{"id":20645,"date":"2024-01-02T05:15:25","date_gmt":"2024-01-02T05:15:25","guid":{"rendered":"https:\/\/server.hk\/blog\/20645\/"},"modified":"2024-11-14T10:39:25","modified_gmt":"2024-11-14T02:39:25","slug":"postgresql-command-explain","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/20645\/","title":{"rendered":"PostgreSQL \u6307\u4ee4\uff1aEXPLAIN"},"content":{"rendered":"<h1 id=\"postgresql-command-explain-dKAVuWudcX\">PostgreSQL \u6307\u4ee4\uff1aEXPLAIN<\/h1>\n<p>PostgreSQL \u662f\u4e00\u500b\u529f\u80fd\u5f37\u5927\u7684\u958b\u6e90\u95dc\u4fc2\u578b\u8cc7\u6599\u5eab\u7ba1\u7406\u7cfb\u7d71\uff0c\u63d0\u4f9b\u4e86\u591a\u7a2e\u529f\u80fd\u548c\u80fd\u529b\u3002<code>EXPLAIN<\/code> \u662f PostgreSQL \u4e2d\u4e00\u500b\u91cd\u8981\u7684\u6307\u4ee4\uff0c\u5b83\u5141\u8a31\u4f7f\u7528\u8005\u900f\u904e\u63d0\u4f9b\u6709\u95dc\u8cc7\u6599\u5eab\u5982\u4f55\u57f7\u884c\u67e5\u8a62\u7684\u6df1\u5165\u5206\u6790\u4f86\u512a\u5316\u67e5\u8a62\u6548\u80fd\u3002<\/p>\n<h2 id=\"understanding-explain-dKAVuWudcX\">\u4e86\u89e3 EXPLAIN<\/h2>\n<p>\u7576\u8655\u7406\u8907\u96dc\u7684\u67e5\u8a62\u6216\u5927\u578b\u8cc7\u6599\u96c6\u6642\uff0c\u78ba\u4fdd\u8cc7\u6599\u5eab\u6709\u6548\u7387\u5730\u57f7\u884c\u67e5\u8a62\u662f\u81f3\u95dc\u91cd\u8981\u7684\u3002<code>EXPLAIN<\/code> \u6307\u4ee4\u901a\u904e\u63d0\u4f9b\u7d66\u5b9a\u67e5\u8a62\u7684\u8a73\u7d30\u57f7\u884c\u8a08\u5283\u4f86\u5e6b\u52a9\u5be6\u73fe\u9019\u4e00\u9ede\u3002\u5b83\u8b93\u4f7f\u7528\u8005\u77ad\u89e3\u8cc7\u6599\u5eab\u5982\u4f55\u8655\u7406\u67e5\u8a62\uff0c\u6709\u52a9\u65bc\u8b58\u5225\u6f5b\u5728\u7684\u74f6\u9838\u6216\u9700\u8981\u512a\u5316\u7684\u90e8\u5206\u3002<\/p>\n<p><code>EXPLAIN<\/code> \u6307\u4ee4\u7684\u57fa\u672c\u8a9e\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre><code>EXPLAIN [ ANALYZE ] [ VERBOSE ] query;<\/code><\/pre>\n<p><code>ANALYZE<\/code> \u9078\u9805\u53ef\u5be6\u969b\u57f7\u884c\u67e5\u8a62\u4e26\u6536\u96c6\u904b\u884c\u6642\u7d71\u8a08\u8cc7\u6599\uff0c\u63d0\u4f9b\u66f4\u6e96\u78ba\u7684\u67e5\u8a62\u6548\u80fd\u8cc7\u8a0a\u3002<code>VERBOSE<\/code> \u9078\u9805\u5247\u6703\u5728\u8f38\u51fa\u4e2d\u63d0\u4f9b\u984d\u5916\u7684\u7d30\u7bc0\uff0c\u4f7f\u57f7\u884c\u8a08\u5283\u66f4\u6613\u65bc\u7406\u89e3\u3002<\/p>\n<h2 id=\"interpreting-the-output-dKAVuWudcX\">\u89e3\u8b80\u8f38\u51fa\u7d50\u679c<\/h2>\n<p><code>EXPLAIN<\/code> \u6307\u4ee4\u7684\u8f38\u51fa\u5305\u542b\u591a\u500b\u6b04\u4f4d\uff0c\u9019\u4e9b\u6b04\u4f4d\u63d0\u4f9b\u6709\u95dc\u67e5\u8a62\u57f7\u884c\u8a08\u5283\u6bcf\u500b\u6b65\u9a5f\u7684\u8cc7\u8a0a\u3002\u4ee5\u4e0b\u662f\u4e00\u4e9b\u95dc\u9375\u6b04\u4f4d\uff1a<\/p>\n<ul>\n<li><strong>Node