{"id":10005996,"date":"2022-07-22T19:36:31","date_gmt":"2022-07-22T11:36:31","guid":{"rendered":"https:\/\/ityet.com\/?p=10005996"},"modified":"2022-07-22T19:36:31","modified_gmt":"2022-07-22T11:36:31","slug":"%e6%95%b0%e6%8d%ae%e5%ba%93%e4%ba%8b%e5%8a%a1%e9%9a%94%e7%a6%bb%e5%8f%91%e5%b1%95%e5%8e%86%e5%8f%b2","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10005996","title":{"rendered":"\u6570\u636e\u5e93\u4e8b\u52a1\u9694\u79bb\u53d1\u5c55\u5386\u53f2"},"content":{"rendered":"<p>\u7b80\u4ecb\uff1a\u00a0\u4e8b\u52a1\u9694\u79bb\u662f\u6570\u636e\u5e93\u7cfb\u7edf\u8bbe\u8ba1\u4e2d\u6839\u672c\u7684\u7ec4\u6210\u90e8\u5206\uff0c\u672c\u6587\u4e3b\u8981\u4ece\u6807\u51c6\u5c42\u9762\u6765\u8ba8\u8bba\u9694\u79bb\u7ea7\u522b\u7684\u53d1\u5c55\u5386\u53f2\uff0c\u9996\u5148\u660e\u786e\u9694\u79bb\u7ea7\u522b\u5212\u5206\u7684\u76ee\u6807\uff1b\u4e4b\u540e\u6982\u8ff0\u5176\u5426\u5b9a\u4e4b\u5426\u5b9a\u7684\u53d1\u5c55\u5386\u7a0b\uff1b\u8fdb\u800c\u5f15\u51fa Adya\u7ed9\u51fa\u7684\u6bd4\u8f83\u5408\u7406\u7684\u9694\u79bb\u7ea7\u522b\u5b9a\u4e49\uff0c\u6700\u7ec8\u603b\u7ed3\u9694\u79bb\u6807\u51c6\u4e00\u8def\u8d70\u6765\u7684\u601d\u8def\u3002\u4e8b\u52a1\u9694\u79bb\u662f\u6570\u636e\u5e93\u7cfb\u7edf\u8bbe\u8ba1\u4e2d\u6839\u672c\u7684\u7ec4\u6210\u90e8\u5206\uff0c\u672c\u6587\u4e3b\u8981\u4ece\u6807\u51c6\u5c42\u9762\u6765\u8ba8\u8bba\u9694\u79bb\u7ea7\u522b\u7684\u53d1\u5c55\u5386\u53f2\uff0c\u9996\u5148\u660e\u786e\u9694\u79bb\u7ea7\u522b\u5212\u5206\u7684\u76ee\u6807\uff1b\u4e4b\u540e\u6982\u8ff0\u5176\u5426\u5b9a\u4e4b\u5426\u5b9a\u7684\u53d1\u5c55\u5386\u7a0b\uff1b\u8fdb\u800c\u5f15\u51fa 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\u3002\u800c\u4e00\u4e2a\u597d\u7684\u6807\u51c6\u4e0d\u5e94\u8be5\u9650\u5236\u5176\u5b9e\u73b0\u65b9\u5f0f\u3002ANSI SQL\u6807\u51c6(1992)\uff1a\u57fa\u4e8e\u5f02\u8c611992\u5e74ANSI\u9996\u5148\u5c1d\u8bd5\u6307\u5b9a\u7edf\u4e00\u7684\u9694\u79bb\u7ea7\u522b\u6807\u51c6\uff0c\u5176\u5b9a\u4e49\u4e86\u4e0d\u540c\u7ea7\u522b\u7684\u5f02\u8c61(phenomenas)\uff0c \u5e76\u4f9d\u636e\u80fd\u907f\u514d\u591a\u5c11\u5f02\u8c61\u6765\u5212\u5206\u9694\u79bb\u6807\u51c6\u3002\u5f02\u8c61\u5305\u62ec\uff1a\u810f\u8bfb\uff08Dirty Read\uff09: \u8bfb\u5230\u4e86\u5176\u4ed6\u4e8b\u52a1\u8fd8\u672a\u63d0\u4ea4\u7684\u6570\u636e\uff1b\u4e0d\u53ef\u91cd\u590d\u8bfb\uff08Non-Repeatable\/Fuzzy Read\uff09\uff1a\u7531\u4e8e\u5176\u4ed6\u4e8b\u52a1\u7684\u4fee\u6539\u6216\u5220\u9664\uff0c\u5bf9\u67d0\u6570\u636e\u7684\u4e24\u6b21\u8bfb\u53d6\u7ed3\u679c\u4e0d\u540c\uff1b\u5e7b\u8bfb\uff08Phantom