Arun Mahadevan created CALCITE-1434:
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Summary: AggregateFunctionImpl doesnt work if the class implements
a generic interface
Key: CALCITE-1434
URL: https://issues.apache.org/jira/browse/CALCITE-1434
Project: Calcite
Issue Type: Bug
Reporter: Arun Mahadevan
Assignee: Julian Hyde
We have an interface like below which we want to expose to users for writing
aggregate functions.
public interface UDAF<A, V, R> {
A init();
A add(A aggregate, V val);
R result(A aggregate);
}
Internally we create an instance of AggregateFunctionImpl and register the
Function in SchemaPlus. However this doesn't work for example if we have an
implementation like below,
public class MySum implements UDAF<Number, Number, Number> {
@Override
public Number init() {...}
@Override
public Number add(Number aggregate, Number val) {...}
@Override
public Number result(Number aggregate) {...}
}
We get an Exception "java.lang.RuntimeException: In user-defined aggregate
class 'x.y.z.$MySum', first parameter to 'add' method must be the accumulator
(the return type of the 'init' method)"
This happens because the ReflectiveFunctionBase.findMethod is trying to look
for a method name "init" and it get a method with a different signature (that
returns Object) instead of the actual method defined in MySum. This happens to
be a 'bridge' method inserted by java.
In findMethod, the bridge methods can be skipped while looking for the method
by name.
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