Neo4j查询性能调优不明 [英] Neo4j Query Performance tuning Undestanding

问题描述

我正在尝试优化Neo4j中的查询性能.我创建了唯一索引，查询执行得很好.但是Neo4j Web控制台中显示的查询性能数字显示为" 0个估计行"和" 0个数据库命中".

但实际上，我是通过一种关系获得结果的.

我的查询:

Match (a:Person{id:"1234"})-[r:Employed_by]->(b:Organization(id:"abcd")) RETURN r

此查询返回我一个亲戚.

但是当我使用Profile检查同一查询时，它显示为"0个估计行"和"0个数据库命中".

这是什么意思?请详细说明结果.

estimated rows的数量仅是在执行查询之前用于指导成本计划员的粗略估计.它经常会与操作获得的实际行数不完全匹配.

如果不需要访问数据库中的任何数据来执行该操作(即，如果该操作所需的所有数据已经​​在内存中可用)，则操作的db hits编号将为零.

I am trying to optimize the query performance in my Neo4j. I have created the Unique indexes and the query is performing pretty good. But the query performance figure shown in the Neo4j web console shows as "0 estimated rows" and "0 db hits".

But in real, I am getting the result with one relationship.

My query:

Match (a:Person{id:"1234"})-[r:Employed_by]->(b:Organization(id:"abcd")) RETURN r

This query returns me a relationship.

But when I am checking the same query with Profile, it is showing like "0 estimated rows" and "0 db hits".

What does this mean? Please elaborate the result.

解决方案

The number of estimated rows is only a rough estimate used to guide the cost planner before the query is executed; it will frequently not exactly match the actual number of rows obtained by an operation.

An operation's number of db hits will be zero if there is no need to access any data from the DB to perform the operation (i.e., if all the data needed by the operation is already available in memory).

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