{"id":57567,"date":"2025-08-15T15:20:22","date_gmt":"2025-08-15T07:20:22","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/57567.html"},"modified":"2025-08-15T15:20:22","modified_gmt":"2025-08-15T07:20:22","slug":"%e7%a7%91%e6%99%ae%e6%96%87%ef%bc%9a%e8%bd%af%e4%bb%b6%e6%9e%b6%e6%9e%84%e6%95%b0%e6%8d%ae%e5%ba%93%e7%b3%bb%e5%88%97%e4%b9%8b%e3%80%90undo%e6%97%a5%e5%bf%97%e3%80%81%e7%89%88%e6%9c%ac%e9%93%be","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/57567.html","title":{"rendered":"\u79d1\u666e\u6587\uff1a\u8f6f\u4ef6\u67b6\u6784\u6570\u636e\u5e93\u7cfb\u5217\u4e4b\u3010undo\u65e5\u5fd7\u3001\u7248\u672c\u94fe\u3001Read View\u4e4b\u95f4\u7684\u5173\u8054\uff1aMySQL MVCC\u5b9e\u73b0\u539f\u7406\u3011"},"content":{"rendered":"<h2 style=\"background-color:transparent\">\u6982\u53d9<\/h2>\n<p>\u79d1\u666e\u6587&#xff1a;\u8f6f\u4ef6\u67b6\u6784\u6570\u636e\u5e93\u7cfb\u5217\u4e4b\u3010\u4e94\u5927 MVCC \u6838\u5fc3\u7ec4\u4ef6\u603b\u89c8&#xff1a;MySQL MVCC\u5b9e\u73b0\u539f\u7406\u3011-CSDN\u535a\u5ba2<\/p>\n<p>\u79d1\u666e\u6587&#xff1a;\u8f6f\u4ef6\u67b6\u6784\u6570\u636e\u5e93\u7cfb\u5217\u4e4b\u3010\u53ef\u89c1\u6027\u5224\u65ad\u51fd\u6570 changes_visible&#xff1a;\u6e90\u7801\u89e3\u8bfbMySQL MVCC\u5b9e\u73b0\u539f\u7406\u3011-CSDN\u535a\u5ba2<\/p>\n<p>\u79d1\u666e\u6587&#xff1a;\u8f6f\u4ef6\u67b6\u6784\u6570\u636e\u5e93\u7cfb\u5217\u4e4b\u3010MVCC&#xff1a;MySQL\u6570\u636e\u5e93&#xff0c;\u5355\u72ec\u4e00\u4e2asession\u4e2d\u7684select\u8bed\u53e5\u662f\u5426\u4f1a\u5f00\u542f\u4e8b\u52a1&#xff1f;\u3011-CSDN\u535a\u5ba2<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" alt=\"\" height=\"394\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/08\/20250815072010-689edfaa9db0a.png\" width=\"980\" \/><\/p>\n<p>\u200cundo\u65e5\u5fd7\u548c\u7248\u672c\u94fe\u5e76\u4e0d\u76f4\u63a5\u6784\u6210Read View&#xff0c;\u4f46\u5b83\u4eec\u5171\u540c\u5728InnoDB\u7684MVCC\u673a\u5236\u4e2d\u5b9e\u73b0\u4e86\u6570\u636e\u7684\u7248\u672c\u7ba1\u7406\u548c\u53ef\u89c1\u6027\u5224\u65ad\u200c\u3002<\/p>\n<p>undo\u65e5\u5fd7\u548c\u7248\u672c\u94fe\u5171\u540c\u8bb0\u5f55\u4e86\u6570\u636e\u7684\u5386\u53f2\u7248\u672c&#xff0c;\u5e76\u901a\u8fc7roll_pointer\u6307\u9488\u5c06\u8fd9\u4e9b\u7248\u672c\u8fde\u63a5\u8d77\u6765\u3002\u800cRead View\u5219\u7528\u4e8e\u5728\u6267\u884c\u67e5\u8be2\u64cd\u4f5c\u65f6\u5224\u65ad\u6570\u636e\u7248\u672c\u7684\u53ef\u89c1\u6027\u3002<\/p>\n<p>\u8fd9\u4e09\u8005\u534f\u540c\u5de5\u4f5c&#xff0c;\u5b9e\u73b0\u4e86InnoDB\u7684MVCC\u673a\u5236&#xff0c;\u4ece\u800c\u63d0\u9ad8\u4e86\u6570\u636e\u5e93\u7684\u5e76\u53d1\u6027\u80fd\u548c\u4e00\u81f4\u6027\u3002<\/p>\n<p>\u4e0b\u9762\u662f\u5bf9\u8fd9\u4e09\u8005\u5982\u4f55\u534f\u540c\u5de5\u4f5c\u7684\u8be6\u7ec6\u89e3\u91ca&#xff1a;<\/p>\n<h3 style=\"background-color:transparent\">1. undo\u65e5\u5fd7\u7684\u4f5c\u7528<\/h3>\n<p>undo\u65e5\u5fd7\u662fMySQL InnoDB\u5f15\u64ce\u7528\u4e8e\u8bb0\u5f55\u6570\u636e\u4fee\u6539\u524d\u7684\u72b6\u6001&#xff08;\u65e7\u503c&#xff09;\u7684\u65e5\u5fd7\u3002\u5f53\u4e8b\u52a1\u6267\u884c\u5931\u8d25\u6216\u9700\u8981\u56de\u6eda\u65f6&#xff0c;undo\u65e5\u5fd7\u63d0\u4f9b\u4e86\u6062\u590d\u6570\u636e\u4e00\u81f4\u6027\u7684\u624b\u6bb5\u3002\u6b64\u5916&#xff0c;undo\u65e5\u5fd7\u8fd8\u662f\u5b9e\u73b0MVCC\u673a\u5236\u7684\u5173\u952e\u7ec4\u6210\u90e8\u5206&#xff0c;\u56e0\u4e3a\u5b83\u4fdd\u5b58\u4e86\u6570\u636e\u7684\u5386\u53f2\u7248\u672c&#xff0c;\u4f7f\u5f97\u5176\u4ed6\u4e8b\u52a1\u5728\u8bfb\u53d6\u6570\u636e\u65f6\u53ef\u4ee5\u901a\u8fc7undo\u65e5\u5fd7\u83b7\u53d6\u65e7\u7248\u672c\u6570\u636e&#xff0c;\u4ece\u800c\u907f\u514d\u8bfb\u5199\u51b2\u7a81\u3002<\/p>\n<h3>2. \u7248\u672c\u94fe\u7684\u6784\u6210<\/h3>\n<p>\u7248\u672c\u94fe\u662f\u7531undo\u65e5\u5fd7\u901a\u8fc7roll_pointer\u6307\u9488\u8fde\u63a5\u5f62\u6210\u7684\u4e00\u4e2a\u5355\u5411\u94fe\u8868\u3002\u6bcf\u5f53\u4e00\u884c\u6570\u636e\u88ab\u4fee\u6539\u65f6&#xff0c;InnoDB\u4f1a\u4fdd\u7559\u4fee\u6539\u524d\u7684\u6570\u636e\u5230undo\u65e5\u5fd7\u4e2d&#xff0c;\u5e76\u901a\u8fc7roll_pointer\u6307\u9488\u5c06\u65b0\u7248\u672c\u7684\u8bb0\u5f55\u4e0e\u65e7\u7248\u672c\u7684undo\u65e5\u5fd7\u8fde\u63a5\u8d77\u6765\u3002\u8fd9\u6837&#xff0c;\u5c31\u5f62\u6210\u4e86\u4e00\u4e2a\u5305\u542b\u6570\u636e\u6240\u6709\u5386\u53f2\u7248\u672c\u7684\u7248\u672c\u94fe\u3002\u7248\u672c\u94fe\u7684\u94fe\u9996\u662f\u6700\u65b0\u7248\u672c\u7684\u6570\u636e\u8bb0\u5f55&#xff0c;\u800c\u94fe\u5c3e\u5219\u662f\u6570\u636e\u6700\u521d\u7684\u72b6\u6001\u6216\u67d0\u4e2a\u8f83\u65e9\u7684\u7248\u672c\u3002<\/p>\n<h3>3. Read View\u5982\u4f55\u5224\u65ad\u6570\u636e\u7248\u672c\u7684\u53ef\u89c1\u6027<\/h3>\n<p>Read View\u662fInnoDB\u5728\u6267\u884c\u5feb\u7167\u8bfb\u64cd\u4f5c\u65f6\u751f\u6210\u7684\u4e00\u4e2a\u4e00\u81f4\u6027\u89c6\u56fe\u3002\u5b83\u8bb0\u5f55\u4e86\u5f53\u524d\u7cfb\u7edf\u4e2d\u6240\u6709\u6d3b\u8dc3\u4e8b\u52a1\u7684\u4e8b\u52a1ID&#xff08;\u5373\u672a\u63d0\u4ea4\u7684\u4e8b\u52a1ID&#xff09;&#xff0c;\u4ee5\u53ca\u4e00\u4e2a\u6700\u5c0f\u6d3b\u8dc3\u4e8b\u52a1ID&#xff08;min_trx_id&#xff09;\u548c\u4e00\u4e2a\u8868\u793a\u4e0b\u4e00\u4e2a\u5f85\u5206\u914d\u4e8b\u52a1ID\u7684\u503c&#xff08;max_trx_id&#xff09;\u3002<\/p>\n<p>\u5f53\u4e8b\u52a1\u6267\u884c\u67e5\u8be2\u64cd\u4f5c\u65f6&#xff0c;InnoDB\u4f1a\u6839\u636eRead