Read\uff09\uff1a\u7531\u4e8e\u5176\u4ed6\u4e8b\u52a1\u7684\u4fee\u6539\uff0c\u589e\u52a0\u6216\u5220\u9664\uff0c\u5bfc\u81f4Range\u7684\u7ed3\u679c\u5931\u6548\uff08\u5982where \u6761\u4ef6\u67e5\u8be2\uff09\u3002\u901a\u8fc7\u963b\u6b62\u4e0d\u540c\u7684\u5f02\u8c61\u53d1\u751f\uff0c\u5f97\u5230\u4e86\u56db\u79cd\u4e0d\u540c\u7ea7\u522b\u7684\u9694\u79bb\u6807\u51c6\uff1a<br \/><img decoding=\"async\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.comhttp:\/\/catkang.github.io\/assets\/img\/isolation_level\/ansi_def.png\" alt=\"\u56fe\u7247\" title=\"\u56fe\u7247\" loading=\"lazy\" ><br \/>\u00a0ANSI SQL\u6807\u51c6\u770b\u8d77\u6765\u662f\u975e\u5e38\u76f4\u89c2\u7684\u5212\u5206\u65b9\u5f0f\uff0c\u4e0d\u60f3\u8981\u4ec0\u4e48\u5c31\u6392\u9664\u4ec0\u4e48\uff0c\u5e76\u4e14\u505a\u5230\u4e86\u5b9e\u73b0\u65e0\u5173\u3002\u7136\u800c\uff0c\u73b0\u5b9e\u5e76\u4e0d\u50cf\u60f3\u8c61\u7f8e\u597d\u3002\u56e0\u4e3a\u5b83\u5e76\u4e0d\u6b63\u786e\u3002A Critique of ANSI(1995)\uff1a\u57fa\u4e8e\u9501\u51e0\u5e74\u540e\uff0c\u5fae\u8f6f\u7684\u7814\u7a76\u5458\u4eec\u5728A Critique of ANSI SQL Isolation Levels\u4e00\u6587\u4e2d\u5bf9ANSI\u7684\u6807\u51c6\u8fdb\u884c\u4e86\u6279\u5224\uff0c\u6307\u51fa\u5176\u5b58\u5728\u4e24\u4e2a\u81f4\u547d\u7684\u95ee\u9898\uff1a1\uff0c\u4e0d\u5b8c\u6574\uff0c\u7f3a\u5c11\u5bf9Dirty Write\u7684\u6392\u9664ANSI SQL\u6807\u51c6\u4e2d\u6240\u6709\u7684\u9694\u79bb\u7ea7\u522b\u90fd\u6ca1\u6709\u5c06Dirty Write\u8fd9\u79cd\u5f02\u8c61\u6392\u9664\u5728\u5916\uff0c\u6240\u8c13Dirty Write\u6307\u7684\u662f\u4e24\u4e2a\u672a\u63d0\u4ea4\u7684\u4e8b\u52a1\u5148\u540e\u5bf9\u540c\u4e00\u4e2a\u5bf9\u8c61\u8fdb\u884c\u4e86\u4fee\u6539\u3002\u800cDirty Write\u4e4b\u6240\u4ee5\u662f\u4e00\u79cd\u5f02\u8c61\uff0c\u4e3b\u8981\u56e0\u4e3a\u4ed6\u4f1a\u5bfc\u81f4\u4e0b\u9762\u7684\u4e00\u81f4\u6027\u95ee\u9898\uff1aH0: w1[x] w2[x] w2[y] c2 w1[y] c1\u8fd9\u6bb5\u5386\u53f2\u4e2d\uff0c\u5047\u8bbe\u6709\u76f8\u5173\u6027\u7ea6\u675fx=y\uff0cT1\u5c1d\u8bd5\u5c06\u4e8c\u8005\u90fd\u4fee\u6539\u4e3a1\uff0cT2\u5c1d\u8bd5\u5c06\u4e8c\u8005\u90fd\u4fee\u6539\u4e3a2\uff0c\u987a\u5e8f\u6267\u884c\u7684\u7ed3\u679c\u5e94\u8be5\u662f\u4e8c\u8005\u90fd\u4e3a1\u6216\u8005\u90fd\u4e3a2\uff0c\u4f46\u7531\u4e8eDirty Write\u7684\u53d1\u751f\uff0c\u6700\u7ec8\u7ed3\u679c\u53d8\u4e3ax=2\uff0cy=1\uff0c\u4e0d\u4e00\u81f4\u30022\uff0c\u6b67\u4e49ANSI SQL\u7684\u82f1\u6587\u8868\u8ff0\u6709\u6b67\u4e49\u3002\u4ee5Phantom\u4e3a\u4f8b\uff0c\u5982\u4e0b\u56fe\u5386\u53f2H3\uff1aH3\uff1ar1[P] w2[insert y to P] r2[z] w2[z] c2 