How to get SUM of all CouchDB values? - view

Question

How to extract SUM depending on ID or something, with goal of getting SUM of all values?
I am able to get all values but canot SUM beacouse its a single variable, so there must be some kind of segmentation to SUM them?? any ideas?
$db = $.couch.db("fuel");
function refreshFuel() {
$("div#fuel").empty();
$db.view("fuel/bill", {success: function(data) {
for (i in data.rows) {
id = data.rows[i].id;
bill = data.rows[i].key;
date = data.rows[i].value;
html = '<div class="fuel">' +
'<span class="bill">' + bill + '</span> ' +
'<span class="date">' + date + '</span> ' +
'</div>';
$("div#fuel").append(html);
}
}});
}
function getAll(){
$("div#all").empty();
$db.view("fuel/bill", {success: function(data) {
for (i in data.rows) {
id = data.rows[i].id;
bill = data.rows[i].key; // how to get SUM of all this values
date = data.rows[i].value;
html =
'<span class="all">' + bill + '</span> '
$("div#all").append(html);
}
}});
}
EDIT:
my JSON looks like this:
{
"_id": "1a06982d3434f37a04a02dbf360010ee",
"_rev": "1-c8c9d5252a76abd8f565ff82bf63b0e8",
"value": "200",
"date": "2011-09-05T10:28:55.101Z"
}
and my VIEW look like this:
function(doc) {
if (doc.value, doc.date) {
emit(doc.value,doc.date, doc);
}
}

Answer 1

You just need to add a reduce function, e.g,
function(keys, values, rereduce) {
return sum(values);
}
This is so common that we have a built-in function that's much faster;
_sum
You'll need to emit the value you want to sum as the value, so something like;
function(doc) {
emit(doc.date, doc.value);
}