Type\uff1a<\/strong>\u8868\u793a\u6240\u57f7\u884c\u7684\u64cd\u4f5c\u985e\u578b\uff0c\u4f8b\u5982\u9806\u5e8f\u6383\u63cf\u3001\u7d22\u5f15\u6383\u63cf\u6216\u9023\u63a5\u64cd\u4f5c\u3002<\/li>\n<li><strong>Relation Name\uff1a<\/strong>\u88ab\u5b58\u53d6\u7684\u8cc7\u6599\u8868\u6216\u7d22\u5f15\u7684\u540d\u7a31\u3002<\/li>\n<li><strong>Join Type\uff1a<\/strong>\u6307\u5b9a\u6240\u4f7f\u7528\u7684\u9023\u63a5\u985e\u578b\uff0c\u4f8b\u5982\u5167\u90e8\u9023\u63a5\u3001\u5de6\u9023\u63a5\u6216\u53f3\u9023\u63a5\u3002<\/li>\n<li><strong>Filter\uff1a<\/strong>\u5c0d\u8cc7\u6599\u61c9\u7528\u7684\u984d\u5916\u904e\u6ffe\u689d\u4ef6\u3002<\/li>\n<li><strong>Rows\uff1a<\/strong>\u6bcf\u500b\u6b65\u9a5f\u9810\u4f30\u8fd4\u56de\u7684\u884c\u6578\u3002<\/li>\n<li><strong>Cost\uff1a<\/strong>\u6bcf\u500b\u6b65\u9a5f\u7684\u9810\u4f30\u6210\u672c\uff0c\u4ee3\u8868\u6240\u9700\u5de5\u4f5c\u91cf\u7684\u76f8\u5c0d\u5927\u5c0f\u3002<\/li>\n<\/ul>\n<p>\u900f\u904e\u5206\u6790\u9019\u4e9b\u8cc7\u8a0a\uff0c\u4f7f\u7528\u8005\u53ef\u4ee5\u8b58\u5225\u6f5b\u5728\u7684\u6548\u80fd\u554f\u984c\u3002\u4f8b\u5982\uff0c\u4e00\u500b\u6b65\u9a5f\u7684\u9ad8\u6210\u672c\u6216\u8fd4\u56de\u7684\u5927\u91cf\u884c\u6578\u53ef\u80fd\u986f\u793a\u9700\u8981\u9032\u884c\u512a\u5316\u3002\u6b64\u5916\uff0c<code>EXPLAIN<\/code> \u6307\u4ee4\u53ef\u4ee5\u5e6b\u52a9\u8b58\u5225\u7f3a\u5931\u6216\u672a\u5145\u5206\u5229\u7528\u7684\u7d22\u5f15\u3001\u4f4e\u6548\u7684\u9023\u63a5\u7b56\u7565\u6216\u4e0d\u5fc5\u8981\u7684\u8cc7\u6599\u6383\u63cf\u3002<\/p>\n<h2 id=\"using-explain-to-optimize-queries-dKAVuWudcX\">\u4f7f\u7528 EXPLAIN \u4f86\u512a\u5316\u67e5\u8a62<\/h2>\n<p>\u7576 <code>EXPLAIN<\/code> \u6307\u4ee4\u63d0\u4f9b\u67e5\u8a62\u57f7\u884c\u8a08\u5283\u7684\u6d1e\u5bdf\u5f8c\uff0c\u4f7f\u7528\u8005\u53ef\u4ee5\u63a1\u53d6\u63aa\u65bd\u4f86\u512a\u5316\u67e5\u8a62\u3002\u4ee5\u4e0b\u662f\u4e00\u4e9b\u5e38\u898b\u7684\u512a\u5316\u6280\u8853\uff1a<\/p>\n<ul>\n<li><strong>\u7d22\u5f15\uff1a<\/strong>\u5728\u67e5\u8a62\u6d89\u53ca\u7684\u8cc7\u6599\u8868\u4e0a\u5efa\u7acb\u9069\u7576\u7684\u7d22\u5f15\u53ef\u4ee5\u986f\u8457\u63d0\u5347\u6548\u80fd\u3002<\/li>\n<li><strong>\u91cd\u5beb\u67e5\u8a62\uff1a<\/strong>\u4fee\u6539\u67e5\u8a62\u7d50\u69cb\u6216\u4f7f\u7528\u66ff\u4ee3\u8a9e\u6cd5\u6709\u6642\u53ef\u4ee5\u751f\u6210\u66f4\u9ad8\u6548\u7684\u57f7\u884c\u8a08\u5283\u3002<\/li>\n<li><strong>\u9023\u63a5\u7b56\u7565\uff