| 7 | 7 |
testing a very basic CD database using SQLite, with DBIx::Class::Schema
|
| 8 | 8 |
as the database frontend.
|
| 9 | 9 |
|
| 10 | |
The database consists of the following:
|
|
10 |
The database structure is based on the following rules:
|
|
11 |
|
|
12 |
An artist can have many cds, and each cd belongs to just one artist.
|
|
13 |
A cd can have many tracks, and each track belongs to just one cd.
|
|
14 |
|
|
15 |
The database is implemented with the following:
|
| 11 | 16 |
|
| 12 | 17 |
table 'artist' with columns: artistid, name
|
| 13 | |
table 'cd' with columns: cdid, artist, title, year
|
| 14 | |
table 'track' with columns: trackid, cd, title
|
|
18 |
table 'cd' with columns: cdid, artistid, title, year
|
|
19 |
table 'track' with columns: trackid, cdid, title
|
| 15 | 20 |
|
| 16 | |
|
| 17 | |
And these rules exists:
|
| 18 | |
|
| 19 | |
one artist can have many cds
|
| 20 | |
one cd belongs to one artist
|
| 21 | |
one cd can have many tracks
|
| 22 | |
one track belongs to one cd
|
| 23 | |
|
|
21 |
Each of the table's first columns is the primary key; any subsequent
|
|
22 |
keys are foreign keys.
|
| 24 | 23 |
|
| 25 | 24 |
=head2 Installation
|
| 26 | 25 |
|
| 27 | |
Install DBIx::Class via CPAN should be sufficient.
|
|
26 |
You'll need to install DBIx::Class via CPAN, and you'll also need to
|
|
27 |
install sqlite3 (not sqlite) if it's not already intalled.
|
| 28 | 28 |
|
| 29 | |
=head3 Create the database/tables
|
|
29 |
=head3 The database/tables/data
|
| 30 | 30 |
|
| 31 | |
First make and change the directory:
|
|
31 |
Your distribution already comes with a pre-filled SQLite database
|
|
32 |
F<examples/Schema/db/example.db>. You can see it by e.g.
|
| 32 | 33 |
|
| 33 | |
mkdir app
|
| 34 | |
cd app
|
| 35 | |
mkdir db
|
| 36 | |
cd db
|
|
34 |
cpanm --look DBIx::Class
|
| 37 | 35 |
|
| 38 | |
This example uses SQLite which is a dependency of DBIx::Class, so you
|
| 39 | |
shouldn't have to install extra software.
|
|
36 |
If for some reason the file is unreadable on your system, you can
|
|
37 |
recreate it as follows:
|
| 40 | 38 |
|
| 41 | |
Save the following into a example.sql in the directory db
|
|
39 |
cp -a <unpacked-DBIC-tarball>/examples/Schema dbicapp
|
|
40 |
cd dbicapp
|
|
41 |
rm db/example.db
|
|
42 |
sqlite3 db/example.db < db/example.sql
|
|
43 |
perl insertdb.pl
|
| 42 | 44 |
|
| 43 | |
CREATE TABLE artist (
|
| 44 | |
artistid INTEGER PRIMARY KEY,
|
| 45 | |
name TEXT NOT NULL
|
| 46 | |
);
|
|
45 |
=head3 Testing the database
|
| 47 | 46 |
|
| 48 | |
CREATE TABLE cd (
|
| 49 | |
cdid INTEGER PRIMARY KEY,
|
| 50 | |
artist INTEGER NOT NULL REFERENCES artist(artistid),
|
| 51 | |
title TEXT NOT NULL
|
| 52 | |
);
|
|
47 |
Enter the example Schema directory
|
| 53 | 48 |
|
| 54 | |
CREATE TABLE track (
|
| 55 | |
trackid INTEGER PRIMARY KEY,
|
| 56 | |
cd INTEGER NOT NULL REFERENCES cd(cdid),
|
| 57 | |
title TEXT NOT NULL
|
| 58 | |
);
|
|
49 |
cd <unpacked-DBIC-tarball>/examples/Schema
|
| 59 | 50 |
|
| 60 | |
and create the SQLite database file:
|
|
51 |
Run the script testdb.pl, which will test that the database has
|
|
52 |
successfully been filled.
