Path properties in Cypher

Question

I have a following graph in Neo4j

(id:5,t:e)<--(id:4,t:w)<--(id:0;t:s)-->(id:1,t:w)-->(id:2,t:b)-->(id:3,t:e)

now I search paths from nodes with t:s to nodes with t:e such that only white-listed nodes with t:w are in-between.

So ideally i need a query to return only (0)-->(4)-->(5) but not (0)-->(1)-->(2)-->(3).

EDIT: i have forgotten to mention that paths may have variable length: from 0 to potentially infinity. It means that I may have an arbitrary number of "t:w" nodes

Best regards

JohnMark13 JohnMark13 · Accepted Answer · 2014-11-05T12:53:01

Working just with the information that you have provided above you could use

MATCH p=({t:'s'})-->({t:'w'})-->({t:'e'}) RETURN p

Of course if an s could link directly to an e you will need to use variable length relationships matches.

MATCH p=({t:'s'})-[*0..1]->({t:'w'})-[]->({t:'e'})
RETURN DISTINCT p

EDIT - Paths of any length

MATCH p=({t:'s'})-[*0..1]->({t:'w'})-[*]->({t:'e'})
RETURN DISTINCT p

To match a path of any length use the * operator in the relationship path match. It is usually best to put some bounds on that match, an example of which is the *0..1 (length 0 to 1). You can leave either end open *..6 (length 1 to 6) or *2.. (length 2 to whatever).

The problem with this is that now you cannot guarantee the node types in the intervening nodes (so t:"b" will be matched). To avoid that I think you'll have to filter.

MATCH p=({t:'s'})-[*]->({t:'e'})
WHERE ALL (node IN NODES(p)
   WHERE node.t = 's' OR node.t = 'w' OR node.t = 'e' )
RETURN p

End Edit

You should introduce labels to your nodes and use relationship types for traversal though as that is where Neo/Cypher is going to be able to help you out. You should also make sure that if you are matching on properties that they are indexed correctly.

Path properties in Cypher

1 Answers