{"id":170087,"date":"2024-11-06T21:02:22","date_gmt":"2024-11-06T13:02:22","guid":{"rendered":"https:\/\/server.hk\/cnblog\/170087\/"},"modified":"2024-11-06T21:02:22","modified_gmt":"2024-11-06T13:02:22","slug":"%e4%bd%a0%e7%9f%a5%e9%81%93hive%e7%b5%b1%e8%a8%88%e5%87%bd%e6%95%b8count%e7%82%ba%e4%bb%80%e9%ba%bc%e4%b8%8d%e8%b5%b0mr%e5%97%8e%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/server.hk\/cnblog\/170087\/","title":{"rendered":"\u4f60\u77e5\u9053Hive\u7d71\u8a08\u51fd\u6578count(*)\u70ba\u4ec0\u9ebc\u4e0d\u8d70MR\u55ce\uff1f"},"content":{"rendered":"

\u4f60\u77e5\u9053Hive\u7d71\u8a08\u51fd\u6578count(*)\u70ba\u4ec0\u9ebc\u4e0d\u8d70MR\u55ce\uff1f<\/h1>\n

\u5728\u5927\u6578\u64da\u8655\u7406\u7684\u9818\u57df\u4e2d\uff0cApache Hive\u4f5c\u70ba\u4e00\u500b\u6578\u64da\u5009\u5eab\u57fa\u790e\u8a2d\u65bd\uff0c\u63d0\u4f9b\u4e86\u4e00\u7a2e\u65b9\u4fbf\u7684\u65b9\u5f0f\u4f86\u67e5\u8a62\u548c\u5206\u6790\u5b58\u5132\u5728Hadoop\u5206\u4f48\u5f0f\u6587\u4ef6\u7cfb\u7d71\uff08HDFS\uff09\u4e2d\u7684\u6578\u64da\u3002Hive\u7684\u67e5\u8a62\u8a9e\u8a00\u985e\u4f3c\u65bcSQL\uff0c\u9019\u4f7f\u5f97\u6578\u64da\u5206\u6790\u5e2b\u548c\u958b\u767c\u8005\u80fd\u5920\u8f15\u9b06\u4e0a\u624b\u3002\u7136\u800c\uff0c\u7576\u6211\u5011\u4f7f\u7528Hive\u9032\u884c\u67e5\u8a62\u6642\uff0c\u7279\u5225\u662f\u4f7f\u7528\u7d71\u8a08\u51fd\u6578count(*)\u6642\uff0c\u53ef\u80fd\u6703\u767c\u73fe\u5b83\u4e0d\u6703\u8d70MapReduce\uff08MR\uff09\u6d41\u7a0b\u3002\u9019\u7bc7\u6587\u7ae0\u5c07\u6df1\u5165\u63a2\u8a0e\u9019\u4e00\u73fe\u8c61\u7684\u539f\u56e0\u53ca\u5176\u80cc\u5f8c\u7684\u6280\u8853\u539f\u7406\u3002<\/p>\n

Hive\u7684\u57f7\u884c\u67b6\u69cb<\/h2>\n

Hive\u7684\u67e5\u8a62\u57f7\u884c\u904e\u7a0b\u901a\u5e38\u6d89\u53ca\u5c07HiveQL\u8f49\u63db\u70baMapReduce\u4f5c\u696d\u3002\u9019\u4e9b\u4f5c\u696d\u6703\u5728Hadoop\u96c6\u7fa4\u4e0a\u4e26\u884c\u57f7\u884c\uff0c\u4ee5\u8655\u7406\u5927\u91cf\u6578\u64da\u3002\u7136\u800c\uff0c\u5c0d\u65bc\u67d0\u4e9b\u67e5\u8a62\uff0cHive\u6703\u9078\u64c7\u4e0d\u4f7f\u7528MapReduce\uff0c\u800c\u662f\u4f7f\u7528\u5176\u4ed6\u66f4\u9ad8\u6548\u7684\u57f7\u884c\u65b9\u5f0f\u3002<\/p>\n

