记录Neo4j的limit踩坑

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已于 2022-09-22 13:58:36 修改 · 1.6k 阅读

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#知识图谱 #人工智能

于 2021-10-22 16:52:49 首次发布

本文探讨了在Neo4j中使用limit关键字对层级查询性能的影响，发现limit并非针对节点或关系，而是影响返回数据集的分页，案例揭示了查询深度和结果数量的关系，并提供了解决初次使用者疑问的实践建议。

最近完成了一个项目使用了Neo4j做节点及关系相关图谱功能，在这里记录一下里面使用limit的问题。

需求是这样的，使用neo4j做向下的层级查询，当前节点为中心节点，向下查询2级、3级、4级这样的需求。但是发现当查询4层的时候，比查询3层响应的节点及关系要少。因初次使用neo4j，不知道具体原因，在网上找了很多，没有找到具体原因，只有把cql打印出来。


MATCH p=(n:`39` {id: '测试'})-[:`30`|:`31`|:`89`|:`90`|:`91`*0..4]-(m)
WHERE  any(x in labels(m) WHERE x in ["29","32","33","34","35","36","37","38","39","40","41","42","43","44","45","46","47","48","49","50","51","52","53","54","55","56","57","58","59","60","61","62","63","64","65","66","67","68","69","70","71","72","73","74","75","76","77","78","79","80"]) 
RETURN DISTINCT p
SKIP 0
limit 1000

自己手动一个个条件去掉执行，发现问题，出在limit 1000。这里的limit不是针对节点也不是针对关系。而是针对响应查询出来的数据集进行分页。例如分页8如下响应

MATCH p=(n:`29` {id: "测试"})-[:`30`|:`31`|:`89`|:`90`|:`91`*0..2]-(m)
WHERE  any(x in labels(m) WHERE x in ["29","32","33","34","35","36","37","38","39","40","41","42","43","44","45","46","47","48","49","50","51","52","53","54","55","56","57","58