NebulaGraph

https://docs.nebula-graph.com.cn/3.8.0/
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### SHOW PARTS Examples

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/7.general-query-statements/6.show/9.show-parts

Examples showing how to list all partitions and how to query a specific partition by its ID.

```ngql
nebula> SHOW PARTS;
+--------------+--------------------+--------------------+-------+
| Partition ID | Leader             | Peers              | Losts |
+--------------+--------------------+--------------------+-------+
| 1            | "192.168.2.1:9779" | "192.168.2.1:9779" | ""    |
| 2            | "192.168.2.2:9779" | "192.168.2.2:9779" | ""    |
| 3            | "192.168.2.3:9779" | "192.168.2.3:9779" | ""    |
| 4            | "192.168.2.1:9779" | "192.168.2.1:9779" | ""    |
| 5            | "192.168.2.2:9779" | "192.168.2.2:9779" | ""    |
| 6            | "192.168.2.3:9779" | "192.168.2.3:9779" | ""    |
| 7            | "192.168.2.1:9779" | "192.168.2.1:9779" | ""    |
| 8            | "192.168.2.2:9779" | "192.168.2.2:9779" | ""    |
| 9            | "192.168.2.3:9779" | "192.168.2.3:9779" | ""    |
| 10           | "192.168.2.1:9779" | "192.168.2.1:9779" | ""    |
+--------------+--------------------+--------------------+-------+

nebula> SHOW PARTS 1;
+--------------+--------------------+--------------------+-------+
| Partition ID | Leader             | Peers              | Losts |
+--------------+--------------------+--------------------+-------+
| 1            | "192.168.2.1:9779" | "192.168.2.1:9779" | ""    |
+--------------+--------------------+--------------------+-------+
```

--------------------------------

### Example configuration generation for CSV

Source: https://docs.nebula-graph.com.cn/3.8.0/import-export/nebula-exchange/parameter-reference/ex-ug-parameter

An example command to generate a CSV configuration file.

```bash
java -cp nebula-exchange_spark_2.4-3.0-SNAPSHOT.jar com.vesoft.exchange.common.GenerateConfigTemplate -s csv -p /home/nebula/csv_application.conf
```

--------------------------------

### SHOW SNAPSHOTS Example

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/7.general-query-statements/6.show/11.show-snapshots

An example showing the execution of the SHOW SNAPSHOTS command and its resulting output table.

```ngql
nebula> SHOW SNAPSHOTS;
+--------------------------------+---------+-----------------------------------------------------+
| Name                           | Status  | Hosts                                               |
+--------------------------------+---------+-----------------------------------------------------+
| "SNAPSHOT_2020_12_16_11_13_55" | "VALID" | "storaged0:9779, storaged1:9779, storaged2:9779"    |
| "SNAPSHOT_2020_12_16_11_14_10" | "VALID" | "storaged0:9779, storaged1:9779, storaged2:9779"    |
+--------------------------------+---------+-----------------------------------------------------+
```

--------------------------------

### CREATE TAG Examples

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/10.tag-statements/1.create-tag

Various examples demonstrating how to create tags with properties, no properties, default values, and TTL configurations.

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

# 创建没有属性的 Tag。
nebula> CREATE TAG IF NOT EXISTS no_property(); 

# 创建包含默认值的 Tag。
nebula> CREATE TAG IF NOT EXISTS player_with_default(name string, age int DEFAULT 20);

# 对字段 create_time 设置 TTL 为 100 秒。
nebula> CREATE TAG IF NOT EXISTS woman(name string, age int, \
        married bool, salary double, create_time timestamp) \
        TTL_DURATION = 100, TTL_COL = "create_time";
```

--------------------------------

### SHOW SPACES Example

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/7.general-query-statements/6.show/12.show-spaces

An example showing the command and its typical output listing the names of existing graph spaces.

```nGQL
nebula> SHOW SPACES;
+---------------------+
| Name                |
+---------------------+
| "docs"              |
| "basketballplayer"  |
+---------------------+
```

--------------------------------

### CREATE EDGE Examples

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/11.edge-type-statements/1.create-edge

Various examples demonstrating how to create edges with properties, no properties, default values, and TTL configurations.

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

# 创建没有属性的 Edge type。
nebula> CREATE EDGE IF NOT EXISTS no_property();

# 创建包含默认值的 Edge type。
nebula> CREATE EDGE IF NOT EXISTS follow_with_default(degree int DEFAULT 20);

# 对字段 p2 设置 TTL 为 100 秒。
nebula> CREATE EDGE IF NOT EXISTS e1(p1 string, p2 int, p3 timestamp) \
        TTL_DURATION = 100, TTL_COL = "p2";
```

--------------------------------

### SHOW COLLATION Example

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/7.general-query-statements/6.show/2.show-collation

Example output showing the available collations and their associated character sets.

```ngql
nebula> SHOW COLLATION;
+------------+---------+
| Collation  | Charset |
+------------+---------+
| "utf8_bin" | "utf8"  |
+------------+---------+
```

