CODEWITHSUNDEEP
neo4jcypher
skme
skme

Reputation: 761

cypher query match on an optional node

I'm trying to improve an already published query : neo4j improving cypher query performace

Again, I have items graph db. each item is connected to multiple properties, which can be shared by multiple items. BUT , this time I want to search for items starting with few property nodes and finding the most connected items.

So, I have a set of properties pr=["pr1","pr2","pr3"] and I want to find the most related items

i.e. 

match (pr)-[r]-(item)
return item, count(r) as matching_properties
order by matching_properties

But, I want to find similar items too. There are SIMILAR relationships between properties, and I want to find:

MATCH (pr) -[:SIMILAR]->(pr2)-[r]-(item)

I tried retrieving all items by doing:

MATCH (pr) -[r*1..2]-(item)

The problem is that I want only the paths that got with a SIMILAR relationship through a property node, and unfortunately I have a lot of paths through some other nodes with other relationships. So I can do Something like :

MATCH (pr) -[r*1..2]-(item)
where (length(r)= 1 or ANY (x in r where (type(x)="SIMILAR")))

but that's really not efficient because it's only a small portion of the paths. I really would want to do an optional matching similar to this :

MATCH (pr) -[r2?:SIMILAR]->(pr2?)-[r]-(item)
where pr2.type = "property"

Or, using an "OR" operand between the two path options (which I know that it doesn't exist..)

Is there any way to do that? Currently I'm using neo4j 1.9.2 but I am planning to move to 2.0. So an answer for 2.0 would be good for me too.

Upvotes: 2

Views: 1362

Answers (1)

Michael Hunger
Michael Hunger

Reputation: 41676

Something like this?

Paths starting at 0 (*0..) also include the zero length path to the start-node.

MATCH (pr:property)-[:SIMILAR*0..1]->(pr2:property)<-[:HAS_PROPERTY]-(item:item)
RETURN pr2, item

Upvotes: 4

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