View\u548c\u7248\u672c\u94fe\u6765\u5224\u65ad\u6570\u636e\u7248\u672c\u7684\u53ef\u89c1\u6027\u3002\u5177\u4f53\u89c4\u5219\u5982\u4e0b&#xff1a;<\/p>\n<ul>\n<li>\u5982\u679c\u6570\u636e\u7248\u672c\u7684trx_id&#xff08;\u5373\u4fee\u6539\u8be5\u7248\u672c\u6570\u636e\u7684\u4e8b\u52a1ID&#xff09;\u5c0f\u4e8eRead View\u4e2d\u7684min_trx_id&#xff0c;\u8868\u793a\u8fd9\u4e2a\u6570\u636e\u7248\u672c\u662f\u5728\u5f53\u524d\u4e8b\u52a1\u5f00\u542f\u4e4b\u524d\u5c31\u5df2\u7ecf\u63d0\u4ea4\u7684\u4e8b\u52a1\u751f\u6210\u7684&#xff0c;\u56e0\u6b64\u5bf9\u5f53\u524d\u4e8b\u52a1\u53ef\u89c1\u3002<\/li>\n<li>\u5982\u679c\u6570\u636e\u7248\u672c\u7684trx_id\u5927\u4e8e\u6216\u7b49\u4e8eRead View\u4e2d\u7684max_trx_id&#xff0c;\u8868\u793a\u8fd9\u4e2a\u6570\u636e\u7248\u672c\u662f\u7531\u5c06\u6765\u542f\u52a8\u7684\u4e8b\u52a1\u751f\u6210\u7684&#xff0c;\u56e0\u6b64\u5bf9\u5f53\u524d\u4e8b\u52a1\u4e0d\u53ef\u89c1&#xff08;\u4f46\u5982\u679c\u6570\u636e\u7248\u672c\u7684trx_id\u6070\u597d\u662f\u5f53\u524d\u4e8b\u52a1\u81ea\u5df1\u7684ID&#xff0c;\u5219\u53ef\u89c1&#xff09;\u3002<\/li>\n<li>\u5982\u679c\u6570\u636e\u7248\u672c\u7684trx_id\u5728Read View\u7684min_trx_id\u548cmax_trx_id\u4e4b\u95f4&#xff0c;\u5219\u9700\u8981\u8fdb\u4e00\u6b65\u5224\u65ad\u3002\u5982\u679ctrx_id\u5728Read View\u7684\u6d3b\u8dc3\u4e8b\u52a1ID\u5217\u8868&#xff08;m_ids&#xff09;\u4e2d&#xff0c;\u8868\u793a\u751f\u6210\u8be5\u6570\u636e\u7248\u672c\u7684\u4e8b\u52a1\u4ecd\u7136\u6d3b\u8dc3&#xff08;\u672a\u63d0\u4ea4&#xff09;&#xff0c;\u56e0\u6b64\u8be5\u6570\u636e\u7248\u672c\u5bf9\u5f53\u524d\u4e8b\u52a1\u4e0d\u53ef\u89c1\u3002\u5982\u679ctrx_id\u4e0d\u5728m_ids\u4e2d&#xff0c;\u5219\u8868\u793a\u751f\u6210\u8be5\u6570\u636e\u7248\u672c\u7684\u4e8b\u52a1\u5df2\u7ecf\u63d0\u4ea4&#xff0c;\u56e0\u6b64\u8be5\u6570\u636e\u7248\u672c\u5bf9\u5f53\u524d\u4e8b\u52a1\u53ef\u89c1\u3002<\/li>\n<\/ul>\n<h2>\u4e09\u8005\u4e4b\u95f4\u7684\u5173\u7cfb&#xff1a;MySQL MVCC\u5b9e\u73b0\u539f\u7406<\/h2>\n<table>\n<tr>\u7ec4\u4ef6\u6838\u5fc3\u529f\u80fd\u4e0e\u5176\u4ed6\u7ec4\u4ef6\u7684\u5173\u8054<\/tr>\n<tbody>\n<tr>\n<td>undo \u65e5\u5fd7<\/td>\n<td>\u5b58\u50a8\u6570\u636e\u4fee\u6539\u524d\u7684\u65e7\u503c&#xff0c;\u662f\u7248\u672c\u94fe\u4e2d\u5386\u53f2\u7248\u672c\u7684\u7269\u7406\u8f7d\u4f53<\/td>\n<td>\u4e3a\u7248\u672c\u94fe\u63d0\u4f9b\u6bcf\u4e2a\u5386\u53f2\u7248\u672c\u7684\u5177\u4f53\u6570\u636e\u5185\u5bb9&#xff1b;\u901a\u8fc7 DB_ROLL_PTR \u88ab\u4e32\u8054\u6210\u94fe\u5f0f\u7ed3\u6784<\/td>\n<\/tr>\n<tr>\n<td>\u7248\u672c\u94fe<\/td>\n<td>\u901a\u8fc7 DB_ROLL_PTR \u5c06\u5f53\u524d\u884c\u4e0e\u591a\u4e2a undo \u65e5\u5fd7\u5173\u8054&#xff0c;\u5f62\u6210\u6309\u65f6\u95f4\u5012\u5e8f\u7684\u5386\u53f2\u7248\u672c\u94fe<\/td>\n<td>\u4f9d\u8d56 undo \u65e5\u5fd7\u5b58\u50a8\u5386\u53f2\u6570\u636e&#xff1b;\u4e3a Read View \u63d0\u4f9b\u53ef\u56de\u6eaf\u7684\u591a\u4e2a\u7248\u672c\u4f9b\u53ef\u89c1\u6027\u5224\u65ad<\/td>\n<\/tr>\n<tr>\n<td>Read View<\/td>\n<td>\u5b9a\u4e49\u5f53\u524d\u4e8b\u52a1\u7684\u53ef\u89c1\u4e8b\u52a1\u8303\u56f4\u4e0e\u89c4\u5219&#xff08;\u5982\u54ea\u4e9b\u4e8b\u52a1ID\u63d0\u4ea4\u7684\u7248\u672c\u53ef\u89c1&#xff09;<\/td>\n<td>\u57fa\u4e8e\u7248\u672c\u94fe\u4e2d\u7684 DB_TRX_ID \u548c undo \u65e5\u5fd7\u4e2d\u7684\u5386\u53f2\u7248\u672c&#xff0c;\u5224\u65ad\u5177\u4f53\u54ea\u4e2a\u7248\u672c\u5bf9\u5f53\u524d\u4e8b\u52a1\u53ef\u89c1<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<ul>\n<li>\u5173\u8054\u7ebd\u5e26&#xff1a;DB_ROLL_PTR\u662f\u8fde\u63a5\u5f53\u524d\u884c\u6570\u636e\u4e0e\u5176\u5386\u53f2\u7248\u672cundo\u65e5\u5fd7\u7684\u201c\u6307\u9488\u201d&#xff0c;\u901a\u8fc7\u5355\u5411\u94fe\u8868\u7ed3\u6784\u5f62\u6210\u7248\u672c\u94fe\u3002<\/li>\n<li>\u7248\u672c\u94fe\u65b9\u5411&#xff1a;\u94fe\u9996\u662f\u5f53\u524d\u6700\u65b0\u7248\u672c&#xff08;\u6570\u636e\u884c\u672c\u8eab&#xff09;&#xff0c;\u94fe\u5c3e\u662f\u6700\u65e9\u7684\u5386\u53f2\u7248\u672c&#xff08;\u6700\u4e45\u8fdc\u7684undo\u65e5\u5fd7&#xff09;&#xff1b;\u6bcf\u6b21\u66f4\u65b0\u64cd\u4f5c\u4f1a\u751f\u6210\u65b0undo\u65e5\u5fd7&#xff0c;\u5e76\u5c06DB_ROLL_PTR\u6307\u5411\u65b0\u65e5\u5fd7\u3002<\/li>\n<li>MVCC\u4f9d\u8d56&#xff1a;\u4e8b\u52a1\u901a\u8fc7Read View\u5224\u65ad\u5f53\u524d\u7248\u672c\u662f\u5426\u53ef\u89c1&#xff0c;\u4e0d\u53ef\u89c1\u65f6\u6cbfDB_ROLL_PTR\u56de\u6eaf\u7248\u672c\u94fe&#xff0c;\u627e\u5230\u6ee1\u8db3\u9694\u79bb\u7ea7\u522b\u8981\u6c42\u7684\u5386\u53f2\u7248\u672c\u6570\u636e&#xff08;\u5982REPEATABLE READ\u4e0b\u8bfb\u53d6\u4e8b\u52a1\u5f00\u59cb\u65f6\u7684\u5feb\u7167\u7248\u672c&#xff09;\u3002<\/li>\n<li>Undo\u65e5\u5fd7\u4f5c\u7528&#xff1a;\u4e0d\u4ec5\u7528\u4e8e\u4e8b\u52a1\u56de\u6eda&#xff0c;\u66f4\u662fMVCC\u591a\u7248\u672c\u6570\u636e\u7684\u7269\u7406\u5b58\u50a8\u8f7d\u4f53&#xff0c;\u901a\u8fc7\u7248\u672c\u94fe\u5b9e\u73b0\u4e0d\u540c\u4e8b\u52a1\u8bfb\u53d6\u4e0d\u540c\u65f6\u95f4\u70b9\u7684\u6570\u636e\u72b6\u6001\u3002<\/li>\n<\/ul>\n<p>\u7b80\u8a00\u4e4b&#xff0c;InnoDB\u901a\u8fc7DB_ROLL_PTR\u5c06\u6bcf\u884c\u6570\u636e\u7684\u5f53\u524d\u7248\u672c\u4e0e\u5386\u53f2undo\u65e5\u5fd7\u4e32\u8054\u6210\u7248\u672c\u94fe&#xff0c;\u518d\u7ed3\u5408Read View\u7684\u53ef\u89c1\u6027\u5224\u65ad\u903b\u8f91&#xff0c;\u5b9e\u73b0MVCC\u7684\u591a\u7248\u672c\u6570\u636e\u9694\u79bb\u4e0e\u8bbf\u95ee\u3002<\/p>\n<h3>\u4e00\u3001\u6838\u5fc3\u7ec4\u4ef6\u5b9a\u4e49<\/h3>\n<h4 style=\"background-color:transparent\">1.