Add transforms for column renames etc

[dbsrgits/DBIx-Class-DeploymentHandler.git] / lib / DBIx / Class / DeploymentHandler / DeployMethod / SQL / Translator.pm

package DBIx::Class::DeploymentHandler::DeployMethod::SQL::Translator;
use Moose;

# ABSTRACT: Manage your SQL and Perl migrations in nicely laid out directories

use autodie;
use Carp qw( carp croak );
use DBIx::Class::DeploymentHandler::Logger;
use Log::Contextual qw(:log :dlog), -default_logger =>
  DBIx::Class::DeploymentHandler::Logger->new({
    env_prefix => 'DBICDH'
  });

use Method::Signatures::Simple;
use Try::Tiny;

use SQL::Translator;
require SQL::Translator::Diff;

require DBIx::Class::Storage;   # loaded for type constraint
use DBIx::Class::DeploymentHandler::Types;

use File::Path 'mkpath';
use File::Spec::Functions;

with 'DBIx::Class::DeploymentHandler::HandlesDeploy';

has ignore_ddl => (
  isa      => 'Bool',
  is       => 'ro',
  default  => undef,
);

has schema => (
  isa      => 'DBIx::Class::Schema',
  is       => 'ro',
  required => 1,
);

has storage => (
  isa        => 'DBIx::Class::Storage',
  is         => 'ro',
  lazy_build => 1,
);

method _build_storage {
  my $s = $self->schema->storage;
  $s->_determine_driver;
  $s
}

has sql_translator_args => (
  isa => 'HashRef',
  is  => 'ro',
  default => sub { {} },
);
has script_directory => (
  isa      => 'Str',
  is       => 'ro',
  required => 1,
  default  => 'sql',
);

has databases => (
  coerce  => 1,
  isa     => 'DBIx::Class::DeploymentHandler::Databases',
  is      => 'ro',
  default => sub { [qw( MySQL SQLite PostgreSQL )] },
);

has txn_wrap => (
  is => 'ro',
  isa => 'Bool',
  default => 1,
);

has schema_version => (
  is => 'ro',
  isa => 'Str',
  lazy_build => 1,
);

# this will probably never get called as the DBICDH
# will be passing down a schema_version normally, which
# is built the same way, but we leave this in place
method _build_schema_version { $self->schema->schema_version }

method __ddl_consume_with_prefix($type, $versions, $prefix) {
  my $base_dir = $self->script_directory;

  my $main    = catfile( $base_dir, $type      );
  my $generic = catfile( $base_dir, '_generic' );
  my $common  =
    catfile( $base_dir, '_common', $prefix, join q(-), @{$versions} );

  my $dir;
  if (-d $main) {
    $dir = catfile($main, $prefix, join q(-), @{$versions})
  } elsif (-d $generic) {
    $dir = catfile($generic, $prefix, join q(-), @{$versions});
  } else {
    croak "neither $main or $generic exist; please write/generate some SQL";
  }

  my %files;
  try {
     opendir my($dh), $dir;
     %files =
       map { $_ => "$dir/$_" }
       grep { /\.(?:sql|pl|sql-\w+)$/ && -f "$dir/$_" }
       readdir $dh;
     closedir $dh;
  } catch {
    die $_ unless $self->ignore_ddl;
  };
  if (-d $common) {
    opendir my($dh), $common;
    for my $filename (grep { /\.(?:sql|pl)$/ && -f catfile($common,$_) } readdir $dh) {
      unless ($files{$filename}) {
        $files{$filename} = catfile($common,$filename);
      }
    }
    closedir $dh;
  }

  return [@files{sort keys %files}]
}

method _ddl_preinstall_consume_filenames($type, $version) {
  $self->__ddl_consume_with_prefix($type, [ $version ], 'preinstall')
}

method _ddl_schema_consume_filenames($type, $version) {
  $self->__ddl_consume_with_prefix($type, [ $version ], 'schema')
}

