Getting Method threw 'java.util.NoSuchElementException' exception.

[sharma-kunal]

I have my Janusgraph Schema defined like this,

        management.makePropertyKey("name").dataType(String.class).make();
        management.makePropertyKey("p_uuid").dataType(String.class).make();
        management.makePropertyKey("site_context").dataType(String.class).make();
        management.makePropertyKey("company_name").dataType(String.class).make();
        management.makePropertyKey("start_date").dataType(Date.class).make();
        management.makePropertyKey("end_date").dataType(Date.class).make();
        management.makePropertyKey("current").dataType(Integer.class).make();

management.buildIndex("seeker", Vertex.class).addKey(management.getPropertyKey("p_uuid"))
                .indexOnly(management.getVertexLabel("seeker"))
                .buildCompositeIndex();
        management.buildIndex("company", Vertex.class).addKey(management.getPropertyKey("company_name"))
                .indexOnly(management.getVertexLabel("company"))
                .buildCompositeIndex();

Now I have inserted data in my graph,

when I query the graph like

g.V('<id>').valueMap().next()

I get the response

p_uuid: <value>
name: <name>
site_context: <site_context>

but when I do like this,

g.V().hasLabel("seeker").has("p_uuid", <p_uuid>).next()

It fails with the error

Method threw 'java.util.NoSuchElementException' exception.

But if I do

g.V().hasLabel("seeker").has("name", <name>).next()
or
g.V().hasLabel("seeker").has("site_context", <site_context>).next()

Since it is returning p_uuid when using valueMap() but when I do I search query with the has() method, why does it fails with 'java.util.NoSuchElementException ?

What am I missing here ?

[sheeehy]

The java.util.NoSuchElementException occurs when the traversal has no elements to provide in the result set. It means that the graph does not contain a vertex with label "seeker" and property "p_uuid" set to the value you provided in <p_uuid>.

Here are some common reasons why you might be running into this issue:

Data Consistency: The p_uuid value you are searching for may not exist in the database at the time of query execution. Double-check the values by executing g.V().hasLabel("seeker").valueMap().toList().

Commit: If you have recently added elements to the graph, make sure that you have committed the transaction to make them visible to queries.

Indexing: Ensure that your index on p_uuid for the label "seeker" is enabled and properly constructed. Indexes sometimes take a while to become effective.

Case Sensitivity: Property keys are usually case-sensitive. Double-check that the case of p_uuid in your has query matches exactly with the one in the graph.

Type Matching: Ensure that the data type of the value you are passing in has("p_uuid", <p_uuid>) is a String, as defined in your schema.

Graph Cache: Sometimes, if there is any kind of caching involved, clearing the cache can help.

[sharma-kunal]

I found the issue here. I am not sure if this is an issue with Janusgraph or not, let me specify the details here.

So I am using Cassandra as my backend. I deleted my keyspace in cassandra using the command

drop keyspace

After which I ran my code, that created the new keyspace with the same schema that was previously created.

But when I ran the queries on this new keyspace using Janusgraph, all fields that were part of composite index failed with the above error.

The solution was to just restart the Janusgraph server once.

I am not sure if I should delete the backend storage as I did with the drop keyspace command, but if it's the wrong way to delete the backend storage and composite index, then it should be specified in the documentation.