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  for my $cd_data (@$cds) {
    my $tracks = delete $cd_data->{tracks};
    my $cd = $artist->create_related('cds', $cd_data);
    $cd->create_related('tracks', $_) for @$tracks;
  }

  printf "  + %-16s  %d CDs, %d tracks\n",
    $artist->name,
    $artist->cds->count,
    $artist->cds->search_related('tracks')->count;
}

# -- Counts -----------------------------------------------------------------

step("Counts");
show("Artists:", $schema->resultset('Artist')->count);
show("CDs:",     $schema->resultset('CD')->count);
show("Tracks:",  $schema->resultset('Track')->count);

# -- Queries ----------------------------------------------------------------

step("Query: all tracks by Kraftwerk (join through CD)");
my $rs = $schema->resultset('Track')->search(
  { 'artist.name' => 'Kraftwerk' },
  { join => { cd => 'artist' }, order_by => ['cd.year', 'me.position'] },
);
while (my $t = $rs->next) {
  printf "  %d. %-24s  (%s, %d)\n",
    $t->position, $t->title, $t->cd->title, $t->cd->year;
}

step("Query: CDs from the 70s (ordered by year)");
$rs = $schema->resultset('CD')->search(
  { year => { '>=' => 1970, '<' => 1980 } },
  { order_by => 'year', prefetch => 'artist' },
);
while (my $cd = $rs->next) {
  printf "  %d  %-26s  by %s\n", $cd->year, $cd->title, $cd->artist->name;
}

step("Query: artists with more than 3 tracks");
$rs = $schema->resultset('Artist')->search(undef, {
  join     => { cds => 'tracks' },
  group_by => ['me.id', 'me.name'],
  having   => \[ 'COUNT(tracks.id) > ?', 3 ],
});
while (my $a = $rs->next) {
  printf "  %-16s  %d tracks\n", $a->name,
    $a->cds->search_related('tracks')->count;
}

# -- Update -----------------------------------------------------------------

step("Update: rename 'Die Mensch-Maschine' to 'The Man-Machine'");
my $cd = $schema->resultset('CD')->find({ title => 'Die Mensch-Maschine' });
$cd->update({ title => 'The Man-Machine' });
show("New title:", $cd->title);

# -- Delete -----------------------------------------------------------------

step("Delete: remove Nina Simone and cascade");
my $nina = $schema->resultset('Artist')->find({ name => 'Nina Simone' });
# manual cascade: delete tracks, then CDs, then artist
for my $nina_cd ($nina->cds->all) {
  $nina_cd->tracks->delete;
  $nina_cd->delete;
}
$nina->delete;
show("Artists now:", $schema->resultset('Artist')->count);
show("CDs now:",     $schema->resultset('CD')->count);
show("Tracks now:",  $schema->resultset('Track')->count);

# -- Transaction ------------------------------------------------------------

step("Transaction: add + rollback");
eval {
  $schema->txn_do(sub {
    $schema->resultset('Artist')->create({ name => 'Ghost Artist' });
    show("Inside txn:", $schema->resultset('Artist')->count . " artists");
    die "intentional rollback\n";
  });
};
show("After rollback:", $schema->resultset('Artist')->count . " artists");

# -- ResultSet chaining -----------------------------------------------------

step("ResultSet chaining demo");
my $bowie_70s_tracks = $schema->resultset('Track')
  ->search({ 'artist.name' => 'David Bowie' }, { join => { cd => 'artist' } })
  ->search({ 'cd.year' => { '<' => 1975 } })
  ->search(undef, { order_by => [{ -asc => 'cd.year' }, { -asc => 'me.position' }] });

say "  David Bowie tracks from before 1975:";
while (my $t = $bowie_70s_tracks->next) {
  printf "    %s - %s (%d) #%d\n",
    $t->cd->title, $t->title, $t->cd->year, $t->position;
}

# -- Done -------------------------------------------------------------------

banner("Done");
say "  Everything works. DBIO is ready.\n";