Returning MAX() and MIN() in one query - rethinkdb

Question

On my RethinkDB 1.16.2-1 on Linux, I have a "products" table that has a "categories" array and a "models" array like this:
{
"name": "ABC Cable Series" ,
"categories": [
"Analog Audio>Instrument>Cables" ,
"Analog Audio>Microphone Cables"
] ,
"models": [
{
"modelCode": "ABC-1" ,
"ssp": 11.95 , ...
} ,
{
"modelCode": "ABC-2" ,
"ssp": 15.95 , ...
}
]
} , ...
I need to get both the minimum and maximum price (ssp) range of models in products that contain the given product category. I can currently get the maximum price like this:
r.db("store").table("products").filter(function(prod) {
return prod("categories").contains(
function(cat){return cat.match("^Analog Audio>")
})
}).concatMap(function(doc) {
return doc("models")("ssp")
}).max()
Other than running 2 queries, is there a more efficient way to get both MAX and MIN values in one query?

Answer 1

Presuming you want an object with both values, you can do the following:
r.db('test').table('products').filter(function(prod) {
return prod("categories").contains(
function(cat){return cat.match("^Analog Audio>")
})
}).concatMap(function(doc) {
return doc("models")("ssp")
})
.coerceTo('array') // Convert Stream to Array
.do(function (rows) { // Pass array to to `.do`
return { // Return Object
max: rows.max(),
min: rows.min()
}
})

Answer 2

You can also use reduce (http://rethinkdb.com/api/javascript/reduce/) to compute both values without converting all data to an array first:
r.db("store").table("products").filter(function(prod) {
return prod("categories").contains(
function(cat){return cat.match("^Analog Audio>")
})
}).map(function(doc) {
return {
min: doc("models")("ssp").min(),
max: doc("models")("ssp").max()
}
}).reduce(function (le, ri) {
return {
min: r.expr([le("min"), ri("min")]).min(),
max: r.expr([le("max"), ri("max")]).max()
}
})