Although Hive has provided many built-in functions, in special use cases, users may need power beyond what's provided. In this case, we can extend Hive's functionality in three main areas:

• User-defined function (UDF): This provides a way to extend functionalities with an external function (mainly written in Java) that can be evaluated in HQL
• HPL/SQL: This provides procedure-language-programming support to HQL
• Streaming: This plugs a user's own customized programs in to the data streaming
• SerDe: This stands for serialization and deserialization and provides a way to serialize or deserialize data with the customized file format

In this chapter, we'll talk about each of them in more detail.