Saturday, April 22, 2017

How to create a linked list in neo4j?

Having a "Post" nodes that have "FILED_IN" relations to "Topic" model. We can retrieve all posts filed under the Topic using;

MATCH (p:Post)-[FILED_IN]->(t:Topic) return p

But what if we need to retrieve next post. It will be convenient to have a relation to the next post. We can add this relation anytime using the following Cypher.

MATCH (p:post)-[FILED_IN]->(t:Topic)
ORDER BY p.timestamp
UNWIND RANGE(0,LENGTH(posts) - 2) as idx 
WITH posts[idx] AS p1, posts[idx+1] AS p2
MERGE (p1)-[:NEXT]->(p2)


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Fun With Haxl (Part 1)

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