Range Aggregation(范围聚合)

原文链接 : https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-bucket-range-aggregation.html

译文链接 : http://www.apache.wiki/display/Elasticsearch（修改该链接为 ApacheCN 对应的译文链接）

贡献者 : @于永超，ApacheCN，Apache中文网

Range Aggregation

A multi-bucket value source based aggregation that enables the user to define a set of ranges－每个代表一个bucket。在聚合过程中，从每个文件中提取的值将根据每个存储区范围进行检查，并对相关/匹配文档进行“bucket”，值得注意的是，注意，此聚合包含了from值，不包括每个范围的to的值。

例子：

{
    "aggs" : {
        "price_ranges" : {
            "range" : {
                "field" : "price",
                "ranges" : [
                    { "to" : 50 },
                    { "from" : 50, "to" : 100 },
                    { "from" : 100 }
                ]
            }
        }
    }
}

响应结果：

{
    ...
    "aggregations": {
        "price_ranges" : {
            "buckets": [
                {
                    "to": 50,
                    "doc_count": 2
                },
                {
                    "from": 50,
                    "to": 100,
                    "doc_count": 4
                },
                {
                    "from": 100,
                    "doc_count": 4
                }
            ]
        }
    }
}

Keyed Response

将keyed标志设置为true会将一个惟一的字符串键与每个bucket关联起来，并将范围作为散列而不是数组返回:

{
    "aggs" : {
        "price_ranges" : {
            "range" : {
                "field" : "price",
                "keyed" : true,
                "ranges" : [
                    { "to" : 50 },
                    { "from" : 50, "to" : 100 },
                    { "from" : 100 }
                ]
            }
        }
    }
}

响应结果：

{
    ...
    "aggregations": {
        "price_ranges" : {
            "buckets": {
                "*-50.0": {
                    "to": 50,
                    "doc_count": 2
                },
                "50.0-100.0": {
                    "from": 50,
                    "to": 100,
                    "doc_count": 4
                },
                "100.0-*": {
                    "from": 100,
                    "doc_count": 4
                }
            }
        }
    }
}

可以为每个范围自定义key：

{
    "aggs" : {
        "price_ranges" : {
            "range" : {
                "field" : "price",
                "keyed" : true,
                "ranges" : [
                    { "key" : "cheap", "to" : 50 },
                    { "key" : "average", "from" : 50, "to" : 100 },
                    { "key" : "expensive", "from" : 100 }
                ]
            }
        }
    }
}

Script

{
    "aggs" : {
        "price_ranges" : {
            "range" : {
                "script" : {
                    "lang": "painless",
                    "inline": "doc['price'].value"
                },
                "ranges" : [
                    { "to" : 50 },
                    { "from" : 50, "to" : 100 },
                    { "from" : 100 }
                ]
            }
        }
    }
}

这将把script参数解释为具有painless脚本语言和no script参数的inline脚本。要使用文件脚本，请使用以下语法

{
    "aggs" : {
        "price_ranges" : {
            "range" : {
                "script" : {
                    "file": "my_script",
                    "params": {
                        "field": "price"
                    }
                },
                "ranges" : [
                    { "to" : 50 },
                    { "from" : 50, "to" : 100 },
                    { "from" : 100 }
                ]
            }
        }
    }
}

对于索引脚本，用id参数替换file参数。

Value Script

假设产品价格是美元，但我们希望得到欧元的价格区间，我们可以使用value script在聚合之前转换价格（假设汇率是0.8）

{
    "aggs" : {
        "price_ranges" : {
            "range" : {
                "field" : "price",
                "script" : {
                    "lang": "painless",
                    "inline": "_value * params.conversion_rate",
                    "params" : {
                        "conversion_rate" : 0.8
                    }
                },
                "ranges" : [
                    { "to" : 35 },
                    { "from" : 35, "to" : 70 },
                    { "from" : 70 }
                ]
            }
        }
    }
}

Sub Aggregations

下面的示例不仅将文档“bucket”到不同的bucket，而且计算每个价格范围内的价格统计

{
    "aggs" : {
        "price_ranges" : {
            "range" : {
                "field" : "price",
                "ranges" : [
                    { "to" : 50 },
                    { "from" : 50, "to" : 100 },
                    { "from" : 100 }
                ]
            },
            "aggs" : {
                "price_stats" : {
                    "stats" : { "field" : "price" }
                }
            }
        }
    }
}

响应结果：

{
    "aggregations": {
        "price_ranges" : {
            "buckets": [
                {
                    "to": 50,
                    "doc_count": 2,
                    "price_stats": {
                        "count": 2,
                        "min": 20,
                        "max": 47,
                        "avg": 33.5,
                        "sum": 67
                    }
                },
                {
                    "from": 50,
                    "to": 100,
                    "doc_count": 4,
                    "price_stats": {
                        "count": 4,
                        "min": 60,
                        "max": 98,
                        "avg": 82.5,
                        "sum": 330
                    }
                },
                {
                    "from": 100,
                    "doc_count": 4,
                    "price_stats": {
                        "count": 4,
                        "min": 134,
                        "max": 367,
                        "avg": 216,
                        "sum": 864
                    }
                }
            ]
        }
    }
}

如果sub aggregation（子集合）也基于与范围聚合相同的值（如上例中的统计信息聚合），则可以省略其值的定义。以下内容将返回与上述相同的结果

{
    "aggs" : {
        "price_ranges" : {
            "range" : {
                "field" : "price",
                "ranges" : [
                    { "to" : 50 },
                    { "from" : 50, "to" : 100 },
                    { "from" : 100 }
                ]
            },
            "aggs" : {
                "price_stats" : {
                    "stats" : {} ＃1
                }
            }
        }
    }
}

＃1 我们不需要指定price，因为我们默认从父范围聚合“继承”它