\u00a0undo \u65e5\u5fd7&#xff08;Update Undo Log&#xff09;<\/h4>\n<ul>\n<li>\u4f5c\u7528&#xff1a;\u8bb0\u5f55\u6570\u636e\u884c\u4fee\u6539\u524d\u7684\u65e7\u503c&#xff08;\u5982 UPDATE\/DELETE \u64cd\u4f5c\u524d\u7684\u5b57\u6bb5\u503c&#xff09;&#xff0c;\u7528\u4e8e\u652f\u6301\u4e8b\u52a1\u56de\u6eda\u548c MVCC \u5386\u53f2\u7248\u672c\u6570\u636e\u83b7\u53d6\u3002<\/li>\n<li>\u5b58\u50a8\u4f4d\u7f6e&#xff1a;\u5199\u5165 undo \u9875&#xff08;\u72ec\u7acb\u4e8e\u6570\u636e\u9875\u7684\u5b58\u50a8\u533a\u57df&#xff09;&#xff0c;\u5305\u542b\u88ab\u4fee\u6539\u884c\u7684\u539f\u59cb\u6570\u636e\u5185\u5bb9\u53ca\u5173\u8054\u7684\u4e8b\u52a1\u4fe1\u606f\u3002<\/li>\n<li>\u7c7b\u578b&#xff1a;\u4ec5 Update Undo Log&#xff08;\u7528\u4e8e MVCC \u548c\u56de\u6eda&#xff09;&#xff0c;Insert Undo Log&#xff08;\u4ec5\u7528\u4e8e\u56de\u6eda&#xff0c;\u4e8b\u52a1\u63d0\u4ea4\u540e\u53ef\u5220\u9664&#xff09;\u3002<\/li>\n<li>\n<p>1.\u00a0DB_ROLL_PTR&#xff08;\u56de\u6eda\u6307\u9488&#xff09;<\/p>\n<ul>\n<li>\u662fInnoDB\u6bcf\u884c\u6570\u636e\u8bb0\u5f55&#xff08;\u805a\u7c07\u7d22\u5f15\u9875\u5185&#xff09;\u7684\u9690\u85cf\u5b57\u6bb5\u4e4b\u4e00&#xff0c;\u7c7b\u578b\u4e3a\u6307\u9488&#xff08;\u901a\u5e38\u5b58\u50a8undo\u9875\u7684\u504f\u79fb\u5730\u5740\u6216\u9875\u5185\u4f4d\u7f6e\u4fe1\u606f&#xff09;\u3002<\/li>\n<li>\u4f5c\u7528&#xff1a;\u6307\u5411\u8be5\u884c\u6700\u8fd1\u4e00\u6b21\u4fee\u6539&#xff08;INSERT\/UPDATE&#xff09;\u6240\u751f\u6210\u7684undo\u65e5\u5fd7\u8bb0\u5f55&#xff0c;\u662f\u4e32\u8054\u5386\u53f2\u7248\u672c\u7684\u5173\u952e\u201c\u94fe\u6761\u201d\u3002<\/li>\n<\/ul>\n<\/li>\n<li>\n<p>2.\u00a0Undo\u65e5\u5fd7&#xff08;Update Undo Log&#xff09;<\/p>\n<ul>\n<li>\u5f53\u4e8b\u52a1\u5bf9\u67d0\u884c\u6570\u636e\u6267\u884cUPDATE\u6216DELETE\u64cd\u4f5c\u65f6&#xff0c;InnoDB\u00a0\u4e0d\u4f1a\u76f4\u63a5\u8986\u76d6\u539f\u6570\u636e&#xff0c;\u800c\u662f\u5c06\u4fee\u6539\u524d\u7684\u65e7\u503c&#xff08;\u5373\u88ab\u66f4\u65b0\u5b57\u6bb5\u7684\u539f\u5185\u5bb9&#xff09;\u5199\u5165undo\u65e5\u5fd7&#xff08;\u5b58\u4e8eundo\u9875\u4e2d&#xff09;\u3002<\/li>\n<li>\u8be5undo\u65e5\u5fd7\u8bb0\u5f55\u4e86\u6570\u636e\u4fee\u6539\u524d\u7684\u5b8c\u6574\u72b6\u6001&#xff08;\u6216\u90e8\u5206\u5173\u952e\u5b57\u6bb5&#xff09;&#xff0c;\u7528\u4e8e\u652f\u6301\u4e8b\u52a1\u56de\u6eda&#xff08;\u56de\u9000\u5230\u4fee\u6539\u524d\u72b6\u6001&#xff09;\u548cMVCC&#xff08;\u63d0\u4f9b\u5386\u53f2\u7248\u672c\u6570\u636e&#xff09;\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h4>2.\u00a0\u7248\u672c\u94fe&#xff08;Version Chain&#xff09;<\/h4>\n<ul>\n<li>\u4f5c\u7528&#xff1a;\u901a\u8fc7 DB_ROLL_PTR&#xff08;\u56de\u6eda\u6307\u9488&#xff09;\u5c06\u540c\u4e00\u884c\u6570\u636e\u7684\u4e0d\u540c\u5386\u53f2\u7248\u672c&#xff08;\u5305\u62ec\u5f53\u524d\u7248\u672c&#xff09;\u4e32\u8054\u6210\u5355\u5411\u94fe\u8868&#xff0c;\u5b9e\u73b0\u6309\u65f6\u95f4\u5012\u5e8f\u7684\u5386\u53f2\u7248\u672c\u8ffd\u6eaf\u3002<\/li>\n<li>\u7ed3\u6784&#xff1a;\u94fe\u9996\u662f\u5f53\u524d\u6700\u65b0\u7248\u672c\u7684\u6570\u636e\u884c&#xff08;\u5b58\u50a8\u4e8e\u6570\u636e\u9875&#xff09;&#xff0c;\u94fe\u4e2d\u6bcf\u4e2a\u8282\u70b9\u901a\u8fc7 DB_ROLL_PTR \u6307\u5411\u4e0b\u4e00\u4e2a\u66f4\u65e9\u7684 undo \u65e5\u5fd7\u8bb0\u5f55&#xff08;\u5373\u4e0a\u4e00\u7248\u672c\u7684\u6570\u636e&#xff09;&#xff0c;\u6700\u7ec8\u5f62\u6210\u201c\u5f53\u524d\u884c\u2192undo \u65e5\u5fd71\u2192undo \u65e5\u5fd72\u2192\u2026\u201d\u7684\u94fe\u5f0f\u7ed3\u6784\u3002<\/li>\n<\/ul>\n<h4>3.\u00a0Read View&#xff08;\u8bfb\u89c6\u56fe&#xff09;<\/h4>\n<ul>\n<li>\u4f5c\u7528&#xff1a;\u5b9a\u4e49\u5f53\u524d\u4e8b\u52a1\u7684\u53ef\u89c1\u4e8b\u52a1\u8303\u56f4\u4e0e\u6570\u636e\u7248\u672c\u89c4\u5219&#xff0c;\u662f\u5224\u65ad\u67d0\u884c\u6570\u636e\u7248\u672c\u662f\u5426\u5bf9\u5f53\u524d\u4e8b\u52a1\u53ef\u89c1\u7684\u903b\u8f91\u4f9d\u636e\u3002<\/li>\n<li>\u5173\u952e\u5b57\u6bb5&#xff1a;<\/li>\n<li>creator_trx_id&#xff08;\u521b\u5efa\u8be5\u89c6\u56fe\u7684\u4e8b\u52a1ID&#xff09;\u3001up_limit_id&#xff08;\u6700\u5c0f\u53ef\u89c1\u4e8b\u52a1ID&#xff09;\u3001low_limit_id&#xff08;\u6700\u5927\u4e0d\u53ef\u89c1\u4e8b\u52a1ID&#xff09;\u3001trx_ids[]&#xff08;\u521b\u5efa\u89c6\u56fe\u65f6\u4ecd\u6d3b\u8dc3\u7684\u672a\u63d0\u4ea4\u4e8b\u52a1ID\u96c6\u5408&#xff09;\u3002<\/li>\n<li>\u751f\u547d\u5468\u671f&#xff1a;\u5728\u4e8b\u52a1\u9996\u6b21\u6267\u884c SELECT \u65f6\u521b\u5efa&#xff08;REPEATABLE READ \u9694\u79bb\u7ea7\u522b\u4e0b\u590d\u7528&#xff0c;READ COMMITTED \u4e0b\u53ef\u80fd\u6bcf\u6b21\u65b0\u5efa&#xff09;\u3002<\/li>\n<\/ul>\n<h3>\u4e8c\u3001\u4e09\u8005\u7684\u5173\u8054\u6d41\u7a0b<\/h3>\n<h4>1.