introduction to hadoop pdf

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Introduction to the Hadoop MapReduce Programming API series Statistics student score 1 (17)

(args[1]));//Output path Job.setmapperclass (Scoremapper.class);//MapperJob.setreducerclass (Scorereducer.class);//Reducer Job.setmapoutputkeyclass (Text.class);//Mapper key Output typeJob.setmapoutputvalueclass (Scorewritable.class);//Mapper value Output type Job.setinputformatclass (Scoreinputformat.class);//Set Custom input formats Job.waitforcompletion (TRUE);return 0;} public static void Main (string[] args) throws Exception{string[] Args0 =// {"Hdfs://hadoopmaster:9000/score/score.txt","H

Introduction to Hadoop

1. Hadoop Core Project: HDFS (Distributed File System) and MapReduce (Parallel computing framework)2, the structure of HDFSMaster-Slave structureMaster node, only one: Namenode (accept user action requirements; Maintain the directory structure of the file system; Manage the relationship between the file and the block, the relationship between Block and Datanode)From the node, there are many: Datanodes (storing files; files are partitioned into blocks

Introduction to the Hadoop MapReduce Programming API series Statistics student score 2 (18)

= Mypath.getfilesystem (conf);if (Hdfs.isdirectory (MyPath)){Hdfs.delete (MyPath, true);}@SuppressWarnings ("deprecation")Job Job = new Job (conf, "gender");//Create a new taskJob.setjarbyclass (Gender.class);//Main classJob.setmapperclass (pcmapper.class);//mapperJob.setreducerclass (pcreducer.class);//reducerJob.setpartitionerclass (Myhashpartitioner.class);Job.setpartitionerclass (Pcpartitioner.class);//Set Partitioner classJob.setnumreducetasks (3);//reduce number set to 3Job.setmapoutputke

Introduction to the Hive for Hadoop notes (architecture of Hive)

table(dbms_xplan.display):Perform a full table scan, of course the cost of a full table scan is relatively highThe department number is indexed belowindexon emp(deptno):索引已创建。forselectfromwhere deptno=10:已解释。selectfrom table(dbms_xplan.display):It's an index-based scan that's faster for full-table scanning.It's almost like Oracle for Hive.So:0hadoop Use HDFS for storage and compute with MapReduce 0 Meta Data storage (Metastore) Typically stored in a relational database su

Bloomfilter Introduction and application in the Hadoop reduce side join __hadoop

Introduction to Bloomfilter and its application in the Hadoop reduce side join1, Bloomfilter can solve what problem? A small amount of memory space to determine whether an element belongs to this set, at the cost of a certain error rate 2. Working principle 1. Initialize an array with all the bits labeled 0, a={x1, x2, x3,..., XM} (x1, x2, x3,..., XM initially 0) 2. Each of the arrays in the known set S i

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