|
| 61 | 53 |
|
| 62 | |
sqlite3 example.db < example.sql
|
|
54 |
When this script is run, it should output the following:
|
| 63 | 55 |
|
| 64 | |
=head3 Set up DBIx::Class::Schema
|
|
56 |
get_tracks_by_cd(Bad):
|
|
57 |
Leave Me Alone
|
|
58 |
Smooth Criminal
|
|
59 |
Dirty Diana
|
| 65 | 60 |
|
| 66 | |
Change directory back from db to the directory app:
|
|
61 |
get_tracks_by_artist(Michael Jackson):
|
|
62 |
Billie Jean (from the CD 'Thriller')
|
|
63 |
Beat It (from the CD 'Thriller')
|
|
64 |
Leave Me Alone (from the CD 'Bad')
|
|
65 |
Smooth Criminal (from the CD 'Bad')
|
|
66 |
Dirty Diana (from the CD 'Bad')
|
| 67 | 67 |
|
| 68 | |
cd ../
|
|
68 |
get_cd_by_track(Stan):
|
|
69 |
The Marshall Mathers LP has the track 'Stan'.
|
| 69 | 70 |
|
| 70 | |
Now create some more directories:
|
|
71 |
get_cds_by_artist(Michael Jackson):
|
|
72 |
Thriller
|
|
73 |
Bad
|
| 71 | 74 |
|
| 72 | |
mkdir MyApp
|
| 73 | |
mkdir MyApp/Schema
|
| 74 | |
mkdir MyApp/Schema/Result
|
| 75 | |
mkdir MyApp/Schema/ResultSet
|
|
75 |
get_artist_by_track(Dirty Diana):
|
|
76 |
Michael Jackson recorded the track 'Dirty Diana'.
|
| 76 | 77 |
|
| 77 | |
Then, create the following DBIx::Class::Schema classes:
|
| 78 | |
|
| 79 | |
MyApp/Schema.pm:
|
| 80 | |
|
| 81 | |
package MyApp::Schema;
|
| 82 | |
use base qw/DBIx::Class::Schema/;
|
| 83 | |
__PACKAGE__->load_namespaces;
|
| 84 | |
|
| 85 | |
1;
|
|
78 |
get_artist_by_cd(The Marshall Mathers LP):
|
|
79 |
Eminem recorded the CD 'The Marshall Mathers LP'.
|
| 86 | 80 |
|
| 87 | 81 |
|
| 88 | |
MyApp/Schema/Result/Artist.pm:
|
|
82 |
=head3 Discussion about the results
|
| 89 | 83 |
|
| 90 | |
package MyApp::Schema::Result::Artist;
|
| 91 | |
use base qw/DBIx::Class::Core/;
|
| 92 | |
__PACKAGE__->table('artist');
|
| 93 | |
__PACKAGE__->add_columns(qw/ artistid name /);
|
| 94 | |
__PACKAGE__->set_primary_key('artistid');
|
| 95 | |
__PACKAGE__->has_many('cds' => 'MyApp::Schema::Result::Cd');
|
|
84 |
The data model defined in this example has an artist with multiple CDs,
|
|
85 |
and a CD with multiple tracks; thus, it's simple to traverse from a
|
|
86 |
track back to a CD, and from there back to an artist. This is
|
|
87 |
demonstrated in the get_tracks_by_artist routine, where we easily walk
|
|
88 |
from the individual track back to the title of the CD that the track
|
|
89 |
came from ($track->cd->title).
