A Writable for arrays containing instances of a class. The elements of this writable must all be instances of the same class.
Table of Contents
What is Arraywritable?
A Writable for arrays containing instances of a class. The elements of this writable must all be instances of the same class.
What is writable collection in Hadoop?
Interface Writable A serializable object which implements a simple, efficient, serialization protocol, based on DataInput and DataOutput . Any key or value type in the Hadoop Map-Reduce framework implements this interface.
What are six writable collection types?
Writable collections There are six Writable collection types in the org.apache.hadoop.io package: Array Writable, ArrayPrimitiveWritable, TwoDArrayWritable, MapWritable, SortedMapWritable, and EnumSetWritable.
What are writable comparable and comparators?
A Writable which is also Comparable . WritableComparable s can be compared to each other, typically via Comparator s. Any type which is to be used as a key in the Hadoop Map-Reduce framework should implement this interface. Note that hashCode() is frequently used in Hadoop to partition keys.
What is writable interface and writable class in Hadoop?
What is writable comparable in big data?
What are object writable and generic writable?
Compared with ObjectWritable , this class is much more effective, because ObjectWritable will append the class declaration as a String into the output file in every Key-Value pair. Generic Writable implements Configurable interface, so that it will be configured by the framework.
What is difference between writable comparable and comparators?
1) Comparable provides a single sorting sequence. In other words, we can sort the collection on the basis of a single element such as id, name, and price. The Comparator provides multiple sorting sequences. In other words, we can sort the collection on the basis of multiple elements such as id, name, and price etc.
What are the two types of writable data?
Define Writable data types in Hadoop MapReduce.
- Integer –> IntWritable: It is the Hadoop variant of Integer.
- Float –> FloatWritable: Hadoop variant of Float used to pass floating point numbers as key or value.
- Long –> LongWritable: Hadoop variant of Long data type to store long values.
When you implement a custom writable you must also define which of these objects?
Implementing Writable requires implementing two methods, readFields(DataInput in) and write(DataOutput out) . Writables that are used as keys in MapReduce jobs must also implement Comparable (or simply WritableComparable).
What is the difference between comparable and Comparator in Java with example?
Comparable in Java is an object to compare itself with another object, whereas Comparator is an object for comparing different objects of different classes. Comparable provides compareTo() method to sort elements in Java whereas Comparator provides compare() method to sort elements in Java.
How is custom writable implemented in hadoop?
Creating Custom Hadoop Writable Data Type 11
- Creating Mapper Class With Custom Data Types.
- Creating Reducer Class With Custom Data Types.
- Creating Mapreduce driver Class With Custom Data Types.
- Run WebLogReader.java program.
- Validate the results.