{"id":2493,"date":"2025-03-09T09:36:25","date_gmt":"2025-03-09T01:36:25","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=2493"},"modified":"2025-03-09T13:02:17","modified_gmt":"2025-03-09T05:02:17","slug":"mongodb-map-reduce-%e8%af%a6%e8%a7%a3","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/03\/09\/mongodb-map-reduce-%e8%af%a6%e8%a7%a3\/","title":{"rendered":"MongoDB Map-Reduce \u8be6\u89e3"},"content":{"rendered":"\n

1. \u4ec0\u4e48\u662f Map-Reduce\uff1f<\/strong><\/h2>\n\n\n\n

Map-Reduce<\/code> \u662f MongoDB \u63d0\u4f9b\u7684\u4e00\u79cd\u6570\u636e\u805a\u5408\u673a\u5236\uff0c\u7528\u4e8e\u5904\u7406\u5927\u89c4\u6a21\u6570\u636e\u5206\u6790\u548c\u8ba1\u7b97<\/strong>\u3002\u5b83\u4e3b\u8981\u7528\u4e8e\u6267\u884c\u590d\u6742\u7684\u805a\u5408\u64cd\u4f5c\uff0c\u5c24\u5176\u9002\u7528\u4e8e\u5927\u6570\u636e\u96c6\u5408<\/strong>\u3002<\/p>\n\n\n\n

MongoDB \u7684 Map-Reduce<\/code> \u8fc7\u7a0b\u5305\u62ec\u4e24\u4e2a\u6838\u5fc3\u6b65\u9aa4\uff1a<\/p>\n\n\n\n

    \n
  1. Map\uff08\u6620\u5c04\uff09<\/strong>\uff1a\u5c06\u6587\u6863\u8f6c\u6362\u4e3a key-value<\/code> \u5f62\u5f0f\u3002<\/li>\n\n\n\n
  2. Reduce\uff08\u5f52\u7ea6\uff09<\/strong>\uff1a\u5bf9\u76f8\u540c key<\/code> \u7684\u503c\u8fdb\u884c\u5408\u5e76\u548c\u8ba1\u7b97\u3002<\/li>\n<\/ol>\n\n\n\n
    \n\n\n\n

    2. Map-Reduce \u7684\u57fa\u672c\u6d41\u7a0b<\/strong><\/h2>\n\n\n\n

    Map-Reduce \u5728 MongoDB \u4e2d\u7684\u6267\u884c\u6d41\u7a0b\u5982\u4e0b\uff1a<\/p>\n\n\n\n

      \n
    1. Map \u9636\u6bb5<\/strong>\uff1a\u904d\u5386\u96c6\u5408\u4e2d\u7684\u6bcf\u4e2a\u6587\u6863\uff0c\u63d0\u53d6\u6240\u9700\u5b57\u6bb5\uff0c\u8f93\u51fa key-value<\/code> \u7ed3\u6784\u3002<\/li>\n\n\n\n
    2. Reduce \u9636\u6bb5<\/strong>\uff1a\u5408\u5e76\u76f8\u540c key<\/code> \u7684\u503c\uff0c\u5e76\u8fdb\u884c\u8ba1\u7b97\uff08\u5982\u6c42\u548c\u3001\u8ba1\u6570\u3001\u5e73\u5747\u503c\uff09\u3002<\/li>\n\n\n\n
    3. \u8f93\u51fa\u7ed3\u679c<\/strong>\uff1a\u53ef\u4ee5\u5b58\u5165\u65b0\u96c6\u5408\u6216\u8fd4\u56de\u7ed9\u5ba2\u6237\u7aef\u3002<\/li>\n<\/ol>\n\n\n\n
      \n\n\n\n

