Apache Hive Essentials

SerDe

SerDe stands for Serializer and Deserializer. It is the technology that Hive uses to process records and map them to column data types in Hive tables. To explain the scenario of using SerDe, we need to understand how Hive reads and writes data.

The process to read data is as follows:

1. Data is read from HDFS.
2. Data is processed by the INPUTFORMAT implementation, which defines the input data split and key/value records. In Hive, we can use CREATE TABLE ... STORED AS <FILE_FORMAT> (see Chapter 7, Performance Considerations, for available file formats) to specify which INPUTFORMAT it reads from.
3. The Java Deserializer class defined in SerDe is called to format the data into a record that maps to column and data types in a table.

For an example of reading ...