Neo4j查询性能问题

Question

I have some performance issue using a specific Cypher Command.

I look for R nodes not directly connected to a specific set of nodes of type I (Here, nodes with index field at "79" and "4") and I want to maximize the field "score" :

MATCH (r:R), (i0:I { index:"79" }), (i1:I { index:"4" })
WHERE NOT r--i0 AND NOT r--i1
RETURN r.index
ORDER BY r.score DESC
LIMIT 5

The query is executed generally in 1250ms. If I remove the ORDER BY clause, the request time goes down to 130ms. The order clause iterates on nearly 3300 elements.

Any idea how I can speed up that request ? I am sure there is a way to use another syntax to perform this search.

Answer 1

I think it is normal, by removing the ORDER BY , he will return you the 5 first nodes he can match. By adding the ORDER BY, it forces to load all possible matching nodes, depending of the amount of "R" nodes the time will increase.

Now :

Did you "profiled" your query with PROFILE

do you have indexes/constraints on I:index ?

Can you change slightly your query to :

MATCH (r:R), (i0:I { index:"79" }), (i1:I { index:"4" })
WHERE NOT EXISTS((r)--(i0)) 
AND NOT EXISTS((r)--(i1))
RETURN r.index
ORDER BY r.score DESC
LIMIT 5

Answer 2

Which version do you use? try to update to the latest one, also please share your visual query plan by prefixing your query with `PROFILE``

Change it to:

MATCH (i0:I { index:"79" }), (i1:I { index:"4" })
MATCH (r:R) 
WHERE NOT r--i0 AND NOT r--i1
WITH r
ORDER BY r.score DESC
LIMIT 5
RETURN r.index