英文:
How does "gds.graph.project" actually work in Neo4j?
问题
我是neo4j的初学者。
在参加neo4j在线课程-Neo4j图数据科学基础时，我对以下**"课程示例"**感到困惑。
课程示例
首先，创建图投影。
CALL gds.graph.project('proj',
['Person','Movie'],
{
ACTED_IN:{orientation:'UNDIRECTED'},
DIRECTED:{orientation:'UNDIRECTED'}
}
);
然后我们可以运行Dijkstra的最短路径算法。
MATCH (a:Actor)
WHERE a.name IN ['Kevin Bacon', 'Denzel Washington']
WITH collect(id(a)) AS nodeIds
CALL gds.shortestPath.dijkstra.stream('proj', {sourceNode:nodeIds[0], TargetNode:nodeIds[1]})
YIELD sourceNode, targetNode, path
RETURN gds.util.asNode(sourceNode).name AS sourceNodeName,
gds.util.asNode(targetNode).name AS targetNodeName,
nodes(path) as path;
问题
关于gds.graph.project，我理解它创建了原始图的子图（子集）。
然而，在创建这个子图时，没有带有Actor标签的节点。那么为什么在执行Dijkstra算法时可以执行MATCH (a:Actor)呢？
英文:
I'm a neo4j beginner.
While praticing in neo4j online course-Neo4j Graph Data Science Fundamentals, I'm confused about the following "Course Example".
Course Example
First, create the graph projection.
CALL gds.graph.project('proj',
['Person','Movie'],
{
ACTED_IN:{orientation:'UNDIRECTED'},
DIRECTED:{orientation:'UNDIRECTED'}
}
);
Then we can run Dijkstra’s shortest path.
MATCH (a:Actor)
WHERE a.name IN ['Kevin Bacon', 'Denzel Washington']
WITH collect(id(a)) AS nodeIds
CALL gds.shortestPath.dijkstra.stream('proj', {sourceNode:nodeIds[0], TargetNode:nodeIds[1]})
YIELD sourceNode, targetNode, path
RETURN gds.util.asNode(sourceNode).name AS sourceNodeName,
gds.util.asNode(targetNode).name AS targetNodeName,
nodes(path) as path;
Question
Regarding gds.graph.project my understanding is that it creates a subgraph (subset) from the original graph.
However, in the creation of this subgraph, there are no nodes with the Actor label. So why is it possible to execute MATCH (a:Actor) when performing the Dijkstra algorithm?
答案1
得分: 2
MATCH (a:Actor) 子句正在查询整个数据库，而不是 GDS 投影 ('proj')。只有以 gds. 开头的存储过程才能访问 GDS。
此外，一个节点可以有任意数量的标签。因此，一个 'Person' 节点也可以有 'Actor' 标签、'Director' 标签或者这三者的组合。
英文:
The MATCH (a:Actor) clause is querying the full database, not the GDS projection ('proj'). Only the procedures whose names start with gds. access the GDS.
Also, a node can have any number of labels. So, a Person node can also have the Actor label, or Director, or all 3.
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