【NebulaGraph】官方查询语言nGQL教程1
- 1. 课程信息
- 2. 查找路径`FIND PATH`
- 2.1 补充说明`FIND PATH`
- 2.2 例子
1. 课程信息
课程地址: https://www.bilibili.com/video/BV1PT411P7w8/?spm_id_from=333.337.search-card.all.click&vd_source=240d9002f7c7e3da63cd9a975639409a
2. 查找路径FIND PATH
FIND PATH语句查找指定起始点和目的点之间的路径。
语法:
FIND { SHORTEST | SINGLE SHORTEST | ALL | NOLOOP } PATH [WITH PROP] FROM <vertex_id_list> TO <vertex_id_list>
OVER <edge_type_list> [REVERSELY | BIDIRECT]
[<WHERE clause>] [UPTO <N> {STEP|STEPS}]
YIELD path as <alias>
[| ORDER BY $-.path] [| LIMIT <M>];
<vertex_id_list> ::=
[vertex_id [, vertex_id] ...]
- SHORTEST：查找所有最短路径。
- SINGLE SHORTEST：查找所有最短路径，随机返回其中一条。
- ALL：查找所有路径。
- NOLOOP：查找非循环路径。
- WITH PROP：展示点和边的属性。不添加本参数则隐藏属性。
-
<vertex_id_list>：点 ID 列表。多个点用英文逗号（,）分隔。支持 − 和 -和 −和var。 -
<edge_type_list>：Edge type 列表。多个 Edge type 用英文逗号（,）分隔。*表示所有 Edge type。 - REVERSELY | BIDIRECT：REVERSELY表示反向，BIDIRECT表示双向。
-
<WHERE clause>：可以使用WHERE子句过滤边属性。 -
UPTO <N> {STEP|STEPS}：路径的最大跳数。默认值为5。 -
ORDER BY $-.path：将返回结果进行排序。排序规则参见 Path。 -
LIMIT <M>：指定返回的最大行数。
限制
- 指定起始点和目的点的列表后，会返回起始点和目的点所有组合的路径。
- 搜索所有路径时可能会出现循环。
- 使用WHERE子句时只能过滤边属性，暂不支持过滤点属性，且不支持函数。
- graphd 是单进程查询，会占用很多内存。
示例
返回的路径格式类似于
(<vertex_id>)-[:<edge_type_name>@<rank>]->(<vertex_id)
# 查找并返回 player102 到 team204 的最短路径。
nebula> FIND SHORTEST PATH FROM "player102" TO "team204" OVER * YIELD path AS p;
+--------------------------------------------+
| p |
+--------------------------------------------+
| <("player102")-[:serve@0 {}]->("team204")> |
+--------------------------------------------+
# 查找并返回带属性值的 team204 到 player100 的最短反向路径。
nebula> FIND SHORTEST PATH WITH PROP FROM "team204" TO "player100" OVER * REVERSELY YIELD path AS p;
+--------------------------------------------------------------------------------------------------------------------------------------+
| p |
+--------------------------------------------------------------------------------------------------------------------------------------+
| <("team204" :team{name: "Spurs"})<-[:serve@0 {end_year: 2016, start_year: 1997}]-("player100" :player{age: 42, name: "Tim Duncan"})> |
+--------------------------------------------------------------------------------------------------------------------------------------+
# 查找并返回起点为 player100,player130 而终点为 player132,player133 的 18 跳之内双向最短路径。
nebula> FIND SHORTEST PATH FROM "player100", "player130" TO "player132", "player133" OVER * BIDIRECT UPTO 18 STEPS YIELD path as p;
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| p |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| <("player100")<-[:follow@0 {}]-("player144")<-[:follow@0 {}]-("player133")> |
| <("player100")-[:serve@0 {}]->("team204")<-[:serve@0 {}]-("player138")-[:serve@0 {}]->("team225")<-[:serve@0 {}]-("player132")> |
| <("player130")-[:serve@0 {}]->("team219")<-[:serve@0 {}]-("player112")-[:serve@0 {}]->("team204")<-[:serve@0 {}]-("player114")<-[:follow@0 {}]-("player133")> |
| <("player130")-[:serve@0 {}]->("team219")<-[:serve@0 {}]-("player109")-[:serve@0 {}]->("team204")<-[:serve@0 {}]-("player114")<-[:follow@0 {}]-("player133")> |
| <("player130")-[:serve@0 {}]->("team219")<-[:serve@0 {}]-("player104")-[:serve@20182019 {}]->("team204")<-[:serve@0 {}]-("player114")<-[:follow@0 {}]-("player133")> |
| ... |
| <("player130")-[:serve@0 {}]->("team219")<-[:serve@0 {}]-("player112")-[:serve@0 {}]->("team204")<-[:serve@0 {}]-("player138")-[:serve@0 {}]->("team225")<-[:serve@0 {}]-("player132")> |
| <("player130")-[:serve@0 {}]->("team219")<-[:serve@0 {}]-("player109")-[:serve@0 {}]->("team204")<-[:serve@0 {}]-("player138")-[:serve@0 {}]->("team225")<-[:serve@0 {}]-("player132")> |
| ... |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
# 查找 player100 和 player130 分别与 player132 和 player133 之间跳数最长为 18 步的最短路径。
nebula> FIND SINGLE SHORTEST PATH FROM "player100", "player130" TO "player132", "player133" OVER * BIDIRECT UPTO 18 STEPS YIELD path as p;
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| p |
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| <("player100")<-[:follow@0 {}]-("player144")<-[:follow@0 {}]-("player133")> |
| <("player100")-[:serve@0 {}]->("team204")<-[:serve@0 {}]-("player138")-[:serve@0 {}]->("team225")<-[:serve@0 {}]-("player132")