动态 Neo4j Cypher 查询

Question

有没有办法编写下面的 neo4j cypher 脚本来根据正在读取的数组的大小来处理 n 案例？ 我有不同的数组大小来计算二氧化碳消耗量，因此使用一种适合所有情况的大小会非常低效。

MATCH paths = allShortestPaths((a: Flights {label: 'Paris'})-[: FLIGHT*]->(b:Flights {label: 'Sydney'}))
WITH paths, relationships(paths) AS rels
UNWIND rels AS rel
WITH paths, 
 collect(rel.co2) AS co2, 
 collect(rel.engine_consumption) as ec
RETURN 
  reduce(acc1=0.0,
      x IN range(0, size(fc)-1) |
            case when x=0 then acc1 + co2[x]
                  when x=1 then acc1 + co2[x] * ec[x-1]
                  when x=2 then acc1 + co2[x] * ec[x-1] * ec[x-2]
                  when x=3 then acc1 + co2[x] * ec[x-1] * ec[x-2] * ec[x-3] 
                  ...
                  when x=size(ec)-1 then acc1 + co2[x] * ec[x-1] * ... * ec[0] 
                  end
      )  AS normalised_co2
;

Answer 1

我最终使用 python 库 py2neo 完成了此操作，并使用 python 创建了 cypher 查询

case_when = ''
accumulator = ''
for x in range(max_paths):
    accumulator += f'* co2[{x}]'
    case_when += f'when x={x+1} then acc + co2[{x+1}]' + accumulator + ' \n '