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Tuesday, April 07, 2009

Linq to Coherence + Attributes + MetaData = Cool

First, we got the Linq Provider for Oracle Coherence

Second, we got attribute based serialization

Third, Metadata in the serialization stream

Once we put all that together, what we get is a set of very clean way of storing and querying data in Oracle Coherence.

A Coherence Linq provider now supports passing a CoherenceQueryTranslator as a parameter. I am providing a MetadataCoherenceQueryTranslator that uses getProperty method to access property originally serialized by the Generic Serializer. Here’s almost all relative .Net Code:

Person Class

[POFSerializableObject(StoreMetadata=true)]
    public class Person// : IPortableObject
    {
        [POFSerializableMember(Order=0,WriteAsType=POFWriteAsTypeEnum.Int16)]
        public int ID { get; set; }
        [POFSerializableMember(Order=1)]
        public string FirstName { get; set; }
        [POFSerializableMember(Order = 2)]
        public string LastName { get; set; }
        [POFSerializableMember(Order = 3)]
        public string Address { get; set; }
        [POFSerializableMember(Order = 4)]
        public string Title { get; set; }
        public Person()
        {
        }
    }
Add object function
INamedCache cache = CacheFactory.GetCache("dist-Person");
for (int i = 0; i < 1000; i++)
{
cache.Add(i, new Person()
{
   ID = i,
   FirstName = string.Format("First Name {0}", i),
   LastName = string.Format("LastName {0}", i),
   Address = string.Format("Address {0}" , Guid.NewGuid()) ,
   Title = i % 2  == 1 ? "Mr" : "Mrs"
   });
}

Query using Linq Query:

CoherenceQuery<Person> coherenceData =
 new CoherenceQuery<Person>(
	 new CoherenceQueryProvider(CacheFactory.GetCache("dist-Person"), 
		 new MetadataCoherenceQueryTranslator()));
string likeClause = "%8";
var people = from person in coherenceData
			 where
				(person.FirstName.Like("Test")
				 || person.LastName.Like(likeClause))
				 && person.Title == "Mrs"
			 select new { person.Title, person.ID, person.LastName };
IFilter filter = ((ICoherenceQueryable)people).Filter;
dataGridView1.DataSource = people.ToArray();

Internally, MetadataCoherenceQueryTranslator, will convert the linq query into a filter and execute the query against the Java POFGenericObject


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