{"id":151946,"date":"2020-09-01T10:36:22","date_gmt":"2020-09-01T02:36:22","guid":{"rendered":"http:\/\/4563.org\/?p=151946"},"modified":"2020-09-01T10:36:22","modified_gmt":"2020-09-01T02:36:22","slug":"%e8%a6%86%e7%9b%96%e7%b4%a2%e5%bc%95%ef%bc%8c%e4%bd%86%e6%98%af%e6%b2%a1%e6%9c%89%e6%9c%80%e5%b7%a6%e5%89%8d%e7%bc%80%e5%8c%b9%e9%85%8d%ef%bc%8c%e6%80%a7%e8%83%bd%e5%a6%82%e4%bd%95","status":"publish","type":"post","link":"http:\/\/4563.org\/?p=151946","title":{"rendered":"\u8986\u76d6\u7d22\u5f15\uff0c\u4f46\u662f\u6ca1\u6709\u6700\u5de6\u524d\u7f00\u5339\u914d\uff0c\u6027\u80fd\u5982\u4f55"},"content":{"rendered":"
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\u8986\u76d6\u7d22\u5f15\uff0c\u4f46\u662f\u6ca1\u6709\u6700\u5de6\u524d\u7f00\u5339\u914d\uff0c\u6027\u80fd\u5982\u4f55 <\/h1>\n

<\/p>\n

\n
\u8cc7\u6df1\u5927\u4f6c : hackingwu <\/span> <\/i> 1<\/span> <\/div>\n
<\/div>\n<\/p><\/div>\n<\/p><\/div>\n<\/p><\/div>\n
<\/p>\n

\u6709\u4e00\u4e2a\u7ec4\u5408\u7d22\u5f15 idx on t1(c1, c2); \u67e5\u8be2\u8bed\u53e5 select id, c1 from t1 where c2 = xxx; \u8fd9\u91cc\u4f1a\u7528\u5230\u8986\u76d6\u7d22\u5f15\uff0c\u4f46\u662f\u5374\u662f\u7528 c2 \u505a\u6761\u4ef6\u67e5\u8be2\uff0c\u8fd9\u6837\u4f1a\u5168\u7d22\u5f15\u626b\u63cf\u5417\uff0c\u6570\u636e\u91cf\u5927\u4e86\uff0c\u6027\u80fd\u5982\u4f55\uff1f<\/p>\n<\/p><\/div>\n

<\/p>\n

\u5927\u4f6c\u6709\u8a71\u8aaa<\/b> (22<\/span>) <\/div>\n
<\/div>\n<\/p><\/div>\n<\/p><\/div>\n
    \n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : zhouhu <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u8fd9\u4e2a\u67e5\u8be2\u4e0d\u4f1a\u7528\u5230\u4f60\u6240\u8bf4\u7684\u7d22\u5f15 <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : optional <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u8fd9\u4e2a\u4f1a\u7528\u8986\u76d6\u7d22\u5f15\uff1f <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u4e3b<\/span> \u8cc7\u6df1\u5927\u4f6c : hackingwu <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    @zhouhu \u80af\u5b9a\u4f1a\u5440 \uff0c\u4f60 explain \u4e00\u4e0b\u5c31\u77e5\u9053\u4e86\uff0c\u8d70\u8986\u76d6\u7d22\u5f15\u5440 <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : useben <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u4e0d\u8d70\u7d22\u5f15, \u5c31\u662f\u5168\u8868\u626b\u63cf\u7684\u6027\u80fd <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : qianProgrammer <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    type \u662f index \u5427,\u626b\u63cf\u4e86\u6574\u4e2a\u7d22\u5f15\u6811,\u53ea\u662f\u6b63\u597d\u5339\u914d\u5230\u4e86\u4f60\u7684\u6761\u4ef6,\u4e0d\u5982\u6700\u5de6\u5339\u914d\u7684\u6548\u7387\u9ad8,\u4f46\u4e5f\u6bd4 all \u5168\u8868\u626b\u63cf\u5feb <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : Jooooooooo <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u8fd9\u548c\u6ca1\u7d22\u5f15\u4e00\u6837 <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : wangritian <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u8986\u76d6\u7d22\u5f15\u5e94\u8be5\u662f\u6307\u7d22\u5f15\u6811\u4e0a\u5305\u542b\u4e86\u672c\u6b21\u67e5\u8be2\u7684\u5168\u90e8\u5b57\u6bb5\uff0c\u65e0\u9700\u56de\u8868\uff0c\u4f60\u7684 sql \u662f\u7b26\u5408\u7684
    \u4f46\u67e5\u8be2\u6761\u4ef6 c2 \u4e0d\u5728 t1 \u7684\u5f00\u5934\uff0c\u6240\u4ee5\u8d70\u5168\u8868\u626b\u63cf <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : yukong <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u8fd9\u4e0d\u662f\u5168\u8868\u626b\u63cf\u4e86\u5417 <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : CODEWEA <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u600e\u4e48\u53ef\u80fd\u5462 <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : wps353 <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u5728 8.0.13 \u4ee5\u524d\u7684\u8bdd\u7528\u4e0d\u5230\u8986\u76d6\u7d22\u5f15\uff0c\u5728 8.0.13 \u540e\uff0c\u5982\u679c\u8bf4 a \u7684 Cardinality \u6bd4\u8f83\u4f4e\u7684\u8bdd\uff0c\u6709\u53ef\u80fd\u901a\u8fc7 skip index scan \u4f7f\u7528\u5230\u3002 <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : zhangysh1995 <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u6839\u636e\u6587\u6863\u5e94\u8be5\u662f\u5168\u8868\u626b\u63cf \u6216\u8005\u5c1d\u8bd5\u9009\u8fc7\u6ee4\u9ad8\u7684<\/p>\n

