Python basic index search

gistfile1.py

from neo4j import GraphDatabase
 
# Create db
db = GraphDatabase('db')

with db.transaction:
 	noun_id = 1
    	#-----1-----------------
    	#first creating the index, reference node and storing it...
	noun_index = db.node.indexes.create('noun_idx')  
	noun_ref  = db.node()
	noun_index['type']['noun_ref'] = noun_ref

	#------2------------------
	#then later I use the reference node to add some new nodes and make sure they are "connected to" the ref-node
	noun = db.node(id=noun_id)
	noun.INSTANCE_OF(noun_ref)




#------3-------------------
#however the next time I run the code and want to actually grab the reference
#node from the index like this....
noun_index = db.index().forNodes('noun_idx')
noun_ref = noun_index['type']['noun_ref'].single

#and then traverse the nouns connected to the reference node (code below in step #4)
#-----4-------------
for relationship in noun_ref.INSTANCE_OF:
       noun = relationship.start
       print noun
 
# Always shut down your database
db.shutdown()

Just as an aside, there's a helper method in py2neo called get_or_create_indexed_node which can help reduce the amount of code required in this type of case:

from py2neo import neo4j

db = neo4j.GraphDatabaseService()

noun_id = 1
noun = db.get_node(noun_id)
# can create a new node attached to the index if one doesn't already exist
noun_ref = db.get_or_create_indexed_node("noun_idx", "type", "noun_ref")
# make the relationship
db.create((noun, "INSTANCE_OF", noun_ref))

for relationship in noun_ref.get_relationships(neo4j.Direction.BOTH, "INSTANCE_OF"):
    noun = relationship.start_node
    print noun

http://packages.python.org/py2neo/neo4j.html#py2neo.neo4j.GraphDatabaseService.get_or_create_indexed_node

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