--------------------------------

### Example of SHOW SPACES output

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/9.space-statements/3.show-spaces

An example showing the command execution and the resulting table of graph space names.

```nGQL
nebula> SHOW SPACES;
+--------------------+
| Name               |
+--------------------+
| "cba"              |
| "basketballplayer" |
+--------------------+
```

--------------------------------

### Example gdb debugging session

Source: https://docs.nebula-graph.com.cn/3.8.0/20.appendix/0.FAQ

A complete example showing how to inspect a core file and view the backtrace.

```bash
 $ file core.1316027
 core.1316027: ELF 64-bit LSB core file, x86-64, version 1 (SYSV), SVR4-style, from '/home/workspace/fork/nebula-debug/bin/nebula-metad --flagfile /home/k', real uid: 1008, effective uid: 1008, real gid: 1008, effective gid: 1008, execfn: '/home/workspace/fork/nebula-debug/bin/nebula-metad', platform: 'x86_64'

 $ gdb /home/workspace/fork/nebula-debug/bin/nebula-metad core.1316027

 $(gdb) bt
 #0  0x00007f9de58fecf5 in __memcpy_ssse3_back () from /lib64/libc.so.6
 #1  0x0000000000eb2299 in void std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::_M_construct<char*>(char*, char*, std::forward_iterator_tag) ()
 #2  0x0000000000ef71a7 in nebula::meta::cpp2::QueryDesc::QueryDesc(nebula::meta::cpp2::QueryDesc const&) ()
 ...
```

--------------------------------

### Telnet connectivity examples

Source: https://docs.nebula-graph.com.cn/3.8.0/20.appendix/0.FAQ

Examples showing the expected output when a port is successfully connected versus when the connection is refused.

```bash
// 如果端口已开放：
$ telnet 192.168.1.10 9669
Trying 192.168.1.10...
Connected to 192.168.1.10.
Escape character is '^]'.

// 如果端口未开放：
$ telnet 192.168.1.10 9777
Trying 192.168.1.10...
telnet: connect to address 192.168.1.10: Connection refused
```

--------------------------------

### SHOW SESSIONS and SHOW SESSION Examples

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/7.general-query-statements/6.show/17.show-sessions

Examples of listing all active sessions and querying a specific session by its ID.

```ngql
nebula> SHOW SESSIONS;
+------------------+----------+--------------------+----------------------------+----------------------------+------------------+----------+--------------------+
| SessionId        | UserName | SpaceName          | CreateTime                 | UpdateTime                 | GraphAddr        | Timezone | ClientIp           |
+------------------+----------+--------------------+----------------------------+----------------------------+------------------+----------+--------------------+
| 1651220858102296 | "root"   | "basketballplayer" | 2022-04-29T08:27:38.102296 | 2022-04-29T08:50:46.282921 | "127.0.0.1:9669" | 0        | "127.0.0.1" |
| 1651199330300991 | "root"   | "basketballplayer" | 2022-04-29T02:28:50.300991 | 2022-04-29T08:16:28.339038 | "127.0.0.1:9669" | 0        | "127.0.0.1" |
| 1651112899847744 | "root"   | "basketballplayer" | 2022-04-28T02:28:19.847744 | 2022-04-28T08:17:44.470210 | "127.0.0.1:9669" | 0        | "127.0.0.1" |
| 1651041092662100 | "root"   | "basketballplayer" | 2022-04-27T06:31:32.662100 | 2022-04-27T07:01:25.200978 | "127.0.0.1:9669" | 0        | "127.0.0.1" |
| 1650959429593975 | "root"   | "basketballplayer" | 2022-04-26T07:50:29.593975 | 2022-04-26T07:51:47.184810 | "127.0.0.1:9669" | 0        | "127.0.0.1" |
| 1650958897679595 | "root"   | ""                 | 2022-04-26T07:41:37.679595 | 2022-04-26T07:41:37.683802 | "127.0.0.1:9669" | 0        | "127.0.0.1" |
+------------------+----------+--------------------+----------------------------+----------------------------+------------------+----------+--------------------+

nebula> SHOW SESSION 1635254859271703;
+------------------+----------+--------------------+----------------------------+----------------------------+------------------+----------+--------------------+
| SessionId        | UserName | SpaceName          | CreateTime                 | UpdateTime                 | GraphAddr        | Timezone | ClientIp           |
+------------------+----------+--------------------+----------------------------+----------------------------+------------------+----------+--------------------+
| 1651220858102296 | "root"   | "basketballplayer" | 2022-04-29T08:27:38.102296 | 2022-04-29T08:50:54.254384 | "127.0.0.1:9669" | 0        | "127.0.0.1" |
+------------------+----------+--------------------+----------------------------+----------------------------+------------------+----------+--------------------+
```

--------------------------------

### Example of SHOW EDGES output

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/11.edge-type-statements/4.show-edges