\u00a0\u6570\u636e\u4fee\u6539\u4e0e\u7248\u672c\u94fe\u6784\u5efa&#xff08;\u901a\u8fc7 undo \u65e5\u5fd7&#xff09;<\/h4>\n<ul>\n<li>\u5f53\u4e8b\u52a1\u5bf9\u67d0\u884c\u6570\u636e\u6267\u884c\u00a0UPDATE \u6216 DELETE\u00a0\u65f6&#xff1a;<\/li>\n<\/ul>\n<p>\u2460 InnoDB\u00a0\u4e0d\u4f1a\u76f4\u63a5\u8986\u76d6\u539f\u6570\u636e&#xff0c;\u800c\u662f\u5148\u5c06\u5f53\u524d\u884c\u7684\u539f\u59cb\u6570\u636e&#xff08;\u5373\u4fee\u6539\u524d\u7684\u503c&#xff09;\u5199\u5165 undo \u65e5\u5fd7&#xff08;\u751f\u6210\u4e00\u6761 Update Undo Log \u8bb0\u5f55&#xff09;&#xff1b;<\/p>\n<p>\u2461 \u66f4\u65b0\u6570\u636e\u9875\u4e2d\u7684\u5f53\u524d\u884c\u5185\u5bb9&#xff08;\u65b0\u503c&#xff09;&#xff0c;\u5e76\u4fee\u6539\u8be5\u884c\u7684 DB_TRX_ID&#xff08;\u4e8b\u52a1ID&#xff09;\u4e3a\u5f53\u524d\u4e8b\u52a1ID&#xff1b;<\/p>\n<p>\u2462 \u5c06\u5f53\u524d\u884c\u7684\u00a0DB_ROLL_PTR \u6307\u9488\u6307\u5411\u521a\u5199\u5165\u7684 undo \u65e5\u5fd7\u8bb0\u5f55&#xff08;\u5373\u8be5\u884c\u7684\u7b2c\u4e00\u4e2a\u5386\u53f2\u7248\u672c&#xff09;\u3002<\/p>\n<\/p>\n<ul>\n<li>\u82e5\u540c\u4e00\u884c\u6570\u636e\u88ab\u00a0\u591a\u6b21\u66f4\u65b0&#xff08;\u5982\u4e8b\u52a1 T1 \u66f4\u65b0\u540e&#xff0c;\u4e8b\u52a1 T2 \u518d\u6b21\u66f4\u65b0&#xff09;&#xff1a;\u6bcf\u6b21\u66f4\u65b0\u90fd\u4f1a\u751f\u6210\u65b0\u7684 undo \u65e5\u5fd7&#xff08;\u8bb0\u5f55\u5f53\u524d\u7248\u672c\u7684\u65e7\u503c&#xff09;&#xff0c;\u5e76\u5c06 DB_ROLL_PTR \u6307\u5411\u6700\u65b0\u7684 undo \u65e5\u5fd7&#xff0c;\u5f62\u6210\u00a0\u201c\u5f53\u524d\u884c\u2192\u6700\u65b0 undo \u65e5\u5fd7\u2192\u6b21\u65b0 undo \u65e5\u5fd7\u2192\u2026\u201d \u7684\u5355\u5411\u7248\u672c\u94fe&#xff08;\u94fe\u9996\u662f\u5f53\u524d\u6700\u65b0\u7248\u672c&#xff0c;\u94fe\u5c3e\u662f\u6700\u65e9\u7248\u672c&#xff09;\u3002<\/li>\n<\/ul>\n<h4>2.\u00a0\u4e8b\u52a1\u8bfb\u53d6\u6570\u636e\u65f6\u901a\u8fc7 Read View \u5224\u65ad\u53ef\u89c1\u6027<\/h4>\n<ul>\n<li>\u5f53\u4e8b\u52a1 T \u6267\u884c SELECT \u67e5\u8be2\u65f6&#xff1a;<\/li>\n<\/ul>\n<p>\u2460 InnoDB \u4f1a\u5148\u83b7\u53d6\u5f53\u524d\u4e8b\u52a1\u7684\u00a0Read View&#xff08;\u6839\u636e\u9694\u79bb\u7ea7\u522b\u51b3\u5b9a\u662f\u5426\u590d\u7528\u5df2\u6709\u89c6\u56fe&#xff09;&#xff1b;<\/p>\n<p>\u2461 \u4ece\u6570\u636e\u9875\u4e2d\u8bfb\u53d6\u76ee\u6807\u884c\u7684\u00a0\u5f53\u524d\u7248\u672c&#xff08;\u5373\u6700\u65b0\u6570\u636e\u884c&#xff09;&#xff0c;\u68c0\u67e5\u5176 DB_TRX_ID&#xff08;\u6700\u540e\u4fee\u6539\u4e8b\u52a1ID&#xff09;\u662f\u5426\u5bf9\u5f53\u524d\u4e8b\u52a1\u53ef\u89c1&#xff08;\u901a\u8fc7\u00a0changes_visible\u00a0\u51fd\u6570&#xff0c;\u7ed3\u5408 Read View \u7684\u00a0up_limit_id\u3001low_limit_id\u00a0\u548c\u00a0trx_ids[]\u00a0\u5224\u65ad&#xff09;&#xff1b;<\/p>\n<ul>\n<li>\u82e5\u53ef\u89c1&#xff08;\u5982 DB_TRX_ID \u5c5e\u4e8e\u5df2\u63d0\u4ea4\u4e8b\u52a1\u4e14\u5728\u5141\u8bb8\u8303\u56f4\u5185&#xff09;&#xff0c;\u76f4\u63a5\u8fd4\u56de\u8be5\u7248\u672c\u6570\u636e&#xff1b;<\/li>\n<li>\u82e5\u4e0d\u53ef\u89c1&#xff08;\u5982 DB_TRX_ID \u662f\u672a\u63d0\u4ea4\u4e8b\u52a1\u6216\u665a\u4e8e\u5f53\u524d\u89c6\u56fe\u7684\u4e8b\u52a1&#xff09;&#xff0c;\u5219\u9700\u8981\u901a\u8fc7\u7248\u672c\u94fe\u56de\u6eaf\u3002<\/li>\n<\/ul>\n<h4>3.\u00a0\u7248\u672c\u94fe\u56de\u6eaf\u4e0e\u5386\u53f2\u7248\u672c\u53ef\u89c1\u6027\u5224\u65ad<\/h4>\n<ul>\n<li>\u82e5\u5f53\u524d\u7248\u672c\u4e0d\u53ef\u89c1&#xff0c;InnoDB \u4f1a\u6839\u636e\u5f53\u524d\u884c\u7684\u00a0DB_ROLL_PTR \u6307\u9488&#xff0c;\u5b9a\u4f4d\u5230\u5bf9\u5e94\u7684 undo \u65e5\u5fd7\u8bb0\u5f55&#xff08;\u5373\u4e0a\u4e00\u5386\u53f2\u7248\u672c\u7684\u6570\u636e&#xff09;&#xff0c;\u4ece\u4e2d\u63d0\u53d6\u8be5\u7248\u672c\u7684\u5b8c\u6574\u6570\u636e\u5185\u5bb9&#xff0c;\u5e76\u68c0\u67e5\u8be5\u7248\u672c\u7684 DB_TRX_ID&#xff08;\u8bb0\u5f55\u5728 undo \u65e5\u5fd7\u6216\u5173\u8054\u4fe1\u606f\u4e2d&#xff09;\u662f\u5426\u5bf9\u5f53\u524d\u4e8b\u52a1\u53ef\u89c1&#xff1a;<\/li>\n<li>\u82e5\u53ef\u89c1&#xff08;\u5982\u8be5\u5386\u53f2\u7248\u672c\u7684 DB_TRX_ID \u5df2\u63d0\u4ea4\u4e14\u7b26\u5408 Read View \u89c4\u5219&#xff09;&#xff0c;\u8fd4\u56de\u8be5\u5386\u53f2\u7248\u672c\u6570\u636e&#xff1b;<\/li>\n<li>\u82e5\u4ecd\u4e0d\u53ef\u89c1&#xff0c;\u7ee7\u7eed\u901a\u8fc7\u8be5\u5386\u53f2\u7248\u672c\u8bb0\u5f55\u4e2d\u7684 DB_ROLL_PTR \u6307\u9488&#xff0c;\u56de\u6eaf\u5230\u66f4\u65e9\u7684 undo \u65e5\u5fd7&#xff0c;\u91cd\u590d\u5224\u65ad\u8fc7\u7a0b&#xff0c;\u76f4\u5230\u627e\u5230\u53ef\u89c1\u7248\u672c\u6216\u904d\u5386\u5b8c\u6240\u6709\u5386\u53f2\u7248\u672c&#xff08;\u6700\u7ec8\u8fd4\u56de\u7a7a\u6216\u62a5\u9519&#xff09;\u3002<\/li>\n<\/ul>\n<h3 style=\"background-color:transparent\">\u4e09\u3001\u7248\u672c\u94fe\u7684\u6784\u5efa\u8fc7\u7a0b&#xff08;\u4ee5UPDATE\u4e3a\u4f8b&#xff09;<\/h3>\n<p>1.\u00a0\u521d\u59cb\u63d2\u5165&#xff08;INSERT&#xff09;&#xff1a;\u65b0\u63d2\u5165\u7684\u884c\u6570\u636e\u4f1a\u8bb0\u5f55\u5f53\u524d\u4e8b\u52a1\u7684DB_TRX_ID&#xff08;\u4e8b\u52a1ID&#xff09;&#xff0c;\u4f46\u6b64\u65f6\u65e0\u5386\u53f2\u7248\u672c&#xff0c;DB_ROLL_PTR\u901a\u5e38\u4e3aNULL&#xff08;\u6216\u6307\u5411\u65e0\u6548\u4f4d\u7f6e&#xff09;\u3002<\/p>\n<p>2.