presto-main/src/main/java/io/prestosql/operator/scalar/JsonFunctions.java/JsonFunctions/jsonExtractScalar
class JsonFunctions:    @ScalarFunction
    @SqlNullable
    @SqlType(StandardTypes.VARCHAR)
    public static Slice jsonExtractScalar(@SqlType(StandardTypes.JSON) Slice json, @SqlType(JsonPathType.NAME) JsonPath jsonPath)
    {
        return JsonExtract.extract(json, jsonPath.getScalarExtractor());
    }