问题
I am trying to use Neo4j to write a query that aggregates quantities along a particular sub-graph.
We have two stores Store1 and Store2 one with supplier S1 the other with supplier S2. We move 100 units from Store1 into Store3 and 200 units from Store2 to Store3.
We then move 100 units from Store3 to Store4. So now Store4 has 100 units and approximately 33 originated from supplier S1 and 66 from supplier S2.
I need the query to effectively return this information, E.g.
S1, 33
S2, 66
I have a recursive query to aggregate all the movements along each path
MATCH p=(store1:Store)-[m:MOVE_TO*]->(store2:Store { Name: 'Store4'})
RETURN store1.Supplier, reduce(amount = 0, n IN relationships(p) | amount + n.Quantity) AS reduction
Returns:
| store1.Supplier | reduction|
|-------------------- |-------------|
| S1 | 200 |
| S2 | 300 |
| null | 100 |
Desired:
| store1.Supplier | reduction|
|---------------------|-------------|
| S1 | 33.33 |
| S2 | 66.67 |
回答1:
What about this one :
MATCH (s:Store) WHERE s.name = 'Store4'
MATCH (s)<-[t:MOVE_TO]-()<-[r:MOVE_TO]-(supp)
WITH t.qty as total, collect(r) as movements
WITH total, movements, reduce(totalSupplier = 0, r IN movements | totalSupplier + r.qty) as supCount
UNWIND movements as movement
RETURN startNode(movement).name as supplier, round(100.0*movement.qty/supCount) as pct
Which returns :
supplier pct
Store1 33
Store2 67
Returned 2 rows in 151 ms
回答2:
So the following is pretty ugly, but it works for the example you've given.
MATCH (s4:Store { Name:'Store4' })<-[r1:MOVE_TO]-(s3:Store)<-[r2:MOVE_TO*]-(s:Store)
WITH s3, r1.Quantity as Factor, SUM(REDUCE(amount = 0, r IN r2 | amount + r.Quantity)) AS Total
MATCH (s3)<-[r1:MOVE_TO*]-(s:Store)
WITH s.Supplier as Supplier, REDUCE(amount = 0, r IN r1 | amount + r.Quantity) AS Quantity, Factor, Total
RETURN Supplier, Quantity, Total, toFloat(Quantity) / toFloat(Total) * Factor as Proportion
I'm sure it can be improved.
来源：https://stackoverflow.com/questions/28036055/recursive-query-with-sub-graph-aggregation