An example showing the execution of the SHOW EDGES command and its resulting output.

```nGQL
nebula> SHOW EDGES;
+----------+
| Name     |
+----------+
| "follow" |
| "serve"  |
+----------+
```

--------------------------------

### SHOW TAG INDEXES Example

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/7.general-query-statements/6.show/8.show-indexes

Example output when listing all Tag indexes in the current graph space.

```nGQL
nebula> SHOW TAG INDEXES;
+------------------+----------+----------+
| Index Name       | By Tag   | Columns  |
+------------------+----------+----------+
| "player_index_0" | "player" | []       |
| "player_index_1" | "player" | ["name"] |
+------------------+----------+----------+
```

--------------------------------

### LOOKUP Examples

Source: https://docs.nebula-graph.com.cn/3.8.0/2.quick-start/6.cheatsheet-for-ngql-command

Examples of using LOOKUP to retrieve vertices, edges, or perform counts.

```nGQL
LOOKUP ON player WHERE player.name == "Tony Parker" YIELD player.name AS name, player.age AS age
```

```nGQL
LOOKUP ON follow WHERE follow.degree == 90 YIELD follow.degree
```

```nGQL
LOOKUP ON player YIELD properties(vertex),id(vertex)
```

```nGQL
LOOKUP ON follow YIELD edge AS e
```

```nGQL
LOOKUP ON player YIELD id(vertex)| YIELD COUNT(*) AS Player_Count
```

```nGQL
LOOKUP ON follow YIELD edge as e | YIELD COUNT(*) AS Like_Count
```

--------------------------------

### Example of SHOW TAGS output

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/10.tag-statements/4.show-tags

An example showing the execution of the SHOW TAGS statement and its typical output format.

```ngql
nebula> SHOW TAGS;
+----------+
| Name     |
+----------+
| "player" |
| "team"   |
+----------+
```

--------------------------------

### Example: SHOW ROLES in basketballplayer

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/7.general-query-statements/6.show/10.show-roles

An example showing the roles assigned to users in the 'basketballplayer' graph space.

```nGQL
nebula> SHOW ROLES in basketballplayer;
+---------+-----------+
| Account | Role Type |
+---------+-----------+
| "user1" | "ADMIN"   |
+---------+-----------+
```

--------------------------------

### SHOW HOSTS Examples

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/7.general-query-statements/6.show/6.show-hosts

Examples of using SHOW HOSTS to display all cluster hosts, or specifically Graph, Storage, or Meta service hosts.

```ngql
nebula> SHOW HOSTS;
+-------------+-------+----------+--------------+----------------------------------+------------------------------+---------+
| Host        | Port  | Status   | Leader count | Leader distribution              | Partition distribution       | Version |
+-------------+-------+----------+--------------+----------------------------------+------------------------------+---------+
| "storaged0" | 9779  | "ONLINE" | 8            | "docs:5, basketballplayer:3"     | "docs:5, basketballplayer:3" | "3.8.0" |
| "storaged1" | 9779  | "ONLINE" | 9            | "basketballplayer:4, docs:5"     | "docs:5, basketballplayer:4" | "3.8.0" |
| "storaged2" | 9779  | "ONLINE" | 8            | "basketballplayer:3, docs:5"     | "docs:5, basketballplayer:3" | "3.8.0" |
+-------------+-------+----------+--------------+----------------------------------+------------------------------+---------+

nebula> SHOW HOSTS GRAPH;
+-----------+------+----------+---------+--------------+---------+
| Host      | Port | Status   | Role    | Git Info Sha | Version |
+-----------+------+----------+---------+--------------+---------+
| "graphd"  | 9669 | "ONLINE" | "GRAPH" | "3ba41bd"    | "3.8.0" |
| "graphd1" | 9669 | "ONLINE" | "GRAPH" | "3ba41bd"    | "3.8.0" |
| "graphd2" | 9669 | "ONLINE" | "GRAPH" | "3ba41bd"    | "3.8.0" |
+-----------+------+----------+---------+--------------+---------+

nebula> SHOW HOSTS STORAGE;
+-------------+------+----------+-----------+--------------+---------+
| Host        | Port | Status   | Role      | Git Info Sha | Version |
+-------------+------+----------+-----------+--------------+---------+
| "storaged0" | 9779 | "ONLINE" | "STORAGE" | "3ba41bd"    | "3.8.0" |
| "storaged1" | 9779 | "ONLINE" | "STORAGE" | "3ba41bd"    | "3.8.0" |
| "storaged2" | 9779 | "ONLINE" | "STORAGE" | "3ba41bd"    | "3.8.0" |
+-------------+------+----------+-----------+--------------+---------+

nebula> SHOW HOSTS META;
+----------+------+----------+--------+--------------+---------+
| Host     | Port | Status   | Role   | Git Info Sha | Version |
+----------+------+----------+--------+--------------+---------+
| "metad2" | 9559 | "ONLINE" | "META" | "3ba41bd"    | "3.8.0" |
| "metad0" | 9559 | "ONLINE" | "META" | "3ba41bd"    | "3.8.0" |
| "metad1" | 9559 | "ONLINE" | "META" | "3ba41bd"    | "3.8.0" |
+----------+------+----------+--------+--------------+---------+
```