count(*)\u7684\u7279\u6027<\/h2>\n

\u5728Hive\u4e2d\uff0ccount(*)\u662f\u4e00\u500b\u975e\u5e38\u5e38\u7528\u7684\u7d71\u8a08\u51fd\u6578\uff0c\u7528\u65bc\u8a08\u7b97\u8868\u4e2d\u884c\u7684\u6578\u91cf\u3002\u9019\u500b\u51fd\u6578\u7684\u7279\u9ede\u5728\u65bc\u5b83\u4e0d\u9700\u8981\u5c0d\u6578\u64da\u9032\u884c\u4efb\u4f55\u904e\u6ffe\u6216\u8a08\u7b97\uff0c\u53ea\u9700\u7c21\u55ae\u5730\u8a08\u7b97\u884c\u6578\u3002\u9019\u4f7f\u5f97count(*)\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\u53ef\u4ee5\u901a\u904e\u66f4\u9ad8\u6548\u7684\u65b9\u5f0f\u4f86\u57f7\u884c\uff0c\u800c\u4e0d\u5fc5\u4f9d\u8cf4MapReduce\u3002<\/p>\n

\u70ba\u4ec0\u9ebccount(*)\u4e0d\u8d70MR\uff1f<\/h2>\n

1. \u76f4\u63a5\u8a08\u7b97\u884c\u6578<\/strong>: Hive\u5728\u8655\u7406count(*)\u6642\uff0c\u6703\u76f4\u63a5\u5f9e\u5143\u6578\u64da\u4e2d\u7372\u53d6\u884c\u6578\uff0c\u800c\u4e0d\u9700\u8981\u5c0d\u6574\u500b\u6578\u64da\u96c6\u9032\u884c\u6383\u63cf\u3002\u9019\u662f\u56e0\u70baHive\u5728\u5275\u5efa\u8868\u6642\u6703\u7dad\u8b77\u4e00\u4e9b\u7d71\u8a08\u4fe1\u606f\uff0c\u5305\u62ec\u884c\u6578\u3002\u7576\u57f7\u884ccount(*)\u6642\uff0cHive\u53ef\u4ee5\u76f4\u63a5\u67e5\u8a62\u9019\u4e9b\u7d71\u8a08\u4fe1\u606f\uff0c\u5f9e\u800c\u907f\u514d\u4e86MapReduce\u7684\u958b\u92b7\u3002<\/p>\n

2. \u512a\u5316\u67e5\u8a62\u8a08\u5283<\/strong>: Hive\u7684\u67e5\u8a62\u512a\u5316\u5668\u6703\u6839\u64da\u67e5\u8a62\u7684\u7279\u6027\u81ea\u52d5\u9078\u64c7\u6700\u5408\u9069\u7684\u57f7\u884c\u8a08\u5283\u3002\u5c0d\u65bccount(*)\u9019\u985e\u7c21\u55ae\u7684\u805a\u5408\u67e5\u8a62\uff0cHive\u53ef\u80fd\u6703\u9078\u64c7\u4f7f\u7528\u66f4\u8f15\u91cf\u7d1a\u7684\u57f7\u884c\u65b9\u5f0f\uff0c\u4f8b\u5982\u4f7f\u7528Apache Tez\u6216Spark\u7b49\u57f7\u884c\u5f15\u64ce\uff0c\u9019\u4e9b\u5f15\u64ce\u5728\u8655\u7406\u6b64\u985e\u67e5\u8a62\u6642\u6548\u7387\u66f4\u9ad8\u3002<\/p>\n

3. \u907f\u514d\u4e0d\u5fc5\u8981\u7684\u8a08\u7b97<\/strong>: \u4f7f\u7528MapReduce\u9032\u884ccount(*)\u7684\u8a08\u7b97\u6703\u6d89\u53ca\u5230\u591a\u500bMap\u548cReduce\u968e\u6bb5\uff0c\u9019\u6703\u589e\u52a0\u8a08\u7b97\u7684\u5ef6\u9072\u548c\u8cc7\u6e90\u6d88\u8017\u3002\u76f8\u5c0d\u800c\u8a00\uff0c\u76f4\u63a5\u5f9e\u5143\u6578\u64da\u4e2d\u7372\u53d6\u884c\u6578\u53ef\u4ee5\u5927\u5e45\u5ea6\u63d0\u9ad8\u67e5\u8a62\u6027\u80fd\u3002<\/p>\n