\u00a0\u9996\u6b21\u66f4\u65b0&#xff08;UPDATE&#xff09;&#xff1a;\u4e8b\u52a1T1\u4fee\u6539\u67d0\u884c\u6570\u636e\u65f6&#xff0c;InnoDB\u4f1a&#xff1a;<\/p>\n<p>\u2460 \u5c06\u8be5\u884c\u4fee\u6539\u524d\u7684\u65e7\u503c&#xff08;\u5373\u66f4\u65b0\u524d\u7684\u5b8c\u6574\u884c\u6216\u5173\u952e\u5b57\u6bb5&#xff09;\u5199\u5165undo\u65e5\u5fd7&#xff08;\u751f\u6210\u4e00\u6761Update Undo Log\u8bb0\u5f55&#xff09;&#xff1b;<\/p>\n<p>\u2461 \u66f4\u65b0\u5f53\u524d\u884c\u7684\u6570\u636e\u5185\u5bb9&#xff08;\u65b0\u503c&#xff09;&#xff1b;<\/p>\n<p>\u2462 \u5c06\u5f53\u524d\u884c\u7684DB_TRX_ID\u66f4\u65b0\u4e3aT1\u7684\u4e8b\u52a1ID&#xff1b;<\/p>\n<p>\u2463 \u5c06DB_ROLL_PTR\u6307\u5411\u521a\u521a\u5199\u5165\u7684undo\u65e5\u5fd7\u8bb0\u5f55&#xff08;\u5373\u8be5\u884c\u7684\u7b2c\u4e00\u4e2a\u5386\u53f2\u7248\u672c&#xff09;\u3002<\/p>\n<p>3.\u00a0\u540e\u7eed\u66f4\u65b0&#xff08;\u591a\u6b21UPDATE&#xff09;<\/p>\n<ul>\n<li>\u5f53\u540c\u4e00\u884c\u6570\u636e\u88ab\u4e8b\u52a1T2\u518d\u6b21\u66f4\u65b0\u65f6&#xff0c;InnoDB\u4f1a&#xff1a;<\/li>\n<\/ul>\n<p>\u2460 \u5c06\u5f53\u524d\u884c&#xff08;\u5373T1\u4fee\u6539\u540e\u7684\u7248\u672c&#xff09;\u7684\u5f53\u524d\u6570\u636e&#xff08;\u65e7\u503c&#xff09;\u5199\u5165\u65b0\u7684undo\u65e5\u5fd7&#xff1b;<\/p>\n<p>\u2461 \u66f4\u65b0\u5f53\u524d\u884c\u7684\u6570\u636e\u5185\u5bb9&#xff08;T2\u4fee\u6539\u7684\u65b0\u503c&#xff09;&#xff1b;<\/p>\n<p>\u2462 \u4fdd\u6301DB_TRX_ID\u4e3aT2\u7684\u4e8b\u52a1ID&#xff1b;<\/p>\n<p>\u2463\u00a0\u5c06DB_ROLL_PTR\u6307\u5411\u65b0\u5199\u5165\u7684undo\u65e5\u5fd7\u8bb0\u5f55&#xff08;\u8986\u76d6\u4e4b\u524d\u7684\u6307\u9488&#xff09;\u3002<\/p>\n<ul>\n<li>\u6700\u7ec8\u6548\u679c&#xff1a;DB_ROLL_PTR\u5f62\u6210\u4e00\u4e2a\u5355\u5411\u94fe\u8868&#xff0c;\u94fe\u9996\u662f\u5f53\u524d\u6700\u65b0\u7248\u672c\u7684\u6570\u636e\u884c&#xff0c;\u94fe\u4e2d\u6bcf\u4e2a\u8282\u70b9&#xff08;undo\u65e5\u5fd7&#xff09;\u4f9d\u6b21\u8bb0\u5f55\u4e86\u8be5\u884c\u66f4\u65e9\u7684\u5386\u53f2\u7248\u672c&#xff08;\u6309\u66f4\u65b0\u65f6\u95f4\u5012\u5e8f\u6392\u5217&#xff09;\u3002<\/li>\n<\/ul>\n<h3>\u56db\u3001\u7248\u672c\u94fe\u7684\u6784\u5efa\u8fc7\u7a0b&#xff08;\u8be6\u7ec6\u793a\u4f8b&#xff09;<\/h3>\n<h4 style=\"background-color:transparent\">1.\u57fa\u672c\u6570\u636e\u7ed3\u6784<\/h4>\n<p>InnoDB\u6bcf\u884c\u8bb0\u5f55\u90fd\u5305\u542b3\u4e2a\u9690\u85cf\u5b57\u6bb5&#xff1a;<\/p>\n<ul>\n<li>DB_TRX_ID(6\u5b57\u8282)&#xff1a;\u6700\u8fd1\u4fee\u6539\u8be5\u884c\u7684\u4e8b\u52a1ID<\/li>\n<li>DB_ROLL_PTR(7\u5b57\u8282)&#xff1a;\u56de\u6eda\u6307\u9488&#xff0c;\u6307\u5411undo\u65e5\u5fd7\u8bb0\u5f55<\/li>\n<li>DB_ROW_ID(6\u5b57\u8282)&#xff1a;\u884cID(\u9690\u85cf\u4e3b\u952e)<\/li>\n<\/ul>\n<p>undo\u65e5\u5fd7\u7c7b\u578b<\/p>\n<ul>\n<li>INSERT undo log&#xff1a;\u4ec5\u5728\u4e8b\u52a1\u56de\u6eda\u65f6\u9700\u8981&#xff0c;\u63d0\u4ea4\u540e\u53ef\u76f4\u63a5\u4e22\u5f03<\/li>\n<li>UPDATE undo log&#xff1a;\u7528\u4e8eMVCC\u548c\u4e8b\u52a1\u56de\u6eda&#xff0c;\u9700\u8981\u6301\u4e45\u5316<\/li>\n<\/ul>\n<h4>2.\u00a0\u7248\u672c\u94fe\u7684\u5f62\u6210\u8fc7\u7a0b<\/h4>\n<h5 style=\"background-color:transparent\">2.1 \u521d\u59cb\u63d2\u5165&#xff08;\u4e8b\u52a1ID&#061;100&#xff09;<\/h5>\n<p>&#8212; \u4e8b\u52a1ID&#061;100\u63d2\u5165\u4e00\u884c<br \/>\n INSERT INTO t VALUES(1, &#039;A&#039;); <\/p>\n<ul>\n<li>\u6570\u636e\u9875\u4e2d\u7684\u8bb0\u5f55&#xff1a;<\/li>\n<\/ul>\n<p>[DB_TRX_ID&#061;100, DB_ROLL_PTR&#061;null, 1, &#039;A&#039;] <\/p>\n<ul>\n<li>undo\u65e5\u5fd7&#xff1a;\u8bb0\u5f55\u63d2\u5165\u524d\u7684\u7a7a\u72b6\u6001(\u7528\u4e8e\u56de\u6eda)<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" alt=\"\" height=\"288\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/08\/20250815072013-689edfad74085.png\" width=\"477\" \/><\/p>\n<h5 style=\"background-color:transparent\">2.2 \u7b2c\u4e00\u6b21\u66f4\u65b0&#xff08;\u4e8b\u52a1ID&#061;200&#xff09;<\/h5>\n<p>&#8212; \u4e8b\u52a1ID&#061;200\u66f4\u65b0\u8be5\u884c<br \/>\nUPDATE t SET name&#061;&#039;B&#039; WHERE id&#061;1; <\/p>\n<li>\u5148\u62f7\u8d1d\u5f53\u524d\u884c\u5230undo log(\u5305\u542b\u4e8b\u52a1ID&#061;100\u7684\u4fe1\u606f)<\/li>\n<li>\u66f4\u65b0\u6570\u636e\u9875\u4e2d\u7684\u8bb0\u5f55&#xff1a;[DB_TRX_ID&#061;200, DB_ROLL_PTR\u2192undo1, 1, &#039;B&#039;]<\/li>\n<li>undo\u65e5\u5fd7\u5f62\u6210\u7248\u672c\u94fe&#xff1a;undo1: [DB_TRX_ID&#061;100, 1, &#039;A&#039;]<\/li>\n<p><img loading=\"lazy\" decoding=\"async\" alt=\"\" height=\"278\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/08\/20250815072014-689edfaedc96b.png\" width=\"479\" \/><\/p>\n<h5 style=\"background-color:transparent\">2.3 \u7b2c\u4e8c\u6b21\u66f4\u65b0&#xff08;\u4e8b\u52a1ID&#061;300&#xff09;<\/h5>\n<p>&#8212; \u4e8b\u52a1ID&#061;300\u518d\u6b21\u66f4\u65b0<br \/>\nUPDATE t SET name&#061;&#039;C&#039; WHERE id&#061;1; <\/p>\n<li>\u62f7\u8d1d\u5f53\u524d\u884c\u5230undo log(\u5305\u542b\u4e8b\u52a1ID&#061;200\u7684\u4fe1\u606f)<\/li>\n<li>\u66f4\u65b0\u6570\u636e\u9875&#xff1a;[DB_TRX_ID&#061;300, DB_ROLL_PTR\u2192undo2, 1, &#039;C&#039;]<\/li>\n<li>\u7248\u672c\u94fe\u53d8\u4e3a&#xff1a;undo2 \u2192 [DB_TRX_ID&#061;200, DB_ROLL_PTR\u2192undo1, 1, &#039;B&#039;] undo1 \u2192 [DB_TRX_ID&#061;100, 1, &#039;A&#039;]<\/li>\n<p><img loading=\"lazy\" decoding=\"async\" alt=\"\" height=\"506\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/08\/20250815072016-689edfb04e3a8.png\" width=\"492\" \/><\/p>\n<h4>3.MVCC\u53ef\u89c1\u6027\u5224\u65ad\u6d41\u7a0b\u56fe&#xff08;\u4e8b\u52a1ID&#061;250\u8bfb\u53d6\u65f6&#xff09;<\/h4>\n<h5 style=\"background-color:transparent\">3.1\u00a0 \u524d\u63d0&#xff1a;<\/h5>\n<ul>\n<li>\u5f53\u524d\u6d3b\u8dc3\u4e8b\u52a1ID\u8303\u56f4&#xff1a;\u5047\u8bbe\u65e0\u5176\u4ed6\u6d3b\u8dc3\u4e8b\u52a1&#xff0c;\u4e8b\u52a1250\u5f00\u59cb\u65f6&#xff0c;\u5df2\u63d0\u4ea4\u4e8b\u52a1ID\u2264200&#xff0c;\u672a\u63d0\u4ea4\u4e8b\u52a1ID&#061;300&#xff08;\u6b63\u5728\u66f4\u65b0&#xff09;\u3002<\/li>\n<li>\u6570\u636e\u9875\u5f53\u524d\u7248\u672c&#xff1a;DB_TRX_ID&#061;300&#xff08;\u672a\u63d0\u4ea4&#xff09;&#xff0c;\u7248\u672c\u94fe\u4e3a\u00a0300\u2192200\u2192100\u3002<\/li>\n<\/ul>\n<p>\u5f53\u67d0\u4e2a\u4e8b\u52a1(\u5982ID&#061;250)\u8bfb\u53d6\u8be5\u884c\u65f6&#xff1a;<\/p>\n<li>\u4ece\u5f53\u524d\u8bb0\u5f55\u5f00\u59cb\u904d\u5386\u7248\u672c\u94fe&#xff1a;\u5f53\u524d\u8bb0\u5f55(300)\u2192undo2(200)\u2192undo1(100)<\/li>\n<li>\u6839\u636e\u4e8b\u52a1\u9694\u79bb\u7ea7\u522b\u548cReadView\u5224\u65ad\u53ef\u89c1\u6027&#xff1a;\n<ul>\n<li>RC&#xff1a;\u53d6\u6700\u65b0\u5df2\u63d0\u4ea4\u7248\u672c<\/li>\n<li>RR&#xff1a;\u53d6\u4e8b\u52a1\u5f00\u59cb\u65f6\u5df2\u63d0\u4ea4\u7684\u6700\u65b0\u7248\u672c<\/li>\n<\/ul>\n<\/li>\n<li>\u5bf9\u4e8e\u4e8b\u52a1250&#xff1a;\n<ul>\n<li>300&gt;250\u4e0d\u53ef\u89c1<\/li>\n<li>200&lt;250\u4e14\u5df2\u63d0\u4ea4\u2192\u8fd4\u56de&#039;B&#039;<\/li>\n<li>(\u5982\u679c200\u672a\u63d0\u4ea4\u5219\u7ee7\u7eed\u627e100)<\/li>\n<\/ul>\n<\/li>\n<p><img loading=\"lazy\" decoding=\"async\" alt=\"\" height=\"632\" src=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/08\/20250815072018-689edfb206ad9.png\" width=\"848\" \/><\/p>\n<li>\u7248\u672c\u94fe\u6784\u5efa&#xff1a;\u901a\u8fc7\u6bcf\u884c\u8bb0\u5f55\u7684\u00a0DB_ROLL_PTR\u00a0\u6307\u5411 undo \u65e5\u5fd7&#xff0c;\u5f62\u6210\u5386\u53f2\u7248\u672c\u94fe\u8868&#xff0c;\u6700\u65b0\u7248\u672c\u5728\u6570\u636e\u9875&#xff0c;\u65e7\u7248\u672c\u5728 undo \u65e5\u5fd7\u4e2d\u3002<\/li>\n<li>\u53ef\u89c1\u6027\u5224\u65ad&#xff1a;\u4e8b\u52a1\u6839\u636e\u81ea\u8eab ID \u548c\u7248\u672c\u94fe\u4e2d\u6bcf\u4e2a\u7248\u672c\u7684\u00a0DB_TRX_ID&#xff08;\u7ed3\u5408\u4e8b\u52a1\u63d0\u4ea4\u72b6\u6001&#xff09;&#xff0c;\u4ece\u94fe\u9996&#xff08;\u6700\u65b0\u7248&#xff09;\u5411\u94fe\u5c3e&#xff08;\u6700\u65e7\u7248&#xff09;\u904d\u5386&#xff0c;\u627e\u5230\u7b2c\u4e00\u4e2a\u6ee1\u8db3\u53ef\u89c1\u6027\u89c4\u5219\u7684\u7248\u672c\u3002<\/li>\n<h5 style=\"background-color:transparent\">3.2 \u5173\u952e\u5b9e\u73b0\u7ec6\u8282<\/h5>\n<li>\n<p>\u7248\u672c\u94fe\u7ec4\u7ec7&#xff1a;<\/p>\n<ul>\n<li>\u901a\u8fc7DB_ROLL_PTR\u5f62\u6210\u5355\u5411\u94fe\u8868&#xff0c;\u6700\u65b0\u4fee\u6539\u5728\u94fe\u9996<\/li>\n<li>\u6bcf\u4e2aundo\u8bb0\u5f55\u5305\u542b\u524d\u4e00\u4e2a\u7248\u672c\u7684DB_TRX_ID\u548cDB_ROLL_PTR<\/li>\n<\/ul>\n<\/li>\n<li>\n<p>undo\u65e5\u5fd7\u6301\u4e45\u5316&#xff1a;<\/p>\n<ul>\n<li>\u5b58\u50a8\u5728\u7cfb\u7edf\u8868\u7a7a\u95f4\u7684\u56de\u6eda\u6bb5(rollback segment)\u4e2d<\/li>\n<li>update undo\u65e5\u5fd7\u5728\u4e8b\u52a1\u63d0\u4ea4\u540e\u4e0d\u4f1a\u7acb\u5373\u5220\u9664&#xff0c;\u8981\u786e\u4fddMVCC\u80fd\u8bfb\u5230<\/li>\n<\/ul>\n<\/li>\n<li>\n<p>purge\u673a\u5236&#xff1a;<\/p>\n<ul>\n<li>\u540e\u53f0\u7ebf\u7a0b\u5b9a\u671f\u6e05\u7406\u4e0d\u518d\u9700\u8981\u7684undo\u65e5\u5fd7<\/li>\n<li>\u5f53\u6ca1\u6709\u6d3b\u8dc3\u4e8b\u52a1\u9700\u8981\u8bbf\u95ee\u65e7\u7248\u672c\u65f6&#xff0c;\u5bf9\u5e94\u7684undo\u65e5\u5fd7\u53ef\u88ab\u6e05\u9664<\/li>\n<\/ul>\n<\/li>\n<li>\n<p>\u4e8c\u7ea7\u7d22\u5f15\u5904\u7406&#xff1a;<\/p>\n<ul>\n<li>\u4e8c\u7ea7\u7d22\u5f15\u4e0d\u76f4\u63a5\u5b58\u50a8\u7248\u672c\u4fe1\u606f<\/li>\n<li>\u901a\u8fc7\u4e3b\u952e\u56de\u8868\u67e5\u8be2\u65f6\u518d\u5e94\u7528MVCC\u89c4\u5219<\/li>\n<\/ul>\n<\/li>\n<h5 style=\"background-color:transparent\">3.3\u4e0d\u540c\u64cd\u4f5c\u7684\u5f71\u54cd<\/h5>\n<li>\n<p>DELETE\u64cd\u4f5c&#xff1a;<\/p>\n<ul>\n<li>\u6807\u8bb0\u5220\u9664\u8bb0\u5f55&#xff0c;\u521b\u5efadelete mark undo\u65e5\u5fd7<\/li>\n<li>\u53ea\u6709\u5728purge\u7ebf\u7a0b\u771f\u6b63\u6e05\u7406\u65f6\u624d\u7269\u7406\u5220\u9664<\/li>\n<\/ul>\n<\/li>\n<li>\n<p>UPDATE\u64cd\u4f5c\u5bfc\u81f4\u5217\u53d8\u5316&#xff1a;<\/p>\n<ul>\n<li>\u5982\u679c\u65b0\u884c\u4e0d\u80fd\u653e\u5728\u539f\u4f4d\u7f6e(\u5982\u53d8\u957f\u5217\u589e\u5927)<\/li>\n<li>\u91c7\u7528&#034;delete mark &#043; insert&#034;\u65b9\u5f0f&#xff0c;\u4ea7\u751f\u4e24\u6761undo\u8bb0\u5f55<\/li>\n<\/ul>\n<\/li>\n<p>\u8fd9\u79cd\u673a\u5236\u4f7f\u5f97InnoDB\u80fd\u591f&#xff1a;<\/p>\n<ul>\n<li>\u5b9e\u73b0\u975e\u9501\u5b9a\u8bfb(\u5feb\u7167\u8bfb)<\/li>\n<li>\u652f\u6301\u4e8b\u52a1\u56de\u6eda<\/li>\n<li>\u4fdd\u8bc1\u4e0d\u540c\u9694\u79bb\u7ea7\u522b\u4e0b\u7684\u53ef\u89c1\u6027\u89c4\u5219<\/li>\n<li>\u9ad8\u6548\u5904\u7406\u5e76\u53d1\u8bfb\u5199\u51b2\u7a81<\/li>\n<\/ul>\n<h3>4.MySQL