Github user dkuppitz commented on a diff in the pull request:
https://github.com/apache/tinkerpop/pull/531#discussion_r95637868
--- Diff: docs/src/recipes/appendix.asciidoc ---
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+////
+Licensed to the Apache Software Foundation (ASF) under one or more
+contributor license agreements. See the NOTICE file distributed with
+this work for additional information regarding copyright ownership.
+The ASF licenses this file to You under the Apache License, Version 2.0
+(the "License"); you may not use this file except in compliance with
+the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+////
+Appendix
+========
+
+Many of the recipes are based on questions and answers provided on the
gremlin-users mailing list. This section
+contains a number of traversals from the mailing list that do not easily
fit any particular pattern (i.e. a recipe),
+but are nonetheless interesting and thus remain good tools for learning
Gremlin.
+
+[[appendix-a]]
+_For each person in a "follows" graph, determine the number of followers
and list their names._
+
+[gremlin-groovy]
+----
+g.addV('name','marko').as('marko').
+ addV('name','josh').as('josh').
+ addV('name','daniel').as('daniel').
+ addV('name','matthias').as('matthias').
+ addE('follows').from('josh').to('marko').
+ addE('follows').from('matthias').to('josh').
+ addE('follows').from('daniel').to('josh').
+ addE('follows').from('daniel').to('marko').iterate()
+g.V().as('p').
+ map(__.in('follows').values('name').fold()).
+ group().by(select('p').by('name')).
+ by(project('numFollowers','followers').
+ by(count(local)).by()).next()
+----
+
+[[appendix-b]]
+_In the "modern" graph, show each person, the software they worked on and
the co-worker count for the software and
+the names of those co-workers._
+
+[gremlin-groovy,modern]
+----
+g.V().hasLabel("person").as("p").
+ out("created").as("s").
+ map(__.in("created").
+ where(neq("p")).values("name").fold()).
+ group().by(select("p").by("name")).
+ by(group().by(select("s").by("name")).
+ by(project("numCoworkers","coworkers").
+ by(count(local)).by())).next()
+----
+
+[[appendix-c]]
+_Assuming a graph of students, classes and times, detect students who have
a conflicting schedule._
+
+[gremlin-groovy]
+----
+g.addV(label, "student", "name", "Pete").as("s1").
+ addV(label, "student", "name", "Joe").as("s2").
+ addV(label, "class", "name", "Java's GC").as("c1").
+ addV(label, "class", "name", "FP Principles").as("c2").
+ addV(label, "class", "name", "Memory Management in C").as("c3").
+ addV(label, "class", "name", "Memory Management in C++").as("c4").
+ addV(label, "timeslot", "date", "11/25/2016", "fromTime", "10:00",
"toTime", "11:00").as("t1").
+ addV(label, "timeslot", "date", "11/25/2016", "fromTime", "11:00",
"toTime", "12:00").as("t2").
+ addE("attends").from("s1").to("c1").
+ addE("attends").from("s1").to("c2").
+ addE("attends").from("s1").to("c3").
+ addE("attends").from("s1").to("c4").
+ addE("attends").from("s2").to("c2").
+ addE("attends").from("s2").to("c3").
+ addE("allocated").from("c1").to("t1").
+ addE("allocated").from("c1").to("t2").
+ addE("allocated").from("c2").to("t1").
+ addE("allocated").from("c3").to("t2").
+ addE("allocated").from("c4").to("t2").iterate()
+g.V().hasLabel("student").as("s").
+ out("attends").as("c").
+ out("allocated").as("t").
+ select("s").
+ out("attends").
+ where(neq("c")).
+ out("allocated").
+ where(eq("t")).
+ group().
+ by(select("s").by("name")).
+ by(group().by(select("t").by(valueMap("fromTime","toTime"))).
+ by(select("c").dedup().values("name").fold())).next()
+----
+
+[[appendix-d]]
+_In the "modern" graph, with a duplicate edge added, find the vertex pairs
that have more than one edge between them._
+
+[gremlin-groovy,modern]
+----
+g.V(1).as("a").V(3).addE("created").property("weight",0.4d).from("a").iterate()
+g.V(1).outE("created")
+g.V().as("a").
+ out().as("b").
+ groupCount().
+ by(select("a","b")).
+ unfold().
+ filter(select(values).is(gt(1))).
+ select(keys)
+----
+
+[[appendix-e]]
+_In the "crew" graph, find vertices that match on a complete set of
multi-properties._
+
+[gremlin-groovy,theCrew]
+----
+places = ["centreville","dulles"];[] // will not match as "purcellville"
is missing
+g.V().not(has("location", without(places))).
