{"id":10006575,"date":"2022-09-22T19:43:36","date_gmt":"2022-09-22T11:43:36","guid":{"rendered":"https:\/\/ityet.com\/?p=10006575"},"modified":"2022-09-22T19:43:36","modified_gmt":"2022-09-22T11:43:36","slug":"mysql-ddl%e6%89%a7%e8%a1%8c%e6%96%b9%e5%bc%8f-online-ddl%e4%bb%8b%e7%bb%8d","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10006575","title":{"rendered":"MySQL DDL\u6267\u884c\u65b9\u5f0f-Online DDL\u4ecb\u7ecd"},"content":{"rendered":"<h3>1 \u5f15\u8a00<\/h3>\n<p>\u5927\u5bb6\u597d\uff0c\u4eca\u5929\u4e0e\u5927\u5bb6\u4e00\u8d77\u5206\u4eab\u4e00\u4e0b mysql DDL\u6267\u884c\u65b9\u5f0f\u3002<\/p>\n<p>\u4e00\u822c\u6765\u8bf4MySQL\u5206\u4e3aDDL\uff08\u5b9a\u4e49\uff09\u548cDML\uff08\u64cd\u4f5c\uff09\u3002<\/p>\n<ul>\n<li>DDL\uff1aData Definition Language\uff0c\u5373\u6570\u636e\u5b9a\u4e49\u8bed\u8a00\uff0c\u90a3\u76f8\u5173\u7684\u5b9a\u4e49\u64cd\u4f5c\u5c31\u662fDDL\uff0c\u5305\u62ec\uff1a\u65b0\u5efa\u3001\u4fee\u6539\u3001\u5220\u9664\u7b49\uff1b\u76f8\u5173\u7684\u547d\u4ee4\u6709\uff1aCREATE\uff0cALTER\uff0cDROP\uff0cTRUNCATE\u622a\u65ad\u8868\u5185\u5bb9\uff08\u5f00\u53d1\u671f\uff0c\u8fd8\u662f\u633a\u5e38\u7528\u7684\uff09\uff0cCOMMENT \u4e3a\u6570\u636e\u5b57\u5178\u6dfb\u52a0\u5907\u6ce8\u3002<\/li>\n<li>DML\uff1aData Manipulation Language\uff0c\u5373\u6570\u636e\u64cd\u4f5c\u8bed\u8a00\uff0c\u5373\u5904\u7406\u6570\u636e\u5e93\u4e2d\u6570\u636e\u7684\u64cd\u4f5c\u5c31\u662fDML\uff0c\u5305\u62ec\uff1a\u9009\u53d6\uff0c\u63d2\u5165\uff0c\u66f4\u65b0\uff0c\u5220\u9664\u7b49\uff1b\u76f8\u5173\u7684\u547d\u4ee4\u6709\uff1aSELECT,INSERT,UPDATE,DELETE\uff0c\u8fd8\u6709 LOCK TABLE\uff0c\u4ee5\u53ca\u4e0d\u5e38\u7528\u7684CALL \u2013 \u8c03\u7528\u4e00\u4e2aPL\/SQL\u6216Java\u5b50\u7a0b\u5e8f\uff0cEXPLAIN PLAN \u2013 \u89e3\u6790\u5206\u6790\u6570\u636e\u8bbf\u95ee\u8def\u5f84\u3002<\/li>\n<\/ul>\n<p>\u6211\u4eec\u53ef\u4ee5\u8ba4\u4e3a\uff1a<\/p>\n<ul>\n<li>CREATE\uff0cALTER \uff0cDROP\uff0cTRUNCATE\uff0c\u5b9a\u4e49\u76f8\u5173\u7684\u547d\u4ee4\u5c31\u662fDDL;<\/li>\n<li>SELECT\uff0cINSERT\uff0cUPDATE\uff0cDELETE\uff0c\u64cd\u4f5c\u5904\u7406\u6570\u636e\u7684\u547d\u4ee4\u5c31\u662fDML\uff1b<\/li>\n<\/ul>\n<p>DDL\u3001DML\u533a\u522b\uff1a<\/p>\n<ul>\n<li>DML\u64cd\u4f5c\u662f\u53ef\u4ee5\u624b\u52a8\u63a7\u5236\u4e8b\u52a1\u7684\u5f00\u542f\u3001\u63d0\u4ea4\u548c\u56de\u6eda\u7684\u3002<\/li>\n<li>DDL\u64cd\u4f5c\u662f\u9690\u6027\u63d0\u4ea4\u7684\uff0c\u4e0d\u80fdrollback\uff0c\u4e00\u5b9a\u8981\u8c28\u614e\u54e6\uff01<\/li>\n<\/ul>\n<p>\u65e5\u5e38\u5f00\u53d1\u6211\u4eec\u5bf9\u4e00\u6761DML\u8bed\u53e5\u8f83\u4e3a\u719f\u6089\uff0c\u5f88\u591a\u5f00\u53d1\u4eba\u5458\u90fd\u4e86\u89e3sql\u7684\u6267\u884c\u8fc7\u7a0b\uff0c\u6bd4\u8f83\u719f\u6089\uff0c\u4f46\u662fDDL\u662f\u5982\u4f55\u6267\u884c\u7684\u5462\uff0c\u5927\u90e8\u5206\u5f00\u53d1\u4eba\u5458\u53ef\u80fd\u4e0d\u592a\u5173\u5fc3\uff0c\u4e5f\u8ba4\u4e3a\u6ca1\u5fc5\u8981\u4e86\u89e3\uff0c\u90fd\u4ea4\u7ed9DBA\u5427\u3002 \u5176\u5b9e\u4e0d\u7136\uff0c\u4e86\u89e3\u4e00\u4e9b\u80fd\u5c3d\u91cf\u907f\u5f00\u4e00\u4e9bddl\u7684\u5751\uff0c\u90a3\u4e48\u4e0b\u9762\u5e26\u5927\u5bb6\u4e00\u8d77\u4e86\u89e3\u4e00\u4e0bDDL\u6267\u884c\u7684\u65b9\u5f0f\uff0c\u4e5f\u7b97\u629b\u7816\u5f15\u7389\u5427\u3002\u5982\u6709\u9519\u8bef\uff0c\u8fd8\u8bf7\u5404\u4f4d\u5927\u4f6c\u4eec\u6307\u6b63\u3002<\/p>\n<h3>2 \u6982\u8ff0<\/h3>\n<p>\u5728MySQL\u4f7f\u7528\u8fc7\u7a0b\u4e2d\uff0c\u6839\u636e\u4e1a\u52a1\u7684\u9700\u6c42\u5bf9\u8868\u7ed3\u6784\u8fdb\u884c\u53d8\u66f4\u662f\u4e2a\u666e\u904d\u7684\u8fd0\u7ef4\u64cd\u4f5c\uff0c\u8fd9\u4e9b\u79f0\u4e3aDDL\u64cd\u4f5c\u3002\u5e38\u89c1\u7684DDL\u64cd\u4f5c\u6709\u5728\u8868\u4e0a\u589e\u52a0\u65b0\u5217\u6216\u7ed9\u67d0\u4e2a\u5217\u6dfb\u52a0\u7d22\u5f15\u3002<\/p>\n<p>\u6211\u4eec\u5e38\u7528\u7684\u6613\u7ef4\u5e73\u53f0\u63d0\u4f9b\u4e86\u4e24\u79cd\u65b9\u5f0f\u53ef\u6267\u884cDDL\uff0c\u5305\u62ecMySQL\u539f\u751f\u5728\u7ebfDDL\uff08online