neo4j中基于时间/日期的搜索 [英] Time/date based searches in neo4j

问题描述

在与neo4j玩耍时，出现了两个问题。目前有2种：

• 在搜索从节点X到节点的特定路径时如何限制关系/边是（RegEx？/通配符？）？例如，所有边都具有2个时间属性，开始和结束。我想找到在凌晨2点到凌晨3点之间发生的节点之间的路径。？


• 如何跟踪时间路径？假设有一辆汽车从 A驶向 B。该路线花费了一个小时，即从早上5点到早上6点。从 B到 C的下一个部分也花了一个小时，但是从早上7点到早上8点，因为驾驶员休息了一个小时。如何以仅允许逻辑上有效（时间）路径的方式查询neo4j。例如，这应该是有效的：

（布拉格）-[：DISTANCE {开始： 5 am ，end：'6 am'}]->（布尔诺），（Brno）-[：DISTANCE {开始：'7 am'，end：'9 am'}]->（Liberec）

而这个无效：

（布拉格）-[ ：DISTANCE {开始：'5 am'，结束：'6 am'}]->（布尔诺），（布尔诺）-[：DISTANCE {开始：'4 am'，结束：'6 am'}]-> ;（Liberec）

另一个示例，如下图所示：

  CREATE（a：BoxingMachine {title：'A'}）
 CREATE（b：BoxingMachine {title：'B'}）
 CREATE（c：BoxingMachine {title ：'C'}）
 CREATE（d：BoxingMachine {title：'D'}）
 CREATE（（a）-[：FORWARDED {start_time：'9:00 am'}]-> （b））
 CREATE（（a）-[：FORWARDED {start_time：'7:00 am'}]->（c））
 CREATE（（c）-[：FORWARDED {start_time ：'8:00 am'}]->（b））
创建（（a）-[：FORWARDED {start_time：'11：00 am'}]->（d））
创建（（d）-[：FORWARDED {start_time：'10：00 am'}]->（b））
  

我正在寻找从节点 A到节点 B的路径。忽略约束 start_time，此图中有3条可能的路径：

• 'A'-> ; ‘B’


• ‘A’-> ‘C’-> ‘B’


• ‘A’-> ‘D’-> 'B'

在这种情况下，我们仅考虑约束 start_time，剩下两个路径： / p>

• 'A'-> ‘B’


• ‘A’-> ‘C’-> ‘B’

是因为路径‘A’-> ‘D’-> ‘B’无效。在这种情况下，时间顺序是错误的。 Cooworker'A'在上午11点将包裹发送给Cooworker'D'，但一个小时前，cooworker将此特定包裹转发给了Cooworker'B'。巫婆是不可能的。

PS：有没有一种工具可以生成边缘为ASCII艺术的节点。对于控制台？ ：）

解决方案

首先，我建议您使用数字时间值而不是字符串。它将使Cypher变得更加简单和高效。同样，实际上，路径可能会跨越多天，因此仅提供一天中的某个时间会导致错误的结果。例如，您可能要使用时代时间。在我的答案中，我假设时间是数字。

此查询应仅返回有效的从A到B的路径：

  MATCH p =（a：BoxingMachine {title：'A'}）-[：FORWARDED *]->（b：BoxingMachine {title：'B'} ）
与p，RELENCESHIPS（p）会在
减少（s = true，i在范围内（1，SIZE（rels）-1）| 
时（rels [i] ）.start_time>（rels [i-1]）。start_time 
 THEN s 
 ELSE false END）
 RETURN p; 
  

REDUCE 子句负责检查

您可以使用此数据检查结果（使用简单的数字时间值，但纪元时间也可以）：

p>

 创建（a：BoxingMachine {title：'A'}）
创建（b：BoxingMachine {title：'B' }} 
创建（c：BoxingMachine {title：'C'}）
 CREATE（d：BoxingMachine {title：'D'}）
 CREATE（（a）-[：FORWARDED { start_time：9}]->（b））
 CREATE（（a）-[：FORWARDED {start_time：7}]->（c））
 CREATE（（c）-[： FORWARDED {start_time：8}]->（b））
 CREATE（（a）-[：FORWARDED {start_time：11}]->（d））
 CREATE（（d）- [：FORWARDED {start_time：10}]->（b））
  

while playing around with neo4j a couple of questions arisen. At present time there are 2 of them:

