{"id":2481,"date":"2025-03-09T09:24:14","date_gmt":"2025-03-09T01:24:14","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=2481"},"modified":"2025-03-09T13:06:30","modified_gmt":"2025-03-09T05:06:30","slug":"mongodb-%e8%a6%86%e7%9b%96%e7%b4%a2%e5%bc%95%e6%9f%a5%e8%af%a2%ef%bc%88covered-query%ef%bc%89","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/03\/09\/mongodb-%e8%a6%86%e7%9b%96%e7%b4%a2%e5%bc%95%e6%9f%a5%e8%af%a2%ef%bc%88covered-query%ef%bc%89\/","title":{"rendered":"MongoDB \u8986\u76d6\u7d22\u5f15\u67e5\u8be2\uff08Covered Query\uff09"},"content":{"rendered":"\n

\u5728 MongoDB \u4e2d\uff0c\u8986\u76d6\u7d22\u5f15\u67e5\u8be2\uff08Covered Query\uff09<\/strong>\u662f\u6307\u67e5\u8be2\u6240\u9700\u7684\u6240\u6709\u5b57\u6bb5\u90fd\u53ef\u4ee5\u76f4\u63a5\u4ece\u7d22\u5f15\u4e2d\u83b7\u53d6<\/strong>\uff0cMongoDB \u65e0\u9700\u626b\u63cf\u6587\u6863\uff08Documents\uff09\uff0c\u4ece\u800c\u63d0\u9ad8\u67e5\u8be2\u6027\u80fd\u3002<\/p>\n\n\n\n

\n\n\n\n

1. \u8986\u76d6\u7d22\u5f15\u67e5\u8be2\u7684\u7279\u70b9<\/strong><\/h2>\n\n\n\n
    \n
  • \u67e5\u8be2\u5b57\u6bb5\u5168\u90e8\u5728\u7d22\u5f15\u4e2d<\/strong> \u2192 \u907f\u514d\u8bbf\u95ee\u5b9e\u9645\u6587\u6863\uff0c\u51cf\u5c11 I\/O\u3002<\/li>\n\n\n\n
  • \u7d22\u5f15\u5fc5\u987b\u5305\u542b\u6240\u6709\u67e5\u8be2\u5b57\u6bb5<\/strong>\uff08\u5305\u62ec find<\/code> \u6761\u4ef6\u5b57\u6bb5\u3001projection<\/code> \u8fd4\u56de\u5b57\u6bb5\uff09\u3002<\/li>\n\n\n\n
  • _id \u5b57\u6bb5\u9ed8\u8ba4\u5b58\u5728\u7d22\u5f15<\/strong>\uff0c\u5982\u679c\u67e5\u8be2\u7ed3\u679c\u4e0d\u5305\u542b _id<\/code>\uff0c\u53ef\u80fd\u9700\u8981\u663e\u5f0f\u6392\u9664\u5b83\u3002<\/li>\n<\/ul>\n\n\n\n
    \n\n\n\n

