{"id":2363,"date":"2017-04-29T11:02:45","date_gmt":"2017-04-29T11:02:45","guid":{"rendered":"http:\/\/data-flair.training\/blogs\/?p=2363"},"modified":"2018-11-20T15:01:30","modified_gmt":"2018-11-20T09:31:30","slug":"hadoop-outputformat","status":"publish","type":"post","link":"https:\/\/data-flair.training\/blogs\/hadoop-outputformat\/","title":{"rendered":"Hadoop Output Format – Types of Output Format in Mapreduce"},"content":{"rendered":"

1. Hadoop Output Format – Objective<\/h2>\n

The Hadoop\u00a0<\/a>Output Format checks the Output-Specification of the job. It determines how RecordWriter implementation is used to write output to output files. In this blog, we are going to see\u00a0what is Hadoop Output Format, what is Hadoop RecordWriter, how RecordWriter is used in Hadoop?<\/p>\n

In this Hadoop Reducer Output Format guide, will also discuss various types of Output Format in Hadoop like textOutputFormat, sequenceFileOutputFormat, mapFileOutputFormat, sequenceFileAsBinaryOutputFormat, DBOutputFormat, LazyOutputForma, and MultipleOutputs.<\/p>\n

Learn How to install Cloudera Hadoop CDH5 on CentOS<\/a><\/strong>.<\/p>\n

\"Hadoop<\/a>

Hadoop Output Format – Types of Output Format in Mapreduce<\/p><\/div>\n

2. What is Hadoop Output Format?<\/h2>\n

Before we start with Hadoop Output Format in MapReduce<\/a><\/strong>, let us first see what is a RecordWriter in MapReduce and what is its role in MapReduce?<\/p>\n

i. Hadoop RecordWriter<\/h3>\n

As we know, Reducer<\/a><\/strong> takes as input a set of an intermediate key-value pair<\/strong><\/a> produced by the mapper<\/a> <\/strong>and runs a reducer function on them to generate output that is again zero or more key-value pairs.<\/p>\n

RecordWriter writes these output key-value pairs from the Reducer phase to output files.<\/p>\n

Read: MapReduce Input Format<\/a><\/strong><\/p>\n

ii. Hadoop Output Format<\/h3>\n

As we saw above, Hadoop RecordWriter takes output data from Reducer and writes this data to output files. The way these output key-value pairs are written in output files by RecordWriter is determined by the Output Format. The Output Format and InputFormat <\/a><\/strong>functions are alike. OutputFormat instances provided by Hadoop are used to write to files on the\u00a0HDFS<\/strong><\/a> or local disk. OutputFormat describes the output-specification for a Map-Reduce job<\/strong><\/a>. On the basis of output specification;<\/p>\n