OrientDB Traverse Functionality

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