CALL apoc.periodic.iterate(
"LOAD CSV WITH HEADERS FROM url AS line 
WITH  apoc.coll.partition(collect(line),10000) AS batchesOfLines 
UNWIND batchesOfLines as batch 
RETURN batch",
"UNWIND {batch} AS user 
MERGE (u:User {Email: user.Email}) 
SET u += apoc.map.clean(user,['Email'],null)",
{batchSize: 1, parallel: true})