Elasticsearch: Give higher score to long title - elasticsearch

Question

I have an Elasticsearch database in which all documents have a title field and are queried by this field.
By default, Elasticsearch search gives higher score to document with short title. But, in my use case, short titles are irrelevant.
For example, when I search for 'Deep Learning' the first results are
'Deep Learning'
'Machine Learning and Deep Learning'
'Semi-Supervised Deep Learning With Memory'
I would like the document titled 'Semi-Supervised Deep Learning With Memory' to appear before the document titled 'Deep Learning'.
Is there any solution to achieve that without changing the mapping?
Thanks

Answer 1

The best way would be to compute the content length ant the ingesting time, keep it in a field and use it with a function score query.
{
"query": {
"function_score": {
"query": {
"match": { "title": "elasticsearch" }
},
"script_score": {
"script": {
"source": "doc['title_length'].value * _score"
}
}
}
}
}
Or you can use a script score query which use the field size if you have a keyword mapping on this field.
If not you will have to enable field data on it. But it's very expensive and not recommended.
https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-script-score-query.html
GET /_search
{
"query": {
"script_score": {
"query": {
"match": { "title": "elasticsearch" }
},
"script": {
"source": "doc['title'].value.length() * _score"
}
}
}
}