@Override
    public ComplexEventChunk<StateEvent> tryUpdate(ComplexEventChunk<StateEvent> updatingOrAddingEventChunk,
                                                   Object storeEvents,
                                                   InMemoryCompiledUpdateSet compiledUpdateSet,
                                                   AddingStreamEventExtractor addingStreamEventExtractor) {
        ComplexEventChunk<StateEvent> failedEventChunk = new ComplexEventChunk<>();
        updatingOrAddingEventChunk.reset();
        while (updatingOrAddingEventChunk.hasNext()) {
            StateEvent overwritingOrAddingEvent = updatingOrAddingEventChunk.next();
            StreamEvent streamEvents = collectionExecutor.find(overwritingOrAddingEvent, (IndexedEventHolder)
                    storeEvents, null);
            ComplexEventChunk<StreamEvent> foundEventChunk = new ComplexEventChunk<>();
            foundEventChunk.add(streamEvents);
            if (foundEventChunk.getFirst() != null) {
                //for cases when indexed attribute is also updated but that not changed
                //to reduce number of passes needed to update the events
                update((IndexedEventHolder) storeEvents, compiledUpdateSet, overwritingOrAddingEvent,
                        foundEventChunk);
            } else {
                updatingOrAddingEventChunk.remove();
                failedEventChunk.add(overwritingOrAddingEvent);
            }
        }
        return failedEventChunk;
    }
Operator which is related to non-indexed In-memory table operations.
modules/siddhi-core/src/main/java/io/siddhi/core/util/collection/operator/IndexOperator.java