Funnels and RethinkDB - rethinkdb

Question

I have some steps saved in RethinkDB like this :
{
date: "Sat Feb 06 2015 00:00:00 GMT+00:00",
step: 1
},
{
date: "Sat Feb 06 2015 11:11:11 GMT+00:00",
step: 3
},
{
date: "Sat Feb 06 2015 22:22:22 GMT+00:00",
step: 2
}
I'd like to count the number of steps done in order 1, 2, 3.
So for this example, I'd like to get something like this :
{
step_1: 1,
step_2: 1,
step_3: 0
}
I have seen a step 1, so step_1 is 1
I have seen a step 2, and have seen a step 1 before, so step_2 is 1
I have seen a step 3, but I haven't seen a step 2 before, so step_3 is 0
I've tried a lot of things but didn't find a way to do it and actually I'm not really sure it's possible with RethinkDB.
Any of you have an idea for me ?
Thanks,
Adrien

Answer 1

As a preface: this really abuses the r.js term, and so is always going to be a bit slow. So this solution is not really great for production services. Unless someone comes up with a better answer (i.e.: all ReQL) it would be better to do this mostly client-side, possibly using a group and min to pre-digest some of this.
A couple of us really think that there is an answer, and mine uses reduce with a JavaScript function for the main bit. Unfortunately in working on this answer I found a bug that crashes our server, so for the moment my answer is slightly untested, and not recommended, but the in-progres version might give you the start of an answer:
r.table('alpha').reduce(r.js('''(
function(left, right) {
var returnValue = [];
var sources = [left, right];
for (var i in sources) {
var source = sources[i];
if (source.date) {
if (!returnValue[source.step] || returnValue[source.step] > source.date) {
returnValue[source.step] = source.date;
}
} else {
for (i in source) {
if (!returnValue[i] || returnValue[i] > source(key)) {
returnValue[i] = source(key);
}
}
}
}
return returnValue;
})''')).map(r.js('''(
function (row) {
var allValid = true;
var lastDate = 0;
var returnValue = [];
for (i in row) {
var afterLast = row[i] && row[i] > lastDate && allValid;
allValid = afterLast == true;
returnValue.push(afterLast);
lastDate = row[i];
}
}
})''')).run()