1a<\/strong>\u9078\u64c7\u6b63\u78ba\u7684\u9023\u63a5\u7b56\u7565\uff0c\u4f8b\u5982\u4f7f\u7528\u54c8\u5e0c\u9023\u63a5\u6216\u5d4c\u5957\u8ff4\u5708\uff0c\u53ef\u4ee5\u6539\u5584\u67e5\u8a62\u6548\u80fd\u3002<\/li>\n<li><strong>\u904e\u6ffe\u8207\u805a\u5408\uff1a<\/strong>\u5728\u67e5\u8a62\u7684\u65e9\u671f\u61c9\u7528\u904e\u6ffe\u548c\u805a\u5408\u689d\u4ef6\uff0c\u53ef\u4ee5\u6e1b\u5c11\u9700\u8981\u8655\u7406\u7684\u8cc7\u6599\u91cf\u3002<\/li>\n<\/ul>\n<p>\u900f\u904e\u53cd\u8986\u5206\u6790 <code>EXPLAIN<\/code> \u7684\u8f38\u51fa\u4e26\u61c9\u7528\u512a\u5316\u6280\u8853\uff0c\u4f7f\u7528\u8005\u53ef\u4ee5\u5fae\u8abf\u5176\u67e5\u8a62\u4ee5\u9054\u5230\u6700\u4f73\u6548\u80fd\u3002<\/p>\n<h2 id=\"summary-dKAVuWudcX\">\u7e3d\u7d50<\/h2>\n<p>PostgreSQL \u4e2d\u7684 <code>EXPLAIN<\/code> \u6307\u4ee4\u662f\u4e00\u500b\u5f37\u5927\u7684\u5de5\u5177\uff0c\u7528\u65bc\u5206\u6790\u548c\u512a\u5316\u67e5\u8a62\u6548\u80fd\u3002\u5b83\u901a\u904e\u63d0\u4f9b\u67e5\u8a62\u57f7\u884c\u8a08\u5283\u7684\u8a73\u7d30\u6d1e\u5bdf\uff0c\u5e6b\u52a9\u4f7f\u7528\u8005\u8b58\u5225\u6f5b\u5728\u7684\u74f6\u9838\u548c\u6539\u9032\u5340\u57df\u3002\u7406\u89e3 <code>EXPLAIN<\/code> \u6307\u4ee4\u7684\u8f38\u51fa\uff0c\u8b93\u4f7f\u7528\u8005\u53ef\u4ee5\u5c0d\u7d22\u5f15\u3001\u67e5\u8a62\u7d50\u69cb\u3001\u9023\u63a5\u7b56\u7565\u53ca\u5176\u4ed6\u512a\u5316\u6280\u8853\u505a\u51fa\u660e\u667a\u7684\u6c7a\u7b56\u3002\u82e5\u60f3\u9032\u4e00\u6b65\u4e86\u89e3 PostgreSQL \u4ee5\u53ca\u5b83\u5982\u4f55\u70ba\u4f60\u7684\u696d\u52d9\u5e36\u4f86\u76ca\u8655\uff0c\u5efa\u8b70\u700f\u89bd <a href=\"https:\/\/server.hk\">Server.HK<\/a>\uff0c\u9019\u662f\u4e00\u5bb6\u9818\u5148\u7684 VPS \u8a17\u7ba1\u63d0\u4f9b\u5546\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>PostgreSQL \u6307\u4ee4\uff1aEX&#46;&#46;&#46;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4924],"tags":[],"class_list":["post-20645","post","type-post","status-publish","format-standard","hentry","category-setup-tutorials"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/20645","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=20645"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/20645\/revisions"}],"predecessor-version":[{"id":24367,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/20645\/revisions\/24367"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=20645"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=20645"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=20645"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}