Nebula入门学习——day4 nGQL中的图查询和其他算法

MATCH¶

MATCH语句提供基于模式（pattern）匹配的搜索功能。

一个MATCH语句定义了一个搜索模式，用该模式匹配存储在 Nebula Graph 中的数据，然后用RETURN子句检索数据。

本文示例使用测试数据集 basketballplayer 进行演示。

我自己最喜欢用的是：

(root@nebula) [basketballplayer]> MATCH (v) RETURN v LIMIT 10
+-----------------------------------------------------------+
| v                                                         |
+-----------------------------------------------------------+
| ("player102" :player{age: 33, name: "LaMarcus Aldridge"}) |
| ("player106" :player{age: 25, name: "Kyle Anderson"})     |
| ("player115" :player{age: 40, name: "Kobe Bryant"})       |
| ("player129" :player{age: 37, name: "Dwyane Wade"})       |
| ("player138" :player{age: 38, name: "Paul Gasol"})        |
| ("team209" :team{name: "Timberwolves"})                   |
| ("team225" :team{name: "Bucks"})                          |
| ("team226" :team{name: "Magic"})                          |
| ("player108" :player{age: 36, name: "Boris Diaw"})        |
| ("player122" :player{age: 30, name: "DeAndre Jordan"})    |
+---------------------------------------

语法¶

与GO或LOOKUP等其他查询语句相比，MATCH的语法更灵活。MATCH语句采用的路径类型是trail，即遍历时只有点可以重复，边不可以重复。

MATCH 语法如下：

MATCH <pattern> [<clause_1>]  RETURN <output>  [<clause_2>];

pattern：pattern 的详细说明请参见模式。MATCH语句支持匹配一个或多个模式，多个模式之间用英文逗号（,）分隔。例如(a)-[]->(b),(c)-[]->(d)。

clause_1：支持WHERE、WITH、UNWIND、OPTIONAL MATCH子句，也可以使用MATCH作为子句。

output：定义需要返回的输出。可以使用AS设置输出的别名。

clause_2：支持ORDER BY、LIMIT子句。

注意事项¶

除以下三种情况之外，请确保 MATCH 语句有至少一个索引可用。

MATCH语句中WHERE子句使用 id() 函数指定了点的 VID，不需要创建索引即可执行。

当遍历所有点边时，例如MATCH (v) RETURN v LIMIT N，不需要创建索引，但必须使用LIMIT限制输出结果数量。

当遍历指定 Tag 的点或指定 Edge Type 的边时，例如MATCH (v:player) RETURN v LIMIT N，不需要创建索引，但必须使用LIMIT限制输出结果数量。

Note

目前 match 语句无法查询到悬挂边。

历史版本兼容性

从 3.0.0 版本开始，为了区别不同 Tag 的属性，返回属性时必须额外指定 Tag 名称。即从RETURN <变量名>.<属性名>改为RETURN <变量名>.<Tag名>.<属性名>。

示例¶

创建索引¶

# 在 Tag player 的 name 属性和 Edge type follow 上创建索引。
nebula> CREATE TAG INDEX IF NOT EXISTS name ON player(name(20));
nebula> CREATE EDGE INDEX IF NOT EXISTS follow_index on follow();

# 重建索引使其生效。
nebula> REBUILD TAG INDEX name;
+------------+
| New Job Id |
+------------+
| 121        |
+------------+

nebula> REBUILD EDGE INDEX follow_index;
+------------+
| New Job Id |
+------------+
| 122        |
+------------+

# 确认重建索引成功。
nebula> SHOW JOB 121;
+----------------+---------------------+------------+----------------------------+----------------------------+-------------+
| Job Id(TaskId) | Command(Dest)       | Status     | Start Time                 | Stop Time                  | Error Code  |
+----------------+---------------------+------------+----------------------------+----------------------------+-------------+
| 121            | "REBUILD_TAG_INDEX" | "FINISHED" | 2021-05-27T02:18:02.000000 | 2021-05-27T02:18:02.000000 | "SUCCEEDED" |
| 0              | "storaged1"         | "FINISHED" | 2021-05-27T02:18:02.000000 | 2021-05-27T02:18:02.000000 | "SUCCEEDED" |
| 1              | "storaged0"         | "FINISHED" | 2021-05-27T02:18:02.000000 | 2021-05-27T02:18:02.000000 | "SUCCEEDED" |
| 2              | "storaged2"         | "FINISHED" | 2021-05-27T02:18:02.000000 | 2021-05-27T02:18:02.000000 | "SUCCEEDED" |
+----------------+---------------------+------------+----------------------------+----------------------------+-------------+

nebula> SHOW JOB 122;
+----------------+----------------------+------------+----------------------------+----------------------------+-------------+
| Job Id(TaskId) | Command(Dest)        | Status     | Start Time                 | Stop Time                  | Error Code  |
+----------------+----------------------+------------+----------------------------+----------------------------+-------------+
| 122            | "REBUILD_EDGE_INDEX" | "FINISHED" | 2021-05-27T02:18:11.000000 | 2021-05-27T02:18:11.000000 | "SUCCEEDED" |
| 0              | "storaged1"          | "FINISHED" | 2021-05-27T02:18:11.000000 | 2021-05-27T02:18:21.000000 | "SUCCEEDED" |
| 1              | "storaged0"          | "FINISHED" | 2021-05-27T02:18:11.000000 | 2021-05-27T02:18:21.000000 | "SUCCEEDED" |
| 2              | "storaged2"          | "FINISHED" | 2021-05-27T02:18:11.000000 | 2021-05-27T02:18:21.000000 | "SUCCEEDED" |
+----------------+----------------------+------------+----------------------------+----------------------------+-------------+
==》什么鬼。。。job清单如何查看？？？

匹配点¶

历史版本兼容性

从 Nebula Graph 3.0.0 开始，支持MATCH (v) RETURN v LIMIT n，不需要创建索引; 但是必须使用 LIMIT 限制输出结果数量。

不可以直接执行 MATCH (v) RETURN v。

用户可以在一对括号中使用自定义变量来表示模式中的点。例如(v)。

nebula> MATCH (v) \
        RETURN v \
        LIMIT 3;
+-----------------------------------------------------------+
| v                                                         |
+-----------------------------------------------------------+
| ("player102" :player{age: 33, name: "LaMarcus Aldridge"}) |
| ("player106" :player{age: 25, name: "Kyle Anderson"})     |
| ("player115" :player{age: 40, name: "Kobe Bryant"})       |
+-----------------------------------------------------------+

如果不指定tag则有返回同时有team和player：

(root@nebula) [basketballplayer]> MATCH (v) RETURN v LIMIT 100
+---------------------------------------------------------------+
| v                                                             |
+---------------------------------------------------------------+
| ("player114" :player{age: 39, name: "Tracy McGrady"})         |
| ("player150" :player{age: 20, name: "Luka Doncic"})           |
| ("team204" :team{name: "Spurs"})                              |
| ("team218" :team{name: "Raptors"})                            |
| ("team229" :team{name: "Heat"})                               |
| ("player105" :player{age: 31, name: "Danny Green"})           |
| ("player109" :player{age: 34, name: "Tiago Splitter"})        |
| ("player111" :player{age: 38, name: "David West"})            |
| ("player118" :player{age: 30, name: "Russell Westbrook"})     |

匹配 Tag¶

历史版本兼容性

在 Nebula Graph 3.0.0 之前，匹配 Tag 的前提是 Tag 本身有索引或者 Tag 的某个属性有索引，否则，用户无法基于该 Tag 执行 MATCH 语句。从 Nebula Graph 3.0.0 开始，匹配 Tag 可以不创建索引，但需要使用 LIMIT 限制输出结果数量。

用户可以在点的右侧用:<tag_name>表示模式中的 Tag。

nebula> MATCH (v:player) \
        RETURN v \
        LIMIT 3;
+-----------------------------------------------------------+
| v                                                         |
+-----------------------------------------------------------+
| ("player102" :player{age: 33, name: "LaMarcus Aldridge"}) |
| ("player106" :player{age: 25, name: "Kyle Anderson"})     |
| ("player115" :player{age: 40, name: "Kobe Bryant"})       |
+-----------------------------------------------------------+
...

