こんにちは。ニフティライフスタイルの中野です。
この記事はニフティグループ Advent Calendar 2018の7日目の記事です。
昨日は @hicka04 さんで「社内で勉強会をやるときに気をつけていること」でした！
ニフティのWEBサービスでは、一部サービスのサイト内検索やログ可視化などで Elasticsearch を利用しています。
以前投稿した ElasticsearchのField Collapsingで検索結果をグルーピングする について、Elasticsearch 6.4 から Second level of collapsing という機能が追加されていましたので使ってみたいと思います。
Field Collapsing はその名のとおり検索結果を「折りたたんで」くれる機能で、検索結果をグルーピングして SQL の GROUP BY のような操作をすることができます。
Elasticsearch 6.4 から追加された Second level of collapsing では、グルーピング結果をさらにもう一段階まとめて取得することができるようです。
まずはサンプルをみてみましょう。
サンプル
データ
サンプルデータとして、青空文庫さんの作品リストcsvを使用させて頂いています。
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$ head -2 list_person_all_utf8.csv 人物ID,著者名,作品ID,作品名,仮名遣い種別,翻訳者名等,入力者名,校正者名,状態,状態の開始日,底本名,出版社名,入力に使用した版,校正に使用した版 001257,"アーヴィング ワシントン",056078,"駅伝馬車",旧字旧仮名,"高垣 松雄","雀","小林繁雄",公開,2013-09-20,"スケッチ・ブック","岩波文庫、岩波書店","2010（平成22）年2月23日第31刷","1992（平成4）年2月26日第30刷" |
このデータを Elasticsearch に投入し、Field Collapsing でグルーピングした検索結果と、さらに Second level of collapsing を使った検索結果を比較してみます。
Field Collapsing の検索結果
作品リストを著者ごとにまとめたサンプルです。
それぞれの著者の下に inner_hits として作品が並んでいます。
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{ "took" : 5, "timed_out" : false, "_shards" : { "total" : 5, "successful" : 5, "skipped" : 0, "failed" : 0 }, "hits" : { "total" : 16088, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "HUIPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "会津 八一" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 9, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "HUIPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { "id" : "046513", "title" : "支那の明器", "author" : "会津 八一", "publisher" : "作品社" } }, { "_index" : "aozora", "_type" : "books", "_id" : "GkIPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { "id" : "057975", "title" : "音楽に就いて", "author" : "会津 八一", "publisher" : "中央公論社" } }, { "_index" : "aozora", "_type" : "books", "_id" : "IEIPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { "id" : "057978", "title" : "少年少女におくる言葉", "author" : "会津 八一", "publisher" : "中央公論社" } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "JkIPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "青空文庫 " ] }, "inner_hits" : { "books" : { "hits" : { "total" : 1, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "JkIPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { "id" : "056572", "title" : "青空文庫の提案", "author" : "青空文庫 ", "publisher" : "" } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "J0IPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "青野 季吉" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 1, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "J0IPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { "id" : "052214", "title" : "百万人のそして唯一人の文学", "author" : "青野 季吉", "publisher" : "筑摩書房" } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "K0IPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "秋田 滋" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 7, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "K0IPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { "id" : "047074", "title" : "親ごころ", "author" : "秋田 滋", "publisher" : "改造文庫、改造社出版" } }, { "_index" : "aozora", "_type" : "books", "_id" : "LkIPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { "id" : "047076", "title" : "狂人日記", "author" : "秋田 滋", "publisher" : "暁書房" } }, { "_index" : "aozora", "_type" : "books", "_id" : "MEIPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { "id" : "043866", "title" : "初雪", "author" : "秋田 滋", "publisher" : "改造文庫、改造社出版" } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "O0IPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "芥川 竜之介" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 375, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "O0IPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { "id" : "003804", "title" : "悪魔", "author" : "芥川 竜之介", "publisher" : "筑摩書房" } }, { "_index" : "aozora", "_type" : "books", "_id" : "V0IPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { "id" : "000174", "title" : "馬の脚", "author" : "芥川 竜之介", "publisher" : "ちくま文庫、筑摩書房" } }, { "_index" : "aozora", "_type" : "books", "_id" : "YkIPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { "id" : "000123", "title" : "大川の水", "author" : "芥川 竜之介", "publisher" : "角川文庫、角川書店" } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "DEIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "伊丹 