DDL\uff09\u4ee5\u53ca\u4e00\u79cd\u7b2c\u4e09\u65b9\u5de5\u5177pt-osc\u3002<\/p>\n<p>\u4e0b\u56fe\u662f\u6267\u884c\u65b9\u5f0f\u7684\u6027\u80fd\u5bf9\u6bd4\u53ca\u8bf4\u660e\uff1a<br \/><img decoding=\"async\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/bVc2Ceo\" alt=\"image.png\" title=\"image.png\" loading=\"lazy\"><\/p>\n<p>\u672c\u6587\u5c06\u5bf9DDL\u7684\u6267\u884c\u5de5\u5177\u4e4bOnline DDL\u8fdb\u884c\u7b80\u8981\u4ecb\u7ecd\u53ca\u5206\u6790\uff0cpt-osc\u4f1a\u4e13\u95e8\u518d\u8fdb\u884c\u4ecb\u7ecd\u3002<\/p>\n<h3>3 \u4ecb\u7ecd<\/h3>\n<p>MySQL Online DDL \u529f\u80fd\u4ece 5.6 \u7248\u672c\u5f00\u59cb\u6b63\u5f0f\u5f15\u5165\uff0c\u53d1\u5c55\u5230\u73b0\u5728\u7684 8.0 \u7248\u672c\uff0c\u7ecf\u5386\u4e86\u591a\u6b21\u7684\u8c03\u6574\u548c\u5b8c\u5584\u3002\u5176\u5b9e\u65e9\u5728 MySQL 5.5 \u7248\u672c\u4e2d\u5c31\u52a0\u5165\u4e86 INPLACE DDL \u65b9\u5f0f\uff0c\u4f46\u662f\u56e0\u4e3a\u5b9e\u73b0\u7684\u95ee\u9898\uff0c\u4f9d\u7136\u4f1a\u963b\u585e INSERT\u3001UPDATE\u3001DELETE \u64cd\u4f5c\uff0c\u8fd9\u4e5f\u662f MySQL \u65e9\u671f\u7248\u672c\u957f\u671f\u88ab\u5410\u69fd\u7684\u539f\u56e0\u4e4b\u4e00\u3002<\/p>\n<p>\u5728MySQL 5.6\u7248\u672c\u4ee5\u524d\uff0c\u6700\u6602\u8d35\u7684\u6570\u636e\u5e93\u64cd\u4f5c\u4e4b\u4e00\u5c31\u662f\u6267\u884cDDL\u8bed\u53e5\uff0c\u7279\u522b\u662fALTER\u8bed\u53e5\uff0c\u56e0\u4e3a\u5728\u4fee\u6539\u8868\u65f6\uff0cMySQL\u4f1a\u963b\u585e\u6574\u4e2a\u8868\u7684\u8bfb\u5199\u64cd\u4f5c\u3002\u4f8b\u5982\uff0c\u5bf9\u8868 A \u8fdb\u884c DDL \u7684\u5177\u4f53\u8fc7\u7a0b\u5982\u4e0b\uff1a<\/p>\n<ol>\n<li>\u6309\u7167\u8868 A \u7684\u5b9a\u4e49\u65b0\u5efa\u4e00\u4e2a\u8868 B<\/li>\n<li>\u5bf9\u8868 A \u52a0\u5199\u9501<\/li>\n<li>\u5728\u8868 B \u4e0a\u6267\u884c DDL \u6307\u5b9a\u7684\u64cd\u4f5c<\/li>\n<li>\u5c06 A \u4e2d\u7684\u6570\u636e\u62f7\u8d1d\u5230 B<\/li>\n<li>\u91ca\u653e A \u7684\u5199\u9501<\/li>\n<li>\u5220\u9664\u8868 A<\/li>\n<li>\u5c06\u8868 B \u91cd\u547d\u540d\u4e3a A<\/li>\n<\/ol>\n<p>\u5728\u4ee5\u4e0a 2-4 \u7684\u8fc7\u7a0b\u4e2d\uff0c\u5982\u679c\u8868 A \u6570\u636e\u91cf\u6bd4\u8f83\u5927\uff0c\u62f7\u8d1d\u5230\u8868 B \u7684\u8fc7\u7a0b\u4f1a\u6d88\u8017\u5927\u91cf\u65f6\u95f4\uff0c\u5e76\u5360\u7528\u989d\u5916\u7684\u5b58\u50a8\u7a7a\u95f4\u3002\u6b64\u5916\uff0c\u7531\u4e8e DDL \u64cd\u4f5c\u5360\u7528\u4e86\u8868 A \u7684\u5199\u9501\uff0c\u6240\u4ee5\u8868 A \u4e0a\u7684 DDL \u548c DML \u90fd\u5c06\u963b\u585e\u65e0\u6cd5\u63d0\u4f9b\u670d\u52a1\u3002<\/p>\n<p>\u5982\u679c\u9047\u5230\u5de8\u5927\u7684\u8868\uff0c\u53ef\u80fd\u9700\u8981\u51e0\u4e2a\u5c0f\u65f6\u624d\u80fd\u6267\u884c\u5b8c\u6210\uff0c\u52bf\u5fc5\u4f1a\u5f71\u54cd\u5e94\u7528\u7a0b\u5e8f\uff0c\u56e0\u6b64\u9700\u8981\u5bf9\u8fd9\u4e9b\u64cd\u4f5c\u8fdb\u884c\u826f\u597d\u7684\u89c4\u5212\uff0c\u4ee5\u907f\u514d\u5728\u9ad8\u5cf0\u65f6\u6bb5\u6267\u884c\u8fd9\u4e9b\u66f4\u6539\u3002\u5bf9\u4e8e\u90a3\u4e9b\u8981\u63d0\u4f9b\u5168\u5929\u5019\u670d\u52a1\uff0824*7\uff09\u6216\u7ef4\u62a4\u65f6\u95f4\u6709\u9650\u7684\u4eba\u6765\u8bf4\uff0c\u5728\u5927\u8868\u4e0a\u6267\u884cDDL\u65e0\u7591\u662f\u4e00\u573a\u771f\u6b63\u7684\u5669\u68a6\u3002<\/p>\n<p>\u56e0\u6b64\uff0cMySQL\u5b98\u65b9\u4e0d\u65ad\u5bf9DDL\u8bed\u53e5\u8fdb\u884c\u589e\u5f3a\uff0c\u81eaMySQL 5.6 \u8d77\uff0c\u5f00\u59cb\u652f\u6301\u66f4\u591a\u7684 ALTER TABLE \u7c7b\u578b\u64cd\u4f5c\u6765\u907f\u514d\u6570\u636e\u62f7\u8d1d\uff0c\u540c\u65f6\u652f\u6301\u4e86\u5728\u7ebf\u4e0a DDL \u7684\u8fc7\u7a0b\u4e2d\u4e0d\u963b\u585e DML \u64cd\u4f5c\uff0c\u771f\u6b63\u610f\u4e49\u4e0a\u7684\u5b9e\u73b0\u4e86 Online DDL\uff0c\u5373\u5728\u6267\u884c DDL \u671f\u95f4\u5141\u8bb8\u5728\u4e0d\u4e2d\u65ad\u6570\u636e\u5e93\u670d\u52a1\u7684\u60c5\u51b5\u4e0b\u6267\u884cDML(insert\u3001update\u3001delete)\u3002\u7136\u800c\u5e76\u4e0d\u662f\u6240\u6709\u7684DDL\u64cd\u4f5c\u90fd\u652f\u6301\u5728\u7ebf\u64cd\u4f5c\u3002\u5230\u4e86 