Imagine the following setup:

abstract class BaseRecord extends Doctrine_Record
abstract class Category extends BaseRecord
class ConcreteCategory extends Category

schema.yml:

Category:
  inheritance:
    extends: BaseRecord
  columns:
    ...

ConcreteCategory:
  inheritance:
    extends: Category
    type: column_aggregation
    keyField: ...
    keyValue: ...

BaseRecord? contains some methods that are shared across all my models. It does not contain any columns and thus is not specified in schema.yml. Category is a base class for all my category types. It is abstract as well, several concrete categories inherit it.

The problem is that Doctrine tries to merge all columns from the children (ConcreteCategory?) to the most upper parent class (here BaseRecord?), since the type is specified as column_aggregation. It does not check though, whether the inheritance type in the children's parents (Category extends BaseRecord?) is of type column_aggregation as well. Merging everything to BaseRecord? fails though, as BaseRecord? is nowhere defined in the schema.yml.

There is a very easy fix for this problem:

Doctrine_Import_Schema, line 475:

            $parent = $this->_findBaseSuperClass($array, $definition['className']);
            // Move any definitions on the schema to the parent
            if (isset($definition['inheritance']['extends']) && isset($definition['inheritance']['type']) && ($definition['inheritance']['type'] == 'simple' || $definition['inheritance']['type'] == 'column_aggregation')) {
                foreach ($moves as $move => $resetValue) {
                    $array[$parent][$move] = Doctrine_Lib::arrayDeepMerge($array[$parent][$move], $definition[$move]);

In case the inheritance of the current class (ConcreteCategory?) is column_aggregation, the base parent (BaseRecord?) is found out and initialized ($array[$parent]...). _findBaseSuperClass should not loop to the most upper parent though, but only as long as the condition in line 477 is met. Thus we should change the code in line 500 from

    protected function _findBaseSuperClass($array, $class)
    {
        if (isset($array[$class]['inheritance']['extends'])) {
            return $this->_findBaseSuperClass($array, $array[$class]['inheritance']['extends']);

to

    protected function _findBaseSuperClass($array, $class)
    {
        if (isset($array[$class]['inheritance']['extends']) && isset($array[$class]['inheritance']['type']) && ($array[$class]['inheritance']['type'] == 'simple' || $array[$class]['inheritance']['type'] == 'column_aggregation')) {
            return $this->_findBaseSuperClass($array, $array[$class]['inheritance']['extends']);

You can also refactor the initialization of the variable $parent inside the if-statement (line 475 again):

            // Move any definitions on the schema to the parent
            if (isset($definition['inheritance']['extends']) && isset($definition['inheritance']['type']) && ($definition['inheritance']['type'] == 'simple' || $definition['inheritance']['type'] == 'column_aggregation')) {
                $parent = $this->_findBaseSuperClass($array, $definition['className']);
                foreach ($moves as $move => $resetValue) {
                    $array[$parent][$move] = Doctrine_Lib::arrayDeepMerge($array[$parent][$move], $definition[$move]);