{"id":1708,"date":"2019-01-06T20:04:12","date_gmt":"2019-01-06T12:04:12","guid":{"rendered":"http:\/\/coderbee.net\/?p=1708"},"modified":"2019-01-06T20:05:01","modified_gmt":"2019-01-06T12:05:01","slug":"mysql-innodb-%e4%ba%8c%e7%ba%a7%e7%b4%a2%e5%bc%95%e7%9a%84%e6%8e%92%e5%ba%8f","status":"publish","type":"post","link":"https:\/\/coderbee.net\/index.php\/db\/20190106\/1708","title":{"rendered":"MySQL InnoDB \u4e8c\u7ea7\u7d22\u5f15\u7684\u6392\u5e8f"},"content":{"rendered":"

\u6392\u5e8f\u95ee\u9898<\/h2>\n

\u6700\u8fd1\u770b\u4e86\u6781\u5ba2\u65f6\u95f4\u4e0a \u300aMySQL\u5b9e\u621845\u8bb2\u300b<\/a>\uff0c\u7ea0\u6b63\u4e86\u4e00\u76f4\u4ee5\u6765\u5bf9 InnoDB \u4e8c\u7ea7\u7d22\u5f15\u7684\u4e00\u4e2a\u7406\u89e3\u4e0d\u5230\u4f4d\uff0c\u6b63\u597d\u628a\u76f8\u5173\u5185\u5bb9\u603b\u7ed3\u4e0b\u3002PS\uff1a\u672c\u6587\u7684\u6240\u6709\u6d4b\u8bd5\u57fa\u4e8e MySQL 8.0.13 \u3002<\/p>\n

\u5148\u628a\u95ee\u9898\u629b\u51fa\u6765\uff0c\u4e0b\u9762\u7684 SQL \u6240\u521b\u5efa\u7684\u8868\uff0c\u6709\u4e24\u4e2a\u67e5\u8be2\u8bed\u53e5\uff0c\u54ea\u4e2a\u7d22\u5f15\u662f\u975e\u5fc5\u987b\u7684\uff1f<\/p>\n

CREATE TABLE `geek` (\n  `a` int(11) NOT NULL,\n  `b` int(11) NOT NULL,\n  `c` int(11) NOT NULL,\n  `d` int(11) NOT NULL,\n  PRIMARY KEY (`a`,`b`),\n  KEY `c` (`c`),\n  KEY `ca` (`c`,`a`),\n  KEY `cb` (`c`,`b`)\n) ENGINE=InnoDB;\n\nselect * from geek where c=N order by a limit 1;\nselect * from geek where c=N order by b limit 1;\n<\/code><\/pre>\n
\u4f5c\u8005\u7ed9\u7684\u7b54\u6848\u662f\u7d22\u5f15 c \u548c ca \u7684\u6570\u636e\u6a21\u578b\u662f\u4e00\u6837\u7684\uff0c\u56e0\u6b64 ca \u662f\u591a\u4f59\u7684\u3002\u4e3a\u5565\uff1f\uff1f<\/p>\n
\u6211\u4eec\u77e5\u9053\uff0c\u4e8c\u7ea7\u7d22\u5f15\u91cc\u5b58\u653e\u7684\u4e0d\u662f\u884c\u7684\u4f4d\u7f6e\uff0c\u800c\u662f\u4e3b\u952e\u7684\u503c\uff0c\u4e5f\u77e5\u9053\u7d22\u5f15\u662f\u6709\u5e8f\u7684\u3002<\/p>\n
\u5982\u679c c \u4e0e ca \u7684\u6570\u636e\u6a21\u578b\u4e00\u6837\uff0c\u90a3\u4e48\u5c31\u8981\u6c42\u4e8c\u7ea7\u7d22\u5f15\u7684\u53f6\u5b50\u8282\u70b9\u4e0d\u4ec5\u662f\u6309\u7d22\u5f15\u5217\u6392\u5e8f\u3001\u800c\u4e14\u8fd8\u6309\u5173\u8054\u7684\u4e3b\u952e\u503c\u8fdb\u884c\u6392\u5e8f<\/strong>\u3002<\/p>\n
