Native (Java) Scripts
editNative (Java) Scripts
editSometimes groovy and expression aren’t enough. For those times you can
implement a native script.
The best way to implement a native script is to write a plugin and install it. The plugin documentation has more information on how to write a plugin so that Elasticsearch will properly load it.
To register the actual script you’ll need to implement NativeScriptFactory
to construct the script. The actual script will extend either
AbstractExecutableScript or AbstractSearchScript. The second one is likely
the most useful and has several helpful subclasses you can extend like
AbstractLongSearchScript and AbstractDoubleSearchScript.
Finally, your plugin should register the native script by implementing the
ScriptPlugin interface.
If you squashed the whole thing into one class it’d look like:
public class MyNativeScriptPlugin extends Plugin implements ScriptPlugin {
@Override
public List<NativeScriptFactory> getNativeScripts() {
return Collections.singletonList(new MyNativeScriptFactory());
}
public static class MyNativeScriptFactory implements NativeScriptFactory {
@Override
public ExecutableScript newScript(@Nullable Map<String, Object> params) {
return new MyNativeScript();
}
@Override
public boolean needsScores() {
return false;
}
@Override
public String getName() {
return "my_script";
}
}
public static class MyNativeScript extends AbstractDoubleSearchScript {
@Override
public double runAsDouble() {
double a = (double) source().get("a");
double b = (double) source().get("b");
return a * b;
}
}
}
You can execute the script by specifying its lang as native, and the name
of the script as the id:
POST /_search
{
"query": {
"function_score": {
"query": {
"match": {
"body": "foo"
}
},
"functions": [
{
"script_score": {
"script": {
"inline": "my_script",
"lang" : "native"
}
}
}
]
}
}
}