Where-ing in discriminated tables

Question

How can I select all items from one specific author ? Its possible this way ? Or how can I edit entities if I want many item types and item packages (item has many items) too ?

Item

/**
 * @ORM\Table()
 * @ORM\Entity
 * @ORM\InheritanceType("JOINED")
 * @ORM\DiscriminatorColumn(name="discr", type="string")
 * @ORM\DiscriminatorMap({
 * "cd"   = "ItemCD",
 * "dvd"   = "ItemDVD",
 * "pack" = "ItemPack",
 * })
 */
class Item
{

    /**
     * @ORM\Column(name="id", type="integer", nullable=false)
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="IDENTITY")
     */
    private $id;

    /**
     * @ORM\Column(name="name", type="string", length=250, nullable=false)
     */
    private $name;

}

ItemCD

/**
 * @ORM\Table()
 * @ORM\Entity
 */
class ItemCD extends Item
{

    /**
     * @ORM\ManyToOne(targetEntity="Author", inversedBy="item")
     * @ORM\JoinColumn(name="author_id", referencedColumnName="id")
     */
    private $author;

}

ItemDVD

/**
 * @ORM\Table()
 * @ORM\Entity
 */
class ItemDVD extends Item
{

    /**
     * @ORM\ManyToOne(targetEntity="Author", inversedBy="item")
     * @ORM\JoinColumn(name="author_id", referencedColumnName="id")
     */
    private $author;

}

ItemPack

/**
 * @ORM\Table()
 * @ORM\Entity
 */
class ItemPack extends Item
{

    /**
     * @ORM\ManyToMany(targetEntity="Item", inversedBy="item")
     * @ORM\JoinTable()
     */
    private $items;

}

Author

/**
 * @ORM\Table()
 * @ORM\Entity
 */
class Author
{

    /**
     * @ORM\Column(name="id", type="integer", nullable=false)
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="IDENTITY")
     *
     */
    private $id;

    /**
     * @ORM\Column(name="name", type="string", length=250, nullable=false)
     */
    private $name;

}

Answer 1

You will have to query for specific elements. This is a known (and wanted) limitation, since DQL is a static typed language: see http://www.doctrine-project.org/jira/browse/DDC-16

Related: how to access fields in inherited table in doctrine2 / dql query

A way of handling this with a workaround is using 2 subqueries in your DQL:

SELECT
    i
FROM
    Item i
WHERE
    i.id IN(
        SELECT 
            i2.id
        FROM
            ItemDvd i2
        WHERE
            i2.author = :author
    )
    OR
    i.id IN(
        SELECT
            i3.id
        FROM
            ItemCd i3
        WHERE
            i3.author = :author
    )

As you can see you have to extract the identifiers for each possible subtype manually.

Edit: to get all the packs from a given author (along with single DVDs or CDs), the query becomes even worse:

SELECT
    i
FROM
    Item i
WHERE
    i.id IN(
        SELECT 
            i2.id
        FROM
            ItemDvd i2
        WHERE
            i2.author = :author
    )
    OR
    i.id IN(
        SELECT
            i3.id
        FROM
            ItemCd i3
        WHERE
            i3.author = :author
    )
    OR
    i.id IN(
        SELECT
            i4.id
        FROM
            ItemPack i4
        JOIN
            i4.items i5
        WHERE
            i5.id IN (
                SELECT
                    i6.id
                FROM
                    Item i6
                WHERE
                    i6.id IN(
                        SELECT 
                            i7.id
                        FROM
                            ItemDvd i7
                        WHERE
                            i7.author = :author
                    )
                    OR
                    i6.id IN(
                        SELECT
                            i8.id
                        FROM
                            ItemCd i8
                        WHERE
                            i8.author = :author
                    )
            )
    )

Answer 2

Make $author in Item and have ItemPacks $author value always be null. Then you can do:

$em->findBy("Item", array("author" => $author));

And you always get instances of ItemDVD or ItemCD.

Answer 3

It's tricky and lengthy the answer. I think the Entities aproach is ok, and by querying the item entity you would get what you want. Now for forms you'll probably need one FormType per sub-item and then user the aproach for Form Collections (http://symfony.com/doc/2.1/cookbook/form/form_collections.html) and I'm certain that you will need to hook into the pre-bind event to prepare the data.

This is a quick thought, may be it can help you.