常用ElasticSearch 查詢語句
- 2020 年 4 月 23 日
- 筆記
- 【ElasticSearch】
為了演示不同類型的 ElasticSearch 的查詢，我們將使用書文檔資訊的集合（有以下欄位：title（標題）, authors（作者）, summary（摘要）, publish_date（發布日期）和 num_reviews（瀏覽數））。
在這之前，首先我們應該先創建一個新的索引（index），並批量導入一些文檔：
創建索引：
PUT /bookdb_index { "settings": { "number_of_shards": 1 }}
批量上傳文檔：
POST /bookdb_index/book/_bulk { "index": { "_id": 1 }} { "title": "Elasticsearch: The Definitive Guide", "authors": ["clinton gormley", "zachary tong"], "summary" : "A distibuted real-time search and analytics engine", "publish_date" : "2015-02-07", "num_reviews": 20, "publisher": "oreilly" } { "index": { "_id": 2 }} { "title": "Taming Text: How to Find, Organize, and Manipulate It", "authors": ["grant ingersoll", "thomas morton", "drew farris"], "summary" : "organize text using approaches such as full-text search, proper name recognition, clustering, tagging, information extraction, and summarization", "publish_date" : "2013-01-24", "num_reviews": 12, "publisher": "manning" } { "index": { "_id": 3 }} { "title": "Elasticsearch in Action", "authors": ["radu gheorge", "matthew lee hinman", "roy russo"], "summary" : "build scalable search applications using Elasticsearch without having to do complex low-level programming or understand advanced data science algorithms", "publish_date" : "2015-12-03", "num_reviews": 18, "publisher": "manning" } { "index": { "_id": 4 }} { "title": "Solr in Action", "authors": ["trey grainger", "timothy potter"], "summary" : "Comprehensive guide to implementing a scalable search engine using Apache Solr", "publish_date" : "2014-04-05", "num_reviews": 23, "publisher": "manning" }
栗子：
1. 基本的匹配（Query）查詢
有兩種方式來執行一個全文匹配查詢：
- 使用 Search Lite API，它從
url中讀取所有的查詢參數 - 使用完整 JSON 作為請求體，這樣你可以使用完整的 Elasticsearch DSL
下面是一個基本的匹配查詢，查詢任一欄位包含 Guide 的記錄
GET /bookdb_index/book/_search?q=guide [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "1", "_score": 0.28168046, "_source": { "title": "Elasticsearch: The Definitive Guide", "authors": ["clinton gormley", "zachary tong"], "summary": "A distibuted real-time search and analytics engine", "publish_date": "2015-02-07", "num_reviews": 20, "publisher": "manning" } }, { "_index": "bookdb_index", "_type": "book", "_id": "4", "_score": 0.24144039, "_source": { "title": "Solr in Action", "authors": ["trey grainger", "timothy potter"], "summary": "Comprehensive guide to implementing a scalable search engine using Apache Solr", "publish_date": "2014-04-05", "num_reviews": 23, "publisher": "manning" } } ]
下面是完整 Body 版本的查詢，生成相同的內容：
{ "query": { "multi_match" : { "query" : "guide", "fields" : ["_all"] } } }
multi_match 是 match 的作為在多個欄位運行相同操作的一個速記法。fields 屬性用來指定查詢針對的欄位，在這個例子中，我們想要對文檔的所有欄位進行匹配。兩個 API 都允許你指定要查詢的欄位。例如，查詢 title 欄位中包含 in Action 的書：
GET /bookdb_index/book/_search?q=title:in action [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "4", "_score": 0.6259885, "_source": { "title": "Solr in Action", "authors": [ "trey grainger", "timothy potter" ], "summary": "Comprehensive guide to implementing a scalable search engine using Apache Solr", "publish_date": "2014-04-05", "num_reviews": 23, "publisher": "manning" } }, { "_index": "bookdb_index", "_type": "book", "_id": "3", "_score": 0.5975345, "_source": { "title": "Elasticsearch in Action", "authors": [ "radu gheorge", "matthew lee hinman", "roy russo" ], "summary": "build scalable search applications using Elasticsearch without having to do complex low-level programming or understand advanced data science algorithms", "publish_date": "2015-12-03", "num_reviews": 18, "publisher": "manning" } } ]
