How to create unique constraint involving multiple properties in Neo4J

Question

I know I can create a unique constraint on a single property with Cypher like CREATE CONSTRAINT ON (p:Person) ASSERT p.name IS UNIQUE. But I was wondering whether it is possible to create a unique constraint which involves multiple properties. If so, how?

Answer 1

neo4j (2.0.1) does not currently support a uniqueness constraint that covers multiple properties simultaneously.

However, I can think of a workaround that might be acceptable, depending on your use cases. Let's say you want properties a, b, and c to be unique as a group. You can add an extra property, d, that concatenates the stringified values of a, b, and c, using appropriate delimiter(s) to separate the substrings (such that, for example, the a/b delimiter is a character that never appears in a or b). You can then create a uniqueness constraint on d.

[UPDATE]

Neo4j 3.3 added support for uniqueness constraints that cover multiple properties, via node key constraints. However, this feature is only available in the Enterprise Edition.

Answer 2

As of neo4j version 3.3 there is a constraint called NODE KEY which can be used for uniqueness across multiple properties.

From the documentation:

To create a Node Key ensuring that all nodes with a particular label have a set of defined properties whose combined value is unique, and where all properties in the set are present

Example Query

CREATE CONSTRAINT ON (n:Person) ASSERT (n.firstname, n.surname) IS NODE KEY

Answer 3

As of now, neo4j(v3.0.3) still does not support unique constraint with multiple properties. The reason behind this is: When a unique constraint is created it also creates an index on it and as indexes only allow one property, thus constraints can only be applied on one index.