Elasticsearch: how to search on computed fields - elasticsearch

Question

Using the data from the current version of Elasticsearch: The Definitive Guide, that is:
[{
"first_name" : "John",
"last_name" : "Smith",
"age" : 25,
"about" : "I love to go rock climbing",
"interests": [ "sports", "music" ]
}, {
"first_name" : "Jane",
"last_name" : "Smith",
"age" : 32,
"about" : "I like to collect rock albums",
"interests": [ "music" ]
}, {
"first_name" : "Douglas",
"last_name" : "Fir",
"age" : 35,
"about": "I like to build cabinets",
"interests": [ "forestry" ]
}]
I'm trying to run a simple computation (I've enabled Groovy scripting) using the request data:
{
"query": {
"filtered": {
"filter": {
"range": {
"max_age": {
"gt": 150
}
}
}
}
},
"script_fields": {
"max_age": {
"script": "_source.age * 5"
}
}
}
But ES isn't returning any data. How can I search over computed fields? It's even better if I don't need to enable scripting.

Answer 1

script_fields are computed after the query phase, i.e. during the fetch phase, so you cannot reference script fields inside your queries.
What you need to achieve can still be done, though, by using a script filter, like this:
{
"query": {
"bool": {
"must": {
"script": {
"script": {
"inline": "doc['age'].value * factor > max_age",
"params": {
"factor": 5,
"max_age": 150
}
}
}
}
}
}
}