# Field Collapsing 字段折疊 原文鏈接 : [https://www.elastic.co/guide/en/elasticsearch/reference/5.4/search-request-collapse.html](https://www.elastic.co/guide/en/elasticsearch/reference/5.4/search-request-collapse.html) 譯文鏈接 : [http://cwiki.apachecn.org/pages/editpage.action?pageId=10813543](http://cwiki.apachecn.org/pages/editpage.action?pageId=10813543) 貢獻者 : [李辰](/display/~lichen)，[ApacheCN](/display/~apachecn)，[Apache中文網](/display/~apachechina) 允許基于字段對結果進行折疊。折疊操作是通過每個選擇每個折疊鍵的頂部文檔來實現的。例如下面的query獲取每個user的最佳tweet并且根據他們的likes數量排序。 ``` GET /twitter/tweet/_search ``` ``` { ``` ``` ??? "query": { ``` ``` ??????? "match": { ``` ``` ??????????? "message": "elasticsearch" ``` ``` ??????? } ``` ``` ??? }, ``` ``` ??? "collapse" : { ``` ``` ??????? "field" : "user"  ``` ``` ????}, ``` ``` ???"sort": ["likes"],  ``` ``` ?? "from": 10  ``` ``` } ``` [](https://www.elastic.co/guide/en/elasticsearch/reference/5.4/search-request-collapse.html#CO27-1)??? 使用user字段來折疊結果集 * * * [](https://www.elastic.co/guide/en/elasticsearch/reference/5.4/search-request-collapse.html#CO27-2)??? 按照likes數量進行排序獲取頂部文檔 * * * [](https://www.elastic.co/guide/en/elasticsearch/reference/5.4/search-request-collapse.html#CO27-3)??? 定義第一個折疊結果的偏移量 ****警告：**** 響應結果中的hits總數表示匹配的文檔總數而不是折疊的，去重后的聚合總數是未知的。 用于折疊的字段必須是單值的[keyword](/display/Elasticsearch/KeyWord)或[numeric](/display/Elasticsearch/Numeric)字段并開啟[doc_values](/pages/viewpage.action?pageId=10027604)（文檔值）。 **注意：** 折疊只應用于頂部文檔，而且不會影響聚合。 ## 擴大折疊的顯示結果 它也可以通過_inner_hits_參數來擴大每個折疊的頂部文檔。 GET /twitter/tweet/_search { ??? "query": { ??????? "match": { ??????????? "message": "elasticsearch" ??????? } ??? }, ??? "collapse" : { ??????? "field" : "user", ??????? "inner_hits": { ??????????? "name": "last_tweets", ??????????? "size": 5, ??????????? "sort": [{ "date": "asc" }] ??????? }, ??????? "max_concurrent_group_searches": 4 ??? }, ??? "sort": ["likes"] } [](https://www.elastic.co/guide/en/elasticsearch/reference/5.4/search-request-collapse.html#CO28-1)??? 使用"user"字段折疊結果集 * * * [](https://www.elastic.co/guide/en/elasticsearch/reference/5.4/search-request-collapse.html#CO28-2)??? name參數用來分割結果響應中的inner_hits * * * [](https://www.elastic.co/guide/en/elasticsearch/reference/5.4/search-request-collapse.html#CO28-3)??? 每個折疊內inner_hits檢索到的數目 * * * [](https://www.elastic.co/guide/en/elasticsearch/reference/5.4/search-request-collapse.html#CO28-4)??? 每個分組的排序方式 * * * [](https://www.elastic.co/guide/en/elasticsearch/reference/5.4/search-request-collapse.html#CO28-5)??? 每個分組內允許檢索inner_hits的并發請求數量 查看[inner hits?](/display/Elasticsearch/Inner+hits)對于所支持的選項的完整列表和響應的格式。 該分組的擴展是通過向響應中返回的每個折疊的命中發送一個額外的查詢來完成的。請求參數 `max_concurrent_group_searches` 可用于控制這個階段并發搜索的最大數量。 默認值是基于數據節點的數量和默認的搜索線程池大小。 ****警告：**** `collapse(折疊)不能用于與[scroll](/display/Elasticsearch/Scroll), [rescore](/display/Elasticsearch/Rescoring), [search after](/display/Elasticsearch/Search+After) 一同使用。`