    If separate single-column indexes exist on col1 and col2, the optimizer attempts to use the Index Merge optimization (see Section 8.2.1.3, \u201cIndex Merge Optimization\u201d), or attempts to find the most restrictive index by deciding which index excludes more rows and using that index to fetch the rows.<\/p>\n

    https:\/\/dev.mysql.com\/doc\/refman\/8.0\/en\/multiple-column-indexes.html <\/p><\/div>\n<\/p><\/div>\n<\/li>\n

  • \n
    \n
    \n
    \u4e3b<\/span> \u8cc7\u6df1\u5927\u4f6c : hackingwu <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    @wangritian \u6211\u7684 c1,c2 \u4fe1\u606f\u90fd\u5728\u7d22\u5f15\u91cc\uff0c\u4e0d\u4f1a\u518d\u56de\u8868\u5566\u3002 <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u4e3b<\/span> \u8cc7\u6df1\u5927\u4f6c : hackingwu <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    @zhangysh1995 \u6211\u8fd9\u4e0d\u662f single-column index, \u6211\u8fd9\u662f\u7ec4\u5408\u7d22\u5f15\u5440 \uff0c\u4e0d\u662f\u4f60\u6587\u6863\u63cf\u8ff0\u7684\u573a\u666f <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : SjwNo1 <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u76f4\u63a5\u6ca1\u8d70\u4f60\u7684\u8054\u5408\u7d22\u5f15\u5427 \u81ea\u5efa\u7d22\u5f15\u6811\u90fd\u6ca1\u8d70\u600e\u4e48\u5229\u7528\u8986\u76d6\u7d22\u5f15\uff08\u6709\u70b9\u5fd8\u4e86 <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : wangritian <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    @hackingwu \u7a81\u7136\u53d1\u73b0\u81ea\u5df1\u4e0a\u9762\u7684\u63cf\u8ff0\u4e0d\u5bf9\uff0c\u5e94\u8be5\u662f\u8d70\u4e86\u5168\u7d22\u5f15\u6811\u626b\u63cf\u3002\u6211\u731c\u4f18\u5316\u5668\u53d1\u73b0\u4f60\u7684 t1 \u7d22\u5f15\u5305\u542b\u4e86\u5168\u90e8\u9700\u6c42\u5b57\u6bb5\uff0c\u6240\u4ee5\u5728 t1 \u7d22\u5f15\u6811\u4e0a\u505a\u5168\u90e8\u626b\u63cf\uff0c\u800c\u6ca1\u6709\u53bb\u4e3b\u952e\u7d22\u5f15\u6811\uff08\u539f\u8868\uff09\u505a\u626b\u63cf\uff0c\u56e0\u4e3a t1 \u6811\u7684\u5b57\u8282\u5927\u5c0f\u4e00\u5b9a\u5c0f\u4e8e\u539f\u8868\uff0c\u66f4\u8282\u7701\u78c1\u76d8 I\/O \u3002\u6240\u4ee5\u4f60\u7684 explain \u7ed3\u679c\u7528\u5230\u4e86\u8986\u76d6\u7d22\u5f15\u3002\u8bf4\u7684\u4e0d\u5bf9\u8bf7\u6307\u6b63\u3002 <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : changdy <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u5fc3\u75bc\u9898\u4e3b….\u90a3\u4e48\u591a\u4eba\u90fd\u8bf4\u76f4\u63a5\u8d70\u5168\u8868,\u4e0d\u77e5\u9053\u6709\u6ca1\u6709\u6000\u7591\u4eba\u751f…<\/p>\n

