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64 <h1>DBIx::Class Introduction</h1>
65 <h2>YAPC::NA 2010</h2>
69 <div class="presentation">
72 <h1>DBIX::Class (aka DBIC)</h1>
73 <h3>for (advanced) beginners</h3>
78 <h4>Originally Leo Lapworth @ LPW 2009</h4>
79 <h4>Matthew S. Trout</h4>
80 <h4>Justin D. Hunter</h4>
81 <h4>Arthur Axel "fREW" Schmidt</h4>
86 <p>You know a little about Perl and using objects</p>
87 <p>You know a little bit about databases and using foreign keys</p>
90 <li>How many people have designed a database with Foreign Keys?</li>
91 <li>How many people have used any ORM?<ul>
94 <li> Class::DBI? </li>
100 <li> DataMapper? </li>
101 <li>(N)Hibernate?</li>
108 <h1>DBIx::Class?</h1>
110 <li>ORM (object relational mapper)</li>
111 <li>SQL <-> OO (using objects instead of SQL)</li>
112 <li>Simple, powerful, complex, fab and confusing</li>
113 <li>There are many ORMs, DBIx::Class just happens to be the best in Perl (personal opinion)</li>
118 <h1>point of note</h1>
119 <p><em>"Debugging is twice as hard as writing the code in the first
120 place. Therefore, if you write the code as cleverly as possible,
121 you are, by definition, not smart enough to debug it." - Brian
122 W. Kernighan</em></p>
124 <p>This talk is about making it easy so we are less likely to get
129 <h1>Examples Table Setup</h1>
134 <em>MySQL not recommended</em>
138 <h1>authors table</h1>
139 <pre>CREATE TABLE authors(
140 id int(8) primary key auto_increment,
142 ) engine = InnoDB DEFAULT CHARSET=utf8;</pre>
147 <p>Name tables as simple plurals (<strong>add an S</strong>) - makes relationships easier to understand</p>
148 <p>Use a character set (<strong>UTF8</strong>) from the start (for international characters)</p>
152 <h1>authors table</h1>
153 <pre>CREATE TABLE author<strong>s</strong>(
154 id int(8) primary key auto_increment,
156 ) engine = <strong>InnoDB</strong> DEFAULT CHARSET=<strong>utf8</strong>;</pre>
161 <pre>CREATE TABLE books(
162 id int(8) primary key auto_increment,
164 author_id int(8),foreign key (author)
165 references authors(id)
166 ) engine = InnoDB DEFAULT CHARSET=utf8;</pre>
172 <p>Name link fields as singular</p>
173 <p>Ensure foreign key is the same type and size in both tables</p>
178 <pre>CREATE TABLE books(
179 id int(8) primary key auto_increment,
181 author_id <strong>int(8)</strong>,<strong>foreign key (<em>author</em>)</strong>
182 <strong>references <em>authors(id)</em></strong>
183 ) engine = InnoDB DEFAULT CHARSET=utf8;</pre>
187 <h1>CRUD compared</h1>
189 <li><strong>C</strong> - Create</li>
190 <li><strong>R</strong> - Read</li>
191 <li><strong>U</strong> - Update</li>
192 <li><strong>D</strong> - Delete</li>
197 <h1>Manual (SQL)</h1>
202 <pre>my $sth = $dbh->prepare('
209 'A book title', $author_id
215 <pre>my $sth = $dbh->prepare('
217 authors.name as author_name
219 WHERE books.author = authors.id
225 <pre>while( my $book = $sth->fetchrow_hashref() ) {
229 . $book->{author_name}
236 <pre>my $update = $dbh->prepare('
243 'New title',<strong>$book_id</strong>
249 <pre>my $delete = $dbh->prepare('
254 $delete->execute(<strong>$book_id</strong>);</pre>
262 <h1>DBIC: Create</h1>
263 <pre>my $book = $book_model->create({
264 title => 'A book title',
265 author => $author_id,
267 <p>Look ma, no SQL!</p>
271 <h1>DBIC: Create</h1>
272 <pre>my $pratchett = $author_model->create({
273 name => 'Terry Pratchett',
278 <h1>DBIC: Create</h1>
279 <pre>my $book = $pratchett->create_related(
280 <strong>books</strong> => {
281 title => 'Another Discworld book',
284 <pre>my $book = $pratchett->add_to_<strong>books</strong>({
285 title => 'Another Discworld book',
291 <p>DBIx::Class - Lots of ways to do the same thing...</p>
292 <p><em>"There is more than one way to do it (TIMTOWTDI, usually pronounced "Tim Toady") is a Perl motto"</em></p>
