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Eager loading

Preloading/Eager loading requires RedBeanPHP version 3.3+

If you know in advance that you need some parent beans you can inform RedBeanPHP about this to avoid unnecessary queries:


    $books = R::find('book');
    R::preload($books,array('author'));
    foreach($books as $book) echo $book->author; 

Here RedBeanPHP will NOT query each author separately. Instead, the preload() will attach all author beans upfront. Preload also understands aliases:


    $books = R::find('book');
    R::preload($books,array('coauthor'=>'author'));
    foreach($books as $book) echo $book->coauthor; 

These power-user features require RedBeanPHP version 3.4+

From version 3.4+ on you can preload multiple parents like this:


    $texts = R::find('text');
    //to preload page, book and author parents:
    R::preload($texts,'page,page.book,page.book.author');
    //or use the short-syntax:
    R::preload($texts,'page,*.book,*.author');

To retrieve the parent of a previous parent you can use the '*'. If you would like to retrieve a parent bean on the same level as the previous parent in the list use '&' instead.


    $p = R::find('page');
    //preloads page->book, page->book->author
    //and page->book->shelf
    R::preload($p,'book,*.author,&.shelf');

Note that both 'shelf' and 'author' are parents of book. Therefore we prefixed the '.shelf' with an & and not an '*'. If we would have used the latter, preload() would have tried to fetch page->book->author->shelf which does not exist of course. To preload lists:


    $books = R::find('book');

    R::preload($books,'ownPage|page,sharedGenre|genre');
    
    foreach($books as $book) { 
        print_r($book->ownPage);
    } 

Preloading is embedded in the syntax of RedBeanPHP, for instance instead of using an ugly foreach-loop, RedBeanPHP can make your code more elegant by preparing the preloaded beans for you as arguments of a closure (requires PHP 5.3):


    R::each($texts,'page,*.book',
    function($text,$page,$book){
        ...no ugly foreach-loop...
    });

To preload an aliased list use (requires 3.5.3+):


    R::preload( $author, array(
        'ownBook/coauthor' => 'book'
    );

This will load all books where the specified author was a coauthor. This is the preloader equivalent of:


    $author->alias('coauthor')->ownBook;

R::each is exactly the same as R::preload. The difference is just stylistic. If you use the closure variant I recommend to use 'each' to highlight the iteration.

Since RedBeanPHP 3.4.1 you can use with() conditions in preloading like this: 'ownBook'=>array('book',array(' category = ? ',array($category))) - i.e. simply replace the string 'book' for an array containing:

1. the type string
2. the SQL snippet you want to use and
3. the parameter bindings

Please be aware that these snippets are embedded in the query that retrieves all records so adding LIMIT clauses will cause undesirable results.


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