NebulaGraph中FIND PATH语句变量自定义及报错语法修正咨询

错误原因 #

• LOOKUP语句默认返回包含顶点属性的结果集，直接赋值给$src/$dst后，FIND PATH无法识别集合类型变量作为起点/终点，必须提取具体的顶点ID（vid）。
• 原语句未通过YIELD指定返回vid，导致变量中没有存储可用的顶点标识，无法被FIND PATH调用。

正确语法写法 #

场景1：单顶点匹配（LOOKUP仅返回1个结果） #

直接提取vid赋值给变量后执行路径查询：

$src = LOOKUP ON table WHERE table.table_name == "da_pubdata_bline_stat_df" YIELD id(vertex) AS vid;
$dst = LOOKUP ON table WHERE table.table_name == "da_pubtb_opt_di" YIELD id(vertex) AS vid;
FIND SHORTEST PATH WITH PROP FROM $src.vid TO $dst.vid OVER * BIDIRECT;

或者使用管道语句串联执行：

LOOKUP ON table WHERE table.table_name == "da_pubdata_bline_stat_df" YIELD id(vertex) AS src_vid | 
LOOKUP ON table WHERE table.table_name == "da_pubtb_opt_di" YIELD id(vertex) AS dst_vid | 
FIND SHORTEST PATH WITH PROP FROM $-.src_vid TO $-.dst_vid OVER * BIDIRECT;

场景2：多顶点匹配（LOOKUP返回多个结果） #

使用FOREACH遍历所有匹配的顶点组合，逐一查询路径：

$src_list = LOOKUP ON table WHERE table.table_name == "da_pubdata_bline_stat_df" YIELD id(vertex) AS vid;
$dst_list = LOOKUP ON table WHERE table.table_name == "da_pubtb_opt_di" YIELD id(vertex) AS vid;
FOREACH($src IN $src_list) {
    FOREACH($dst IN $dst_list) {
        FIND SHORTEST PATH WITH PROP FROM $src.vid TO $dst.vid OVER * BIDIRECT;
    }
}

内容的提问来源于stack exchange，提问作者Lisa Liu