What is considered the most resource-heavy aggregation?

The aggregation that is considered the most resource-heavy is Count distinct. This is due to the complexity involved in calculating the unique values in a data set. Unlike simple aggregations such as Sum, Count, or Average, which can be computed with straightforward arithmetic operations, Count distinct requires the application of additional logic to identify and ensure that only unique entries are considered in the final result.

The process involves maintaining a list of processed values and checking for duplicates, which can significantly increase the computational load, especially when dealing with large data sets. This additional overhead makes Count distinct a more resource-intensive operation compared to the others mentioned.

In contrast, aggregations like Sum, Count, and Average can be performed with less resource demand as they either involve straightforward counting or arithmetic calculations that do not require tracking individual distinct values.