如何在Node.js中使用Neo4j GraphQL OGM按节点标签动态过滤数据

我在基于Node.js的应用中使用@neo4j/graphql-ogm，想要根据额外的节点标签动态过滤数据。我尝试用下面的代码实现，但没能生效：
const [brands] = await Brand.find({labels: { _in: nodeLabels }});

完整代码片段如下：

const express = require('express');
const { ApolloServer, gql } = require('apollo-server-express');
const { Neo4jGraphQL } = require('@neo4j/graphql');
const neo4j = require('neo4j-driver');
const { OGM, cypher } = require("@neo4j/graphql-ogm");


// Connect to Neo4j database
const driver = neo4j.driver(
    'neo4j+s://localhost:80',
    neo4j.auth.basic('abc', 'abc')
);


// Define GraphQL schema
const typeDefs = gql`
  type Brand {
    name: String!
    url: String
    # Add fields for other node labels here
  }

  type Query {
    brands(nodeLabels: [String!]!): [Brand!]!
  }
`;


// Initialize OGM (Object-Graph Mapping) for Neo4j
const ogm = new OGM({ typeDefs, driver });
const session = driver.session();

// Create resolvers
const resolvers = {
  Query: {
    brands: async (_parent, { nodeLabels }) => {

    await ogm.init();
    const Brand = ogm.model("Brand");

    const [brands] = await Brand.find({labels: { _in: nodeLabels }});
    console.log([brands]);
    return [brands];
    }
  }
};

// Create an ApolloServer instance with Neo4jGraphQL
const server = new ApolloServer({
  typeDefs,
  resolvers,
  context: ({ req }) => ({ req, cypher: ogm }),
});

/**
 * Main program
 * 
 * @returns {boolean} success status
 */
const main = async () => {
    await server.start();
    const app = express();
    server.applyMiddleware({ app });
    
    // Start the server
    const PORT = process.env.PORT || 4000;
    app.listen(PORT, () => {
      console.log(`Server running on http://localhost:${PORT}${server.graphqlPath}`);
    });
};


(async () => {
    await main();
})();

OGM的find方法不支持直接通过labels参数过滤，要实现基于额外标签的动态过滤，需使用自定义Cypher查询。

修改Resolver逻辑 #

将brands查询的Resolver替换为以下代码：

brands: async (_parent, { nodeLabels }) => {
  const session = driver.session();
  try {
    // 匹配带有Brand标签且包含所有传入额外标签的节点
    const cypherQuery = `
      MATCH (b:Brand)
      WHERE ALL(label IN $nodeLabels WHERE label IN labels(b))
      RETURN b { .* } AS brand
    `;
    const result = await session.run(cypherQuery, { nodeLabels });
    return result.records.map(record => record.get('brand'));
  } finally {
    // 务必关闭会话释放资源
    await session.close();
  }
}

核心逻辑说明 #

• labels(b)函数获取节点b的所有标签列表
• ALL(label IN $nodeLabels WHERE label IN labels(b))确保传入的所有标签都存在于目标节点上；若需要匹配任意传入标签，将ALL替换为ANY即可
• 通过b { .* }将节点属性映射为对象返回，符合GraphQL类型定义

优化初始化逻辑 #

原代码中每次Resolver调用都执行ogm.init()是冗余的，将初始化移到main函数中，全局执行一次：

const main = async () => {
    await ogm.init(); // 全局初始化OGM
    await server.start();
    const app = express();
    server.applyMiddleware({ app });
    
    const PORT = process.env.PORT || 4000;
    app.listen(PORT, () => {
      console.log(`Server running on http://localhost:${PORT}${server.graphqlPath}`);
    });
};

内容的提问来源于stack exchange，提问作者Tushar Narang