\u6211\u4ee5\u524d\u7684\u7406\u89e3\u662f \u4e8c\u7ea7\u7d22\u5f15\u53ea\u6309\u7d22\u5f15\u5217<\/strong>\u8fdb\u884c\u6392\u5e8f\uff0c\u4e3b\u952e\u503c\u662f\u4e0d\u6392\u5e8f\u7684\u3002<\/p>\n
\u95ee\u4e86\u4e13\u680f\u4f5c\u8005\uff0c\u5f97\u5230\u7684\u7b54\u590d\u662f\uff1a\u7d22\u5f15 c \u5c31\u662f\u6309\u7167 cab \u8fd9\u6837\u6392\u5e8f\uff0c\uff08\u4e8c\u7ea7\u7d22\u5f15)\uff09\u6709\u4fdd\u8bc1\u4e3b\u952e\u7b97\u8fdb\u53bb\u3001\u8fd8\u662f\u6709\u5e8f\u7684\u3002\uff08PS\uff1a\u975e\u539f\u8bdd\uff0c\u524d\u540e\u95ee\u4e86\u4e09\u6b21\u5f97\u5230\uff09\u3002<\/p>\n
\u672c\u7740 \u5148\u95ee\u662f\u4e0d\u662f\uff0c\u518d\u95ee\u4e3a\u4ec0\u4e48 \u7684\u601d\u8def\uff0c\u8fdb\u884c\u4e00\u756a\u63a2\u7a76\u3002<\/p>\n
<\/p>\n
\u662f\u4e0d\u662f\uff1f<\/h2>\n
\u5982\u679c\u80fd\u76f4\u63a5\u770b InnoDB \u7684\u6570\u636e\u6587\u4ef6\uff0c\u90a3\u5c31\u53ef\u4ee5\u76f4\u63a5\u770b\u51fa\u662f\u4e0d\u662f\u9075\u5faa\u4e86\u8fd9\u6837\u7684\u6392\u5e8f\u89c4\u5219\u3002\u53ef\u60dc\u90a3\u662f\u4e8c\u8fdb\u5236\u6587\u4ef6\uff0c\u53c8\u6ca1\u6709\u987a\u624b\u7684\u5de5\u5177\u53ef\u4ee5\u65b9\u4fbf\u67e5\u770b\uff0c\u653e\u5f03\u3002<\/p>\n
\u540e\u6765\u627e\u5230\u4e86 MySQL \u7684 handler \u8bed\u53e5<\/a>\uff0c\u5b83\u652f\u6301 MyISAM\/InnoDB \u4e24\u79cd\u5f15\u64ce\u7684\u8868\u3002handler \u8bed\u53e5\u63d0\u4f9b\u4e86\u76f4\u63a5\u8bbf\u95ee\u8868\u5b58\u50a8\u5f15\u64ce\u7684\u63a5\u53e3\u3002<\/p>\n
\u4e0b\u9762\u7684\u8bed\u6cd5\u8868\u793a\u8bfb\u53d6\u6307\u5b9a\u8868\u6307\u5b9a\u7d22\u5f15\u7684 \u7b2c\u4e00\u6761\/\u524d\u4e00\u6761\/\u4e0b\u4e00\u6761\/\u6700\u540e\u4e00\u6761 \u8bb0\u5f55\u3002<\/p>\n
handler table_name\/table_name_alias read index_name first\/pre\/next\/last;\n<\/code><\/pre>\n
\u5c31\u7528 handler \u8bed\u53e5\u6765\u9a8c\u8bc1\u4e0b\uff0c\u5148\u5efa\u4e00\u4e2a\u7b80\u5355\u7684\u8868\uff0c\u63d2\u5165\u51e0\u6761\u6570\u636e\uff1a<\/p>\n
create table t_simple (\n    id int primary key,\n    v int,\n    key k_v (v)\n) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;\n\ninsert into t_simple values (1, 5);\ninsert into t_simple values (10, 5);\ninsert into t_simple values (4, 5);\n<\/code><\/pre>\n
\u4e0a\u9762\u7684\u63d2\u5165\u8bed\u53e5\uff0c\u4e8c\u7ea7\u7d22\u5f15\u5217\u7684\u503c\u90fd\u662f\u4e00\u6837\u7684\uff0c\u4e3b\u952e\u4e0d\u662f\u6309\u987a\u5e8f\u7684\uff0c\u8fd9\u6837\u5c31\u53ef\u4ee5\u770b\u904d\u5386\u65f6\u662f\u4e0d\u662f\u6309\u4e3b\u952e\u987a\u5e8f\u5b58\u653e\u7684\u3002<\/p>\n
