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1.x: optimize merge/flatMap for empty sources #3761

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May 2, 2016
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13 changes: 13 additions & 0 deletions src/main/java/rx/internal/operators/OperatorMerge.java
Original file line number Diff line number Diff line change
Expand Up @@ -237,6 +237,9 @@ public void onNext(Observable<? extends T> t) {
if (t == null) {
return;
}
if (t == Observable.empty()) {
emitEmpty();
} else
if (t instanceof ScalarSynchronousObservable) {
tryEmit(((ScalarSynchronousObservable<? extends T>)t).get());
} else {
Expand All @@ -247,6 +250,16 @@ public void onNext(Observable<? extends T> t) {
}
}

void emitEmpty() {
int produced = scalarEmissionCount + 1;
if (produced == scalarEmissionLimit) {
scalarEmissionCount = 0;
this.requestMore(produced);
} else {
scalarEmissionCount = produced;
}
}

private void reportError() {
List<Throwable> list = new ArrayList<Throwable>(errors);
if (list.size() == 1) {
Expand Down
106 changes: 106 additions & 0 deletions src/test/java/rx/internal/operators/OperatorFlatMapTest.java
Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,7 @@
import rx.Observer;
import rx.exceptions.TestException;
import rx.functions.*;
import rx.internal.util.RxRingBuffer;
import rx.observers.TestSubscriber;
import rx.schedulers.Schedulers;

Expand Down Expand Up @@ -544,4 +545,109 @@ public Observable<Integer> call(Integer t) {
ts.assertValueCount(n * 2);
}
}

@Test
public void justEmptyMixture() {
TestSubscriber<Integer> ts = TestSubscriber.create();

Observable.range(0, 4 * RxRingBuffer.SIZE)
.flatMap(new Func1<Integer, Observable<Integer>>() {
@Override
public Observable<Integer> call(Integer v) {
return (v & 1) == 0 ? Observable.<Integer>empty() : Observable.just(v);
}
})
.subscribe(ts);

ts.assertValueCount(2 * RxRingBuffer.SIZE);
ts.assertNoErrors();
ts.assertCompleted();

int j = 1;
for (Integer v : ts.getOnNextEvents()) {
Assert.assertEquals(j, v.intValue());

j += 2;
}
}

@Test
public void rangeEmptyMixture() {
TestSubscriber<Integer> ts = TestSubscriber.create();

Observable.range(0, 4 * RxRingBuffer.SIZE)
.flatMap(new Func1<Integer, Observable<Integer>>() {
@Override
public Observable<Integer> call(Integer v) {
return (v & 1) == 0 ? Observable.<Integer>empty() : Observable.range(v, 2);
}
})
.subscribe(ts);

ts.assertValueCount(4 * RxRingBuffer.SIZE);
ts.assertNoErrors();
ts.assertCompleted();

int j = 1;
List<Integer> list = ts.getOnNextEvents();
for (int i = 0; i < list.size(); i += 2) {
Assert.assertEquals(j, list.get(i).intValue());
Assert.assertEquals(j + 1, list.get(i + 1).intValue());

j += 2;
}
}

@Test
public void justEmptyMixtureMaxConcurrent() {
TestSubscriber<Integer> ts = TestSubscriber.create();

Observable.range(0, 4 * RxRingBuffer.SIZE)
.flatMap(new Func1<Integer, Observable<Integer>>() {
@Override
public Observable<Integer> call(Integer v) {
return (v & 1) == 0 ? Observable.<Integer>empty() : Observable.just(v);
}
}, 16)
.subscribe(ts);

ts.assertValueCount(2 * RxRingBuffer.SIZE);
ts.assertNoErrors();
ts.assertCompleted();

int j = 1;
for (Integer v : ts.getOnNextEvents()) {
Assert.assertEquals(j, v.intValue());

j += 2;
}
}

@Test
public void rangeEmptyMixtureMaxConcurrent() {
TestSubscriber<Integer> ts = TestSubscriber.create();

Observable.range(0, 4 * RxRingBuffer.SIZE)
.flatMap(new Func1<Integer, Observable<Integer>>() {
@Override
public Observable<Integer> call(Integer v) {
return (v & 1) == 0 ? Observable.<Integer>empty() : Observable.range(v, 2);
}
}, 16)
.subscribe(ts);

ts.assertValueCount(4 * RxRingBuffer.SIZE);
ts.assertNoErrors();
ts.assertCompleted();

int j = 1;
List<Integer> list = ts.getOnNextEvents();
for (int i = 0; i < list.size(); i += 2) {
Assert.assertEquals(j, list.get(i).intValue());
Assert.assertEquals(j + 1, list.get(i + 1).intValue());

j += 2;
}
}

}