private void sendTimerEvent(ExecutorState executorState) {
        if (getNextExecutor() != null) {
            StreamEvent timerEvent = streamEventFactory.newInstance();
            timerEvent.setType(ComplexEvent.Type.TIMER);
            timerEvent.setTimestamp(executorState.startTimeOfAggregates);
            ComplexEventChunk<StreamEvent> timerStreamEventChunk = new ComplexEventChunk<>();
            timerStreamEventChunk.add(timerEvent);
            next.execute(timerStreamEventChunk);
        }
    }
Incremental executor class which is responsible for performing incremental aggregation.
modules/siddhi-core/src/main/java/io/siddhi/core/aggregation/IncrementalExecutor.java