mysql> handler t_simple open as ts;\nQuery OK, 0 rows affected (0.00 sec)\n\nmysql> handler ts read k_v next;\n+----+------+\n| id | v    |\n+----+------+\n|  1 |    5 |\n+----+------+\n1 row in set (0.00 sec)\n\nmysql> handler ts read k_v next;\n+----+------+\n| id | v    |\n+----+------+\n|  4 |    5 |\n+----+------+\n1 row in set (0.00 sec)\n\nmysql> handler ts read k_v next;\n+----+------+\n| id | v    |\n+----+------+\n| 10 |    5 |\n+----+------+\n1 row in set (0.00 sec)\n<\/code><\/pre>\n
\u4ece\u7ed3\u679c\u53ef\u4ee5\u770b\u5230\uff0c\u904d\u5386\u7684\u4e8c\u7ea7\u7d22\u5f15\uff0c\u503c\u76f8\u7b49\u65f6\uff0c\u6309\u4e3b\u952e\u7684\u987a\u5e8f\u904d\u5386\uff0c\u57fa\u672c\u53ef\u4ee5\u786e\u5b9a\u4e8c\u7ea7\u7d22\u5f15\u4e0d\u4ec5\u6309\u7d22\u5f15\u5217\u6392\u5e8f\uff0c\u8fd8\u6309\u4e3b\u952e\u503c\u6392\u5e8f\u4e86\u3002<\/p>\n
\u4e3a\u4ec0\u4e48\uff1f<\/h2>\n
\u4e4b\u524d\u4e00\u76f4\u6ca1\u770b\u5230\u8bf4 MySQL \u6709\u8fd9\u6837\u7684\u673a\u5236\uff0c\u95ee\u4e86\u524d\u516c\u53f8\u548c\u5148\u516c\u53f8\u7684 DBA \u90fd\u6ca1\u4e86\u89e3\u8fc7\u8fd9\u4e2a\u3002<\/p>\n
\u6700\u540e DBA \u540c\u4e8b\u627e\u5230\u4e86 \u7d22\u5f15\u6269\u5c55, Index Extensions<\/a> \uff0c\u91cc\u9762\u6709\u8fd9\u4e48\u6bb5\u63cf\u8ff0\u505a\u4e86\u8bf4\u660e\uff1a<\/p>\n
\n
InnoDB automatically extends each secondary index by appending the primary key columns to it. Consider this table definition:<\/p>\n<\/blockquote>\n
CREATE TABLE t1 (\n  i1 INT NOT NULL DEFAULT 0,\n  i2 INT NOT NULL DEFAULT 0,\n  d DATE DEFAULT NULL,\n  PRIMARY KEY (i1, i2),\n  INDEX k_d (d)\n) ENGINE = InnoDB;\n<\/code><\/pre>\n
\n
This table defines the primary key on columns (i1, i2). It also defines a secondary index k_d on column (d), but internally InnoDB extends this index and treats it as columns (d, i1, i2).<\/p>\n<\/blockquote>\n
InnoDB \u81ea\u52a8\u6269\u5c55\u6bcf\u4e2a\u4e8c\u7ea7\u7d22\u5f15\uff0c\u628a\u4e3b\u952e\u503c\u8ffd\u52a0\u5230\u7d22\u5f15\u5217\u540e\u9762\uff0c\u628a\u6269\u5c55\u540e\u7684\u7ec4\u5408\u5217\u4f5c\u4e3a\u8be5\u7d22\u5f15\u7684\u7d22\u5f15\u5217\u3002\u5bf9\u4e8e\u4e0a\u9762 t_simple \u8868\u7684 k_v \u7d22\u5f15\uff0c\u6269\u5c55\u540e\u662f (v, id)\u5217\u3002<\/p>\n
