얼마나 많은 매퍼 클래스 인스턴스가 생성됩니까?

Question

MaaTemperatureMapper라는 Mapper 클래스가 있고 100 개의 레코드가있는 파일로 TextInputFormat 클래스를 입력 할 때. IS 입력 분할 수와 동일한 수의 생성 된 매퍼 인스턴스 수 또는 입력의 각 키 값 쌍에 대해 생성 된 새 매퍼입니다.

Answer 1

Number of mapper would be equal to number of input splits . 

when ever you submit a job ,first of all it determines number of splits ,splits are logical . 

usually one split size is equal to hdfs block size but that can also be configured where your split size could be less than or greater than block size . for efficent processing usually one split size is equal to block size . 

suppose you have file of 1 GB ,your default block size is 128 mb so approximately you will have 8 blocks and 8 input splits would be required and hence 8 mappers would be invoked for this process .