“`” \u89e3\u7b54\uff1a<\/p>\n
\u4e00\u4e2aMapReduce\u4f5c\u4e1a\u7531Map\u9636\u6bb5\u548cReduce\u9636\u6bb5\u4e24\u90e8\u5206\u7ec4\u6210\uff0c\u8fd9\u4e24\u9636\u6bb5\u4f1a\u5bf9\u6570\u636e\u6392\u5e8f\uff0c\u4ece\u8fd9\u4e2a\u610f\u4e49\u4e0a\u8bf4\uff0cMapReduce\u6846\u67b6\u672c\u8d28\u5c31\u662f\u4e00\u4e2aDistributed Sort\u3002\u5728Map\u9636\u6bb5\uff0c\u5728Map\u9636\u6bb5\uff0cMap Task\u4f1a\u5728\u672c\u5730\u78c1\u76d8\u8f93\u51fa\u4e00\u4e2a\u6309\u7167key\u6392\u5e8f\uff08\u91c7\u7528\u7684\u662f\u5feb\u901f\u6392\u5e8f\uff09\u7684\u6587\u4ef6\uff08\u4e2d\u95f4\u53ef\u80fd\u4ea7\u751f\u591a\u4e2a\u6587\u4ef6\uff0c\u4f46\u6700\u7ec8\u4f1a\u5408\u5e76\u6210\u4e00\u4e2a\uff09\uff0c\u5728Reduce\u9636\u6bb5\uff0c\u6bcf\u4e2aReduce Task\u4f1a\u5bf9\u6536\u5230\u7684\u6570\u636e\u6392\u5e8f\uff0c\u8fd9\u6837\uff0c\u6570\u636e\u4fbf\u6309\u7167Key\u5206\u6210\u4e86\u82e5\u5e72\u7ec4\uff0c\u4e4b\u540e\u4ee5\u7ec4\u4e3a\u5355\u4f4d\u4ea4\u7ed9reduce\uff08\uff09\u5904\u7406\u3002\u5f88\u591a\u4eba\u7684\u8bef\u89e3\u5728Map\u9636\u6bb5\uff0c\u5982\u679c\u4e0d\u4f7f\u7528Combiner\u4fbf\u4e0d\u4f1a\u6392\u5e8f\uff0c\u8fd9\u662f\u9519\u8bef\u7684\uff0c\u4e0d\u7ba1\u4f60\u7528\u4e0d\u7528Combiner\uff0cMap Task\u5747\u4f1a\u5bf9\u4ea7\u751f\u7684\u6570\u636e\u6392\u5e8f\uff08\u5982\u679c\u6ca1\u6709Reduce Task\uff0c\u5219\u4e0d\u4f1a\u6392\u5e8f\uff0c \u5b9e\u9645\u4e0aMap\u9636\u6bb5\u7684\u6392\u5e8f\u5c31\u662f\u4e3a\u4e86\u51cf\u8f7bReduce\u7aef\u6392\u5e8f\u8d1f\u8f7d\uff09\u3002\u7531\u4e8e\u8fd9\u4e9b\u6392\u5e8f\u662fMapReduce\u81ea\u52a8\u5b8c\u6210\u7684\uff0c\u7528\u6237\u65e0\u6cd5\u63a7\u5236\uff0c\u56e0\u6b64\uff0c\u5728hadoop 1.x\u4e2d\u65e0\u6cd5\u907f\u514d\uff0c\u4e5f\u4e0d\u53ef\u4ee5\u5173\u95ed\uff0c\u4f46hadoop2.x\u662f\u53ef\u4ee5\u5173\u95ed\u7684\u3002<\/p>\n
1\u3001combiner\u6700\u57fa\u672c\u662f\u5b9e\u73b0\u672c\u5730key\u7684\u805a\u5408\uff0c\u5bf9map\u8f93\u51fa\u7684key\u6392\u5e8f\uff0cvalue\u8fdb\u884c\u8fed\u4ee3\u3002\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n
\u3000\u3000map: (K1, V1) \u2192 list(K2, V2)<\/p>\n
\u3000\u3000combine: (K2, list(V2)) \u2192 list(K2, V2)<\/p>\n
\u3000\u3000reduce: (K2, list(V2)) \u2192 list(K3, V3)<\/p>\n
2\u3001combiner\u8fd8\u5177\u6709\u7c7b\u4f3c\u672c\u5730\u7684reduce\u529f\u80fd.<\/p>\n
