Doctrine - Access metadata saved on linking table - orm

Question

I have 3 tables:
# schema.yml
Author:
connection: store-rw-library
tableName: lib_author
actAs: { Timestampable: ~ }
columns:
id:
type: integer(4)
unsigned: 1
primary: true
autoincrement: true
name:
type: string(50)
notnull: true
Book:
connection: store-rw-library
tableName: lib_book
actAs: { Timestampable: ~ }
columns:
id:
type: integer(4)
unsigned: 1
primary: true
autoincrement: true
name:
type: string(50)
notnull: true
relations:
Author:
class: Author
foreignAlias: Books
refClass: LinkingAuthorBook
LinkingAuthorBook:
connection: store-rw-library
tableName: lib_linking_author_book
columns:
author_id:
type: integer(4)
unsigned: 1
primary: true
book_id:
type: integer(4)
unsigned: 1
primary: true
created_at:
type: timestamp(25)
notnull: true
relations:
Author:
foreignAlias: AuthorBooks
Book:
foreignAlias: AuthorBooks
Per the notes via Doctrine docs, I established the relationships as M:M between Author and Book using the LinkingAuthorBook table.
Now, I am trying to get all the books authored by a specific author, in one query, something like:
class AuthorTable
{
public function getAuthor($id)
{
$q = Doctrine_Query::create()
->select('a.id AS author_id')
->addSelect('a.name AS author_name')
->addSelect('b.AuthorBooks')
->from('Author a')
->innerJoin('a.Books b')
->where('a.id = ?', $id);
$result = $q->fetchArray();
}
}
The resulting query from the above DQL construct:
SELECT
m.id AS m__id,
m.name AS m__1,
m2.id AS m2__id,
m2.name AS m2__1,
m.id AS m__0,
m.name AS m__1
FROM
lib_author m
INNER JOIN
lib_linking_author_book m3 ON (m.id = m3.author_id)
INNER JOIN
lib_book m2 ON m2.id = m3.book_id
WHERE
(m.id = '163')
From the above query, I see that it is correctly doing the joins, but how do I access the LinkingAuthorBook.created_at metadata column, established in my schema.yml file?
The only way I was able to get access to the metadata column was by adding an explicit innerJoin to LinkingAuthorBook (with associated book_link alias), but this resulted in another join in the resulting SQL. Which doesn't make sense because it has access to the data it needs from the original query.
-- Update (3.7.2012) --
The problem is still occurring, if I setup a loop to iterate over all the books belonging to an author, I cannot combine the meta data from the LinkingAuthorBook table or the Book table without forcing another query.
Updated query:
$q = Doctrine_Query::create()
->from('Author a')
->innerJoin('a.Books b')
->innerJoin('b.LinkingAuthorBook ab ON a.id = ab.author_id AND b.id = ab.book_id')
->where('a.id = ?', $id);
Example loop from LinkingAuthorBook -> Book:
foreach ($author->getLinkingAuthorBook() as $link) {
// Works fine, no extra query
var_dump($link->getCreatedAt());
// Forces an extra query, even though 'name' is the column name
// So even though doctrine uses lazy-load, it should be able to
// get this data from the original query
var_dump($link->getBook()->getName());
}
And the same for the following loop of Book -> LinkingAuthorBook:
foreach ($author->getBook() as $book) {
// Forces extra query
var_dump($book->getLinkingAuthorBook()->getCreatedAt());
// No extra query
var_dump($book->getName());
}
My work around:
class Book
{
public $meta;
}
class AuthorTable
{
public function getAuthor($id)
{
$q = Doctrine_Query::create()
->from('Author a')
->innerJoin('a.Books b')
->innerJoin('b.LinkingAuthorBook ab ON a.id = ab.author_id AND b.id = ab.book_id')
->where('a.id = ?', $id);
$author = $q->fetchOne();
// Manually hydrate Book Meta
foreach ($author->getLinkingAuthorBook() as $authorBook) {
$authorBooks[$authorBook->getId()] = $authorBook;
}
foreach ($author->getBook() as $book) {
$book->meta = $authorBooks[$book->getId()];
}
}
}
So now, I can iterate over books, with meta, without forcing an extra query:
foreach ($author->getBook() as $book) {
// No extra query
var_dump($book->meta->getCreatedAt());
// No extra query
var_dump($book->getName());
}
-- Update (3.8.2012) --
So I was able to prove that in the following code:
foreach ($author->getBooks() as $book)
{
echo $book->getName().'- '.$book->LinkingAuthorBook[0]->getCreatedAt().'<br/>';
}
Each iteration caused a new query to be issued in order to get the createdAt value. I did this by issuing the following commands in MySQL:
mysql> set global log_output = 'FILE';
mysql> set global general_log = 'ON';
mysql> set global general_log_file = '/var/log/mysql/queries.log';
Then I tailed /var/log/mysql/queries.log and was able to see the additional queries being generated. So, as far as I can tell, manually hydrating the Book::Meta object after initial query, is the only way to access the metadata without having to issue another query.

Answer 1

My suggestion:
//one query for fetching an Author, his books and created_at for the each book
$q = Doctrine_Query::create()
->from('Author a')
->innerJoin('a.Books b')
->innerJoin('b.LinkingAuthorBook ab ON a.id = ab.author_id AND b.id = ab.book_id')
->where('a.id = ?', 1);
$author = $q->fetchOne();
echo 'Author: '.$author->getName().'<br/>';
echo 'Books: <br/>';
foreach ($author->getBooks() as $book)
{
echo $book->getName().'- '.$book->LinkingAuthorBook[0]->getCreatedAt().'<br/>';
}
Only one query you realy need.