|
| 96 | 90 |
|
| 97 | |
1;
|
| 98 | |
|
| 99 | |
|
| 100 | |
MyApp/Schema/Result/Cd.pm:
|
| 101 | |
|
| 102 | |
package MyApp::Schema::Result::Cd;
|
| 103 | |
use base qw/DBIx::Class::Core/;
|
| 104 | |
__PACKAGE__->load_components(qw/InflateColumn::DateTime/);
|
| 105 | |
__PACKAGE__->table('cd');
|
| 106 | |
__PACKAGE__->add_columns(qw/ cdid artist title year/);
|
| 107 | |
__PACKAGE__->set_primary_key('cdid');
|
| 108 | |
__PACKAGE__->belongs_to('artist' => 'MyApp::Schema::Result::Artist');
|
| 109 | |
__PACKAGE__->has_many('tracks' => 'MyApp::Schema::Result::Track');
|
| 110 | |
|
| 111 | |
1;
|
| 112 | |
|
| 113 | |
|
| 114 | |
MyApp/Schema/Result/Track.pm:
|
| 115 | |
|
| 116 | |
package MyApp::Schema::Result::Track;
|
| 117 | |
use base qw/DBIx::Class::Core/;
|
| 118 | |
__PACKAGE__->table('track');
|
| 119 | |
__PACKAGE__->add_columns(qw/ trackid cd title /);
|
| 120 | |
__PACKAGE__->set_primary_key('trackid');
|
| 121 | |
__PACKAGE__->belongs_to('cd' => 'MyApp::Schema::Result::Cd');
|
| 122 | |
|
| 123 | |
1;
|
| 124 | |
|
| 125 | |
|
| 126 | |
=head3 Write a script to insert some records
|
| 127 | |
|
| 128 | |
insertdb.pl
|
| 129 | |
|
| 130 | |
#!/usr/bin/perl
|
| 131 | |
|
| 132 | |
use strict;
|
| 133 | |
use warnings;
|
| 134 | |
|
| 135 | |
use MyApp::Schema;
|
| 136 | |
|
| 137 | |
my $schema = MyApp::Schema->connect('dbi:SQLite:db/example.db');
|
| 138 | |
|
| 139 | |
my @artists = (['Michael Jackson'], ['Eminem']);
|
| 140 | |
$schema->populate('Artist', [
|
| 141 | |
[qw/name/],
|
| 142 | |
@artists,
|
| 143 | |
]);
|
| 144 | |
|
| 145 | |
my %albums = (
|
| 146 | |
'Thriller' => 'Michael Jackson',
|
| 147 | |
'Bad' => 'Michael Jackson',
|
| 148 | |
'The Marshall Mathers LP' => 'Eminem',
|
| 149 | |
);
|
| 150 | |
|
| 151 | |
my @cds;
|
| 152 | |
foreach my $lp (keys %albums) {
|
| 153 | |
my $artist = $schema->resultset('Artist')->find({
|
| 154 | |
name => $albums{$lp}
|
| 155 | |
});
|
| 156 | |
push @cds, [$lp, $artist->id];
|
| 157 | |
}
|
| 158 | |
|
| 159 | |
$schema->populate('Cd', [
|
| 160 | |
[qw/title artist/],
|
| 161 | |
@cds,
|
| 162 | |
]);
|
| 163 | |
|
| 164 | |
|
| 165 | |
my %tracks = (
|
| 166 | |
'Beat It' => 'Thriller',
|
| 167 | |
'Billie Jean' => 'Thriller',
|
| 168 | |
'Dirty Diana' => 'Bad',
|
| 169 | |
'Smooth Criminal' => 'Bad',
|
| 170 | |
'Leave Me Alone' => 'Bad',
|
| 171 | |
'Stan' => 'The Marshall Mathers LP',
|
| 172 | |
'The Way I Am' => 'The Marshall Mathers LP',
|
| 173 | |
);
|
| 174 | |
|
| 175 | |
my @tracks;
|
| 176 | |
foreach my $track (keys %tracks) {
|
| 177 | |
my $cdname = $schema->resultset('Cd')->find({
|
| 178 | |
title => $tracks{$track},
|
| 179 | |
});
|
| 180 | |
push @tracks, [$cdname->id, $track];
|
| 181 | |
}
|
| 182 | |
|
| 183 | |
$schema->populate('Track',[
|
| 184 | |
[qw/cd title/],
|
| 185 | |
@tracks,
|
| 186 | |
]);
|
| 187 | |
|
| 188 | |
=head3 Create and run the test scripts
|
| 189 | |
|
| 190 | |
testdb.pl:
|
| 191 | |
|
| 192 | |
#!/usr/bin/perl
|
| 193 | |
|
| 194 | |
use strict;
|
| 195 | |
use warnings;
|
| 196 | |
|
| 197 | |
use MyApp::Schema;
|
| 198 | |
|
| 199 | |
my $schema = MyApp::Schema->connect('dbi:SQLite:db/example.db');
