CODEWITHSUNDEEP
pythonneo4jpy2neo
VineetChirania
VineetChirania

Reputation: 871

Exception in creating batch relationship between nodes while using py2neo

I have created a graph database using py2neo and the purpose is:

I created city nodes first (successfully) using this module:

batch = neo4j.WriteBatch(graph_db)    
for city_id,city_name in <some_list>:
     city_node_id = batch.create(node(city_id=city_id, name=city_name))
     batch.add_indexed_node('city_index','city_id',city_id, city_node_id)
batch.submit()

Then in another separate module I tried to create airport nodes and relationship between the airport node and corresponding city node like this:

read_batch = neo4j.ReadBatch(graph_db)
write_batch = neo4j.WriteBatch(graph_db)
for airport_id, city_id, airport_name in <some_list>:
    airport_node_id = write_batch.create(node(airport_id=airport_id, city_id=city_id, name=airport_name)) 
    write_batch.add_indexed_node('airport_index','airport_id',airport_id, airport_node_id)
    city_node_id = read_batch.get_indexed_nodes('city_index','city_id',city_id)
    rel_id = write_batch.create(rel(airport_node_id, "is in city", city_node_id))
    write_batch.add_indexed_relationship('airport_rel_index','airport_id',airport_id, rel_id)
write_batch.submit()

The 3rd statement from last wherein I am creating relationships is throwing exception:

rel_id = write_batch.create(rel(airport_node_id, "is in city", city_node_id))
File "/usr/local/lib/python2.7/dist-packages/py2neo/neo4j.py", line 2695, in create
"to": self._uri_for(entity.end_node)
File "/usr/local/lib/python2.7/dist-packages/py2neo/neo4j.py", line 2537, in _uri_for
uri = "{{{0}}}".format(self.find(resource))
File "/usr/local/lib/python2.7/dist-packages/py2neo/neo4j.py", line 2528, in find
raise ValueError("Request not found")
  ValueError: Request not found

I tried to print uri of both the types of nodes. Their is a difference:

print station_node_id._uri, city_node_id._uri

Output:

node index/node/city_index/city_id/2536650

So the uris of both nodes are different, which is why I guess the relationship is not getting created.

What function can I use which returns the unindexed node for city i.e. uri should be just "node" instead of the "index/node/city_index/city_id/".

Is there any other way to create this relationship?

I would be happy to provide any other information if need be. Thanks in advance!

Neo4j: 1.9.5

py2neo: 1.6.1

Upvotes: 1

Views: 325

Answers (1)

Nigel Small
Nigel Small

Reputation: 4495

What you're seeing is an unfortunate server limitation whereby the Location URIs returned by some REST calls contain a node index entry URI instead of a standard node URI. This is unfortunately useful only in a few use cases and a major limitation in cases like yours.

There is a similar issue discussed here - https://github.com/nigelsmall/py2neo/issues/221 - and unfortunately nothing I can do from the client side.

Your only real option is to split your work into multiple batches or - if you are able to do so - consider an upgrade to Neo4j 2.0 where you can use the new label and schema index capabilities.

Upvotes: 1

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