method _ddl_protoschema_up_consume_filenames($versions) {
  my $base_dir = $self->script_directory;

  my $dir = catfile( $base_dir, '_protoschema', 'up', join q(-), @{$versions});

  return [] unless -d $dir;

  opendir my($dh), $dir;
  my %files = map { $_ => "$dir/$_" } grep { /\.pl$/ && -f "$dir/$_" } readdir $dh;
  closedir $dh;

  return [@files{sort keys %files}]
}

method _ddl_protoschema_down_consume_filenames($versions) {
  my $base_dir = $self->script_directory;

  my $dir = catfile( $base_dir, '_protoschema', 'down', join q(-), @{$versions});

  return [] unless -d $dir;

  opendir my($dh), $dir;
  my %files = map { $_ => "$dir/$_" } grep { /\.pl$/ && -f "$dir/$_" } readdir $dh;
  closedir $dh;

  return [@files{sort keys %files}]
}

method _ddl_protoschema_produce_filename($version) {
  my $dirname = catfile( $self->script_directory, '_protoschema', 'schema',  $version );
  mkpath($dirname) unless -d $dirname;

  return catfile( $dirname, '001-auto.yml' );
}

method _ddl_schema_produce_filename($type, $version) {
  my $dirname = catfile( $self->script_directory, $type, 'schema', $version );
  mkpath($dirname) unless -d $dirname;

  return catfile( $dirname, '001-auto.sql' );
}

method _ddl_schema_up_consume_filenames($type, $versions) {
  $self->__ddl_consume_with_prefix($type, $versions, 'up')
}

method _ddl_schema_down_consume_filenames($type, $versions) {
  $self->__ddl_consume_with_prefix($type, $versions, 'down')
}

method _ddl_schema_up_produce_filename($type, $versions) {
  my $dir = $self->script_directory;

  my $dirname = catfile( $dir, $type, 'up', join q(-), @{$versions});
  mkpath($dirname) unless -d $dirname;

  return catfile( $dirname, '001-auto.sql' );
}

method _ddl_schema_down_produce_filename($type, $versions, $dir) {
  my $dirname = catfile( $dir, $type, 'down', join q(-), @{$versions} );
  mkpath($dirname) unless -d $dirname;

  return catfile( $dirname, '001-auto.sql');
}

method _run_sql_array($sql) {
  my $storage = $self->storage;

  $sql = [grep {
    $_ && # remove blank lines
    !/^(BEGIN|BEGIN TRANSACTION|COMMIT)/ # strip txn's
  } map {
    s/^\s+//; s/\s+$//; # trim whitespace
    join '', grep { !/^--/ } split /\n/ # remove comments
  } @$sql];

  Dlog_trace { "Running SQL $_" } $sql;
  foreach my $line (@{$sql}) {
    $storage->_query_start($line);
    # the whole reason we do this is so that we can see the line that was run
    try {
      $storage->dbh_do (sub { $_[1]->do($line) });
    }
    catch {
      die "$_ (running line '$line')"
    }
    $storage->_query_end($line);
  }
  return join "\n", @$sql
}

method _run_sql($filename) {
  log_debug { "Running SQL from $filename" };
  return $self->_run_sql_array($self->_read_sql_file($filename));
}

method _run_perl($filename) {
  log_debug { "Running Perl from $filename" };
  my $filedata = do { local( @ARGV, $/ ) = $filename; <> };

  no warnings 'redefine';
  my $fn = eval "$filedata";
  use warnings;
  Dlog_trace { "Running Perl $_" } $fn;

  if ($@) {
    carp "$filename failed to compile: $@";
  } elsif (ref $fn eq 'CODE') {
    $fn->($self->schema)
  } else {
    carp "$filename should define an anonymouse sub that takes a schema but it didn't!";
  }
}

method _run_sql_and_perl($filenames, $sql_to_run) {
  my @files   = @{$filenames};
  my $guard   = $self->schema->txn_scope_guard if $self->txn_wrap;