万作" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 23, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "DEIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { "id" : "001194", "title" : "一つの世界 ――私信――", "author" : "伊丹 万作", "publisher" : "筑摩書房" } }, { "_index" : "aozora", "_type" : "books", "_id" : "z0IPjWcBtkR6x7Gbkrx4", "_score" : 1.0, "_source" : { "id" : "043868", "title" : "映画と民族性", "author" : "伊丹 万作", "publisher" : "筑摩書房" } }, { "_index" : "aozora", "_type" : "books", "_id" : "0UIPjWcBtkR6x7Gbkrx4", "_score" : 1.0, "_source" : { "id" : "043869", "title" : "映画の普及力とは", "author" : "伊丹 万作", "publisher" : "筑摩書房" } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "FUIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "伊藤 左千夫" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 30, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "FUIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { "id" : "057444", "title" : "井戸", "author" : "伊藤 左千夫", "publisher" : "日本図書センター" } }, { "_index" : "aozora", "_type" : "books", "_id" : "FkIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { "id" : "056526", "title" : "落穂", "author" : "伊藤 左千夫", "publisher" : "アイドル・ブックス、ポプラ社" } }, { "_index" : "aozora", "_type" : "books", "_id" : "HkIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { "id" : "057469", "title" : "子規と和歌", "author" : "伊藤 左千夫", "publisher" : "増進会出版社" } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "NEIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "伊藤 信二" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 1, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "NEIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { "id" : "054099", "title" : "冬のしぶき ――母親から獄中の息子に――", "author" : "伊藤 信二", "publisher" : "新日本出版社" } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "NkIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "伊東 忠太" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 5, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "NkIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { "id" : "046334", "title" : "建築の本義", "author" : "伊東 忠太", "publisher" : "萬里閣書房" } }, { "_index" : "aozora", "_type" : "books", "_id" : "N0IPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { "id" : "046335", "title" : "国語尊重", "author" : "伊東 忠太", "publisher" : "萬里閣書房" } }, { "_index" : "aozora", "_type" : "books", "_id" : "OEIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { "id" : "046336", "title" : "日本建築の発達と地震", "author" : "伊東 忠太", "publisher" : "萬里閣書房" } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "S0IPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "伊藤 野枝" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 74, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "S0IPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { "id" : "046560", "title" : "少数と多数", "author" : "伊藤 野枝", "publisher" : "學藝書林" } }, { "_index" : "aozora", "_type" : "books", "_id" : "T0IPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { "id" : "057001", "title" : "書簡 大杉栄宛 （一九一六年五月三一日）", "author" : "伊藤 野枝", "publisher" : "學藝書林" } }, { "_index" : "aozora", "_type" : "books", "_id" : "U0IPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { "id" : "057005", "title" : "書簡 大杉栄宛 （一九一六年五月二七日）", "author" : "伊藤 野枝", "publisher" : "學藝書林" } } ] } } } } ] } } |
Second level of collapsing の検索結果
作品リストを著者ごとにまとめたあとに、Second level of collapsing でさらに出版社ごとにまとめたサンプルです。
それぞれの著者の下にある inner_hits が、さらに出版社ごとにまとまっています。
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{ "took" : 15, "timed_out" : false, "_shards" : { "total" : 5, "successful" : 5, "skipped" : 0, "failed" : 0 }, "hits" : { "total" : 16088, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "HUIPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "会津 八一" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 9, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "HUIPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "作品社" ] } }, { "_index" : "aozora", "_type" : "books", "_id" : "GkIPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "中央公論社" ] } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "JkIPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "青空文庫 " ] }, "inner_hits" : { "books" : { "hits" : { "total" : 1, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "JkIPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "" ] } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "J0IPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "青野 