297 <pre>my $book = $book_model->find($book_id);
299 my $book = $book_model->search({
300 title => 'A book title',
301 }, { rows => 1 })->single;
303 my @books = $book_model->search({
304 author => $author_id,
310 <pre>while( my $book = $books_rs->next ) {
314 . $book->author->name
321 <pre>my $books_rs = $book_rs->search({
322 author => $author_id,
324 <p>Search takes SQL::Abstract formatted queries</p>
325 <pre>> perldoc SQL::Abstract</p>
329 <h1>DBIC: Update</h1>
330 <pre>$book->update({
331 title => 'New title',
336 <h1>DBIC: Delete</h1>
337 <pre>$book->delete;</pre>
341 <h1>Creating models</h1>
345 <pre>package MyApp::Schema::Result::Author;
346 use strict; use warnings;
347 __PACKAGE__->table('authors');
348 __PACKAGE__->add_columns(
350 data_type => 'int',
354 data_type => 'varchar',
359 __PACKAGE__->set_primary_key('id');
360 __PACKAGE__->has_many( books =>
361 'MyApp::Schema::Result::Book', 'author_id'
368 <pre>package MyApp::Schema::Result::Book;
369 use strict; use warnings;
370 __PACKAGE__->table('books');
371 __PACKAGE__->add_columns(
373 data_type => 'int',
377 data_type => 'varchar',
382 data_type => 'int',
384 is_nullable => 1, # <-- probably should be 0
387 __PACKAGE__->set_primary_key('id');
388 __PACKAGE__->belongs_to( author =>
389 'MyApp::Schema::Result::Author', 'author_id'
396 <h1>Schema::Loader</h1>
397 <p>DB -> Perl vs Perl -> DB</p>
398 <pre>package MyApp::Schema;
399 use strict; use warnings;
400 use base 'DBIx::Class::Schema::Loader';
401 __PACKAGE__->loader_options({
403 debug => $ENV{DBIC_TRACE},
409 my $schema = MyApp::Schema->connect($dsn, $user, $pass);
414 <h1>Splitting Logic Cleanly</h1>
415 <p>MyApp::Schema::Result::Foo = individual row</p>
416 <p>MyApp::Schema::ResultSet::Foo = searches / table </p>
420 <h1>Using your Schema</h1>
422 use strict; use warnings;
425 my $schema = MyApp::Schema->connect($dns, $user, $pass);
426 my $author_rs = $schema->resultset('Author');
427 my $author = $author_rs->create({
428 name => 'Douglas Adams',
430 my $book = $author->add_to_books({
438 <pre>DBIC_TRACE=1 ./your_script.pl</pre>
442 <h1>SQL - debugging</h1>
443 <pre>INSERT INTO authors (name)
444 VALUES (?): 'Douglas Adams'
446 INSERT INTO books (author, title)
447 VALUES (?, ?): '5', '42'</pre>
452 <pre>MyApp::Schema::Result::Book
453 MyApp::Schema::ResultSet::Book
454 MyApp::Schema::Result::Author
455 MyApp::Schema::ResultSet::Book</pre>
460 <pre>package Foo::Schema::Result::Books;
461 use base 'DBIx::Class';
470 # search amazon or something
471 my $api = Amazon::API->book({
472 title => $self->title
475 return $api->isbn;
483 <pre>print $book->isbn;</pre>
487 <h1>Result:: (inflating)</h1>
488 <pre>package Foo::Schema::Result::Books;
489 use base 'DBIx::Class';
493 use DateTime::Format::MySQL;
495 __PACKAGE__-><strong>inflate_column</strong>(
496 <strong>date_published</strong> => {
497 inflate => sub { DateTime::Format::MySQL->parse_date(shift) },
498 deflate => sub { shift->ymd},
501 # Automatic see: DBIx::Class::InflateColumn::DateTime</pre>
505 <h1>Result:: (inflating)</h1>
506 <pre>package Foo::Schema::Result::Books;
507 use base 'DBIx::Class';
511 use DateTime::Format::MySQL;
513 __PACKAGE__->inflate_column(
514 date_published => {
515 <strong>inflate => sub { DateTime::Format::MySQL->parse_date(shift) },
516 deflate => sub { shift->ymd},</strong>
519 # Automatic see: DBIx::Class::InflateColumn::DateTime
520 # Automatic see: DBIx::Class::InflateColumn::DateTime
521 # Automatic see: DBIx::Class::InflateColumn::DateTime</pre>
525 <h1>Result:: (deflating)</h1>
526 <pre>$book->date_published(DateTime->now);
527 $book->update;</pre>
531 <h1>Result:: (inflating)</h1>
532 <pre>my $date_published = $book->date_published;
533 print $date_published->month_abbr;</pre>
535 <strong><em>Nov</em></strong>
539 <h1>ResultSets::</h1>
