How to process all items in List then complete with RxJava - rx-java2

Question

I am investigating the use of RxJava in my current Android application.
I am stuck with the following use case.
For each data row on a particular database table I wish to action an HTTP POST call, once all the POST(s) have completed OK I need to clear down the database table.
The code I have is as follows:-
login()
.andThen(Single.defer(() -> DatabaseController.fetchSingleRealmObjects(UpdateDO.class)))
.toObservable()
.flatMapIterable(update -> update)
.flatMap(this::parameteriseUpdate)
.doOnNext(NetworkController::update)
.doOnComplete(() -> DatabaseController.deleteAll(UpdateDO.class))
.ignoreElements()
.retryWhen(errors -> errors.flatMap(e -> constructRetryHandler(retryCounter, e)))
.doOnComplete(onComplete)
.doOnError(onError)
.doAfterTerminate(doAfterTerminate())
.doOnSubscribe(compositeDisposable::add)
.blockingAwait();
When the UpdateDO table is empty the above code completes as expected.
However when data rows exist the process "sticks" in the doOnNext()
I realise this is because I only call emitter.onNext()
private ObservableSource<Map<String, Object>> parameteriseUpdate(final UpdateDO updateDO) {
final Map<String, Object> fields = new HashMap<>();
fields.put(FIELD_NAME_DRUG_ID, updateDO.getDrugId());
fields.put(FIELD_NAME_STORE_CONTENT_ID, updateDO.getStoreContentId());
fields.put(FIELD_NAME_STORE_ID, updateDO.getStoreID());
fields.put(FIELD_NAME_ACTUAL_QUANTITY, updateDO.getActualQty());
fields.put(FIELD_NAME_VARIANCE, updateDO.getUnitQty());
fields.put(FIELD_NAME_REMARKS, updateDO.getRemarks());
fields.put(FIELD_NAME_CREATED_BY, updateDO.getCreatedBy());
return Observable.create(emitter -> emitter.onNext(fields));
}
I cannot see how to fix this though, how to I refactor my code to allow me to have emitter.onComplete() called?

Answer 1

I think that is better to change that function from returning ObservableSource<Map<String, Object>>
to simple function like this
private Map<String, Object> parameteriseUpdate(final UpdateDO updateDO) {
final Map<String, Object> fields = new HashMap<>();
fields.put(FIELD_NAME_DRUG_ID, updateDO.getDrugId());
fields.put(FIELD_NAME_STORE_CONTENT_ID, updateDO.getStoreContentId());
fields.put(FIELD_NAME_STORE_ID, updateDO.getStoreID());
fields.put(FIELD_NAME_ACTUAL_QUANTITY, updateDO.getActualQty());
fields.put(FIELD_NAME_VARIANCE, updateDO.getUnitQty());
fields.put(FIELD_NAME_REMARKS, updateDO.getRemarks());
fields.put(FIELD_NAME_CREATED_BY, updateDO.getCreatedBy());
return fields;
}
and call it as a map not flatmap like this :
.map(this::parameteriseUpdate)
because in your case you are creating many streams that never complete.