    \u72d7\u5c3e\u7eed\u8c82 , \u4e5f\u8bf7\u6559\u5404\u4f4d\u4e00\u4e2a\u95ee\u9898 , mysql \u7684\u5206\u533a\u8868\u5982\u4f55 ? \u76ee\u524d\u7cfb\u7edf\u4e1a\u52a1\u91cf\u6bd4\u8f83\u5927, \u60f3\u7528 mysql \u672c\u8eab\u7684\u5206\u533a\u8868\u5b9e\u73b0\u7c7b\u4f3c\u5206\u8868\u529f\u80fd. <\/p><\/div>\n<\/p><\/div>\n<\/li>\n

  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : RedisMasterNode <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u5fc3\u75bc\u4e3b…\u8fd8\u6709\u8fd9\u4e48\u591a\u4eba\u8bf4\u8d70\u5168\u8868\uff0c\u4e00\u5b9a\u8981\u575a\u6301\u6709\u81ea\u5df1\u7684\u89c2\u70b9\u5440^_^\u7279\u522b\u662f\u4f60\u89c9\u5f97\u6709\u8db3\u591f\u7684\u4e1c\u897f\u652f\u6491\u89c2\u70b9\u7684\u65f6\u5019<\/p>\n

    \u8fd9\u4e2a\u67e5\u8be2\u6beb\u65e0\u7591\u95ee\uff08\u6b63\u5e38\u60c5\u51b5\u4e0b\uff09\u4f1a\u8d70\u4f60\u7684(c1, c2)\u7d22\u5f15\uff0c\u524d\u63d0\u662f\u4f60\u7684\u8868\u53ef\u80fd\u5f97\u4e0d\u6b62\u6709 id, c1, c2 \u8fd9 3 \u4e2a\u5b57\u6bb5\uff0c\u7406\u7531\u662f\u4e3b\u952e\u7d22\u5f15\u7684\u6bcf\u4e2a\u9875\u80fd\u591f\u5b58\u653e\u4e0b\u7684\u6570\u636e\u884c\u6bd4(c1, c2)\u7d22\u5f15\u6bcf\u4e2a\u9875\u80fd\u5b58\u653e\u4e0b\u7684\u6570\u636e\u884c\u66f4\u5c11\uff0c\u5982\u679c\u626b\u63cf\u4e3b\u952e\u83b7\u53d6\u7ed3\u679c\uff0c\u9700\u8981\u626b\u8fc7\u66f4\u591a\u7684\u6570\u636e\u9875\uff0c\u5982\u679c\u626b(c1, c2)\u7d22\u5f15\uff0c\u5c3d\u7ba1\u6ca1\u6709\u7528\u4e0a”\u7d22\u5f15”\u7684\u67e5\u8be2\u7279\u6027\uff0c\u4f46\u662f\u53ef\u4ee5\u901a\u8fc7\u626b\u66f4\u5c11\u7684\u9875\u5f97\u5230\u6b63\u786e\u7ed3\u679c\u3002<\/p>\n

    \u6027\u80fd\u7684\u5dee\u8ddd = \u4e3b\u952e\u7d22\u5f15\u4f53\u79ef vs (c1, c2)\u7d22\u5f15\u4f53\u79ef\uff0c\u5f53\u4f60\u7684\u8868\u5b57\u6bb5\u8d8a\u591a\uff0c\u8d8a\u5927\u7684\u65f6\u5019\uff0c\u5dee\u8ddd\u8d8a\u660e\u663e\uff1b\u53cd\u4f8b\u5219\u662f\u5982\u679c\u8868\u53ea\u6709 id, c1, c2 \u4e09\u4e2a\u5b57\u6bb5\u7684\u65f6\u5019\uff0c\u626b\u63cf\u7684\u65f6\u95f4\u7406\u8bba\u4e0a\u5e94\u8be5\u662f\u975e\u5e38\u63a5\u8fd1\u7684\uff0c\u5e76\u4e14\u4f18\u5316\u5668\u5728\u9009\u62e9\u4e0a\u4e24\u4e2a\u7d22\u5f15\u90fd\u6709\u53ef\u80fd\u9009\u62e9\u4f7f\u7528 <\/p><\/div>\n<\/p><\/div>\n<\/li>\n

