OrientDB 遍历功能

Question

我想选择所有连接到另一个顶点的顶点。我目前在 OrientDB 中使用traverse 函数。考虑以下示例：

> 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]'

现在，当我尝试遍历以查找 Smith 教授教授的课程时，我使用以下命令：

> 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
----+-----+---------+-----+-----------+-----+-----

为什么这会将边缘而不是我正在寻找的顶点（路线）返回给我？将顶点返回给我的适当命令是什么？我希望返回“微积分”的记录。

Answer 1

我稍微扩展了您的图表以尝试您的查询。

如果您只想知道边“教导”与某个起始顶点的连接顶点，您应该使用SELECT EXPAND (OUT / IN / BOTH)，因为如果您希望探索不同深度的图形，TRAVERSE 更有用（在我的情况下“史密斯”有@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]
----+-----+------+------------+----------+----------

或使用select expand(out('teaches')) from #11:0，您将获得相同的结果：

----+-----+------+------------+----------+----------
#   |@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]
----+-----+------+------------+----------+----------

或者你可以获得所有连接到教授“Smith”的顶点

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]
----+-----+----------+------------+----------+----------+------------+----------

您的查询traverse out_teaches from #11:0 似乎列出了起始顶点和所有具有相对IN 和OUT 顶点的连接边：

----+-----+---------+-----+-----------+-----------+-----+-----
#   |@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
----+-----+---------+-----+-----------+-----------+-----+-----

我也试过traverse out_teaches from professor，结果和上一个查询类似：

----+-----+---------+-----+-----------+-----------+-----+-----
#   |@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

选择课程的正确语法（至少在 OrientDB 2.1 中）将基于 out('teaches')。例如：

> select expand(out('teaches')) from (select from Professor where name='Smith')

----+-----+------+--------+----------
#   |@RID |@CLASS|name    |in_teaches
----+-----+------+--------+----------
0   |#12:0|Course|Calculus|[size=1]  
----+-----+------+--------+----------

也就是说，正如预期的那样，只有一个顶点。

请注意，“traverse”用于不同的目的。它涉及遍历图的迭代过程。

out_teaches

“out_teaches”是对边的引用。使用 OrientDB 2.1.7，我为您的“out_teaches”查询获得的响应如下：

> select expand(out_teaches) from (select from Professor where name='Smith')

----+-----+-------+-----+-----
#   |@RID |@CLASS |out  |in   
----+-----+-------+-----+-----
0   |#13:0|teaches|#11:0|#12:0
----+-----+-------+-----+-----

再一次，这是人们所期望的 - 优势。

Answer 3

您的查询对我来说很好。

在我的情况下，我的教授是 #11:0，课程是 #12:0，教师是 #13:0

再次重新运行您的查询或尝试以下操作：

从 #12:0 开始遍历两个（'teaches'）