需要匹配拥有多个 Tag 的点，可以用英文冒号（:）。

nebula> CREATE TAG actor (name string, age int);
nebula> INSERT VERTEX actor(name, age) VALUES "player100":("Tim Duncan", 42);
nebula> MATCH (v:player:actor) \
        RETURN v \
        LIMIT 10;
+----------------------------------------------------------------------------------------+
| v                                                                                      |
+----------------------------------------------------------------------------------------+
| ("player100" :actor{age: 42, name: "Tim Duncan"} :player{age: 42, name: "Tim Duncan"}) |
+----------------------------------------------------------------------------------------+

匹配点的属性¶

Note

匹配点的属性的前提是 Tag 本身有对应属性的索引，否则，用户无法执行 MATCH 语句匹配该属性。

用户可以在 Tag 的右侧用{<prop_name>: <prop_value>}表示模式中点的属性。

# 使用属性 name 搜索匹配的点。
nebula> MATCH (v:player{name:"Tim Duncan"}) \
        RETURN v;
+----------------------------------------------------+
| v                                                  |
+----------------------------------------------------+
| ("player100" :player{age: 42, name: "Tim Duncan"}) |
+----------------------------------------------------+

使用WHERE子句也可以实现相同的操作：

nebula> MATCH (v:player) \
        WHERE v.player.name == "Tim Duncan" \
        RETURN v;
+----------------------------------------------------+
| v                                                  |
+----------------------------------------------------+
| ("player100" :player{age: 42, name: "Tim Duncan"}) |
+----------------------------------------------------+

openCypher 兼容性

在 openCypher 9 中，=是相等运算符，在 nGQL 中，==是相等运算符，=是赋值运算符。

匹配点 ID¶

用户可以使用点 ID 去匹配点。id()函数可以检索点的 ID。

nebula> MATCH (v) \
        WHERE id(v) == 'player101' \
        RETURN v;
+-----------------------------------------------------+
| v                                                   |
+-----------------------------------------------------+
| ("player101" :player{age: 36, name: "Tony Parker"}) |
+-----------------------------------------------------+

要匹配多个点的 ID，可以用WHERE id(v) IN [vid_list]。

nebula> MATCH (v:player { name: 'Tim Duncan' })--(v2) \
        WHERE id(v2) IN ["player101", "player102"] \
        RETURN v2;
+-----------------------------------------------------------+
| v2                                                        |
+-----------------------------------------------------------+
| ("player101" :player{age: 36, name: "Tony Parker"})       |
| ("player101" :player{age: 36, name: "Tony Parker"})       |
| ("player102" :player{age: 33, name: "LaMarcus Aldridge"}) |
+-----------------------------------------------------------+

匹配连接的点¶

用户可以使用--符号表示两个方向的边，并匹配这些边连接的点。

历史版本兼容性

在 nGQL 1.x 中，--符号用于行内注释，从 nGQL 2.x 起，--符号表示出边或入边，不再用于注释。

nebula> MATCH (v:player{name:"Tim Duncan"})--(v2:player) \
        RETURN v2.player.name AS Name;
+---------------------+
| Name                |
+---------------------+
| "Manu Ginobili"     |
| "Manu Ginobili"     |
| "Dejounte Murray"   |
...

用户可以在--符号上增加<或>符号指定边的方向。

# -->表示边从 v 开始，指向 v2。对于点 v 来说是出边，对于点 v2 来说是入边。
nebula> MATCH (v:player{name:"Tim Duncan"})-->(v2:player) \
        RETURN v2.player.name AS Name;
+-----------------+
| Name            |
+-----------------+
| "Tony Parker"   |
| "Manu Ginobili" |
+-----------------+

如果需要判断目标点，可以使用CASE表达式。

nebula> MATCH (v:player{name:"Tim Duncan"})--(v2) \
        RETURN \
        CASE WHEN v2.team.name IS NOT NULL \
        THEN v2.team.name  \
        WHEN v2.player.name IS NOT NULL \
        THEN v2.player.name END AS Name;

+---------------------+
| Name                |
+---------------------+
| "Manu Ginobili"     |
| "Manu Ginobili"     |
| "Spurs"             |
| "Dejounte Murray"   |
...

如果需要扩展模式，可以增加更多点和边。

nebula> MATCH (v:player{name:"Tim Duncan"})-->(v2)<--(v3) \
        RETURN v3.player.name AS Name;
+---------------------+
| Name                |
+---------------------+
| "Dejounte Murray"   |
| "LaMarcus Aldridge" |
| "Marco Belinelli"   |
...

如果不需要引用点，可以省略括号中表示点的变量。

nebula> MATCH (v:player{name:"Tim Duncan"})-->()<--(v3) \
        RETURN v3.player.name AS Name;
+---------------------+
| Name                |
+---------------------+
| "Dejounte Murray"   |
| "LaMarcus Aldridge" |
| "Marco Belinelli"   |
...

匹配路径¶

连接起来的点和边构成了路径。用户可以使用自定义变量命名路径。

nebula> MATCH p=(v:player{name:"Tim Duncan"})-->(v2) \
        RETURN p;  ==》一直没有找到，原来是要这样写！！！【【常用！！！！】】
+--------------------------------------------------------------------------------------------------------------------------------------+
| p                                                                                                                                    |
+--------------------------------------------------------------------------------------------------------------------------------------+
| <("player100" :player{age: 42, name: "Tim Duncan"})-[:serve@0 {end_year: 2016, start_year: 1997}]->("team204" :team{name: "Spurs"})> |
| <("player100" :player{age: 42, name: "Tim Duncan"})-[:follow@0 {degree: 95}]->("player101" :player{age: 36, name: "Tony Parker"})>   |
| <("player100" :player{age: 42, name: "Tim Duncan"})-[:follow@0 {degree: 95}]->("player125" :player{age: 41, name: "Manu Ginobili"})> |
+--------------------------------------------------------------------------------------------------------------------------------------+

openCypher 兼容性

在 nGQL 中，@符号表示边的 rank，在 openCypher 中，没有 rank 概念。

匹配边¶

历史版本兼容性

在 Nebula Graph 3.0.0 之前，匹配边的前提是边本身有对应属性的索引，否则，用户无法基于边执行 MATCH 语句。从 Nebula Graph 3.0.0 开始，匹配边可以不创建索引，但需要使用 LIMIT 限制输出结果数量，并且必须指定边的方向。

nebula> MATCH ()<-[e]-() \
        RETURN e \
        LIMIT 3;
+----------------------------------------------------+
| e                                                  |
+----------------------------------------------------+
| [:follow "player101"->"player102" @0 {degree: 90}] |
| [:follow "player103"->"player102" @0 {degree: 70}] |
| [:follow "player135"->"player102" @0 {degree: 80}] |
+----------------------------------------------------+

匹配 Edge type¶

和点一样，用户可以用:<edge_type>表示模式中的 Edge type，例如-[e:follow]-。

历史版本兼容性

在 Nebula Graph 3.0.0 之前，匹配 Edge Type 的前提是 Edge type 本身有对应属性的索引，否则，用户无法基于 Edge Type 执行 MATCH 语句。从 Nebula Graph 3.0.0 开始，匹配 Edge Type 可以不创建索引，但需要使用 LIMIT 限制输出结果数量，并且必须指定边的方向。

nebula> MATCH ()-[e:follow]->() \
        RETURN e \
        limit 3; ==》原来不用上面的方式，也可以返回边！！！像我下面这样，不指定edge type也是可以的！！！【【常用！！！！】】
+----------------------------------------------------+
| e                                                  |
+----------------------------------------------------+
| [:follow "player102"->"player100" @0 {degree: 75}] |
| [:follow "player102"->"player101" @0 {degree: 75}] |
| [:follow "player129"->"player116" @0 {degree: 90}] |
+----------------------------------------------------+

(root@nebula) [basketballplayer]> MATCH ()-[e:follow]->() \
                               ->         RETURN e \
                               ->         limit 3;
+----------------------------------------------------+
| e                                                  |
+----------------------------------------------------+
| [:follow "player102"->"player100" @0 {degree: 75}] |
| [:follow "player102"->"player101" @0 {degree: 75}] |
| [:follow "player129"->"player116" @0 {degree: 90}] |
+----------------------------------------------------+
Got 3 rows (time spent 1350/1667 us)

Tue, 24 May 2022 17:06:49 CST

(root@nebula) [basketballplayer]> MATCH ()-[e]->()         RETURN e         limit 3;
+-----------------------------------------------------------------------+
| e                                                                     |
+-----------------------------------------------------------------------+
| [:serve "player102"->"team203" @0 {end_year: 2015, start_year: 2006}] |
| [:serve "player102"->"team204" @0 {end_year: 2019, start_year: 2015}] |
| [:follow "player102"->"player100" @0 {degree: 75}]                    |
+-----------------------------------------------------------------------+
Got 3 rows (time spent 1314/1635 us)

Tue, 24 May 2022 17:06:56 CST

匹配边的属性¶

Note

匹配边的属性的前提是 Edge type 本身有对应属性的索引，否则，用户无法执行 MATCH 语句匹配该属性。

用户可以用{<prop_name>: <prop_value>}表示模式中 Edge type 的属性，例如[e:follow{likeness:95}]。

nebula> MATCH (v:player{name:"Tim Duncan"})-[e:follow{degree:95}]->(v2) \
        RETURN e;
+--------------------------------------------------------+
| e                                                      |
+--------------------------------------------------------+
| [:follow "player100"->"player101" @0 {degree: 95}]     |
| [:follow "player100"->"player125" @0 {degree: 95}]     |
+--------------------------------------------------------+

匹配多个 Edge type¶

使用|可以匹配多个 Edge type，例如[e:follow|:serve]。第一个 Edge type 前的英文冒号（:）不可省略，后续 Edge type 前的英文冒号可以省略，例如[e:follow|serve]。

nebula> MATCH (v:player{name:"Tim Duncan"})-[e:follow|:serve]->(v2) \
        RETURN e;
+---------------------------------------------------------------------------+
| e                                                                         |
+---------------------------------------------------------------------------+
| [:follow "player100"->"player101" @0 {degree: 95}]                        |
| [:follow "player100"->"player125" @0 {degree: 95}]                        |
| [:serve "player100"->"team204" @0 {end_year: 2016, start_year: 1997}]     |
+---------------------------------------------------------------------------+

匹配多条边¶

用户可以扩展模式，匹配路径中的多条边。

nebula> MATCH (v:player{name:"Tim Duncan"})-[]->(v2)<-[e:serve]-(v3) \
        RETURN v2, v3;
+----------------------------------+-----------------------------------------------------------+
| v2                               | v3                                                        |
+----------------------------------+-----------------------------------------------------------+
| ("team204" :team{name: "Spurs"}) | ("player104" :player{age: 32, name: "Marco Belinelli"})   |
| ("team204" :team{name: "Spurs"}) | ("player101" :player{age: 36, name: "Tony Parker"})       |
| ("team204" :team{name: "Spurs"}) | ("player102" :player{age: 33, name: "LaMarcus Aldridge"}) |
...

