Why is T.label immutable and do we have to create a new node to change a label?

We cannot do g.V('some label').property(T.label, 'new label').iterate() ? Is this correct? Thank you

Solution

you have a few questions here @Julius Hamilton

Why is T.label immutable

i'm not sure there's a particular reason except to say that many graphs have not allowed that functionality so TinkerPop hasn't offered a way to do it.

and do we have to create a new node to change a label?

yes

We cannot do g.V('some label').property(T.label, 'new label').iterate()

no, because you can't modify the label as mentioned earlier, but also

V()

V()

V()

V() does not take a

label

label

as an argument. it would be more correct to do

g.V().hasLabel('some label').property(...)

g.V().hasLabel('some label').property(...)

g.V().hasLabel('some label').property(...)

g.V().hasLabel('some label').property(...) to modify all things with a particular label (but, again

label

label

and

id

id

cannot be one of those things. you'd have to sort of clone the vertex. there are some patterns for doing it: https://stackoverflow.com/q/51900116/1831717

also, in the future, i think a mutable label probably should be allowed. we'll see how that comes to pass.

Stack Overflow

gremlin clone a node and its edges

Does gremlin provide the ability to clone a vertex for instance
v1->v2, v1->v3, v1->v4 how can I simply and efficiently create a new vertex v5 that also has edges that point to v2, v3, v4 ...

Jump to solution

pieter•9/24/24, 5:04 PM

Hi,
Gremlin has no support for managing a graph's schema, so what you are doing is wrong.

Solution

spmallette•9/24/24, 5:41 PM

you have a few questions here @Julius Hamilton

Why is T.label immutable

i'm not sure there's a particular reason except to say that many graphs have not allowed that functionality so TinkerPop hasn't offered a way to do it.

and do we have to create a new node to change a label?

yes

We cannot do g.V('some label').property(T.label, 'new label').iterate()

no, because you can't modify the label as mentioned earlier, but also

V()

V()

does not take a

label

label

as an argument. it would be more correct to do

g.V().hasLabel('some label').property(...)

g.V().hasLabel('some label').property(...)

to modify all things with a particular label (but, again

label

label

and

id

id

Stack Overflow

gremlin clone a node and its edges

Does gremlin provide the ability to clone a vertex for instance
v1->v2, v1->v3, v1->v4 how can I simply and efficiently create a new vertex v5 that also has edges that point to v2, v3, v4 ...

pieter•9/24/24, 5:44 PM

What you are doing, I think of as a renameVertexLabelrenameVertexLabel operation. Most graphs have a custom api to handle such things.

Ppieter What you are doing, I think of as a `renameVertexLabel` operation. Most graphs h...

spmallette•9/24/24, 7:37 PM

didn't really think too hard about it, but shouldn't we just allow property(label, 'new-label')property(label, 'new-label') to work?

Sspmallette didn't really think too hard about it, but shouldn't we just allow `property(lab...

pieter•9/24/24, 8:02 PM

I'd prefer a more dedicated approach. An api (gremlin lang) that deals with schema creation and modification.

Gremlin comes with a implicit meta model, which can be supported fairly easily. We need to leave some extension points for all the implementation specific details that exist outside of Gremlin's meta model.
Stuff like partitions, gis, strange data types and ...

What I have in mind is something like,

graph.schema()
    .ensureVertexLabelExist('Person")
    .ensurePropertyExist('name', "namespace.String", additionalParameters...)
    .ensurePropertyExist('surname', "namespace.String", additionalParameters...)

graph.schema()
    .ensureVertexLabelExist('Person")
    .ensurePropertyExist('name', "namespace.String", additionalParameters...)
    .ensurePropertyExist('surname', "namespace.String", additionalParameters...)

From what I have seen this is the approach most implementations have taken.

Ppieter I'd prefer a more dedicated approach. An api (gremlin lang) that deals with sche...

spmallette•9/24/24, 11:27 PM

i see...you're thinking of a bigger picture and one that fits the specific nature of the OP's question about changing the label for all vertices of a particular label. you might just want to do that from a schema perspective, whre you are modifying the schema as a whole. i still think there is a Gremlin component though where you just want to do g.V(1).property(label, 'new-label')g.V(1).property(label, 'new-label') and just change it for one vertex.