540 <pre>package Foo::Schema::ResultSet::Books;
541 use base 'DBIx::Class::ResultSet';
542 sub the_ultimate_books {
544 return $self->search({ title => { -like => '%42%' } });
547 my ( $self, $author ) = @_;
548 return $self->search({ author => $author->id })
555 <h1>ResultSets::</h1>
556 <pre>package Foo::Schema::<strong>ResultSet::Books</strong>;
557 use base '<strong>DBIx::Class::ResultSet</strong>';
558 sub the_ultimate_books {
560 <strong>return $self->search({ title => { -like => '%42%' } })</strong>
563 my ( $self, $author ) = @_;
564 return $self->search({ author => $author->id })
571 <h1>ResultSets::</h1>
572 <pre>package Foo::Schema::ResultSet::Books;
573 use base 'DBIx::Class::ResultSet';
574 sub the_ultimate_books {
576 return $self->search({ title => { -like => '%42%' } });
579 my ( $self, $author ) = @_;
580 <strong>return $self->search({ author => $author->id })</strong>
587 <h1>ResultSets::</h1>
588 <pre>use Foo::Schema;
589 my $book_model = Foo::Schema->resultset('Books');
590 my $book_rs = $book_model->the_ultimate_books;
591 my @books = $book_rs->all;</pre>
595 <h1>ResultSets::chaining</h1>
596 <pre>use Foo::Schema;
597 my $book_model = Foo::Schema->resultset('Books');
598 my $author_model = Foo::Schema->resultset('Authors');
599 my $author = $author_model->search({ name => 'Douglas Adams' })->single;
600 my $book_rs = $book_model->the_ultimate_books->by_author($author);
601 my @books = $book_rs->all;</pre>
605 <h1>ResultSets::chaining</h1>
606 <pre>my $book_rs = $book_model
607 ->the_ultimate_books
608 ->by_author($author);</pre>
611 <pre>my $book_rs = $book_model
612 ->the_ultimate_books();
613 $book_rs = $book_rs->by_author($author);</pre>
616 # SELECT me.id, me.title, me.date_published, me.author
618 # WHERE ( ( ( author = ? ) AND ( title LIKE ? ) ) ): '5', '%42%'
619 # WHERE ( ( ( author = ? ) AND ( title LIKE ? ) ) ): '5', '%42%'</pre>
623 <h1>ResultSets::chaining</h1>
624 <pre>my $rs = $book_model
625 ->category('childrens')
626 ->by_author($author)
627 ->published_after('1812')
628 ->first_page_contains('once upon')
629 ->rating_greater_than(4);
631 my @books = $rs->all;</pre>
635 <h1>overloading before new record</h1>
639 <h1>overloading before new record</h1>
640 <pre>package Foo::Schema::Result::Authors;
641 use base 'DBIx::Class';
644 my ( $class, $attrs ) = @_;
646 my $new = $class->next::method($attrs);
653 <h1>relationships</h1>
657 <h1>multiple authors</h1>
661 <h1>a few relationships</h1>
662 (authors -- author_link_to_book -- books)
666 <h1>a few relationships</h1>
671 <h1>new join table</h1>
672 <pre>CREATE TABLE author_and_books(
673 id int(8) primary key auto_increment,
676 foreign key (book) references books(id),
677 foreign key (author) references authors(id)
678 ) engine = InnoDB DEFAULT CHARSET=utf8;
680 ALTER TABLE `books` DROP `author`</pre>
684 <h1>new join table</h1>
685 <pre>CREATE TABLE author_and_books(
686 id int(8) primary key auto_increment,
689 <strong>foreign key (book) references books(id),
690 foreign key (author) references authors(id)</strong>
691 ) engine = InnoDB DEFAULT CHARSET=utf8;
693 ALTER TABLE `books` DROP `author`</pre>
702 <pre>package Foo::Schema::<strong>Result::Books</strong>;
704 __PACKAGE__->has_many( author_and_books => "Foo::Schema::Result::AuthorAndBooks",
705 { "foreign.book" => "self.id" },
708 <strong># This is auto generated by Schema::Loader</strong></pre>
713 <pre>package Foo::Schema::<strong>Result::Books</strong>;
715 __PACKAGE__->has_many(
716 author_and_books => <strong># name of accessor</strong>
717 "Foo::Schema::Result::AuthorAndBooks", <strong># related class</strong>
718 { "foreign.book" => "self.id" } <strong># Relationship (magic often works if not
719 # specified, but avoid!)</strong>
730 <pre>package Foo::Schema::<strong>Result::AuthorAndBooks</strong>;
732 __PACKAGE__->belongs_to(