匹配定长路径¶

用户可以在模式中使用:<edge_type>*<hop>匹配定长路径。hop必须是一个非负整数。

nebula> MATCH p=(v:player{name:"Tim Duncan"})-[e:follow*2]->(v2) \
        RETURN DISTINCT v2 AS Friends;
+-----------------------------------------------------------+
| Friends                                                   |
+-----------------------------------------------------------+
| ("player100" :player{age: 42, name: "Tim Duncan"})        |
| ("player125" :player{age: 41, name: "Manu Ginobili"})     |
| ("player102" :player{age: 33, name: "LaMarcus Aldridge"}) |
+-----------------------------------------------------------+

我们看看边上面的匹配结果是如何发生的：

(root@nebula) [basketballplayer]> MATCH p=(v:player{name:"Tim Duncan"})-[e:follow*2]->(v2)         RETURN p;

+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| p                                                                                                                                                                                                                      |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| <("player100" :player{age: 42, name: "Tim Duncan"})-[:follow@0 {degree: 95}]->("player101" :player{age: 36, name: "Tony Parker"})-[:follow@0 {degree: 95}]->("player125" :player{age: 41, name: "Manu Ginobili"})>     |
| <("player100" :player{age: 42, name: "Tim Duncan"})-[:follow@0 {degree: 95}]->("player101" :player{age: 36, name: "Tony Parker"})-[:follow@0 {degree: 95}]->("player100" :player{age: 42, name: "Tim Duncan"})>        |
| <("player100" :player{age: 42, name: "Tim Duncan"})-[:follow@0 {degree: 95}]->("player125" :player{age: 41, name: "Manu Ginobili"})-[:follow@0 {degree: 90}]->("player100" :player{age: 42, name: "Tim Duncan"})>      |
| <("player100" :player{age: 42, name: "Tim Duncan"})-[:follow@0 {degree: 95}]->("player101" :player{age: 36, name: "Tony Parker"})-[:follow@0 {degree: 90}]->("player102" :player{age: 33, name: "LaMarcus Aldridge"})> |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

如果hop为 0，模式会匹配路径上的起始点。

nebula> MATCH (v:player{name:"Tim Duncan"}) -[*0]-> (v2) \
        RETURN v2;
+----------------------------------------------------+
| v2                                                 |
+----------------------------------------------------+
| ("player100" :player{age: 42, name: "Tim Duncan"}) |
+----------------------------------------------------+

匹配变长路径¶

用户可以在模式中使用:<edge_type>*[minHop..maxHop]匹配变长路径。

Note

设置边界时，minHop 和 maxHop 至少存在其中一个。

Caution

如果未设置 maxHop 可能会导致 graph 服务 OOM，请谨慎执行该命令。

参数	说明
`minHop`	可选项。表示路径的最小长度。`minHop`必须是一个非负整数，默认值为 1。
`maxHop`	可选项。表示路径的最大长度。`maxHop`必须是一个非负整数，默认值为无穷大。

nebula> MATCH p=(v:player{name:"Tim Duncan"})-[e:follow*]->(v2) \
        RETURN v2 AS Friends;
+-----------------------------------------------------------+
| Friends                                                   |
+-----------------------------------------------------------+
| ("player125" :player{age: 41, name: "Manu Ginobili"})     |
| ("player101" :player{age: 36, name: "Tony Parker"})       |
...

nebula> MATCH p=(v:player{name:"Tim Duncan"})-[e:follow*1..3]->(v2) \
        RETURN v2 AS Friends;
+-----------------------------------------------------------+
| Friends                                                   |
+-----------------------------------------------------------+
| ("player101" :player{age: 36, name: "Tony Parker"})       |
| ("player125" :player{age: 41, name: "Manu Ginobili"})     |
| ("player100" :player{age: 42, name: "Tim Duncan"})        |
...

nebula> MATCH p=(v:player{name:"Tim Duncan"})-[e:follow*1..]->(v2) \
        RETURN v2 AS Friends;
+-----------------------------------------------------------+
| Friends                                                   |
+-----------------------------------------------------------+
| ("player125" :player{age: 41, name: "Manu Ginobili"})     |
| ("player101" :player{age: 36, name: "Tony Parker"})       |
| ("player100" :player{age: 42, name: "Tim Duncan"})        |
...

两跳之内匹配：【如果不建索引，是没法搞的啊！！！当心！！！】

(root@nebula) [basketballplayer]> MATCH p=(v:player{name:"Tim Duncan"})-[e:follow*1..2]->(v2)         RETURN p;
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| p                                                                                                                                                                                                                      |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| <("player100" :player{age: 42, name: "Tim Duncan"})-[:follow@0 {degree: 95}]->("player125" :player{age: 41, name: "Manu Ginobili"})>                                                                                   |
| <("player100" :player{age: 42, name: "Tim Duncan"})-[:follow@0 {degree: 95}]->("player101" :player{age: 36, name: "Tony Parker"})>                                                                                     |
| <("player100" :player{age: 42, name: "Tim Duncan"})-[:follow@0 {degree: 95}]->("player101" :player{age: 36, name: "Tony Parker"})-[:follow@0 {degree: 95}]->("player125" :player{age: 41, name: "Manu Ginobili"})>     |
| <("player100" :player{age: 42, name: "Tim Duncan"})-[:follow@0 {degree: 95}]->("player101" :player{age: 36, name: "Tony Parker"})-[:follow@0 {degree: 95}]->("player100" :player{age: 42, name: "Tim Duncan"})>        |
| <("player100" :player{age: 42, name: "Tim Duncan"})-[:follow@0 {degree: 95}]->("player125" :player{age: 41, name: "Manu Ginobili"})-[:follow@0 {degree: 90}]->("player100" :player{age: 42, name: "Tim Duncan"})>      |
| <("player100" :player{age: 42, name: "Tim Duncan"})-[:follow@0 {degree: 95}]->("player101" :player{age: 36, name: "Tony Parker"})-[:follow@0 {degree: 90}]->("player102" :player{age: 33, name: "LaMarcus Aldridge"})> |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+

用户可以使用DISTINCT关键字聚合重复结果。

nebula> MATCH p=(v:player{name:"Tim Duncan"})-[e:follow*1..3]->(v2:player) \
        RETURN DISTINCT v2 AS Friends, count(v2);==》注意是两条独立语句！！！
+-----------------------------------------------------------+-----------+
| Friends                                                   | count(v2) |
+-----------------------------------------------------------+-----------+
| ("player102" :player{age: 33, name: "LaMarcus Aldridge"}) | 1         |
| ("player100" :player{age: 42, name: "Tim Duncan"})        | 4         |
| ("player101" :player{age: 36, name: "Tony Parker"})       | 3         |
| ("player125" :player{age: 41, name: "Manu Ginobili"})     | 3         |
+-----------------------------------------------------------+-----------+

如果minHop为0，模式会匹配路径上的起始点。与上个示例相比，下面的示例设置minHop为0，因为它是起始点，所以结果集中"Tim Duncan"比上个示例多计算一次。

nebula> MATCH p=(v:player{name:"Tim Duncan"})-[e:follow*0..3]->(v2:player) \
        RETURN DISTINCT v2 AS Friends, count(v2);
+-----------------------------------------------------------+-----------+
| Friends                                                   | count(v2) |
+-----------------------------------------------------------+-----------+
| ("player102" :player{age: 33, name: "LaMarcus Aldridge"}) | 1         |
| ("player100" :player{age: 42, name: "Tim Duncan"})        | 5         |
| ("player125" :player{age: 41, name: "Manu Ginobili"})     | 3         |
| ("player101" :player{age: 36, name: "Tony Parker"})       | 3         |
+-----------------------------------------------------------+-----------+

匹配多个 Edge type 的变长路径¶

用户可以在变长或定长模式中指定多个 Edge type。hop、minHop和maxHop对所有 Edge type 都生效。

nebula> MATCH p=(v:player{name:"Tim Duncan"})-[e:follow|serve*2]->(v2) \
        RETURN DISTINCT v2;
+-----------------------------------------------------------+
| v2                                                        |
+-----------------------------------------------------------+
| ("team204" :team{name: "Spurs"})                          |
| ("player100" :player{age: 42, name: "Tim Duncan"})        |
| ("team215" :team{name: "Hornets"})                        |
| ("player125" :player{age: 41, name: "Manu Ginobili"})     |
| ("player102" :player{age: 33, name: "LaMarcus Aldridge"}) |
+-----------------------------------------------------------+

