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Questions tagged [mapper]

The mapper is the first step in MapReduce framework, a component of a larger scalable, parallel-izable algorithm.

Maps input key/value pairs to a set of intermediate key/value pairs.

Maps are the individual tasks which transform input records into a intermediate records. The transformed intermediate records need not be of the same type as the input records. A given input pair may map to zero or many output pairs.

The most common map reduce framework is Apache Hadoop.

See also MapReduce Wiki.

653 questions
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Cannot resolve method on java object

I am trying out some new design patterns in java but I am getting confused as to why mine will not work. I am aiming to pass a user account into a data transfer object which can then be used to sign up a new user by checking if they exist or not and…
Oliver Darby
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Convert MutableList to MutableList
Actually I have this data class where data is a mutableList , data class DataTable ( var total: Long = 0, @JsonProperty("data") var data: MutableList? = null ) my idea is that when that data arrives I can map it to a very…
dasuma
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Java, Map same object to different objects

I have a list of Car's, I want to map them to different specific Car's like - FordCar, HondaCar, VolkswagenCar... base on value of maker attribute of Car, that is Car.maker Can Dozer, MapStruct do this? Or is there any framework in Java which can do…
CR Sardar
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generic mapper call another mapper

in old application i use seperate map for convert any model to view model and inverse. now i want use generic function but generic function not call sightly map public class GenericBll where TVModel : class where TMModel : class { …
Alireza Hejazi
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What is the correct way to perform multiple operations on a text file , but executing it as a SINGLE HADOOP JOB

I want to perform few operations on a single text file. For eg: Task 1: Count all the words Task 2: Count words ending with specific characters Task 3: Count words occuring multiple times. What is the best way of achieving this? Do I need to write…
TjS
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How to use mrjob.cat to auto-decompress inputs?

I want to use MrJob to analyze a dataset without decompressing it on disk beforehand (it is 18Gb compressed but >3Tb uncompressed). How can I use use mrjob.cat to auto-decompress the file and stream it to my mapper? There aren't any code samples.
crypdick
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Trying to print mapped data but function is returning nothing

import numpy as np with open("/Users/myname/Downloads/names/yob1880.txt","r") as f: text = f.readlines() for line in text: print (line) def mapper(): for lines in line: data = line.strip().split("\t") name, sex, number =…
Isabelle
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java.lang.Exception: java.lang.ClassCastException: org.apache.hadoop.io.Text cannot be cast to org.apache.hadoop.io.IntWritable

public class PrimeMapper extends Mapper { public void map(LongWritable k,IntWritable val,Context c) throws IOException, InterruptedException { int…
AcCesS DoOmeR
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How to write own model mapper in Swift Language

I have a requirement for mapping values coming from service layer to the UI key values. Let's say two values are coming from the service layer in array of dictionary { ["identifier": "1", "fullname": "Bob Steve"] } I have to modify the key…
Raghunath Sahoo
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How to map Data Table to "DTO" using Express Mapper

I am using ASP.NET Web API and C#. As i am new to Express Mapper and i am having ADO.NET code which is returning list of results.How to map using Express Mapper?
Sai Kumar
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Reducer Not Working or Never geting call

Driver class: import java.io.IOException; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.NullWritable; import org.apache.hadoop.io.Text; import…
Ash
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Hbase Error: java.lang.ClassCastException: org.apache.hadoop.io.Text cannot be cast to org.apache.hadoop.hbase.client.Mutation

I am getting following error while transferring values from one Hbase table to other Hbase table. The code is working fine while transferring from Hbase table to file output. Error: java.lang.ClassCastException: org.apache.hadoop.io.Text cannot be…
stonecrusher
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How to pass string as value in mapper?

I am trying to pass a string as value in the mapper, but getting error that it is not Writable. How to resolve? public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { String TempString =…
Raunak Tibrewal
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Dozer mapping result of a getter to filed in destination

I am using dozer to map my DTO objects from domain objects. How can map the result of a getter method from the domain object to a filed in the destination Object Class Domain{ public boolean getSomethig() { return somebooleanValue; …
kumar
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Accessing protected class in java

I have an object represented as follows: public final class FooFunc
frazman
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