MVCC\u673a\u5236\u4ee3\u7801\u793a\u4f8b<\/h3>\n<p>MVCC&#xff08;\u591a\u7248\u672c\u5e76\u53d1\u63a7\u5236&#xff09;\u662fInnoDB\u5b58\u50a8\u5f15\u64ce\u7684\u6838\u5fc3\u7279\u6027&#xff0c;\u4e0b\u9762\u6211\u5c06\u901a\u8fc7\u51e0\u4e2a\u4ee3\u7801\u793a\u4f8b\u6765\u5c55\u793aMVCC\u7684\u5de5\u4f5c\u539f\u7406\u3002<\/p>\n<h4>4.1 \u57fa\u672cMVCC\u884c\u4e3a\u793a\u4f8b<\/h4>\n<p>&#8212; \u521b\u5efa\u6d4b\u8bd5\u8868<br \/>\nCREATE TABLE mvcc_test (<br \/>\n    id INT PRIMARY KEY,<br \/>\n    data VARCHAR(100),<br \/>\n    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP<br \/>\n) ENGINE&#061;InnoDB;<\/p>\n<p>&#8212; \u63d2\u5165\u521d\u59cb\u6570\u636e<br \/>\nINSERT INTO mvcc_test (id, data) VALUES (1, &#039;Initial Data&#039;);<\/p>\n<p>&#8212; \u4e8b\u52a11 &#8211; \u8bfb\u53d6\u6570\u636e&#xff08;\u5feb\u7167\u8bfb&#xff09;<br \/>\nSTART TRANSACTION;<br \/>\nSELECT * FROM mvcc_test WHERE id &#061; 1;  &#8212; \u4f1a\u770b\u5230&#039;Initial Data&#039;<br \/>\n&#8212; \u6b64\u65f6\u4e0d\u63d0\u4ea4&#xff0c;\u4fdd\u6301\u4e8b\u52a1\u6253\u5f00<\/p>\n<p>&#8212; \u5728\u53e6\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\u6267\u884c&#xff1a;<br \/>\n&#8212; \u4e8b\u52a12 &#8211; \u66f4\u65b0\u6570\u636e<br \/>\nSTART TRANSACTION;<br \/>\nUPDATE mvcc_test SET data &#061; &#039;Updated Data&#039; WHERE id &#061; 1;<br \/>\nSELECT * FROM mvcc_test WHERE id &#061; 1;  &#8212; \u4f1a\u770b\u5230&#039;Updated Data&#039;<br \/>\nCOMMIT;<\/p>\n<p>&#8212; \u56de\u5230\u4e8b\u52a11 &#8211; \u518d\u6b21\u8bfb\u53d6&#xff08;\u4ecd\u7136\u770b\u5230\u65e7\u7248\u672c&#xff09;<br \/>\nSELECT * FROM mvcc_test WHERE id &#061; 1;  &#8212; \u4ecd\u7136\u770b\u5230&#039;Initial Data&#039;<br \/>\nCOMMIT;<\/p>\n<h4 style=\"background-color:transparent\">4.2 \u663e\u793a\u4e8b\u52a1ID\u548c\u7248\u672c\u4fe1\u606f\u7684\u793a\u4f8b<\/h4>\n<p>&#8212; \u542f\u7528\u4e8b\u52a1ID\u663e\u793a&#xff08;\u9700\u8981MySQL 8.0&#043;&#xff09;<br \/>\nSET SESSION innodb_status_output_locks&#061;ON;<br \/>\nSET SESSION innodb_status_output&#061;ON;<\/p>\n<p>&#8212; \u67e5\u770b\u4e8b\u52a1\u548c\u9501\u4fe1\u606f<br \/>\nSHOW ENGINE INNODB STATUS;<\/p>\n<p>&#8212; \u521b\u5efa\u5e26\u6709\u4e8b\u52a1ID\u8ddf\u8e2a\u7684\u8868<br \/>\nCREATE TABLE mvcc_with_tx (<br \/>\n    id INT PRIMARY KEY,<br \/>\n    data VARCHAR(100),<br \/>\n    tx_id BIGINT UNSIGNED,<br \/>\n    start_time TIMESTAMP,<br \/>\n    end_time TIMESTAMP<br \/>\n) ENGINE&#061;InnoDB;<\/p>\n<p>&#8212; \u521b\u5efa\u89e6\u53d1\u5668\u6765\u8ddf\u8e2a\u4e8b\u52a1<br \/>\nDELIMITER \/\/<br \/>\nCREATE TRIGGER before_mvcc_with_tx_insert<br \/>\nBEFORE INSERT ON mvcc_with_tx<br \/>\nFOR EACH ROW<br \/>\nBEGIN<br \/>\n    SET NEW.tx_id &#061; (SELECT txn_id FROM information_schema.innodb_trx<br \/>\n                     ORDER BY txn_started DESC LIMIT 1);<br \/>\n    SET NEW.start_time &#061; NOW();<br \/>\nEND\/\/<br \/>\nDELIMITER ;<\/p>\n<p>&#8212; \u6d4b\u8bd5\u4e8b\u52a1ID\u8ddf\u8e2a<br \/>\nSTART TRANSACTION;<br \/>\nINSERT INTO mvcc_with_tx (id, data) VALUES (1, &#039;Test Data&#039;);<br \/>\nCOMMIT;<\/p>\n<h4>4.3 MVCC\u4e0e\u9694\u79bb\u7ea7\u522b\u793a\u4f8b<\/h4>\n<p>&#8212; \u8bbe\u7f6e\u4e0d\u540c\u7684\u9694\u79bb\u7ea7\u522b\u5e76\u89c2\u5bdfMVCC\u884c\u4e3a<\/p>\n<p>&#8212; READ COMMITTED \u793a\u4f8b<br \/>\nSET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED;<br \/>\nSTART TRANSACTION;<br \/>\nSELECT * FROM mvcc_test WHERE id &#061; 1;  &#8212; \u4f1a\u770b\u5230\u5df2\u63d0\u4ea4\u7684\u66f4\u6539<br \/>\nCOMMIT;<\/p>\n<p>&#8212; REPEATABLE READ \u793a\u4f8b&#xff08;MySQL\u9ed8\u8ba4&#xff09;<br \/>\nSET SESSION TRANSACTION ISOLATION LEVEL REPEATABLE READ;<br \/>\nSTART TRANSACTION;<br \/>\nSELECT * FROM mvcc_test WHERE id &#061; 1;  &#8212; \u4f1a\u770b\u5230\u4e8b\u52a1\u5f00\u59cb\u65f6\u7684\u5feb\u7167<br \/>\n&#8212; \u5728\u53e6\u4e00\u4e2a\u4f1a\u8bdd\u4e2d\u66f4\u65b0\u6570\u636e\u5e76\u63d0\u4ea4<br \/>\n&#8212; \u518d\u6b21\u67e5\u8be2\u4ecd\u7136\u770b\u5230\u65e7\u6570\u636e<br \/>\nSELECT * FROM mvcc_test WHERE id &#061; 1;<br \/>\nCOMMIT;<\/p>\n<h4>4.4 \u6a21\u62dfMVCC\u7248\u672c\u94fe\u7684\u7b80\u5316\u5b9e\u73b0&#xff08;\u4f2a\u4ee3\u7801&#xff09;<\/h4>\n<p># \u7b80\u5316\u7684MVCC\u7248\u672c\u94fe\u6a21\u62df<br \/>\nclass MVCCRow:<br \/>\n    def __init__(self, data, tx_id, is_deleted&#061;False):<br \/>\n        self.data &#061; data<br \/>\n        self.tx_id &#061; tx_id  # \u521b\u5efa\u8be5\u7248\u672c\u7684\u4e8b\u52a1ID<br \/>\n        self.is_deleted &#061; is_deleted<br \/>\n        self.next &#061; None  # \u6307\u5411\u4e0b\u4e00\u4e2a\u7248\u672c<\/p>\n<p>class MVCCTable:<br \/>\n    def __init__(self):<br \/>\n        self.head &#061; None<br \/>\n        self.current_tx_id &#061; 0<\/p>\n<p>    def begin_transaction(self):<br \/>\n        self.current_tx_id &#043;&#061; 1<br \/>\n        return self.current_tx_id<\/p>\n<p>    def insert(self, data, tx_id):<br \/>\n        new_row &#061; MVCCRow(data, tx_id)<br \/>\n        new_row.next &#061; self.head<br \/>\n        