季吉" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 1, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "J0IPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "筑摩書房" ] } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "K0IPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "秋田 滋" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 7, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "K0IPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "改造文庫、改造社出版" ] } }, { "_index" : "aozora", "_type" : "books", "_id" : "LkIPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "暁書房" ] } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "O0IPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "芥川 竜之介" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 375, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "O0IPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "筑摩書房" ] } }, { "_index" : "aozora", "_type" : "books", "_id" : "V0IPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "ちくま文庫、筑摩書房" ] } }, { "_index" : "aozora", "_type" : "books", "_id" : "YkIPjWcBtkR6x7GbkbCk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "角川文庫、角川書店" ] } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "DEIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "伊丹 万作" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 23, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "DEIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "筑摩書房" ] } }, { "_index" : "aozora", "_type" : "books", "_id" : "1EIPjWcBtkR6x7Gbkrx4", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "作品社" ] } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "FUIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "伊藤 左千夫" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 30, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "FUIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "日本図書センター" ] } }, { "_index" : "aozora", "_type" : "books", "_id" : "FkIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "アイドル・ブックス、ポプラ社" ] } }, { "_index" : "aozora", "_type" : "books", "_id" : "HkIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "増進会出版社" ] } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "NEIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "伊藤 信二" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 1, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "NEIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "新日本出版社" ] } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "NkIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "伊東 忠太" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 5, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "NkIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "萬里閣書房" ] } } ] } } } }, { "_index" : "aozora", "_type" : "books", "_id" : "S0IPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "author" : [ "伊藤 野枝" ] }, "inner_hits" : { "books" : { "hits" : { "total" : 74, "max_score" : 1.0, "hits" : [ { "_index" : "aozora", "_type" : "books", "_id" : "S0IPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "學藝書林" ] } }, { "_index" : "aozora", "_type" : "books", "_id" : "bUIPjWcBtkR6x7GbkbGk", "_score" : 1.0, "_source" : { }, "fields" : { "publisher" : [ "作品社" ] } } ] } } } } ] } } |
使い方
次に、ドキュメント に従って Second level of collapsing の使い方を確認したいと思います。
Second level of collapsing
グルーピング結果をさらにグルーピングするためには、collapse 句内の inner_hits に collapse 句を追加します。
追加した collapse 句の中では、通常の Field Collapsing と同じように、グルーピングのキーとなるフィールド名を filed に指定します。
下記のクエリでは、aozora というインデックスを検索条件なしで取得して、検索結果を author というフィールドの値ごとにグルーピングし、それをさらに publisher でグルーピングしています。
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GET /aozora/_search { "query": { "match_all": {} }, "collapse": { "field": "author", "inner_hits": { "name": "books", "size": 3, "collapse": { "field": "publisher" } } } } |
グループの展開
通常の Field Collapsing では inner_hits 句を追加することで、各グループに含まれるレコードを検索結果に含めることができましたが、残念ながら Second level of collapsing でさらにグルーピングした内容を inner_hits で取得することはできないようです。
Second level of collapsing の基本的な使い方については、以上となります。
まとめ
Second level of collapsing はいかがでしたでしょうか。
二重にグルーピングすることで、WEBサイトやECサービスでの検索結果の一覧性向上や、Kibanaでのログ可視化にも役立てることができそうですね。
弊社の提供するニフティ不動産やニフティアルバイト等の横断検索サービスでも、Elasticsearchの便利な検索機能を活用して利用者様に想像以上の体験を提供できるよう、改善していきたいと思います。
明日は @kanishionori さんがinput要素をCSSだけでいじり倒してくれるそうです!お楽しみに!
