gianm commented on code in PR #15007:
URL: https://github.com/apache/druid/pull/15007#discussion_r1341563571
##########
extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/exec/WorkerImpl.java:
##########
@@ -1152,7 +1152,7 @@ private void makeShuffleOutputChannelFactory(boolean
isFinalStage)
);
}
- private <FactoryType extends FrameProcessorFactory<I, WorkerClass, T, R>,
I, WorkerClass extends FrameProcessor<T>, T, R> void makeAndRunWorkProcessors()
+ private <FactoryType extends FrameProcessorFactory<T, R, I>, T, R, I> void
makeAndRunWorkProcessors()
Review Comment:
I updated the names to be clearer and added javadoc.
##########
extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/querykit/ChainedProcessorManager.java:
##########
@@ -0,0 +1,104 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.druid.msq.querykit;
+
+import com.google.common.base.Preconditions;
+import com.google.common.util.concurrent.Futures;
+import com.google.common.util.concurrent.ListenableFuture;
+import com.google.common.util.concurrent.SettableFuture;
+import org.apache.druid.common.guava.FutureUtils;
+import org.apache.druid.frame.processor.FrameProcessor;
+import org.apache.druid.frame.processor.manager.ProcessorAndCallback;
+import org.apache.druid.frame.processor.manager.ProcessorManager;
+import org.apache.druid.utils.CloseableUtils;
+
+import javax.annotation.Nullable;
+import java.util.Optional;
+import java.util.function.Function;
+
+/**
+ * Manager that chains processors: runs {@link #first} first, then based on
its result, creates {@link #restFuture}
+ * using {@link #restFactory} and runs that next.
+ */
+public class ChainedProcessorManager<A, B, R> implements
ProcessorManager<Object, R>
+{
+ /**
+ * First processor. This one blocks all the others. The reference is set to
null once the processor has been
+ * returned by the channel.
+ */
+ @Nullable
+ private FrameProcessor<A> first;
+
+ /**
+ * Produces {@link #restFuture}.
+ */
+ private final Function<A, ProcessorManager<B, R>> restFactory;
+
+ /**
+ * The rest of the processors. Produced by {@link #restFactory} once {@link
#first} has completed.
+ */
+ private final SettableFuture<ProcessorManager<B, R>> restFuture =
SettableFuture.create();
+
+ public ChainedProcessorManager(
+ final FrameProcessor<A> first,
+ final Function<A, ProcessorManager<B, R>> restFactory
+ )
+ {
+ this.first = Preconditions.checkNotNull(first, "first");
+ this.restFactory = Preconditions.checkNotNull(restFactory, "restFactory");
+ }
+
+ @Override
+ public ListenableFuture<Optional<ProcessorAndCallback<Object>>> next()
+ {
+ if (first != null) {
+ //noinspection unchecked
+ final FrameProcessor<Object> tmp = (FrameProcessor<Object>) first;
+ first = null;
+ return Futures.immediateFuture(Optional.of(new
ProcessorAndCallback<>(tmp, this::onFirstProcessorComplete)));
+ } else {
+ return FutureUtils.transformAsync(
+ restFuture,
+ rest -> (ListenableFuture) rest.next()
+ );
+ }
+ }
+
+ private void onFirstProcessorComplete(final Object firstResult)
+ {
+ //noinspection unchecked
+ restFuture.set(restFactory.apply((A) firstResult));
+ }
+
+ @Override
+ public R result()
+ {
+ return FutureUtils.getUncheckedImmediately(restFuture).result();
+ }
+
+ @Override
+ public void close()
+ {
Review Comment:
What do you mean by this?
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