User-Defined Extensions and User-Defined Functions

User-Defined Extension (UDx) refers to all extensions to Vertica developed using the APIs in the Vertica SDK. UDxs encompass functions such as User-Defined Scalar Functions (UDSFs), and utilities such as the User-Defined Load (UDL) feature that let you create custom data load routines.

Thanks to their tight integration with Vertica, UDxs usually have better performance than User-defined SQL functions or External Procedures.

User-Defined Functions (UDFs) are a specific type of UDx. You use them in SQL statements to process data similarly to Vertica's own built-in functions. They give you the power of creating your own functions that run just slightly slower than Vertica's own function.

The Vertica SDK uses the term UDx extensively, even for APIs that deal exclusively with developing UDFs.