  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : RedisMasterNode <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    em \u8865\u5145\u4e00\u70b9\uff0c\u5728\u5b57\u6bb5\u5c11\uff08\u4f46\u4e0d\u4ec5\u6709 id, c1, c2 \uff09\u7684\u60c5\u51b5\u4e0b\uff0c\u5982\u679c c1, c2 \u662f varchar \u4e4b\u7c7b\u7684\u7c7b\u578b\uff0c\u672a\u5fc5\u4f1a\u771f\u7684\u9009\u62e9(c1, c2)\u7d22\u5f15\u8fdb\u884c\u7d22\u5f15\u626b\u63cf\uff0c\u56e0\u4e3a\u9009\u62e9\u4f7f\u7528\u4ec0\u4e48\u67e5\u8be2\u8def\u5f84\u662f\u6839\u636e cardinality \u503c\u6765\u51b3\u5b9a\u7684\uff0c\u8fd9\u4e2a\u503c\u662f\u901a\u8fc7\u5b9a\u671f\u5bf9\u9875\u8fdb\u884c\u91c7\u6837\u3001\u7edf\u8ba1\u7684\u7ed3\u679c\uff0c\u662f\u4e2a\u9884\u4f30\u503c\uff0c\u5982\u679c\u4e0d\u5de7 mysql \u8bb0\u5f55\u7684\u4e3b\u952e\u7d22\u5f15\u548c(c1, c2)\u7d22\u5f15\u7684\u9884\u4f30\u503c\u4e0e\u5b9e\u9645\u4e0d\u7b26\uff0c\u90a3\u6709\u53ef\u80fd\u4f1a\u91c7\u53d6\uff08\u5b9e\u9645\u6027\u80fd\u66f4\u5dee\uff09\u7684\u4e3b\u952e\u626b\u63cf\u6765\u6267\u884c <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : maigebaoer <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    sql \u5df2\u7ecf\u662f\u9ed1\u7bb1\u5b50\u4e86 <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : pkoukk <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    \u4e0d\u4f1a\u8d70\u5168\u8868\u626b\u63cf\uff08\u4e3b\u952e\u626b\u63cf\uff09\uff0c\u4f46\u662f\u4f1a\u8d70\u4f60\u8fd9\u4e2a\u7d22\u5f15\u7684\u5168\u7d22\u5f15\u626b\u63cf\u3002
    \u600e\u4e48\u8bf4\u5462\uff0c\u80af\u5b9a\u6bd4\u5168\u8868\u5f3a\uff0c\u4f46\u662f\u5230\u5e95\u5f3a\u591a\u5c11\u5f97\u770b\u4f60\u8fd9\u4e2a\u7d22\u5f15\u7684\u533a\u5206\u5ea6 <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : zhangysh1995 <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    @hackingwu \u4f60\u5e94\u8be5\u770b\u4e0b\u4e0a\u7ebf\u6587\uff0c\u8fd9\u91cc\u662f\u8bf4\u7ec4\u5408\u7d22\u5f15\u7528\u4e0d\u4e86\uff0c\u5982\u679c\u6709 single column \u7d22\u5f15\u4f1a\u7528\u7684\u3002\u548c\u4f60\u7684\u60c5\u51b5\u6ca1\u6709\u51b2\u7a81\u3002 <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n
    \n
    \n
    \u8cc7\u6df1\u5927\u4f6c : zhouhu <\/span> <\/div>\n
    <\/i> <\/span> <\/div>\n<\/p><\/div>\n
    @hackingwu \u4e0d\u597d\u610f\u601d\uff0c\u6211\u8bf4\u9519\u4e86\u3002\u8bd5\u4e86\u4e00\u4e0b\uff0c\u786e\u5b9e\u662f\u53ef\u4ee5\u7684\u3002\u4e0d\u8fc7\u5b9e\u9645\u4e0a\u4e5f\u662f\u4e0d\u63a8\u8350\u8fd9\u79cd\u7528\u6cd5\u5427\u3002\u5982\u679c\u7d22\u5f15\u80fd\u5168\u90e8\u52a0\u8f7d\u8fdb\u5185\u5b58\uff0c\u901f\u5ea6\u5e94\u8be5\u8fd8\u884c\u3002 <\/div>\n<\/p><\/div>\n<\/li>\n
  • \n","protected":false},"excerpt":{"rendered":"

    \u8986\u76d6\u7d22\u5f15\uff0c\u4f46\u662f\u6ca1\u6709\u6700\u5de6\u524d\u7f00\u5339\u914d\uff0c\u6027…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[],"tags":[],"_links":{"self":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts\/151946"}],"collection":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=151946"}],"version-history":[{"count":0,"href":"http:\/\/4563.org\/index.php?rest_route=\/wp\/v2\/posts\/151946\/revisions"}],"wp:attachment":[{"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=151946"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=151946"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/4563.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=151946"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}