[hibernate-dev] [OGM-8, OGM-21] initial "criteria query" search

[Cyrille Chépélov]

Hi Sanne,

Le lundi 15 août 2011 à 16:48 +0100, Sanne Grinovero a écrit : 

> Regarding queries, you can use it with Hibernate Search as we did in a
> demo at JBoss World [1], that doesn't provide all power of relational
> queries but can still deal with most needs (and full text queries as
> well); the only thing you have to consider is to use


Well; the application for which I'm experimenting with OGM/Infinispan
requires a synchronous search behaviour (which is, once a write
transaction completes, subsequent 'read' transactions must show
immediately the modified state). A previous implementation of the
service currently struggles, because it attempts to expect this from
SOLR (meep! wrong). Eventually relying on Lucene again won't buy me much
here :)

As both OGM-21 (no JP-QL) and OGM-8 (no Criteria Queries either) block
me, and before temporarily retreating on JPA(Hibernate)+Postgres, I've
played with sketching a very early implementation of CQ support.  Not
much, not properly tested, nothing, but enough to get a my single use
case somewhat working:

/* with 

        @Entity
        public class Document {
            @Id
            @GeneratedValue(generator = "uuid")
        @GenericGenerator( name="uuid", strategy = "uuid2")
            String internalUuid;
            
            @NaturalId
            private String docuid;
        
            public String title;
        }

*/   

        CriteriaBuilder cb = em.getCriteriaBuilder();

        CriteriaQuery<Document> cq = cb.createQuery(Document.class);
        Root<Document> clRoot = cq.from(Document.class);

        cq.select(clRoot).where(cb.equal(clRoot.get("docuid"), uid));

        /* List<Document> docs = em.createQuery(cq).getResultsList(); */
        List<Document> docs = TypedCriteriaQueryFactory
                .createTypedQuery(em, cq).getResultList();

caveats:

      * apparently, Infinispan's Distributed Execution Framework
        requires the clustering mode to be "distribution"; "replication"
        ought to be fine too, but the engine seems to have strong
        opinion against this.
      * only the simplest queries have a chance to work 
      * a full scan on the whole ENTITIES cache is going to happen on
        every query.  And then an individual load(by @Id) on each
        matched entity.
      * for the moment, this is implemented as external code, rather
        than a proper patch. Hence a fairly ugly "ClandestineAccess"
        class. I guess a more correct implementation will have to find a
        better way to bounce from OgmEntityManager down to the
        InfinispanDialect, but for now Session seems to have a fairly
        strong opinion that the query world is about JDBC and HQL->SQL
        translations only.
      * Apparently, sometimes the ghost of a previous instance is
        detected by Infinispan which then fails because of a remote
        invocation error. I guess this is more an issue with eclipse
        starting new sessions before killing the previous one.


With that said, I can now proceed!

    -- Cyrille