匹配多个模式¶

用户可以用英文逗号（,）分隔多个模式。

nebula> MATCH (v1:player{name:"Tim Duncan"}), (v2:team{name:"Spurs"}) \
        RETURN v1,v2;
+----------------------------------------------------+----------------------------------+
| v1                                                 | v2                               |
+----------------------------------------------------+----------------------------------+
| ("player100" :player{age: 42, name: "Tim Duncan"}) | ("team204" :team{name: "Spurs"}) |
+----------------------------------------------------+----------------------------------+

多MATCH检索¶

不同的模式有不同的筛选条件时，可以使用多MATCH，会返回模式完全匹配的行。

nebula> MATCH (m)-[]->(n) WHERE id(m)=="player100" \
        MATCH (n)-[]->(l) WHERE id(n)=="player125" \
        RETURN id(m),id(n),id(l);
+-------------+-------------+-------------+
| id(m)       | id(n)       | id(l)       |
+-------------+-------------+-------------+
| "player100" | "player125" | "team204"   |
| "player100" | "player125" | "player100" |
+-------------+-------------+-------------+

OPTIONAL MATCH检索¶

参见OPTIONAL MATCH。

Performance

Nebula Graph 3.1.0 中MATCH语句的性能和资源占用得到了优化.但对性能要求较高时，仍建议使用 GO, LOOKUP, | 和 FETCH 等来替代MATCH。

OPTIONAL MATCH¶

OPTIONAL MATCH通常与MATCH语句一起使用，作为MATCH语句的可选项去匹配命中的模式，如果没有命中对应的模式，对应的列返回NULL。

openCypher 兼容性¶

本文操作仅适用于 nGQL 中的 openCypher 方式。

示例¶

MATCH语句中使用OPTIONAL MATCH的示例如下：

nebula> MATCH (m)-[]->(n) WHERE id(m)=="player100" \
        OPTIONAL MATCH (n)-[]->(l) WHERE id(n)=="player125" \
        RETURN id(m),id(n),id(l);
+-------------+-------------+-------------+
| id(m)       | id(n)       | id(l)       |
+-------------+-------------+-------------+
| "player100" | "team204"   | __NULL__    |
| "player100" | "player101" | __NULL__    |
| "player100" | "player125" | "team204"   |
| "player100" | "player125" | "player100" |
+-------------+-------------+-------------+

而使用多MATCH，不使用OPTIONAL MATCH时，会返回模式完全匹配的行。示例如下：

nebula> MATCH (m)-[]->(n) WHERE id(m)=="player100" \
        MATCH (n)-[]->(l) WHERE id(n)=="player125" \
        RETURN id(m),id(n),id(l);
+-------------+-------------+-------------+
| id(m)       | id(n)       | id(l)       |
+-------------+-------------+-------------+
| "player100" | "player125" | "team204"   |
| "player100" | "player125" | "player100" |
+-------------+-------------+-------------+

LOOKUP¶

LOOKUP根据索引遍历数据。用户可以使用LOOKUP实现如下功能：

根据WHERE子句搜索特定数据。

通过 Tag 列出点：检索指定 Tag 的所有点 ID。

通过 Edge type 列出边：检索指定 Edge type 的所有边的起始点、目的点和 rank。

统计包含指定 Tag 的点或属于指定 Edge type 的边的数量。

OpenCypher 兼容性¶

本文操作仅适用于原生 nGQL。

注意事项¶

索引会导致写性能大幅降低（降低 90%甚至更多）。请不要随意在生产环境中使用索引，除非很清楚使用索引对业务的影响。

通过Explain命令查看选择的索引。

历史版本兼容性

在 2.5.0 版本之前，如果用LOOKUP语句基于指定属性查询时该属性没有索引，系统将报错，而不会使用其它索引。

前提条件¶

请确保LOOKUP语句有至少一个索引可用。

如果已经存在相关的点、边或属性，必须在新创建索引后重建索引，才能使其生效。

Lookup语法¶

LOOKUP ON {<vertex_tag> | <edge_type>}  ==》这玩意专门针对边的搜索？？？
[WHERE <expression> [AND <expression> ...]]
YIELD <return_list> [AS <alias>]; ==》为啥是yield而不是return？？？

<return_list>
    <prop_name> [AS <col_alias>] [, <prop_name> [AS <prop_alias>] ...];

WHERE <expression>：指定遍历的过滤条件，还可以结合布尔运算符 AND 和 OR 一起使用。详情请参见 WHERE。

YIELD：定义需要返回的输出。详情请参见 YIELD。

AS：设置别名。

WHERE 语句限制¶

在LOOKUP语句中使用WHERE子句，不支持如下操作：

$-和$^。
在关系表达式中，不支持运算符两边都有字段名，例如tagName.prop1 > tagName.prop2。
不支持运算表达式和函数表达式中嵌套 AliasProp 表达式。
不支持 XOR 运算符。
不支持除STARTS WITH之外的字符串操作。
不支持图模式

检索点¶

返回 Tag 为player且name为Tony Parker的点。

nebula> CREATE TAG INDEX IF NOT EXISTS index_player ON player(name(30), age);==》是name和age都会建立索引？

nebula> REBUILD TAG INDEX index_player;
+------------+
| New Job Id |
+------------+
| 15         |
+------------+

nebula> LOOKUP ON player \
        WHERE player.name == "Tony Parker" \
        YIELD id(vertex);
+---------------+
| id(VERTEX)    |
+---------------+
| "player101"   |
+---------------+

nebula> LOOKUP ON player \
        WHERE player.name == "Tony Parker" \
        YIELD properties(vertex).name AS name, properties(vertex).age AS age;
+---------------+-----+
| name          | age |
+---------------+-----+
| "Tony Parker" | 36  |
+---------------+-----+

nebula> LOOKUP ON player \
        WHERE player.age  > 45 \
        YIELD id(vertex);
+-------------+
| id(VERTEX)  |
+-------------+
| "player144" |
| "player140" |
+-------------+

nebula> LOOKUP ON player \
        WHERE player.name STARTS WITH "B" \
        AND player.age IN [22,30] \
        YIELD properties(vertex).name, properties(vertex).age;
+-------------------------+------------------------+
| properties(VERTEX).name | properties(VERTEX).age |
+-------------------------+------------------------+
| "Ben Simmons"           | 22                     |
| "Blake Griffin"         | 30                     |
+-------------------------+------------------------+

nebula> LOOKUP ON player \
        WHERE player.name == "Kobe Bryant"\
        YIELD id(vertex) AS VertexID, properties(vertex).name AS name |\
        GO FROM $-.VertexID OVER serve \
        YIELD $-.name, properties(edge).start_year, properties(edge).end_year, properties($$).name;
+---------------+-----------------------------+---------------------------+---------------------+
| $-.name       | properties(EDGE).start_year | properties(EDGE).end_year | properties($$).name |
+---------------+-----------------------------+---------------------------+---------------------+
| "Kobe Bryant" | 1996                        | 2016                      | "Lakers"            |
+---------------+-----------------------------+---------------------------+---------------------+

检索边¶

返回 Edge type 为follow且degree为90的边。

nebula> CREATE EDGE INDEX IF NOT EXISTS index_follow ON follow(degree);

nebula> REBUILD EDGE INDEX index_follow;
+------------+
| New Job Id |
+------------+
| 62         |
+------------+

nebula> LOOKUP ON follow \
        WHERE follow.degree == 90 YIELD edge AS e;
+----------------------------------------------------+
| e                                                  |
+----------------------------------------------------+
| [:follow "player109"->"player125" @0 {degree: 90}] |
| [:follow "player118"->"player120" @0 {degree: 90}] |
| [:follow "player118"->"player131" @0 {degree: 90}] |
...

nebula> LOOKUP ON follow \
        WHERE follow.degree == 90 \
        YIELD properties(edge).degree;
+-------------------------+
| properties(EDGE).degree |
+-------------------------+
| 90                      |
| 90                      |
...

nebula> LOOKUP ON follow \
        WHERE follow.degree == 60 \
        YIELD dst(edge) AS DstVID, properties(edge).degree AS Degree |\
        GO FROM $-.DstVID OVER serve \
        YIELD $-.DstVID, properties(edge).start_year, properties(edge).end_year, properties($$).name;
+-------------+-----------------------------+---------------------------+---------------------+
| $-.DstVID   | properties(EDGE).start_year | properties(EDGE).end_year | properties($$).name |
+-------------+-----------------------------+---------------------------+---------------------+
| "player105" | 2010                        | 2018                      | "Spurs"             |
| "player105" | 2009                        | 2010                      | "Cavaliers"         |
| "player105" | 2018                        | 2019                      | "Raptors"           |
+-------------+-----------------------------+---------------------------+---------------------+

通过 Tag 列出所有的对应的点/通过 Edge type 列出边¶

如果需要通过 Tag 列出所有的点，或通过 Edge type 列出边，则 Tag、Edge type 或属性上必须有至少一个索引。

例如一个 Tag player有属性name和age，为了遍历所有包含 Tag player的点 ID，Tag player、属性name或属性age中必须有一个已经创建索引。

查找所有 Tag 为player的点 VID。

nebula> CREATE TAG IF NOT EXISTS player(name string,age int);

nebula> CREATE TAG INDEX IF NOT EXISTS player_index on player();

nebula> REBUILD TAG INDEX player_index;
+------------+
| New Job Id |
+------------+
| 66         |
+------------+

nebula> INSERT VERTEX player(name,age) \
        VALUES "player100":("Tim Duncan", 42), "player101":("Tony Parker", 36);

# 列出所有的 player。类似于 MATCH (n:player) RETURN id(n) /*, n */。

nebula> LOOKUP ON player YIELD id(vertex);
+-------------+
| id(VERTEX)  |
+-------------+
| "player100" |
| "player101" |
...

