AGE中访问路径内边属性时报错，请求技术解决方案

我在使用Apache AGE进行图查询时，以下代码可正常执行：

SELECT * FROM cypher('age_graph', $$ 
    MATCH (a)-[:LocatedAt*]->(c:City)
    MATCH (a:Airport)-[e:Flight*]->(b:Airport) 
    MATCH (b)-[:LocatedAt*]->(c1:City) 
        RETURN c, a, e, b, c1
$$) AS (c agtype, airport1 agtype,e agtype , airport2 agtype, c1 agtype);

但尝试返回路径内边的属性时，执行以下代码出现错误：

SELECT * FROM cypher('age_graph', $$ 
    MATCH (a)-[:LocatedAt*]->(c:City)
    MATCH (a:Airport)-[e:Flight*]->(b:Airport) 
    MATCH (b)-[:LocatedAt*]->(c1:City) 
        RETURN c, a, e, b, c1, e.arrival_time
$$) AS (c agtype, airport1 agtype,e agtype , airport2 agtype, c1 agtype, arrival agtype);

错误信息：

ERROR: array index must resolve to an integer value

错误原因与解决方法 #

错误核心在于[e:Flight*]中的e是边的数组（*表示匹配0或多条边），而非单条边。直接通过e.arrival_time访问属性会被解析为数组索引操作，因此触发报错。根据业务需求，可选择以下两种解决方案：

• 仅匹配单条Flight边
  如果业务逻辑只需要单个Flight边的属性，去掉*即可，此时e是单条边，可直接访问属性：

SELECT * FROM cypher('age_graph', $$ 
    MATCH (a)-[:LocatedAt*]->(c:City)
    MATCH (a:Airport)-[e:Flight]->(b:Airport) 
    MATCH (b)-[:LocatedAt*]->(c1:City) 
        RETURN c, a, e, b, c1, e.arrival_time
$$) AS (c agtype, airport1 agtype,e agtype , airport2 agtype, c1 agtype, arrival agtype);

• 处理多条Flight边的情况
  若需要匹配多条边并提取每条边的属性，使用UNWIND将边数组展开后再访问：

SELECT * FROM cypher('age_graph', $$ 
    MATCH (a)-[:LocatedAt*]->(c:City)
    MATCH (a:Airport)-[e:Flight*]->(b:Airport) 
    MATCH (b)-[:LocatedAt*]->(c1:City)
    UNWIND e AS flight_edge
        RETURN c, a, e, b, c1, flight_edge.arrival_time
$$) AS (c agtype, airport1 agtype,e agtype , airport2 agtype, c1 agtype, arrival agtype);

如果需要将所有边的属性收集为列表，可使用列表推导式：

SELECT * FROM cypher('age_graph', $$ 
    MATCH (a)-[:LocatedAt*]->(c:City)
    MATCH (a:Airport)-[e:Flight*]->(b:Airport) 
    MATCH (b)-[:LocatedAt*]->(c1:City) 
        RETURN c, a, e, b, c1, [edge IN e | edge.arrival_time] AS arrival_times
$$) AS (c agtype, airport1 agtype,e agtype , airport2 agtype, c1 agtype, arrival_times agtype);

内容的提问来源于stack exchange，提问作者Jaber