We today support a global `indexed_chars` processor parameter. But in some cases, users would like to set this limit depending on the document itself.
It used to be supported in mapper-attachments plugin by extracting the limit value from a meta field in the document sent to indexation process.
We add an option which reads this limit value from the document itself
by adding a setting named `indexed_chars_field`.
Which allows running:
```
PUT _ingest/pipeline/attachment
{
"description" : "Extract attachment information. Used to parse pdf and office files",
"processors" : [
{
"attachment" : {
"field" : "data",
"indexed_chars_field" : "size"
}
}
]
}
```
Then index either:
```
PUT index/doc/1?pipeline=attachment
{
"data": "BASE64"
}
```
Which will use the default value (or the one defined by `indexed_chars`)
Or
```
PUT index/doc/2?pipeline=attachment
{
"data": "BASE64",
"size": 1000
}
```
Closes#28942
87553bba16