然而， 完整的 DSL 給予你靈活創建更複雜查詢和指定返回結果的能力（後面，我們會一一闡述）。在下面例子中，我們指定 size 限定返回的結果條數，from 指定起始位子，_source 指定要返回的欄位，以及語法高亮
POST /bookdb_index/book/_search { "query": { "match" : { "title" : "in action" } }, "size": 2, "from": 0, "_source": [ "title", "summary", "publish_date" ], "highlight": { "fields" : { "title" : {} } } } [Results] "hits": { "total": 2, "max_score": 0.9105287, "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "3", "_score": 0.9105287, "_source": { "summary": "build scalable search applications using Elasticsearch without having to do complex low-level programming or understand advanced data science algorithms", "title": "Elasticsearch in Action", "publish_date": "2015-12-03" }, "highlight": { "title": [ "Elasticsearch <em>in</em> <em>Action</em>" ] } }, { "_index": "bookdb_index", "_type": "book", "_id": "4", "_score": 0.9105287, "_source": { "summary": "Comprehensive guide to implementing a scalable search engine using Apache Solr", "title": "Solr in Action", "publish_date": "2014-04-05" }, "highlight": { "title": [ "Solr <em>in</em> <em>Action</em>" ] } } ] }
注意：對於多個詞查詢，match 允許指定是否使用 and 操作符來取代默認的 or 操作符。你還可以指定 mininum_should_match 選項來調整返回結果的相關程度。具體看後面的例子。
2. 多欄位（Multi-filed）查詢
正如我們已經看到來的，為了根據多個欄位檢索（e.g. 在 title 和 summary 欄位都是相同的查詢字元串的結果），你可以使用 multi_match 語句
POST /bookdb_index/book/_search { "query": { "multi_match" : { "query" : "elasticsearch guide", "fields": ["title", "summary"] } } } [Results] "hits": { "total": 3, "max_score": 0.9448582, "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "1", "_score": 0.9448582, "_source": { "title": "Elasticsearch: The Definitive Guide", "authors": [ "clinton gormley", "zachary tong" ], "summary": "A distibuted real-time search and analytics engine", "publish_date": "2015-02-07", "num_reviews": 20, "publisher": "manning" } }, { "_index": "bookdb_index", "_type": "book", "_id": "3", "_score": 0.17312013, "_source": { "title": "Elasticsearch in Action", "authors": [ "radu gheorge", "matthew lee hinman", "roy russo" ], "summary": "build scalable search applications using Elasticsearch without having to do complex low-level programming or understand advanced data science algorithms", "publish_date": "2015-12-03", "num_reviews": 18, "publisher": "manning" } }, { "_index": "bookdb_index", "_type": "book", "_id": "4", "_score": 0.14965448, "_source": { "title": "Solr in Action", "authors": [ "trey grainger", "timothy potter" ], "summary": "Comprehensive guide to implementing a scalable search engine using Apache Solr", "publish_date": "2014-04-05", "num_reviews": 23, "publisher": "manning" } } ] }
注：第三條被匹配，因為 guide 在 summary 欄位中被找到。
3. Boosting
由於我們是多個欄位查詢，我們可能需要提高某一個欄位的分值。在下面的例子中，我們把 summary 欄位的分數提高三倍，為了提升 summary 欄位的重要度；因此，我們把文檔 4 的相關度提高了。
POST /bookdb_index/book/_search { "query": { "multi_match" : { "query" : "elasticsearch guide", "fields": ["title", "summary^3"] } }, "_source": ["title", "summary", "publish_date"] } [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "1", "_score": 0.31495273, "_source": { "summary": "A distibuted real-time search and analytics engine", "title": "Elasticsearch: The Definitive Guide", "publish_date": "2015-02-07" } }, { "_index": "bookdb_index", "_type": "book", "_id": "4", "_score": 0.14965448, "_source": { "summary": "Comprehensive guide to implementing a scalable search engine using Apache Solr", "title": "Solr in Action", "publish_date": "2014-04-05" } }, { "_index": "bookdb_index", "_type": "book", "_id": "3", "_score": 0.13094766, "_source": { "summary": "build scalable search applications using Elasticsearch without having to do complex low-level programming or understand advanced data science algorithms", "title": "Elasticsearch in Action", "publish_date": "2015-12-03" } } ]