r1[z] c1\u5047\u8bbeT1\u6839\u636e\u6761\u4ef6P\u67e5\u8be2\u6240\u6709\u7684\u96c7\u5458\u5217\u8868\uff0c\u4e4b\u540eT2\u589e\u52a0\u4e86\u4e00\u4e2a\u96c7\u5458\u5e76\u589e\u52a0\u4e86\u96c7\u5458\u4eba\u6570\u503cz\uff0c\u4e4b\u540eT1\u8bfb\u53d6\u96c7\u5458\u4eba\u6570z\uff0c\u6700\u7ec8T1\u7684\u5217\u8868\u4e2d\u7684\u4eba\u6570\u6bd4z\u5c11\uff0c\u4e0d\u4e00\u81f4\u3002\u4f46T1\u5e76\u6ca1\u6709\u5728T2\u4fee\u6539\u94fe\u8868\u540e\u518d\u4f7f\u7528P\u4e2d\u7684\u503c\uff0c\u662f\u5426\u5c31\u4e0d\u5c5e\u4e8eANSI\u4e2d\u5bf9Phantom\u7684\u5b9a\u4e49\u4e86\u5462\uff1f\u8fd9\u4e5f\u5bfc\u81f4\u4e86\u5bf9ANSI\u7684\u8868\u8ff0\u53ef\u80fd\u6709\u4e25\u683c\u548c\u5bbd\u677e\u4e24\u79cd\u89e3\u8bfb\u3002\u5bf9\u4e8eRead Dirty\u548cNon-Repeatable\/Fuzzy Read\u4e5f\u6709\u540c\u6837\u7684\u95ee\u9898\u3002\u90a3\u4e48\uff0c\u5982\u4f55\u89e3\u51b3\u4e0a\u8ff0\u4e24\u4e2a\u95ee\u9898\u5462\uff1fCritique of ANSI\u7684\u7b54\u6848\u662f\uff1a\u5b81\u53ef\u9519\u6740\u4e09\u5343\uff0c\u4e0d\u53ef\u653e\u8fc7\u4e00\u4e2a\uff0c\u5373\u7ed9ANSI\u6807\u51c6\u4e2d\u7684\u5f02\u8c61\u6700\u4e25\u683c\u7684\u5b9a\u4e49\u3002Critique of ANSI\u6539\u9020\u4e86\u5f02\u8c61\u7684\u5b9a\u4e49\uff1aP0: w1[x]\u2026w2[x]\u2026(c1 or a1) (Dirty Write)P1: w1[x]\u2026r2[x]\u2026(c1 or a1) (Dirty Read)P2: r1[x]\u2026w2[x]\u2026(c1 or a1) (Fuzzy or Non-Repeatable Read)P3: r1[P]\u2026w2[y in P]\u2026(c1 or a1) (Phantom)\u6b64\u65f6\u5b9a\u4e49\u5df2\u7ecf\u5f88\u4e25\u683c\u4e86\uff0c\u76f4\u63a5\u963b\u6b62\u4e86\u5bf9\u5e94\u7684\u8bfb\u5199\u7ec4\u5408\u987a\u5e8f\u3002\u4ed4\u7ec6\u53ef\u4ee5\u770b\u51fa\uff0c\u6b64\u65f6\u5f97\u5230\u7684\u5176\u5b9e\u5c31\u662f\u57fa\u4e8e\u9501\u7684\u5b9a\u4e49:Read Uncommitted\uff0c\u963b\u6b62P0\uff1a\u6574\u4e2a\u4e8b\u52a1\u9636\u6bb5\u5bf9x\u52a0\u957f\u5199\u9501Read Commited\uff0c\u963b\u6b62P0\uff0cP1\uff1a\u77ed\u8bfb\u9501 + \u957f\u5199\u9501Repeatable Read\uff0c\u963b\u6b62P0\uff0cP1\uff0cP2\uff1a\u957f\u8bfb\u9501 + \u77ed\u8c13\u8bcd\u9501 + \u957f\u5199\u9501Serializable\uff0c\u963b\u6b62P0\uff0cP1\uff0cP2\uff0cP3\uff1a\u957f\u8bfb\u9501 + \u957f\u8c13\u8bcd\u9501 + \u957f\u5199\u9501\u95ee\u9898\u672c\u8d28\u53ef\u4ee5\u770b\u51fa\uff0c\u8fd9\u79cd\u65b9\u5f0f\u7684\u9694\u79bb\u6027\u5b9a\u4e49\u4fdd\u8bc1\u4e86\u6b63\u786e\u6027\uff0c\u4f46\u5374\u4ea7\u751f\u4e86\u4f9d\u8d56\u5b9e\u73b0\u65b9\u5f0f\u7684\u95ee\u9898\uff1a\u592a\u8fc7\u4e25\u683c\u7684\u9694\u79bb\u6027\u5b9a\u4e49\uff0c\u963b\u6b62\u4e86Optimize\u6216Multi-version\u7684\u5b9e\u73b0\u65b9\u5f0f\u4e2d\u7684\u4e00\u4e9b\u6b63\u5e38\u7684\u60c5\u51b5\uff1a\u9488\u5bf9P0\uff1aOptimize\u7684\u5b9e\u73b0\u65b9\u5f0f\u53ef\u80fd\u4f1a\u8ba9\u591a\u4e2a\u4e8b\u52a1\u5404\u81ea\u5199\u81ea\u5df1\u7684\u672c\u5730\u526f\u672c\uff0c\u63d0\u4ea