How to allow increments to a value instead of replacing?

[joshbartley]

I'm trying to count unique events that occur based off a key. Redis has a StringIncrement function, but I'm trying to use a local KV store and tried to setup a quick POC with FASTER. Code below.

    public class SimpleFunctions2 : FunctionsBase<string, long, long, long, Empty>
    {
        public override bool InPlaceUpdater(ref string key, ref long input, ref long value, ref long output, ref RMWInfo rmwInfo)
        { 
            Interlocked.Add(ref input, value);
            return true;
        }

        public override bool InitialUpdater(ref string key, ref long input, ref long value, ref long output, ref RMWInfo rmwInfo)
        {
            value = input;
            return true;
        } 
        public override bool CopyUpdater(ref string key, ref long input, ref long oldValue, ref long newValue, ref long output, ref RMWInfo rmwInfo)
        {
            newValue = oldValue + input;
            return true;
        } 
    }

            using var settings = new FasterKVSettings<string,long>(System.IO.Path.GetDirectoryName(Environment.ProcessPath));
            using var store = new FasterKV<string,long>(settings);
            using var session = store.NewSession(new SimpleFunctions2());

When I do a session.Upsert(ref key, ref value); or session.RMW(ref key, ref value); the value doesn't change. I'm sure it's the SimpleFunctions2 class, though I have no idea why and I'm just stuck. I tried the examples but the learning curve is steep. How can I set this up to increment a value on each operation?