  $self->_run_sql_array($sql_to_run) if $self->ignore_ddl;

  my $sql = ($sql_to_run)?join ";\n", @$sql_to_run:'';
  FILENAME:
  for my $filename (@files) {
    if ($self->ignore_ddl && $filename =~ /^[^_]*-auto.*\.sql$/) {
      next FILENAME
    } elsif ($filename =~ /\.sql$/) {
       $sql .= $self->_run_sql($filename)
    } elsif ( $filename =~ /\.pl$/ ) {
       $self->_run_perl($filename)
    } else {
      croak "A file ($filename) got to deploy that wasn't sql or perl!";
    }
  }

  $guard->commit if $self->txn_wrap;

  return $sql;
}

sub deploy {
  my $self = shift;
  my $version = (shift @_ || {})->{version} || $self->schema_version;
  log_info { "deploying version $version" };
  my $sqlt_type = $self->storage->sqlt_type;
  my $sql;
  if ($self->ignore_ddl) {
     $sql = $self->_sql_from_yaml({},
       '_ddl_protoschema_produce_filename', $sqlt_type
     );
  }
  return $self->_run_sql_and_perl($self->_ddl_schema_consume_filenames(
    $sqlt_type,
    $version,
  ), $sql);
}

sub preinstall {
  my $self         = shift;
  my $args         = shift;
  my $version      = $args->{version}      || $self->schema_version;
  log_info { "preinstalling version $version" };
  my $storage_type = $args->{storage_type} || $self->storage->sqlt_type;

  my @files = @{$self->_ddl_preinstall_consume_filenames(
    $storage_type,
    $version,
  )};

  for my $filename (@files) {
    # We ignore sql for now (till I figure out what to do with it)
    if ( $filename =~ /^(.+)\.pl$/ ) {
      my $filedata = do { local( @ARGV, $/ ) = $filename; <> };

      no warnings 'redefine';
      my $fn = eval "$filedata";
      use warnings;

      if ($@) {
        carp "$filename failed to compile: $@";
      } elsif (ref $fn eq 'CODE') {
        $fn->()
      } else {
        carp "$filename should define an anonymous sub but it didn't!";
      }
    } else {
      croak "A file ($filename) got to preinstall_scripts that wasn't sql or perl!";
    }
  }
}

method _sqldiff_from_yaml($from_version, $to_version, $db, $direction) {
  my $dir       = $self->script_directory;
  my $sqltargs = {
    add_drop_table => 1,
    ignore_constraint_names => 1,
    ignore_index_names => 1,
    %{$self->sql_translator_args}
  };

  my $source_schema;
  {
    my $prefilename = $self->_ddl_protoschema_produce_filename($from_version, $dir);

    # should probably be a croak
    carp("No previous schema file found ($prefilename)")
       unless -e $prefilename;

    my $t = SQL::Translator->new({
       %{$sqltargs},
       debug => 0,
       trace => 0,
       parser => 'SQL::Translator::Parser::YAML',
    });

    my $out = $t->translate( $prefilename )
      or croak($t->error);

    $source_schema = $t->schema;

    $source_schema->name( $prefilename )
      unless  $source_schema->name;
  }

  my $dest_schema;
  {
    my $filename = $self->_ddl_protoschema_produce_filename($to_version, $dir);

    # should probably be a croak
    carp("No next schema file found ($filename)")
       unless -e $filename;

    my $t = SQL::Translator->new({
       %{$sqltargs},
       debug => 0,
       trace => 0,
       parser => 'SQL::Translator::Parser::YAML',
    });

    my $out = $t->translate( $filename )
      or croak($t->error);

    $dest_schema = $t->schema;

