Recursive Aggregators

If the operation in your is associative (\_property\) then you should mark your aggregator with an attribute to indicate that the UDAgg is "recursive" (a.k.a "associative" ). This will improve the performance substantially of your U-SQL script has to aggregate a lot of data with your UDAgg because the UDAgg can be parallelized.

The snippet below shows how to do this.

[SqlUserDefinedReducer(IsRecursive = true)]
public class MySum : IAggregate<int, long>
// your code here

Do not just blindly add the IsRecursive property to your UDAggs. Make sure the UDAggs support the associative property.

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