User-defined functions

In modern data processing and analysis, SQL language is a powerful tool for handling structured data. However, as the complexity of data analysis increases, standard SQL statements and built-in functions may not be sufficient to meet all data processing needs. This is where user-defined functions (UDFs) come into play, allowing you to define custom functions to achieve more complex calculations and operations.

When do you need UDFs

UDFs are crucial when there is a need to perform calculations that cannot be supported by standard SQL functions. Here are some typical scenarios and examples:

• Complex mathematical or statistical calculations, such as calculating the greatest common divisor of two numbers.
• Custom data transformations or validations, such as extracting information from network packets.
• Need to use external services or resources, such as accessing OpenAI API to generate text.
• Migration from existing systems, such as migrating Flink UDFs and implementing functions not currently supported by RisingWave.

It is important to note that UDFs have lower execution efficiency compared to built-in functions due to cross-language communication and data conversion. Therefore, users should always prioritize the use of built-in functions.

Types of UDFs in RisingWave

At present, there are three ways to define your UDF. The first option is to use it as an external function, which runs as a standalone service and provides maximum flexibility. The second option is to use an embedded UDF, which runs internally in RisingWave. The third is to use a SQL UDF, which allows for the same capabilities as regular SQL while offering a more concise way to express complex queries.

Beta feature

UDF is currently in Beta. Please contact us if you encounter any issues or have feedback.

UDFs as external functions

RisingWave supports creating UDFs with the following programming languages:

• Python

• Java

Embedded UDFs

• Python

• JavaScript

• Rust

SQL UDFs

For details about how to create a SQL UDF and its use cases, see:

• CREATE FUNCTION

See also

You may also use UDFs to query data stored in different databases

• Query foreign data