MATCH (u:User {uid: $userId})
UNWIND $contextNames as contextName
MERGE (context:Context {name:contextName.name,by:u.uid,uid:contextName.uid})
ON CREATE SET context.timestamp=$timestamp
MERGE (context)-[by:BY]->(u)
SET by.timestamp = $timestamp

{
 "userId": "15229100-b20e-11e3-80d3-6150cb20a1b9",
 "contextNames": [
  {
    "uid": "822e2580-1f5e-11e9-9ed0-5b93e8900a78",
    "name": "fnas"
  }
 ],
 "timestamp": "1912811921129"
}

MATCH (u:User {uid: $userId})
 UNWIND $contextNames as contextName
 MERGE (context:Context {name:contextName.name,by:u.uid,uid:contextName.uid})
 ON CREATE SET context.timestamp=$timestamp
 MERGE (context)-[:BY{timestamp:$timestamp}]->(u)