--------------------------------

### DESCRIBE SPACE Example

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/9.space-statements/4.describe-space

An example showing the command to describe the 'basketballplayer' space and the resulting output table containing space metadata.

```ngql
nebula> DESCRIBE SPACE basketballplayer;
+----+--------------------+------------------+----------------+---------+------------+--------------------+---------+
| ID | Name               | Partition Number | Replica Factor | Charset | Collate    | Vid Type           | Comment |
+----+--------------------+------------------+----------------+---------+------------+--------------------+---------+
| 1  | "basketballplayer" | 10               | 1              | "utf8"  | "utf8_bin" | "FIXED_STRING(32)" |         |
+----+--------------------+------------------+----------------+---------+------------+--------------------+---------+
```

--------------------------------

### Repeat command example with output

Source: https://docs.nebula-graph.com.cn/3.8.0/nebula-console

Example of repeating a query 3 times. The output shows each execution result and the average time.

```nGQL
nebula> :repeat 3;
nebula> GO FROM "player100" OVER follow YIELD dst(edge);
+-------------+
| dst(EDGE)   |
+-------------+
| "player101" |
| "player125" |
+-------------+
Got 2 rows (time spent 2602/3214 us)

Fri, 20 Aug 2021 06:36:05 UTC

+-------------+
| dst(EDGE)   |
+-------------+
| "player101" |
| "player125" |
+-------------+
Got 2 rows (time spent 583/849 us)

Fri, 20 Aug 2021 06:36:05 UTC

+-------------+
| dst(EDGE)   |
+-------------+
| "player101" |
| "player125" |
+-------------+
Got 2 rows (time spent 496/671 us)

Fri, 20 Aug 2021 06:36:05 UTC

Executed 3 times, (total time spent 3681/4734 us), (average time spent 1227/1578 us)
```

--------------------------------

### Spark Submit Command Example

Source: https://docs.nebula-graph.com.cn/3.8.0/import-export/nebula-exchange/use-exchange/ex-ug-import-from-jdbc

Example of the spark-submit command with actual paths for the JAR and configuration file. The JAR can be obtained by compiling or from the Maven repository.

```bash
${SPARK_HOME}/bin/spark-submit  --master "local" --class com.vesoft.nebula.exchange.Exchange  /root/nebula-echange/nebula-exchange/target/nebula-exchange_spark_2.4-3.8.0.jar  -c /root/nebula-exchange/nebula-exchange/target/classes/jdbc_application.conf
```

--------------------------------

### Install and start NebulaGraph Agent

Source: https://docs.nebula-graph.com.cn/3.8.0/backup-and-restore/nebula-br/2.compile-br

Download, rename, and make the Agent binary executable, then start it with `--agent` and `--meta` parameters. The example uses `--ratelimit=1048576` to limit upload/download speed. Verify the Agent is registered by running `SHOW HOSTS AGENT`; the expected output shows the Agent as `ONLINE`.

```bash
wget https://github.com/vesoft-inc/nebula-agent/releases/download/v3.7.1/agent-3.7.1-linux-amd64

```

```bash
sudo mv agent-3.7.1-linux-amd64 agent

```

```bash
sudo chmod +x agent

```

```bash
sudo nohup ./agent --agent="<agent_node_ip>:8888" --meta="<metad_node_ip>:9559" > nebula_agent.log 2>&1 &

```

```bash
sudo nohup ./agent --agent="192.168.8.129:8888" --meta="192.168.8.129:9559" --ratelimit=1048576 > nebula_agent.log 2>&1 &

```

```bash
nebula> SHOW HOSTS AGENT;
+-----------------+------+----------+---------+--------------+---------+
| Host            | Port | Status   | Role    | Git Info Sha | Version |
+-----------------+------+----------+---------+--------------+---------+
| "192.168.8.129" | 8888 | "ONLINE" | "AGENT" | "96646b8"    |         |
+-----------------+------+----------+---------+--------------+---------+  

```

--------------------------------

### Helm installation output: kubectl get pods

Source: https://docs.nebula-graph.com.cn/3.8.0/k8s-operator/4.cluster-administration/4.1.installation/4.1.1.cluster-install

Output of a kubectl get pods command after installing NebulaGraph with Helm. Shows all pods in Running status with 1/1 readiness, including nebula-exporter, graphd, metad, and storaged components.

```text
NAME                               READY   STATUS    RESTARTS   AGE
nebula-exporter-854c76989c-mp725   1/1     Running   0          14h
nebula-graphd-0                    1/1     Running   0          14h
nebula-graphd-1                    1/1     Running   0          14h
nebula-metad-0                     1/1     Running   0          14h
nebula-metad-1                     1/1     Running   0          14h
nebula-metad-2                     1/1     Running   0          14h
nebula-storaged-0                  1/1     Running   0          14h
nebula-storaged-1                  1/1     Running   0          14h
nebula-storaged-2                  1/1     Running   0          14h
```

