{"id":1774,"date":"2019-01-21T07:30:12","date_gmt":"2019-01-20T23:30:12","guid":{"rendered":"https:\/\/coderbee.net\/?p=1774"},"modified":"2019-01-20T17:55:32","modified_gmt":"2019-01-20T09:55:32","slug":"%e3%80%8amysql-%e5%ae%9e%e6%88%9845%e8%ae%b2%e3%80%8b-%e7%ac%94%e8%ae%b0-order-by-%e5%ae%9e%e7%8e%b0","status":"publish","type":"post","link":"https:\/\/coderbee.net\/index.php\/db\/20190121\/1774","title":{"rendered":"\u300aMySQL \u5b9e\u621845\u8bb2\u300b–\u7b14\u8bb0–order by \u5b9e\u73b0"},"content":{"rendered":"

\u7528 explain \u547d\u4ee4\u67e5\u770b\u6267\u884c\u8ba1\u5212\u7684\u65f6\u5019\uff0cExtra \u5217\u7684\u503c\u542b\u6709 “using filesort” \u8868\u793a\u9700\u8981\u6392\u5e8f\uff0c\u53ef\u80fd\u662f\u5728\u5185\u5b58\u91cc\u6392\u5e8f\u3001\u4e5f\u53ef\u80fd\u662f\u78c1\u76d8\u6587\u4ef6\u6392\u5e8f\u3002MySQL \u7ed9\u6bcf\u4e2a\u7ebf\u7a0b\u5206\u914d\u4e00\u5757\u5185\u5b58\u7528\u4e8e\u6392\u5e8f\uff0c\u79f0\u4e3a sort_buffer \uff0c\u53ef\u4ee5\u901a\u8fc7\u53c2\u6570 sort_buffer_size<\/code> \u8c03\u6574\u8fd9\u4e2a\u5185\u5b58\u7684\u5927\u5c0f\u3002<\/p>\n

\u5982\u679c\u8981\u6392\u5e8f\u7684\u6570\u636e\u90fd\u80fd\u653e\u8fdb sort_buffer \u5219\u76f4\u63a5\u5728\u5185\u5b58\u91cc\u6392\u5e8f\uff0c\u5426\u5219\u9700\u8981\u501f\u52a9\u78c1\u76d8\u4e34\u65f6\u6587\u4ef6\u8fdb\u884c\u8f85\u52a9\u6392\u5e8f\u3002<\/p>\n

\u7531\u4e8e InnoDB \u662f\u7d22\u5f15\u7ec4\u7ec7\u8868\uff0c\u805a\u7c07\u7d22\u5f15\u5c31\u662f\u4e3b\u952e\u7d22\u5f15\uff0c\u4e0b\u9762\u7684\u63cf\u8ff0\u5c31\u7528 rowid \u66ff\u4ee3\u4e3b\u952e\u503c\u3002<\/p>\n

\u8d70\u7d22\u5f15\u5168\u5b57\u6bb5\u6392\u5e8f<\/h2>\n
    \n
  1. \u521d\u59cb\u5316 sort_buffer\uff0c\u786e\u5b9a\u8981\u653e\u5165 sort_buffer \u7684\u76ee\u6807\u5b57\u6bb5\uff1b<\/li>\n
  2. \u6839\u636e\u9009\u62e9\u7684\u7d22\u5f15\u67e5\u627e\u6ee1\u8db3\u6761\u4ef6\u7684 rowid\uff1b<\/li>\n
  3. \u901a\u8fc7rowid\u5230\u805a\u7c07\u7d22\u5f15\u6811\u83b7\u53d6\u6574\u884c\u6570\u636e\uff0c\u53d6\u76ee\u6807\u5b57\u6bb5\u653e\u5165sort_buffer\uff1b<\/li>\n
  4. \u4ece\u9009\u62e9\u7684\u7d22\u5f15\u53d6\u4e0b\u4e00\u4e2a\u8bb0\u5f55\u7684rowid\uff1b<\/li>\n
  5. \u91cd\u590d\u6b65\u9aa4 3\u30014\u76f4\u5230\u4e0d\u6ee1\u8db3\u6761\u4ef6\uff1b<\/li>\n
  6. \u5bf9 sort_buffer \u4e2d\u7684\u6570\u636e\u6309\u7167\u6392\u5e8f\u5217\u8fdb\u884c\u6392\u5e8f\u3002<\/li>\n
  7. \u904d\u5386\u6392\u5e8f\u7ed3\u679c\uff0c\u628a\u76ee\u6807\u6570\u636e\u8fd4\u56de\u7ed9\u5ba2\u6237\u7aef\u3002<\/li>\n<\/ol>\n

    <\/p>\n

    \u8d70\u7d22\u5f15 rowid \u6392\u5e8f<\/h2>\n

    \u5982\u679c MySQL \u8ba4\u4e3a\u8981\u6392\u5e8f\u7684\u5355\u884c\u6570\u636e\u592a\u5927\uff0c\u53ef\u4ee5\u9009\u62e9 rowid \u6392\u5e8f\uff1a<\/p>\n

