Liquid Projections for NHibernate

What is this?

This package provides an NHibernateProjector that allows you to build NHibernate-backed projectors for use with LiquidProjections' event mapping API and Dispatcher class.

What does it offer?

• Supports NHibernate 4.0 or later.
• Allows customizing how many LiquidProjections Transactions it should process in a single database transaction.
• Supports nesting one or more NHibernateChildProjectors that can be used for maintaining lookup tables and which are part of the same database transaction as the parent projector creates.
• Ensures autonomy by storing the IProjectionState (e.g. the last transaction checkpoint) in the same transaction as the actual projection data.
• Allows the projector to be configured with an ExceptionPolicy delegate so that you can handle projection exceptions and get full control on whether or not the projector should retry the entire batch, individual transactions, ignore or abort the exception.
• If the implementation of IProjectorState has additional custom properties, you can use the EnrichState delegate of the NHibernateProjector to update the state object before it is written to the database. This is called as part of the same database transaction that encompasses the projector code.

Why would I use NHibernate for something like a projection

Some have argued that using raw SQL is the fasted method for updating RDBMS-backed projections. And quite often this is true. But depending on the nature of the projection, in particular when it touches the same projection many times in the same batch of events, the unit-of-work (the ISession) can provide some significant speed improvements.