--------------------------------

### GET SUBGRAPH query example

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/7.general-query-statements/7.get-subgraph

An example of querying a subgraph with a specified step count, showing that the query stops when no additional data is found.

```nGQL
# 查询从点 player101 开始、0~100 跳、follow 类型的出边的子图。
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 {}]]                                           |
+----------------------------------------------------+--------------------------------------------------------------------------------------+
```

--------------------------------

### 编辑 GRUB 配置文件

Source: https://docs.nebula-graph.com.cn/3.8.0/5.configurations-and-logs/1.configurations/6.kernel-config

打开 GRUB 配置文件以准备修改内核启动参数。

```bash
sudo vi /etc/default/grub
```

--------------------------------

### substr() and substring() extraction

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/6.functions-and-expressions/2.string

Examples of extracting substrings using specified start positions and lengths.

```nGQL
nebula> RETURN substr("abcdefg",2,4);
+-----------------------+
| substr("abcdefg",2,4) |
+-----------------------+
| "cdef"                |
+-----------------------+
```

```nGQL
nebula> RETURN substr("abcdefg",0,4);
+-----------------------+
| substr("abcdefg",0,4) |
+-----------------------+
| "abcd"                |
+-----------------------+
```

```nGQL
nebula> RETURN substr("abcdefg",2);
+---------------------+
| substr("abcdefg",2) |
+---------------------+
| "cdefg"             |
+---------------------+
```

--------------------------------

### Subquery as Starting Point

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/7.general-query-statements/3.go

Demonstrates using the result of a subquery as the starting point for a subsequent graph traversal. The first example uses GO, and the second uses MATCH to achieve the same semantic result.

```ngql
nebula> GO FROM "player100" OVER follow \
        YIELD dst(edge) AS id | \
        GO FROM $-.id OVER serve \
        WHERE properties($^).age > 20 \
        YIELD properties($^).name AS Friend, properties($$).name AS Team;
+---------------------+-----------------+
| Friend              | Team            |
+---------------------+-----------------+
| "Tony Parker"       | "Spurs"         |
| "Tony Parker"       | "Hornets"       |
| "Manu Ginobili"     | "Spurs"         |
+---------------------+-----------------+
```

```ngql
nebula> MATCH (v)-[e:follow]-> (v2)-[e2:serve]->(v3)  \
        WHERE id(v) == 'player100' \
        AND properties(v2).age > 20 \
        RETURN v2.player.name AS Friend, v3.team.name AS Team;
+---------------------+-----------------+
| Friend              | Team            |
+---------------------+-----------------+
| "Tony Parker"       | "Spurs"         |
| "Tony Parker"       | "Hornets"       |
| "Manu Ginobili"     | "Spurs"         |
+---------------------+-----------------+
```

--------------------------------

### 字符串前缀匹配运算符 (NOT) STARTS WITH

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/5.operators/7.string

使用 (NOT) STARTS WITH 运算符判断字符串是否以特定字符串开头。

```nGQL
nebula> RETURN 'apple' STARTS WITH 'app', 'apple' STARTS WITH 'a', 'apple' STARTS WITH toUpper('a');
+-----------------------------+---------------------------+------------------------------------+
| ("apple" STARTS WITH "app") | ("apple" STARTS WITH "a") | ("apple" STARTS WITH toUpper("a")) |
+-----------------------------+---------------------------+------------------------------------+
| true                        | true                      | false                              |
+-----------------------------+---------------------------+------------------------------------+

nebula> RETURN 'apple' STARTS WITH 'b','apple' NOT STARTS WITH 'app';
+---------------------------+---------------------------------+
| ("apple" STARTS WITH "b") | ("apple" NOT STARTS WITH "app") |
+---------------------------+---------------------------------+
| false                     | false                           |
+---------------------------+---------------------------------+
```

--------------------------------

### 编译示例程序

Source: https://docs.nebula-graph.com.cn/3.8.0/14.client/3.nebula-cpp-client

使用 g++ 编译 SessionExample.cpp，需指定库路径和头文件路径。

```bash
$ LIBRARY_PATH=<library_folder_path>:$LIBRARY_PATH g++ -std=c++11 SessionExample.cpp -I<include_folder_path> -lnebula_graph_client -o session_example
```

```bash
$ LIBRARY_PATH=/usr/local/nebula/lib64:$LIBRARY_PATH g++ -std=c++11 SessionExample.cpp -I/usr/local/nebula/include -lnebula_graph_client -o session_example
```

--------------------------------

### GET SUBGRAPH 语法结构

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/7.general-query-statements/7.get-subgraph