|
| 200 | |
# for other DSNs, e.g. MySQL, see the perldoc for the relevant dbd
|
| 201 | |
# driver, e.g perldoc L<DBD::mysql>.
|
| 202 | |
|
| 203 | |
get_tracks_by_cd('Bad');
|
| 204 | |
get_tracks_by_artist('Michael Jackson');
|
| 205 | |
|
| 206 | |
get_cd_by_track('Stan');
|
| 207 | |
get_cds_by_artist('Michael Jackson');
|
| 208 | |
|
| 209 | |
get_artist_by_track('Dirty Diana');
|
| 210 | |
get_artist_by_cd('The Marshall Mathers LP');
|
| 211 | |
|
| 212 | |
|
| 213 | |
sub get_tracks_by_cd {
|
| 214 | |
my $cdtitle = shift;
|
| 215 | |
print "get_tracks_by_cd($cdtitle):\n";
|
| 216 | |
my $rs = $schema->resultset('Track')->search(
|
| 217 | |
{
|
| 218 | |
'cd.title' => $cdtitle
|
| 219 | |
},
|
| 220 | |
{
|
| 221 | |
join => [qw/ cd /],
|
| 222 | |
}
|
| 223 | |
);
|
| 224 | |
while (my $track = $rs->next) {
|
| 225 | |
print $track->title . "\n";
|
| 226 | |
}
|
| 227 | |
print "\n";
|
| 228 | |
}
|
| 229 | |
|
| 230 | |
sub get_tracks_by_artist {
|
| 231 | |
my $artistname = shift;
|
| 232 | |
print "get_tracks_by_artist($artistname):\n";
|
| 233 | |
my $rs = $schema->resultset('Track')->search(
|
| 234 | |
{
|
| 235 | |
'artist.name' => $artistname
|
| 236 | |
},
|
| 237 | |
{
|
| 238 | |
join => {
|
| 239 | |
'cd' => 'artist'
|
| 240 | |
},
|
| 241 | |
}
|
| 242 | |
);
|
| 243 | |
while (my $track = $rs->next) {
|
| 244 | |
print $track->title . "\n";
|
| 245 | |
}
|
| 246 | |
print "\n";
|
| 247 | |
}
|
| 248 | |
|
| 249 | |
|
| 250 | |
sub get_cd_by_track {
|
| 251 | |
my $tracktitle = shift;
|
| 252 | |
print "get_cd_by_track($tracktitle):\n";
|
| 253 | |
my $rs = $schema->resultset('Cd')->search(
|
| 254 | |
{
|
| 255 | |
'tracks.title' => $tracktitle
|
| 256 | |
},
|
| 257 | |
{
|
| 258 | |
join => [qw/ tracks /],
|
| 259 | |
}
|
| 260 | |
);
|
| 261 | |
my $cd = $rs->first;
|
| 262 | |
print $cd->title . "\n\n";
|
| 263 | |
}
|
| 264 | |
|
| 265 | |
sub get_cds_by_artist {
|
| 266 | |
my $artistname = shift;
|
| 267 | |
print "get_cds_by_artist($artistname):\n";
|
| 268 | |
my $rs = $schema->resultset('Cd')->search(
|
| 269 | |
{
|
| 270 | |
'artist.name' => $artistname
|
| 271 | |
},
|
| 272 | |
{
|
| 273 | |
join => [qw/ artist /],
|
| 274 | |
}
|
| 275 | |
);
|
| 276 | |
while (my $cd = $rs->next) {
|
| 277 | |
print $cd->title . "\n";
|
| 278 | |
}
|
| 279 | |
print "\n";
|
| 280 | |
}
|
| 281 | |
|
| 282 | |
|
| 283 | |
|
| 284 | |
sub get_artist_by_track {
|
| 285 | |
my $tracktitle = shift;
|
| 286 | |
print "get_artist_by_track($tracktitle):\n";
|
| 287 | |
my $rs = $schema->resultset('Artist')->search(
|
| 288 | |
{
|
| 289 | |
'tracks.title' => $tracktitle
|
| 290 | |
},
|
| 291 | |
{
|
| 292 | |
join => {
|
| 293 | |
'cds' => 'tracks'
|
| 294 | |
}
|
| 295 | |
}
|
| 296 | |
);
|
| 297 | |
my $artist = $rs->first;
|
| 298 | |
