[Runtime fields](docs-content://manage-data/data-store/mapping/runtime-fields.md) provide a very similar feature that is more flexible. You write a script to create field values and they are available everywhere, such as [`fields`](/reference/elasticsearch/rest-apis/retrieve-selected-fields.md), [all queries](/reference/query-languages/querydsl.md), and [aggregations](/reference/aggregations/index.md).
Filters documents based on a provided [script](docs-content://explore-analyze/scripting/modules-scripting-using.md). The `script` query is typically used in a [filter context](/reference/query-languages/query-dsl/query-filter-context.md).
Using scripts can result in slower search speeds. See [Scripts, caching, and search speed](docs-content://explore-analyze/scripting/scripts-search-speed.md).
::::
## Example request [script-query-ex-request]
```console
GET /_search
{
"query": {
"bool": {
"filter": {
"script": {
"script": """
double amount = doc['amount'].value;
if (doc['type'].value == 'expense') {
amount *= -1;
}
return amount <10;
"""
}
}
}
}
}
```
You can achieve the same results in a search query by using runtime fields. Use the [`fields`](/reference/elasticsearch/rest-apis/retrieve-selected-fields.md) parameter on the `_search` API to fetch values as part of the same query:
```console
GET /_search
{
"runtime_mappings": {
"amount.signed": {
"type": "double",
"script": """
double amount = doc['amount'].value;
if (doc['type'].value == 'expense') {
amount *= -1;
}
emit(amount);
"""
}
},
"query": {
"bool": {
"filter": {
"range": {
"amount.signed": { "lt": 10 }
}
}
}
},
"fields": [{"field": "amount.signed"}]
}
```
## Top-level parameters for `script` [script-top-level-params]
`script`
: (Required, [script object](docs-content://explore-analyze/scripting/modules-scripting-using.md)) Contains a script to run as a query. This script must return a boolean value, `true` or `false`.
Like [filters](/reference/query-languages/query-dsl/query-filter-context.md), scripts are cached for faster execution. If you frequently change the arguments of a script, we recommend you store them in the script’s `params` parameter. For example:
Script queries will not be executed if [`search.allow_expensive_queries`](/reference/query-languages/querydsl.md#query-dsl-allow-expensive-queries) is set to false.