Question

I’m having a problem with my mapping. I can’t get it to work. I have an abstract base class like so:

/**
 * @Entity
 * @Table(name="actions")
 * @InheritanceType("JOINED")
 * @DiscriminatorColumn(name="type", type="string")
 * @DiscriminatorMap({"FOO" = "FooAction", "BAR" = "BarAction", ...})
 */
abstract class AbstractAction
{
    ...
}

I have a bunch of different actions, all with different fields. E.g:

/**
 * @Entity
 * @Table(name="actions_foo")
 */
class FooAction extends AbstractAction
{
   ...
}

But one of my actions (BarAction) does not need any extra fields besides those supplied by the AbstractAction. But how can I map that? I tried omitting the @Table, or using the same @Table as the AbstractAction, but to no effect.

/**
 * @Entity
 * @Table(name="actions")
 */
class BarAction extends AbstractAction
{
   ...
}

Omitting the @Table gives me a PDOException about a missing table BarAction. Using the @Table of the base class gives me:

PDOException: SQLSTATE[HY093]: Invalid parameter number: number of bound variables does not match number of tokens

So, how do I map this?

Edit: So far I have tried two more things.

I tried removing the @Entity as well as the @Table from BarAction in the hope that this way it would no longer require a database table. That doesn’t work. Instead, I get this error:

Doctrine\ORM\Mapping\MappingException: Class BarAction is not a valid entity or mapped super class.

Next I tried creating an actions_bar table in my database with just a single foreign key column id. Then I mapped the BarAction to it. That works (yay!) but it feels crufty and ugly to have an extra SQL table that I don’t need at all.

So, still looking for a better way…

Answer 1

You are using joined inheritance model (class table inheritance), which uses a separate table for parent and each child. If you don’t specify any fields in the child class, Doctrine will just create a table only containing ID field.

And a parent class can only use one type of inheritance, either class table inheritance or single table inheritance.

In that case, if you don’t want to have a table with only id column in it, you need to change your data model.