MySQL 5.7\uff0c\u5728 5.6 \u7684\u57fa\u7840\u4e0a\u53c8\u589e\u52a0\u4e86\u4e00\u4e9b\u65b0\u7684\u7279\u6027\uff0c\u6bd4\u5982\uff1a\u589e\u52a0\u4e86\u91cd\u547d\u540d\u7d22\u5f15\u652f\u6301\uff0c\u652f\u6301\u4e86\u6570\u503c\u7c7b\u578b\u957f\u5ea6\u7684\u589e\u5927\u548c\u51cf\u5c0f\uff0c\u652f\u6301\u4e86 VARCHAR \u7c7b\u578b\u7684\u5728\u7ebf\u589e\u5927\u7b49\u3002\u4f46\u662f\u57fa\u672c\u7684\u5b9e\u73b0\u903b\u8f91\u548c\u9650\u5236\u6761\u4ef6\u76f8\u6bd4 5.6 \u5e76\u6ca1\u6709\u5927\u7684\u53d8\u5316\u3002<\/p>\n<h3>4 \u7528\u6cd5<\/h3>\n<pre><code>ALTER TABLE tbl_name ADD PRIMARY KEY (column), ALGORITHM=INPLACE, LOCK=NONE;<\/code><\/pre>\n<p>ALTER \u8bed\u53e5\u4e2d\u53ef\u4ee5\u6307\u5b9a\u53c2\u6570 ALGORITHM \u548c LOCK \u5206\u522b\u6307\u5b9a DDL \u6267\u884c\u7684\u7b97\u6cd5\u6a21\u5f0f\u548c DDL \u671f\u95f4 DML \u7684\u9501\u63a7\u5236\u6a21\u5f0f\u3002<\/p>\n<ul>\n<li>ALGORITHM=INPLACE \u8868\u793a\u6267\u884cDDL\u7684\u8fc7\u7a0b\u4e2d\u4e0d\u53d1\u751f\u8868\u62f7\u8d1d\uff0c\u8fc7\u7a0b\u4e2d\u5141\u8bb8\u5e76\u53d1\u6267\u884cDML\uff08INPLACE\u4e0d\u9700\u8981\u50cfCOPY\u4e00\u6837\u5360\u7528\u5927\u91cf\u7684\u78c1\u76d8I\/O\u548cCPU\uff0c\u51cf\u5c11\u4e86\u6570\u636e\u5e93\u8d1f\u8f7d\u3002\u540c\u65f6\u51cf\u5c11\u4e86buffer pool\u7684\u4f7f\u7528\uff0c\u907f\u514d buffer pool \u4e2d\u539f\u6709\u7684\u67e5\u8be2\u7f13\u5b58\u88ab\u5927\u91cf\u5220\u9664\u800c\u5bfc\u81f4\u7684\u6027\u80fd\u95ee\u9898\uff09\u3002<\/li>\n<li>\u5982\u679c\u8bbe\u7f6e ALGORITHM=COPY\uff0cDDL \u5c31\u4f1a\u6309 MySQL 5.6 \u4e4b\u524d\u7684\u65b9\u5f0f\uff0c\u91c7\u7528\u8868\u62f7\u8d1d\u7684\u65b9\u5f0f\u8fdb\u884c\uff0c\u8fc7\u7a0b\u4e2d\u4f1a\u963b\u585e\u6240\u6709\u7684DML\u3002\u53e6\u5916\u4e5f\u53ef\u4ee5\u8bbe\u7f6e ALGORITHEM=DAFAULT\uff0c\u8ba9 MySQL \u4ee5\u5c3d\u91cf\u4fdd\u8bc1 DML \u5e76\u53d1\u64cd\u4f5c\u7684\u539f\u5219\u9009\u62e9\u6267\u884c\u65b9\u5f0f\u3002<\/li>\n<li>LOCK=NONE \u8868\u793a\u5bf9 DML \u64cd\u4f5c\u4e0d\u52a0\u9501\uff0cDDL \u8fc7\u7a0b\u4e2d\u5141\u8bb8\u6240\u6709\u7684 DML \u64cd\u4f5c\u3002\u6b64\u5916\u8fd8\u6709 EXCLUSIVE\uff08\u6301\u6709\u6392\u5b83\u9501\uff0c\u963b\u585e\u6240\u6709\u7684\u8bf7\u6c42\uff0c\u9002\u7528\u4e8e\u9700\u8981\u5c3d\u5feb\u5b8c\u6210DDL\u6216\u8005\u670d\u52a1\u5e93\u7a7a\u95f2\u7684\u573a\u666f\uff09\u3001SHARED\uff08\u5141\u8bb8SELECT\uff0c\u4f46\u662f\u963b\u585eINSERT UPDATE DELETE\uff0c\u9002\u7528\u4e8e\u6570\u636e\u4ed3\u5e93\u7b49\u53ef\u4ee5\u5141\u8bb8\u6570\u636e\u5199\u5165\u5ef6\u8fdf\u7684\u573a\u666f\uff09\u548c DEFAULT\uff08\u6839\u636eDDL\u7684\u7c7b\u578b\uff0c\u5728\u4fdd\u8bc1\u6700\u5927\u5e76\u53d1\u7684\u539f\u5219\u4e0b\u6765\u9009\u62e9LOCK\u7684\u53d6\u503c\uff09\u3002<\/li>\n<\/ul>\n<h3>5 \u4e24\u79cd\u7b97\u6cd5<\/h3>\n<p>\u7b2c\u4e00\u79cd Copy\uff1a<\/p>\n<ol>\n<li>\u6309\u7167\u539f\u8868\u5b9a\u4e49\u521b\u5efa\u4e00\u4e2a\u65b0\u7684\u4e34\u65f6\u8868\uff1b<\/li>\n<li>\u5bf9\u539f\u8868\u52a0\u5199\u9501\uff08\u7981\u6b62DML\uff0c\u5141\u8bb8select\uff09\uff1b<\/li>\n<li>\u5728\u6b65\u9aa41 \u5efa\u7acb\u7684\u4e34\u65f6\u8868\u6267\u884c DDL\uff1b<\/li>\n<li>\u5c06\u539f\u8868\u4e2d\u7684\u6570\u636e copy \u5230\u4e34\u65f6\u8868\uff1b<\/li>\n<li>\u91ca\u653e\u539f\u8868\u7684\u5199\u9501\uff1b<\/li>\n<li>\u5c06\u539f\u8868\u5220\u9664\uff0c\u5e76\u5c06\u4e34\u65f6\u8868\u91cd\u547d\u540d\u4e3a\u539f\u8868\u3002<\/li>\n<li>\u4ece\u4e0a\u53ef\u89c1\uff0c\u91c7\u7528 copy \u65b9\u5f0f\u671f\u95f4\u9700\u8981\u9501\u8868\uff0c\u7981\u6b62DML\uff0c\u56e0\u6b64\u662f\u975eOnline\u7684\u3002\u6bd4\u5982\uff1a\u5220\u9664\u4e3b\u952e\u3001\u4fee\u6539\u5217\u7c7b\u578b\u3001\u4fee\u6539\u5b57\u7b26\u96c6\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u4f1a\u5bfc\u81f4\u884c\u8bb0\u5f55\u683c\u5f0f\u53d1\u751f\u53d8\u5316\uff08\u65e0\u6cd5\u901a\u8fc7\u5168\u91cf + \u589e\u91cf\u5b9e\u73b0 Online\uff09\u3002<\/li>\n<\/ol>\n<p>\u7b2c\u4e8c\u79cd Inplace\uff1a<\/p>\n<p>\u5728\u539f\u8868\u4e0a\u8fdb\u884c\u66f4\u6539\uff0c\u4e0d\u9700\u8981\u751f\u6210\u4e34\u65f6\u8868\uff0c\u4e0d\u9700\u8981\u8fdb\u884c\u6570\u636ecopy\u7684\u8fc7\u7a0b\u3002\u6839\u636e\u662f\u5426\u884c\u8bb0\u5f55\u683c\u5f0f\uff0c\u53c8\u53ef\u5206\u4e3a\u4e24\u7c7b\uff1a<\/p>\n<ul>\n<li>rebuild\uff1a\u9700\u8981\u91cd\u5efa\u8868\uff08\u91cd\u65b0\u7ec4\u7ec7\u805a\u7c07\u7d22\u5f15\uff09\u3002\u6bd4\u5982 optimize table\u3001\u6dfb\u52a0\u7d22\u5f15\u3001\u6dfb\u52a0\/\u5220\u9664\u5217\u3001\u4fee\u6539\u5217 NULL\/NOT NULL \u5c5e\u6027\u7b49\uff1b<\/li>\n<li>no-rebuild\uff1a\u4e0d\u9700\u8981\u91cd\u5efa\u8868\uff0c\u53ea\u9700\u8981\u4fee\u6539\u8868\u7684\u5143\u6570\u636e\uff0c\u6bd4\u5982\u5220\u9664\u7d22\u5f15\u3001\u4fee\u6539\u5217\u540d\u3001\u4fee\u6539\u5217\u9ed8\u8ba4\u503c\u3001\u4fee\u6539\u5217\u81ea\u589e\u503c\u7b49\u3002<\/li>\n<li>\u5bf9\u4e8e rebuild \u65b9\u5f0f\u5b9e\u73b0 Online \u662f\u901a\u8fc7\u7f13\u5b58 DDL \u671f\u95f4\u7684 DML\uff0c\u5f85 DDL \u5b8c\u6210\u4e4b\u540e\uff0c\u5c06 DML \u5e94\u7528\u5230\u8868\u4e0a\u6765\u5b9e\u73b0\u7684\u3002\u4f8b\u5982\uff0c\u6267\u884c\u4e00\u4e2a alter table A engine=InnoDB; \u91cd\u5efa\u8868\u7684 DDL \u5176\u5927\u81f4\u6d41\u7a0b\u5982\u4e0b\uff1a<\/li>\n<li>\u5efa\u7acb\u4e00\u4e2a\u4e34\u65f6\u6587\u4ef6\uff0c\u626b\u63cf\u8868 A \u4e3b\u952e\u7684\u6240\u6709\u6570\u636e\u9875\uff1b<\/li>\n<li>\u7528\u6570\u636e\u9875\u4e2d\u8868 A \u7684\u8bb0\u5f55\u751f\u6210 B+ \u6811\uff0c\u5b58\u50a8\u5230\u4e34\u65f6\u6587\u4ef6\u4e2d\uff1b<\/li>\n<li>\u751f\u6210\u4e34\u65f6\u6587\u4ef6\u7684\u8fc7\u7a0b\u4e2d\uff0c\u5c06\u6240\u6709\u5bf9 A \u7684\u64cd\u4f5c\u8bb0\u5f55\u5728\u4e00\u4e2a\u65e5\u5fd7\u6587\u4ef6\uff08row log\uff09\u4e2d\uff1b<\/li>\n<li>\u4e34\u65f6\u6587\u4ef6\u751f\u6210\u540e\uff0c\u5c06\u65e5\u5fd7\u6587\u4ef6\u4e2d\u7684\u64cd\u4f5c\u5e94\u7528\u5230\u4e34\u65f6\u6587\u4ef6\uff0c\u5f97\u5230\u4e00\u4e2a\u903b\u8f91\u6570\u636e\u4e0a\u4e0e\u8868 A \u76f8\u540c\u7684\u6570\u636e\u6587\u4ef6\uff1b<\/li>\n<li>\u7528\u4e34\u65f6\u6587\u4ef6\u66ff\u6362\u8868 A \u7684\u6570\u636e\u6587\u4ef6\u3002<\/li>\n<\/ul>\n<p>\u8bf4\u660e\uff1a<\/p>\n<ol>\n<li>\u5728 copy \u6570\u636e\u5230\u65b0\u8868\u671f\u95f4\uff0c\u5728\u539f\u8868\u4e0a\u662f\u52a0\u7684 MDL \u8bfb\u9501\uff08\u5141\u8bb8 DML\uff0c\u7981\u6b62 DDL\uff09\uff1b<\/li>\n<li>\u5728\u5e94\u7528\u589e\u91cf\u671f\u95f4\u5bf9\u539f\u8868\u52a0 MDL \u5199\u9501\uff08\u7981\u6b62 DML \u548c DDL\uff09\uff1b<\/li>\n<li>\u6839\u636e\u8868 A \u91cd\u5efa\u51fa\u6765\u7684\u6570\u636e\u662f\u653e\u5728 tmp_file \u91cc\u7684\uff0c\u8fd9\u4e2a\u4e34\u65f6\u6587\u4ef6\u662f InnoDB \u5728\u5185\u90e8\u521b\u5efa\u51fa\u6765\u7684\uff0c\u6574\u4e2a DDL \u8fc7\u7a0b\u90fd\u5728 InnoDB \u5185\u90e8\u5b8c\u6210\u3002\u5bf9\u4e8e server \u5c42\u6765\u8bf4\uff0c\u6ca1\u6709\u628a\u6570\u636e\u632a\u52a8\u5230\u4e34\u65f6\u8868\uff0c\u662f\u4e00\u4e2a\u539f\u5730\u64cd\u4f5c\uff0c\u8fd9\u5c31\u662f\u201dinplace\u201d\u540d\u79f0\u7684\u6765\u6e90\u3002<\/li>\n<\/ol>\n<p>\u4f7f\u7528Inplace\u65b9\u5f0f\u6267\u884c\u7684DDL\uff0c\u53d1\u751f\u9519\u8bef\u6216\u88abkill\u65f6\uff0c\u9700\u8981\u4e00\u5b9a\u65f6\u95f4\u7684\u56de\u6eda\u671f\uff0c\u6267\u884c\u65f6\u95f4\u8d8a\u957f\uff0c\u56de\u6eda\u65f6\u95f4\u8d8a\u957f\u3002<\/p>\n<p>\u4f7f\u7528Copy\u65b9\u5f0f\u6267\u884c\u7684DDL\uff0c\u9700\u8981\u8bb0\u5f55\u8fc7\u7a0b\u4e2d\u7684undo\u548credo\u65e5\u5fd7\uff0c\u540c\u65f6\u4f1a\u6d88\u8017buffer pool\u7684\u8d44\u6e90\uff0c\u6548\u7387\u8f83\u4f4e\uff0c\u4f18\u70b9\u662f\u53ef\u4ee5\u5feb\u901f\u505c\u6b62\u3002<\/p>\n<p>\u4e0d\u8fc7\u5e76\u4e0d\u662f\u6240\u6709\u7684 