\u5be6\u969b\u61c9\u7528\u4e2d\u7684\u8003\u91cf<\/h2>\n

\u5728\u5be6\u969b\u61c9\u7528\u4e2d\uff0c\u4f7f\u7528count(*)\u6642\u9700\u8981\u8003\u616e\u6578\u64da\u7684\u66f4\u65b0\u983b\u7387\u3002\u5982\u679c\u6578\u64da\u7d93\u5e38\u8b8a\u52d5\uff0c\u5143\u6578\u64da\u4e2d\u7684\u884c\u6578\u53ef\u80fd\u4e0d\u518d\u6e96\u78ba\uff0c\u9019\u6642\u5019\u57f7\u884ccount(*)\u53ef\u80fd\u6703\u8fd4\u56de\u904e\u6642\u7684\u7d50\u679c\u3002\u56e0\u6b64\uff0c\u5728\u9019\u7a2e\u60c5\u6cc1\u4e0b\uff0c\u958b\u767c\u8005\u53ef\u80fd\u9700\u8981\u9078\u64c7\u5176\u4ed6\u65b9\u6cd5\u4f86\u78ba\u4fdd\u6578\u64da\u7684\u6e96\u78ba\u6027\uff0c\u4f8b\u5982\u4f7f\u7528count(1)\u4f86\u5f37\u5236Hive\u9032\u884c\u5168\u8868\u6383\u63cf\u3002<\/p>\n

\u7d50\u8ad6<\/h2>\n

\u7e3d\u7d50\u4f86\u8aaa\uff0cHive\u7684count(*)\u51fd\u6578\u4e4b\u6240\u4ee5\u4e0d\u8d70MapReduce\uff0c\u4e3b\u8981\u662f\u56e0\u70ba\u5b83\u80fd\u5920\u76f4\u63a5\u5f9e\u5143\u6578\u64da\u4e2d\u7372\u53d6\u884c\u6578\uff0c\u5f9e\u800c\u907f\u514d\u4e86\u4e0d\u5fc5\u8981\u7684\u8a08\u7b97\u548c\u8cc7\u6e90\u6d88\u8017\u3002\u9019\u4e00\u7279\u6027\u4f7f\u5f97Hive\u5728\u8655\u7406\u7c21\u55ae\u7684\u805a\u5408\u67e5\u8a62\u6642\u66f4\u52a0\u9ad8\u6548\u3002\u7136\u800c\uff0c\u5728\u4f7f\u7528count(*)\u6642\uff0c\u958b\u767c\u8005\u4ecd\u9700\u6ce8\u610f\u6578\u64da\u7684\u66f4\u65b0\u983b\u7387\uff0c\u4ee5\u78ba\u4fdd\u67e5\u8a62\u7d50\u679c\u7684\u6e96\u78ba\u6027\u3002<\/p>\n

\u5982\u679c\u60a8\u5c0d\u65bc\u5927\u6578\u64da\u8655\u7406\u548cHive\u7684\u4f7f\u7528\u6709\u8208\u8da3\uff0c\u4e26\u5e0c\u671b\u5c0b\u627e\u5408\u9069\u7684\u89e3\u6c7a\u65b9\u6848\uff0c\u60a8\u53ef\u4ee5\u8003\u616e\u6211\u5011\u7684\u9999\u6e2fVPS<\/a>\u670d\u52d9\uff0c\u70ba\u60a8\u7684\u6578\u64da\u5206\u6790\u63d0\u4f9b\u7a69\u5b9a\u7684\u652f\u6301\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"

\u4e86\u89e3Hive\u7d71\u8a08\u51fd\u6578count(*)\u70ba\u4f55\u4e0d\u4f7f\u7528MapReduce\uff0c\u63a2\u8a0e\u5176\u6027\u80fd\u512a\u52e2\u53ca\u80cc\u5f8c\u7684\u6280\u8853\u539f\u7406\u3002<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-170087","post","type-post","status-publish","format-standard","hentry","category-database"],"_links":{"self":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/170087","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"}],"replies":[{"embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/comments?post=170087"}],"version-history":[{"count":1,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/170087\/revisions"}],"predecessor-version":[{"id":170088,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/posts\/170087\/revisions\/170088"}],"wp:attachment":[{"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/media?parent=170087"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/categories?post=170087"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/server.hk\/cnblog\/wp-json\/wp\/v2\/tags?post=170087"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}