banging my head on this one…

I’ve a piece of code like this which wraps JPA Entities into vertices and which wraps JPA Relationships into Edges :

    public GraphTraversalSource modelGraphFromMetamodelGraph(org.jgrapht.Graph<MetamodelVertex, FieldEdge<MetamodelVertex>> entityMetamodelGraph) {
        log.info("Creating model vertex");
        GraphTraversalSource gTS = this.graphTraversalSource.getGraph();
TransactionTemplate tpl = new TransactionTemplate(sourcePlatformTxManager);
        tpl.setReadOnly(true);
        tpl.executeWithoutResult(status -> {
        createVertices(entityMetamodelGraph, gTS);
        createEdges(entityMetamodelGraph, gTS);
});     return gTS;
    }

That works totally fine.

Unfortunately this code throws OOM on big databases thus I’m trying to ‘Stream’ it and make Transactions/Sessions more atomic.

But unfortunately, when I’m modifying this piece of code like this:

public GraphTraversalSource modelGraphFromMetamodelGraph(org.jgrapht.Graph<MetamodelVertex, FieldEdge<MetamodelVertex>> entityMetamodelGraph) {
        log.info("Creating model vertex");
        GraphTraversalSource gTS = this.graphTraversalSource.getGraph();
        createVertices(entityMetamodelGraph, gTS);
        createEdges(entityMetamodelGraph, gTS);
        return gTS;
    }
    private void createVertices(Graph<MetamodelVertex, FieldEdge<MetamodelVertex>> entityMetamodelGraph, GraphTraversalSource graphTraversalSource) {
        log.info("Creating model Vertex");
        TransactionTemplate tpl = new TransactionTemplate(sourcePlatformTxManager);
        tpl.setReadOnly(true);
        tpl.executeWithoutResult(status ->*/
        createVertices(entityMetamodelGraph.vertexSet(), graphTraversalSource);
        );
    }

    void createEdges(Graph<MetamodelVertex, FieldEdge<MetamodelVertex>> entityMetamodelGraph, GraphTraversalSource graphTraversalSource) {
        log.info("Creating model edges");
        TransactionTemplate tpl = new TransactionTemplate(sourcePlatformTxManager);
        tpl.setReadOnly(true);
        tpl.executeWithoutResult(status ->
        modelGraphEdgeBuilder.createEdges(graphTraversalSource, entityMetamodelGraph);
        );
    }

I face a lovely

[ERROR] net.osgiliath.FakerProcessingIT.givenFedGraphWhenEntityProcessorAndSequenceProcessorIsCalledThenTargetDatabaseIsPopulatedExcludingCyclicPathAndFieldsAreTransformed -- Time elapsed: 0.079 s <<< ERROR!
org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: net.osgiliath.datamigrator.sample.domain.JhiUser.jhiAuthorities: could not initialize proxy - no Session
        at org.hibernate.collection.spi.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:634)
        at org.hibernate.collection.spi.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:217)
        at org.hibernate.collection.spi.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:613)
        at org.hibernate.collection.spi.AbstractPersistentCollection.read(AbstractPersistentCollection.java:136)
        at org.hibernate.collection.spi.PersistentSet.iterator(PersistentSet.java:166)
        at java.base/java.util.Spliterators$IteratorSpliterator.estimateSize(Spliterators.java:1959)
        at java.base/java.util.Spliterator.getExactSizeIfKnown(Spliterator.java:414)
        at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:508)
        at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
        at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
        at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
        at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
        at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:596)
        at java.base/java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:276)
        at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
        at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197)
        at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197)
        at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1708)
        at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509)
        at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
        at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
        at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
        at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
        at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:596)
        at java.base/java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:276)
        at org.apache.tinkerpop.gremlin.process.traversal.Traversal.forEachRemaining(Traversal.java:278)
        at java.base/java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1939)
        at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509)
        at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
        at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921)
        at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
        at java.base/java.util.stream.ReferencePipeline.reduce(ReferencePipeline.java:667)
        at net.osgiliath.migrator.core.graph.TinkerpopModelGraphEdgeBuilder.createEdges(TinkerpopModelGraphEdgeBuilder.java:68)

Any idea of why this thing is happening? Any potential fix?

Thank you in advance