查找 Edge type 为follow的所有边的信息。

nebula> CREATE EDGE IF NOT EXISTS follow(degree int);

nebula> CREATE EDGE INDEX IF NOT EXISTS follow_index on follow();

nebula> REBUILD EDGE INDEX follow_index;
+------------+
| New Job Id |
+------------+
| 88         |
+------------+

nebula> INSERT EDGE follow(degree) \
        VALUES "player100"->"player101":(95);

# 列出所有的 follow 边。类似于 MATCH (s)-[e:follow]->(d) RETURN id(s), rank(e), id(d) /*, type(e) */。

nebula)> LOOKUP ON follow YIELD edge AS e;
+-----------------------------------------------------+
| e                                                   |
+-----------------------------------------------------+
| [:follow "player105"->"player100" @0 {degree: 70}]  |
| [:follow "player105"->"player116" @0 {degree: 80}]  |
| [:follow "player109"->"player100" @0 {degree: 80}]  |
...

统计点或边¶

统计 Tag 为player的点和 Edge type 为follow的边。

nebula> LOOKUP ON player YIELD id(vertex)|\
        YIELD COUNT(*) AS Player_Number;
+---------------+
| Player_Number |
+---------------+
| 51            |
+---------------+

nebula> LOOKUP ON follow YIELD edge AS e| \
        YIELD COUNT(*) AS Follow_Number;
+---------------+
| Follow_Number |
+---------------+
| 81            |
+---------------+

Note

使用 SHOW STATS命令也可以统计点和边。

感觉没有讲出lookup的应用场景和精髓！！！

GO¶

GO从给定起始点开始遍历图。GO语句采用的路径类型是walk，即遍历时点和边都可以重复。

openCypher 兼容性¶

本文操作仅适用于原生 nGQL。

语法¶

GO [[<M> TO] <N> STEPS ] FROM <vertex_list>
OVER <edge_type_list> [{REVERSELY | BIDIRECT}]
[ WHERE <conditions> ]
YIELD [DISTINCT] <return_list> ==》还是yield而不是return
[{ SAMPLE <sample_list> | <limit_by_list_clause> }]
[| GROUP BY {<col_name> | expression> | <position>} YIELD <col_name>]
[| ORDER BY <expression> [{ASC | DESC}]]
[| LIMIT [<offset>,] <number_rows>];

<vertex_list> ::=
    <vid> [, <vid> ...]

<edge_type_list> ::=
   <edge_type> [, <edge_type> ...]
   | *

<return_list> ::=
    <col_name> [AS <col_alias>] [, <col_name> [AS <col_alias>] ...]

<N> STEPS：指定跳数。如果没有指定跳数，默认值N为1。如果N为0，Nebula Graph 不会检索任何边。

M TO N STEPS：遍历M~N跳的边。如果M为0，输出结果和M为1相同，即GO 0 TO 2和GO 1 TO 2是相同的。

<vertex_list>：用逗号分隔的点 ID 列表，或特殊的引用符$-.id。详情参见管道符。

<edge_type_list>：遍历的 Edge type 列表。

REVERSELY | BIDIRECT：默认情况下检索的是<vertex_list>的出边（正向），REVERSELY表示反向，即检索入边；BIDIRECT 为双向，即检索正向和反向，通过返回 <edge_type>._type 字段判断方向，其正数为正向，负数为反向。

WHERE <conditions>：指定遍历的过滤条件。用户可以在起始点、目的点和边使用WHERE子句，还可以结合AND、OR、NOT、XOR一起使用。详情参见 WHERE。

Note

遍历多个 Edge type 时，WHERE子句有一些限制。例如不支持WHERE edge1.prop1 > edge2.prop2。

YIELD [DISTINCT] <return_list>：定义需要返回的输出。<return_list>建议使用 Schema 函数，当前支持src(edge)、dst(edge)、type(edge)等，暂不支持嵌套函数。详情参见 YIELD。

SAMPLE <sample_list>：用于在结果集中取样。详情参见 SAMPLE。

<limit_by_list_clause>：用于在遍历过程中逐步限制输出数量。详情参见 LIMIT。

GROUP BY：根据指定属性的值将输出分组。详情参见 GROUP BY。分组后需要再次使用YIELD定义需要返回的输出。

ORDER BY：指定输出结果的排序规则。详情参见 ORDER BY。

Note

没有指定排序规则时，输出结果的顺序不是固定的。

LIMIT [<offset>,] <number_rows>]：限制输出结果的行数。详情参见 LIMIT。

示例¶

# 返回 player102 所属队伍。
nebula> GO FROM "player102" OVER serve YIELD dst(edge); ==》默认1跳
+-----------+
| dst(EDGE) |
+-----------+
| "team203" |
| "team204" |
+-----------+

# 返回距离 player102 两跳的朋友。
nebula> GO 2 STEPS FROM "player102" OVER follow YIELD dst(edge);
+-------------+
| dst(EDGE)   |
+-------------+
| "player101" |
| "player125" |
| "player100" |
| "player102" |
| "player125" |
+-------------+

# 添加过滤条件。
nebula> GO FROM "player100", "player102" OVER serve \
        WHERE properties(edge).start_year > 1995 \  ==》引起property返回hash map
        YIELD DISTINCT properties($$).name AS team_name, properties(edge).start_year AS start_year, properties($^).name AS player_name;

+-----------------+------------+---------------------+
| team_name       | start_year | player_name         |
+-----------------+------------+---------------------+
| "Spurs"         | 1997       | "Tim Duncan"        |
| "Trail Blazers" | 2006       | "LaMarcus Aldridge" |
| "Spurs"         | 2015       | "LaMarcus Aldridge" |
+-----------------+------------+---------------------+

# 遍历多个 Edge type。属性没有值时，会显示 UNKNOWN_PROP。
nebula> GO FROM "player100" OVER follow, serve \
        YIELD properties(edge).degree, properties(edge).start_year;
+-------------------------+-----------------------------+
| properties(EDGE).degree | properties(EDGE).start_year |
+-------------------------+-----------------------------+
| 95                      | UNKNOWN_PROP                |
| 95                      | UNKNOWN_PROP                |
| UNKNOWN_PROP            | 1997                        |
+-------------------------+-----------------------------+

# 返回 player100 入方向的邻居点。
nebula> GO FROM "player100" OVER follow REVERSELY \
        YIELD src(edge) AS destination;
+-------------+
| destination |
+-------------+
| "player101" |
| "player102" |
...

# 该 MATCH 查询与上一个 GO 查询具有相同的语义。
nebula> MATCH (v)<-[e:follow]- (v2) WHERE id(v) == 'player100' \
        RETURN id(v2) AS destination;
+-------------+
| destination |
+-------------+
| "player101" |
| "player102" |
...

# 查询 player100 的朋友和朋友所属队伍。
nebula> GO FROM "player100" OVER follow REVERSELY \
        YIELD src(edge) AS id | \
        GO FROM $-.id OVER serve \
        WHERE properties($^).age > 20 \
        YIELD properties($^).name AS FriendOf, properties($$).name AS Team;
+---------------------+-----------------+
| FriendOf            | Team            |
+---------------------+-----------------+
| "Boris Diaw"        | "Spurs"         |
| "Boris Diaw"        | "Jazz"          |
| "Boris Diaw"        | "Suns"          |
...

# 该 MATCH 查询与上一个 GO 查询具有相同的语义。==》写起来更直观！！！不像上面那样，还需要自己去画图绕下。。。
nebula> MATCH (v)<-[e:follow]- (v2)-[e2:serve]->(v3)  \
        WHERE id(v) == 'player100' \
        RETURN v2.player.name AS FriendOf, v3.team.name AS Team;
+---------------------+-----------------+
| FriendOf            | Team            |
+---------------------+-----------------+
| "Boris Diaw"        | "Spurs"         |
| "Boris Diaw"        | "Jazz"          |
| "Boris Diaw"        | "Suns"          |
...

# 查询 player100 1~2 跳内的朋友。
nebula> GO 1 TO 2 STEPS FROM "player100" OVER follow \
        YIELD dst(edge) AS destination;
+-------------+
| destination |
+-------------+
| "player101" |
| "player125" |
...

# 该 MATCH 查询与上一个 GO 查询具有相同的语义。
nebula> MATCH (v) -[e:follow*1..2]->(v2) \
        WHERE id(v) == "player100" \
        RETURN id(v2) AS destination;
+-------------+
| destination |
+-------------+
| "player100" |
| "player102" |
...