Sspmallette i see...you're thinking of a bigger picture and one that fits the specific natur...

pieter•9/25/24, 6:40 AM

"g.V(1).property(label, 'new-label')g.V(1).property(label, 'new-label') and just change it for one vertex"

I see this as a,

g.schema().ensureVertexLabelExist('new-label', ... all label properties ...)
g.V().addVertex('new-label', ......)  //copy the vertex over
g.V(1).drop().iterate()
g.tx().commit()

g.schema().ensureVertexLabelExist('new-label', ... all label properties ...)
g.V().addVertex('new-label', ......)  //copy the vertex over
g.V(1).drop().iterate()
g.tx().commit()

On SqlgSqlg at least only some rdbms support transactional schema changes, which means its best to handle the schema outside of the data.

pieter•9/25/24, 8:06 AM

Actually come to think of it, the above is wrong, as it needs to migrate all edges attached to the vertex also.

spmallette•9/25/24, 11:36 AM

yeah, i see that in sqlg's case you have a situation where changing the label for one vertex isn't quite as direct as something like TinkerGraph where it's probably just:
vertex.setLabel("new-label")vertex.setLabel("new-label")
which updates a member variable.

pieter•9/25/24, 11:49 AM

Yeah, I'd suggest that TinkerGraphTinkerGraph not be used as a guide for schema/meta management but rather JanusJanus, ArcadeGraphArcadeGraph and others.

Dave•9/25/24, 1:57 PM

@Julius Hamilton What database are you using? Amazon Neptune does allow you to have multiple labels but the syntax is different.

triggan•9/27/24, 12:16 PM

Also to Dave's point, while Gremlin doesn't allow for you to change a label on a node, openCypher does. There are a lot of interoperability aspects that have driven how Neptune supports labels.

Using multiple labels in Gremlin on Neptune: https://docs.aws.amazon.com/neptune/latest/userguide/access-graph-gremlin-differences.html#feature-gremlin-differences-labels

You can change a label on a vertex/node in openCypher via:

MATCH (n)
WHERE id(n) = '96c90f92-9aef-6f62-14c6-b1882b66188c'
SET n:newuser
REMOVE n:user
RETURN n

MATCH (n)
WHERE id(n) = '96c90f92-9aef-6f62-14c6-b1882b66188c'
SET n:newuser
REMOVE n:user
RETURN n

( where the old label is

user

user

and new label is newusernewuser )

This also brings up the point that openCypher supports the ability to do this, while Gremlin does not. So likely a gap that Gremlin needs to address even without addressing this from a schema/constraint standpoint.

Gremlin standards compliance in Amazon Neptune - Amazon Neptune

Overview of differences between the Neptune and TinkerPop implementations of Gremlin.

pieter•9/27/24, 12:25 PM

Are labels on Neptune more like a tag, i.e. different vertices with the same label might have completely different properties?

triggan•9/27/24, 12:36 PM

Neptune has very few constraints. Primarily only that each vertex and edge must have a unique ID (and those IDs must be a String). Each vertex and edge must have a label (though if not defined at creation, a label of vertexvertex or edgeedge is used). And that every edge must have a vertex at either end of the edge. Outside of that, there are no constraints on what properties a vertex/edge must have, data types, etc.

pieter•9/27/24, 12:40 PM

Ok and that it not just saying that all properties are optional, but that they can have different types even if they are on the same label?

label: 'Person', "ID": 1, name: "John"
label: 'Person', "ID": 2, name: 1L

This kind of modelling is ok?

triggan•9/27/24, 12:44 PM

"Ok" is of opinion. It's entirely possible and a tradeoff in supporting multiple frameworks and query languages.

pieter•9/27/24, 12:45 PM

Ok, thanks

Why is T.label immutable and do we have to create a new node to change a label?

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