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【AWS re:Invent 2025】OpenSearchのレキシカル検索（キーワード検索）を試してみた

【AWS re:Invent 2025】OpenSearchのレキシカル検索（キーワード検索）を試してみた

AWS re:Invent 2025
Amazon OpenSearch Service
FacebookHatena blogX
2026.01.06

目次

  1. この記事でやること / やらないこと
  2. レキシカル検索（キーワード検索）とは
  3. 手を動かす：Dev Toolsで確認と検索
  4. レキシカル検索の限界
  5. まとめ

この記事でやること / やらないこと

この記事は、AWS re:Invent 2025 のワークショップで学んだ OpenSearch のレキシカル検索を、自分の環境で再現して理解を深めた記録です。

やったこと

  1. AWS OpenSearch Service でドメインを作成（t3.small / 1ノード構成）
  2. Dev Tools で demostore-search-index の状態確認（mapping / 件数 / ドキュメント構造）
  3. 自作の50件サンプルデータを投入（ワークショップとは別に用意）
  4. match クエリ（BM25）でキーワード検索を実行し、結果を分析

省略したこと

  • 環境構築・ログイン手順の詳細
  • VPC 内配置などの本番向け設定

補足：検証目的のため、パブリックアクセス可能な構成で実施しました。実運用では セキュリティの観点からVPC 内配置 を基本に考えてください。

レキシカル検索（キーワード検索）とは

レキシカル検索の概要

レキシカル検索（キーワード検索）とは、テキスト内で 単語（トークン）の一致 を軸に検索する手法です。

  • 製品名・部品番号・型番など、明確なキーワード を探すケースに強い
  • 例：black jacket for men → black / jacket / men の一致を評価

BM25 によるスコア計算

今回は関連度スコア計算に BM25（Best Matching 25） を使います。

要素 説明 スコアへの影響
一致する語の数 検索ワードのうち何語マッチしたか 多いほど高スコア
語の出現頻度（TF） その文書内で何回出現するか 多いほど高スコア（ただし上限あり）
文書全体での希少性（IDF） 全文書の中でどれだけレアか 珍しい語ほど高スコア

手を動かす：Dev Toolsで確認と検索

1. インデックス作成

Dev Tools（OpenSearch Dashboards → 左メニュー → Dev Tools）で以下を実行します。

PUT demostore-search-index
{
  "settings": {
    "number_of_shards": 1,
    "number_of_replicas": 0
  },
  "mappings": {
    "properties": {
      "product_id": { "type": "keyword" },
      "product_name": { "type": "text" },
      "product_description": { "type": "text" },
      "category": { "type": "keyword" },
      "price": { "type": "float" },
      "color": { "type": "keyword" },
      "gender": { "type": "keyword" }
    }
  }
}

create_index

パラメータ 意味
number_of_shards データを分割する数（1 = 分割なし）
number_of_replicas 複製の数（0 = バックアップなし、検証用）
product_id 商品ID（keyword型：完全一致検索用）
product_name 商品名（text型：全文検索用）
product_description 商品説明（text型：全文検索用）
category カテゴリ（keyword型：フィルタ用）
price 価格（float型：数値）
color 色（keyword型：フィルタ用）
gender 性別（keyword型：フィルタ用）

