=pod

=head1 NAME

DBIx::Migration - Seamless database schema up- and downgrades

=head1 SYNOPSIS

  use DBIx::Migration ();

  my $m = DBIx::Migration->new(
    dsn => 'dbi:SQLite:~/Projects/myapp/db/myapp.db'
  );

  # Get current version from database
  my $version = $m->version;

  # Set directory before applying migrations
  $m->dir( '~/Projects/myapp/db/migrations' );

  # Migrate database to version 1
  $m->migrate( 1 );

  # Migrate database to the latest version
  $m->migrate;

  # ~/Projects/myapp/db/migrations/schema_1_up.sql
  CREATE TABLE foo (
    id INTEGER PRIMARY KEY,
    bar TEXT
  );

  # ~/Projects/myapp/db/migrations/schema_1_down.sql
  DROP TABLE foo;

  # ~/Projects/myapp/db/migrations/schema_2_up.sql
  CREATE TABLE bar (
    id INTEGER PRIMARY KEY,
    baz TEXT
  );

  # ~/Projects/myapp/db/migrations/schema_2_down.sql
  DROP TABLE bar;

=head1 DESCRIPTION

This module provides seamless database schema up- and downgrades. The
implementation is based on migrations. A migration is a C<.sql> script.
Although not mandatory the script name begins with a prefix like for example
C<schema_>. It follows a version number that is a positive integer. After an
C<_> (underscore) character the script name ends with the migration type that
is either C<up> or C<down>. Migrations are stored in a directory and are
applied in order to a database. Usually the version number of the first
migration is 1. The version numbers of the other migrations have to be
ascending without gaps.

During processing the content of each migration is read with the C<binmode> of
C<:raw> into a scalar. The content is split into sections using the default SQL
delimiter C<;> (semicolon). Each section is executed independently. All related
sections are encapsulated in a database transaction.  If a migration embeds
stored logic containing one or more semicolons (a PostgreSQL trigger function
for example), the C<migrate()> method incorrectly splits the migration into
sections, causing an error. You can set a different delimiter to overcome this
problem. Add the C<dbix_migration_delimiter> annotation as an SQL comment to
the migration

  -- dbix_migration_delimiter: /
  ...

The annotation has to be specified in the first line. The delimiter has to be
a single printable ASCII character, excluding the space character. In the
previous example it is the C</> (slash) character.

=head1 METHODS

=over

=item $self->BUILD( $args )

Validate object.

=item $self->debug( $debug )

Enable/disable debug messages.

=item $self->dir( $dir )

Get/set-once directory that contains migrations.

=item $self->dsn

Get data source name.

=item $self->dbh

Get database handle.

=item $self->migrate( $version )

Migrate database to version. Returns true in case of success; otherwise false.
If called without the version argument the latest migration version will be
used.

=item $self->password

Get database password.

=item $self->username

Get database username.

=item $self->version

Get migration version from database. Will be C<undef> if no migration has taken
place yet. The version is stored in the table C<dbix_migration>. The name of
this table may change in the future so don't rely on it.

=back

=head1 SEE ALSO

=over

=item * L<Liquibase endDelimiter|https://docs.liquibase.com/change-types/enddelimiter-sql.html>

=back

=head1 TODOS

=over

=item *

Implement proper logging. Printing debug information to stdout conflicts with
the stdout output of C<DBIx::Migration::CLI>.

=back

=head1 AUTHOR

Sebastian Riedel, <kraihx@gmail.com>

=head1 CONTRIBUTORS

Dan Sully, <dan+github@sully.org>

Marcus Ramberg, <marcus@nordaaker.com>

Steven Jenkin, <sjenkin@venda.com>

Sven Willenbuecher, <sven.willenbuecher@gmx.de>

=head1 COPYRIGHT

Copyright 2004-2005 Sebastian Riedel. All rights reserved.

This program is free software, you can redistribute it and/or modify it under
the same terms as Perl itself.

=cut
