NHibernate 2.0 Alpha is out!
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It gives me great pleasure to announce that NHiberante 2.0 Alpha 1 was released last night and can be downloaded from this location.

We call this alpha, but many of us are using this in production, so we are really certain in its stability. The reason that this is an alpha is that we have made a lot of changes in the last nine months (since the last release), and we want to get more real world experience before we ship this. Recent estimates are of about 100,000 lines of code has changed since the last release.

You can see the unofficial change list below. Please note that there are breaking changes in the move to NHibernate 2.0. There are also significant improvement in many fields, as you will see in a moment.

We are particularly interested in hearing about compatibility issues, performance issues and "why doesn't this drat work?" issues.

We offer support for moving to NHibernate 2.0 Alpha on the NHibernate mailing list at: nhusers@googlegroups.com (http://groups.google.com/group/nhusers).

And now, for the changes:

  • New features:
    • Add join mapping element to map one class to several tables
    • <union> tables and <union-subclass> inheritance strategy
    • HQL functions 'current_timestamp', 'str' and 'locate' for PostgreSQL dialect
    • VetoInterceptor - Cancel Calls to Delete, Update, Insert via the IInterceptor Interface
    • Using constants in select clause of HQL
    • Added [ Table per subclass, using a discriminator ] Support to Nhibernate
    • Added support for paging in sub queries.
    • Auto discovery of types in custom SQL queries
    • Added OnPreLoad & OnPostLoad Lifecycle Events
    • Added ThreadStaticSessionContext
    • Added <on-delete> tag to <key>
    • Added foreign-key="none" since the Parent have not-found="ignore". (not relevant to SQL Server)
    • Added DetachedQuery
    • ExecuteUpdate support for native SQL queries
    • From Hibernate:
      • Ported Actions, Events and Listeners
      • Ported StatelessSession
      • Ported CacheMode
      • Ported Statistics
      • Ported QueryPlan
      • Ported ResultSetWrapper
      • Ported  Structured/Unstructured cache
      • Ported SchemaUpdate
      • Ported Hibernate.UserTypes
      • Ported Hibernate.Mapping
      • Ported Hibernate.Type
      • Ported EntityKey
      • Ported CollectionKey
      • Ported TypedValue
      • Ported SQLExceptionConverter
      • Ported Session Context
      • Ported CascadingAction
  • Breaking changes:
    • Changed NHibernate.Expression namespace to NHibernate.Criterion
    • Changed NHiberante.Property namespace to NHiberante.Properties
    • No AutoFlush outside a transaction - Database transactions are never optional, all communication with a database has to occur inside a transaction, no matter if you read or write data.
    • <nhibernate> section is ignored, using <hibernate-configuration> section (note that they have different XML formats)
    • Configuration values are no longer prefixed by "hibernate.", if before you would specify "hibernate.dialect", now you specify just "dialect"
    • IInterceptor changed to match the Hibernate 3.2 Interceptor - interface changed
    • Will perform validation on all named queries at initialization time, and throw if any is not valid.
    • NHibernate will return long for count(*) queries on SQL Server
    • SaveOrUpdateCopy return a new instance of the entity without change the original.
    • INamingStrategy interface changed
    • NHibernate.Search - Moved Index/Store attributes to the Attributes namespace
    • Changes to IType, IEntityPersister, IVersionType - of interest only to people who did crazy stuff with NHibernate.
    • <formula> must contain parenthesis when needed
    • IBatcher interface change
  • Fixed bugs:
    • Fixing bug with HQL queries on map with formula.
    • Fixed exception when the <idbag> has a <composite-element> inside; inside which, has a <many-to-one>
    • Multi criteria doesn't support paging on dialects that doesn't support limiting the query size using SQL.
    • Fixed an issue with limit string in MsSql2005 dialect sorting incorrectly on machines with multiple processors
    • Fixed an issue with getting NullReferenceException when using SimpleSubqueryExpression within another subexpression
    • Fixed Null Reference Exception when deleting a <list> that has holes in it.
    • Fixed duplicate column name on complex joins of similar tables
    • Fixed MultiQuery force to use parameter in all queries
    • Fixed concat function fails when a parameter contains a comma, and using MaxResults
    • Fixed failure with Formula when using the paging on MSSQL 2005 dialect
    • Fixed PersistentEnumType incorrectly assumes enum types have zero-value defined
    • Fixed SetMaxResults() returns one less row when SetFirstResult() is not used
    • Fixed Bug in GetLimitString for SQL Server 2005 when ordering by aggregates
    • Fixed SessionImpl.EnableFilter returns wrong filter if already enabled
    • Fixed Generated Id does not work for MySQL
    • Fixed one-to-one can never be lazy
    • Fixed FOR UPDATE statements not generated for pessimistic locking
  • Improvements:
    • Added Guid support for Postgre Dialect
    • Added support for comments in queries
    • Added Merge and Persist to ISession
    • Support IFF for SQL Server
    • IdBag now work with Identity columns
    • Multi Criteria now uses the Result Transformer
    • Handling key-many-to-one && not-found
    • Can now specify that a class is abstract in the mapping.
  • Guidance:
    • Prefer to use the Restrictions instead of the Expression class for defining Criteria queries.
  • Child projects:
    • Added NHibernate.Validator
    • Added NHibernate.Shards
    • NHibernate.Search updated match to Hibernate Search 3.0
  • Criteria API:
    • Allow Inspection, Traversal, Cloning and Transformation for ICriteria and DetachedCriteria
      • Introduced CriteriaTransformer class
      • GetCriteriaByPath, GetCriteriaByAlias
    • Added DetachedCriteria.For<T>
    • Added Multi Criteria
    • Projections can now pass parameters to the generated SQL statement.
    • Added support for calling Sql Functions (HQL concept) from projections (Criteria).
    • Added ConstantProjection
    • Added CastProjection
    • Can use IProjection as a parameter to ICriterion
  • Better validation for proxies:
    • Now supports checking for internal fields as well
    • Updated Castle.DynamicProxy2.dll to have better support for .NET 2.0 SP1
  • SQL Lite:
    • Support for multi query and multi criteria
    • Supporting subselects and limits
    • Allowed DROP TABLE IF EXISTS semantics
  • PostgreSQL (Npgsql):
    • Enable Multi Query support for PostgreSQL
  • FireBird:
    • Much better overall support
  • Batching:
    • Changed logging to make it clearer that all commands are send to the database in a single batch.
    • AbstractBatcher now use the Interceptor to allow the user intercept and change an SQL before it's preparation
  • Error handling:
    • Better error message on exception in getting values in Int32Type
    • Better error message when using a subquery that contains a reference to non existing property
    • Throws a more meaningful exception when calling UniqueResult<T>() with a value type and the query returns null.
    • Overall better error handling
    • Better debug logs
  • Refactoring:
    • Major refactoring internally to use generic collections instead of the non generic types.
    • Major refactoring to the configuration and the parsing of hbm files.
  • Factories:
    • Added ProxyFactoryFactory
    • Added BatchingBatcherFactory
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