Neo4j / Cypher-从匹配结果中获取随机节点

Question

我需要播种Neo4j数据库。假设添加了Person个节点后，我需要它们来编写Book个。这是我到目前为止的内容：

MATCH (p:Person)
WITH ["Book 1", "Book 2", "Book 3", "Book 4", "Book 5"] AS titles
UNWIND titles AS title
CREATE (???)-[:CREATED]->(:Content { title: title, content: "Words..." })

我当时想用???中的一个随机人来填写p，该人在第一行中是MATCH。我该怎么办？

Answer 1

使用APOC程序，您可以使用功能从列表中选择随机项目。这是用法示例：

MATCH (p:Person)
WITH collect(p) as people
UNWIND ["Book 1", "Book 2", "Book 3", "Book 4", "Book 5"] AS title
WITH apoc.coll.randomItem(people) as person, title
CREATE (person)-[:CREATED]->(:Content { title: title, content: "Words..." })

Answer 2

如果您只想说5个不同的Person节点，而您不在乎它们是否是随机分布的，或者重复运行很可能会得到相同的节点，则可以使用此有效查询（因为它不需要获取所有Person个节点）：

MATCH (p:Person)
WITH p LIMIT 5
WITH COLLECT(p) AS ps, ["Book 1", "Book 2", "Book 3", "Book 4", "Book 5"] AS titles
UNWIND [i IN RANGE(0, SIZE(ps)-1) | {p: ps[i], title: titles[i]}] AS data
WITH data.p AS p, data.title AS title
MERGE (p)-[:CREATED]->(:Content {title: title, content: "Words..."})

请注意，如果要重新运行此查询，我将使用MERGE而不是CREATE，以避免产生重复的关系和节点。