如何在未知Schema的JanusGraph中获取所有图标签？

Hey there! Let's sort out this label-fetching problem for you. The queries you tried have small syntax issues that are stopping them from working as expected:

• g.V().Label().values(): Gremlin uses lowercase for this method—Label should be label, and values() is redundant because label() already returns the vertex's label value directly.
• g.V().hasLabel().values(): hasLabel() is meant to filter vertices by a specific label, not retrieve labels themselves, so this won't return the list you need.

Correct Gremlin Queries to Fetch Labels #

Here are the working commands you can use:

1. Get all unique vertex labels
   This query retrieves every vertex's label, then removes duplicates to give you a clean list of distinct labels:

   g.V().label().dedup()
   

2. Get all unique vertex AND edge labels
   If you also need edge labels, use union() to combine vertex and edge label results, then deduplicate:

   g.V().label().union(g.E().label()).dedup()
   

Bonus Tip for Specific Databases #

Some graph databases offer optimized ways to fetch labels via their management APIs (instead of traversing all vertices/edges):

• For JanusGraph: Use the management interface to get labels directly with mgmt.getVertexLabels() or mgmt.getEdgeLabels() (note this is a Java API call, not a Gremlin traversal).
• For Neo4j: Use CALL db.labels() for vertex labels and CALL db.relationshipTypes() for edge types (these are Neo4j-specific procedures).

But the Gremlin queries above are universal and will work across any TinkerPop-compliant graph database.

内容的提问来源于stack exchange，提问作者Sagar