# 根据年龄分组。
nebula> GO 2 STEPS FROM "player100" OVER follow \
        YIELD src(edge) AS src, dst(edge) AS dst, properties($$).age AS age \
        | GROUP BY $-.dst \
        YIELD $-.dst AS dst, collect_set($-.src) AS src, collect($-.age) AS age;
+-------------+----------------------------+----------+
| dst         | src                        | age      |
+-------------+----------------------------+----------+
| "player125" | ["player101"]              | [41]     |
| "player100" | ["player125", "player101"] | [42, 42] |
| "player102" | ["player101"]              | [33]     |
+-------------+----------------------------+----------+

# 分组并限制输出结果的行数。
nebula> $a = GO FROM "player100" OVER follow YIELD src(edge) AS src, dst(edge) AS dst; \
        GO 2 STEPS FROM $a.dst OVER follow \
        YIELD $a.src AS src, $a.dst, src(edge), dst(edge) \
        | ORDER BY $-.src | OFFSET 1 LIMIT 2;
+-------------+-------------+-------------+-------------+
| src         | $a.dst      | src(EDGE)   | dst(EDGE)   |
+-------------+-------------+-------------+-------------+
| "player100" | "player125" | "player100" | "player101" |
| "player100" | "player101" | "player100" | "player125" |
+-------------+-------------+-------------+-------------+

# 在多个边上通过 IS NOT EMPTY 进行判断。
nebula> GO FROM "player100" OVER follow WHERE properties($$).name IS NOT EMPTY YIELD dst(edge);
+-------------+
| dst(EDGE)   |
+-------------+
| "player125" |
| "player101" |
+-------------+

FETCH¶

FETCH可以获取指定点或边的属性值。

openCypher 兼容性¶

本文操作仅适用于原生 nGQL。

获取点的属性值¶

语法¶

FETCH PROP ON {<tag_name>[, tag_name ...] | *}
<vid> [, vid ...]
YIELD <return_list> [AS <alias>];

参数	说明
`tag_name`	Tag 名称。
`*`	表示当前图空间中的所有 Tag。
`vid`	点 ID。
`YIELD`	定义需要返回的输出。详情请参见 `YIELD`。
`AS`	设置别名。

基于 Tag 获取点的属性值¶

在FETCH语句中指定 Tag 获取对应点的属性值。

nebula> FETCH PROP ON player "player100" YIELD properties(vertex);
+-------------------------------+
| properties(VERTEX)            |
+-------------------------------+
| {age: 42, name: "Tim Duncan"} |
+-------------------------------+

获取点的指定属性值¶

使用YIELD子句指定返回的属性。

nebula> FETCH PROP ON player "player100" \
        YIELD properties(vertex).name AS name;
+--------------+
| name         |
+--------------+
| "Tim Duncan" |
+--------------+

获取多个点的属性值¶

指定多个点 ID 获取多个点的属性值，点之间用英文逗号（,）分隔。

nebula> FETCH PROP ON player "player101", "player102", "player103" YIELD properties(vertex);
+--------------------------------------+
| properties(VERTEX)                   |
+--------------------------------------+
| {age: 33, name: "LaMarcus Aldridge"} |
| {age: 40, name: "Tony Parker"}       |
| {age: 32, name: "Rudy Gay"}          |
+--------------------------------------+

基于多个 Tag 获取点的属性值¶

在FETCH语句中指定多个 Tag 获取属性值。Tag 之间用英文逗号（,）分隔。

# 创建新 Tag t1。
nebula> CREATE TAG IF NOT EXISTS t1(a string, b int);

# 为点 player100 添加 Tag t1。
nebula> INSERT VERTEX t1(a, b) VALUES "player100":("Hello", 100);

# 基于 Tag player 和 t1 获取点 player100 上的属性值。
nebula> FETCH PROP ON player, t1 "player100" YIELD vertex AS v;
+----------------------------------------------------------------------------+
| v                                                                          |
+----------------------------------------------------------------------------+
| ("player100" :player{age: 42, name: "Tim Duncan"} :t1{a: "Hello", b: 100}) |
+----------------------------------------------------------------------------+

用户可以在FETCH语句中组合多个 Tag 和多个点。

nebula> FETCH PROP ON player, t1 "player100", "player103" YIELD vertex AS v;
+----------------------------------------------------------------------------+
| v                                                                          |
+----------------------------------------------------------------------------+
| ("player100" :player{age: 42, name: "Tim Duncan"} :t1{a: "Hello", b: 100}) |
| ("player103" :player{age: 32, name: "Rudy Gay"})                           |
+----------------------------------------------------------------------------+

在所有标签中获取点的属性值¶

在FETCH语句中使用*获取当前图空间所有标签里，点的属性值。

nebula> FETCH PROP ON * "player100", "player106", "team200" YIELD vertex AS v;
+----------------------------------------------------------------------------+
| v                                                                          |
+----------------------------------------------------------------------------+
| ("player100" :player{age: 42, name: "Tim Duncan"} :t1{a: "Hello", b: 100}) |
| ("player106" :player{age: 25, name: "Kyle Anderson"})                      |
| ("team200" :team{name: "Warriors"})                                        |
+----------------------------------------------------------------------------+

获取边的属性值¶

语法¶

FETCH PROP ON <edge_type> <src_vid> -> <dst_vid>[@<rank>] [, <src_vid> -> <dst_vid> ...]
YIELD <output>;

参数	说明
`edge_type`	Edge type 名称。
`src_vid`	起始点 ID，表示边的起点。
`dst_vid`	目的点 ID，表示边的终点。
`rank`	边的 rank。可选参数，默认值为`0`。起始点、目的点、Edge type 和 rank 可以唯一确定一条边。
`YIELD`	定义需要返回的输出。详情请参见 `YIELD`。

获取边的所有属性值¶

# 获取连接 player100 和 team204 的边 serve 的所有属性值。
nebula> FETCH PROP ON serve "player100" -> "team204" YIELD properties(edge);
+------------------------------------+
| properties(EDGE)                   |
+------------------------------------+
| {end_year: 2016, start_year: 1997} |
+------------------------------------+

获取边的指定属性值¶

使用YIELD子句指定返回的属性。

nebula> FETCH PROP ON serve "player100" -> "team204"    \
        YIELD properties(edge).start_year;
+-----------------------------+
| properties(EDGE).start_year |
+-----------------------------+
| 1997                        |
+-----------------------------+

获取多条边的属性值¶

指定多个边模式 (<src_vid> -> <dst_vid>[@<rank>]) 获取多个边的属性值。模式之间用英文逗号（,）分隔。

nebula> FETCH PROP ON serve "player100" -> "team204", "player133" -> "team202" YIELD edge AS e;
+-----------------------------------------------------------------------+
| e                                                                     |
+-----------------------------------------------------------------------+
| [:serve "player100"->"team204" @0 {end_year: 2016, start_year: 1997}] |
| [:serve "player133"->"team202" @0 {end_year: 2011, start_year: 2002}] |
+-----------------------------------------------------------------------+

基于 rank 获取属性值¶

如果有多条边，起始点、目的点和 Edge type 都相同，可以通过指定 rank 获取正确的边属性值。

# 插入不同属性值、不同 rank 的边。
nebula> insert edge serve(start_year,end_year) \
        values "player100"->"team204"@1:(1998, 2017);==》这个是啥？rank吧？

nebula> insert edge serve(start_year,end_year) \
        values "player100"->"team204"@2:(1990, 2018);

# 默认返回 rank 为 0 的边。
nebula> FETCH PROP ON serve "player100" -> "team204" YIELD edge AS e;
+-----------------------------------------------------------------------+
| e                                                                     |
+-----------------------------------------------------------------------+
| [:serve "player100"->"team204" @0 {end_year: 2016, start_year: 1997}] |
+-----------------------------------------------------------------------+

# 要获取 rank 不为 0 的边，请在 FETCH 语句中设置 rank。
nebula> FETCH PROP ON serve "player100" -> "team204"@1 YIELD edge AS e;
+-----------------------------------------------------------------------+
| e                                                                     |
+-----------------------------------------------------------------------+
| [:serve "player100"->"team204" @1 {end_year: 2017, start_year: 1998}] |
+-----------------------------------------------------------------------+

复合语句中使用 FETCH¶

将FETCH与原生 nGQL 结合使用是一种常见的方式，例如和GO一起。

# 返回从点 player101 开始的 follow 边的 degree 值。
nebula> GO FROM "player101" OVER follow \
        YIELD src(edge) AS s, dst(edge) AS d \
        | FETCH PROP ON follow $-.s -> $-.d \
        YIELD properties(edge).degree;
+-------------------------+
| properties(EDGE).degree |
+-------------------------+
| 95                      |
| 90                      |
| 95                      |
+-------------------------+

用户也可以通过自定义变量构建类似的查询。

nebula> $var = GO FROM "player101" OVER follow \
        YIELD src(edge) AS s, dst(edge) AS d; \
        FETCH PROP ON follow $var.s -> $var.d \
        YIELD properties(edge).degree;
+-------------------------+
| properties(EDGE).degree |
+-------------------------+
| 95                      |
| 90                      |
| 95                      |
+-------------------------+

