MAPREDUCE Flashcards
1
Q
What is mapreduce and hadoop mapreduce
A
mapreduce is a programming model for processing and generating large datasets.
hadoop mapreduce is an implementation of this model
2
Q
how does map reduce work
A
1)iterate over numerous records
2)extract data as key-value pair
3)aggregate results
4)save the results in hdfs
3
Q
what is combiner and how it works with map reduce
A
combiner is like a mini reducer works during map phase to pre-aggregate data when the function is associative and commutative.
it happens before shuffling and aggregating.
it reduces intermediate data and reduce network traffic.
4
Q
what is partitioning mapreduce
A
the partitioner directs map outputs to appropriate reducer by applying a function on that key.
