Issue 653: add support for merging virtual nodes / rels

[vga91]

Added CALL apoc.merge.vNodes(...) and CALL apoc.merge.vRelationships(...)

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Resolve the Issue 1615 as well.
This one, cannot be solved by creating virtual entities in fabric subquery, because after that, throws an exception (Node with id (-number) not found).
I think because there is some native problem with the subquery, indeed executing the following query return an empty map:

UNWIND fabric.graphIds() AS graphId
CALL {
USE fabric.graph(x)
MATCH (m:Movie {title: 'The Matrix'})
RETURN m
}
RETURN properties(m)

so we can execute this query:

UNWIND fabric.graphIds() AS graphId
CALL {
USE fabric.graph(graphId)
MATCH g = (m:Movie {title: 'The Matrix'})<-[r]-(p:Person)
return labels(m) as lbl_movie, properties(m) as props_movie,
labels(p) as lbl_person, properties(p) as props_person,
type(r) as type_r, properties(r) as props_r
}
WITH apoc.create.vNode(lbl_movie, props_movie) as mV, 
    apoc.create.vNode(lbl_person, props_person) as pV, type_r, props_r // v nodes creation
WITH apoc.merge.vNodes(mV)[0] as start, collect([type_r, props_r, pV]) AS rows // merge movie v node
UNWIND rows as row
RETURN start, apoc.create.vRelationship(start, row[0], row[1], row[2]) as rel, row[2] as end// v rel creation

[conker84]

Questa dobbiamo provarla con una aggregate function