4\u7684\u65f6\u5019\u53ea\u8981\u987a\u5e8f\u5408\u9002\u662f\u53ef\u4ee5\u6210\u529f\u7684\uff0c\u53ea\u5728\u9700\u8981\u7684\u65f6\u5019\u624dabort\uff0c\u4f46\u8fd9\u79cd\u9009\u62e9\u88abP0\u963b\u6b62\uff1b\u9488\u5bf9P2\uff1a\u53ea\u8981T1\u6ca1\u6709\u5728\u8bfbx\uff0c\u540e\u7eed\u6ca1\u6709\u4e0ex\u76f8\u5173\u7684\u64cd\u4f5c\uff0c\u4e14\u5148\u4e8eT2\u63d0\u4ea4\u3002\u5728Optimize\u7684\u5b9e\u73b0\u4e2d\u662f\u53ef\u4ee5\u63a5\u53d7\u7684\uff0c\u5374\u88abP2\u963b\u6b62\u3002\u56de\u5fc6Critique of ANSI\u4e2d\u6307\u51fa\u7684ANSI\u6807\u51c6\u95ee\u9898\uff0c\u5305\u62ecDirty Write\u548c\u6b67\u4e49\uff0c\u5176\u5b9e\u90fd\u662f\u7531\u4e8e\u591aObject\u4e4b\u95f4\u6709\u76f8\u4e92\u7ea6\u675f\u5173\u7cfb\u5bfc\u81f4\u7684\uff0c\u5982\u4e0b\u56fe\u6240\u793a\uff0c\u56fe\u4e2d\u9ed1\u8272\u90e8\u5206\u8868\u793a\u7684\u662fANSI\u4e2d\u9488\u5bf9\u67d0\u4e00\u4e2a\u5f02\u8c61\u63cf\u8ff0\u7684\u5f02\u5e38\u60c5\u51b5\uff0c\u7070\u8272\u90e8\u5206\u7531\u4e8e\u591aObject\u7ea6\u675f\u5bfc\u81f4\u7684\u5f02\u5e38\u90e8\u5206\uff0c\u4f46\u8fd9\u90e8\u5206\u5728\u4f20\u7edf\u7684\u5f02\u8c61\u5b9a\u4e49\u65b9\u5f0f\u4e2d\u5e76\u4e0d\u80fd\u63cf\u8ff0\uff0c\u56e0\u6b64\u5176\u53ea\u80fd\u9000\u800c\u6c42\u5176\u6b21\uff0c\u6269\u5927\u9650\u5236\u7684\u8303\u56f4\u5230\u9ec4\u8272\u90e8\u5206\uff0c\u4ece\u800c\u9650\u5236\u4e86\u6b63\u5e38\u7684\u60c5\u51b5\u3002\uff1a<br \/><img decoding=\"async\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.comhttp:\/\/catkang.github.io\/assets\/img\/isolation_level\/Isolation_cover.png\" alt=\"\u56fe\u7247\" title=\"\u56fe\u7247\" loading=\"lazy\" ><br \/>\u7531\u6b64\uff0c\u53ef\u4ee5\u770b\u51fa\u95ee\u9898\u7684\u672c\u8d28\uff1a\u7531\u4e8e\u5f02\u8c61\u7684\u63cf\u8ff0\u53ea\u9488\u5bf9\u5355\u4e2aobject\uff0c\u7f3a\u5c11\u63cf\u8ff0\u591aobject\u4e4b\u95f4\u7684\u7ea6\u675f\u5173\u7cfb\uff0c\u5bfc\u81f4\u9700\u8981\u7528\u9501\u7684\u65b9\u5f0f\u6765\u4f5c\u51fa\u8d85\u51fa\u5fc5\u987b\u7684\u9650\u5236\u3002\u76f8\u5e94\u5730\uff0c\u89e3\u51b3\u95ee\u9898\u7684\u5173\u952e\uff1a\u8981\u6709\u65b0\u7684\u5b9a\u4e49\u5f02\u8c61\u7684\u6a21\u578b\uff0c\u4f7f\u4e4b\u80fd\u7cbe\u51c6\u7684\u63cf\u8ff0\u591aobject\u4e4b\u95f4\u7684\u7ea6\u675f\u5173\u7cfb\uff0c\u4ece\u800c\u4f7f\u5f97\u6211\u4eec\u80fd\u591f\u7cbe\u51c6\u5730\u9650\u5236\u4e0a\u8ff0\u7070\u8272\u90e8\u5206\uff0c\u800c\u5c06\u9ec4\u8272\u7684\u90e8\u5206\u89e3\u653e\u51fa\u6765\u3002Adya\u7ed9\u51fa\u7684\u7b54\u6848\u662f\u5e8f\u5217\u5316\u56fe\u3002A Generalized Theory(1999)\uff1a\u57fa\u4e8e\u5e8f\u5217\u5316\u56feAdya\u5728Weak Consistency: A Generalized Theory and