@Override
    public void delete(ComplexEventChunk<StateEvent> deletingEventChunk, Object storeEvents) {
        if (((Collection<StreamEvent>) storeEvents).size() > 0) {
            deletingEventChunk.reset();
            while (deletingEventChunk.hasNext()) {
                StateEvent deletingEvent = deletingEventChunk.next();
                try {
                    for (Iterator<StreamEvent> iterator = ((Collection<StreamEvent>) storeEvents).iterator();
                         iterator.hasNext(); ) {
                        StreamEvent storeEvent = iterator.next();
                        deletingEvent.setEvent(storeEventPosition, storeEvent);
                        if ((Boolean) expressionExecutor.execute(deletingEvent)) {
                            iterator.remove();
                        }
                    }
                } finally {
                    deletingEvent.setEvent(storeEventPosition, null);
                }
            }
        }
    }
Operator which is related to non-indexed In-memory table operations.
modules/siddhi-core/src/main/java/io/siddhi/core/util/collection/operator/CollectionOperator.java