2. サンプルデータ投入（50件）

以下の Bulk API で50件の商品データを投入します。

POST demostore-search-index/_bulk
{"index":{}}
{"product_id":"1","product_name":"Classic Black Leather Jacket","product_description":"Premium black leather jacket for men. Perfect for casual and formal occasions.","category":"jackets","price":199.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"2","product_name":"Men's Black Running Shoes","product_description":"Lightweight black running shoes for men. Breathable mesh upper.","category":"shoes","price":89.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"3","product_name":"Women's Red Backpack","product_description":"Stylish red backpack for women. Multiple compartments for travel.","category":"bags","price":59.99,"color":"red","gender":"women"}
{"index":{}}
{"product_id":"4","product_name":"Black Denim Jacket","product_description":"Trendy black denim jacket for men. Classic fit with button closure.","category":"jackets","price":79.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"5","product_name":"Silver Bracelet Set","product_description":"Elegant silver bracelets for men. Set of 3 designs.","category":"accessories","price":45.99,"color":"silver","gender":"men"}
{"index":{}}
{"product_id":"6","product_name":"Women's Black Tote Bag","product_description":"Spacious black tote bag for women. Faux leather with gold accents.","category":"bags","price":69.99,"color":"black","gender":"women"}
{"index":{}}
{"product_id":"7","product_name":"Men's Black Wool Coat","product_description":"Elegant black wool coat for men. Perfect for winter formal occasions.","category":"jackets","price":299.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"8","product_name":"Black Hiking Boots","product_description":"Durable black hiking boots for men. Waterproof with ankle support.","category":"shoes","price":149.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"9","product_name":"Women's Black Leather Jacket","product_description":"Stylish black leather jacket for women. Slim fit with zipper.","category":"jackets","price":189.99,"color":"black","gender":"women"}
{"index":{}}
{"product_id":"10","product_name":"Black Canvas Sneakers","product_description":"Classic black canvas sneakers for men. Comfortable everyday black shoes.","category":"shoes","price":49.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"11","product_name":"Men's Navy Blazer","product_description":"Professional navy blazer jacket for men. Perfect for business meetings.","category":"jackets","price":179.99,"color":"navy","gender":"men"}
{"index":{}}
{"product_id":"12","product_name":"Black Oxford Shoes","product_description":"Formal black oxford shoes for men. Genuine leather, perfect for suits.","category":"shoes","price":129.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"13","product_name":"Women's Denim Jacket","product_description":"Classic blue denim jacket for women. Vintage wash with brass buttons.","category":"jackets","price":69.99,"color":"blue","gender":"women"}
{"index":{}}
{"product_id":"14","product_name":"Black Sports Watch","product_description":"Digital black sports watch for men. Water resistant with multiple functions.","category":"accessories","price":79.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"15","product_name":"Men's Black Puffer Jacket","product_description":"Warm black puffer jacket for men. Lightweight down filling for cold weather.","category":"jackets","price":159.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"16","product_name":"Black Running Trainers","product_description":"High performance black running trainers for men. Extra cushioning for long runs.","category":"shoes","price":119.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"17","product_name":"Women's Red Heels","product_description":"Elegant red high heels for women. Perfect for parties and special occasions.","category":"shoes","price":89.99,"color":"red","gender":"women"}
{"index":{}}
{"product_id":"18","product_name":"Black Messenger Bag","product_description":"Professional black messenger bag for men. Multiple compartments for laptop.","category":"bags","price":79.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"19","product_name":"Men's Suede Jacket","product_description":"Premium brown suede jacket for men. Soft texture with classic design.","category":"jackets","price":219.99,"color":"brown","gender":"men"}
{"index":{}}
{"product_id":"20","product_name":"Black Loafers","product_description":"Comfortable black loafers for men. Slip-on design for easy wear.","category":"shoes","price":99.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"21","product_name":"Women's White Blouse","product_description":"Elegant white blouse for women. Perfect for office and casual wear.","category":"tops","price":49.99,"color":"white","gender":"women"}
{"index":{}}
{"product_id":"22","product_name":"Black Leather Wallet","product_description":"Genuine black leather wallet for men. Multiple card slots and coin pocket.","category":"accessories","price":45.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"23","product_name":"Men's Windbreaker Jacket","product_description":"Lightweight black windbreaker jacket for men. Perfect for outdoor activities.","category":"jackets","price":89.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"24","product_name":"Black Basketball Shoes","product_description":"Professional black basketball shoes for men. High top design with ankle support.","category":"shoes","price":139.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"25","product_name":"Women's Crossbody Bag","product_description":"Compact black crossbody bag for women. Adjustable strap with gold hardware.","category":"bags","price":59.99,"color":"black","gender":"women"}
{"index":{}}
{"product_id":"26","product_name":"Men's Quilted Jacket","product_description":"Stylish black quilted jacket for men. Diamond pattern with snap buttons.","category":"jackets","price":129.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"27","product_name":"Black Dress Shoes","product_description":"Classic black dress shoes for men. Perfect for weddings and formal events.","category":"shoes","price":109.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"28","product_name":"Women's Pink Sneakers","product_description":"Trendy pink sneakers for women. Lightweight with memory foam insole.","category":"shoes","price":69.99,"color":"pink","gender":"women"}
{"index":{}}
{"product_id":"29","product_name":"Black Sunglasses","product_description":"Stylish black sunglasses for men. UV protection with polarized lenses.","category":"accessories","price":59.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"30","product_name":"Men's Motorcycle Jacket","product_description":"Rugged black motorcycle jacket for men. Heavy duty leather with armor pockets.","category":"jackets","price":279.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"31","product_name":"Black Slip-On Shoes","product_description":"Casual black slip-on shoes for men. Elastic sides for easy on and off.","category":"shoes","price":59.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"32","product_name":"Women's Trench Coat","product_description":"Classic beige trench coat for women. Double breasted with belt.","category":"jackets","price":199.99,"color":"beige","gender":"women"}
{"index":{}}
{"product_id":"33","product_name":"Black Gym Bag","product_description":"Spacious black gym bag for men. Separate shoe compartment included.","category":"bags","price":49.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"34","product_name":"Men's Varsity Jacket","product_description":"Retro style black varsity jacket for men. Wool body with leather sleeves.","category":"jackets","price":149.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"35","product_name":"Black Chelsea Boots","product_description":"Sleek black chelsea boots for men. Elastic side panels with pull tab.","category":"shoes","price":159.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"36","product_name":"Women's Yoga Pants","product_description":"Comfortable black yoga pants for women. High waist with stretch fabric.","category":"bottoms","price":39.99,"color":"black","gender":"women"}
{"index":{}}
{"product_id":"37","product_name":"Black Tie","product_description":"Silk black tie for men. Perfect for formal occasions and business.","category":"accessories","price":29.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"38","product_name":"Men's Fleece Jacket","product_description":"Cozy black fleece jacket for men. Full zip with side pockets.","category":"jackets","price":79.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"39","product_name":"Black Tennis Shoes","product_description":"Professional black tennis shoes for men. Non-marking sole for court use.","category":"shoes","price":89.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"40","product_name":"Women's Shoulder Bag","product_description":"Elegant black shoulder bag for women. Quilted design with chain strap.","category":"bags","price":129.99,"color":"black","gender":"women"}
{"index":{}}
{"product_id":"41","product_name":"Men's Track Jacket","product_description":"Athletic black track jacket for men. Moisture wicking with reflective details.","category":"jackets","price":69.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"42","product_name":"Black Boat Shoes","product_description":"Classic black boat shoes for men. Leather upper with non-slip sole.","category":"shoes","price":79.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"43","product_name":"Women's Winter Boots","product_description":"Warm black winter boots for women. Faux fur lining with waterproof exterior.","category":"shoes","price":119.99,"color":"black","gender":"women"}
{"index":{}}
{"product_id":"44","product_name":"Black Belt","product_description":"Classic black leather belt for men. Silver buckle with adjustable size.","category":"accessories","price":35.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"45","product_name":"Men's Safari Jacket","product_description":"Adventure style khaki safari jacket for men. Multiple pockets for travel.","category":"jackets","price":139.99,"color":"khaki","gender":"men"}
{"index":{}}
{"product_id":"46","product_name":"Black Skate Shoes","product_description":"Durable black skate shoes for men. Reinforced toe cap with grip sole.","category":"shoes","price":74.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"47","product_name":"Women's Clutch Bag","product_description":"Glamorous black clutch bag for women. Perfect for evening events.","category":"bags","price":49.99,"color":"black","gender":"women"}
{"index":{}}
{"product_id":"48","product_name":"Men's Rain Jacket","product_description":"Waterproof black rain jacket for men. Packable design with hood.","category":"jackets","price":99.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"49","product_name":"Black Work Boots","product_description":"Heavy duty black work boots for men. Steel toe with oil resistant sole.","category":"shoes","price":129.99,"color":"black","gender":"men"}
{"index":{}}
{"product_id":"50","product_name":"Women's Cardigan","product_description":"Soft gray cardigan for women. Button front with ribbed cuffs.","category":"tops","price":59.99,"color":"gray","gender":"women"}