DDL \u64cd\u4f5c\u90fd\u80fd\u7528 INPLACE \u7684\u65b9\u5f0f\u6267\u884c\uff0c\u5177\u4f53\u7684\u652f\u6301\u60c5\u51b5\u53ef\u4ee5\u5728\uff08\u5728\u7ebf DDL \u64cd\u4f5c) \u4e2d\u67e5\u770b\u3002<\/p>\n<p>\u4ee5\u4e0b\u662f\u5e38\u89c1DDL\u64cd\u4f5c\uff1a<br \/><img decoding=\"async\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/bVc2CeP\" alt=\"image.png\" title=\"image.png\" loading=\"lazy\"><\/p>\n<p>\u5b98\u7f51\u652f\u6301\u5217\u8868\uff1a<br \/><img decoding=\"async\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/bVc2CeU\" alt=\"image.png\" title=\"image.png\" loading=\"lazy\"><\/p>\n<h3>6 \u6267\u884c\u8fc7\u7a0b<\/h3>\n<p>Online DDL\u4e3b\u8981\u5305\u62ec3\u4e2a\u9636\u6bb5\uff0cprepare\u9636\u6bb5\uff0cddl\u6267\u884c\u9636\u6bb5\uff0ccommit\u9636\u6bb5\u3002\u4e0b\u9762\u5c06\u4e3b\u8981\u4ecb\u7ecdddl\u6267\u884c\u8fc7\u7a0b\u4e2d\u4e09\u4e2a\u9636\u6bb5\u7684\u6d41\u7a0b\u3002<\/p>\n<p>1\uff09Prepare\u9636\u6bb5\uff1a\u521d\u59cb\u5316\u9636\u6bb5\u4f1a\u6839\u636e\u5b58\u50a8\u5f15\u64ce\u3001\u7528\u6237\u6307\u5b9a\u7684\u64cd\u4f5c\u3001\u7528\u6237\u6307\u5b9a\u7684 ALGORITHM \u548c LOCK \u8ba1\u7b97 DDL \u8fc7\u7a0b\u4e2d\u5141\u8bb8\u7684\u5e76\u53d1\u91cf\uff0c\u8fd9\u4e2a\u8fc7\u7a0b\u4e2d\u4f1a\u83b7\u53d6\u4e00\u4e2a shared metadata lock\uff0c\u7528\u6765\u4fdd\u62a4\u8868\u7684\u7ed3\u6784\u5b9a\u4e49\u3002<\/p>\n<ul>\n<li>\u521b\u5efa\u65b0\u7684\u4e34\u65f6frm\u6587\u4ef6(\u4e0eInnoDB\u65e0\u5173)\u3002<\/li>\n<li>\u6301\u6709EXCLUSIVE-MDL\u9501\uff0c\u7981\u6b62\u8bfb\u5199\u3002<\/li>\n<li>\u6839\u636ealter\u7c7b\u578b\uff0c\u786e\u5b9a\u6267\u884c\u65b9\u5f0f(copy,online-rebuild,online-norebuild)\u3002\u5047\u5982\u662fAdd Index\uff0c\u5219\u9009\u62e9online-norebuild\u5373INPLACE\u65b9\u5f0f\u3002<\/li>\n<li>\u66f4\u65b0\u6570\u636e\u5b57\u5178\u7684\u5185\u5b58\u5bf9\u8c61\u3002<\/li>\n<li>\u5206\u914drow_log\u5bf9\u8c61\u6765\u8bb0\u5f55\u589e\u91cf(\u4ec5rebuild\u7c7b\u578b\u9700\u8981)\u3002<\/li>\n<li>\u751f\u6210\u65b0\u7684\u4e34\u65f6ibd\u6587\u4ef6(\u4ec5rebuild\u7c7b\u578b\u9700\u8981) \u3002<\/li>\n<li>\u6570\u636e\u5b57\u5178\u4e0a\u63d0\u4ea4\u4e8b\u52a1\u3001\u91ca\u653e\u9501\u3002<\/li>\n<\/ul>\n<p>\u6ce8\uff1aRow log\u662f\u4e00\u79cd\u72ec\u5360\u7ed3\u6784\uff0c\u5b83\u4e0d\u662fredo log\u3002\u5b83\u4ee5Block\u7684\u65b9\u5f0f\u7ba1\u7406DML\u8bb0\u5f55\u7684\u5b58\u653e\uff0c\u4e00\u4e2aBlock\u7684\u5927\u5c0f\u4e3a\u7531\u53c2\u6570innodb_sort_buffer_size\u63a7\u5236\uff0c\u9ed8\u8ba4\u5927\u5c0f\u4e3a1M\uff0c\u521d\u59cb\u5316\u9636\u6bb5\u4f1a\u7533\u8bf7\u4e24\u4e2aBlock\u3002<\/p>\n<p>2\uff09DDL\u6267\u884c\u9636\u6bb5\uff1a\u6267\u884c\u671f\u95f4\u7684 shared metadata lock \u4fdd\u8bc1\u4e86\u4e0d\u4f1a\u540c\u65f6\u6267\u884c\u5176\u4ed6\u7684 DDL\uff0c\u4f46 DML \u80fd\u53ef\u4ee5\u6b63\u5e38\u6267\u884c\u3002<\/p>\n<ul>\n<li>\u964d\u7ea7EXCLUSIVE-MDL\u9501\uff0c\u5141\u8bb8\u8bfb\u5199\uff08copy\u4e0d\u53ef\u5199\uff09\u3002<\/li>\n<li>\u626b\u63cfold_table\u7684\u805a\u96c6\u7d22\u5f15\u6bcf\u4e00\u6761\u8bb0\u5f55rec\u3002<\/li>\n<li>\u904d\u5386\u65b0\u8868\u7684\u805a\u96c6\u7d22\u5f15\u548c\u4e8c\u7ea7\u7d22\u5f15\uff0c\u9010\u4e00\u5904\u7406\u3002<\/li>\n<li>\u6839\u636erec\u6784\u9020\u5bf9\u5e94\u7684\u7d22\u5f15\u9879<\/li>\n<li>\u5c06\u6784\u9020\u7d22\u5f15\u9879\u63d2\u5165sort_buffer\u5757\u6392\u5e8f\u3002<\/li>\n<li>\u5c06sort_buffer\u5757\u66f4\u65b0\u5230\u65b0\u7684\u7d22\u5f15\u4e0a\u3002<\/li>\n<li>\u8bb0\u5f55ddl\u6267\u884c\u8fc7\u7a0b\u4e2d\u4ea7\u751f\u7684\u589e\u91cf(\u4ec5rebuild\u7c7b\u578b\u9700\u8981)<\/li>\n<li>\u91cd\u653erow_log\u4e2d\u7684\u64cd\u4f5c\u5230\u65b0\u7d22\u5f15\u4e0a(no-rebuild\u6570\u636e\u662f\u5728\u539f\u8868\u4e0a\u66f4\u65b0\u7684)\u3002<\/li>\n<li>\u91cd\u653erow_log\u95f4\u4ea7\u751fdml\u64cd\u4f5cappend\u5230row_log\u6700\u540e\u4e00\u4e2aBlock\u3002<\/li>\n<\/ul>\n<p>3\uff09Commit\u9636\u6bb5\uff1a\u5c06 