更多复合语句的详情，请参见复合查询（子句结构）。

索引介绍¶

Nebula Graph 支持两种类型索引：原生索引和全文索引。

和一般数据库意义上的索引概念不同，Nebula Graph中的索引没有加速查询的功能，是用于定位到数据的必要前置条件。==》从这里可看出图数据库的内在实现，索引定位到V、E，然后才使用图的查找算法。

原生索引¶

原生索引可以基于指定的属性查询数据，有如下特点：

包括 Tag 索引和 Edge type 索引。

必须手动重建索引（REBUILD INDEX）。

支持创建同一个 Tag 或 Edge type 的多个属性的索引（复合索引），但是不能跨 Tag 或 Edge type。

原生索引操作¶

CREATE INDEX

SHOW CREATE INDEX

SHOW INDEXES

DESCRIBE INDEX

REBUILD INDEX

SHOW INDEX STATUS

DROP INDEX

LOOKUP

MATCH

全文索引¶

全文索引是基于Elastic Search来实现的，用于对字符串属性进行前缀搜索、通配符搜索、正则表达式搜索和模糊搜索，有如下特点：

只允许创建一个属性的索引。

只能创建指定长度（不超过 256 字节）字符串的索引。

不支持逻辑操作，例如AND、OR、NOT。

Note

如果需要进行整个字符串的匹配，请使用原生索引。

全文索引操作¶

在对全文索引执行任何操作之前，请确保已经部署全文索引。详情请参见部署全文索引和部署 listener。==》是和ES配合使用的，ES建立索引，nebula图存储，二者交互实现全文检索。

部署完成后，Elasticsearch 集群上会自动创建全文索引。不支持重建或修改全文索引。如果需要删除全文索引，请在 Elasticsearch 集群上手动删除。

使用全文索引请参见使用全文索引查询。

全文检索的一个示例：

示例¶

//创建图空间。
nebula> CREATE SPACE IF NOT EXISTS basketballplayer (partition_num=3,replica_factor=1, vid_type=fixed_string(30));

//登录文本搜索客户端。
nebula> SIGN IN TEXT SERVICE (127.0.0.1:9200, HTTP);

//切换图空间。
nebula> USE basketballplayer;

//添加 listener 到 Nebula Graph 集群。
nebula> ADD LISTENER ELASTICSEARCH 192.168.8.5:9789;

//创建 Tag。
nebula> CREATE TAG IF NOT EXISTS player(name string, age int);

//创建原生索引。
nebula> CREATE TAG INDEX IF NOT EXISTS name ON player(name(20));

//重建原生索引。
nebula> REBUILD TAG INDEX;

//创建全文索引，索引名称需要以 nebula 开头。
nebula> CREATE FULLTEXT TAG INDEX nebula_index_1 ON player(name);

//重建全文索引。
nebula> REBUILD FULLTEXT INDEX;

//查看全文索引。
nebula> SHOW FULLTEXT INDEXES;
+------------------+-------------+-------------+--------+
| Name             | Schema Type | Schema Name | Fields |
+------------------+-------------+-------------+--------+
| "nebula_index_1" | "Tag"       | "player"    | "name" |
+------------------+-------------+-------------+--------+

//插入测试数据。
nebula> INSERT VERTEX player(name, age) VALUES \
  "Russell Westbrook": ("Russell Westbrook", 30), \
  "Chris Paul": ("Chris Paul", 33),\
  "Boris Diaw": ("Boris Diaw", 36),\
  "David West": ("David West", 38),\
  "Danny Green": ("Danny Green", 31),\
  "Tim Duncan": ("Tim Duncan", 42),\
  "James Harden": ("James Harden", 29),\
  "Tony Parker": ("Tony Parker", 36),\
  "Aron Baynes": ("Aron Baynes", 32),\
  "Ben Simmons": ("Ben Simmons", 22),\
  "Blake Griffin": ("Blake Griffin", 30);

//测试查询
nebula> LOOKUP ON player WHERE PREFIX(player.name, "B") YIELD id(vertex);
+-----------------+
| id(VERTEX)      |
+-----------------+
| "Boris Diaw"    |
| "Ben Simmons"   |
| "Blake Griffin" |
+-----------------+

nebula> LOOKUP ON player WHERE WILDCARD(player.name, "*ri*") YIELD player.name, player.age;
+-----------------+-----+
| name            | age |
+-----------------+-----+
| "Chris Paul"    | 33  |
| "Boris Diaw"    | 36  |
| "Blake Griffin" | 30  |
+-----------------+-----+

nebula> LOOKUP ON player WHERE WILDCARD(player.name, "*ri*") | YIELD count(*);
+----------+
| count(*) |
+----------+
| 3        |
+----------+

nebula> LOOKUP ON player WHERE REGEXP(player.name, "R.*") YIELD player.name, player.age;
+---------------------+-----+
| name                | age |
+---------------------+-----+
| "Russell Westbrook" | 30  |
+---------------------+-----+

nebula> LOOKUP ON player WHERE REGEXP(player.name, ".*") YIELD id(vertex);
+---------------------+
| id(VERTEX)          |
+---------------------+
| "Danny Green"       |
| "David West"        |
| "Russell Westbrook" |
+---------------------+
...

nebula> LOOKUP ON player WHERE FUZZY(player.name, "Tim Dunncan", AUTO, OR) YIELD player.name;
+--------------+
| name         |
+--------------+
| "Tim Duncan" |
+--------------+

//删除全文索引。
nebula> DROP FULLTEXT INDEX nebula_index_1;

GET SUBGRAPH¶

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¶

GET SUBGRAPH [WITH PROP] [<step_count> STEPS] FROM {<vid>, <vid>...}
[{IN | OUT | BOTH} <edge_type>, <edge_type>...]
YIELD [VERTICES AS <vertex_alias>] [, EDGES AS <edge_alias>];

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。

YIELD：定义需要返回的输出。可以仅返回点或边。必须设置别名。

Note

GET SUBGRAPH语句检索的路径类型为trail，即检索的路径只有点可以重复，边不可以重复。详情请参见路径。

示例¶

以下面的示例图进行演示。

A sample graph for GET SUBGRAPH

插入测试数据：

nebula> CREATE SPACE IF NOT EXISTS subgraph(partition_num=15, replica_factor=1, vid_type=fixed_string(30));
nebula> USE subgraph;
nebula> CREATE TAG IF NOT EXISTS player(name string, age int);
nebula> CREATE TAG IF NOT EXISTS team(name string);
nebula> CREATE EDGE IF NOT EXISTS follow(degree int);
nebula> CREATE EDGE IF NOT EXISTS serve(start_year int, end_year int);
nebula> INSERT VERTEX player(name, age) VALUES "player100":("Tim Duncan", 42);
nebula> INSERT VERTEX player(name, age) VALUES "player101":("Tony Parker", 36);
nebula> INSERT VERTEX player(name, age) VALUES "player102":("LaMarcus Aldridge", 33);
nebula> INSERT VERTEX team(name) VALUES "team203":("Trail Blazers"), "team204":("Spurs");
nebula> INSERT EDGE follow(degree) VALUES "player101" -> "player100":(95);
nebula> INSERT EDGE follow(degree) VALUES "player101" -> "player102":(90);
nebula> INSERT EDGE follow(degree) VALUES "player102" -> "player100":(75);
nebula> INSERT EDGE serve(start_year, end_year) VALUES "player101" -> "team204":(1999, 2018),"player102" -> "team203":(2006,  2015);

查询从点player101开始、0~1 跳、所有 Edge type 的子图。

nebula> GET SUBGRAPH 1 STEPS FROM "player101" YIELD VERTICES AS nodes, EDGES AS relationships;
+-------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------+
| nodes                                                                   | relationships                                                                                                               |
+-------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------+
| [("player101" :player{})]                                               | [[:serve "player101"->"team204" @0 {}], [:follow "player101"->"player100" @0 {}], [:follow "player101"->"player102" @0 {}]] |==》这个我能够理解！！！下面的为啥team204也冒出来了？？
| [("team204" :team{}), ("player100" :player{}), ("player102" :player{})] | [[:follow "player102"->"player100" @0 {}]]                                                                                  |
+-------------------------------------------------------------------------+-----------------------------------------------------------------------------------------------------------------------------+

返回的子图如下。

GET SUBGRAPH FROM "player101"

查询从点player101开始、0~1 跳、follow类型的入边的子图。

nebula> GET SUBGRAPH 1 STEPS FROM "player101" IN follow YIELD VERTICES AS nodes, EDGES AS relationships;
+---------------------------+---------------+
| nodes                     | relationships |
+---------------------------+---------------+
| [("player101" :player{})] | []            |
| []                        | []            |
+---------------------------+---------------+

因为player101没有follow类型的入边。所以仅返回点player101。

查询从点player101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 "player101" OUT serve YIELD VERTICES AS nodes, EDGES AS relationships;
+-------------------------------------------------------+-------------------------------------------------------------------------+
| nodes                                                 | relationships                                                           |
+-------------------------------------------------------+-------------------------------------------------------------------------+
| [("player101" :player{age: 36, name: "Tony Parker"})] | [[:serve "player101"->"team204" @0 {end_year: 2018, start_year: 1999}]] |
| [("team204" :team{name: "Spurs"})]                    | []                                                                      |
+-------------------------------------------------------+-------------------------------------------------------------------------+

