# Set Field Value in Painless Script by Field Name as String
**URL:** https://discuss.elastic.co/t/set-field-value-in-painless-script-by-field-name-as-string/328719
**Category:** Elasticsearch
**Tags:** painless
**Created:** [March 28, 2023, 2:25pm UTC](https://discuss.elastic.co/t/set-field-value-in-painless-script-by-field-name-as-string/328719 "2023-03-28T14:25:23Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@DougR](https://discuss.elastic.co/u/DougR)
#### Post date: [March 28, 2023, 2:25pm UTC](https://discuss.elastic.co/t/set-field-value-in-painless-script-by-field-name-as-string/328719/1 "2023-03-28T14:25:23Z")
# TL;DR
I'm trying to pass in a nested key to a Painless script as a string and set that key from the script, but it's not working. How do I do this?# Use Case
# Long Version
## Use Case
As a user, I need to perform the same transform in an ingest pipeline using a Painless script on multiple nested fields. However, the field name is arbitrary and will vary, based on the input data.
## Current Solution
The best solution appears to be to pass the name of the nested field into the script as a string (e.g., `a.b.c`), but this does not work in all situations.
### Example
Assume the following document structure:
```json
{
"a": {
"b": {
"c": "string"
}
}
}
```
Applying the following script to retrieve the value of `a.b.c` works as expected with the parameter `{ "source_field": "a.b.c" }`:
```auto
def val = ctx;
def keys = params['source_field'].splitOnToken('.');
for (key in keys) {
val = val[key];
}
val;
```
I don't like having to iterate down through the object to get the value for `a.b.c`, but it works.
If I execute the following code with the parameters `{ "source_field": "a.b.c", "dest_field": "d.e.f" }`:
```auto
def val = ctx;
def keys = params['source_field'].splitOnToken('.');
for (key in keys) {
val = val[key];
}
ctx[params['dest_field']] = val;
```
I get the expected output:
```json
{
"a": {
"b": {
"c": "string"
}
},
"d": {
"e": {
"f": "string"
}
}
}
```
However, if `d.e.f` already exists and I'm attempting to overwrite the field, or even `d` exists, it does not save `d.e.f` to the document. Presumably this is because what I'm actually doing is creating a new key called `{"d.e.f":"string"}`.
How can I accomplish this?
> **Note:** It would be great if the `set` ingest processor were exposed through the `Processors` object, but alas, it's not.
---
### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [April 25, 2023, 2:25pm UTC](https://discuss.elastic.co/t/set-field-value-in-painless-script-by-field-name-as-string/328719/2 "2023-04-25T14:25:54Z")
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