shared metadata lock \u5347\u7ea7\u4e3a exclusive metadata lock\uff0c\u7981\u6b62DML\uff0c\u7136\u540e\u5220\u9664\u65e7\u7684\u8868\u5b9a\u4e49\uff0c\u63d0\u4ea4\u65b0\u7684\u8868\u5b9a\u4e49\u3002<\/p>\n<ul>\n<li>\u5f53\u524dBlock\u4e3arow_log\u6700\u540e\u4e00\u4e2a\u65f6\uff0c\u7981\u6b62\u8bfb\u5199\uff0c\u5347\u7ea7\u5230EXCLUSIVE-MDL\u9501\u3002<\/li>\n<li>\u91cd\u505arow_log\u4e2d\u6700\u540e\u4e00\u90e8\u5206\u589e\u91cf\u3002<\/li>\n<li>\u66f4\u65b0innodb\u7684\u6570\u636e\u5b57\u5178\u8868\u3002<\/li>\n<li>\u63d0\u4ea4\u4e8b\u52a1(\u5237\u4e8b\u52a1\u7684redo\u65e5\u5fd7)\u3002<\/li>\n<li>\u4fee\u6539\u7edf\u8ba1\u4fe1\u606f\u3002<\/li>\n<li>rename\u4e34\u65f6idb\u6587\u4ef6\uff0cfrm\u6587\u4ef6\u3002<\/li>\n<li>\u53d8\u66f4\u5b8c\u6210\u3002<br \/><img decoding=\"async\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/bVc2CeY\" alt=\"image.png\" title=\"image.png\" loading=\"lazy\"><\/li>\n<\/ul>\n<p>Online DDL \u8fc7\u7a0b\u4e2d\u5360\u7528 exclusive MDL \u7684\u6b65\u9aa4\u6267\u884c\u5f88\u5feb\uff0c\u6240\u4ee5\u51e0\u4e4e\u4e0d\u4f1a\u963b\u585e DML \u8bed\u53e5\u3002<\/p>\n<p>\u4e0d\u8fc7\uff0c\u5728 DDL \u6267\u884c\u524d\u6216\u6267\u884c\u65f6\uff0c\u5176\u4ed6\u4e8b\u52a1\u53ef\u4ee5\u83b7\u53d6 MDL\u3002\u7531\u4e8e\u9700\u8981\u7528\u5230 exclusive MDL\uff0c\u6240\u4ee5\u5fc5\u987b\u8981\u7b49\u5230\u5176\u4ed6\u5360\u6709 metadata lock \u7684\u4e8b\u52a1\u63d0\u4ea4\u6216\u56de\u6eda\u540e\u624d\u80fd\u6267\u884c\u4e0a\u9762\u4e24\u4e2a\u6d89\u53ca\u5230 MDL \u7684\u5730\u65b9\u3002<\/p>\n<h3>7 \u8e29\u5751<\/h3>\n<p>\u524d\u9762\u63d0\u5230 Online DDL \u6267\u884c\u8fc7\u7a0b\u4e2d\u9700\u8981\u83b7\u53d6 MDL\uff0cMDL (metadata lock) \u662f MySQL 5.5 \u5f15\u5165\u7684\u8868\u7ea7\u9501\uff0c\u5728\u8bbf\u95ee\u4e00\u4e2a\u8868\u7684\u65f6\u5019\u4f1a\u88ab\u81ea\u52a8\u52a0\u4e0a\uff0c\u4ee5\u4fdd\u8bc1\u8bfb\u5199\u7684\u6b63\u786e\u6027\u3002\u5f53\u5bf9\u4e00\u4e2a\u8868\u505a DML \u64cd\u4f5c\u7684\u65f6\u5019\uff0c\u52a0 MDL \u8bfb\u9501\uff1b\u5f53\u505a DDL \u64cd\u4f5c\u65f6\u5019\uff0c\u52a0 MDL \u5199\u9501\u3002<\/p>\n<p>\u4e3a\u4e86\u5728\u5927\u8868\u6267\u884c DDL \u7684\u8fc7\u7a0b\u4e2d\u540c\u65f6\u4fdd\u8bc1 DML \u80fd\u5e76\u53d1\u6267\u884c\uff0c\u524d\u9762\u4f7f\u7528\u4e86 ALGORITHM=INPLACE \u7684 Online DDL\uff0c\u4f46\u8fd9\u91cc\u4ecd\u7136\u5b58\u5728\u6b7b\u9501\u7684\u98ce\u9669\uff0c\u95ee\u9898\u5c31\u51fa\u5728 Online DDL \u8fc7\u7a0b\u4e2d\u9700\u8981 exclusive MDL \u7684\u5730\u65b9\u3002<\/p>\n<p>\u4f8b\u5982\uff0cSession 1 \u5728\u4e8b\u52a1\u4e2d\u6267\u884c SELECT \u64cd\u4f5c\uff0c\u6b64\u65f6\u4f1a\u83b7\u53d6 shared MDL\u3002\u7531\u4e8e\u662f\u5728\u4e8b\u52a1\u4e2d\u6267\u884c\uff0c\u6240\u4ee5\u8fd9\u4e2a shared MDL \u53ea\u6709\u5728\u4e8b\u52a1\u7ed3\u675f\u540e\u624d\u4f1a\u88ab\u91ca\u653e\u3002<\/p>\n<pre><code># Session 1&gt; START TRANSACTION;&gt; SELECT * FROM tbl_name;# \u6b63\u5e38\u6267\u884c<\/code><\/pre>\n<p>\u8fd9\u65f6 Session 2 \u60f3\u8981\u6267\u884c DML \u64cd\u4f5c\u4e5f\u53ea\u9700\u8981\u83b7\u53d6 shared MDL\uff0c\u4ecd\u7136\u53ef\u4ee5\u6b63\u5e38\u6267\u884c\u3002<\/p>\n<pre><code># Session 2&gt; SELECT * FROM tbl_name;# \u6b63\u5e38\u6267\u884c<\/code><\/pre>\n<p>\u4f46\u5982\u679c Session 3 \u60f3\u6267\u884c DDL \u64cd\u4f5c\u5c31\u4f1a\u963b\u585e\uff0c\u56e0\u4e3a\u6b64\u65f6 Session 1 \u5df2\u7ecf\u5360\u7528\u4e86 shared MDL\uff0c\u800c DDL \u7684\u6267\u884c\u9700\u8981\u5148\u83b7\u53d6 exclusive MDL\uff0c\u56e0\u6b64\u65e0\u6cd5\u6b63\u5e38\u6267\u884c\u3002<\/p>\n<pre><code># Session 3&gt; ALTER TABLE tbl_name ADD COLUMN n INT;# \u963b\u585e<\/code><\/pre>\n<p>\u901a\u8fc7 show processlist \u53ef\u4ee5\u770b\u5230 ALTER \u64cd\u4f5c\u6b63\u5728\u7b49\u5f85 MDL\u3002<\/p>\n<p>\u7531\u4e8e exclusive MDL \u7684\u83b7\u53d6\u4f18\u5148\u4e8e shared