Optimistic Implementations for Distributed Transactions\u4e2d\u7ed9\u51fa\u4e86\u57fa\u4e8e\u5e8f\u5217\u5316\u56fe\u5f97\u5b9a\u4e49\uff0c\u601d\u8def\u4e3a\u5148\u5b9a\u4e49\u51b2\u7a81\u5173\u7cfb\uff1b\u5e76\u4ee5\u51b2\u7a81\u5173\u7cfb\u4e3a\u6709\u5411\u8fb9\u5f62\u6210\u5e8f\u5217\u5316\u56fe\uff1b\u518d\u4ee5\u56fe\u4e2d\u7684\u73af\u7c7b\u578b\u5b9a\u4e49\u4e0d\u540c\u7684\u5f02\u8c61\uff1b\u6700\u540e\u901a\u8fc7\u963b\u6b62\u4e0d\u540c\u7684\u5f02\u8c61\u6765\u5b9a\u4e49\u9694\u79bb\u7ea7\u522b\u3002\u5e8f\u5217\u5316\u56fe\uff08Direct Serialization Graph, DSG\uff09\u5e8f\u5217\u5316\u56fe\u662f\u7528\u6709\u5411\u56fe\u7684\u65b9\u5f0f\u6765\u8868\u793a\u4e8b\u52a1\u76f8\u4e92\u4e4b\u95f4\u7684\u4f9d\u8d56\u5173\u7cfb\uff0c\u56fe\u4e2d\u6bcf\u4e2a\u8282\u70b9\u8868\u793a\u4e00\u4e2a\u4e8b\u52a1\uff0c\u6709\u5411\u8fb9\u8868\u793a\u5b58\u5728\u4e00\u79cd\u4f9d\u8d56\u5173\u7cfb\uff0c\u4e8b\u52a1\u9700\u8981\u7b49\u5230\u6240\u6709\u6307\u5411\u5176\u7684\u4e8b\u52a1\u5148\u884c\u63d0\u4ea4\uff0c\u5982\u4e0b\u56fe\u6240\u793a\u5386\u53f2\u7684\u5408\u6cd5\u7684\u63d0\u4ea4\u987a\u5e8f\u5e94\u8be5\u4e3a\uff1aT1\uff0cT2\uff0cT3\uff1a<br \/><img decoding=\"async\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.comhttp:\/\/catkang.github.io\/assets\/img\/isolation_level\/andy_dsg.png\" alt=\"\u56fe\u7247\" title=\"\u56fe\u7247\" loading=\"lazy\" ><br \/>\u8fd9\u91cc\u7684\u6709\u5411\u8fb9\u5305\u62ec\u4e09\u79cd\u60c5\u51b5\uff1a\u5199\u5199\u51b2\u7a81ww\uff08Directly Write-Depends\uff09\uff1a\u8868\u793a\u4e24\u4e2a\u4e8b\u52a1\u5148\u540e\u4fee\u6539\u540c\u4e00\u4e2a\u6570\u636e\u5e93Object(w1[x]\u2026w2[x]&#8230;)\uff1b\u5148\u5199\u540e\u8bfb\u51b2\u7a81wr\uff08Directly Read-Depends\uff09\uff1a\u4e00\u4e2a\u4e8b\u52a1\u4fee\u6539\u67d0\u4e2a\u6570\u636e\u5e93Object\u540e\uff0c\u53e6\u4e00\u4e2a\u5bf9\u8be5Object\u8fdb\u884c\u8bfb\u64cd\u4f5c\uff08w1[x]\u2026r2[x]&#8230;\uff09\uff1b\u5148\u8bfb\u540e\u5199\u51b2\u7a81rw\uff08Directly Anti-Depends\uff09\uff1a\u4e00\u4e2a\u4e8b\u52a1\u8bfb\u53d6\u67d0\u4e2aObject\u6216\u8005\u67d0\u4e2aRange\u540e\uff0c\u53e6\u4e00\u4e2a\u4e8b\u52a1\u8fdb\u884c\u4e86\u4fee\u6539\uff08r1[x]\u2026w2[x]\u2026 or r1[P]\u2026w2[y in P]\uff09\uff1b<br \/><img decoding=\"async\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.comhttp:\/\/catkang.github.io\/assets\/img\/isolation_level\/andy_dsg_edge.png\" alt=\"\u56fe\u7247\" title=\"\u56fe\u7247\" loading=\"lazy\" ><br \/>\u57fa\u4e8e\u5e8f\u5217\u5316\u56fe\u7684\u5f02\u8c61\u5b9a\u4e49\uff1a\u6839\u636e\u6709\u5411\u56fe\u7684\u5b9a\u4e49\uff0c\u6211\u4eec\u53ef\u4ee5\u5c06\u4e8b\u52a1\u5bf9\u4e0d\u540cObject\u7684\u4f9d\u8d56\u5173\u7cfb\u8868\u793a\u5230\u4e00\u5f20\u540c\u4e00\u5f20\u56fe\u4e2d\uff0c\u800c\u6240\u8c13\u5f02\u8c61\u5c31\u662f\u5728\u56fe\u4e2d\u627e\u4e0d\u5230\u4e00\u4e2a\u6b63\u786e\u7684\u5e8f\u5217\u5316\u987a\u5e8f\uff0c\u5373\u5b58\u5728\u67d0\u79cd\u73af\u3002\u800c\u8fd9\u79cd\u57fa\u4e8e\u73af\u7684\u5b9a\u4e49\u5176\u5b9e\u5c31\u662f\u5c06\u57fa\u4e8eLock\u5b9a\u4e49\u7684\u5f02\u8c61\u6700\u5c0f\u5316\u5230\u56fe\u4e2d\u7070\u8272\u90e8\u5206\uff1a1\uff0cP0(Dirty Write) \u6700\u5c0f\u5316\u4e3a G0(Write Cycles)\uff1a\u5e8f\u5217\u5316\u56fe\u4e2d\u5305\u542b\u4e24\u6761\u8fb9\u90fd\u4e3aww\u51b2\u7a81\u7ec4\u6210\u7684\u73af\uff0c\u5982H0\uff1aH0: w1[x] w2[x] w2[y] c2 w1[y] c1\u53ef\u4ee5\u770b\u51faT1\u5728x\u4e0a\u4e0eT2\u5199\u5199\u51b2\u7a81\uff0cT2\u53c8\u5728y\u4e0a\u4e0eT1\u5199\u5199\u51b2\u7a81\uff0c\u5f62\u6210\u4e86\u5982\u4e0b\u56fe\u6240\u793a\u7684\u73af\u3002<br \/><img decoding=\"async\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.comhttp:\/\/catkang.github.io\/assets\/img\/isolation_level\/ww_cycle.png\" alt=\"\u56fe\u7247\" title=\"\u56fe\u7247\" loading=\"lazy\" ><br \/>2\uff0cP1(Dirty Read) \u6700\u5c0f\u5316\u4e3a G1\uff1aDirty Read\u5f02\u8c61\u7684\u6700\u5c0f\u96c6\u5305\u62ec\u4e09\u4e2a\u90e8\u5206G1a(Aborted Reads)\uff0c\u8bfb\u5230\u7684uncommitted\u6570\u636e\u6700\u7ec8\u88ababort\uff1bG1b(Intermediate Reads) \uff1a\u8bfb\u5230\u5176\u4ed6\u4e8b\u52a1\u4e2d\u95f4\u7248\u672c\u7684\u6570\u636e\uff1b\u4ee5\u53caG1c(Circular Information Flow)\uff1aDSG\u4e2d\u5305\u542bww\u51b2\u7a81\u548cwr\u51b2\u7a81\u5f62\u6210\u7684\u73af\u30023\uff0cP2(Fuzzy or Non-Repeatable Read) \u6700\u5c0f\u5316\u4e3a G2-item(Item Anti-dependency Cycles)\u00a0\uff1aDSG\u4e2d\u5305\u542b\u73af\uff0c\u4e14\u5176\u4e2d\u81f3\u5c11\u6709\u4e00\u6761\u5173\u4e8e\u67d0\u4e2aobject\u7684rw\u51b2\u7a814\uff0cP3(Phantom) \u6700\u5c0f\u5316\u4e3a G2(Anti-dependency Cycles):\u00a0DSG\u4e2d\u5305\u542b\u73af\uff0c\u5e76\u4e14\u5176\u4e2d\u81f3\u5c11\u6709\u4e00\u6761\u662frw\u51b2\u7a81\uff0c\u4ecd\u7136\u4ee5\u4e0a\u9762\u7684H3\u4e3a\u4f8b\uff1aH3\uff1ar1[P] w2[insert y to P] r2[z] w2[z] c2 r1[z] c1T1\u5728\u8c13\u8bcdP\u4e0a\u4e0eT2 rw\u51b2\u7a81\uff0c\u53cd\u8fc7\u6765T2\u53c8\u5728z\u4e0a\u4e0eT1wr\u51b2\u7a81\uff0c\u5982\u4e0b\u56fe\u6240\u793a\uff1a<br \/><img decoding=\"async\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.comhttp:\/\/catkang.github.io\/assets\/img\/isolation_level\/anti_dependency_cycles.png\" alt=\"\u56fe\u7247\" title=\"\u56fe\u7247\" loading=\"lazy\" ><br \/>\u5bf9\u5e94\u7684\u9694\u79bb\u7ea7\u522b\uff1a\u901a\u8fc7\u4e0a\u9762\u7684\u8ba8\u8bba\u53ef\u4ee5\u770b\u51fa\uff0c\u901a\u8fc7\u73af\u7684\u65b9\u5f0f\u6211\u4eec\u6210\u529f\u6700\u5c0f\u5316\u4e86\u5f02\u8c61\u7684\u9650\u5236\u8303\u56f4\uff0c\u90a3\u4e48\u6392\u9664\u8fd9\u4e9b\u5f02\u8c61\u5c31\u5f97\u5230\u4e86\u66f4\u5bbd\u677e\u7684\uff0c\u901a\u7528\u7684\u9694\u79bb\u7ea7\u522b\u5b9a\u4e49\uff1aPL-1\uff08Read Uncommitted\uff09\uff1a\u963b\u6b62G0PL-2\uff08Read Commited\uff09\uff1a\u963b\u6b62G1PL-2.99\uff08Repeatable Read\uff09\uff1a\u963b\u6b62G1\uff0cG2-itemPL-3\uff08Serializable\uff09\uff1a\u963b\u6b62G1\uff0cG2\u5176\u4ed6\u9694\u79bb\u7ea7\u522b\uff1a\u9664\u4e86\u4e0a\u8ff0\u7684\u9694\u79bb\u7ea7\u522b\u5916\uff0c\u5728\u6b63\u786e\u6027\u7684\u9891\u8c31\u4e2d\u8fd8\u6709\u7740\u5927\u91cf\u7a7a\u767d\uff0c\u4e5f\u5c31\u5b58\u5728\u7740\u5404\u79cd\u5176\u4ed6\u9694\u79bb\u7ea7\u522b\u7684\u7a7a\u95f4\uff0c\u5546\u4e1a\u6570\u636e\u5e93\u7684\u5b9e\u73b0\u4e2d\u6709\u4e24\u4e2a\u6bd4\u8f83\u5e38\u89c1\uff1a1\uff0cCursor Stability\u8be5\u9694\u79bb\u754c\u522b\u4ecb\u4e8eRead Committed\u548cRepeatable Read\u4e4b\u95f4\uff0c\u901a\u8fc7\u5bf9\u6e38\u6807\u52a0\u9501\u800c\u4e0d\u662f\u5bf9object\u52a0\u8bfb\u9501\u7684\u65b9\u5f0f\u907f\u514d\u4e86Lost Write\u5f02\u8c61\u30022\uff0c Snapshot Ioslation\u4e8b\u52a1\u5f00\u59cb\u7684\u65f6\u5019\u62ff\u4e00\u4e2aStart-Timestamp\u7684snapshot\uff0c\u6240\u6709\u7684\u64cd\u4f5c\u90fd\u5728\u8fd9\u4e2asnapshot\u4e0a\u505a\uff0c\u5f53commit\u7684\u65f6\u5019\u62ffCommit-Timestamp\uff0c\u68c0\u67e5\u6240\u6709\u6709\u51b2\u7a81\u7684\u503c\u4e0d\u80fd\u518d[Start- Timestamp, Commit-Timestamp]\u88ab\u63d0\u4ea4\uff0c\u5426\u5219abort\u3002\u957f\u4e45\u4ee5\u6765\uff0cSnapshot Ioslation\u4e00\u76f4\u88ab\u8ba4\u4e3a\u662fSerializable\uff0c\u4f46\u5176\u5b9eSnapshot Ioslation\u4e0b\u8fd8\u4f1a\u51fa\u73b0Write Skew\u7684\u5f02\u8c61\u3002\u4e4b\u540e\u7684\u6587\u7ae0\u4f1a\u8be6\u7ec6\u4ecb\u7ecd\u5982\u4f55\u4eceSnapshot Ioslation\u51fa\u53d1\u83b7\u5f97Serializable\u3002\u603b\u7ed3\u5bf9\u4e8e\u4e8b\u52a1\u9694\u79bb\u7ea7\u522b\u7684\u6807\u51c6\uff0c\u6570\u636e\u5e93\u7684\u524d\u8f88\u4eec\u8fdb\u884c\u4e86\u957f\u4e45\u7684\u63a2\u7d22\uff1aANSI isolation levels\u5b9a\u4e49\u4e86\u5f02\u8c61\u6807\u51c6\uff0c\u5e76\u6839\u636e\u6240\u6392\u9664\u7684\u5f02\u8c61\uff0c\u5b9a\u4e49\u4e86\uff0cRead Uncommitted\u3001Read Committed\u3001Repeatable Read\u3001Serializable\u56db\u4e2a\u9694\u79bb\u7ea7\u522b\uff1bA Critique of ANSI SQL Isolation Levels\u8ba4\u4e3aANSI\u7684\u5b9a\u4e49\u5e76\u6ca1\u5c06\u6709\u591aobject\u7ea6\u675f\u7684\u5f02\u8c61\u6392\u9664\u5728\u5916\uff0c\u5e76\u9009\u62e9\u7528\u66f4\u4e25\u683c\u7684\u57fa\u4e8eLock\u7684\u5b9a\u4e49\u6269\u5927\u4e86\u6bcf\u4e2a\u7ea7\u522b\u9650\u5236\u7684\u8303\u56f4\uff1bWeak