SERVER-12325 Fix FTSSpec traversal logic for subdocuments

Fixed issue where FTSSpec::scoreDocument() would stop deep traversal
of a document when it encountered a weight for the FTSSpec with a
non-String BSON type which also happens to be a parent component of
another weight.

Author: jrassi

src/mongo/db/fts/fts_spec.cpp

@@ -179,7 +179,9 @@ namespace mongo {
                 // weight that could possibly match or be a prefix of dottedName.  And if this
                 // element fails to match, then no subsequent weight can match, since the weights
                 // are lexicographically ordered.
-                Weights::const_iterator i = _weights.lower_bound( dottedName );
+                Weights::const_iterator i = _weights.lower_bound( elem.type() == Object
+                                                                  ? dottedName + '.'
+                                                                  : dottedName );
 
                 // possibleWeightMatch is set if the weight map contains either a match or some item
                 // lexicographically larger than fieldName.  This boolean acts as a guard on

src/mongo/db/fts/fts_spec_test.cpp

@@ -212,6 +212,20 @@ namespace mongo {
             ASSERT( m["book"] < m["sat"] );
         }
 
+        TEST( FTSSpec, ScoreMultipleField2 ) {
+            // Test where one indexed field is a parent component of another indexed field.
+            BSONObj user = BSON( "key" << BSON( "a" << "text" << "a.b" << "text" ) );
+
+            FTSSpec spec( FTSSpec::fixSpec( user ) );
+
+            TermFrequencyMap m;
+            spec.scoreDocument( BSON( "a" << BSON( "b" << "term" ) ),
+                                FTSLanguage::makeFTSLanguage( "english" ).getValue(),
+                                "",
+                                false,
+                                &m );
+            ASSERT_EQUALS( 1U, m.size() );
+        }
 
         TEST( FTSSpec, ScoreRepeatWord ) {
             BSONObj user = BSON( "key" << BSON( "title" << "text" <<