注：提升不是簡簡單單通過提升因子把計算分數加成。實際的 boost 值通過歸一化和一些內部優化給出的。相關資訊請見 Elasticsearch guide
4. Bool 查詢
為了提供更相關或者特定的結果，AND/OR/NOT 操作符可以用來調整我們的查詢。它是以 布爾查詢 的方式來實現的。布爾查詢 接受如下參數：
must等同於ANDmust_not等同於NOTshould等同於OR
打比方，如果我想要查詢這樣類型的書：書名包含 ElasticSearch 或者（OR） Solr，並且（AND）它的作者是 Clinton Gormley 不是（NOT）Radu Gheorge
POST /bookdb_index/book/_search { "query": { "bool": { "must": { "bool" : { "should": [ { "match": { "title": "Elasticsearch" }}, { "match": { "title": "Solr" }} ] } }, "must": { "match": { "authors": "clinton gormely" }}, "must_not": { "match": {"authors": "radu gheorge" }} } } } [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "1", "_score": 0.3672021, "_source": { "title": "Elasticsearch: The Definitive Guide", "authors": [ "clinton gormley", "zachary tong" ], "summary": "A distibuted real-time search and analytics engine", "publish_date": "2015-02-07", "num_reviews": 20, "publisher": "oreilly" } } ]
注：正如你所看到的，布爾查詢 可以包裝任何其他查詢類型，包括其他布爾查詢，以創建任意複雜或深度嵌套的查詢。
5. 模糊（Fuzzy）查詢
在進行匹配和多項匹配時，可以啟用模糊匹配來捕捉拼寫錯誤，模糊度是基於原始單詞的編輯距離來指定的。
POST /bookdb_index/book/_search { "query": { "multi_match" : { "query" : "comprihensiv guide", "fields": ["title", "summary"], "fuzziness": "AUTO" } }, "_source": ["title", "summary", "publish_date"], "size": 1 } [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "4", "_score": 0.5961596, "_source": { "summary": "Comprehensive guide to implementing a scalable search engine using Apache Solr", "title": "Solr in Action", "publish_date": "2014-04-05" } } ]
注：當術語長度大於 5 個字元時，AUTO 的模糊值等同於指定值 「2」。但是，80％ 拼寫錯誤的編輯距離為 1，所以，將模糊值設置為 1 可能會提高您的整體搜索性能。更多詳細資訊，請參閱Elasticsearch指南中的「排版和拼寫錯誤」（Typos and Misspellings）。
6. 通配符（Wildcard）查詢
通配符查詢 允許你指定匹配的模式，而不是整個術語。
？匹配任何字元*匹配零個或多個字元。
例如，要查找名稱以字母』t』開頭的所有作者的記錄：
POST /bookdb_index/book/_search { "query": { "wildcard" : { "authors" : "t*" } }, "_source": ["title", "authors"], "highlight": { "fields" : { "authors" : {} } } } [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "1", "_score": 1, "_source": { "title": "Elasticsearch: The Definitive Guide", "authors": [ "clinton gormley", "zachary tong" ] }, "highlight": { "authors": [ "zachary <em>tong</em>" ] } }, { "_index": "bookdb_index", "_type": "book", "_id": "2", "_score": 1, "_source": { "title": "Taming Text: How to Find, Organize, and Manipulate It", "authors": [ "grant ingersoll", "thomas morton", "drew farris" ] }, "highlight": { "authors": [ "<em>thomas</em> morton" ] } }, { "_index": "bookdb_index", "_type": "book", "_id": "4", "_score": 1, "_source": { "title": "Solr in Action", "authors": [ "trey grainger", "timothy potter" ] }, "highlight": { "authors": [ "<em>trey</em> grainger", "<em>timothy</em> potter" ] } } ]
7. 正則（Regexp）查詢
正則查詢 讓你可以使用比 通配符查詢 更複雜的模式進行查詢：
POST /bookdb_index/book/_search { "query": { "regexp" : { "authors" : "t[a-z]*y" } }, "_source": ["title", "authors"], "highlight": { "fields" : { "authors" : {} } } } [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "4", "_score": 1, "_source": { "title": "Solr in Action", "authors": [ "trey grainger", "timothy potter" ] }, "highlight": { "authors": [ "<em>trey</em> grainger", "<em>timothy</em> potter" ] } } ]
8. 短語匹配(Match Phrase)查詢