GET SUBGRAPH 语句的基本语法结构，包含步数、起始点、边类型、过滤条件和输出定义。

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

--------------------------------

### Start NebulaGraph Service Command

Source: https://docs.nebula-graph.com.cn/3.8.0/4.deployment-and-installation/2.compile-and-install-nebula-graph/deploy-nebula-graph-cluster

Command to start specific or all NebulaGraph services.

```bash
sudo /usr/local/nebula/scripts/nebula.service start <metad|graphd|storaged|all>

```

--------------------------------

### Algorithm configuration file example

Source: https://docs.nebula-graph.com.cn/3.8.0/graph-computing/nebula-algorithm

A sample configuration file for submitting algorithm tasks, covering Spark, NebulaGraph, and local file settings.

```hocon
{
    # Spark 相关配置
    spark: {
    app: {
        name: LPA
        # Spark 分片数量
        partitionNum:100
    }
    master:local
    }

    data: {
    # 数据源，可选值为 nebula、csv、json。
    source: nebula
    # 数据落库，即图计算的结果写入的目标，可选值为 nebula、csv、json。
    sink: nebula
    # 算法是否需要权重。
    hasWeight: false
    }

    #  NebulaGraph 相关配置
    nebula: {
    # 数据源。 NebulaGraph 作为图计算的数据源时，nebula.read 的配置才生效。
    read: {
        # 所有 Meta 服务的 IP 地址和端口，多个地址用英文逗号（,）分隔。格式："ip1:port1,ip2:port2"。
        # 使用 docker-compose 部署，端口需要填写 docker-compose 映射到外部的端口
        # 可以用`docker-compose ps`查看
        metaAddress: "192.168.*.10:9559"
        #  NebulaGraph 图空间名称
        space: basketballplayer
        # NebulaGraph Edge type, 多个 labels 时，多个边的数据将合并。
        labels: ["serve"]
        # NebulaGraph 每个 Edge type 的属性名称，此属性将作为算法的权重列，请确保和 Edge type 对应。
        weightCols: ["start_year"]
    }

    # 数据落库。图计算结果落库到 NebulaGraph 时，nebula.write 的配置才生效。
    write:{
        # Graph 服务的 IP 地址和端口，多个地址用英文逗号（,）分隔。格式："ip1:port1,ip2:port2"。
        # 使用 docker-compose 部署，端口需要填写 docker-compose 映射到外部的端口
        # 可以用`docker-compose ps`查看
        graphAddress: "192.168.*.11:9669"
        # 所有 Meta 服务的 IP 地址和端口，多个地址用英文逗号（,）分隔。格式："ip1:port1,ip2:port2"。
        # 使用 docker-compose 部署，端口需要填写 docker-compose 映射到外部的端口
        # 可以用`docker-compose ps`查看
        metaAddress: "192.168.*.12:9559"
        user:root
        pswd:nebula
        # 在提交图计算任务之前需要自行创建图空间及 Tag
        #  NebulaGraph 图空间名称
        space:nb
        # NebulaGraph Tag 名称，图计算结果会写入该 Tag。Tag 中的属性名称固定如下：
        # PageRank：pagerank
        # Louvain：louvain
        # ConnectedComponent：cc
        # StronglyConnectedComponent：scc
        # LabelPropagation：lpa
        # ShortestPath：shortestpath
        # DegreeStatic：degree、inDegree、outDegree
        # KCore：kcore
        # TriangleCount：tranglecpunt
        # BetweennessCentrality：betweennedss
        tag:pagerank
    }
    }  

    local: {
    # 数据源。图计算的数据源为 csv 文件或 json 文件时，local.read 的配置才生效。
    read:{
        filePath: "hdfs://127.0.0.1:9000/edge/work_for.csv"
        # 如果 CSV 文件没有表头，使用 [_c0, _c1, _c2, ..., _cn] 表示其表头，有表头或者是 json 文件时，直接使用表头名称即可。
        # 起始点 ID 列的表头。
        srcId:"_c0"
        # 目的点 ID 列的表头。
        dstId:"_c1"
        # 权重列的表头
        weight: "_c2"
        # csv 文件是否有表头
        header: false
        # csv 文件的分隔符
        delimiter:","
    }

    # 数据落库。图计算结果落库到 csv 文件或 text 文件时，local.write 的配置才生效。
    write:{
        resultPath:/tmp/
    }

    algorithm: {
    # 需要执行的算法，可选值为：
    # pagerank、louvain、connectedcomponent、labelpropagation、shortestpaths、
    # degreestatic、kcore、stronglyconnectedcomponent、trianglecount、
    # betweenness、graphtriangleCount。
    executeAlgo: pagerank

    # PageRank 参数
    pagerank: {
        maxIter: 10
        resetProb: 0.15  
        encodeId:false # 如果点 ID 是字符串类型，请配置为 true。
    }

    # Louvain 参数
    louvain: {
        maxIter: 20
        internalIter: 10
        tol: 0.5
        encodeId:false # 如果点 ID 是字符串类型，请配置为 true。
    }

    # ...
    }
    }
}
```

