text: // Check null key generation.
  
  t = db.jstests_indexv;
  t.drop();
  
  t.ensureIndex( {'a.b':1} );
  
  t.save( {a:[{},{b:1}]} );
  var e = t.find( {'a.b':null} ).explain();
  assert.eq( 1, e.n );
  assert.eq( 1, e.nscanned );
  
  t.drop();
  t.ensureIndex( {'a.b.c':1} );
  t.save( {a:[{b:[]},{b:{c:1}}]} );
  var e = t.find( {'a.b.c':null} ).explain();
  assert.eq( 0, e.n );
  assert.eq( 1, e.nscanned );
  