# Get number of days in a month to aggregate data
**URL:** https://discuss.elastic.co/t/get-number-of-days-in-a-month-to-aggregate-data/206028
**Category:** Elasticsearch
**Created:** [October 31, 2019, 11:42am UTC](https://discuss.elastic.co/t/get-number-of-days-in-a-month-to-aggregate-data/206028 "2019-10-31T11:42:09Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@Quang\_D\_Tr\_n](https://discuss.elastic.co/u/Quang_D_Tr_n)
#### Post date: [October 31, 2019, 11:42am UTC](https://discuss.elastic.co/t/get-number-of-days-in-a-month-to-aggregate-data/206028/1 "2019-10-31T11:42:10Z")
I am trying to get the number of days of a month from a timestamp field, and then, divide the one numeric field by this number of days.
Right now, my implementation is like this:
```auto
{
"query" : {...},
"script_fields": {
"days_of_month": {
"script": {
"source": "Calendar cal = Calendar.getInstance(); cal.setTimeInMillis(doc['timestamp'].value); return cal.getActualMaximum(Calendar.DAY_OF_MONTH);"
}
}
},
"aggregations": {...}
}
```
My intention is to create a new field named `days_of_month` and then later put it in `bucket_script params` to use in aggregation part. But the result does not returns any `days_of_month`.
If I put the `script_fields` under `aggregation` then it the server can't parse the json.
Any idea to implement this kind of aggregation would be very much appreciated.
Thank you!
* * *
UPDATE:
Since I set the size as 0 because I only care about the aggregation result so the `days_of_month` is missing. Set the size as 1 and this will return the number of days in the month.
---
### Author:  [@spinscale](https://discuss.elastic.co/u/spinscale)
#### Post date: [October 31, 2019, 3:04pm UTC](https://discuss.elastic.co/t/get-number-of-days-in-a-month-to-aggregate-data/206028/2 "2019-10-31T15:04:37Z")
is there any chance you can use a script in aggregation (like terms) to figure out the right logic to bucket.. maybe you can explain what you are after in more detail.
---
### Author:  [@Quang\_D\_Tr\_n](https://discuss.elastic.co/u/Quang_D_Tr_n)
#### Post date: [October 31, 2019, 3:24pm UTC](https://discuss.elastic.co/t/get-number-of-days-in-a-month-to-aggregate-data/206028/3 "2019-10-31T15:24:09Z")
@spinscale Thanks Alex, I figure out what I am missing. Since I set the size as 0 (I use result in aggregation only) so that scripted field is missing. After set the size as 1, it comes back as expected.
In `aggregation` part, I group data daily in a month. I already have the `_source.month_price` so scripted field above is for division to get daily price. After that, I will multiply the field `extra_usage` with the `daily_price` to have daily daily charge. That is what I am after.
However, scripted field is not able to be reused in aggregation. Hence, there will be duplicate calculation for the value of the scrpited field if I put the whole script (get days of a month) in aggregation.
Maybe I have to do it in the client side. 🙂
Cheers!
---
### Author:  [@spinscale](https://discuss.elastic.co/u/spinscale)
#### Post date: [November 4, 2019, 9:51am UTC](https://discuss.elastic.co/t/get-number-of-days-in-a-month-to-aggregate-data/206028/4 "2019-11-04T09:51:30Z")
it seems to me, that you could do that scripting calculation as part of the aggregation without any need of a scripted field
---
### Author:  [@Quang\_D\_Tr\_n](https://discuss.elastic.co/u/Quang_D_Tr_n)
#### Post date: [November 5, 2019, 4:19am UTC](https://discuss.elastic.co/t/get-number-of-days-in-a-month-to-aggregate-data/206028/5 "2019-11-05T04:19:20Z")
yes Alex, but if the script as a part of aggregation then the result will be calculated for many times, depending on the hit bucket size, leading to duplication.
That is why I want it to be calculated once only and then use it in aggregation later but it seems to be a challenge.
---
### Author:  [@spinscale](https://discuss.elastic.co/u/spinscale)
#### Post date: [November 5, 2019, 9:35am UTC](https://discuss.elastic.co/t/get-number-of-days-in-a-month-to-aggregate-data/206028/6 "2019-11-05T09:35:18Z")
I am not sure I understand the last post. A script field will also be executed for every hit.
---
### Author:  [@Quang\_D\_Tr\_n](https://discuss.elastic.co/u/Quang_D_Tr_n)
#### Post date: [November 6, 2019, 7:40am UTC](https://discuss.elastic.co/t/get-number-of-days-in-a-month-to-aggregate-data/206028/7 "2019-11-06T07:40:59Z")
Really? I notice in the result json, there is only one section for field script if I put it outside aggregation. If I put it inside aggregation, it will return the same number of output as aggregation hits.
So I assume that putting field script outside of the aggregation section, it will be executed once only.
Is that so?
```auto
"days_of_month": {
"script": {
"source": "Calendar cal = Calendar.getInstance(); cal.setTimeInMillis(doc['timestamp'].value); return cal.getActualMaximum(Calendar.DAY_OF_MONTH);"
}
}
},
"aggregations": {...}
//Inside aggregation
"aggregations": {
"script_fields": {
"days_of_month": {
"script": {
"source": "Calendar cal = Calendar.getInstance();cal.setTimeInMillis(doc['timestamp'].value); return cal.getActualMaximum(Calendar.DAY_OF_MONTH);"
}
}
},...
}
```
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [December 4, 2019, 7:41am UTC](https://discuss.elastic.co/t/get-number-of-days-in-a-month-to-aggregate-data/206028/8 "2019-12-04T07:41:00Z")
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