create_data

パラメータ 意味
_bulk 複数のドキュメントを一括登録するAPI
{"index":{}} 次の行のデータを登録する指示

3. 件数確認

GET demostore-search-index/_count

count_data

パラメータ 意味
_count インデックス内のドキュメント数を取得

4. match でレキシカル検索（BM25）

GET demostore-search-index/_search
{
  "query": {
    "match": {
      "product_description": "black jacket for men"
    }
  },
  "size": 20
}

lexical_search_black_jacket

パラメータ 意味
_search 検索を実行するAPI
query 検索条件を指定
match 全文検索（BM25でスコア計算）
product_description 検索対象のフィールド
"black jacket for men" 検索キーワード（単語に分割されて検索）
size 返す件数（デフォルトは10件）

5. 結果の分析

ポイント：上位15件はジャケット、16位以降に靴が混入

順位 スコア 商品名 カテゴリ 一致した語
1位 0.847 Men's Windbreaker Jacket jackets ✅ black jacket men (3語)
2位 0.845 Men's Rain Jacket jackets ✅ black jacket men (3語)
3-10位 0.78-0.81 各種ジャケット jackets ✅ 3語一致
11位 0.727 Men's Navy Blazer jackets ✅ jacket men (2語)
16位 0.326 Black Canvas Sneakers shoes ⚠️ black men (2語)
17位 0.295 Men's Black Running Shoes shoes ⚠️ black men (2語)

レキシカル検索の限界

1. 明確なキーワードがないと精度が落ちる

jacket を含まないクエリで検索

GET demostore-search-index/_search
{
  "query": {
    "match": {
      "product_description": "warm winter outerwear"
    }
  },
  "size": 10
}

lexical_search_warm_winter

結果

順位 スコア 商品名 カテゴリ 一致した語
1位 2.64 Women's Winter Boots shoes ⚠️ warm winter (2語)
2位 1.37 Men's Black Wool Coat jackets ✅ winter (1語)
3位 1.32 Men's Black Puffer Jacket jackets ✅ warm (1語)

問題：検索意図は「冬用アウター」だが、1位は冬用ブーツ

2. 同義語を理解できない

outerwear ≒ jacket, coat と理解できない
データに outerwear がないため 3件しかヒットしない

3. 検索意図を理解できない

ユーザーの意図: 冬に着る暖かい上着が欲しい
レキシカル検索: warm と winter を含むものを探す
結果: 冬用ブーツが1位になってしまう…

まとめ

特性 説明
✅ 強み 明確なキーワード（jacket、型番など）があれば正確
✅ BM25 一致する語が多いほどスコアが高い
⚠️ 限界 同義語・曖昧な表現には弱い
⚠️ 限界 検索意図を理解できない

検証結果

クエリ 結果
black jacket for men 上位15件がジャケット ✅
warm winter outerwear 1位が冬用ブーツ ⚠️

次のステップ

この限界を補うために セマンティック検索（意味検索） を導入して検証してみたいと思います！

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