      3. Map-Reduce \u8bed\u6cd5<\/strong><\/h2>\n\n\n\n

      MongoDB \u7684 Map-Reduce \u4e3b\u8981\u901a\u8fc7 mapReduce()<\/code> \u65b9\u6cd5\u6765\u6267\u884c\uff0c\u57fa\u672c\u8bed\u6cd5\u5982\u4e0b\uff1a<\/p>\n\n\n\n

      db.collection.mapReduce(\n   mapFunction,       \/\/ \u6620\u5c04\u51fd\u6570\n   reduceFunction,    \/\/ \u5f52\u7ea6\u51fd\u6570\n   {\n     out: \"result_collection\", \/\/ \u7ed3\u679c\u5b58\u50a8\u65b9\u5f0f\n     query: { },         \/\/ \u53ef\u9009\uff1a\u7b5b\u9009\u6570\u636e\n     sort: { },          \/\/ \u53ef\u9009\uff1a\u6392\u5e8f\n     limit: 100          \/\/ \u53ef\u9009\uff1a\u9650\u5236\u5904\u7406\u7684\u6587\u6863\u6570\n   }\n)<\/code><\/pre>\n\n\n\n
      \n\n\n\n
      4. \u793a\u4f8b\uff1a\u8ba1\u7b97\u6bcf\u4e2a\u7c7b\u522b\u7684\u603b\u9500\u552e\u989d<\/strong><\/h2>\n\n\n\n
      \u5047\u8bbe\u6211\u4eec\u6709\u4e00\u4e2a sales<\/code> \u96c6\u5408\uff0c\u5b58\u50a8\u4e86\u4ea7\u54c1\u9500\u552e\u6570\u636e\uff1a<\/p>\n\n\n\n
      { \"_id\": 1, \"category\": \"Electronics\", \"amount\": 500 }\n{ \"_id\": 2, \"category\": \"Clothing\", \"amount\": 200 }\n{ \"_id\": 3, \"category\": \"Electronics\", \"amount\": 300 }\n{ \"_id\": 4, \"category\": \"Clothing\", \"amount\": 100 }\n{ \"_id\": 5, \"category\": \"Furniture\", \"amount\": 400 }<\/code><\/pre>\n\n\n\n
      \u6211\u4eec\u5e0c\u671b\u8ba1\u7b97\u6bcf\u4e2a category<\/code> \u7684\u9500\u552e\u603b\u989d\u3002<\/p>\n\n\n\n
      (1) \u5b9a\u4e49 Map \u51fd\u6570<\/strong><\/h3>\n\n\n\n
      var mapFunction = function() {\n    emit(this.category, this.amount);\n};<\/code><\/pre>\n\n\n\n
        \n
      • emit(key, value)<\/code> \u5c06 category<\/code> \u4f5c\u4e3a key<\/code>\uff0camount<\/code> \u4f5c\u4e3a value<\/code> \u8f93\u51fa\u3002<\/li>\n<\/ul>\n\n\n\n
        (2) \u5b9a\u4e49 Reduce \u51fd\u6570<\/strong><\/h3>\n\n\n\n
        var reduceFunction = function(key, values) {\n    return Array.sum(values);\n};<\/code><\/pre>\n\n\n\n
          \n
        • values<\/code> \u662f\u6240\u6709\u76f8\u540c key<\/code> \u7684 amount<\/code> \u5217\u8868\uff0cArray.sum(values)<\/code> \u8ba1\u7b97\u603b\u989d\u3002<\/li>\n<\/ul>\n\n\n\n
          (3) \u6267\u884c Map-Reduce<\/strong><\/h3>\n\n\n\n
          db.sales.mapReduce(\n    mapFunction,\n    reduceFunction,\n    { out: \"sales_summary\" }\n);<\/code><\/pre>\n\n\n\n
            \n
          • \u8ba1\u7b97\u7ed3\u679c\u5b58\u5165 sales_summary<\/code> \u96c6\u5408\u3002<\/li>\n<\/ul>\n\n\n\n
            (4) \u67e5\u8be2\u7ed3\u679c<\/strong><\/h3>\n\n\n\n
            db.sales_summary.find();<\/code><\/pre>\n\n\n\n
            \u8f93\u51fa\uff1a<\/p>\n\n\n\n
            { \"_id\": \"Electronics\", \"value\": 800 }\n{ \"_id\": \"Clothing\", \"value\": 300 }\n{ \"_id\": \"Furniture\", \"value\": 400 }<\/code><\/pre>\n\n\n\n
            \n\n\n\n