+ where(values("location").is(within(places)).count().is(places.size())).
+ valueMap()
+places = ["centreville","dulles","purcellville"];[]
+g.V().not(has("location", without(places))).
+ where(values("location").is(within(places)).count().is(places.size())).
+ valueMap()
+----
+
+[[appendix-f]]
+_Methods for performing some basic mathematical operations in the "modern"
graph._
+
+[gremlin-groovy,modern]
+----
+g.V().values("age").sum() // sum all ages
+g.V().values("age").fold(1, mult) // multiply all ages
+g.V().values("age").map(union(identity(), constant(-1)).sum()) // subtract
1
+g.V().values("age").map(union(identity(), identity()).sum()) // multiply
by 2 (simple)
+g.V().values("age").map(union(identity(), constant(2)).fold(1, mult)) //
multiply by 2 (generally useful for multiplications by n):
+----
+
+[[appendix-g]]
+_Dropping a vertex, as well as the vertices related to that dropped vertex
that are connected by a "knows" edge in the
+"modern" graph_
+
+[gremlin-groovy,modern]
+----
+g.V().has('name','marko').outE()
+g.V().has('name','marko').sideEffect(out('knows').drop()).drop()
+g.V().has('name','marko')
+g.V(2,4,3)
+----
+
+[[appendix-h]]
+_For the specified graph, find all neighbor vertices connected to "A" as
filtered by datetime, those neighbor vertices
+that don't have datetime vertices, and those neighbor vertices that have
the label "dimon"._
+
+[gremlin-groovy]
+----
+g.addV().property("name", "A").as("a").
+ addV().property("name", "B").as("b").
+ addV().property("name", "C").as("c").
+ addV().property("name", "D").as("d").
+ addV().property("name", "E").as("e").
+ addV("dimon").property("name", "F").as("f").
+ addV().property("name", "G").as("g").property("date", 20160818).
+ addV().property("name", "H").as("h").property("date", 20160817).
+ addE("rel").from("a").to("b").
+ addE("rel").from("a").to("c").
+ addE("rel").from("a").to("d").
+ addE("rel").from("a").to("e").
+ addE("rel").from("c").to("f").
+ addE("occured_at").from("d").to("g").
+ addE("occured_at").from("e").to("h").iterate()
+// D and E have a valid datetime
+g.V().has("name", "A").out("rel").
+ union(where(out("occured_at").has("date", gte(20160817))),
+ __.not(outE("occured_at")).coalesce(out().hasLabel("dimon"),
identity())).
+ valueMap()
+// only E has a valid date
+g.V().has("name", "A").out("rel").
+ union(where(out("occured_at").has("date", lte(20160817))),
+ __.not(outE("occured_at")).coalesce(out().hasLabel("dimon"),
identity())).
+ valueMap()
+// only D has a valid date
+g.V().has("name", "A").out("rel").
+ union(where(out("occured_at").has("date", gt(20160817))),
+ __.not(outE("occured_at")).coalesce(out().hasLabel("dimon"),
identity())).
+ valueMap()
+// neither D nor E have a valid date
+g.V().has("name", "A").out("rel").
+ union(where(out("occured_at").has("date", lt(20160817))),
+ __.not(outE("occured_at")).coalesce(out().hasLabel("dimon"),
identity())).
+ valueMap()
+----
+
+[[appendix-i]]
+_Use element labels in a `select`._
+
+[gremlin-groovy,modern]
+----
+g.V(1).as("a").
+ both().
+ map(group().by(label).by(unfold())).as("b").
+ select("a","b").
+ map(union(project("a").by(select("a")), select("b")).
+ unfold().
+ group().
+ by(select(keys)).
+ by(select(values)))
+g.V().as("a").
+ both().
+ map(group().by(label).by(unfold())).as("b").
+ select("a","b").
+ group().
+ by(select("a")).
+ by(select("b").
+ group().
+ by(select(keys)).
+ by(select(values).fold())).
+ unfold().
+ map(union(select(keys).project("a").by(), select(values)).
+ unfold().
+ group().
+ by(select(keys).unfold()).
+ by(select(values).unfold().unfold().fold()))
+----
--- End diff --
Do we want to look good or perform good? You may have noticed it on the
mailing list, I always try to prevent the use of `match()`. There were only a
few questions that I ever answered with a match query and that was only for the
sake of readability.
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