LIMIT有多少影响neo4j“ allShortestPaths”密码查询性能

Question

I have learned that how much higher will your LIMIT be, how much higher DbHits will be done during the Execution Plan,and neo4j is using A* algorithm for "allShortestPaths" query.

My first question is dose LIMIT also affect neo4j "allShortestPaths" query.If it does affect, how much it affects, why it affect?

I have do some test.but i haven't found the obvious evidence that the LIMIT affect performance as we expect

[EDITED]

My test query:

MATCH
  (node1:E { eid:"c953fc2d-55fc-4239-910e-ae6e41b3648d" }),
  (node2:E { eid:"e8cdf5e0-97ad-4e1e-a8e4-29358f8a9866" }),
  p = allShortestPaths((node1)-[*]-(node2))
RETURN p
LIMIT 25;

Answer 1

The LIMIT in you test query does not limit the amount of work done by allShortestPaths ; instead, it just limits the number of results you get back.

The only way to affect the amount of work done by allShortestPaths is by putting an upper bound on the length of the paths searched. For example, this query will only search paths with up to 5 relationships:

MATCH
  (node1:E { eid:"c953fc2d-55fc-4239-910e-ae6e41b3648d" }),
  (node2:E { eid:"e8cdf5e0-97ad-4e1e-a8e4-29358f8a9866" }),
  p = allShortestPaths((node1)-[*..5]-(node2))
RETURN p
LIMIT 25;

By the way, to speed up the matching of the end nodes you should create an index on :E(eid) .