print $artist->name . "\n\n";
|
| 299 | |
}
|
| 300 | |
|
| 301 | |
sub get_artist_by_cd {
|
| 302 | |
my $cdtitle = shift;
|
| 303 | |
print "get_artist_by_cd($cdtitle):\n";
|
| 304 | |
my $rs = $schema->resultset('Artist')->search(
|
| 305 | |
{
|
| 306 | |
'cds.title' => $cdtitle
|
| 307 | |
},
|
| 308 | |
{
|
| 309 | |
join => [qw/ cds /],
|
| 310 | |
}
|
| 311 | |
);
|
| 312 | |
my $artist = $rs->first;
|
| 313 | |
print $artist->name . "\n\n";
|
| 314 | |
}
|
| 315 | |
|
| 316 | |
|
| 317 | |
|
| 318 | |
It should output:
|
| 319 | |
|
| 320 | |
get_tracks_by_cd(Bad):
|
| 321 | |
Dirty Diana
|
| 322 | |
Smooth Criminal
|
| 323 | |
Leave Me Alone
|
| 324 | |
|
| 325 | |
get_tracks_by_artist(Michael Jackson):
|
| 326 | |
Beat it
|
| 327 | |
Billie Jean
|
| 328 | |
Dirty Diana
|
| 329 | |
Smooth Criminal
|
| 330 | |
Leave Me Alone
|
| 331 | |
|
| 332 | |
get_cd_by_track(Stan):
|
| 333 | |
The Marshall Mathers LP
|
| 334 | |
|
| 335 | |
get_cds_by_artist(Michael Jackson):
|
| 336 | |
Thriller
|
| 337 | |
Bad
|
| 338 | |
|
| 339 | |
get_artist_by_track(Dirty Diana):
|
| 340 | |
Michael Jackson
|
| 341 | |
|
| 342 | |
get_artist_by_cd(The Marshall Mathers LP):
|
| 343 | |
Eminem
|
| 344 | |
|
| 345 | |
=head1 Notes
|
| 346 | |
|
| 347 | |
A reference implementation of the database and scripts in this example
|
| 348 | |
are available in the main distribution for DBIx::Class under the
|
| 349 | |
directory F<examples/Schema>.
|
| 350 | |
|
| 351 | |
With these scripts we're relying on @INC looking in the current
|
| 352 | |
working directory. You may want to add the MyApp namespaces to
|
| 353 | |
@INC in a different way when it comes to deployment.
|
| 354 | |
|
| 355 | |
The F<testdb.pl> script is an excellent start for testing your database
|
| 356 | |
model.
|
|
91 |
Note also that in the get_tracks_by_cd and get_tracks_by_artist
|
|
92 |
routines, the result set is called multiple times with the 'next'
|
|
93 |
iterator. In contrast, get_cd_by_track uses the 'first' result set
|
|
94 |
method, since only one CD is expected to have a specific track.
|
| 357 | 95 |
|
| 358 | 96 |
This example uses L<DBIx::Class::Schema/load_namespaces> to load in the
|
| 359 | 97 |
appropriate L<Result|DBIx::Class::Manual::ResultClass> classes from the
|
| 360 | 98 |
C<MyApp::Schema::Result> namespace, and any required
|
| 361 | 99 |
L<ResultSet|DBIx::Class::ResultSet> classes from the
|
| 362 | |
C<MyApp::Schema::ResultSet> namespace (although we created the directory
|
| 363 | |
in the directions above we did not add, or need to add, any resultset
|
| 364 | |
classes).
|
|
100 |
C<MyApp::Schema::ResultSet> namespace (although we did not add, nor needed
|
|
101 |
any such classes in this example).
|
| 365 | 102 |
|
| 366 | 103 |
=head1 FURTHER QUESTIONS?
|
| 367 | 104 |
|