{"id":653,"date":"2020-06-21T22:32:26","date_gmt":"2020-06-21T14:32:26","guid":{"rendered":"https:\/\/www.zeroheart.xyz\/wordpress\/?p=653"},"modified":"2020-06-21T22:32:45","modified_gmt":"2020-06-21T14:32:45","slug":"mysql-explain%e7%9a%84%e4%bd%bf%e7%94%a8","status":"publish","type":"post","link":"https:\/\/www.zeroheart.xyz\/wordpress\/?p=653","title":{"rendered":"mysql explain\u7684\u4f7f\u7528"},"content":{"rendered":"\n<p>1.\u5f00\u542f\u6162\u65e5\u5fd7\uff0c\u53ef\u4ee5\u5e2e\u52a9\u6211\u4eec\u5206\u6790\u4e00\u4e9b\u6027\u80fd\u95ee\u9898<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u663e\u793a\u662f\u5426\u5f00\u542f\u4e86\u6162\u67e5\u8be2\u65e5\u5fd7<\/h4>\n\n\n\n<p>show variables like &#8216;slow_query%&#8217;; <\/p>\n\n\n\n<p>show variables like &#8216;%query%&#8217;;<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u5f00\u542f\u6162\u67e5\u8be2\u65e5\u5fd7<\/h4>\n\n\n\n<p>set global slow_query_log = on <\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u6162\u67e5\u8be2\u65e5\u5fd7\u8f93\u51fa\u4f4d\u7f6e<\/h4>\n\n\n\n<p>set global slow_query_log_file = &#8216;\/var\/lib\/mysql\/slow.log&#8217; <br>set global log_queries_not_using_indexes = on <\/p>\n\n\n\n<h4 class=\"wp-block-heading\">\u8bbe\u7f6e\u8017\u65f6\u67e5\u8be2\u65f6\u95f4\u9608\u503c<\/h4>\n\n\n\n<p>set global long_query_time = 1<\/p>\n\n\n\n<p>2.explain\u7684\u7528\u6cd5<\/p>\n\n\n\n<p>expain extended\u51fa\u6765\u7684\u4fe1\u606f\u670910\u5217\uff0c\u5206\u522b\u662fid\u3001select_type\u3001table\u3001type\u3001possible_keys\u3001key\u3001key_len\u3001ref\u3001rows\u3001Extra<\/p>\n\n\n\n<p><strong>\u6982\u8981\u63cf\u8ff0\uff1a<\/strong><br>id:\u9009\u62e9\u6807\u8bc6\u7b26<br>select_type:\u8868\u793a\u67e5\u8be2\u7684\u7c7b\u578b\u3002<br>table:\u8f93\u51fa\u7ed3\u679c\u96c6\u7684\u8868<br>partitions:\u5339\u914d\u7684\u5206\u533a<br>type:\u8868\u793a\u8868\u7684\u8fde\u63a5\u7c7b\u578b<br>possible_keys:\u8868\u793a\u67e5\u8be2\u65f6\uff0c\u53ef\u80fd\u4f7f\u7528\u7684\u7d22\u5f15<br>key:\u8868\u793a\u5b9e\u9645\u4f7f\u7528\u7684\u7d22\u5f15<br>key_len:\u7d22\u5f15\u5b57\u6bb5\u7684\u957f\u5ea6<br>ref:\u5217\u4e0e\u7d22\u5f15\u7684\u6bd4\u8f83<br>rows:\u626b\u63cf\u51fa\u7684\u884c\u6570(\u4f30\u7b97\u7684\u884c\u6570)<br>filtered:\u6309\u8868\u6761\u4ef6\u8fc7\u6ee4\u7684\u884c\u767e\u5206\u6bd4<br>Extra:\u6267\u884c\u60c5\u51b5\u7684\u63cf\u8ff0\u548c\u8bf4\u660e<\/p>\n\n\n\n<p><strong>id\u5217<\/strong><\/p>\n\n\n\n<p>id\u5217\u4e2d\u7684\u6570\u636e\u4e3a\u4e00\u7ec4\u6570\u5b57\uff0c\u8868\u793a\u6267\u884cselect\u8bed\u53e5\u7684\u987a\u5e8f<\/p>\n\n\n\n<p>id\u503c\u76f8\u540c\u65f6\uff0c\u6267\u884c\u987a\u5e8f\u7531\u4e0a\u81f3\u4e0b<\/p>\n\n\n\n<p>id\u503c\u8d8a\u5927\u4f18\u5148\u7ea7\u8d8a\u9ad8\uff0c\u8d8a\u5148\u88ab\u6267\u884c<\/p>\n\n\n\n<p><strong>select_type\u5217<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"640\" height=\"266\" src=\"https:\/\/www.zeroheart.xyz\/wordpress\/wp-content\/uploads\/2020\/06\/image.png\" alt=\"\" class=\"wp-image-663\" srcset=\"https:\/\/www.zeroheart.xyz\/wordpress\/wp-content\/uploads\/2020\/06\/image.png 640w, https:\/\/www.zeroheart.xyz\/wordpress\/wp-content\/uploads\/2020\/06\/image-300x125.png 300w\" sizes=\"(max-width: 640px) 100vw, 640px\" \/><\/figure>\n\n\n\n<p><strong>table\u5217<\/strong><\/p>\n\n\n\n<p>\u8f93\u51fa\u6570\u636e\u884c\u6240\u5728\u7684\u8868\u7684\u540d\u79f0<\/p>\n\n\n\n<p><strong>partitions\u5217<\/strong><\/p>\n\n\n\n<p>\u5bf9\u4e8e\u5206\u533a\u8868\uff0c\u663e\u793a\u67e5\u8be2\u7684\u5206\u533aid\u5bf9\u4e8e\u975e\u5206\u533a\u8868\uff0c\u663e\u793a\u4e3anull<\/p>\n\n\n\n<p><strong>type<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"620\" height=\"578\" src=\"https:\/\/www.zeroheart.xyz\/wordpress\/wp-content\/uploads\/2020\/06\/image-1.png\" alt=\"\" class=\"wp-image-664\" srcset=\"https:\/\/www.zeroheart.xyz\/wordpress\/wp-content\/uploads\/2020\/06\/image-1.png 