MDL\uff0c\u540e\u7eed\u5c1d\u8bd5\u83b7\u53d6 shared MDL \u7684\u64cd\u4f5c\u4e5f\u5c06\u4f1a\u5168\u90e8\u963b\u585e<\/p>\n<pre><code>+----+-----------------+------------------+------+---------+------+---------------------------------+-----------------+\n| Id | User            | Host             | db   | Command | Time | State                           | Info            |\u2502----+-----------------+------------------+------+---------+------+---------------------------------+-----------------+\n| 11 | root            | 172.17.0.1:53048 | demo | Query   |    3 | Waiting for table metadata lock | alter table ... |+----+-----------------+------------------+------+---------+------+---------------------------------+-----------------+<\/code><\/pre>\n<p>\u5230\u8fd9\u4e00\u6b65\uff0c\u540e\u7eed\u65e0\u8bba\u662f DML \u548c DDL \u90fd\u5c06\u963b\u585e\uff0c\u76f4\u5230 Session 1 \u63d0\u4ea4\u6216\u8005\u56de\u6eda\uff0cSession 1 \u5360\u7528\u7684 shared MDL \u88ab\u91ca\u653e\uff0c\u540e\u9762\u7684\u64cd\u4f5c\u624d\u80fd\u7ee7\u7eed\u6267\u884c\u3002<\/p>\n<p>\u4e0a\u9762\u8fd9\u4e2a\u95ee\u9898\u4e3b\u8981\u6709\u4e24\u4e2a\u539f\u56e0\uff1a<\/p>\n<ol>\n<li>Session 1 \u4e2d\u7684\u4e8b\u52a1\u6ca1\u6709\u53ca\u65f6\u63d0\u4ea4\uff0c\u56e0\u6b64\u963b\u585e\u4e86 Session 3 \u7684 DDL<\/li>\n<li>Session 3 Online DDL \u963b\u585e\u4e86\u540e\u7eed\u7684 DML \u548c DDL<\/li>\n<\/ol>\n<p>\u5bf9\u4e8e\u95ee\u9898 1\uff0c\u6709\u4e9bORM\u6846\u67b6\u9ed8\u8ba4\u5c06\u7528\u6237\u8bed\u53e5\u5c01\u88c5\u6210\u4e8b\u52a1\u6267\u884c\uff0c\u5982\u679c\u5ba2\u6237\u7aef\u7a0b\u5e8f\u4e2d\u65ad\u9000\u51fa\uff0c\u8fd8\u6ca1\u6765\u5f97\u53ca\u63d0\u4ea4\u6216\u8005\u56de\u6eda\u4e8b\u52a1\uff0c\u5c31\u4f1a\u51fa\u73b0 Session 1 \u4e2d\u7684\u60c5\u51b5\u3002\u90a3\u4e48\u6b64\u65f6\u53ef\u4ee5\u5728 infomation_schema.innodb_trx \u4e2d\u627e\u51fa\u672a\u5b8c\u6210\u7684\u4e8b\u52a1\u5bf9\u5e94\u7684\u7ebf\u7a0b\uff0c\u5e76\u5f3a\u5236\u9000\u51fa\u3002<\/p>\n<pre><code>&gt; SELECT * FROM information_schema.innodb_trx\/G*************************** 1. row ***************************trx_id: 421564480355704trx_state: RUNNINGtrx_started: 2022-05-01 014:49:41trx_requested_lock_id: NULLtrx_wait_started: NULLtrx_weight: 0trx_mysql_thread_id: 9trx_query: NULLtrx_operation_state: NULLtrx_tables_in_use: 0trx_tables_locked: 0trx_lock_structs: 0trx_lock_memory_bytes: 1136trx_rows_locked: 0trx_rows_modified: 0trx_concurrency_tickets: 0trx_isolation_level: REPEATABLE READtrx_unique_checks: 1trx_foreign_key_checks: 1trx_last_foreign_key_error: NULLtrx_adaptive_hash_latched: 0trx_adaptive_hash_timeout: 0trx_is_read_only: 0trx_autocommit_non_locking: 0trx_schedule_weight: NULL1 row in set (0.0025 sec)<\/code><\/pre>\n<p>\u53ef\u4ee5\u770b\u5230 Session 1 \u6b63\u5728\u6267\u884c\u7684\u4e8b\u52a1\u5bf9\u5e94\u7684 trx_mysql_thread_id \u4e3a 9\uff0c\u7136\u540e\u6267\u884c KILL 9 \u5373\u53ef\u4e2d\u65ad Session 1 \u4e2d\u7684\u4e8b\u52a1\u3002<br \/>\u5bf9\u4e8e\u95ee\u9898 2\uff0c\u5728\u67e5\u8be2\u5f88\u591a\u7684\u60c5\u51b5\u4e0b\uff0c\u4f1a\u5bfc\u81f4\u963b\u585e\u7684 session \u8fc5\u901f\u589e\u591a\uff0c\u5bf9\u4e8e\u8fd9\u79cd\u60c5\u51b5\uff0c\u53ef\u4ee5\u5148\u4e2d\u65ad DDL \u64cd\u4f5c\uff0c\u9632\u6b62\u5bf9\u670d\u52a1\u9020\u6210\u8fc7\u5927\u7684\u5f71\u54cd\u3002\u4e5f\u53ef\u4ee5\u5c1d\u8bd5\u5728\u4ece\u5e93\u4e0a\u4fee\u6539\u8868\u7ed3\u6784\u540e\u8fdb\u884c\u4e3b\u4ece\u5207\u6362\u6216\u8005\u4f7f\u7528 pt-osc \u7b49\u7b2c\u4e09\u65b9\u5de5\u5177\u3002<\/p>\n<h3>8 \u9650\u5236<\/h3>\n<ul>\n<li>\u4ec5\u9002\u7528\u4e8eInnoDB\uff08\u8bed\u6cd5\u4e0a\u5b83\u53ef\u4ee5\u4e0e\u5176\u4ed6\u5b58\u50a8\u5f15\u64ce\u4e00\u8d77\u4f7f\u7528\uff0c\u5982MyISAM\uff0c\u4f46MyISAM\u53ea\u5141\u8bb8algorithm = copy\uff0c\u4e0e\u4f20\u7edf\u65b9\u6cd5\u76f8\u540c\uff09\uff1b<\/li>\n<li>\u65e0\u8bba\u4f7f\u7528\u4f55\u79cd\u9501\uff08NONE\uff0c\u5171\u4eab\u6216\u6392\u5b83\uff09\uff0c\u5728\u5f00\u59cb\u548c\u7ed3\u675f\u65f6\u90fd\u9700\u8981\u4e00\u4e2a\u77ed\u6682\u7684\u65f6\u95f4\u6765\u9501\u8868\uff08\u6392\u5b83\u9501\uff09\uff1b<\/li>\n<li>\u5728\u6dfb\u52a0\/\u5220\u9664\u5916\u952e\u65f6\uff0c\u5e94\u8be5\u7981\u7528 foreign_key_checks \u4ee5\u907f\u514d\u8868\u590d\u5236\uff1b<\/li>\n<li>\u4ecd\u7136\u6709\u4e00\u4e9b alter \u64cd\u4f5c\u9700\u8981 copy \u6216 lock \u8868\uff08\u8001\u65b9\u6cd5\uff09\uff0c\u6709\u5173\u54ea\u4e9b\u8868\u66f4\u6539\u9700\u8981\u8868\u590d\u5236\u6216\u8868\u9501\u5b9a\uff0c\u8bf7\u67e5\u770b\u5b98\u7f51\uff1b<\/li>\n<li>\u5982\u679c\u5728\u8868\u4e0a\u6709 ON \u2026 CASCADE \u6216 ON \u2026 SET NULL \u7ea6\u675f\uff0c\u5219\u5728 alter table \u8bed\u53e5\u4e2d\u4e0d\u5141\u8bb8LOCK = NONE\uff1b<\/li>\n<li>Online DDL\u4f1a\u88ab\u590d\u5236\u5230\u4ece\u5e93\uff08\u540c\u4e3b\u5e93\u4e00\u6837\uff0c\u5982\u679c LOCK = NONE\uff0c\u4ece\u5e93\u4e5f\u4e0d\u4f1a\u52a0\u9501\uff09\uff0c\u4f46\u590d\u5236\u672c\u8eab\u5c06\u88ab\u963b\u6b62\uff0c\u56e0\u4e3a alter \u5728\u4ece\u5e93\u4ee5\u5355\u7ebf\u7a0b\u6267\u884c\uff0c\u8fd9\u5c06\u5bfc\u81f4\u4e3b\u4ece\u5ef6\u8fdf\u95ee\u9898\u3002<\/li>\n<\/ul>\n<p>\u5b98\u65b9\u53c2\u8003\u8d44\u6599\uff1aMySQL :: MySQL 5.7 Reference Manual :: 14.13.6 Online DDL Limitations<\/p>\n<h3>9 \u603b\u7ed3<\/h3>\n<p>\u672c\u6b21\u548c\u5927\u5bb6\u4e00\u8d77\u4e86\u89e3SQL\u7684DDL\u3001DML\u53ca\u533a\u522b\uff0c\u4e5f\u4ecb\u7ecd\u4e86Online DDL\u7684\u6267\u884c\u65b9\u5f0f\u3002<\/p>\n<p>\u76ee\u524d\u53ef\u7528\u7684DDL\u64cd\u4f5c\u5de5\u5177\u5305\u62ecpt-osc\uff0cgithub\u7684gh-ost\uff0c\u4ee5\u53caMySQL\u63d0\u4f9b\u7684\u5728\u7ebf\u4fee\u6539\u8868\u7ed3\u6784\u547d\u4ee4Online DDL\u3002pt-osc\u548cgh-ost\u5747\u91c7\u7528\u62f7\u8868\u65b9\u5f0f\u5b9e\u73b0\uff0c\u5373\u521b\u5efa\u4e2a\u7a7a\u7684\u65b0\u8868\uff0c\u901a\u8fc7select+insert\u5c06\u65e7\u8868\u4e2d\u7684\u8bb0\u5f55\u9010\u6b21\u8bfb\u53d6\u5e76\u63d2\u5165\u5230\u65b0\u8868\u4e2d\uff0c\u4e0d\u540c\u4e4b\u5904\u5728\u4e8e\u5904\u7406DDL\u671f\u95f4\u4e1a\u52a1\u5bf9\u8868\u7684DML\u64cd\u4f5c\u3002<\/p>\n<p>\u5230\u4e86MySQL 8.0 \u5b98\u65b9\u4e5f\u5bf9 DDL \u7684\u5b9e\u73b0\u91cd\u65b0\u8fdb\u884c\u4e86\u8bbe\u8ba1\uff0c\u5176\u4e2d\u4e00\u4e2a\u6700\u5927\u7684\u6539\u8fdb\u662f DDL \u64cd\u4f5c\u652f\u6301\u4e86\u539f\u5b50\u7279\u6027\u3002\u53e6\u5916\uff0cOnline DDL \u7684 ALGORITHM \u53c2\u6570\u589e\u52a0\u4e86\u4e00\u4e2a\u65b0\u7684\u9009\u9879\uff1aINSTANT\uff0c\u53ea\u9700\u4fee\u6539\u6570\u636e\u5b57\u5178\u4e2d\u7684\u5143\u6570\u636e\uff0c\u65e0\u9700\u62f7\u8d1d\u6570\u636e\u4e5f\u65e0\u9700\u91cd\u5efa\u8868\uff0c\u540c\u6837\u4e5f\u65e0\u9700\u52a0\u6392\u4ed6 MDL \u9501\uff0c\u539f\u8868\u6570\u636e\u4e5f\u4e0d\u53d7\u5f71\u54cd\u3002\u6574\u4e2a DDL \u8fc7\u7a0b\u51e0\u4e4e\u662f\u77ac\u95f4\u5b8c\u6210\u7684\uff0c\u4e5f\u4e0d\u4f1a\u963b\u585e DML\uff0c\u4e0d\u8fc7\u76ee\u524d8.0\u7684INSTANT\u4f7f\u7528\u8303\u56f4\u8f83\u5c0f\uff0c\u540e\u7eed\u518d\u5bf98.0\u7684INSTANT\u505a\u8be6\u7ec6\u4ecb\u7ecd\u5427\u3002<\/p>\n<p>\u53e6\u5916\uff0c\u6613\u7ef4\u5e73\u53f0\u4e5f\u63d0\u4f9b\u4e86pt-osc\u7684\u6267\u884c\u65b9\u5f0f\uff0c\u4e0b\u6b21\u518d\u4e0e\u5927\u5bb6\u4e00\u8d77\u5206\u4eabpt-osc\u7684\u6267\u884c\u65b9\u5f0f\u5427\uff0c\u656c\u8bf7\u671f\u5f85\uff01<\/p>\n<p>\u4f5c\u8005\uff1a\u5218\u9093\u5fe0<\/p>\n<p><a href=\"https:\/\/segmentfault.com\/a\/1190000042530574\">https:\/\/segmentfault.com\/a\/1190000042530574<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>1 \u5f15\u8a00 \u5927\u5bb6\u597d\uff0c\u4eca\u5929\u4e0e\u5927\u5bb6\u4e00\u8d77\u5206\u4eab\u4e00\u4e0b mysql DDL\u6267\u884c\u65b9\u5f0f\u3002 \u4e00\u822c\u6765\u8bf4MySQL\u5206\u4e3aDDL\uff08\u5b9a\u4e49\uff09\u548c 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