    2. \u521b\u5efa\u8986\u76d6\u7d22\u5f15<\/strong><\/h2>\n\n\n\n

    \u793a\u4f8b\uff1a\u521b\u5efa\u96c6\u5408<\/strong><\/h3>\n\n\n\n
    db.products.insertMany([\n  { _id: 1, name: \"Laptop\", category: \"Electronics\", price: 1200 },\n  { _id: 2, name: \"Phone\", category: \"Electronics\", price: 800 },\n  { _id: 3, name: \"Table\", category: \"Furniture\", price: 150 }\n])<\/code><\/pre>\n\n\n\n
    \u2460 \u521b\u5efa\u7d22\u5f15<\/strong><\/h3>\n\n\n\n
    \u521b\u5efa\u7ec4\u5408\u7d22\u5f15<\/strong>\uff0c\u5305\u542b category<\/code> \u548c price<\/code> \u5b57\u6bb5\uff1a<\/p>\n\n\n\n
    db.products.createIndex({ category: 1, price: 1 })<\/code><\/pre>\n\n\n\n
    \u2461 \u4f7f\u7528\u8986\u76d6\u7d22\u5f15\u67e5\u8be2<\/strong><\/h3>\n\n\n\n
    \u67e5\u8be2 category<\/code> \u548c price<\/code>\uff0c\u5e76\u6392\u9664 _id<\/code>\uff08\u907f\u514d\u626b\u63cf\u6587\u6863\uff09\uff1a<\/p>\n\n\n\n
    db.products.find({ category: \"Electronics\" }, { category: 1, price: 1, _id: 0 })<\/code><\/pre>\n\n\n\n
    \ud83d\udca1 \u4e3a\u4ec0\u4e48\u6392\u9664 _id<\/code>\uff1f<\/strong><\/p>\n\n\n\n
      \n
    • _id<\/code> \u9ed8\u8ba4\u6709\u7d22\u5f15\uff0c\u4f46\u4e0d\u5728 { category: 1, price: 1 }<\/code> \u7ec4\u5408\u7d22\u5f15\u5185\uff0cMongoDB \u9700\u8981\u8bbf\u95ee\u6587\u6863\u6765\u83b7\u53d6 _id<\/code>\uff0c\u5bfc\u81f4\u67e5\u8be2\u65e0\u6cd5\u5b8c\u5168\u8986\u76d6\u7d22\u5f15\u3002<\/li>\n<\/ul>\n\n\n\n
      \n\n\n\n
      3. \u4f7f\u7528 explain()<\/code> \u9a8c\u8bc1<\/strong><\/h2>\n\n\n\n
      \u53ef\u4ee5\u4f7f\u7528 .explain(\"executionStats\")<\/code> \u68c0\u67e5\u67e5\u8be2\u662f\u5426\u662f\u8986\u76d6\u7d22\u5f15\u67e5\u8be2<\/strong>\uff1a<\/p>\n\n\n\n
      db.products.find({ category: \"Electronics\" }, { category: 1, price: 1, _id: 0 }).explain(\"executionStats\")<\/code><\/pre>\n\n\n\n
      \u67e5\u770b explain<\/code> \u7ed3\u679c\u4e2d\u7684 \"stage\"<\/code>\uff1a<\/p>\n\n\n\n
      \"stage\": \"PROJECTION_COVERED\"<\/code><\/pre>\n\n\n\n
      \u5982\u679c \"stage\": \"PROJECTION_COVERED\"<\/code>\uff0c\u5219\u8868\u793a\u5b8c\u5168\u4f7f\u7528\u7d22\u5f15\uff0c\u67e5\u8be2\u65e0\u9700\u8bbf\u95ee\u6587\u6863<\/strong>\u3002<\/p>\n\n\n\n
      \n\n\n\n
      4. \u8986\u76d6\u7d22\u5f15 vs. \u975e\u8986\u76d6\u7d22\u5f15\u67e5\u8be2<\/strong><\/h2>\n\n\n\n
      \u67e5\u8be2\u65b9\u5f0f<\/th>\u662f\u5426\u4f7f\u7528\u7d22\u5f15<\/th>\u662f\u5426\u8bbf\u95ee\u6587\u6863<\/th>\u9002\u7528\u573a\u666f<\/th><\/tr><\/thead>
      \u666e\u901a\u7d22\u5f15\u67e5\u8be2<\/strong><\/td>\u4ec5\u7528\u4e8e\u67e5\u627e<\/td>\u9700\u8981\u8bbf\u95ee\u6587\u6863<\/td>\u67e5\u8be2\u5b57\u6bb5\u8f83\u591a<\/td><\/tr>
      \u8986\u76d6\u7d22\u5f15\u67e5\u8be2<\/strong><\/td>\u76f4\u63a5\u83b7\u53d6\u7ed3\u679c<\/td>\u65e0\u9700\u8bbf\u95ee\u6587\u6863<\/td>\u67e5\u8be2\u5b57\u6bb5\u8f83\u5c11\uff0c\u63d0\u9ad8\u6027\u80fd<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
      \n\n\n\n
      5. \u8986\u76d6\u7d22\u5f15\u7684\u4f18\u5316\u6280\u5de7<\/strong><\/h2>\n\n\n\n
      \u2705 \u4f7f\u7528\u7ec4\u5408\u7d22\u5f15\uff08Compound Index\uff09<\/strong>\uff0c\u786e\u4fdd\u67e5\u8be2\u5b57\u6bb5\u5168\u90e8\u5305\u542b\u5728\u7d22\u5f15\u4e2d\u3002
      \u2705 \u6392\u9664 _id<\/code> \u5b57\u6bb5<\/strong>\uff08\u5982\u679c\u4e0d\u5728\u7d22\u5f15\u5185\uff09\uff0c\u907f\u514d\u989d\u5916\u7684\u6587\u6863\u626b\u63cf\u3002
      \u2705 \u9002\u7528\u4e8e\u53ea\u67e5\u8be2\u5c11\u91cf\u5b57\u6bb5<\/strong>\u7684\u573a\u666f\uff0c\u4f8b\u5982\u7edf\u8ba1\u3001\u5217\u8868\u5c55\u793a\u7b49\u3002<\/p>\n\n\n\n
      \n\n\n\n
      6. \u603b\u7ed3<\/strong><\/h2>\n\n\n\n
        \n
      • \u8986\u76d6\u7d22\u5f15\u67e5\u8be2\u53ef\u4ee5\u663e\u8457\u63d0\u9ad8\u67e5\u8be2\u6027\u80fd<\/strong>\uff0c\u907f\u514d\u6587\u6863\u626b\u63cf\uff0c\u51cf\u5c11 I\/O\u3002<\/li>\n\n\n\n
      • \u5fc5\u987b\u786e\u4fdd\u67e5\u8be2\u7684\u5b57\u6bb5\u90fd\u5728\u7d22\u5f15\u4e2d<\/strong>\uff0c\u5426\u5219 MongoDB \u4ecd\u7136\u4f1a\u8bbf\u95ee\u6587\u6863\u3002<\/li>\n\n\n\n
      • \u4f7f\u7528 .explain(\"executionStats\")<\/code> \u68c0\u67e5\u662f\u5426\u662f\u8986\u76d6\u7d22\u5f15\u67e5\u8be2<\/strong>\uff0c\u5173\u952e\u662f \"stage\": \"PROJECTION_COVERED\"<\/code>\u3002<\/li>\n<\/ul>\n\n\n\n
        \u66f4\u591a\u8be6\u7ec6\u5185\u5bb9\u8bf7\u5173\u6ce8\u5176\u4ed6\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"
        \u5728 MongoDB \u4e2d\uff0c\u8986\u76d6\u7d22\u5f15\u67e5\u8be2\uff08Covered Query\uff09\u662f\u6307\u67e5\u8be2\u6240\u9700\u7684\u6240\u6709\u5b57\u6bb5\u90fd\u53ef\u4ee5\u76f4\u63a5\u4ece\u7d22\u5f15\u4e2d\u83b7\u53d6 […]<\/p>\n","protected":false},"author":1,"featured_media":2546,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[77],"tags":[],"class_list":["post-2481","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\/2481","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=2481"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2481\/revisions"}],"predecessor-version":[{"id":2482,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/2481\/revisions\/2482"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media\/2546"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=2481"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=2481"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=2481"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}