Elasticsearch - Query based on text length - node.js

Question

I'm using the official Elasticsearch NodeJS client library, to query the following index structure:
{
"_index": "articles",
"_type": "context",
"_id": "1",
"_version": 1,
"found": true,
"_source": {
"article": "this is a paragraph",
"topic": "topic A"
}
}
{
"_index": "articles",
"_type": "context",
"_id": "2",
"_version": 1,
"found": true,
"_source": {
"article": "this is a paragraph this is a paragraph this is a paragraph",
"topic": "topic B"
}
}
I would like to query my index using the term "this is a paragraph" and boost the result with the most similar text length, IE: document _id:1
Can I do this without re-indexing and adding a field to my index (as described here)?

Answer 1

The below query uses Groovy to look at the length of the actual text indexed into ES (using _source.article.length()) and at the length of the text to be searched. As a very simple basic query, I used match_phrase and then rescored the documents based on how long the text to search is compared to how long the original text is.
GET /articles/context/_search
{
"query": {
"function_score": {
"query": {
"match_phrase": {
"article": "this is a paragraph"
}
},
"functions": [
{
"script_score": {
"script": {
"inline": "text_to_search_length=text_to_search.length(); compared_length=_source.article.length();return (compared_length-text_to_search_length).abs()",
"params": {
"text_to_search": "this is a paragraph"
}
}
}
}
]
}
},
"sort": [
{
"_score": {
"order": "asc"
}
}
]
}