# Should I set the zero value of a floating-point field to 0.0 rather than 0, to help dynamic detection?
**URL:** https://discuss.elastic.co/t/should-i-set-the-zero-value-of-a-floating-point-field-to-0-0-rather-than-0-to-help-dynamic-detection/77929
**Category:** Elasticsearch
**Created:** [March 9, 2017, 3:26am UTC](https://discuss.elastic.co/t/should-i-set-the-zero-value-of-a-floating-point-field-to-0-0-rather-than-0-to-help-dynamic-detection/77929 "2017-03-09T03:26:12Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@GrahamHannington](https://discuss.elastic.co/u/GrahamHannington)
#### Post date: [March 9, 2017, 3:26am UTC](https://discuss.elastic.co/t/should-i-set-the-zero-value-of-a-floating-point-field-to-0-0-rather-than-0-to-help-dynamic-detection/77929/1 "2017-03-09T03:26:12Z")
I think the answer is “Yes”, but I thought it was worth asking this question. Perhaps the answer is “No” or “It doesn’t matter”; in which case, I’ll have learned something about dynamic mapping, and I can save bytes by omitting the trailing `.0`.
I am a member of the development team for a product that extracts data from proprietary binary-format logs, and then forwards that data to Logstash; for example, as JSON Lines over TCP.
Currently, the product represents floating-point field values in JSON like this, where a zero value is represented as a single digit, for conciseness:
```
"wait": 10.123456
....
"wait": 0
```
In practice, Elasticsearch gets the mapping “right”: it maps `wait` to `double`. (I’m currently testing in a backlevel Elasticsearch, 2.4; in Elastic 5.2, I’d expect this to be a `float`.)
But I’m curious how Elasticsearch does that, because, on its own, without sampling other values of that same field, the value `0` makes the `wait` field look like an integer (or `long`).
Perhaps I’ve just been “lucky” so far, but that thought makes me nervous. I’d like to get a better understanding of how Elasticsearch dynamically maps numbers in JSON to its own, more granular, numeric data types.
I’ve read the Elastic documentation topic “[Dynamic field mapping](https://www.elastic.co/guide/en/elasticsearch/reference/current/dynamic-field-mapping.html)”. (Nit: while I can understand the reason for the separate rows, the values “floating point number” and “integer” under the column heading “JSON datatype” are both misleading and strictly incorrect: JSON has no such separate numeric data types.)
I confess I’ve not tried too hard to “trick” Elasticsearch—say, by feeding it a bunch of `0` values for a field in a new index, followed by a floating-point value for the same field. I’m curious: would Elasticsearch initially set the mapping to `long`, and then, when it met the floating-point value, adjust the mapping to `float`?
Back to the primary question, though: should I change “my” product to output `0.0` for floating-point fields, instead of just `0`, to help Elasticsearch dynamic mapping? (And: why, or why not?)
---
### Author:  [@GrahamHannington](https://discuss.elastic.co/u/GrahamHannington)
#### Post date: [March 28, 2017, 4:24am UTC](https://discuss.elastic.co/t/should-i-set-the-zero-value-of-a-floating-point-field-to-0-0-rather-than-0-to-help-dynamic-detection/77929/2 "2017-03-28T04:24:39Z")
> [@GrahamHannington](#):
>
> I confess I’ve not tried too hard to “trick” Elasticsearch—say, by feeding it a bunch of 0 values for a field in a new index, followed by a floating-point value for the same field. I’m curious: would Elasticsearch initially set the mapping to `long`, and then, when it met the floating-point value, adjust the mapping to `float`?
I’ve tried this in Elastic 5.2. The answer is “ **No** ”.
In detail:
- If I forward to a new Elasticsearch index—via the Logstash elasticsearch output; hence, via the Elasticsearch bulk API—an event with a field with the value `0`, and then I query the mapping in Elasticsearch, the (dynamically detected) data type is `long`
- If I do the same thing with the value `0.0`, the data type is `float`
- If I forward to a new index a field with the value `0`, and then I follow that with an event where that field has the value `0.0`, then the data type remains `long`
I don’t get a mapping error from Elasticsearch when I forward a floating-point value for a field that has been mapped to `long`. I’m curious about that; I’m going to create a new topic.
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [April 25, 2017, 4:24am UTC](https://discuss.elastic.co/t/should-i-set-the-zero-value-of-a-floating-point-field-to-0-0-rather-than-0-to-help-dynamic-detection/77929/3 "2017-04-25T04:24:47Z")
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