    $dest_schema->name( $filename )
      unless $dest_schema->name;
  }

  my $transform_files_method =  "_ddl_protoschema_${direction}_consume_filenames";
  my $transforms = $self->_coderefs_per_files(
    $self->$transform_files_method([$from_version, $to_version])
  );
  $_->($source_schema, $dest_schema) for @$transforms;

  return [SQL::Translator::Diff::schema_diff(
     $source_schema, $db,
     $dest_schema,   $db,
     $sqltargs
  )];
}

method _sql_from_yaml($sqltargs, $from_file, $db) {
  my $schema    = $self->schema;
  my $version   = $self->schema_version;

  my $sqlt = SQL::Translator->new({
    add_drop_table          => 0,
    parser                  => 'SQL::Translator::Parser::YAML',
    %{$sqltargs},
    producer => $db,
  });

  my $yaml_filename = $self->$from_file($version);

  my @sql = $sqlt->translate($yaml_filename);
  if(!@sql) {
    carp("Failed to translate to $db, skipping. (" . $sqlt->error . ")");
    return undef;
  }
  return \@sql;
}

sub _prepare_install {
  my $self      = shift;
  my $sqltargs  = { %{$self->sql_translator_args}, %{shift @_} };
  my $from_file = shift;
  my $to_file   = shift;
  my $dir       = $self->script_directory;
  my $databases = $self->databases;
  my $version   = $self->schema_version;

  foreach my $db (@$databases) {
    my $sql = $self->_sql_from_yaml($sqltargs, $from_file, $db ) or next;

    my $filename = $self->$to_file($db, $version, $dir);
    if (-e $filename ) {
      carp "Overwriting existing DDL file - $filename";
      unlink $filename;
    }
    open my $file, q(>), $filename;
    print {$file} join ";\n", @$sql;
    close $file;
  }
}

sub _resultsource_install_filename {
  my ($self, $source_name) = @_;
  return sub {
    my ($self, $type, $version) = @_;
    my $dirname = catfile( $self->script_directory, $type, 'schema', $version );
    mkpath($dirname) unless -d $dirname;

    return catfile( $dirname, "001-auto-$source_name.sql" );
  }
}

sub _resultsource_protoschema_filename {
  my ($self, $source_name) = @_;
  return sub {
    my ($self, $version) = @_;
    my $dirname = catfile( $self->script_directory, '_protoschema', $version );
    mkpath($dirname) unless -d $dirname;

    return catfile( $dirname, "001-auto-$source_name.yml" );
  }
}

sub install_resultsource {
  my ($self, $args) = @_;
  my $source          = $args->{result_source};
  my $version         = $args->{version};
  log_info { 'installing_resultsource ' . $source->source_name . ", version $version" };
  my $rs_install_file =
    $self->_resultsource_install_filename($source->source_name);

  my $files = [
     $self->$rs_install_file(
      $self->storage->sqlt_type,
      $version,
    )
  ];
  $self->_run_sql_and_perl($files);
}

sub prepare_resultsource_install {
  my $self = shift;
  my $source = (shift @_)->{result_source};
  log_info { 'preparing install for resultsource ' . $source->source_name };

  my $install_filename = $self->_resultsource_install_filename($source->source_name);
  my $proto_filename = $self->_resultsource_protoschema_filename($source->source_name);
  $self->prepare_protoschema({
      parser_args => { sources => [$source->source_name], }
  }, $proto_filename);
  $self->_prepare_install({}, $proto_filename, $install_filename);
}

sub prepare_deploy {
  log_info { 'preparing deploy' };
  my $self = shift;
  $self->prepare_protoschema({}, '_ddl_protoschema_produce_filename');
  $self->_prepare_install({}, '_ddl_protoschema_produce_filename', '_ddl_schema_produce_filename');
}

sub prepare_upgrade {
  my ($self, $args) = @_;
  log_info {
     "preparing upgrade from $args->{from_version} to $args->{to_version}"
  };
  $self->_prepare_changegrade(
    $args->{from_version}, $args->{to_version}, $args->{version_set}, 'up'
  );
}

