OrientDB Traverse Functionality - orientdb

Question

I want to select all vertices that are connected to another vertex. I am currently using the traverse function in OrientDB. Consider the following example:
> create class professor extends V
> create class course extends V
> insert into professor set name='Smith'
Inserted record 'professor#14:0{name:Smith} v1'
> insert into course set name='Calculus'
Inserted record 'course#15:0{name:Calculus} v1'
> create class teaches extends E
> create edge teaches from #14:0 to #15:0
Created edge '[teaches#16:0{out:#14:0,in:#15:0} v3]'
Now when I try to traverse to find the course(s) that professor Smith teaches I use the following command:
> traverse out_teaches from #15:0
----+-----+---------+-----+-----------+-----+-----
# |#RID |#CLASS |name |out_teaches|out |in
----+-----+---------+-----+-----------+-----+-----
0 |#14:0|professor|Smith|[size=1] |null |null
1 |#16:0|teaches |null |null |#14:0|#15:0
----+-----+---------+-----+-----------+-----+-----
Why does this return to me the edge and not the vertex (course) that I am looking for? What is the appropriate command to return to me the vertex? I want the record for 'Calculus' to be returned.

Answer 1

I expanded your graph a bit to try your query.
If you want to know only the connected vertices to some starting vertex by the edge 'teaches' you should use SELECT EXPAND (OUT / IN / BOTH) because TRAVERSE is more useful if you wish to explore the graph at different depths (in my case "Smith" has the #rid #11:0):
select expand(out('teaches')) from (select from Professor where name='Smith')
----+-----+------+------------+----------+----------
# |#RID |#CLASS|name |in_teaches|in_follows
----+-----+------+------------+----------+----------
0 |#12:0|course|Calculus |[size=1] |[size=1]
1 |#12:1|course|Astrophysics|[size=1] |[size=1]
2 |#12:2|course|Law |[size=2] |[size=1]
----+-----+------+------------+----------+----------
or with select expand(out('teaches')) from #11:0 you will obtain the same result:
----+-----+------+------------+----------+----------
# |#RID |#CLASS|name |in_teaches|in_follows
----+-----+------+------------+----------+----------
0 |#12:0|course|Calculus |[size=1] |[size=1]
1 |#12:1|course|Astrophysics|[size=1] |[size=1]
2 |#12:2|course|Law |[size=2] |[size=1]
----+-----+------+------------+----------+----------
or you can obtain all the connected vertices to the professor "Smith"
select expand(out()) from professor where name="Smith"
----+-----+----------+------------+----------+----------+------------+----------
# |#RID |#CLASS |name |in_teaches|in_follows|in_studiesAt|in_worksAt
----+-----+----------+------------+----------+----------+------------+----------
0 |#12:0|course |Calculus |[size=1] |[size=1] |null |null
1 |#12:1|course |Astrophysics|[size=1] |[size=1] |null |null
2 |#12:2|course |Law |[size=2] |[size=1] |null |null
3 |#16:0|university|Cambridge |null |null |[size=1] |[size=1]
----+-----+----------+------------+----------+----------+------------+----------
Your query traverse out_teaches from #11:0 seems to list the starting vertex and all of the connected edges with relative IN and OUT vertices:
----+-----+---------+-----+-----------+-----------+-----+-----
# |#RID |#CLASS |name |out_teaches|out_worksAt|out |in
----+-----+---------+-----+-----------+-----------+-----+-----
0 |#11:0|professor|Smith|[size=3] |[size=1] |null |null
1 |#13:0|teaches |null |null |null |#11:0|#12:0
2 |#13:1|teaches |null |null |null |#11:0|#12:1
3 |#13:2|teaches |null |null |null |#11:0|#12:2
----+-----+---------+-----+-----------+-----------+-----+-----
I tried also traverse out_teaches from professor and the result is similar to the previous query:
----+-----+---------+-----+-----------+-----------+-----+-----
# |#RID |#CLASS |name |out_teaches|out_worksAt|out |in
----+-----+---------+-----+-----------+-----------+-----+-----
0 |#11:0|professor|Smith|[size=3] |[size=1] |null |null
1 |#13:0|teaches |null |null |null |#11:0|#12:0
2 |#13:1|teaches |null |null |null |#11:0|#12:1
3 |#13:2|teaches |null |null |null |#11:0|#12:2
4 |#11:1|professor|Green|[size=1] |[size=1] |null |null
5 |#13:3|teaches |null |null |null |#11:1|#12:2
----+-----+---------+-----+-----------+-----------+-----+-----

Answer 2

The correct syntax for selecting the courses (at least in OrientDB 2.1) would be based on out('teaches'). For example:
> select expand(out('teaches')) from (select from Professor where name='Smith')
----+-----+------+--------+----------
# |#RID |#CLASS|name |in_teaches
----+-----+------+--------+----------
0 |#12:0|Course|Calculus|[size=1]
----+-----+------+--------+----------
That is, there's just one vertex, as expected.
Please note that 'traverse' is used for a different purpose. It involves an iterative procedure for traversing graphs.
out_teaches
"out_teaches" is a reference to an edge. Using OrientDB 2.1.7, the response I obtained for your "out_teaches" query is as follows:
> select expand(out_teaches) from (select from Professor where name='Smith')
----+-----+-------+-----+-----
# |#RID |#CLASS |out |in
----+-----+-------+-----+-----
0 |#13:0|teaches|#11:0|#12:0
----+-----+-------+-----+-----
Again, this is what one would expect - an edge.

Answer 3

Your query is working fine for me.
In my case I have the rid as #11:0 for professor, #12:0 for course and #13:0 for teaches
Just rerun your query once again or try the below :
traverse both('teaches') from #12:0