What is writable comparable?
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.
What is writable data?
Writable data types are meant for writing the data to the local disk and it is a serialization format. Just like in Java there are data types to store variables (int, float, long, double,etc.), Hadoop has its own equivalent data types called Writable data types.
What is the writable interface explain in details?
Overview. Writable is interface mechanism to serialise and de-serialise your data. It is an interface which has write method and read fields method. * Write field is to writing your data into the output stream or network. * Read field is to read data from the input stream.
What are writable wrappers for Java primitives?
Primitive Writable Classes
These are Writable Wrappers for Java primitive data types and they hold a single primitive value that can be set either at construction or via a setter method. All these primitive writable wrappers have get() and set() methods to read or write the wrapped value.
What is writable Hadoop?
Writable is an interface in Hadoop. Writable in Hadoop acts as a wrapper class to almost all the primitive data type of Java. That is how int of java has become IntWritable in Hadoop and String of Java has become Text in Hadoop. Writables are used for creating serialized data types in Hadoop.
What is difference between writable comparable and writable comparator?
In short, the type used as key in Hadoop must be a WritableComparable , while the type only used as value could be just a Writable . A Writable which is also Comparable. WritableComparables can be compared to each other, typically via Comparators.
What is MapReduce technique?
MapReduce is a programming model or pattern within the Hadoop framework that is used to access big data stored in the Hadoop File System (HDFS). … MapReduce facilitates concurrent processing by splitting petabytes of data into smaller chunks, and processing them in parallel on Hadoop commodity servers.
What are six writable collection types?
There are six Writable collection types in the org.apache.hadoop.io package: Array Writable, ArrayPrimitiveWritable, TwoDArrayWritable, MapWritable, SortedMapWritable, and EnumSetWritable.
What is null writable in Hadoop?
I see the following from the «Hadoop: The Definitive Guide» book. NullWritable is a special type of Writable , as it has a zero-length serialization. No bytes are written to, or read from, the stream.
What is writable comparable interface?
WritableComparable interface is just a sub interface of the Writable and java.lang.Comparable interfaces. For implementing a WritableComparable we must have compareTo method apart from readFields and write methods, as shown below: public interface WritableComparable extends Writable, Comparable.
What is HBase in Hadoop?
HBase is a column-oriented non-relational database management system that runs on top of Hadoop Distributed File System (HDFS). HBase provides a fault-tolerant way of storing sparse data sets, which are common in many big data use cases. … HBase does support writing applications in Apache Avro, REST and Thrift.
What is the difference between Apache Pig and MapReduce?
Pig is an open-source tool that is built on the Hadoop ecosystem for providing better processing of Big data. It is a high-level scripting language that is commonly known as Pig Latin scripts.
Difference between MapReduce and Pig:
|1.||It is a Data Processing Language.||It is a Data Flow Language.|
Is byte a wrapper class?
The Byte , Short , Integer , Long , Float , and Double wrapper classes are all subclasses of the Number class. The wrapper classes BigDecimal and BigInteger are not one of the primitive wrapper classes but are immutable.
What is boxing and unboxing in Java?
Autoboxing is the automatic conversion that the Java compiler makes between the primitive types and their corresponding object wrapper classes. For example, converting an int to an Integer, a double to a Double, and so on. If the conversion goes the other way, this is called unboxing.
Is string a wrapper class in Java?
No. String is not a wrapper class, simply because there is no parallel primitive type that it wraps. A string is a representation of a char sequence but not necessarily a ‘wrapper’.