Path Manipulation
The functions in this section can be used to create, combine and split paths.
Function Overview
The available functions are described below:
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Examples
The examples in this section are based on the following sample graph:
MERGE (manUtd:Club {name: 'Man Utd'})
MERGE (juventus:Club {name: 'Juventus'})
MERGE (flamengo:Club {name: 'Flamengo'})
MERGE (premierLeague:League {name: 'Premier League'})
MERGE (serieA:League {name: 'Serie A'})
MERGE (brasileirao:League {name: 'Brasileirão'})
MERGE (england:Country {name: 'England'})
MERGE (brazil:Country {name: 'Brazil'})
MERGE (uefa:Confederation {name: 'UEFA'})
MERGE (manUtd)-[:IN_LEAGUE]->(premierLeague)
MERGE (premierLeague)-[:IN_COUNTRY]->(england)
MERGE (england)-[:IN_CONFEDERATION]->(uefa)
MERGE (juventus)-[:IN_LEAGUE]->(serieA)
MERGE (flamengo)-[:IN_LEAGUE]->(brasileirao)
MERGE (brasileirao)-[:IN_COUNTRY]->(brazil);
The apoc.path.create
function creates paths from a start node and a list of relationhips.
One use case for this function is combining relationships from OPTIONAL MATCH
clauses.
OPTIONAL MATCH
clausesMATCH (club:Club)
OPTIONAL MATCH (club)-[inLeague:IN_LEAGUE]->(league)
OPTIONAL MATCH (league)-[inCountry:IN_COUNTRY]->(country)
OPTIONAL MATCH (country)-[inConfederation:IN_CONFEDERATION]->(confederation)
RETURN club.name, apoc.path.create(club, [inLeague, inCountry, inConfederation]) AS path
ORDER BY length(path);
club.name | path |
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"Juventus" |
(:Club {name: "Juventus"})-[:IN_LEAGUE]→(:League {name: "Serie A"}) |
"Flamengo" |
(:Club {name: "Flamengo"})-[:IN_LEAGUE]→(:League {name: "Brasileirão"})-[:IN_COUNTRY]→(:Country {name: "Brazil"}) |
"Man Utd" |
(:Club {name: "Man Utd"})-[:IN_LEAGUE]→(:League {name: "Premier League"})-[:IN_COUNTRY]→(:Country {name: "England"})-[:IN_CONFEDERATION]→(:Confederation {name: "UEFA"}) |
If we want to create a path from a query that contains two OPTIONAL MATCH
clauses, we can instead use the apoc.path.combine
function.
(club)-[:IN_LEAGUE]→(league)
and (league)-[:IN_COUNTRY]→(country)
pathsMATCH (club:Club)
OPTIONAL MATCH path1 = (club)-[:IN_LEAGUE]->(league)
OPTIONAL MATCH path2 = (league)-[:IN_COUNTRY]->(country)
RETURN club.name, apoc.path.combine(path1, path2) AS path
ORDER BY length(path);
club.name | path |
---|---|
"Juventus" |
(:Club {name: "Juventus"})-[:IN_LEAGUE]→(:League {name: "Serie A"}) |
"Man Utd" |
(:Club {name: "Man Utd"})-[:IN_LEAGUE]→(:League {name: "Premier League"})-[:IN_COUNTRY]→(:Country {name: "England"}) |
"Flamengo" |
(:Club {name: "Flamengo"})-[:IN_LEAGUE]→(:League {name: "Brasileirão"})-[:IN_COUNTRY]→(:Country {name: "Brazil"}) |
The apoc.path.slice
function returns a subset of a path starting from a specified offset for a specified number of elements.
MATCH (club:Club)
OPTIONAL MATCH path1 = (club)-[:IN_LEAGUE]->(league)
OPTIONAL MATCH path2 = (league)-[:IN_COUNTRY]->(country)
WITH apoc.path.combine(path1, path2) AS path
RETURN apoc.path.slice(path, 1, 1);
apoc.path.slice(path, 1, 1) |
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(:League {name: "Premier League"})-[:IN_COUNTRY]→(:Country {name: "England"}) |
(:League {name: "Serie A"}) |
(:League {name: "Brasileirão"})-[:IN_COUNTRY]→(:Country {name: "Brazil"}) |
The apoc.path.elements
function converts a path into a list of nodes and relationships.
(club)-[:IN_LEAGUE]→(league)-[:IN_COUNTRY]→(country)
pathMATCH path = (club:Club)-[:IN_LEAGUE]->(league)-[:IN_COUNTRY]->(country)
RETURN path, apoc.path.elements(path);
path | apoc.path.elements(path) |
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(:Club {name: "Man Utd"})-[:IN_LEAGUE]→(:League {name: "Premier League"})-[:IN_COUNTRY]→(:Country {name: "England"}) |
[(:Club {name: "Man Utd"}), [:IN_LEAGUE], (:League {name: "Premier League"}), [:IN_COUNTRY], (:Country {name: "England"})] |
(:Club {name: "Flamengo"})-[:IN_LEAGUE]→(:League {name: "Brasileirão"})-[:IN_COUNTRY]→(:Country {name: "Brazil"}) |
[(:Club {name: "Flamengo"}), [:IN_LEAGUE], (:League {name: "Brasileirão"}), [:IN_COUNTRY], (:Country {name: "Brazil"})] |
We can use this function to return a stream of triples representing the nodes and relationships contained in paths.
MATCH path = (club:Club)
OPTIONAL MATCH path1 = (club)-[:IN_LEAGUE]->(league)
OPTIONAL MATCH path2 = (league)-[:IN_COUNTRY]->(country)
WITH apoc.path.combine(path1, path2) AS path
WITH apoc.path.elements(path) AS elements
UNWIND range(0, size(elements)-2) AS index
WITH elements, index
WHERE index %2 = 0
RETURN elements[index] AS subject, elements[index+1] AS predicate, elements[index+2] AS object;
subject | predicate | object |
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(:Club {name: "Man Utd"}) |
[:IN_LEAGUE] |
(:League {name: "Premier League"}) |
(:League {name: "Premier League"}) |
[:IN_COUNTRY] |
(:Country {name: "England"}) |
(:Club {name: "Juventus"}) |
[:IN_LEAGUE] |
(:League {name: "Serie A"}) |
(:Club {name: "Flamengo"}) |
[:IN_LEAGUE] |
(:League {name: "Brasileirão"}) |
(:League {name: "Brasileirão"}) |
[:IN_COUNTRY] |
(:Country {name: "Brazil"}) |