{"id":1942,"date":"2020-07-29T21:25:58","date_gmt":"2020-07-29T13:25:58","guid":{"rendered":"http:\/\/39.97.231.10\/?p=1942"},"modified":"2020-07-29T21:25:58","modified_gmt":"2020-07-29T13:25:58","slug":"mysql%e6%80%a7%e8%83%bd%e4%bc%98%e5%8c%96-%e6%9d%a1%e4%bb%b6%e8%bf%87%e6%bb%a4condition-filtering","status":"publish","type":"post","link":"http:\/\/www.weijing.co\/?p=1942","title":{"rendered":"MySQL\u6027\u80fd\u4f18\u5316-\u6761\u4ef6\u8fc7\u6ee4(Condition Filtering)"},"content":{"rendered":"<div class=\\\"blog_content\\\">\n<div class=\\\"blog_detail\\\">\n<div>\nMySQL\u5728\u5904\u7406join\u67e5\u8be2\u65f6\uff0c\u904d\u5386\u9a71\u52a8\u8868\u7684\u8bb0\u5f55\uff0c\u628a\u9a71\u52a8\u8868\u7684\u8bb0\u5f55\u4f20\u9012\u7ed9\u88ab\u9a71\u52a8\u8868\uff0c\u7136\u540e\u6839\u636ejoin\u8fde\u63a5\u6761\u4ef6\u8fdb\u884c\u5339\u914d\u3002\u4f18\u5316\u5668\u901a\u5e38\u4f1a\u5c06\u66f4\u5c0f\u7684\u8868\u4f5c\u4e3a\u9a71\u52a8\u8868\uff0c\u901a\u8fc7\u5728\u9a71\u52a8\u8868\u4e0a\u505a\u989d\u5916\u7684where\u6761\u4ef6\u8fc7\u6ee4\uff08Condition Filtering\uff09\uff0c\u80fd\u591f\u5c06\u9a71\u52a8\u8868\u9650\u5236\u5728\u4e00\u4e2a\u66f4\u5c0f\u7684\u8303\u56f4\uff0c\u4ee5\u4fbf\u4f18\u5316\u5668\u80fd\u591f\u505a\u51fa\u66f4\u4f18\u7684\u6267\u884c\u8ba1\u5212\u3002<\/p>\n<h4>1. \u4ec0\u4e48\u662f\u6761\u4ef6\u8fc7\u6ee4(Condition Filtering)<\/h4>\n<p>\u5982\u679c\u6ca1\u6709\u4f7f\u7528\u6761\u4ef6\u8fc7\u6ee4\uff0cjoin\u67e5\u8be2\u7684\u9a71\u52a8\u8868\u9884\u4f30\u626b\u63cf\u7684\u8bb0\u5f55\u6570\u4e0e\u7d22\u5f15\u6761\u4ef6\u76f8\u5173\uff0c\u6bd4\u5982\u4e00\u4e2a\u4e8c\u7ea7\u7d22\u5f15 idx_name(name)\uff0cname=\\&#8217;abc\\&#8217; \u7684\u8bb0\u5f55\u6570\u6709100\u4e2a\uff0c\u90a3\u4e48\u6267\u884c\u8ba1\u5212\u4e2d\u7684\u9884\u4f30\u626b\u63cf\u8bb0\u5f55\u6570\u5c31\u662f100\u5de6\u53f3\u3002\u5982\u679c\u6b64\u65f6where\u6761\u4ef6\u4e2d\u5173\u4e8e\u9a71\u52a8\u8868\u6709\u53e6\u5916\u4e00\u4e2a\u6761\u4ef6\u9650\u5236\uff0c\u6bd4\u5982age=20\uff0c\u6ee1\u8db3name=\\&#8217;abc\\&#8217;\u4e14age=20\u7684\u8bb0\u5f55\u6570\u4e3a10\uff0c\u901a\u8fc7\u6761\u4ef6\u8fc7\u6ee4\u540e\uff0c\u5b9e\u9645\u53c2\u4e0e\u5230join\u8fd0\u7b97\u7684\u9a71\u52a8\u8868\u8bb0\u5f55\u6570\u53ea\u670910\u6761\u5de6\u53f3\u3002<br \/>\n\u6761\u4ef6\u8fc7\u6ee4\u6709\u4e00\u4e9b\u9650\u5236\uff1a<\/p>\n<ul>\n<li>\u6761\u4ef6\u53ea\u80fd\u662f\u5e38\u91cf<\/li>\n<li>\u6761\u4ef6\u8fc7\u6ee4\u4e2d\u7684where\u6761\u4ef6\u4e0d\u5728\u7d22\u5f15\u6761\u4ef6\u4e2d<\/li>\n<\/ul>\n<h4>2. \u6761\u4ef6\u8fc7\u6ee4\u5728explain\u4e2d\u7684\u8868\u73b0<\/h4>\n<p>\u5728explain\u7684\u8f93\u51fa\u4e2d\uff0crows\u5b57\u6bb5\u8868\u793a\u6240\u9009\u62e9\u7684\u7d22\u5f15\u8bbf\u95ee\u65b9\u5f0f\u9884\u4f30\u7684\u626b\u63cf\u8bb0\u5f55\u6570\uff0cfiltered\u5b57\u6bb5\u53cd\u6620\u4e86\u6761\u4ef6\u8fc7\u6ee4\uff0cfiltered\u503c\u662f\u4e00\u4e2a\u767e\u5206\u6bd4\uff0c\u6700\u5927\u503c\u662f100\uff0c\u8868\u793a\u6ca1\u6709\u8fdb\u884c\u4efb\u4f55\u8fc7\u6ee4\uff0c\u8be5\u503c\u8d8a\u5c0f\uff0c\u8bf4\u660e\u8fc7\u6ee4\u6548\u679c\u8d8a\u597d\u3002<br \/>\n\u5982\u679c\u4e00\u4e2aSQL\u7684\u6267\u884c\u8ba1\u5212\uff0crows\u4e3a100\uff0cfiltered\u4e3a10%\uff0c\u90a3\u4e48\u6700\u7ec8\u9884\u4f30\u7684\u626b\u63cf\u8bb0\u5f55\u6570\u4e3a 100*10%=10\u3002<\/p>\n<h4>3. \u6761\u4ef6\u8fc7\u6ee4\u6848\u4f8b<\/h4>\n<p>\u6709\u4e24\u5f20\u8868\u505ajoin\u67e5\u8be2\uff0cemployee \u4e3a\u96c7\u5458\u8868\uff0cdepartment\u4e3a\u90e8\u95e8\u8868\uff0c\u67e5\u8be2SQL\u5982\u4e0b\uff1a<\/p>\n<pre><code>SELECT *\n  FROM employee JOIN department ON employee.dept_no = department.dept_no\n  WHERE employee.first_name = \\'John\\'\n  AND employee.hire_date BETWEEN \\'2018-01-01\\' AND \\'2018-06-01\\';\n<\/code><\/pre>\n<ul>\n<li>employee\u8868\u8bb0\u5f55\u603b\u6570\uff1a1024<\/li>\n<li>department\u8868\u8bb0\u5f55\u603b\u6570\uff1a12<\/li>\n<li>\u4e24\u5f20\u8868\u5728dept_no\u5b57\u6bb5\u4e0a\u90fd\u6709\u7d22\u5f15\u3002<\/li>\n<li>employee\u8868\u5728first_name\u4e0a\u6709\u7d22\u5f15\u3002<\/li>\n<li>\u6ee1\u8db3 employee.first_name = \\&#8217;John\\&#8217; \u7684\u8bb0\u5f55\u6570\uff1a8<\/li>\n<li>\u6ee1\u8db3 employee.hire_date BETWEEN \\&#8217;2018-01-01\\&#8217; AND \\&#8217;2018-06-01\\&#8217; \u7684\u8bb0\u5f55\u6570\uff1a150<\/li>\n<li>\u6ee1\u8db3 employee.first_name = \\&#8217;John\\&#8217; AND employee.hire_date BETWEEN \\&#8217;2018-01-01\\&#8217; AND \\&#8217;2018-06-01\\&#8217; \u8bb0\u5f55\u6570\uff1a1<\/li>\n<\/ul>\n<p><strong>\uff081\uff09\u5982\u679c\u6ca1\u6709\u4f7f\u7528\u6761\u4ef6\u8fc7\u6ee4\uff0cexplain\u6267\u884c\u8ba1\u5212\u5982\u4e0b\uff1a<\/strong><\/p>\n<pre><code>+----+------------+--------+------------------+---------+---------+------+----------+\n| id | table      | type   | possible_keys    | key     | ref     | rows | filtered |\n+----+------------+--------+------------------+---------+---------+------+----------+\n| 1  | employee   | ref    | name,h_date,dept | name    | const   | 8    | 100.00   |\n| 1  | department | eq_ref | PRIMARY          | PRIMARY | dept_no | 1    | 100.00   |\n+----+------------+--------+------------------+---------+---------+------+----------+\n<\/code><\/pre>\n<p><strong>\uff082\uff09\u4f7f\u7528\u4e86\u6761\u4ef6\u8fc7\u6ee4\uff0cexplain\u6267\u884c\u8ba1\u5212\u5982\u4e0b\uff1a<\/strong><\/p>\n<pre><code>+----+------------+--------+------------------+---------+---------+------+----------+\n| id | table      | type   | possible_keys    | key     | ref     | rows | filtered |\n+----+------------+--------+------------------+---------+---------+------+----------+\n| 1  | employee   | ref    | name,h_date,dept | name    | const   | 8    | 16.31    |\n| 1  | department | eq_ref | PRIMARY          | PRIMARY | dept_no | 1    | 100.00   |\n+----+------------+--------+------------------+---------+---------+------+----------+\n<\/code><\/pre>\n<p>\u5f88\u660e\u663e\uff0c\u8868employee\u4e0a\u7684filtered \u7531 100 \u53d8\u4e3a\u4e86 16.31\uff0c8 \u00d7 16.31% = 1.3\uff0c\u8fc7\u6ee4\u6548\u679c\u975e\u5e38\u597d\u3002<\/p>\n<h4>4. \u6761\u4ef6\u8fc7\u6ee4\u5f00\u5173<\/h4>\n<p>MySQL\u63d0\u4f9b\u4e86\u53c2\u6570\u6765\u63a7\u5236\u662f\u5426\u6253\u5f00\u6761\u4ef6\u8fc7\u6ee4\uff0c\u9ed8\u8ba4\u662f\u6253\u5f00\u7684\u3002<br \/>\nSET optimizer_switch = \\&#8217;condition_fanout_filter=on\\&#8217;;<br \/>\n\u6253\u5f00\u6761\u4ef6\u8fc7\u6ee4\u6709\u65f6\u5e76\u4e0d\u603b\u662f\u80fd\u63d0\u9ad8\u6027\u80fd\uff0c\u4f18\u5316\u5668\u53ef\u80fd\u4f1a\u9ad8\u4f30\u6761\u4ef6\u8fc7\u6ee4\u7684\u5f71\u54cd\uff0c\u4e2a\u522b\u573a\u666f\u4e0b\u4f7f\u7528\u6761\u4ef6\u8fc7\u6ee4\u53cd\u800c\u4f1a\u5bfc\u81f4\u6027\u80fd\u4e0b\u964d\u3002\u5728\u6392\u67e5\u7c7b\u4f3c\u6027\u80fd\u95ee\u9898\u65f6\uff0c\u53ef\u53c2\u8003\u4ee5\u4e0b\u601d\u8def\uff1a<\/p>\n<ol>\n<li>join\u8fde\u63a5\u7684\u5b57\u6bb5\u662f\u5426\u6709\u7d22\u5f15\uff0c\u5982\u679c\u6ca1\u6709\u7d22\u5f15\uff0c\u5219\u5e94\u5f53\u5148\u52a0\u4e0a\u7d22\u5f15\uff0c\u4ee5\u4fbf\u4f18\u5316\u5668\u80fd\u591f\u638c\u63e1\u5b57\u6bb5\u503c\u7684\u5206\u5e03\u60c5\u51b5\uff0c\u66f4\u51c6\u786e\u7684\u9884\u4f30\u884c\u6570\u3002<\/li>\n<li>\u8868\u7684join\u987a\u5e8f\u662f\u5426\u5408\u9002\uff0c\u901a\u8fc7\u6539\u53d8\u8868\u7684join\u987a\u5e8f\uff0c\u8ba9\u66f4\u5c0f\u7684\u8868\u4f5c\u4e3a\u9a71\u52a8\u8868\u3002\u53ef\u4ee5\u8003\u8651\u4f7f\u7528STRAIGHT_JOIN\uff0c\u5f3a\u5236\u4f18\u5316\u5668\u4f7f\u7528\u6307\u5b9a\u7684\u8868join\u987a\u5e8f\u3002<\/li>\n<li>\u5982\u679c\u4e0d\u4f7f\u7528\u6761\u4ef6\u8fc7\u6ee4\uff0c\u6027\u80fd\u4f1a\u66f4\u597d\uff0c\u90a3\u4e48\u53ef\u4ee5\u5173\u95ed\u4f1a\u8bdd\u7ea7\u6761\u4ef6\u8fc7\u6ee4\u529f\u80fd\u3002<br \/>\nSET optimizer_switch = \\&#8217;condition_fanout_filter=off\\&#8217;;<\/li>\n<\/ol>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>MySQL\u5728\u5904\u7406join\u67e5\u8be2\u65f6\uff0c\u904d\u5386\u9a71\u52a8\u8868\u7684\u8bb0\u5f55\uff0c\u628a\u9a71\u52a8\u8868\u7684\u8bb0\u5f55\u4f20\u9012\u7ed9\u88ab\u9a71\u52a8\u8868\uff0c\u7136\u540e\u6839\u636ejoin\u8fde\u63a5\u6761\u4ef6\u8fdb\u884c\u5339 &hellip;<\/p>\n<p class=\"read-more\"> <a class=\"\" href=\"http:\/\/www.weijing.co\/?p=1942\"> <span class=\"screen-reader-text\">MySQL\u6027\u80fd\u4f18\u5316-\u6761\u4ef6\u8fc7\u6ee4(Condition Filtering)<\/span> \u67e5\u770b\u5168\u6587 &raquo;<\/a><\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"default","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"default","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":""},"categories":[90,88],"tags":[],"uagb_featured_image_src":{"full":false,"thumbnail":false,"medium":false,"medium_large":false,"large":false,"1536x1536":false,"2048x2048":false,"mailpoet_newsletter_max":false,"woocommerce_thumbnail":false,"woocommerce_single":false,"woocommerce_gallery_thumbnail":false,"shop_catalog":false,"shop_single":false,"shop_thumbnail":false},"uagb_author_info":{"display_name":"weijing","author_link":"http:\/\/www.weijing.co\/?author=4"},"uagb_comment_info":0,"uagb_excerpt":"MySQL\u5728\u5904\u7406join\u67e5\u8be2\u65f6\uff0c\u904d\u5386\u9a71\u52a8\u8868\u7684\u8bb0\u5f55\uff0c\u628a\u9a71\u52a8\u8868\u7684\u8bb0\u5f55\u4f20\u9012\u7ed9\u88ab\u9a71\u52a8\u8868\uff0c\u7136\u540e\u6839\u636ejoin\u8fde\u63a5\u6761\u4ef6\u8fdb\u884c\u5339&hellip;","_links":{"self":[{"href":"http:\/\/www.weijing.co\/index.php?rest_route=\/wp\/v2\/posts\/1942"}],"collection":[{"href":"http:\/\/www.weijing.co\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.weijing.co\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.weijing.co\/index.php?rest_route=\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"http:\/\/www.weijing.co\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1942"}],"version-history":[{"count":0,"href":"http:\/\/www.weijing.co\/index.php?rest_route=\/wp\/v2\/posts\/1942\/revisions"}],"wp:attachment":[{"href":"http:\/\/www.weijing.co\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1942"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.weijing.co\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1942"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.weijing.co\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1942"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}