OrientDB: Create Edges with subselect - orientdb

Question

I have a simple tree structure in a MySQL table (id, parentId) with about 3 million vertices and wanted to import this into a OrientDB Graph database. The ETL importer imports the vertices smoothly, but can't create edges (NullPointerException). The ETL does not even work on a plain database with the given examples in the documentation (http://orientdb.com/docs/last/Import-a-tree-structure.html throws the same exception), so I just imported the vertices and wanted to create the edges manually.
I have a Vertex class (Address) with two properties (id, parentId) and I want to create the Edges between these Vertices (parentId -> id). Is there a simple way to do this instead of inserting the edges in a loop? Something like in SQL
INSERT INTO E (out, in) VALUES (SELECT parentId, id FROM Address)
Since edges shall only be created with CREATE EDGE, I guess OrientDB does not support such an operation by default. But maybe there is a workaround to create these 3 million edges?
I found it is easy to create a link between the two records:
CREATE LINK parentLink TYPE LINK FROM Address.parentId TO Address.Id
However, I cannot create Edges in such a way. I tried working with variables
CREATE EDGE isParentOf FROM (SELECT FROM Address) TO (SELECT FROM Address WHERE id = $current.parentId)
But that does not work.

Answer 1

Have you tried this ETL Json:
{
"config": {"log": "debug", "parallel": true },
"extractor" : {
"jdbc": { "driver": "oracle.jdbc.driver.OracleDriver",
"url": "jdbc:oracle:thin:hostname/db",
"userName": "username",
"userPassword": "password",
"query": "select id, A.parentId from Address a where rownum<2" }
},
"transformers": [`enter code here`
{ "vertex": { "class": "Address" }},
{ "edge": { "class": "isParentOf",
"joinFieldName": "parentId",
"lookup": "Address.Id",
"direction": "in",
"skipDuplicates":true
}
}
],
"loader": {
"orientdb": {
"dbURL": "remote:server/db",
"dbUser": "user",
"dbPassword": "passwd!",
"dbType": "graph",
"classes": [
{"name": "Address", "extends": "V"},
{"name": "isParentOf", "extends": "E"}
], "indexes": [
{"class":"Address", "fields":["ID:string"], "type":"UNIQUE" }
]
}
}
}