script, "upgrade.pl":

        #!/usr/bin/env perl
        use strict;
        use warnings;
        use aliased 'DBIx::Class::DeploymentHandler' => 'DH';
        use FindBin;
        use lib "$FindBin::Bin/../lib";
        use MyDatabase::Main;
        my $schema = MyDatabase::Main->connect('dbi:SQLite:mydb');

        my $dh = DH->new({
           schema              => $schema,
           script_directory    => "$FindBin::Bin/../dbicdh",
           databases           => 'SQLite',
           sql_translator_args => { add_drop_table => 0 },
        });

        $dh->prepare_deploy;
        $dh->prepare_upgrade({ from_version => 1, to_version => 2});
        $dh->upgrade;

       Our script directory now looks like:

         dbicdh/
         |-- SQLite
         |   |-- deploy
         |   |   |-- 1
         |   |   |   `-- 001-auto.sql
         |   |   `-- 2
         |   |       `-- 001-auto.sql
         |   `-- upgrade
         |       `-- 1-2
         |           `-- 001-auto.sql
         `-- _source
             `-- deploy
                 |-- 1
                 |   `-- 001-auto.yml
                 `-- 2
                     `-- 001-auto.yml

       The new "deploy/001-auto.sql" and "deploy/001-auto.yml" files are the state of the db as at that version.
       The "upgrade/1-2/001-auto.sql" file is the most interesting one; it is what gets your database from
       version 1 to 2.

       And again, you can create a Perl file like we did previously with the deploy stage.

AUTHOR

       Arthur Axel "fREW" Schmidt <frioux+cpan@gmail.com>

COPYRIGHT AND LICENSE

       This software is copyright (c) 2019 by Arthur Axel "fREW" Schmidt.

       This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5
       programming language system itself.