# Derivative Aggregation（导数聚合） 原文链接 : [https://www.elastic.co/guide/en/elasticsearch/reference/5.4/search-aggregations-pipeline-derivative-aggregation.html](https://www.elastic.co/guide/en/elasticsearch/reference/5.4/search-aggregations-pipeline-derivative-aggregation.html) 译文链接 : [Derivative Aggregation（导数聚合）](/pages/viewpage.action?pageId=10030239) 贡献者 : @苏涛，[ApacheCN](/display/~apachecn)，[Apache中文网](/display/~apachechina) 警告 此功能是实验性的，可能会在将来的版本中完全更改或删除。Elastic将采取最大的努力来解决此问题，但实验功能不受SLA官方功能的支持。 导数管道聚合，其计算父直方图（或日期 - 图形）聚合中指定度量的导数。指定的度量必须是数字，并且必须设置直方图min_doc_count为0（默认为直方图聚合）。 ### 语法 `derivative（导数）` 聚合结构如下： ``` "derivative": { "buckets_path": "the_sum" } ``` `derivative（导数）` 参数如下： | 参数名称 | 描述 | 是否必填 | 默认值 | | --- | --- | --- | --- | | buckets_path | 想要计算导数值的桶路径，点击 [the section called “`buckets_path` Syntax](https://www.elastic.co/guide/en/elasticsearch/reference/5.4/search-aggregations-pipeline.html#buckets-path-syntax "buckets_path Syntaxedit")[edit](https://github.com/elastic/elasticsearch/edit/5.4/docs/reference/aggregations/pipeline.asciidoc "Edit this page on GitHub")”查看更多细节 | 必填 |   | | gap_policy | 当数据缺口出现时采用的策略，点击[the section called “Dealing with gaps in the data](https://www.elastic.co/guide/en/elasticsearch/reference/5.4/search-aggregations-pipeline.html#gap-policy "Dealing with gaps in the dataedit")[edit](https://github.com/elastic/elasticsearch/edit/5.4/docs/reference/aggregations/pipeline.asciidoc "Edit this page on GitHub")”查看更多细节 | 可选 | skip | | format | 用于规范聚合输出值的格式 | 可选 | null | ### 一级导数 以下代码段计算每月总销售额的导数： ``` POST /sales/_search { "size": 0, "aggs" : { "sales_per_month" : { "date_histogram" : { "field" : "date", "interval" : "month" }, "aggs": { "sales": { "sum": { "field": "price" } }, "sales_deriv": { "derivative": { "buckets_path": "sales" #1 } } } } } } ``` | 1 | buckets_path指示这个derivative聚合是想要得到sales_per_month日期直方图聚合中sales聚合值的导数。 | 响应可能如下所示： ``` { "took": 11, "timed_out": false, "_shards": ..., "hits": ..., "aggregations": { "sales_per_month": { "buckets": [ { "key_as_string": "2015/01/01 00:00:00", "key": 1420070400000, "doc_count": 3, "sales": { "value": 550.0 } #1 }, { "key_as_string": "2015/02/01 00:00:00", "key": 1422748800000, "doc_count": 2, "sales": { "value": 60.0 }, "sales_deriv": { "value": -490.0 #2 } }, { "key_as_string": "2015/03/01 00:00:00", "key": 1425168000000, "doc_count": 2, #3 "sales": { "value": 375.0 }, "sales_deriv": { "value": 315.0 } } ] } } } ``` | 1 | 由于我们至少需要2个数据点来计算导数，因此第一个桶没有值 | | 2 | 导数的单位默认和sales聚合以及父直方图相同。所以在这种情况下，如果价格字段的单位是美元，导数的单位就是美元/月 | | 3 | doc_count表示桶中的文档数 | ### 二级导数 可以把导数管道聚合链接到另一个管道聚合的结果，计算二级导数。如以下示例所示，它将计算总月销售额的第一和第二阶导数： ``` POST /sales/_search { "size": 0, "aggs" : { "sales_per_month" : { "date_histogram" : { "field" : "date", "interval" : "month" }, "aggs": { "sales": { "sum": { "field": "price" } }, "sales_deriv": { "derivative": { "buckets_path": "sales" } }, "sales_2nd_deriv": { "derivative": { "buckets_path": "sales_deriv" #1 } } } } } } ``` | 1 | 二阶导数的buckets_path指向一阶导数的名称 | 响应可能如下所示： ``` { "took": 50, "timed_out": false, "_shards": ..., "hits": ..., "aggregations": { "sales_per_month": { "buckets": [ { "key_as_string": "2015/01/01 00:00:00", "key": 1420070400000, "doc_count": 3, "sales": { "value": 550.0 } #1 }, { "key_as_string": "2015/02/01 00:00:00", "key": 1422748800000, "doc_count": 2, "sales": { "value": 60.0 }, "sales_deriv": { "value": -490.0 } #2 }, { "key_as_string": "2015/03/01 00:00:00", "key": 1425168000000, "doc_count": 2, "sales": { "value": 375.0 }, "sales_deriv": { "value": 315.0 }, "sales_2nd_deriv": { "value": 805.0 } } ] } } } ``` | 1 | 由于我们至少需要2个数据点，所以前两个桶没有二级导数 | | 2 | 一级导数计算二级导数 | ### Units（单位） 导数聚合允许指定导数值的单位。这将在响应normalized_value中返回一个额外的字段，汇报在X轴单位下的导数。在下面的例子中，我们计算出每月销售额的导数，但要求销售的导数按天计算： ``` POST /sales/_search { "size": 0, "aggs" : { "sales_per_month" : { "date_histogram" : { "field" : "date", "interval" : "month" }, "aggs": { "sales": { "sum": { "field": "price" } }, "sales_deriv": { "derivative": { "buckets_path": "sales", "unit": "day" #1 } } } } } } ``` | 1 | unit指定用于导数计算的X轴的单位 | 响应可能如下所示： ``` { "took": 50, "timed_out": false, "_shards": ..., "hits": ..., "aggregations": { "sales_per_month": { "buckets": [ { "key_as_string": "2015/01/01 00:00:00", "key": 1420070400000, "doc_count": 3, "sales": { "value": 550.0 } #1 }, { "key_as_string": "2015/02/01 00:00:00", "key": 1422748800000, "doc_count": 2, "sales": { "value": 60.0 }, "sales_deriv": { "value": -490.0, #2 "normalized_value": -15.806451612903226 #3 } }, { "key_as_string": "2015/03/01 00:00:00", "key": 1425168000000, "doc_count": 2, "sales": { "value": 375.0 }, "sales_deriv": { "value": 315.0, "normalized_value": 11.25 } } ] } } } ``` | 1，2 | value值是原单位：按月 | | 3 | `normalized_value值是请求的单位：按天` |