Cypher / Neo4j：如何匹配与n个“连续”节点相关的节点

Question

I'm trying to match listing availabilities in my graph (Airbnb-like).

• The graph has 1 node per date, and consecutive days are linked by a NEXT_DAY edge.
• Listings are linked to day nodes by an AVAILABLE edge (if they are available)

I'm trying to write a query which returns all listings which are available from start_date to end_date.

I know the following FOREACH syntax is incorrect but I may help giving the general idea:

MATCH period=(a)-[:NEXT_DAY*]->(c)
WHERE a.date="2013-01-20" AND c.date="2013-01-24"

MATCH (listing:Listing)-[:AVAILABLE]->(d:Date)
FOREACH (d IN nodes(period))

RETURN listing

Bonus question: How could I proceed if I wanted to score listings proportionally to their availability match with the query (eg 100% if the listing is available during the whole period, 50% if it is only available half of the period) ?

Thanks in advance :)

Benjamin

Answer 1

You can use UNWIND to get get the nodes from your date path and MATCH them to Listing .

MATCH period=(a)-[:NEXT_DAY*]->(c)
WHERE a.date="2013-01-20" AND c.date="2013-01-24"

// UNWIND gets a collection of ndoes and transforms them to single/matchable nodes
UNWIND nodes(period) as nodes_in_period
MATCH (nodes_in_period)<-[:AVAILABLE]-(listing:Listing)

RETURN listing

And for the bonus question: If I get it right, you can count the number of AVAILABLE relationships from Listing to Date and compare it to the number of Date nodes in your period. OPTIONAL MATCH might help:

MATCH period=(a)-[:NEXT_DAY*]->(c)
WHERE a.date="2013-01-20" AND c.date="2013-01-24"
UNWIND nodes(period) as nodes_in_period

OPTIONAL MATCH (nodes_in_period)<-[a:AVAILABLE]-(listing:Listing)

// return the listing, the number of available relationships 
// and the number of days in period
RETURN listing, count(a), count(nodes_in_period)