MongoDB Composite Key

Question

I\'m just getting started with MongoDb and I\'ve noticed that I get a lot of duplicate records for entries that I meant to be unique. I would like to know how to use a compo

Answer 1

I just noticed that the question is marked as "java", so you'd want to do something like:

final BasicDBObject id = new BasicDBObject("a", aVal)
        .append("b", bVal)
        .append("c", cVal);
results = coll.find(new BasicDBObjet("_id", id));

I use Morphia too, but have found (that while it works) it generates lots of errors as it tries to marshall the composite key. I use the above when querying to avoid these errors.

My original code (which also works):

final ProbId key = new ProbId(srcText, srcLang, destLang);
final QueryImpl query = ds.createQuery(Probabilities.class)
  .field("id").equal(key);
Probabilities probs = (Probabilities) query.get();

My ProbId class is annotated as @Entity(noClassnameStored = true) and inside the Probabilities class, the id field is @Id ProbId id;