620w, https:\/\/www.zeroheart.xyz\/wordpress\/wp-content\/uploads\/2020\/06\/image-1-300x280.png 300w\" sizes=\"(max-width: 620px) 100vw, 620px\" \/><\/figure>\n\n\n\n<p><strong>extra \u5217<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"583\" height=\"459\" src=\"https:\/\/www.zeroheart.xyz\/wordpress\/wp-content\/uploads\/2020\/06\/image-2.png\" alt=\"\" class=\"wp-image-665\" srcset=\"https:\/\/www.zeroheart.xyz\/wordpress\/wp-content\/uploads\/2020\/06\/image-2.png 583w, https:\/\/www.zeroheart.xyz\/wordpress\/wp-content\/uploads\/2020\/06\/image-2-300x236.png 300w\" sizes=\"(max-width: 583px) 100vw, 583px\" \/><\/figure>\n\n\n\n<p><strong>possible_key \u5217<\/strong><\/p>\n\n\n\n<p>\u6307\u51faMySQL\u80fd\u4f7f\u7528\u54ea\u4e9b\u7d22\u5f15\u6765\u4f18\u5316\u67e5\u8be2\uff0c\u4e0d\u4e00\u5b9a\u4f1a\u88ab\u4f7f\u7528\u3002<\/p>\n\n\n\n<p><strong>key\u5217<\/strong><\/p>\n\n\n\n<p>\u67e5\u8be2\u4f18\u5316\u5668 \u4f18\u5316\u67e5\u8be2\u5b9e\u9645\u6240\u4f7f\u7528\u7684\u7d22\u5f15\uff0c\u5982\u679c\u6ca1\u6709\u53ef\u7528\u7684\u7d22\u5f15\uff0c\u5219\u663e\u793a\u4e3anull<\/p>\n\n\n\n<p><strong>key_len\u5217<\/strong><\/p>\n\n\n\n<p>\u8868\u793a\u7d22\u5f15\u5b57\u6bb5\u7684\u6700\u5927\u53ef\u80fd\u957f\u5ea6\uff0ckey_len\u7684\u957f\u5ea6\u7531\u5b57\u6bb5\u5b9a\u4e49\u8ba1\u7b97\u800c\u6765\uff0c\u5e76\u975e\u6570\u636e\u7684\u5b9e\u9645\u957f\u5ea6\u3002<\/p>\n\n\n\n<p><strong>ref \u5217<\/strong><\/p>\n\n\n\n<p>\u8868\u793a\u90a3\u4e9b\u5217\u6216\u5e38\u91cf\u88ab\u7528\u4e8e\u67e5\u627e\u7d22\u5f15\u5217\u4e0a\u7684\u503c<\/p>\n\n\n\n<p><strong>rows\u5217<\/strong><\/p>\n\n\n\n<p>\u8868\u793aMySQL\u901a\u8fc7\u7d22\u5f15\u7edf\u8ba1\u4fe1\u606f\uff0c\u4f30\u7b97\u7684\u6240\u9700\u8bfb\u53d6\u7684\u884c\u6570\uff0crows\u7684\u5927\u5c0f\u662f\u4e2a\u7edf\u8ba1\u62bd\u6837\u7ed3\u679c\uff0c\u5e76\u4e0d\u5341\u5206\u51c6\u786e\u3002<\/p>\n\n\n\n<p><strong>Filtered\u5217<\/strong><\/p>\n\n\n\n<p>\u8868\u793a\u8fd4\u56de\u7ed3\u679c\u7684\u884c\u6570\u5360\u9700\u8bfb\u53d6\u884c\u6570\u7684\u767e\u5206\u6bd4\uff0cFiltered\u5217\u7684\u503c\u8d8a\u5927\u8d8a\u597d\uff0cFiltered\u5217\u7684\u503c\u4f9d\u8d56\u4e8e\u7edf\u8ba1\u4fe1\u606f\u3002<\/p>\n\n\n\n<p>\u53c2\u8003\u6587\u7ae0\uff1a<\/p>\n\n\n\n<p><a href=\"https:\/\/baijiahao.baidu.com\/s?id=1663038925363046620&amp;wfr=spider&amp;for=pc\">https:\/\/baijiahao.baidu.com\/s?id=1663038925363046620<\/a><\/p>\n\n\n\n<p><a href=\"https:\/\/www.cnblogs.com\/tufujie\/p\/9413852.html\">https:\/\/www.cnblogs.com\/tufujie\/p\/9413852.html<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>1.\u5f00\u542f\u6162\u65e5\u5fd7\uff0c\u53ef\u4ee5\u5e2e\u52a9\u6211\u4eec\u5206\u6790\u4e00\u4e9b\u6027\u80fd\u95ee\u9898 \u663e\u793a\u662f\u5426\u5f00\u542f\u4e86\u6162\u67e5\u8be2\u65e5\u5fd7 show variables like [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[12],"tags":[31],"_links":{"self":[{"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/653"}],"collection":[{"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=653"}],"version-history":[{"count":14,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/653\/revisions"}],"predecessor-version":[{"id":670,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/653\/revisions\/670"}],"wp:attachment":[{"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=653"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=653"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=653"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}