Support for Vector indexes

[mariusconjeaud]

Neo4j added a new type of index in version 5.11 : Vector index

It comes with a set of commands to query it.

But it is still in beta mode, so the set of commands are subject to change, so I suggest we hold off a bit before adding support for this new index type ; but happy to debate.

[CyrusOfEden]

I might just take a stab at this over the holidays. Any tips?

[mariusconjeaud]

So, the _install_node / _install_relationship are the ones where the magic happens (if a node has an index property, it will create an index.

A few tricks here though :

• We must pass an extra property to mention the type of index we want to create (so we create a vector and not the default range index)
• We must check that the Neo4j version is right to create vector indexes. There are utility methods and examples for this, like : if self.version_is_higher_than("5.7")

An underlying question is that we should provide a way to make neomodel query using vector indexes, since it's a specific syntax in Cypher (something like CALL db.index.vector.queryNodes) and returns a list of elements with a similarity score. So that would require a separate method I guess ?