\u4f18\u5316\u5668\u4f1a\u6839\u636e\u6269\u5c55\u540e\u7684\u4e8c\u7ea7\u7d22\u5f15\u7684\u4e3b\u952e\u5217\u6765\u51b3\u5b9a\u5982\u4f55\u548c\u662f\u5426\u4f7f\u7528\u90a3\u4e2a\u7d22\u5f15\u3002\u4f18\u5316\u5668\u53ef\u4ee5\u7528\u6269\u5c55\u7684\u4e8c\u7ea7\u7d22\u5f15\u6765\u8fdb\u884c ref,range,index_merge \u7b49\u7c7b\u578b\u7684\u7d22\u5f15\u8bbf\u95ee\u3001\u677e\u6563\u7684\u7d22\u5f15\u626b\u63cf\u3001\u8fde\u63a5\u548c\u6392\u5e8f\u4f18\u5316\uff0c\u4ee5\u53ca min()\/max() \u4f18\u5316\u3002<\/p>\n
\u53ef\u4ee5\u7528 show variables like '%optimizer_switch%';<\/code> \u67e5\u770b\u7d22\u5f15\u6269\u5c55\u662f\u5426\u5f00\u542f\uff1b\u7528 SET optimizer_switch = 'use_index_extensions=on\/off';<\/code> \u8fdb\u884c\u5f00\u542f\u6216\u5173\u95ed\uff0c\u8fd9\u4e2a\u53ea\u5f71\u54cd\u5f53\u524d\u4f1a\u8bdd\u3002<\/p>\n
\u7ecf\u6d4b\u8bd5\uff0c\u54ea\u6015\u5173\u95ed\u4e86\u5f53\u524d\u4f1a\u8bdd\u7684\u7d22\u5f15\u6269\u5c55\uff0c\u7528 handler \u8bbf\u95ee\u65f6\u4ecd\u7136\u6709\u6309\u4e3b\u952e\u6392\u5e8f\u7684\u6548\u679c\u3002<\/p>\n
\n
\u6b22\u8fce\u5173\u6ce8\u6211\u7684\u5fae\u4fe1\u516c\u4f17\u53f7: coderbee\u7b14\u8bb0<\/strong>\uff0c\u53ef\u4ee5\u66f4\u53ca\u65f6\u56de\u590d\u4f60\u7684\u8ba8\u8bba\u3002
\n<\/p>\n","protected":false},"excerpt":{"rendered":"
\u6392\u5e8f\u95ee\u9898 \u6700\u8fd1\u770b\u4e86\u6781\u5ba2\u65f6\u95f4\u4e0a \u300aMySQL\u5b9e\u621845\u8bb2\u300b\uff0c\u7ea0\u6b63\u4e86\u4e00\u76f4\u4ee5\u6765\u5bf9 Inn … \u7ee7\u7eed\u9605\u8bfb →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[215,298],"_links":{"self":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/1708"}],"collection":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/comments?post=1708"}],"version-history":[{"count":12,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/1708\/revisions"}],"predecessor-version":[{"id":1737,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/1708\/revisions\/1737"}],"wp:attachment":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/media?parent=1708"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/categories?post=1708"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/tags?post=1708"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}