Quick and basic tip about how you can partition dates in your map and use that as an array key and then use different group-level values to perform aggregation on different granularity.
Given that we have some simple documents representing sales:
POST /sales/_bulk_docs
{"docs":[
{"_id": "1", "created":"2015-01-01T13:35:01", "by":"adam", "value": 200},
{"_id": "2", "created":"2015-01-01T13:40:02", "by":"john", "value": 220},
{"_id": "3", "created":"2015-01-01T13:40:03", "by":"hans", "value": 10},
{"_id": "4", "created":"2015-01-01T13:50:00", "by":"hans", "value": 190},
{"_id": "5", "created":"2015-01-02T09:05:00", "by":"hans", "value": 10},
{"_id": "6", "created":"2015-02-01T13:40:03", "by":"adam", "value": 200},
{"_id": "7", "created":"2015-03-13T13:40:03", "by":"john", "value": 1333}
]}
Lets say we want to be able to see the value by:
- Year
- Year, Month
- Year, Month, Date
The map should now just return an array as key and the value of the order as the value. It could look something like this:
function(doc) {
var d = new Date(doc.created);
emit([d.getFullYear(),d.getMonth() + 1,d.getDate()], doc.value);
}
For reduce, you could e.g. use the built in _sum or _stats function.
This view is stored in db “sales” under desgin document “salesinfo” as “bydates”, hence accessed via: GET /sales/_design/salesinfo/_view/bydates.
Lets say we want on per year basis, that would be the "first dimension", hence group_level=1:
GET /..?reduce=true&group_level=1
[2015] --> {sum: 2163, count: 7, min: 10, max: 1333, sumsqr: 1941589}
For year & month:
GET /..?reduce=true&group_level=2
[2015, 1] --> {sum: 630, count: 5, min: 10, max: 220, sumsqr: 124700}
[2015, 2] --> {sum: 200, count: 1, min: 200, max: 200, sumsqr: 40000}
[2015, 3] --> {sum: 1333, count: 1, min: 1333, max: 1333, sumsqr: 1776889}
For year, month & date:
GET /..?reduce=true&group_level=3
[2015, 1, 1] --> {sum: 620, count: 4, min: 10, max: 220, sumsqr: 124600}
[2015, 1, 2] --> {sum: 10, count: 1, min: 10, max: 10, sumsqr: 100}
[2015, 2, 1] --> {sum: 200, count: 1, min: 200, max: 200, sumsqr: 40000}
[2015, 3, 13] --> {sum: 1333, count: 1, min: 1333, max: 1333, sumsqr: 1776889}
Now, lets say you want to limit the results to e.g. take from February:
GET /..?reduce=true&group_level=2&start_key=[2015, 2]
[2015, 2] --> {sum: 200, count: 1, min: 200, max: 200, sumsqr: 40000}
[2015, 3] --> {sum: 1333, count: 1, min: 1333, max: 1333, sumsqr: 1776889}
Of course, this also works with another group_level:
GET /..?reduce=true&group_level=1&start_key=[2015, 2]
[2015] --> {sum:1533, count:2, min:200, max: 1333, sumsqr: 1816889}
Quick and simple example of working with arrays as keys.
Cheers,
//Daniel