短語匹配查詢 要求在請求字元串中的所有查詢項必須都在文檔中存在，文中順序也得和請求字元串一致，且彼此相連。默認情況下，查詢項之間必須緊密相連，但可以設置 slop 值來指定查詢項之間可以分隔多遠的距離，結果仍將被當作一次成功的匹配。
POST /bookdb_index/book/_search { "query": { "multi_match" : { "query": "search engine", "fields": ["title", "summary"], "type": "phrase", "slop": 3 } }, "_source": [ "title", "summary", "publish_date" ] } [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "4", "_score": 0.22327082, "_source": { "summary": "Comprehensive guide to implementing a scalable search engine using Apache Solr", "title": "Solr in Action", "publish_date": "2014-04-05" } }, { "_index": "bookdb_index", "_type": "book", "_id": "1", "_score": 0.16113183, "_source": { "summary": "A distibuted real-time search and analytics engine", "title": "Elasticsearch: The Definitive Guide", "publish_date": "2015-02-07" } } ]
注：在上述例子中，對於非整句類型的查詢，_id 為 1 的文檔一般會比 _id 為 4 的文檔得分高，結果位置也更靠前，因為它的欄位長度較短，但是對於 短語匹配類型 查詢，由於查詢項之間的接近程度是一個計算因素，因此 _id 為 4 的文檔得分更高。
9. 短語前綴（Match Phrase Prefix）查詢
短語前綴式查詢 能夠進行 即時搜索（search-as-you-type） 類型的匹配，或者說提供一個查詢時的初級自動補全功能，無需以任何方式準備你的數據。和 match_phrase 查詢類似，它接收slop 參數（用來調整單詞順序和不太嚴格的相對位置）和 max_expansions 參數（用來限制查詢項的數量，降低對資源需求的強度）。
POST /bookdb_index/book/_search { "query": { "match_phrase_prefix" : { "summary": { "query": "search en", "slop": 3, "max_expansions": 10 } } }, "_source": [ "title", "summary", "publish_date" ] } [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "4", "_score": 0.5161346, "_source": { "summary": "Comprehensive guide to implementing a scalable search engine using Apache Solr", "title": "Solr in Action", "publish_date": "2014-04-05" } }, { "_index": "bookdb_index", "_type": "book", "_id": "1", "_score": 0.37248808, "_source": { "summary": "A distibuted real-time search and analytics engine", "title": "Elasticsearch: The Definitive Guide", "publish_date": "2015-02-07" } } ]
注：採用 查詢時即時搜索 具有較大的性能成本。更好的解決方案是採用 索引時即時搜索。更多資訊，請查看 自動補齊介面（Completion Suggester API） 或 邊緣分詞器（Edge-Ngram filters）的用法。
10. 查詢字元串（Query String）
查詢字元串 類型（query_string）的查詢提供了一個方法，用簡潔的簡寫語法來執行 多匹配查詢、 布爾查詢 、 提權查詢、 模糊查詢、 通配符查詢、 正則查詢 和範圍查詢。下面的例子中，我們在那些作者是 「grant ingersoll」 或 「tom morton」 的某本書當中，使用查詢項 「search algorithm」 進行一次模糊查詢，搜索全部欄位，但給 summary 的權重提升 2 倍。
POST /bookdb_index/book/_search { "query": { "query_string" : { "query": "(saerch~1 algorithm~1) AND (grant ingersoll) OR (tom morton)", "fields": ["_all", "summary^2"] } }, "_source": [ "title", "summary", "authors" ], "highlight": { "fields" : { "summary" : {} } } } [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "2", "_score": 0.14558059, "_source": { "summary": "organize text using approaches such as full-text search, proper name recognition, clustering, tagging, information extraction, and summarization", "title": "Taming Text: How to Find, Organize, and Manipulate It", "authors": [ "grant ingersoll", "thomas morton", "drew farris" ] }, "highlight": { "summary": [ "organize text using approaches such as full-text <em>search</em>, proper name recognition, clustering, tagging, information extraction, and summarization" ] } } ]
11. 簡單查詢字元串（Simple Query String）
簡單請求字元串 類型（simple_query_string）的查詢是請求字元串類型（query_string）查詢的一個版本，它更適合那種僅暴露給用戶一個簡單搜索框的場景；因為它用 +/\|/- 分別替換了 AND/OR/NOT，並且自動丟棄了請求中無效的部分，不會在用戶出錯時，拋出異常。
POST /bookdb_index/book/_search { "query": { "simple_query_string" : { "query": "(saerch~1 algorithm~1) + (grant ingersoll) | (tom morton)", "fields": ["_all", "summary^2"] } }, "_source": [ "title", "summary", "authors" ], "highlight": { "fields" : { "summary" : {} } } }
12. 詞條（Term）/多詞條（Terms）查詢
