Neo4j Type Provider

Why am I doing this?

One of the most awesomest things about F# is Type Providers . There are Type Providers for, like, everything. A while ago I found a Neo4j Type Provider built by Pete Bayne , who was kind of enough to help me a bit when I was having trouble getting the code to compile. I did end up making some small changes to get it to work, but sure enough, it does and has been very useful.

I will outline the changes I made, example usage, and some tests I wrote using the Type Provider.

The source code

You can get the original source code on Pete Bayne's BitBucket .

Read about it on this blog post .

Pete used Readify's Neo4jClient to query the database. This was great because I am familiar with that client and so I could follow the code pretty easily. Phew! I might actually understand what is going on.

At first I couldn't get it to compile, but I tweeted Pete and he said I should make sure that Neo4j was running. I did this, felt really dumb, and got a lot further. I was almost there. The next problem was syntax. Neo4j was telling me that the parens were required, like this:

Parentheses are required to identify nodes in patterns, i.e. (n) (line 1, column 7 (offset: 6)) "MATCH n RETURN n LIMIT 25"

So I made the following changes to the graph module.

The changes are on the left and the original is on the right.

I got it to compile. Now I can try using it. I was so excited!

Using the type provider

I cloned from Pete's repo on BitBucket and pushed it onto my Github. You can find tests using the Type Provider in my GraphIVR project . I will talk about how I used it in my GraphIVR project in my next post. Here I will give some examples of using the Type Provider alone.

First you need to instantiate the type like this.

[<Literal>] let ConnectionString = @"http://localhost:7474/db/data" //the db should be populated type IVRSchema = Haumohio.Neo4j.Schema< ConnectionString >

You can get at your graph's labels like this ( see my previous post on the IVR graph ).

let startLabel = IVRSchema.Labels.START

You can get at a label's property fields like this.

let endIdField = IVRSchema.Props.END.id

You can get at a relationship like this.

let successRelationship = IVRSchema.Rels.SUCCESS

You can get a node as an object like this.

let entryNode = IVRSchema.Proxies.ENTRY

Putting it all together you can do something like this to get a list of related nodes. In this case the path is from an entry node to the next entry node through the success relationship. Here I am using Neo4jClient.

type IVRSchema = Haumohio.Neo4j.Schema< ConnectionString > let db = new Neo4jClient.GraphClient(Uri(ConnectionString)) db.Connect() let data = db.Cypher .Match(sprintf "(s:%s)-[r:%s]->(e:%s)" IVRSchema.Labels.START IVRSchema.Rels.GOTO IVRSchema.Labels.ENTRY) .Return(fun (s:ICypherResultItem) (e:ICypherResultItem) -> (s.As<IVRSchema.Proxies.START>(), e.As<IVRSchema.Proxies.ENTRY>())) .Results let sNode, eNode = data |> Seq.head Thoughts

This is a nice way to work with your database's schema and it will naturally update as the source database changes.

I |> heart TypeProviders