minor additions for strategies and filtering map keys

book/Section-Miscellaneous-Queries-Results.adoc

@@ -4412,6 +4412,17 @@ extremely long time. In many ways the concept of "longest path" can be viewed as
 anti pattern. This is especially true in highly connected graphs of which
 `air-routes` is an example.
 
+As a final point about the prior example, we recall the "<<traversal-strategies>>" 
+section, where we learned that TinkerPop applies some changes to the way a traversal
+is written just before it is iterated to optimize performance where it can. The prior
+example demonstrates a case where certain query patterns will prevent a particular
+strategy from being applied. Normally, the 'repeat().times()' pattern will result in
+the contents of 'repeat' being expanded, where 'repeat(out()).times(2)' becomes, 
+'out().out()' which is more efficient for TinkerPop to execute. But the presence of 
+'dedup()' precludes that transformation to get the query semantics that are 
+presented. This sort of information can become useful when you are looking for your 
+own query optimizations.
+
 [[unwantededges]]
 Finding unwanted parallel edges
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

book/Section-Writing-Gremlin-Queries.adoc

@@ -1755,6 +1755,26 @@ g.V().has('code','AUS').valueMap().select('code','icao','desc')
 [code:[AUS],icao:[KAUS],desc:[Austin Bergstrom International Airport]]
 ----
 
+As an additional example of Gremlin's flexibility, note that you can also restrict 
+the selected keys to all but those you specify.
+
+[source,groovy]
+----
+ g.V('3').valueMap().as('vm').unfold().
+   filter(select(keys).is(without('city','desc')))
+
+country=[US]
+code=[AUS]
+longest=[12250]
+elev=[542]
+icao=[KAUS]
+lon=[-97.6698989868164]
+type=[airport]
+region=[US-TX]
+runways=[2]
+lat=[30.1944999694824]
+----
+
 If you are reading the output of queries that use 'valueMap' on the Gremlin console,
 it is sometimes easier to read the output if you add an 'unfold' step to the end of
 the query as follows. The 'unfold' step will unbundle a collection for us. You will