以上例子均為 full-text(全文檢索) 的示例。有時我們對結構化查詢更感興趣，希望得到更準確的匹配並返回結果，詞條查詢 和 多詞條查詢 可幫我們實現。在下面的例子中，我們要在索引中找到所有由 Manning 出版的圖書。
POST /bookdb_index/book/_search { "query": { "term" : { "publisher": "manning" } }, "_source" : ["title","publish_date","publisher"] } [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "2", "_score": 1.2231436, "_source": { "publisher": "manning", "title": "Taming Text: How to Find, Organize, and Manipulate It", "publish_date": "2013-01-24" } }, { "_index": "bookdb_index", "_type": "book", "_id": "3", "_score": 1.2231436, "_source": { "publisher": "manning", "title": "Elasticsearch in Action", "publish_date": "2015-12-03" } }, { "_index": "bookdb_index", "_type": "book", "_id": "4", "_score": 1.2231436, "_source": { "publisher": "manning", "title": "Solr in Action", "publish_date": "2014-04-05" } } ]
可使用詞條關鍵字來指定多個詞條，將搜索項用數組傳入。
{
"query": {
"terms" : {
"publisher": ["oreilly", "packt"]
}
}
}
13. 詞條（Term）查詢 – 排序（Sorted）
詞條查詢 的結果（和其他查詢結果一樣）可以被輕易排序，多級排序也被允許：
POST /bookdb_index/book/_search { "query": { "term" : { "publisher": "manning" } }, "_source" : ["title","publish_date","publisher"], "sort": [ { "publish_date": {"order":"desc"}}, { "title": { "order": "desc" }} ] } [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "3", "_score": null, "_source": { "publisher": "manning", "title": "Elasticsearch in Action", "publish_date": "2015-12-03" }, "sort": [ 1449100800000, "in" ] }, { "_index": "bookdb_index", "_type": "book", "_id": "4", "_score": null, "_source": { "publisher": "manning", "title": "Solr in Action", "publish_date": "2014-04-05" }, "sort": [ 1396656000000, "solr" ] }, { "_index": "bookdb_index", "_type": "book", "_id": "2", "_score": null, "_source": { "publisher": "manning", "title": "Taming Text: How to Find, Organize, and Manipulate It", "publish_date": "2013-01-24" }, "sort": [ 1358985600000, "to" ] } ]
14. 範圍查詢
另一個結構化查詢的例子是 範圍查詢。在這個例子中，我們要查找 2015 年出版的書。
POST /bookdb_index/book/_search { "query": { "range" : { "publish_date": { "gte": "2015-01-01", "lte": "2015-12-31" } } }, "_source" : ["title","publish_date","publisher"] } [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "1", "_score": 1, "_source": { "publisher": "oreilly", "title": "Elasticsearch: The Definitive Guide", "publish_date": "2015-02-07" } }, { "_index": "bookdb_index", "_type": "book", "_id": "3", "_score": 1, "_source": { "publisher": "manning", "title": "Elasticsearch in Action", "publish_date": "2015-12-03" } } ]
注：範圍查詢 用於日期、數字和字元串類型的欄位。
15. 過濾(Filtered)查詢
過濾查詢允許你可以過濾查詢結果。對於我們的例子中，要在標題或摘要中檢索一些書，查詢項為 Elasticsearch，但我們又想篩出那些僅有 20 個以上評論的。
POST /bookdb_index/book/_search { "query": { "filtered": { "query" : { "multi_match": { "query": "elasticsearch", "fields": ["title","summary"] } }, "filter": { "range" : { "num_reviews": { "gte": 20 } } } } }, "_source" : ["title","summary","publisher", "num_reviews"] } [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "1", "_score": 0.5955761, "_source": { "summary": "A distibuted real-time search and analytics engine", "publisher": "oreilly", "num_reviews": 20, "title": "Elasticsearch: The Definitive Guide" } } ]
注：過濾查詢 並不強制它作用於其上的查詢必須存在。如果未指定查詢，match_all 基本上會返回索引內的全部文檔。實際上，過濾只在第一次運行，以減少所需的查詢面積，並且，在第一次使用後過濾會被快取，大大提高了性能。
更新：過濾查詢 將在 ElasticSearch 5 中移除，使用 布爾查詢 替代。 下面有個例子使用 布爾查詢 重寫上面的例子：
POST /bookdb_index/book/_search { "query": { "bool": { "must" : { "multi_match": { "query": "elasticsearch", "fields": ["title","summary"] } }, "filter": { "range" : { "num_reviews": { "gte": 20 } } } } }, "_source" : ["title","summary","publisher", "num_reviews"] }