sub prepare_downgrade {
  my ($self, $args) = @_;
  log_info {
     "preparing downgrade from $args->{from_version} to $args->{to_version}"
  };
  $self->_prepare_changegrade(
    $args->{from_version}, $args->{to_version}, $args->{version_set}, 'down'
  );
}

method _coderefs_per_files($files) {
  no warnings 'redefine';
  [map eval do { local( @ARGV, $/ ) = $_; <> }, @$files]
}

method _prepare_changegrade($from_version, $to_version, $version_set, $direction) {
  my $schema    = $self->schema;
  my $databases = $self->databases;
  my $dir       = $self->script_directory;

  my $schema_version = $self->schema_version;
  my $diff_file_method = "_ddl_schema_${direction}_produce_filename";
  foreach my $db (@$databases) {
    my $diff_file = $self->$diff_file_method($db, $version_set, $dir );
    if(-e $diff_file) {
      carp("Overwriting existing $direction-diff file - $diff_file");
      unlink $diff_file;
    }

    open my $file, q(>), $diff_file;
    print {$file} join ";\n", @{$self->_sqldiff_from_yaml($from_version, $to_version, $db, $direction)};
    close $file;
  }
}

method _read_sql_file($file) {
  return unless $file;

  open my $fh, '<', $file;
  my @data = split /;\n/, join '', <$fh>;
  close $fh;

  @data = grep {
    $_ && # remove blank lines
    !/^(BEGIN|BEGIN TRANSACTION|COMMIT)/ # strip txn's
  } map {
    s/^\s+//; s/\s+$//; # trim whitespace
    join '', grep { !/^--/ } split /\n/ # remove comments
  } @data;

  return \@data;
}

sub downgrade_single_step {
  my $self = shift;
  my $version_set = (shift @_)->{version_set};
  Dlog_info { "downgrade_single_step'ing $_" } $version_set;

  my $sqlt_type = $self->storage->sqlt_type;
  my $sql_to_run;
  if ($self->ignore_ddl) {
     $sql_to_run = $self->_sqldiff_from_yaml(
       $version_set->[0], $version_set->[1], $sqlt_type, 'down',
     );
  }
  my $sql = $self->_run_sql_and_perl($self->_ddl_schema_down_consume_filenames(
    $sqlt_type,
    $version_set,
  ), $sql_to_run);

  return ['', $sql];
}

sub upgrade_single_step {
  my $self = shift;
  my $version_set = (shift @_)->{version_set};
  Dlog_info { "upgrade_single_step'ing $_" } $version_set;

  my $sqlt_type = $self->storage->sqlt_type;
  my $sql_to_run;
  if ($self->ignore_ddl) {
     $sql_to_run = $self->_sqldiff_from_yaml(
       $version_set->[0], $version_set->[1], $sqlt_type, 'up',
     );
  }
  my $sql = $self->_run_sql_and_perl($self->_ddl_schema_up_consume_filenames(
    $sqlt_type,
    $version_set,
  ), $sql_to_run);
  return ['', $sql];
}

sub prepare_protoschema {
  my $self      = shift;
  my $sqltargs  = { %{$self->sql_translator_args}, %{shift @_} };
  my $to_file   = shift;
  my $filename
    = $self->$to_file($self->schema_version);

  # we do this because the code that uses this sets parser args,
  # so we just need to merge in the package
  $sqltargs->{parser_args}{package} = $self->schema;
  my $sqlt = SQL::Translator->new({
    parser                  => 'SQL::Translator::Parser::DBIx::Class',
    producer                => 'SQL::Translator::Producer::YAML',
    %{ $sqltargs },
  });

  my $yml = $sqlt->translate;

  croak("Failed to translate to YAML: " . $sqlt->error)
    unless $yml;

  if (-e $filename ) {
    carp "Overwriting existing DDL-YML file - $filename";
    unlink $filename;
  }

  open my $file, q(>), $filename;
  print {$file} $yml;
  close $file;
}

__PACKAGE__->meta->make_immutable;

1;