            5. Map-Reduce \u7ed3\u679c\u5b58\u50a8\u65b9\u5f0f<\/strong><\/h2>\n\n\n\n
            \u5728 mapReduce()<\/code> \u65b9\u6cd5\u4e2d\uff0cout<\/code> \u9009\u9879\u51b3\u5b9a\u7ed3\u679c\u5b58\u50a8\u65b9\u5f0f\uff1a<\/p>\n\n\n\n
            \u9009\u9879<\/strong><\/th>\u63cf\u8ff0<\/strong><\/th><\/tr><\/thead>
            { out: \"collection_name\" }<\/code><\/td>\u7ed3\u679c\u5b58\u5165\u65b0\u96c6\u5408\uff0c\u53ef\u7528\u4e8e\u540e\u7eed\u67e5\u8be2\u3002<\/td><\/tr>
            { out: { inline: 1 } }<\/code><\/td>\u76f4\u63a5\u8fd4\u56de\u7ed3\u679c\uff0c\u4e0d\u5b58\u5165\u96c6\u5408\uff08\u9002\u7528\u4e8e\u5c0f\u6570\u636e\u91cf\uff09\u3002<\/td><\/tr>
            { out: { merge: \"collection_name\" } }<\/code><\/td>\u5c06\u7ed3\u679c\u5408\u5e76<\/strong>\u5230\u6307\u5b9a\u96c6\u5408\uff08\u76f8\u540c _id<\/code> \u7684\u503c\u8986\u76d6\uff09\u3002<\/td><\/tr>
            { out: { reduce: \"collection_name\" } }<\/code><\/td>\u5c06\u7ed3\u679c\u4e0e\u5df2\u6709\u96c6\u5408\u7684\u76f8\u540c _id<\/code> \u8fdb\u884c\u5f52\u7ea6<\/strong>\u3002<\/td><\/tr>
            { out: { replace: \"collection_name\" } }<\/code><\/td>\u66ff\u6362\u96c6\u5408\u4e2d\u7684\u6240\u6709\u6570\u636e\u3002<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
            \u793a\u4f8b\uff1a\u8fd4\u56de\u7ed3\u679c\u800c\u4e0d\u5b58\u5165\u96c6\u5408<\/p>\n\n\n\n
            db.sales.mapReduce(\n    mapFunction,\n    reduceFunction,\n    { out: { inline: 1 } }\n);<\/code><\/pre>\n\n\n\n
            \n\n\n\n
            6. \u8fc7\u6ee4\u6570\u636e<\/strong><\/h2>\n\n\n\n
            \u53ef\u4ee5\u4f7f\u7528 query<\/code> \u9009\u9879\u5728 mapReduce()<\/code> \u4e4b\u524d\u7b5b\u9009\u6570\u636e\uff1a<\/p>\n\n\n\n
            db.sales.mapReduce(\n    mapFunction,\n    reduceFunction,\n    {\n        out: \"sales_summary\",\n        query: { category: { $ne: \"Furniture\" } } \/\/ \u6392\u9664 Furniture \u7c7b\u522b\n    }\n);<\/code><\/pre>\n\n\n\n
            \n\n\n\n
            7. Map-Reduce vs Aggregation Pipeline<\/strong><\/h2>\n\n\n\n
            MongoDB 4.2+ \u63a8\u8350\u4f7f\u7528 \u805a\u5408\u7ba1\u9053\uff08Aggregation Pipeline\uff09<\/strong> \u800c\u975e mapReduce()<\/code>\uff0c\u56e0\u4e3a\uff1a
            \u2705 \u6027\u80fd\u66f4\u9ad8<\/strong>\uff08Map-Reduce \u8fd0\u884c\u5728 JavaScript \u89e3\u91ca\u5668\u4e0a\uff0c\u901f\u5ea6\u8f83\u6162\uff09\u3002
            \u2705 \u652f\u6301\u66f4\u591a\u64cd\u4f5c<\/strong>\uff08\u5982 $group<\/code>, $sum<\/code>, $avg<\/code>, $project<\/code>\uff09\u3002<\/p>\n\n\n\n
            \u4e0a\u9762 Map-Reduce<\/code> \u793a\u4f8b\u7528 \u805a\u5408\u7ba1\u9053<\/strong> \u4ee3\u66ff\uff1a<\/p>\n\n\n\n
            db.sales.aggregate([\n    { $group: { _id: \"$category\", totalAmount: { $sum: \"$amount\" } } }\n]);<\/code><\/pre>\n\n\n\n
            \u66f4\u7b80\u6d01\u9ad8\u6548\uff01<\/p>\n\n\n\n
            \n\n\n\n
