Re: [hibernate-dev] RE: Exposing legacy Lucene documents on searches.

Hi John, The idea behind projections is to avoid full database round-trips in uses cases where you are only interested in a subset of object properties (instead of the full Hibernate managed object). Lucene allows you to store the original values of the fields you are indexing in the index itself. This functioanlity is exposed in HSearch via the annotation @Field(store=Store.YES). My favourite use case is a online shop. Normally such a site has some sort of search functionality. Say that only the title, price and category of an item is searchable and beeing displayed on the search result page. If you store these properties in the lucene index you can retrieve them at search time and just return these 'projected' values without accessing the database. When a user then clicks on a single item you would normally retrieve the fully managed Item object from the database (probably using the hibernate id) Projections will be returned as object arrays. Have a look at the example in the HSearch documentation: http://www.hibernate.org/hib_docs/search/reference/en/html_single/#d0e1139 Cheers Hardy