--------------------------------

### kubectl get svc 返回示例

Source: https://docs.nebula-graph.com.cn/3.8.0/k8s-operator/4.cluster-administration/4.2.configuration

展示 kubectl get svc 命令的输出，显示各服务的端口已更新为自定义值。

```text
NAME                        TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)                      AGE
nebula-graphd-headless      ClusterIP   None             <none>        3669/TCP,8080/TCP            10m
nebula-graphd-svc           ClusterIP   10.102.13.115    <none>        3669/TCP,8080/TCP            10m
nebula-metad-headless       ClusterIP   None             <none>        9559/TCP,8081/TCP            11m
nebula-storaged-headless    ClusterIP   None             <none>        9779/TCP,8082/TCP,9778/TCP   11m
```

--------------------------------

### DROP TAG Example

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/10.tag-statements/2.drop-tag

An example showing the creation of a tag followed by its deletion.

```ngql
nebula> CREATE TAG IF NOT EXISTS test(p1 string, p2 int);
nebula> DROP TAG test;
```

--------------------------------

### 重启操作系统

Source: https://docs.nebula-graph.com.cn/3.8.0/5.configurations-and-logs/1.configurations/6.kernel-config

重启系统以使 GRUB 配置更改生效。

```bash
sudo reboot
```

--------------------------------

### 更新 GRUB 配置

Source: https://docs.nebula-graph.com.cn/3.8.0/5.configurations-and-logs/1.configurations/6.kernel-config

根据操作系统类型更新 GRUB 配置。

```bash
sudo grub2-mkconfig -o /boot/grub2/grub.cfg
```

```bash
sudo update-grub
```

--------------------------------

### CLEAR SPACE Example

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/9.space-statements/6.clear-space

A simple example of clearing data from the basketballplayer graph space.

```ngql
CLEAR SPACE basketballplayer;
```

--------------------------------

### OpenCypher ORDER BY Examples

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/8.clauses-and-options/order-by

Examples of sorting results in openCypher, including multi-column sorting.

```Cypher
nebula> MATCH (v:player) RETURN v.player.name AS Name, v.player.age AS Age  \
        ORDER BY Name DESC;
+-----------------+-----+
| Name            | Age |
+-----------------+-----+
| "Yao Ming"      | 38  |
| "Vince Carter"  | 42  |
| "Tracy McGrady" | 39  |
| "Tony Parker"   | 36  |
+-----------------+-----+
...

# 首先以年龄排序，如果年龄相同，再以姓名排序。
nebula> MATCH (v:player) RETURN v.player.age AS Age, v.player.name AS Name  \
        ORDER BY Age DESC, Name ASC;
+-----+-------------------+
| Age | Name              |
+-----+-------------------+
| 47  | "Shaquille O'Neal" |
| 46  | "Grant Hill"      |
| 45  | "Jason Kidd"      |
| 45  | "Steve Nash"      |
+-----+-------------------+
...
```

--------------------------------

### Example of SHOW USERS output

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/7.general-query-statements/6.show/16.show-users

Displays the list of users and their configured IP whitelists.

```nGQL
nebula> SHOW USERS;
+---------+-----------------+
| Account | IP Whitelist    |
+---------+-----------------+
| "root"  | ""              |
| "user1" | ""              |
| "user2" | "192.168.10.10" |
+---------+-----------------+
```

--------------------------------

### INTERSECT Examples

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/5.operators/6.set

Examples demonstrating the use of INTERSECT with GO, MATCH, and UNWIND statements.

```ngql
# 返回两个查询结果的交集。
nebula> GO FROM "player102" OVER follow \
        YIELD dst(edge) AS id, properties(edge).degree AS Degree, properties($$).age AS Age \
        INTERSECT \
        GO FROM "player100" OVER follow \
        YIELD dst(edge) AS id, properties(edge).degree AS Degree, properties($$).age AS Age;
+----+--------+-----+
| id | Degree | Age |
+----+--------+-----+
+----+--------+-----+

# 返回 player102 的邻居和边数据与 player100 的邻居和边数据之间的交集。
nebula> MATCH (v:player)-[e:follow]->(v2) \
        WHERE id(v) == "player102" \
        RETURN id(v2) As id, e.degree As Degree, v2.player.age AS Age \
        INTERSECT \
        MATCH (v:player)-[e:follow]->(v2) \
        WHERE id(v) == "player100" \
        RETURN id(v2) As id, e.degree As Degree, v2.player.age AS Age;
+----+--------+-----+
| id | Degree | Age |
+----+--------+-----+
+----+--------+-----+

# 返回 [1,2] 与 [1,2,3,4] 的交集。
nebula> UNWIND [1,2] AS a RETURN a \
        INTERSECT \
        UNWIND [1,2,3,4] AS a \
        RETURN a;
+---+
| a |
+---+
| 1 |
| 2 |
+---+
```

