我一直在研究一个包含英国国家铁路时刻表的数据集，它们以文本格式为您提供每列火车的出发和到达时间。

例如，可以这样创建代表停止的节点：

CREATE (stop:Stop {arrival: "0802", departure: "0803H"})

该时间格式不是特别适合查询，因此我想添加另一个属性，该属性指示自一天开始以来的秒数。

因此，我们想向节点添加“ arrivalSecondsSinceStartOfDay”和“ departureSecondsSinceStartOfDay”属性。 我编写了以下查询来计算这些属性的值。

MATCH (stop:Stop)
UNWIND ["arrival", "departure"] AS keyWITH key,toInteger(substring(stop[key], 0, 2)) AS hours,          toInteger(substring(stop[key], 2, 2)) AS minutes,CASE WHEN substring(stop[key], 4,1) = "H" THEN 30 ELSE 0 END AS secondsWITH key, (hours * 60 * 60) + (minutes * 60) + seconds AS secondsSinceStartOfDayRETURN key + "SecondsSinceStartOfDay" AS newKey, secondsSinceStartOfDay

╒═══════════════════════════════╤══════════════════════╕
│newKey                         │secondsSinceStartOfDay│
╞═══════════════════════════════╪══════════════════════╡
│arrivalSecondsSinceStartOfDay  │28920                 │
├───────────────────────────────┼──────────────────────┤
│departureSecondsSinceStartOfDay│29010                 │
└───────────────────────────────┴──────────────────────┘

现在我们准备在“停止”节点上设置这些属性。

MATCH (stop:Stop2)
UNWIND ["arrival", "departure"] AS keyWITH stop,key,toInteger(substring(stop[key], 0, 2)) AS hours,          toInteger(substring(stop[key], 2, 2)) AS minutes,CASE WHEN substring(stop[key], 4,1) = "H" THEN 30 ELSE 0 END AS secondsWITH stop, key, (hours * 60 * 60) + (minutes * 60) + seconds AS secondsSinceStartOfDay
WITH stop, key + "SecondsSinceStartOfDay" AS newKey, secondsSinceStartOfDay
SET stop[newKey] = secondsSinceStartOfDay

Invalid input '[': expected an identifier character, whitespace, '{', node labels, a property map, a relationship pattern, '.', '(', '=' or "+=" (line 12, column 9 (offset: 447))
"SET stop[newKey] = secondsSinceStartOfDay"^

嗯，没有按预期工作！ 看起来我们还不能使用Cypher设置动态属性。

幸运的是，我的同事Michael Hunger和Neo4j社区一直在管理APOC程序库，并且该程序正是可以帮助我们的程序。

您需要下载适用于您的Neo4j版本的jar ，然后将其放在plugins目录中。 我正在使用Neo4j 3.1 Beta1，因此对我来说是这样的：

$ tree neo4j-enterprise-3.1.0-BETA1/plugins/neo4j-enterprise-3.1.0-BETA1/plugins/
└── apoc-3.1.0.1-all.jar0 directories, 1 file

完成之后，您将需要重新启动Neo4j，以便它可以采用我们添加的新过程。 完成后，执行以下查询以检查它们是否正确安装：

call dbms.procedures()
YIELD name
WITH name
WHERE name STARTS WITH "apoc"
RETURN COUNT(*)

╒════════╕
│COUNT(*)│
╞════════╡
│183     │
└────────┘

现在，我们准备在图中动态设置属性。 我们将使用的过程是apoc.create.setProperty ，很容易更新查询以使用它：

MATCH (stop:Stop)
UNWIND ["arrival", "departure"] AS keyWITH stop,key,toInteger(substring(stop[key], 0, 2)) AS hours,          toInteger(substring(stop[key], 2, 2)) AS minutes,CASE WHEN substring(stop[key], 4,1) = "H" THEN 30 ELSE 0 END AS secondsWITH stop, key, (hours * 60 * 60) + (minutes * 60) + seconds AS secondsSinceStartOfDay
WITH stop, key + "SecondsSinceStartOfDay" AS newKey, secondsSinceStartOfDay
CALL apoc.create.setProperty(stop, newKey, secondsSinceStartOfDay)

Query cannot conclude with CALL (must be RETURN or an update clause) (line 12, column 1 (offset: 439))
"CALL apoc.create.setProperty(stop, newKey, secondsSinceStartOfDay)"^

糟糕，我讲得太早了！ 我们需要产生过程的return列并返回它，或者只是返回一个计数来解决此问题：

MATCH (stop:Stop)
UNWIND ["arrival", "departure"] AS keyWITH stop,key,toInteger(substring(stop[key], 0, 2)) AS hours,          toInteger(substring(stop[key], 2, 2)) AS minutes,CASE WHEN substring(stop[key], 4,1) = "H" THEN 30 ELSE 0 END AS secondsWITH stop, key, (hours * 60 * 60) + (minutes * 60) + seconds AS secondsSinceStartOfDay
WITH stop, key + "SecondsSinceStartOfDay" AS newKey, secondsSinceStartOfDay
CALL apoc.create.setProperty(stop, newKey, secondsSinceStartOfDay)
YIELD node
RETURN COUNT(*)

╒════════╕
│COUNT(*)│
╞════════╡
│2       │
└────────┘

就是这样，我们现在可以在查询中动态设置属性。

翻译自: https://www.javacodegeeks.com/2016/10/neo4j-dynamically-add-propertyset-dynamic-property.html