self.head &#061; new_row<\/p>\n<p>    def update(self, data, tx_id, visible_tx_id):<br \/>\n        # \u627e\u5230\u5f53\u524d\u4e8b\u52a1\u53ef\u89c1\u7684\u6700\u65b0\u7248\u672c<br \/>\n        current &#061; self.head<br \/>\n        while current and current.tx_id &gt; visible_tx_id:<br \/>\n            current &#061; current.next<\/p>\n<p>        if current:<br \/>\n            new_row &#061; MVCCRow(data, tx_id)<br \/>\n            new_row.next &#061; current.next<br \/>\n            current.next &#061; new_row<\/p>\n<p>    def select(self, tx_id):<br \/>\n        current &#061; self.head<br \/>\n        result &#061; []<br \/>\n        while current:<br \/>\n            if current.tx_id &lt;&#061; tx_id and not current.is_deleted:<br \/>\n                result.append((current.data, current.tx_id))<br \/>\n            current &#061; current.next<br \/>\n        return result<\/p>\n<p># \u4f7f\u7528\u793a\u4f8b<br \/>\ntable &#061; MVCCTable()<br \/>\ntx1 &#061; table.begin_transaction()<br \/>\ntable.insert(&#034;Initial Data&#034;, tx1)<\/p>\n<p>tx2 &#061; table.begin_transaction()<br \/>\ntable.update(&#034;Updated Data&#034;, tx2, tx1)<\/p>\n<p>print(table.select(tx1))  # \u770b\u5230\u521d\u59cb\u6570\u636e<br \/>\nprint(table.select(tx2))  # \u770b\u5230\u66f4\u65b0\u540e\u7684\u6570\u636e<\/p>\n<p>\u5907\u6ce8&#xff1a;\u8fd9\u4e9b\u793a\u4f8b\u5c55\u793a\u4e86MVCC\u5728\u4e0d\u540c\u573a\u666f\u4e0b\u7684\u884c\u4e3a\u3002\u5728\u5b9e\u9645\u7684MySQL\u5b9e\u73b0\u4e2d&#xff0c;\u8fd9\u4e9b\u673a\u5236\u8981\u590d\u6742\u5f97\u591a&#xff0c;\u4f46\u57fa\u672c\u539f\u7406\u662f\u76f8\u540c\u7684&#xff1a;\u901a\u8fc7\u7ef4\u62a4\u6570\u636e\u7684\u591a\u4e2a\u7248\u672c\u6765\u5b9e\u73b0\u9ad8\u5e76\u53d1\u6027\u80fd&#xff0c;\u540c\u65f6\u4fdd\u6301\u6570\u636e\u4e00\u81f4\u6027\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u6587\u7ae0\u6d4f\u89c8\u9605\u8bfb302\u6b21\uff0c\u70b9\u8d5e11\u6b21\uff0c\u6536\u85cf5\u6b21\u3002\u200cundo\u65e5\u5fd7\u548c\u7248\u672c\u94fe\u5e76\u4e0d\u76f4\u63a5\u6784\u6210Read View\uff0c\u4f46\u5b83\u4eec\u5171\u540c\u5728InnoDB\u7684MVCC\u673a\u5236\u4e2d\u5b9e\u73b0\u4e86\u6570\u636e\u7684\u7248\u672c\u7ba1\u7406\u548c\u53ef\u89c1\u6027\u5224\u65ad\u200c\u3002undo\u65e5\u5fd7\u548c\u7248\u672c\u94fe\u5171\u540c\u8bb0\u5f55\u4e86\u6570\u636e\u7684\u5386\u53f2\u7248\u672c\uff0c\u5e76\u901a\u8fc7roll_pointer\u6307\u9488\u5c06\u8fd9\u4e9b\u7248\u672c\u8fde\u63a5\u8d77\u6765\u3002\u800cRead View\u5219\u7528\u4e8e\u5728\u6267\u884c\u67e5\u8be2\u64cd\u4f5c\u65f6\u5224\u65ad\u6570\u636e\u7248\u672c\u7684\u53ef\u89c1\u6027\u3002\u8fd9\u4e09\u8005\u534f\u540c\u5de5\u4f5c\uff0c\u5b9e\u73b0\u4e86InnoDB\u7684MVCC\u673a\u5236\uff0c\u4ece\u800c\u63d0\u9ad8\u4e86\u6570\u636e\u5e93\u7684\u5e76\u53d1\u6027\u80fd\u548c\u4e00\u81f4\u6027\u3002<\/p>\n","protected":false},"author":2,"featured_media":57562,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[6018,114,6021,6019,644,100,6020,646],"topic":[],"class_list":["post-57567","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-server","tag-mvcc","tag-mysql","tag-readview","tag-undo","tag-644","tag-100","tag-6020","tag-646"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v20.3 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ 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content=\"\u6587\u7ae0\u6d4f\u89c8\u9605\u8bfb302\u6b21\uff0c\u70b9\u8d5e11\u6b21\uff0c\u6536\u85cf5\u6b21\u3002\u200cundo\u65e5\u5fd7\u548c\u7248\u672c\u94fe\u5e76\u4e0d\u76f4\u63a5\u6784\u6210Read View\uff0c\u4f46\u5b83\u4eec\u5171\u540c\u5728InnoDB\u7684MVCC\u673a\u5236\u4e2d\u5b9e\u73b0\u4e86\u6570\u636e\u7684\u7248\u672c\u7ba1\u7406\u548c\u53ef\u89c1\u6027\u5224\u65ad\u200c\u3002undo\u65e5\u5fd7\u548c\u7248\u672c\u94fe\u5171\u540c\u8bb0\u5f55\u4e86\u6570\u636e\u7684\u5386\u53f2\u7248\u672c\uff0c\u5e76\u901a\u8fc7roll_pointer\u6307\u9488\u5c06\u8fd9\u4e9b\u7248\u672c\u8fde\u63a5\u8d77\u6765\u3002\u800cRead View\u5219\u7528\u4e8e\u5728\u6267\u884c\u67e5\u8be2\u64cd\u4f5c\u65f6\u5224\u65ad\u6570\u636e\u7248\u672c\u7684\u53ef\u89c1\u6027\u3002\u8fd9\u4e09\u8005\u534f\u540c\u5de5\u4f5c\uff0c\u5b9e\u73b0\u4e86InnoDB\u7684MVCC\u673a\u5236\uff0c\u4ece\u800c\u63d0\u9ad8\u4e86\u6570\u636e\u5e93\u7684\u5e76\u53d1\u6027\u80fd\u548c\u4e00\u81f4\u6027\u3002\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.wsisp.com\/helps\/57567.html\" \/>\n<meta property=\"og:site_name\" content=\"\u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\" \/>\n<meta property=\"article:published_time\" content=\"2025-08-15T07:20:22+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.wsisp.com\/helps\/wp-content\/uploads\/2025\/08\/20250815072010-689edfaa9db0a.png\" \/>\n<meta name=\"author\" content=\"admin\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"\u4f5c\u8005\" \/>\n\t<meta name=\"twitter:data1\" content=\"admin\" \/>\n\t<meta name=\"twitter:label2\" content=\"\u9884\u8ba1\u9605\u8bfb\u65f6\u95f4\" \/>\n\t<meta name=\"twitter:data2\" content=\"7 \u5206\" \/>\n<script type=\"application\/ld+json\" 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