--------------------------------

### DROP TAG INDEX Example

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/14.native-index-statements/6.drop-native-index

An example of dropping a tag index named player_index_0.

```ngql
nebula> DROP TAG INDEX player_index_0;
```

--------------------------------

### Compile and Package

Source: https://docs.nebula-graph.com.cn/3.8.0/connector/nebula-flink-connector

Run the Maven command to compile and package the connector, skipping tests.

```bash
$ mvn clean package -Dmaven.test.skip=true
```

--------------------------------

### DROP EDGE Example

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/11.edge-type-statements/2.drop-edge

An example showing the creation of an edge type followed by its deletion.

```ngql
nebula> CREATE EDGE IF NOT EXISTS e1(p1 string, p2 int);
nebula> DROP EDGE e1;
```

--------------------------------

### 构建并启动 Studio 服务

Source: https://docs.nebula-graph.com.cn/3.8.0/nebula-studio/deploy-connect/st-ug-deploy

使用 docker-compose up -d 构建并启动 Studio 服务，其中 -d 表示在后台运行服务容器。

```bash
docker-compose up -d

```

--------------------------------

### 检查 Studio 服务状态（systemctl）

Source: https://docs.nebula-graph.com.cn/3.8.0/nebula-studio/troubleshooting/st-ug-connection-errors

使用 RPM 或 DEB 包部署的 Studio，运行此命令查看服务运行状态。

```bash
systemctl status nebula-graph-studio
```

--------------------------------

### 使用 startNode() 函数获取路径起始点

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/6.functions-and-expressions/4.schema

startNode() 获取路径并返回其起始点信息，包括 ID、Tag、属性和值。

```nebula
nebula> MATCH p = (a :player {name : "Tim Duncan"})-[r:serve]-(t) \
        RETURN startNode(p);
+----------------------------------------------------+
| startNode(p)                                       |
+----------------------------------------------------+
| ("player100" :player{age: 42, name: "Tim Duncan"}) |
+----------------------------------------------------+
```

--------------------------------

### Show Tag Index Creation Information

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/14.native-index-statements/2.1.show-create-index

Example showing how to list tag indexes and then retrieve the creation statement for a specific tag index.

```nGQL
nebula> SHOW TAG INDEXES;
+------------------+----------+----------+
| Index Name       | By Tag   | Columns  |
+------------------+----------+----------+
| "player_index_0" | "player" | []       |
| "player_index_1" | "player" | ["name"] |
+------------------+----------+----------+

nebula> SHOW CREATE TAG INDEX player_index_1;
+------------------+--------------------------------------------------+
| Tag Index Name   | Create Tag Index                                 |
+------------------+--------------------------------------------------+
| "player_index_1" | "CREATE TAG INDEX `player_index_1` ON `player` ( |
|                  |  `name`(20)                                      |
|                  | )"                                               |
+------------------+--------------------------------------------------+
```

--------------------------------

### FETCH PROP ON Vertex Examples

Source: https://docs.nebula-graph.com.cn/3.8.0/2.quick-start/6.cheatsheet-for-ngql-command

Examples of fetching vertex properties using different tag specifications.

```ngql
FETCH PROP ON player "player100" YIELD properties(vertex)
```

```ngql
FETCH PROP ON player "player100" YIELD player.name AS name
```

```ngql
FETCH PROP ON player "player101", "player102", "player103" YIELD properties(vertex)
```

```ngql
FETCH PROP ON player, t1 "player100", "player103" YIELD properties(vertex)
```

```ngql
FETCH PROP ON * "player100", "player106", "team200" YIELD properties(vertex)
```

--------------------------------

### DESCRIBE TAG INDEX Examples

Source: https://docs.nebula-graph.com.cn/3.8.0/3.ngql-guide/14.native-index-statements/3.describe-native-index

Examples showing the output of DESCRIBE TAG INDEX for different indexes.

```ngql
nebula> DESCRIBE TAG INDEX player_index_0;
+--------+--------------------+
| Field  | Type               |
+--------+--------------------+
| "name" | "fixed_string(30)" |
+--------+--------------------+

nebula> DESCRIBE TAG INDEX player_index_1;
+--------+--------------------+
| Field  | Type               |
+--------+--------------------+
| "name" | "fixed_string(10)" |
| "age"  | "int64"            |
+--------+--------------------+
```

--------------------------------

### 使用 ClusterIP 连接示例 (kubectl run example)

Source: https://docs.nebula-graph.com.cn/3.8.0/k8s-operator/2.get-started/2.4.connect-to-cluster

使用实际的 ClusterIP 10.98.213.34 和端口 9669 连接 NebulaGraph，并展示成功连接后的命令行提示符。

```bash
kubectl run -ti --image vesoft/nebula-console:v3.8.0 --restart=Never -- nebula-console -addr 10.98.213.34  -port 9669 -u root -p vesoft
```

```bash
If you don't see a command prompt, try pressing enter.

(root@nebula) [(none)]>


```
Tokens:
Raw