apoc.nodes.collapse

Procedure APOC Core

apoc.nodes.collapse([nodes…],[{properties:'overwrite' or 'discard' or 'combine'}]) yield from, rel, to merge nodes onto first in list

Signature

apoc.nodes.collapse(nodes :: LIST? OF NODE?, config = {} :: MAP?) :: (from :: NODE?, rel :: RELATIONSHIP?, to :: NODE?)

Input parameters

Name	Type	Default
nodes	LIST? OF NODE?	null
config	MAP?	{}

Name

Type

Default

nodes

LIST? OF NODE?

null

config

MAP?

{}

Config parameters

The procedure support the following config parameters:

Table 1. Config parameters
name	type	default	description
properties	String	"discard"	how to handle properties on the nodes being collapse. The following values are supported: `overwrite` - if there is the same property in more node, in the new one will have the last relationship’s/node’s property value `discard` - if there is the same property in more node, the new one will have the first relationship’s/node’s property value `combine` - if there is the same property in more node, the new one a value’s array with all relationship’s/node’s values
mergeVirtualRels	Boolean	true	give the possibility to merge relationships with same type and direction.
selfRel	Boolean	false	give the possibility to create the self relationship.
countMerge	Boolean	true	give the possibility count all the Nodes/Relationships merged.
collapsedLabel	Boolean	false	give the possibility to add the label `:Collapsed` to the virtualNode.

Output parameters

Name	Type
from	NODE?
rel	RELATIONSHIP?
to	NODE?

Name

Type

from

NODE?

rel

RELATIONSHIP?

NODE?

Usage Examples

The examples in this section are based on the following sample graph:

MERGE (david:Person {name: "David"})
MERGE (john:Person {name: "John"})
MERGE (jennifer:Person {name: "Jennifer"})
MERGE (adam:Person {name: "Adam"})
MERGE (mark:Person {name: "Mark"})

MERGE (unitedStates:Country {name: "United States"})
MERGE (uk:Country {name: "United Kingdom"})

MERGE (david)-[:LIVES_IN]->(unitedStates)
MERGE (john)-[:LIVES_IN]->(unitedStates)
MERGE (jennifer)-[:LIVES_IN]->(unitedStates)

MERGE (adam)-[:LIVES_IN]->(uk)
MERGE (mark)-[:LIVES_IN]->(uk);

We can collapse the people living in the city to a single node, by running the following query:

MATCH (p:Person)-[:LIVES_IN]->(c:Country)
WITH c, collect(p) as subgraph
CALL apoc.nodes.collapse(subgraph,{properties:'combine'})
YIELD from, rel, to
RETURN from, rel, to;

Table 2. Results
from	rel	to
(:Person {name: ["David", "John", "Jennifer"], count: 3})	[:LIVES_IN {count: 2}]	(:Country {name: "United States"})
(:Person {name: ["Adam", "Mark"], count: 2})	[:LIVES_IN {count: 1}]	(:Country {name: "United Kingdom"})

More documentation of apoc.nodes.collapse