Edges are not deleted after Node is removed

[qohelet]

In the documentation of python-arangod it's stated:

If a vertex is deleted, all connected edges are also automatically deleted.

So I'm not sure if "vertex" in this case refers to the vertex-collection or a single document. Any way, when removing a document with:
db = self.client.db(self.DB, username=self.user, password=self.password) if db.has_collection(col_name): col = db.collection(col_name) col.delete(id)

Only the document is removed but the edges remain.
Is this a bug or supposed to be? Also if I want to remove a node with all the edges is there a different command for that or is it supposed to be done with Graph traversals?

[TariqAHassan]

@qohelet

I'm not sure that this will solve your problem, but try looking here.

Assuming you have defined a graph, then the graph interface should remove a vertex's adjacent edges.

[joowani]

Hi @qohelet,

Yes as @TariqAHassan pointed out you will need to use vertex collection API wrapper to remove the vertex.

[qohelet]

I'm afraid I not able I'm understanding what you're trying to tell me.
Is the edge removed after I remove the vertex like I did? If now, how should I remove it properly?

[wshayes]

@qohelet You can create an edge collection without it being part of a defined graph - see https://python-driver-for-arangodb.readthedocs.io/en/master/graph.html and https://www.arangodb.com/docs/stable/aql/graphs.html (see the two methods). If you did not set up the vertex/edge collections as a defined graph, you have to manage the edges/vertexes addition/deletion more manually.

[qohelet]

@wshayes - I know how to set up an Edge collection and that had never been my question.

I want to know how to delete a vertex and have all its edges removed in the same operation.
With my code it's not working (despite the manual states it). So how is the proper way to do it?

[wshayes]

From: https://www.arangodb.com/docs/stable/graphs.html#named-graphs

"Your edge collections will only contain valid edges and you will never have loose ends. These guarantees are lost if you access the collections in any other way than the graph module, so if you delete documents from your vertex collections directly, the edges pointing to them will remain in place."

[wshayes]

You talk about setting up an edge collection but not how you did it - did you do it as a named graph or just as an edge collection (e.g. anonymous graph). I typically use anonymous graphs and manage edges/vertices myself.

[joowani]

Hi @qohelet,

Sorry for the late reply. Let me give you an example code to clarify.

from arango import ArangoClient

client = ArangoClient()

client.db('_system', username='root', password='passwd').create_database('test')

# Connect to "test" database as root user.
db = client.db('test', username='root', password='passwd')

school = db.create_graph('school')
lectures = school.create_vertex_collection('lectures')
teachers = school.create_vertex_collection('teachers')
gives = school.create_edge_definition(
    edge_collection='gives',
    from_vertex_collections=['teachers'],
    to_vertex_collections=['lectures']
)

# Insert vertices into the graph.
teachers.insert({'_key': 'jon', 'name': 'Professor jon'})
lectures.insert({'_key': 'CSC101', 'name': 'Introduction to CS'})
lectures.insert({'_key': 'MAT223', 'name': 'Linear Algebra'})
lectures.insert({'_key': 'STA201', 'name': 'Statistics'})

# Insert edges into the graph.
gives.insert({'_from': 'teachers/jon', '_to': 'lectures/CSC101'})
gives.insert({'_from': 'teachers/jon', '_to': 'lectures/STA201'})
gives.insert({'_from': 'teachers/jon', '_to': 'lectures/MAT223'})

# Delete a vertex with edges (all of them in this case).
teachers.delete('jon')

# Now the edges collection should be empty.
assert len(gives) == 0

What you need is to use the vertex collection API wrapper:

# Correct
client.database('database_name').graph('graph_name').vertex_collection('colllection_name')

and NOT the standard collection wrapper:

# Incorrect
client.database('database_name').collection('collection_name')

I know it's a bit confusing but that's how ArangoDB's REST API is designed.

[joowani]

Closing due to inactivity, feel free to reopen if you have any more questions. Thanks