Nebula Graph基础

服务部署

1. Nebula Graph安装与启动

https://docs.nebula-graph.com.cn/3.2.0/4.deployment-and-installation/2.compile-and-install-nebula-graph/2.install-nebula-graph-by-rpm-or-deb/

1. RPM/DEB包安装和启动

wget https://oss-cdn.nebula-graph.com.cn/package/3.2.0/nebula-graph-3.2.0.ubuntu1804.amd64.deb  # 下载安装包
dpkg -i nebula-graph-3.2.0.ubuntu1804.amd64.deb  # 安装

sudo /usr/local/nebula/scripts/nebula.service start all  # 启动服务
sudo /usr/local/nebula/scripts/nebula.service status all  # 查看状态

2. 使用docker compose安装和启动

git clone -b release-3.2 https://github.com/vesoft-inc/nebula-docker-compose.git

cd nebula-docker-compose/
docker compose up -d  # 启动 Nebula Graph 服务

docker compose ps  # 查看 Nebula Console 容器名称
NAME                                COMMAND                   SERVICE             STATUS              PORTS
nebula-docker-compose-console-1     "sh -c 'sleep 3 &&\nn…"   console             running             
nebula-docker-compose-graphd-1      "/usr/local/nebula/b…"    graphd              running (healthy)   0.0.0.0:9669->9669/tcp, 0.0.0.0:32793->19669-19670/tcp
nebula-docker-compose-graphd1-1     "/usr/local/nebula/b…"    graphd1             running (healthy)   0.0.0.0:32792->9669/tcp, 0.0.0.0:32790->19669-19670/tcp
nebula-docker-compose-graphd2-1     "/usr/local/nebula/b…"    graphd2             running (healthy)   0.0.0.0:32789->9669/tcp, 0.0.0.0:32787->19669-19670/tcp
nebula-docker-compose-metad0-1      "/usr/local/nebula/b…"    metad0              running (healthy)   0.0.0.0:32776->9559/tcp, 0.0.0.0:32774->19559-19560/tcp
nebula-docker-compose-metad1-1      "/usr/local/nebula/b…"    metad1              running (healthy)   0.0.0.0:32775->9559/tcp, 0.0.0.0:32773->19559-19560/tcp
nebula-docker-compose-metad2-1      "/usr/local/nebula/b…"    metad2              running (healthy)   0.0.0.0:32772->9559/tcp, 0.0.0.0:32769->19559-19560/tcp
nebula-docker-compose-storaged0-1   "/usr/local/nebula/b…"    storaged0           running (healthy)   0.0.0.0:32781->9779/tcp, 0.0.0.0:32778->19779-19780/tcp
nebula-docker-compose-storaged1-1   "/usr/local/nebula/b…"    storaged1           running (healthy)   0.0.0.0:32785->9779/tcp, 0.0.0.0:32783->19779-19780/tcp
nebula-docker-compose-storaged2-1   "/usr/local/nebula/b…"    storaged2           running (healthy)   0.0.0.0:32784->9779/tcp, 0.0.0.0:32782->19779-19780/tcp

docker exec -it nebuladockercompose_console_1 /bin/sh  # 进入Nebula Console 容器

/usr/local/bin/nebula-console -u <user_name> -p <password> --address=graphd --port=9669  # 通过 Nebula Console 连接 Nebula Graph

nebula> SHOW HOSTS;  # 查看集群状态
+-------------+------+-----------+----------+--------------+----------------------+------------------------+---------+
| Host        | Port | HTTP port | Status   | Leader count | Leader distribution  | Partition distribution | Version |
+-------------+------+-----------+----------+--------------+----------------------+------------------------+---------+
| "storaged0" | 9779 | 19669     | "ONLINE" | 0            | "No valid partition" | "No valid partition"   | "3.2.0" |
| "storaged1" | 9779 | 19669     | "ONLINE" | 0            | "No valid partition" | "No valid partition"   | "3.2.0" |
| "storaged2" | 9779 | 19669     | "ONLINE" | 0            | "No valid partition" | "No valid partition"   | "3.2.0" |
+-------------+------+-----------+----------+--------------+----------------------+------------------------+---------+