Consistency: A Generalized Theory and Optimistic Implementations for Distributed Transactions\u8ba4\u4e3a\u57fa\u4e8eLock\u7684\u5b9a\u4e49\u8fc7\u591a\u7684\u6269\u5927\u4e86\u9650\u5236\u7684\u8303\u56f4\uff0c\u5bfc\u81f4\u6b63\u5e38\u60c5\u51b5\u88ab\u6392\u9664\u5728\u5916\uff0c\u4ece\u800c\u9650\u5236\u4e86Optimize\u7c7b\u578b\u5e76\u884c\u63a7\u5236\u7684\u4f7f\u7528\uff1b\u6307\u51fa\u89e3\u51b3\u8be5\u95ee\u9898\u7684\u5173\u952e\u662f\u8981\u6709\u6a21\u578b\u80fd\u51c6\u786e\u5730\u63cf\u8ff0\u8fd9\u79cd\u591aObject\u7ea6\u675f\uff1b\u5e76\u7ed9\u51fa\u4e86\u57fa\u4e8e\u5e8f\u5217\u5316\u56fe\u7684\u5b9a\u4e49\u65b9\u5f0f\uff0c\u5c06\u6bcf\u4e2a\u7ea7\u522b\u9650\u5236\u7684\u8303\u56f4\u6700\u5c0f\u5316\u3002\u53c2\u8003A History of Transaction HistoriesANSI isolation levelsA Critique of ANSI SQL Isolation LevelsWeak Consistency: A Generalized Theory and Optimistic Implementations for Distributed TransactionsGeneralized Isolation Level Definitions\u539f\u6587\u94fe\u63a5\uff1a<a href=\"https:\/\/link.segmentfault.com\/?enc=hHgZq%2FgrlBClPFwMwqJv8A%3D%3D.Qb3Cww6hbE7m49RNxiRX0TfnuY1z941ypVFDWFZHxIZlmNniJlnVc2uhgMoERGc2\" rel=\"nofollow\">http:\/\/click.aliyun.com\/m\/100&#8230;<\/a>\u672c\u6587\u4e3a\u963f\u91cc\u4e91\u539f\u521b\u5185\u5bb9\uff0c\u672a\u7ecf\u5141\u8bb8\u4e0d\u5f97\u8f6c\u8f7d\u3002<\/p>\n<p><a href=\"https:\/\/segmentfault.com\/a\/1190000042210016\">https:\/\/segmentfault.com\/a\/1190000042210016<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u7b80\u4ecb\uff1a\u00a0\u4e8b\u52a1\u9694\u79bb\u662f\u6570\u636e\u5e93\u7cfb\u7edf\u8bbe\u8ba1\u4e2d\u6839\u672c\u7684\u7ec4\u6210\u90e8\u5206\uff0c\u672c\u6587\u4e3b\u8981\u4ece\u6807\u51c6\u5c42\u9762\u6765\u8ba8\u8bba\u9694\u79bb\u7ea7\u522b\u7684\u53d1\u5c55\u5386\u53f2\uff0c\u9996\u5148\u660e\u786e\u9694\u79bb\u7ea7\u522b [&hellip;]<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[],"tags":[],"class_list":["post-10005996","post","type-post","status-publish","format-standard","hentry"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10005996","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=10005996"}],"version-history":[{"count":0,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10005996\/revisions"}],"wp:attachment":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10005996"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10005996"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10005996"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}