返回的子图如下。

GET SUBGRAPH FROM "101" OUT serve

FAQ¶

为什么返回结果中会出现超出`step_count`跳数之外的关系？¶

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。

FAQ

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。==》啥情况，，，没有看懂为啥这么做。。。

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 MATCH 或 GO 语句。例如：

nebula> MATCH p= (v:player) -- (v2) WHERE id(v)=="A" RETURN p;

nebula> GO 1 STEPS FROM "A" OVER follow YIELD src(edge),dst(edge);

为什么返回结果中会出现低于`step_count`跳数的关系？¶

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 "player101" OUT follow YIELD VERTICES AS nodes, EDGES AS relationships;
+----------------------------------------------------+--------------------------------------------------------------------------------------+
| nodes                                              | relationships                                                                        |
+----------------------------------------------------+--------------------------------------------------------------------------------------+
| [("player101" :player{})]                          | [[:follow "player101"->"player100" @0 {}], [:follow "player101"->"player102" @0 {}]] |
| [("player100" :player{}), ("player102" :player{})] | [[:follow "player102"->"player100" @0 {}]]                                           |
+----------------------------------------------------+--------------------------------------------------------------------------------------+

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 | ALL | NOLOOP } PATH [WITH PROP] FROM <vertex_id_list> TO <vertex_id_list>
OVER <edge_type_list> [REVERSELY | BIDIRECT] 
[<WHERE clause>] [UPTO <N> STEPS] 
YIELD path as <alias>
[| ORDER BY $-.path] [| LIMIT <M>];

<vertex_id_list> ::=
    [vertex_id [, vertex_id] ...]

SHORTEST：查找最短路径。

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$-和$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。

<N>：路径的最大跳数。默认值为5。

<M>：指定返回的最大行数。

Note

FIND PATH语句检索的路径类型为trail，即检索的路径只有点可以重复，边不可以重复。详情请参见路径。

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)。

nebula> FIND SHORTEST PATH FROM "player102" TO "team204" OVER * YIELD path AS p;
+--------------------------------------------+
| p                                          |
+--------------------------------------------+
| <("player102")-[:serve@0 {}]->("team204")> |
+--------------------------------------------+

为啥是上面的结果，分析下：

(root@nebula) [basketballplayer]> FIND SHORTEST PATH FROM "player102" TO "team204" OVER * YIELD path AS p;
+--------------------------------------------+
| p                                          |
+--------------------------------------------+
| <("player102")-[:serve@0 {}]->("team204")> |
+--------------------------------------------+
Got 1 rows (time spent 737/995 us)

Tue, 24 May 2022 20:02:34 CST

(root@nebula) [basketballplayer]> FIND all PATH FROM "player102" TO "team204" OVER * YIELD path AS p;
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| p                                                                                                                                                                  |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| <("player102")-[:follow@0 {}]->("player101")-[:serve@0 {}]->("team204")>                                                                                           |
| <("player102")-[:serve@0 {}]->("team204")>                                                                                                                         |
| <("player102")-[:follow@0 {}]->("player100")-[:serve@0 {}]->("team204")>                                                                                           |
| <("player102")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player101")-[:serve@0 {}]->("team204")>                                                             |
| <("player102")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player125")-[:serve@0 {}]->("team204")>                                                             |
| <("player102")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player125")-[:serve@0 {}]->("team204")>                                                             |
| <("player102")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player102")-[:serve@0 {}]->("team204")>                               |
| <("player102")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player125")-[:serve@0 {}]->("team204")>                               |
| <("player102")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player100")-[:serve@0 {}]->("team204")>                               |
| <("player102")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player125")-[:follow@0 {}]->("player100")-[:serve@0 {}]->("team204")>                               |
| <("player102")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player125")-[:follow@0 {}]->("player100")-[:serve@0 {}]->("team204")>                               |
| <("player102")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player100")-[:serve@0 {}]->("team204")>                                                             |
| <("player102")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player102")-[:serve@0 {}]->("team204")>                                                             |
| <("player102")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player125")-[:serve@0 {}]->("team204")>                               |
| <("player102")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player101")-[:serve@0 {}]->("team204")>                               |
| <("player102")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player102")-[:follow@0 {}]->("player100")-[:serve@0 {}]->("team204")>                               |
| <("player102")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player102")-[:serve@0 {}]->("team204")> |
| <("player102")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player125")-[:serve@0 {}]->("team204")> |
| <("player102")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player125")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player125")-[:serve@0 {}]->("team204")> |
| <("player102")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player125")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player101")-[:serve@0 {}]->("team204")> |
| <("player102")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player125")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player101")-[:serve@0 {}]->("team204")> |
| <("player102")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player125")-[:serve@0 {}]->("team204")> |
| <("player102")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player102")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player125")-[:serve@0 {}]->("team204")> |
| <("player102")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player102")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player101")-[:serve@0 {}]->("team204")> |
| <("player102")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player125")-[:follow@0 {}]->("player100")-[:serve@0 {}]->("team204")> |
| <("player102")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player125")-[:follow@0 {}]->("player100")-[:serve@0 {}]->("team204")> |
| <("player102")-[:follow@0 {}]->("player100")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player102")-[:follow@0 {}]->("player101")-[:serve@0 {}]->("team204")> |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------+
Got 27 rows (time spent 2547/3444 us)

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"})> |
+--------------------------------------------------------------------------------------------------------------------------------------+

nebula> FIND ALL PATH FROM "player100" TO "team204" OVER * WHERE follow.degree is EMPTY or follow.degree >=0 YIELD path AS p;
+------------------------------------------------------------------------------+
| p                                                                            |
+------------------------------------------------------------------------------+
| <("player100")-[:serve@0 {}]->("team204")>                                   |
| <("player100")-[:follow@0 {}]->("player125")-[:serve@0 {}]->("team204")>     |
| <("player100")-[:follow@0 {}]->("player101")-[:serve@0 {}]->("team204")>     |
| ...                                                                          |
+------------------------------------------------------------------------------+

nebula> FIND NOLOOP PATH FROM "player100" TO "team204" OVER * YIELD path AS p;
+--------------------------------------------------------------------------------------------------------+
| p                                                                                                      |
+--------------------------------------------------------------------------------------------------------+
| <("player100")-[:serve@0 {}]->("team204")>                                                             |
| <("player100")-[:follow@0 {}]->("player125")-[:serve@0 {}]->("team204")>                               |
| <("player100")-[:follow@0 {}]->("player101")-[:serve@0 {}]->("team204")>                               |
| <("player100")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player125")-[:serve@0 {}]->("team204")> |
| <("player100")-[:follow@0 {}]->("player101")-[:follow@0 {}]->("player102")-[:serve@0 {}]->("team204")> |
| ...                                                                                                    |
+--------------------------------------------------------------------------------------------------------+

FAQ¶

是否支持 WHERE 子句，以实现图遍历过程中的条件过滤？¶

支持使用WHERE子句过滤，但只能过滤边属性，不支持过滤点属性。

如示例中的 WHERE follow.degree is EMPTY or follow.degree >= 0。

posted @ 2022-05-24 18:28 bonelee 阅读(1193) 评论(0) 编辑收藏举报

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Nebula入门学习——day4 nGQL中的图查询和其他算法

MATCH¶

语法¶

注意事项¶

示例¶

创建索引¶

匹配点¶

匹配 Tag¶

匹配点的属性¶

匹配点 ID¶

匹配连接的点¶

匹配路径¶

匹配边¶

匹配 Edge type¶

匹配边的属性¶

匹配多个 Edge type¶

匹配多条边¶

匹配定长路径¶

匹配变长路径¶

匹配多个 Edge type 的变长路径¶

匹配多个模式¶

多MATCH检索¶

OPTIONAL MATCH检索¶

OPTIONAL MATCH¶

openCypher 兼容性¶

示例¶

LOOKUP¶

OpenCypher 兼容性¶

注意事项¶

前提条件¶

Lookup语法¶

WHERE 语句限制¶

检索点¶

检索边¶

通过 Tag 列出所有的对应的点/通过 Edge type 列出边¶

统计点或边¶

GO¶

openCypher 兼容性¶

语法¶

示例¶

FETCH¶

openCypher 兼容性¶

获取点的属性值¶

语法¶

基于 Tag 获取点的属性值¶

获取点的指定属性值¶

获取多个点的属性值¶

基于多个 Tag 获取点的属性值¶

在所有标签中获取点的属性值¶

获取边的属性值¶

语法¶

获取边的所有属性值¶

获取边的指定属性值¶

获取多条边的属性值¶

基于 rank 获取属性值¶

复合语句中使用 FETCH¶

索引介绍¶

原生索引¶

原生索引操作¶

全文索引¶

全文索引操作¶

GET SUBGRAPH¶

语法¶

示例¶

FAQ¶

为什么返回结果中会出现超出step_count跳数之外的关系？¶

为什么返回结果中会出现低于step_count跳数的关系？¶

FIND PATH¶

语法¶

限制¶

示例¶

FAQ¶

是否支持 WHERE 子句，以实现图遍历过程中的条件过滤？¶

公告

为什么返回结果中会出现超出`step_count`跳数之外的关系？¶

为什么返回结果中会出现低于`step_count`跳数的关系？¶