在後續的例子中，我們將會把它使用在 多重過濾 中。
16. 多重過濾（Multiple Filters）
多重過濾 可以結合 布爾查詢 使用，下一個例子中，過濾查詢決定只返回那些包含至少20條評論，且必須在 2015 年前出版，且由 O』Reilly 出版的結果。
POST /bookdb_index/book/_search { "query": { "filtered": { "query" : { "multi_match": { "query": "elasticsearch", "fields": ["title","summary"] } }, "filter": { "bool": { "must": { "range" : { "num_reviews": { "gte": 20 } } }, "must_not": { "range" : { "publish_date": { "lte": "2014-12-31" } } }, "should": { "term": { "publisher": "oreilly" } } } } } }, "_source" : ["title","summary","publisher", "num_reviews", "publish_date"] } [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "1", "_score": 0.5955761, "_source": { "summary": "A distibuted real-time search and analytics engine", "publisher": "oreilly", "num_reviews": 20, "title": "Elasticsearch: The Definitive Guide", "publish_date": "2015-02-07" } } ]
17. 作用分值: 域值（Field Value）因子
也許在某種情況下，你想把文檔中的某個特定域作為計算相關性分值的一個因素，比較典型的場景是你想根據普及程度來提高一個文檔的相關性。在我們的示例中，我們想把最受歡迎的書（基於評論數判斷）的權重進行提高，可使用 field_value_factor 用以影響分值。
POST /bookdb_index/book/_search { "query": { "function_score": { "query": { "multi_match" : { "query" : "search engine", "fields": ["title", "summary"] } }, "field_value_factor": { "field" : "num_reviews", "modifier": "log1p", "factor" : 2 } } }, "_source": ["title", "summary", "publish_date", "num_reviews"] } [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "1", "_score": 0.44831306, "_source": { "summary": "A distibuted real-time search and analytics engine", "num_reviews": 20, "title": "Elasticsearch: The Definitive Guide", "publish_date": "2015-02-07" } }, { "_index": "bookdb_index", "_type": "book", "_id": "4", "_score": 0.3718407, "_source": { "summary": "Comprehensive guide to implementing a scalable search engine using Apache Solr", "num_reviews": 23, "title": "Solr in Action", "publish_date": "2014-04-05" } }, { "_index": "bookdb_index", "_type": "book", "_id": "3", "_score": 0.046479136, "_source": { "summary": "build scalable search applications using Elasticsearch without having to do complex low-level programming or understand advanced data science algorithms", "num_reviews": 18, "title": "Elasticsearch in Action", "publish_date": "2015-12-03" } }, { "_index": "bookdb_index", "_type": "book", "_id": "2", "_score": 0.041432835, "_source": { "summary": "organize text using approaches such as full-text search, proper name recognition, clustering, tagging, information extraction, and summarization", "num_reviews": 12, "title": "Taming Text: How to Find, Organize, and Manipulate It", "publish_date": "2013-01-24" } } ]
注1: 我們可能剛運行了一個常規的 multi_match (多匹配)查詢，並對 num_reviews 域進行了排序，這讓我們失去了評估相關性分值的好處。
注2: 有大量的附加參數可用來調整提升原始相關性分值效果的程度，比如 modifier, factor, boost_mode 等等，至於細節可在 Elasticsearch 指南中探索。
18. 作用分值: 衰變（Decay）函數
假設不想使用域值做遞增提升，而你有一個理想目標值，並希望用這個加權因子來對這個離你較遠的目標值進行衰減。有個典型的用途是基於經緯度、價格或日期等數值域的提升。在如下的例子中，我們查找在2014年6月左右出版的，查詢項是 search engines 的書。
POST /bookdb_index/book/_search { "query": { "function_score": { "query": { "multi_match" : { "query" : "search engine", "fields": ["title", "summary"] } }, "functions": [ { "exp": { "publish_date" : { "origin": "2014-06-15", "offset": "7d", "scale" : "30d" } } } ], "boost_mode" : "replace" } }, "_source": ["title", "summary", "publish_date", "num_reviews"] } [Results] "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "4", "_score": 0.27420625, "_source": { "summary": "Comprehensive guide to implementing a scalable search engine using Apache