doctrine2/UPGRADE_TO_2_0

# Upgrade from 2.0-ALPHA4 to 2.0-BETA1

## Default Property for Field Mappings

The "default" option for database column defaults has been removed. If desired, database column defaults can
be implemented by using the columnDefinition attribute of the @Column annotation (or the approriate XML and YAML equivalents).
Prefer PHP default values, if possible.

## Partial Objects

xxx

## XML Mapping Driver

The 'inheritance-type' attribute changed to take last bit of ClassMetadata constant names, i.e.
NONE, SINGLE_TABLE, INHERITANCE_TYPE_JOINED

## YAML Mapping Driver

The way to specify lifecycle callbacks in YAML Mapping driver was changed to allow for multiple callbacks
per event. The Old syntax ways:

    [yaml]
    lifecycleCallbacks:
      doStuffOnPrePersist: prePersist
      doStuffOnPostPersist: postPersist

The new syntax is:

    [yaml]
    lifecycleCallbacks:
      prePersist: [ doStuffOnPrePersist, doOtherStuffOnPrePersistToo ]
      postPersist: [ doStuffOnPostPersist ]

## PreUpdate Event Listeners

Event Listeners listening to the 'preUpdate' event can only affect the primitive values of entity changesets
by using the API on the `PreUpdateEventArgs` instance passed to the preUpdate listener method. Any changes
to the state of the entitys properties won't affect the database UPDATE statement anymore. This gives drastic
performance benefits for the preUpdate event.