Re: [smartweb-devel] Smartweb Auth and problem with XDoclet/ Hibernate union subclass

[Roberto Lo G. <rlo...@us...>]

The problem using sequence generator is some database doesn't support
sequences: the consequence will be an unsable auth module on those
databases.

An analysis og pros and cons of the two choices could be more helpful.

Joined Subclass
  Pros
    # Well known and supported by xdoclet without needing to be patched
    # Supported by all databases
    # Allows database constraints
    # Better performances if a list of Subjects is requested (only id and
display properties)
  Cons
    # Requires an additional Subject table
    # Full queries on Subject, User or Group needs a JOIN on twoor three
tables
    # Pessimistical locking need to acquire 2 locks

Union Subclass
  Pros
    # Better performances on quering User and Group entities as no JOIN is
requested
    # No additional table exposed
    # Easier to query using plain SQL outside Hibernate
  Cons
    # Quering Subject needs a UNION, whatever infos you need
    # Same field on two tables
    # Needs sequence support on the database


Gaetano Perrone wrote:
> 
> I delve into the problem and hibernate documentation says that identity
> generator strategy is not allowed in union subclass inheritance, indeed
> the primary key seed has to be shared accross all unioned subclasses of a
> hierarchy.
> The suggested approch for generating table  for concrete class is to use a
> sequence generator strategy instead of native.  With this approch each
> table defines columns for all properties of the class, including inherited
> properties. The limitation of this approach is that if a property is
> mapped on the superclass, the column name must be the same on all subclass
> tables. (Hibernate group is going to relax this in a future release).
> This means that a dedicated class tree sequence could be
> introduced....Otherwise i don't know what happens using the
> hibernate_sequence as sequence instead of generator native...
> What do u thing about it??
> 

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