Hi Marco,
nesting aggregated functions is not allowed in SQL. The exception could
be improved though. I guess the planner searches for a scalar function
called `MyUDTAGG` in your example and cannot find one.
Maybe the built-in function `COLLECT` or `LISTAGG`is what you are
looking for?
https://ci.apache.org/projects/flink/flink-docs-release-1.12/dev/table/functions/systemFunctions.html
Regards,
Timo
On 05.01.21 14:45, Marco Villalobos wrote:
I am trying to use User defined Table Aggregate function directly in the SQL
so that I could combine all the rows collected in a window into one object.
GIVEN a User defined Table Aggregate function
public class MyUDTAGG extends
TableAggregateFunction<PurchaseWindow,PurchaseWindow> {
public PurchaseWindow createAccumulator() {
return new PurchaseWindow();
}
public void accumulate(PurchaseWindow acc, String name, double cost) {
acc.add(name, cost);
}
public void emitValue(PurchaseWindow acc, Collector<PurchaseWindow>
out) {
out.collect(acc);
}
}
THAT it is registered as
StreamTableEnvironment tEnv = ...
tEnv.registerFunction("MyUDTAGG", new MyUDTAGG());
THEN is it possible to call it in an SQL query in this manner?
SELECT MyUDTAGG(name, SUM(cost)) AS purchase_window
FROM purchases
GROUP BY TUMBLE(proactive, INTERVAL '1' DAY), name
I am receiving an SQL validation error, "No match found for function signature
...".
What am I doing wrong, or is there a better way to do this?