            8. \u4f55\u65f6\u4f7f\u7528 Map-Reduce\uff1f<\/strong><\/h2>\n\n\n\n
            \u2705 \u9002\u7528\u4e8e\uff1a<\/strong><\/p>\n\n\n\n
              \n
            • \u9700\u8981\u590d\u6742\u8ba1\u7b97\uff08\u5982\u81ea\u5b9a\u4e49\u53bb\u91cd\u3001\u7edf\u8ba1\u5206\u6790\uff09\u3002<\/li>\n\n\n\n
            • \u5904\u7406\u8d85\u5927\u6570\u636e\u96c6\u5408\uff08\u4f46\u6027\u80fd\u53ef\u80fd\u8f83\u4f4e\uff09\u3002<\/li>\n\n\n\n
            • \u9700\u8981 JavaScript \u903b\u8f91\u5904\u7406\u3002<\/li>\n<\/ul>\n\n\n\n
              \u274c \u4e0d\u9002\u7528\u4e8e\uff1a<\/strong><\/p>\n\n\n\n
                \n
              • \u4ec5\u7528\u4e8e\u805a\u5408\uff08\u63a8\u8350 aggregate()<\/code>\uff09\u3002<\/li>\n\n\n\n
              • \u9700\u8981\u9ad8\u6027\u80fd\u8ba1\u7b97\uff08\u63a8\u8350\u5206\u5e03\u5f0f\u8ba1\u7b97\u6846\u67b6\uff0c\u5982 Spark\uff09\u3002<\/li>\n<\/ul>\n\n\n\n
                \n\n\n\n
                9. \u603b\u7ed3<\/strong><\/h2>\n\n\n\n
                  \n
                • Map-Reduce<\/code> \u9002\u7528\u4e8e\u590d\u6742\u6570\u636e\u5904\u7406\uff0c\u4f46\u6027\u80fd\u8f83\u4f4e\u3002<\/li>\n\n\n\n
                • \u8bed\u6cd5\u5305\u62ec Map\uff08\u6620\u5c04\uff09<\/strong> \u548c Reduce\uff08\u5f52\u7ea6\uff09<\/strong> \u4e24\u90e8\u5206\u3002<\/li>\n\n\n\n
                • \u7ed3\u679c\u53ef\u4ee5\u5b58\u5165\u65b0\u96c6\u5408\u6216\u8fd4\u56de\u7ed9\u5ba2\u6237\u7aef\u3002<\/li>\n\n\n\n
                • \u63a8\u8350\u4f7f\u7528 Aggregation Pipeline<\/code> \u4ee3\u66ff<\/strong>\uff0c\u9664\u975e\u5fc5\u987b\u4f7f\u7528 JavaScript \u903b\u8f91\u3002<\/li>\n<\/ul>\n\n\n\n
                  \u66f4\u591a\u8be6\u7ec6\u5185\u5bb9\u53ef\u4ee5\u5173\u6ce8\u5176\u4ed6\u76f8\u5173\u6587\u7ae0\uff01\ud83d\ude0a<\/p>\n","protected":false},"excerpt":{"rendered":"
                  1. \u4ec0\u4e48\u662f Map-Reduce\uff1f Map-Reduce \u662f MongoDB \u63d0\u4f9b\u7684\u4e00\u79cd\u6570\u636e\u805a\u5408\u673a\u5236\uff0c\u7528\u4e8e\u5904 […]<\/p>\n","protected":false},"author":1,"featured_media":2539,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[77],"tags":[],"class_list":["post-2493","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-mongodb"],"_links":{"self":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2493","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/comments?post=2493"}],"version-history":[{"count":3,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2493\/revisions"}],"predecessor-version":[{"id":2530,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2493\/revisions\/2530"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media\/2539"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=2493"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=2493"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=2493"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}