开源大数据平台 E-MapReduce学习-阿里云

Hadoop学习：MapReduce实现WordCount经典案例一、✌题目要求> 统计文本中每个单词的数量二、✌实现思想> Map阶段默认输入为TextInputFormat，键值对对应为行的偏移量和每行的文本内容 > 在map函数中将每行文本进行切分，提取出每个单词 > 在Reduce阶段根据相同Key值进行累加求和 > 三、✌代...

Hadoop学习：MapReduce实现文件的解压缩一、✌实现思想压缩> 获取输入流 > 获取压缩相关信息（反射） > 获取输出流 > 流的对拷 > 关闭资源解压缩> 校验文件是否可以解压 > 获取输入流 > 获取输出流 > 流的对拷 > 关闭资源二、✌代码实现1.✌compress压缩方法...

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Hadoop学习：MapReduce实现倒排索引一、✌题目要求文件1：a.txt文件2：b.txt文件3：c.txt最终输出格式：二、✌实现思想> 首先在map阶段，获得每个单词所在的文件名称 > 然后在方法中，每个单词作为Key，所在文件名称+1作为Value > 在Reduce阶段，针对每个Key&#x...

Hadoop学习：MapReduce不使用Reduce将表合并提高效率一、✌题目要求record表：ID城市编号空气指数001032450020265500305743004042460050295600601637007058310080368300902349city表：城市编号城市名称01长沙02株洲03湘潭04怀化05岳阳目标表：ID城市名称空气指数001湘潭...

Hadoop学习：MapReduce实现两张表合并一、✌题目要求record表：ID城市编号空气指数001032450020265500305743004042460050295600601637007058310080368300902349city表：城市编号城市名称01长沙02株洲03湘潭04怀化05岳阳目标表：ID城市名称空气指数001湘潭...

Hadoop MapReduce 保姆级吐血宝典，学习与面试必读此文！（三） 8. Map端实现 JOIN8.1 概述适用于关联表中有小表的情形.使用分布式缓存,可以将小表分发到所有的map节点，这样，map节点就可以在本地对自己所读到的大表数据进行join并输出最终结果，可以大大提高join操作的并发度，加快处理速度8.2 实现步骤先在mapper类中预先定义好小表，进行j...

Hadoop MapReduce 保姆级吐血宝典，学习与面试必读此文！（二） 6. MapReduce的运行机制详解6.1 MapTask 工作机制整个Map阶段流程大体如上图所示。简单概述：inputFile通过split被逻辑切分为多个split文件，通过Record按行读取内容给map（用户自己实现的）进行处理，数据被map处理结束之后交给OutputCollector...

Hadoop MapReduce 保姆级吐血宝典，学习与面试必读此文！（一） Hadoop 涉及的知识点如下图所示，本文将逐一讲解：本文档参考了关于 Hadoop 的官网及其他众多资料整理而成，为了整洁的排版及舒适的阅读，对于模糊不清晰的图片及黑白图片进行重新绘制成了高清彩图。目前企业应用较多的是Hadoop2.x，所以本文是以Hadoop2.x为主，对于Hadoop3.x新...

案例学习：MapReduce 案例学习：MapReduce

Hadoop学习(4)-mapreduce的一些注意事项 Hadoop学习(4)-mapreduce的一些注意事项

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开源大数据平台 E-MapReduce

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