Solr", "num_reviews": 23, "title": "Solr in Action", "publish_date": "2014-04-05" } }, { "_index": "bookdb_index", "_type": "book", "_id": "1", "_score": 0.005920768, "_source": { "summary": "A distibuted real-time search and analytics engine", "num_reviews": 20, "title": "Elasticsearch: The Definitive Guide", "publish_date": "2015-02-07" } }, { "_index": "bookdb_index", "_type": "book", "_id": "2", "_score": 0.000011564, "_source": { "summary": "organize text using approaches such as full-text search, proper name recognition, clustering, tagging, information extraction, and summarization", "num_reviews": 12, "title": "Taming Text: How to Find, Organize, and Manipulate It", "publish_date": "2013-01-24" } }, { "_index": "bookdb_index", "_type": "book", "_id": "3", "_score": 0.0000059171475, "_source": { "summary": "build scalable search applications using Elasticsearch without having to do complex low-level programming or understand advanced data science algorithms", "num_reviews": 18, "title": "Elasticsearch in Action", "publish_date": "2015-12-03" } } ]
19. 函數分值: 腳本評分
當內置的評分函數無法滿足你的需求時，還可以用 Groovy 腳本。在我們的例子中，想要指定一個腳本，能在決定把 num_reviews 的因子計算多少之前，先將 publish_date 考慮在內。因為很新的書也許不會有評論，分值不應該被懲罰。
評分腳本如下：
publish_date = doc['publish_date'].value num_reviews = doc['num_reviews'].value if (publish_date > Date.parse('yyyy-MM-dd', threshold).getTime()) { my_score = Math.log(2.5 + num_reviews) } else { my_score = Math.log(1 + num_reviews) } return my_score
在 script_score 參數內動態調用評分腳本：
POST /bookdb_index/book/_search { "query": { "function_score": { "query": { "multi_match" : { "query" : "search engine", "fields": ["title", "summary"] } }, "functions": [ { "script_score": { "params" : { "threshold": "2015-07-30" }, "script": "publish_date = doc['publish_date'].value; num_reviews = doc['num_reviews'].value; if (publish_date > Date.parse('yyyy-MM-dd', threshold).getTime()) { return log(2.5 + num_reviews) }; return log(1 + num_reviews);" } } ] } }, "_source": ["title", "summary", "publish_date", "num_reviews"] } [Results] "hits": { "total": 4, "max_score": 0.8463001, "hits": [ { "_index": "bookdb_index", "_type": "book", "_id": "1", "_score": 0.8463001, "_source": { "summary": "A distibuted real-time search and analytics engine", "num_reviews": 20, "title": "Elasticsearch: The Definitive Guide", "publish_date": "2015-02-07" } }, { "_index": "bookdb_index", "_type": "book", "_id": "4", "_score": 0.7067348, "_source": { "summary": "Comprehensive guide to implementing a scalable search engine using Apache Solr", "num_reviews": 23, "title": "Solr in Action", "publish_date": "2014-04-05" } }, { "_index": "bookdb_index", "_type": "book", "_id": "3", "_score": 0.08952084, "_source": { "summary": "build scalable search applications using Elasticsearch without having to do complex low-level programming or understand advanced data science algorithms", "num_reviews": 18, "title": "Elasticsearch in Action", "publish_date": "2015-12-03" } }, { "_index": "bookdb_index", "_type": "book", "_id": "2", "_score": 0.07602123, "_source": { "summary": "organize text using approaches such as full-text search, proper name recognition, clustering, tagging, information extraction, and summarization", "num_reviews": 12, "title": "Taming Text: How to Find, Organize, and Manipulate It", "publish_date": "2013-01-24" } } ] }
注1: 要在 Elasticsearch 實例中使用動態腳本，必須在 config/elasticsearch.yaml 文件中啟用它；也可以使用存儲在 Elasticsearch 伺服器上的腳本。建議看看 Elasticsearch 指南文檔獲取更多資訊。
注2: 因 JSON 不能包含嵌入式換行符，請使用分號來分割語句。