\u3000\u3000\u4f8b\u5982hadoop\u81ea\u5e26\u7684wordcount\u7684\u4f8b\u5b50\u548c\u627e\u51favalue\u7684\u6700\u5927\u503c\u7684\u7a0b\u5e8f\uff0ccombiner\u548creduce\u5b8c\u5168\u4e00\u81f4\u3002\u5982\u4e0b\u6240\u793a\uff1a<\/p>\n
\u3000\u3000map: (K1, V1) \u2192 list(K2, V2)<\/p>\n
\u3000\u3000combine: (K2, list(V2)) \u2192 list(K3, V3)<\/p>\n
\u3000\u3000reduce: (K3, list(V3)) \u2192 list(K4, V4)<\/p>\n
3\u3001\u5982\u679c\u4e0d\u7528combiner\uff0c\u90a3\u4e48\uff0c\u6240\u6709\u7684\u7ed3\u679c\u90fd\u662freduce\u5b8c\u6210\uff0c\u6548\u7387\u4f1a\u76f8\u5bf9\u4f4e\u4e0b\u3002\u4f7f\u7528combiner\uff0c\u5148\u5b8c\u6210\u7684map\u4f1a\u5728\u672c\u5730\u805a\u5408\uff0c\u63d0\u5347\u901f\u5ea6\u3002<\/p>\n
4\u3001\u5bf9\u4e8ehadoop\u81ea\u5e26\u7684wordcount\u7684\u4f8b\u5b50\uff0cvalue\u5c31\u662f\u4e00\u4e2a\u53e0\u52a0\u7684\u6570\u5b57\uff0c\u6240\u4ee5map\u4e00\u7ed3\u675f\u5c31\u53ef\u4ee5\u8fdb\u884creduce\u7684value\u53e0\u52a0\uff0c\u800c\u4e0d\u5fc5\u8981\u7b49\u5230\u6240\u6709\u7684map\u7ed3\u675f\u518d\u53bb\u8fdb\u884creduce\u7684value\u53e0\u52a0\u3002<\/p>\n
\u3000\u3000combiner\u4f7f\u7528\u7684\u5408\u9002\uff0c\u53ef\u4ee5\u5728\u6ee1\u8db3\u4e1a\u52a1\u7684\u60c5\u51b5\u4e0b\u63d0\u5347job\u7684\u901f\u5ea6\uff0c\u5982\u679c\u4e0d\u5408\u9002\uff0c\u5219\u5c06\u5bfc\u81f4\u8f93\u51fa\u7684\u7ed3\u679c\u4e0d\u6b63\u786e\u3002<\/p>\n
<pre><code> "“`
\n<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"
“`” \u89e3\u7b54\uff1a \u4e00\u4e2aMapReduce\u4f5c\u4e1a\u7531Map\u9636\u6bb5\u548cReduce\u9636\u6bb5\u4e24\u90e8\u5206\u7ec4\u6210\uff0c\u8fd9 […]<\/p>\n","protected":false},"author":7,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[101],"tags":[],"class_list":["post-47649","post","type-post","status-publish","format-standard","hentry","category-c"],"_links":{"self":[{"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/posts\/47649","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/comments?post=47649"}],"version-history":[{"count":1,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/posts\/47649\/revisions"}],"predecessor-version":[{"id":47650,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/posts\/47649\/revisions\/47650"}],"wp:attachment":[{"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/media?parent=47649"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/categories?post=47649"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/tags?post=47649"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}