Variable edge properties

[kasthuri]

I am constructing a graph in Neo4j like this. First, I create the nodes with an array property. Then I check if any two nodes have common elements between the arrays (using apoc intersection call) and if so I create a relationship between the nodes.

For example, lets say, nodes N and M has arrays S = [A, B, C] and T = [A, B, D] as properties, respectively, then N and M will have a relationship r between them, since they share the common elements A, B .

Now, each of the array elements also has properties associated with them and I want to populate the edge with common elements together with their properties. That is, we have A.name, A.age, B.name, B.age associated with them. Note that A and B are variables themselves. That is, A could be Doctor X and B could be Doctor Y .

How do I annotate the edges with the variable name and their properties so that I can query the database using the variable name? I somehow need to preserve the association between elements and their properties within the edges as edge properties.

How do I do this? Thank you very much.

[Joel]

You can add properties to edges and query by them, but be aware that you can't use the regular indexes on relationship properties, but it is possible to add a full text search.

Neo4j Graph Database Platform

Indexes for full-text search - Neo4j Cypher Manual

This section describes how to use full-text indexes, to enable full-text search.

That said, at times I do use unindexed edge properties in queries, but always in combination with label and node property filters. Here is a very simple example (note: you can create both nodes and relationship with properties in one cypher command, but this is may be easier to follow)

// create node A
CREATE (:NODE {name:'A'});

// create node B
CREATE (:NODE {name:'B'});'

// check that they were created
MATCH (x :NODE {name:'A'})
MATCH (y :NODE {name:'B'})
RETURN x, y

// create relationship, and set value (using set instead of inline)
// (there are two ways to relationship properties, see reference below for inline style)
MATCH (x :NODE {name:'A'})
MATCH (y :NODE {name:'B'})
CREATE (x)-[r:KNOWS]->(y)
SET r.relationship='friends'

// query relationship property for value and return a path
MATCH t=(:NODE)-[r]-(:NODE)
WHERE r.relationship='friends'
RETURN t

// same query, but return nodes and relationship
MATCH (x:NODE)-[r]-(y:NODE)
WHERE r.relationship='friends'
RETURN x ,r, y

Reference:

Neo4j Graph Database Platform

CREATE - Neo4j Cypher Manual

The `CREATE` clause is used to create nodes and relationships.

[kasthuri]

@Joel Thanks. Yes, I realize we can do that. This is not what I meant. Each element in the array has properties that need to be set and there is a variable number of them.

[ameyasoft]

It's not clear how you stored array elements and their associated properties. Please share the Cypher query you are using in your test.

[kasthuri]

@ameyasoft What do you mean? You mean how I create the nodes? There are no different from how we usually do, using MERGE.

[Joel]

A note of clarification, Neo4j allows properties to be added adhoc to any node or relationship, they do not need to be the same, this is schema-less, so any given node/relationships can have any property, or not have it. Just be aware that you may want/need to check if a property exists, before checking if the property has a specific value, otherwise the query results may not be what you expect.

If you want to dynamically create a series of properties on the fly it seems likely you'll need to construct the CREATE/MERGE query on the fly as a string, then execute it. There is an APOC function that enables this, (if you aren't already writing code in a language like java, python)

Neo4j Graph Database Platform

apoc.cypher.run - APOC Documentation

This section contains reference documentation for the apoc.cypher.run procedure.

There are many ways to unwind an array, in neo4j/cypher or outside, then add properties, since the property name is dynamic I think you will need to create cypher strings, then execute them, but there might be another clever way around it? (interested to know if there is)

[kasthuri]

@Joel again, thanks. Yes, I am creating relationships and their properties dynamically through apoc. What I am looking for is preserving an association between two properties without introducing any pseudo node or relationship.