# vim: ts=2 sw=2 expandtab

__END__

=head1 DESCRIPTION

This class is the meat of L<DBIx::Class::DeploymentHandler>.  It takes care
of generating serialized schemata  as well as sql files to move from one
version of a schema to the rest.  One of the hallmark features of this class
is that it allows for multiple sql files for deploy and upgrade, allowing
developers to fine tune deployment.  In addition it also allows for perl
files to be run at any stage of the process.

For basic usage see L<DBIx::Class::DeploymentHandler::HandlesDeploy>.  What's
documented here is extra fun stuff or private methods.

=head1 DIRECTORY LAYOUT

Arguably this is the best feature of L<DBIx::Class::DeploymentHandler>.  It's
heavily based upon L<DBIx::Migration::Directories>, but has some extensions and
modifications, so even if you are familiar with it, please read this.  I feel
like the best way to describe the layout is with the following example:

 $sql_migration_dir
 |- SQLite
 |  |- down
 |  |  `- 2-1
 |  |     `- 001-auto.sql
 |  |- schema
 |  |  `- 1
 |  |     `- 001-auto.sql
 |  `- up
 |     |- 1-2
 |     |  `- 001-auto.sql
 |     `- 2-3
 |        `- 001-auto.sql
 |- _common
 |  |- down
 |  |  `- 2-1
 |  |     `- 002-remove-customers.pl
 |  `- up
 |     `- 1-2
 |        `- 002-generate-customers.pl
 |- _generic
 |  |- down
 |  |  `- 2-1
 |  |     `- 001-auto.sql
 |  |- schema
 |  |  `- 1
 |  |     `- 001-auto.sql
 |  `- up
 |     `- 1-2
 |        |- 001-auto.sql
 |        `- 002-create-stored-procedures.sql
 `- MySQL
    |- down
    |  `- 2-1
    |     `- 001-auto.sql
    |- preinstall
    |  `- 1
    |     |- 001-create_database.pl
    |     `- 002-create_users_and_permissions.pl
    |- schema
    |  `- 1
    |     `- 001-auto.sql
    `- up
       `- 1-2
          `- 001-auto.sql

So basically, the code

 $dm->deploy(1)

on an C<SQLite> database that would simply run
C<$sql_migration_dir/SQLite/schema/1/001-auto.sql>.  Next,

 $dm->upgrade_single_step([1,2])

would run C<$sql_migration_dir/SQLite/up/1-2/001-auto.sql> followed by
C<$sql_migration_dir/_common/up/1-2/002-generate-customers.pl>.

C<.pl> files don't have to be in the C<_common> directory, but most of the time
they should be, because perl scripts are generally be database independent.

C<_generic> exists for when you for some reason are sure that your SQL is
generic enough to run on all databases.  Good luck with that one.

Note that unlike most steps in the process, C<preinstall> will not run SQL, as
there may not even be an database at preinstall time.  It will run perl scripts
just like the other steps in the process, but nothing is passed to them.
Until people have used this more it will remain freeform, but a recommended use
of preinstall is to have it prompt for username and password, and then call the
appropriate C<< CREATE DATABASE >> commands etc.

=head1 PERL SCRIPTS

A perl script for this tool is very simple.  It merely needs to contain an
anonymous sub that takes a L<DBIx::Class::Schema> as it's only argument.
A very basic perl script might look like:

 #!perl

 use strict;
 use warnings;

 sub {
   my $schema = shift;

   $schema->resultset('Users')->create({
     name => 'root',
     password => 'root',
   })
 }

=attr schema

The L<DBIx::Class::Schema> (B<required>) that is used to talk to the database
and generate the DDL.

