Rethinkdb execute multiple avg in one query

Question

I have a review table with multiple number columns. I would like to count he avg of all columns in one query.

So if the table looks like:

{ 
   foo : 2,
   bar : 5,
   foobar : 10
},
{
   foo : 4,
   bar : 3,
   foobar : 12
}

then i would like to get the avg for each column in one query. I know I can do:

r.table('stats' ).avg( 'foo' )

on each column but I would like to do this in just one query and map into into just one object.

Any ideas on how to do this?

Answer 1

You can use map with reduce (if every record in table has all 3 fields):

r.table("stats").map(function(row){
  return {foo : row("foo"), bar : row("bar") , foobar : row("foobar"), count : 1};
}).reduce(function(left, right){
  return {foo : left("foo").add(right("foo")), bar : left("bar").add(right("bar")), foobar : left("foobar").add(right("foobar")), count : left("count").add(right("count"))};
}).do(function (res) {
  return {
    foo: res('foo').div(res("count")),
    bar: res('bar').div(res("count")),
    foobar: res('foobar').div(res("count"))
  };
})

If record can have not all fields, you can separate count in map operation for each field, and then in do use it depending on field.