Document using docvalue_fields to retrieve _size field from mapper size plugin #57103
Description
The mapper size plugin documentation notes that the _size field can be retrieved using script_fields like so:
"script_fields": {
"size": {
"script": "doc['_size']"
}
}
An alternative is to use docvalue_fields like so:
"docvalue_fields" : [
{
"field": "_size",
"format": "use_field_mapping"
}
]
This second option is helpful for situations where users may have dynamic scripting disabled. I'm not sure, but it my also perform better than the script fields option.