• How can I limit the relationships/edges while searching for a specific path from node X to node Y (RegEx?/Wildcard?)? For instance all edges have 2 time attributes, "begin" and "end". I would like to find a path between nodes which occured between 2 am and 3 am in the morning.?
• How can track a time path? Lets say a car drove from 'A' to 'B'. The route took one hour, namely from 5 am to 6 am. The next section, from 'B' to 'C' took as well one hour but from 7 am to 8 am because the driver took a one hour rest. How can I query neo4j in the way that only logically valid (time) paths are allowed. For instance this should be valid:

(Prague) -[:DISTANCE {begin: '5 am', end: '6 am'}]->(Brno), (Brno) -[:DISTANCE {begin: '7 am', end: '9 am'}]->(Liberec)

whereas this one shall be invalid:

(Prague) -[:DISTANCE {begin: '5 am', end: '6 am'}]->(Brno), (Brno) -[:DISTANCE {begin: '4 am', end: '6 am'}]->(Liberec)

Another example, given is the following graph:

CREATE (a:BoxingMachine {title: 'A'})
CREATE (b:BoxingMachine {title: 'B'})
CREATE (c:BoxingMachine {title: 'C'})
CREATE (d:BoxingMachine {title: 'D'})
CREATE ((a)-[:FORWARDED {start_time:  '9:00 am'}]->(b))
CREATE ((a)-[:FORWARDED {start_time:  '7:00 am'}]->(c))
CREATE ((c)-[:FORWARDED {start_time:  '8:00 am'}]->(b))
CREATE ((a)-[:FORWARDED {start_time: '11:00 am'}]->(d))
CREATE ((d)-[:FORWARDED {start_time: '10:00 am'}]->(b))

I am looking for paths from node 'A' to node 'B'. Ignoring the constraint "start_time", we have 3 possible paths in this graph:

• 'A' --> 'B'
• 'A' --> 'C' --> 'B'
• 'A' --> 'D' --> 'B'

In the case we consider the constraint "start_time" only, two paths left:

• 'A' --> 'B'
• 'A' --> 'C' --> 'B'

because the path 'A' --> 'D' --> 'B' is invalid. In this case the chronology is wrong. Cooworker 'A' send a package to cooworker 'D' at 11am but cooworker forwarded this particular package to cooworker 'B' a hour earlier. Witch is impossible.

PS: Is there a tool to generate the nodes with there edges as ASCII art resp. for the console? :)

解决方案

First, I would advise that you use a numeric time value instead of a string. It would make the Cypher a lot simpler and efficient. Also, practically speaking, paths can span multiple days, so just providing a time of day will lead to wrong results. For instance, you may want to use epoch time. In my answer, I assume that the times are numeric.

This query should only return paths from A to B that are valid:

MATCH p=(a:BoxingMachine{title: 'A'})-[:FORWARDED*]->(b:BoxingMachine{title: 'B'})
WITH p, RELATIONSHIPS(p) AS rels
WHERE REDUCE(s = true, i IN RANGE(1, SIZE(rels)-1) |
  CASE WHEN (rels[i]).start_time > (rels[i-1]).start_time
  THEN s
  ELSE false END)
RETURN p;

The REDUCE clause is responsible for checking that the start times in a candidate path make sense.

You can check the results using this data (with simple numeric time values, but epoch time would also work):

CREATE (a:BoxingMachine {title: 'A'}) 
CREATE (b:BoxingMachine {title: 'B'}) 
CREATE (c:BoxingMachine {title: 'C'}) 
CREATE (d:BoxingMachine {title: 'D'}) 
CREATE ((a)-[:FORWARDED {start_time:  9}]->(b)) 
CREATE ((a)-[:FORWARDED {start_time:  7}]->(c)) 
CREATE ((c)-[:FORWARDED {start_time:  8}]->(b)) 
CREATE ((a)-[:FORWARDED {start_time: 11}]->(d)) 
CREATE ((d)-[:FORWARDED {start_time: 10}]->(b))

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