Which primary language is commonly used for writing User Defined Functions (UDFs) in Databricks?

In Databricks, Python is the primary language used for writing User Defined Functions (UDFs). This choice is driven by Python's popularity and versatility in data processing and analysis, making it an ideal choice for data engineers and data scientists working within the platform.

Python UDFs allow users to encapsulate complex logic into reusable functions that can be applied to data frames and other data structures, enhancing the flexibility and functionality of Spark SQL queries. Additionally, the rich libraries available in Python for data manipulation, machine learning, and analytics significantly bolster the capabilities of UDFs.

While other languages like JavaScript, Ruby, and SQL may be available or suitable in certain contexts, they do not offer the same level of integration and support within the Databricks environment for functions that need extensive computational abilities or data transformations that Python provides.