text: t = db.array1;
  t.drop();
  
  x = {
      a: [1, 2]
  };
  
  t.save({a: [[1, 2]]});
  assert.eq(1, t.find(x).count(), "A");
  
  t.save(x);
  delete x._id;
  assert.eq(2, t.find(x).count(), "B");
  
  t.ensureIndex({a: 1});
  assert.eq(2, t.find(x).count(), "C");  // TODO SERVER-146
  