GET SUBGRAPHGraph

GET SUBGRAPH语句检索指定Edge type的起始点可以到达的点和边的信息，返回子图信息。

语法Graph

GET SUBGRAPH [WITH PROP] [<step_count> STEPS] FROM {<vid>, <vid>...}
[IN <edge_type>, <edge_type>...]
[OUT <edge_type>, <edge_type>...]
[BOTH <edge_type>, <edge_type>...];

• WITH PROP：展示属性。不添加本参数则隐藏属性。

• step_count：指定从起始点开始的跳数，返回从0到step_count跳的子图。必须是非负整数。默认值为1。

• vid：指定起始点ID。

• edge_type：指定Edge type。可以用IN、OUT和BOTH来指定起始点上该Edge type的方向。默认为BOTH。

示例Graph

以下面的示例图进行演示。

• 查询从点player100开始、0~1跳、所有Edge type的子图。

  nebula> GET SUBGRAPH 1 STEPS FROM "player100";
  +-------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------+
  | _vertices                                                               | _edges                                                                                                                      |
  +-------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------+
  | [("player100" :player{})]                                               | [[:serve "player100"->"team200" @0 {}], [:follow "player100"->"player101" @0 {}], [:follow "player100"->"player102" @0 {}]] |
  +-------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------+
  | [("team200" :team{}), ("player101" :player{}), ("player102" :player{})] | [[:follow "player102"->"player101" @0 {}]]                                                                                  |
  +-------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------+
  

  返回的子图如下。

  

• 查询从点player100开始、0~1跳、follow类型的入边的子图。

  nebula> GET SUBGRAPH 1 STEPS FROM "player100" IN follow;
  +---------------------------+--------+
  | _vertices                 | _edges |
  +---------------------------+--------+
  | [("player100" :player{})] | []     |     
  +---------------------------+--------+
  | []                        | []     |
  +---------------------------+--------+
  

  因为player100没有follow类型的入边。所以仅返回点player100。

• 查询从点player100开始、0~1跳、serve类型的出边的子图，同时展示边的属性。

  nebula> GET SUBGRAPH WITH PROP 1 STEPS FROM "player100" OUT serve;
  +------------------------------------------------------+-------------------------------------------------------------------------+
  | _vertices                                            | _edges                                                                  |
  +------------------------------------------------------+-------------------------------------------------------------------------+
  | [("player100" :player{age: 42, name: "Tim Duncan"})] | [[:serve "player100"->"team200" @0 {end_year: 2016, start_year: 1997}]] |
  +------------------------------------------------------+-------------------------------------------------------------------------+
  | [("team200" :team{name: "Warriors"})]                | []                                                                      |
  +------------------------------------------------------+-------------------------------------------------------------------------+
  

  返回的子图如下。

  

FAQGraph

为什么返回结果中会出现超出step_count跳数之外的关系？Graph

为了展示子图的完整性，会在满足条件的所有点上额外查询一跳。例如下图。

• 用GET SUBGRAPH 1 STEPS FROM "A";查询的满足结果的路径是A->B、B->A和A->C，为了子图的完整性，会在满足结果的点上额外查询一跳，即B->C。

• 用GET SUBGRAPH 1 STEPS FROM "A" IN follow;查询的满足结果的路径是B->A，在满足结果的点上额外查询一跳，即A->B。

如果只是查询满足条件的路径或点，建议使用Graph语句。例如：

nebula> match p= (v:player) -- (v2) where id(v)=="A" return p;

nebula> go 1 steps from "A" over follow;

为什么返回结果中会出现低于step_count跳数的关系？Graph

查询到没有多余子图数据时会停止查询，且不会返回空值。

nebula> GET SUBGRAPH 100 STEPS FROM "player141" OUT follow;
+-------------------------------------------------------+--------------------------------------------+
| _vertices                                             | _edges                                     |
+-------------------------------------------------------+--------------------------------------------+
| [("player141" :player{age: 43, name: "Ray Allen"})]   | [[:follow "player141"->"player124" @0 {}]] |
+-------------------------------------------------------+--------------------------------------------+
| [("player124" :player{age: 33, name: "Rajon Rondo"})] | [[:follow "player124"->"player141" @0 {}]] |
+-------------------------------------------------------+--------------------------------------------+