Apoc periodic iterate succeeds but does not return anything

Neo4j Graph Platform
1

I expect some outright error on my part but request any help. Using apoc.periodic.iterate s per:
call apoc.periodic.iterate("
MATCH (a:DrugDrugX), (b:MeshDB)
WHERE a.parentKey = b.parentKey
RETURN a,b
",
"MERGE (a) - [r:DRUG_DRUG_MESH] -> (b)
RETURN r",
{batchSize:20000,
parallel:false});
Reports 1195 batches, "relationshipsCreated": 23893270, takes about 230 seconds with 4G set aside for Neo4j.
But rel DRUG_DRUG_MESH is nowhere to be seen!
Using desktop 1.4.15 I can use the python connector but have not done so for this. I don't do java.
Project exploring NLM MeSH codes and drug interactions.
Your help greatly appreciated.

2

Aha! Got it to work. Yes, something dumb. Oh well. Anybody interested in NLM MeSH codes?