733 book => <strong># Accessor name</strong>
734 "Foo::Schema::Result::Books", <strong># Related class</strong>
735 { id => "book" } <strong># relationship</strong>
741 <h1>same for Authors</h1>
745 <h1>with no coding...</h1>
749 <h1>many_to_many</h1>
753 <h1>many_to_many</h1>
754 <pre>package Foo::Schema::<strong>Result::Books</strong>;
755 use base 'DBIx::Class';
757 __PACKAGE__->many_to_many(
758 authors => "author_and_books", 'author'
763 <strong> # This is <em>NOT</em> auto generated by Schema::Loader </strong></pre>
767 <h1>many_to_many</h1>
768 <pre>package Foo::Schema::<strong>Result::Books</strong>;
769 use base 'DBIx::Class';
771 __PACKAGE__->many_to_many(
772 authors <strong># Accessor name</strong>
773 => "author_and_books", <strong># has_many</strong>
774 'author' <strong># foreign relationship name</strong>
781 <h1>many_to_many</h1>
782 <pre>package Foo::Schema::Result::Authors;
783 use base 'DBIx::Class';
785 __PACKAGE__->many_to_many(
786 "books" <strong># Accessor Name</strong>
787 => "author_and_books", <strong># has_many accessor_name</strong>
788 'book' <strong># foreign relationship name</strong>
793 <strong># This is <em>NOT</em> auto generated by Schema::Loader</strong></pre>
797 <h1>using many_to_many</h1>
802 my $author_model = Foo::Schema->resultset('Authors');
803 my $author = $author_model->search({
804 name => 'Douglas Adams',
806 $author->add_to_books({
807 title => 'A new book',
812 <h1>using many_to_many</h1>
813 <pre>my $author = $author_model->search({
814 name => 'Douglas Adams',
816 <strong>$author->add_to_books({
817 title => 'A new book',
820 # SELECT me.id, me.name FROM authors me
821 # WHERE ( name = ? ): 'Douglas Adams';
822 # INSERT INTO books (title) VALUES (?): 'A new book';
823 # INSERT INTO author_and_books (author, book)
824 # VALUES (?, ?): '5', '2';</pre>
828 <h1>using many_to_many</h1>
829 <pre>$author->add_to_books($book);
831 $book->add_to_authors($author_1);
832 $book->add_to_authors($author_2);</pre>
836 <h1>in 16 lines of code</h1>
841 <p>Read them closely!</p>
845 <h1>error messages</h1>
846 <pre>DBIx::Class::Schema::Loader::connection(): Failed to load external class definition for 'Foo::Schema::Result::Authors': Can't locate object method "many_to_many" via package "Foo::Schema::Result::Author" at lib/Foo/Schema/Result/Authors.pm line 9.Compilation failed in require at /Library/Perl/5.8.8/DBIx/Class/Schema/Loader/Base.pm line 292.</pre>
850 <h1>error messages</h1>
851 <pre>DBIx::Class::Schema::Loader::connection(): Failed to load external class definition for 'Foo::Schema::Result::Authors': Can't locate object method "many_to_many" via package "Foo::Schema::<strong>Result::Author</strong>" at lib/Foo/Schema/<strong>Result/Authors.pm</strong> line 9.Compilation failed in require at /Library/Perl/5.8.8/DBIx/Class/Schema/Loader/Base.pm line 292.</pre>
857 <li>Turn on debugging</li>
858 <li>Read error messages (sometimes useful!)</li>
859 <li>Check field names</li>
860 <li>Check package names</li>
861 <li>Check which database you are connected to (dev/test/live?) - repeat above</li>
866 <h1>bonus slides!</h1>
870 <h1>Template Toolkit</h1>
872 <li><pre>[% author.books.count %]</pre> not working?</li>
873 <li>TT all methods are called in list context</li>
874 <li><pre>[% author.books<strong>_rs</strong>.count %]</pre> scalar context</li>
875 <li><em>Available for all relationships</em></li>
881 <pre>package Your::App::Model::<strong>Foo</strong>;
882 use base qw(<strong>Catalyst::Model::Schema::Schema</strong>);
887 __PACKAGE__->config(
888 schema_class => '<strong>Foo::Schema</strong>',
892 <p>Keep your Schema in a <em>separate</em> package to your Catalyst application</p>
897 <pre>sub action_name : Local {
900 my $model = $c->model('Schema::Foo');
901 my $author_model = $model->resultset('Authors');