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Posted to commits@tinkerpop.apache.org by sp...@apache.org on 2017/01/18 11:36:16 UTC
[02/24] tinkerpop git commit: Added more content to traversal induced
value recipe
Added more content to traversal induced value recipe
Project: http://git-wip-us.apache.org/repos/asf/tinkerpop/repo
Commit: http://git-wip-us.apache.org/repos/asf/tinkerpop/commit/e1d5b686
Tree: http://git-wip-us.apache.org/repos/asf/tinkerpop/tree/e1d5b686
Diff: http://git-wip-us.apache.org/repos/asf/tinkerpop/diff/e1d5b686
Branch: refs/heads/TINKERPOP-1600
Commit: e1d5b686172aa4caed3429adf04802fb3ef62a07
Parents: 6dba5ec
Author: Stephen Mallette <sp...@genoprime.com>
Authored: Fri Jan 6 11:48:40 2017 -0500
Committer: Stephen Mallette <sp...@genoprime.com>
Committed: Fri Jan 6 11:48:40 2017 -0500
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.../recipes/traversal-induced-values.asciidoc | 49 +++++++++++++++++++
docs/static/images/eulerian-circuit.png | Bin 0 -> 25270 bytes
.../images/traversal-induced-values-1.png | Bin 0 -> 12607 bytes
.../images/traversal-induced-values-2.png | Bin 0 -> 40440 bytes
.../images/traversal-induced-values-3.png | Bin 0 -> 49652 bytes
5 files changed, 49 insertions(+)
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http://git-wip-us.apache.org/repos/asf/tinkerpop/blob/e1d5b686/docs/src/recipes/traversal-induced-values.asciidoc
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diff --git a/docs/src/recipes/traversal-induced-values.asciidoc b/docs/src/recipes/traversal-induced-values.asciidoc
index e292e16..03affbe 100644
--- a/docs/src/recipes/traversal-induced-values.asciidoc
+++ b/docs/src/recipes/traversal-induced-values.asciidoc
@@ -56,6 +56,55 @@ g.V().has('name','marko').as('marko'). <1>
<3> Continue to traverser only if Marko's current friend is older than him.
<4> Get the name of Marko's older friend.
+As another example of how traversal induced values can be used, consider a scenario where there was a graph that
+contained people, their friendship relationships, and the movies that they liked.
+
+image:traversal-induced-values-3.png[width=600]
+
+[gremlin-groovy]
+----
+g.addV("name", "alice", label, "user").as("u1").
+ addV("name", "jen", label, "user").as("u2").
+ addV("name", "dave", label, "user").as("u3").
+ addV("name", "the wild bunch", label, "movie").as("m1").
+ addV("name", "young guns", label, "movie").as("m2").
+ addV("name", "unforgiven", label, "movie").as("m3").
+ addE("friend").from("u1").to("u2").
+ addE("friend").from("u1").to("u3").
+ addE("like").from("u2").to("m1").
+ addE("like").from("u2").to("m2").
+ addE("like").from("u3").to("m2").
+ addE("like").from("u3").to("m3").iterate()
+----
+
+Getting a list of all the movies that Alice's friends like could be done like this:
+
+[gremlin-groovy,existing]
+----
+g.V().has('name','alice').out("friend").out("like").values("name")
+----
+
+but what if there was a need to get a list of movies that *all* her Alice's friends liked. In this case, that would
+mean filtering out "the wild bunch" and "unforgiven".
+
+[gremlin-groovy,existing]
+----
+g.V().has("name","alice").
+ out("friend").aggregate("friends"). <1>
+ out("like").dedup(). <2>
+ filter(__.in("like").where(within("friends")).count().as("a"). <3>
+ select("friends").count(local).where(eq("a"))). <4>
+ values("name")
+----
+
+<1> Gather Alice's list of friends to a list called "friends".
+<2> Traverse to the unique list of movies that Alice's friends like.
+<3> Remove movies that weren't liked by all friends. This starts by taking each movie and traversing back in on the
+"like" edges to friends who liked the movie (note the use of `where(within("friends"))` to limit those likes to only
+Alice's friends as aggregated in step one) and count them up into "a".
+<4> Count the aggregated friends and see if the number matches what was stored in "a" which would mean that all friends
+like the movie.
+
Traversal induced values are not just for filtering. They can also be used when writing the values of the properties
of one `Vertex` to another:
http://git-wip-us.apache.org/repos/asf/tinkerpop/blob/e1d5b686/docs/static/images/eulerian-circuit.png
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