2. Nebula Studio安装与启动

https://docs.nebula-graph.com.cn/3.2.0/nebula-studio/deploy-connect/st-ug-deploy/

wget https://oss-cdn.nebula-graph.com.cn/nebula-graph-studio/3.4.1/nebula-graph-studio-3.4.1.x86_64.rpm  # 下载安装包
sudo rpm -i nebula-graph-studio-3.4.1.x86_64.rpm

顺利安装后会自动启动，在浏览器地址栏输入 http://127.0.0.1:7001

输入Nebula Graph 的 Graph 服务本机 IP 地址以及服务所用端口，默认端口为 9669。

3. 部署遇到的问题

1. 使用docker compose安装nebula-graph时可能会出现由于网络问题导致下载文件失败，可以多试几次。
2. Nebula Studio的deb包无法在WSL环境安装，会提示System has not been booted with systemd as init system (PID 1). Can't operate. Failed to connect to bus: Host is down。

用法

支持nGQL和openCypher 9
https://docs.nebula-graph.com.cn/3.1.0/3.ngql-guide/14.native-index-statements/1.create-native-index/

1. MATCH语句
   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。
   参考：https://docs.nebula-graph.com.cn/3.1.0/3.ngql-guide/7.general-query-statements/2.match/
   使用MATCH语句时注意需要创建索引

   # 匹配节点
   MATCH (v:Disease) RETURN v LIMIT 10;
   MATCH (v:Disease{name: "上感"}) RETURN v;
   MATCH (v:Disease) where v.Disease.name=="上感" RETURN v;
   
   # 匹配连接的点
   # v1--v2表示v1和v2之间的连接
   # v1-->v2表示v1到v2之间的连接，对于v1是出边，对于v2是入边
   # v1<--v2表示v2到v1之间的连接
   
   # -->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。
   MATCH (v:Disease{name:"急性上呼吸道感染"})-->(v2:Disease) RETURN v2.Disease.name AS Name;
   
   # 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。
   MATCH p=(v:Disease{name:"上感"})-->(v2) RETURN p;
   
   # 匹配边
   # 和点一样，用户可以用:<edge_type>表示模式中的 Edge type，例如-[e:follow]-
   MATCH (v:Disease{name:"流行性脑脊髓膜炎"})-[e:ClinicalManifestation]->(v2) RETURN e;
   MATCH (v:Disease{name:"流行性脑脊髓膜炎"})-[e:ClinicalManifestation{inStage:"初期"}]->(v2) RETURN e;
   

2. FIND PATH语句
   FIND PATH语句查找指定起始点和目的点之间的路径。
   参考：https://docs.nebula-graph.com.cn/3.1.0/3.ngql-guide/16.subgraph-and-path/2.find-path/

   # "急性上呼吸道感染" 到 "咽干" 的最短路径
   FIND SHORTEST PATH FROM "急性上呼吸道感染" TO "咽干" OVER * YIELD path AS p;
   

3. GET SUBGRAPH语句
   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。
   参考：https://docs.nebula-graph.com.cn/3.1.0/3.ngql-guide/16.subgraph-and-path/1.get-subgraph/

   # 查询从点急性上呼吸道感染开始、0~1 跳、所有Edge type的子图。
   GET SUBGRAPH 1 STEPS FROM "急性上呼吸道感染" YIELD VERTICES AS nodes, EDGES AS relationships
   
   # 查询从点急性上呼吸道感染开始、0~1 跳、DiseaseClassification类型的出边的子图。
   GET SUBGRAPH 1 STEPS FROM "急性上呼吸道感染" OUT DiseaseClassification YIELD VERTICES AS nodes, EDGES AS relationships;
   

Python接口

参考：https://github.com/vesoft-inc/nebula/tree/master/tests/tck/features/fetch