      \n
    1. \u521d\u59cb\u5316 sort_buffer\uff0c\u786e\u5b9a\u76ee\u6807\u5b57\u6bb5\u4e3a \u4e3b\u952e\u5217 \u548c \u6392\u5e8f\u5217\u3002<\/li>\n
    2. \u4ece\u7d22\u5f15\u4e2d\u627e\u5230\u7b2c\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684rowid\uff1b<\/li>\n
    3. \u5230\u4e3b\u952e\u7d22\u5f15\u53d6\u51fa\u6574\u884c\u6570\u636e\uff0c\u53d6\u51fa rowid \u548c \u6392\u5e8f\u5217\u653e\u5165 sort_buffer \uff1b<\/li>\n
    4. \u4ece\u7d22\u5f15\u53bb\u4e0b\u4e00\u4e2a rowid\uff1b<\/li>\n
    5. \u91cd\u590d\u6b65\u9aa4 3\u30014 \u76f4\u5230\u4e0d\u6ee1\u8db3\u6761\u4ef6\uff1b<\/li>\n
    6. \u5bf9 sort_buffer \u4e2d\u7684\u6570\u636e\u6309\u7167 \u6392\u5e8f\u5217\u8fdb\u884c\u6392\u5e8f\uff1b<\/li>\n
    7. \u904d\u5386\u6392\u5e8f\u7ed3\u679c\uff0c\u53d6\u51fa\u8981\u8fd4\u56de\u7684 rowid\uff0c\u6839\u636e rowid \u56de\u8868\u53d6\u51fa select \u5b50\u53e5\u6307\u5b9a\u7684\u5217\u8fd4\u56de\u7ed9\u5ba2\u6237\u7aef\u3002<\/li>\n<\/ol>\n

      \u7d22\u5f15\u6d88\u9664\u6392\u5e8f\u3001\u9700\u56de\u8868\u7684\u60c5\u51b5<\/h2>\n
        \n
      1. \u4ece\u7d22\u5f15\u627e\u5230\u7b2c\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684 rowid\uff1b<\/li>\n
      2. \u56de\u8868\u53d6\u51fa\u6574\u884c\u6570\u636e\uff0c\u53d6 select \u5b50\u53e5\u6307\u5b9a\u7684\u5217\uff0c\u4f5c\u4e3a\u7ed3\u679c\u96c6\u7684\u4e00\u90e8\u5206\u76f4\u63a5\u8fd4\u56de\uff1b<\/li>\n
      3. \u4ece\u7d22\u5f15\u53d6\u4e0b\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684 rowid\uff1b<\/li>\n
      4. \u91cd\u590d\u6b65\u9aa42\u30013\u76f4\u5230\u4e0d\u6ee1\u8db3\u6761\u4ef6\u3002<\/li>\n<\/ol>\n

        \u7d22\u5f15\u8986\u76d6\u7684\u60c5\u51b5<\/h2>\n
          \n
        1. \u4ece\u7d22\u5f15\u627e\u51fa\u7b2c\u4e00\u4e2a\u6ee1\u8db3\u6761\u4ef6\u7684\u8bb0\u5f55\uff0c\u53d6\u51fa select \u5b50\u53e5\u6307\u5b9a\u7684\u5217\u4f5c\u4e3a\u7ed3\u679c\u96c6\u7684\u4e00\u90e8\u5206\u76f4\u63a5\u8fd4\u56de\uff1b<\/li>\n
        2. \u4ece\u7d22\u5f15\u53d6\u4e0b\u4e00\u6761\u8bb0\u5f55\u901a\u7528\u53d6\u51fa select \u5b50\u53e5\u6307\u5b9a\u7684\u5217\u7684\u503c\u4f5c\u4e3a\u7ed3\u679c\u96c6\u7684\u4e00\u90e8\u5206\u76f4\u63a5\u8fd4\u56de\uff1b<\/li>\n
        3. \u91cd\u590d\u6267\u884c\u6b65\u9aa42\u76f4\u5230\u6ca1\u6709\u6ee1\u8db3\u6761\u4ef6\u7684\u3002<\/li>\n<\/ol>\n

          \u67e5\u770b\u6392\u5e8f\u76f8\u5173\u7684\u53c2\u6570\u503c<\/h2>\n
          mysql> show variables like '%sort%';\n+--------------------------------+--------------+\n| Variable_name                  | Value        |\n+--------------------------------+--------------+\n| innodb_disable_sort_file_cache | OFF          |\n| innodb_ft_sort_pll_degree      | 2            |\n| innodb_sort_buffer_size        | 1048576      |\n| max_length_for_sort_data       | 4096         |\n| max_sort_length                | 1024         |\n| myisam_max_sort_file_size      | 107374182400 |\n| myisam_sort_buffer_size        | 84934656     |\n| sort_buffer_size               | 262144       |\n+--------------------------------+--------------+\n8 rows in set, 1 warning (0.00 sec)\n<\/code><\/pre>\n
          max_length_for_sort_data<\/code> \u51b3\u5b9a\u6392\u5e8f\u7684\u884c\u6570\u636e\u7684\u957f\u5ea6\u3002<\/p>\n
          \n
          \u6b22\u8fce\u5173\u6ce8\u6211\u7684\u5fae\u4fe1\u516c\u4f17\u53f7: coderbee\u7b14\u8bb0<\/strong>\uff0c\u53ef\u4ee5\u66f4\u53ca\u65f6\u56de\u590d\u4f60\u7684\u8ba8\u8bba\u3002
          \n<\/p>\n","protected":false},"excerpt":{"rendered":"
          \u7528 explain \u547d\u4ee4\u67e5\u770b\u6267\u884c\u8ba1\u5212\u7684\u65f6\u5019\uff0cExtra \u5217\u7684\u503c\u542b\u6709 &#8220 … \u7ee7\u7eed\u9605\u8bfb →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[149,305,304],"_links":{"self":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/1774"}],"collection":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/comments?post=1774"}],"version-history":[{"count":4,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/1774\/revisions"}],"predecessor-version":[{"id":1778,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/1774\/revisions\/1778"}],"wp:attachment":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/media?parent=1774"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/categories?post=1774"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/tags?post=1774"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}