=attr storage

The L<DBIx::Class::Storage> that is I<actually> used to talk to the database
and generate the DDL.  This is automatically created with L</_build_storage>.

=attr sql_translator_args

The arguments that get passed to L<SQL::Translator> when it's used.

=attr script_directory

The directory (default C<'sql'>) that scripts are stored in

=attr databases

The types of databases (default C<< [qw( MySQL SQLite PostgreSQL )] >>) to
generate files for

=attr txn_wrap

Set to true (which is the default) to wrap all upgrades and deploys in a single
transaction.

=attr schema_version

The version the schema on your harddrive is at.  Defaults to
C<< $self->schema->schema_version >>.

=begin comment

=head2 __ddl_consume_with_prefix

 $dm->__ddl_consume_with_prefix( 'SQLite', [qw( 1.00 1.01 )], 'up' )

This is the meat of the multi-file upgrade/deploy stuff.  It returns a list of
files in the order that they should be run for a generic "type" of upgrade.
You should not be calling this in user code.

=head2 _ddl_schema_consume_filenames

 $dm->__ddl_schema_consume_filenames( 'SQLite', [qw( 1.00 )] )

Just a curried L</__ddl_consume_with_prefix>.  Get's a list of files for an
initial deploy.

=head2 _ddl_schema_produce_filename

 $dm->__ddl_schema_produce_filename( 'SQLite', [qw( 1.00 )] )

Returns a single file in which an initial schema will be stored.

=head2 _ddl_schema_up_consume_filenames

 $dm->_ddl_schema_up_consume_filenames( 'SQLite', [qw( 1.00 )] )

Just a curried L</__ddl_consume_with_prefix>.  Get's a list of files for an
upgrade.

=head2 _ddl_schema_down_consume_filenames

 $dm->_ddl_schema_down_consume_filenames( 'SQLite', [qw( 1.00 )] )

Just a curried L</__ddl_consume_with_prefix>.  Get's a list of files for a
downgrade.

=head2 _ddl_schema_up_produce_filenames

 $dm->_ddl_schema_up_produce_filename( 'SQLite', [qw( 1.00 1.01 )] )

Returns a single file in which the sql to upgrade from one schema to another
will be stored.

=head2 _ddl_schema_down_produce_filename

 $dm->_ddl_schema_down_produce_filename( 'SQLite', [qw( 1.00 1.01 )] )

Returns a single file in which the sql to downgrade from one schema to another
will be stored.

=head2 _resultsource_install_filename

 my $filename_fn = $dm->_resultsource_install_filename('User');
 $dm->$filename_fn('SQLite', '1.00')

Returns a function which in turn returns a single filename used to install a
single resultsource.  Weird interface is convenient for me.  Deal with it.

=head2 _run_sql_and_perl

 $dm->_run_sql_and_perl([qw( list of filenames )])

Simply put, this runs the list of files passed to it.  If the file ends in
C<.sql> it runs it as sql and if it ends in C<.pl> it runs it as a perl file.

Depending on L</txn_wrap> all of the files run will be wrapped in a single
transaction.

=head2 _prepare_install

 $dm->_prepare_install({ add_drop_table => 0 }, sub { 'file_to_create' })

Generates the sql file for installing the database.  First arg is simply
L<SQL::Translator> args and the second is a coderef that returns the filename
to store the sql in.

=head2 _prepare_changegrade

 $dm->_prepare_changegrade('1.00', '1.01', [qw( 1.00 1.01)], 'up')

Generates the sql file for migrating from one schema version to another.  First
arg is the version to start from, second is the version to go to, third is the
L<version set|DBIx::Class::DeploymentHandler/VERSION SET>, and last is the
direction of the changegrade, be it 'up' or 'down'.

=head2 _read_sql_file

 $dm->_read_sql_file('foo.sql')

Reads a sql file and returns lines in an C<ArrayRef>.  Strips out comments,
transactions, and blank lines.

=end comment