最近接手了一个数据知识图谱展示的项目，其中图数据库用的是 neo4j，前端可视化组件用的是 ECharts 3。上线后用户反应图谱查询较慢，故分析了一下项目的代码，发现了一个编码思路的问题。
一般图的可视化组件，如 ECharts，Cytoscape.js 等，接收的图数据格式是按照节点和关系来分类的，类似：
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/*
nodes:id,label,properties
edges:id,source,target,title
*/
data = {
nodes: nodes,
edges: edges
};
但是我们代码里后台查询出来的结果是按照节点的形式，然后再通过节点中遍历出关系信息，组装成上文的 nodes\edges 格式的 json 返回到前端。根据一番测试，发现图数据库查询耗时都在毫秒级，瓶颈就在这个 json 组装上，通常耗费2s+。
后来通过查询资料，发现 neo4j 自带提供 graph format 格式的返回，专门用于可视化组件。不过此种方式仅在 HTTP API 中提供:
发送请求：
- POST http://localhost:7474/db/data/transaction/commit
- Accept: application/json; charset=UTF-8
- Content-Type: application/json
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{
"statements" : [ {
"statement" : "CREATE ( bike:Bike { weight: 10 } ) CREATE ( frontWheel:Wheel { spokes: 3 } ) CREATE ( backWheel:Wheel { spokes: 32 } ) CREATE p1 = (bike)-[:HAS { position: 1 } ]->(frontWheel) CREATE p2 = (bike)-[:HAS { position: 2 } ]->(backWheel) RETURN bike, p1, p2",
"resultDataContents" : [ "row", "graph" ]
} ]
}
返回结果：
- 200: OK
- Content-Type: application/json
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{
"results" : [ {
"columns" : [ "bike", "p1", "p2" ],
"data" : [ {
"row" : [ {
"weight" : 10
}, [ {
"weight" : 10
}, {
"position" : 1
}, {
"spokes" : 3
} ], [ {
"weight" : 10
}, {
"position" : 2
}, {
"spokes" : 32
} ] ],
"meta" : [ {
"id" : 7,
"type" : "node",
"deleted" : false
}, [ {
"id" : 7,
"type" : "node",
"deleted" : false
}, {
"id" : 0,
"type" : "relationship",
"deleted" : false
}, {
"id" : 8,
"type" : "node",
"deleted" : false
} ], [ {
"id" : 7,
"type" : "node",
"deleted" : false
}, {
"id" : 1,
"type" : "relationship",
"deleted" : false
}, {
"id" : 9,
"type" : "node",
"deleted" : false
} ] ],
"graph" : {
"nodes" : [ {
"id" : "7",
"labels" : [ "Bike" ],
"properties" : {
"weight" : 10
}
}, {
"id" : "8",
"labels" : [ "Wheel" ],
"properties" : {
"spokes" : 3
}
}, {
"id" : "9",
"labels" : [ "Wheel" ],
"properties" : {
"spokes" : 32
}
} ],
"relationships" : [ {
"id" : "0",
"type" : "HAS",
"startNode" : "7",
"endNode" : "8",
"properties" : {
"position" : 1
}
}, {
"id" : "1",
"type" : "HAS",
"startNode" : "7",
"endNode" : "9",
"properties" : {
"position" : 2
}
} ]
}
} ]
} ],
"errors" : [ ]
}
可以看到 graph 节点中的数据格式符合我们可视化组件的要求。
通过这次改造，解决了图谱展示慢的问题，如果大家也有图谱展示的要求，不妨试试这种方式，欢迎交流～
参考
- https://neo4j.com/docs/http-api/current/actions/return-results-in-graph-format/
本文为[原创]文章，转载请标明出处。
本文链接：https://weyunx.com/2019/05/02/neo4j-visualization/
本文出自微云的技术博客
