Google Git
Sign in
apache / beam / 8787c13675bfa8484c1f6074165c6cbd613c734b / . / sdks / java / core / src / main / java / org / apache / beam / sdk / transforms / Combine.java
blob: a3b56657877ff210a294f4dc7b01f2e952fe0e59 [file] [log] [blame]
/*
* 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.beam.sdk.transforms;
import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkState;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ThreadLocalRandom;
import org.apache.beam.sdk.coders.CannotProvideCoderException;
import org.apache.beam.sdk.coders.Coder;
import org.apache.beam.sdk.coders.CoderException;
import org.apache.beam.sdk.coders.CoderRegistry;
import org.apache.beam.sdk.coders.DelegateCoder;
import org.apache.beam.sdk.coders.IterableCoder;
import org.apache.beam.sdk.coders.KvCoder;
import org.apache.beam.sdk.coders.StructuredCoder;
import org.apache.beam.sdk.coders.VarIntCoder;
import org.apache.beam.sdk.coders.VoidCoder;
import org.apache.beam.sdk.options.PipelineOptions;
import org.apache.beam.sdk.transforms.CombineFnBase.AbstractGlobalCombineFn;
import org.apache.beam.sdk.transforms.CombineFnBase.GlobalCombineFn;
import org.apache.beam.sdk.transforms.CombineWithContext.CombineFnWithContext;
import org.apache.beam.sdk.transforms.CombineWithContext.Context;
import org.apache.beam.sdk.transforms.CombineWithContext.RequiresContextInternal;
import org.apache.beam.sdk.transforms.View.CreatePCollectionView;
import org.apache.beam.sdk.transforms.display.DisplayData;
import org.apache.beam.sdk.transforms.display.DisplayData.Builder;
import org.apache.beam.sdk.transforms.display.HasDisplayData;
import org.apache.beam.sdk.transforms.windowing.GlobalWindow;
import org.apache.beam.sdk.transforms.windowing.GlobalWindows;
import org.apache.beam.sdk.transforms.windowing.Window;
import org.apache.beam.sdk.util.AppliedCombineFn;
import org.apache.beam.sdk.util.NameUtils;
import org.apache.beam.sdk.util.NameUtils.NameOverride;
import org.apache.beam.sdk.util.SerializableUtils;
import org.apache.beam.sdk.values.KV;
import org.apache.beam.sdk.values.PCollection;
import org.apache.beam.sdk.values.PCollectionList;
import org.apache.beam.sdk.values.PCollectionTuple;
import org.apache.beam.sdk.values.PCollectionView;
import org.apache.beam.sdk.values.PCollectionViews;
import org.apache.beam.sdk.values.PCollectionViews.TypeDescriptorSupplier;
import org.apache.beam.sdk.values.PValue;
import org.apache.beam.sdk.values.TupleTag;
import org.apache.beam.sdk.values.TupleTagList;
import org.apache.beam.sdk.values.TypeDescriptor;
import org.apache.beam.sdk.values.WindowingStrategy;
import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.ImmutableList;
import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.collect.Iterables;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* {@code PTransform}s for combining {@code PCollection} elements globally and per-key.
*
* <p>See the <a
* href="https://beam.apache.org/documentation/programming-guide/#transforms-combine">documentation</a>
* for how to use the operations in this class.
*/
@SuppressWarnings({
"nullness" // TODO(https://issues.apache.org/jira/browse/BEAM-10402)
})
public class Combine {
private Combine() {
// do not instantiate
}
/**
* Returns a {@link Globally Combine.Globally} {@code PTransform} that uses the given {@code
* SerializableFunction} to combine all the elements in each window of the input {@code
* PCollection} into a single value in the output {@code PCollection}. The types of the input
* elements and the output elements must be the same.
*
* <p>If the input {@code PCollection} is windowed into {@link GlobalWindows}, a default value in
* the {@link GlobalWindow} will be output if the input {@code PCollection} is empty. To use this
* with inputs with other windowing, either {@link Globally#withoutDefaults} or {@link
* Globally#asSingletonView} must be called.
*
* <p>See {@link Globally Combine.Globally} for more information.
*/
public static <V> Globally<V, V> globally(SerializableFunction<Iterable<V>, V> combiner) {
return globally(IterableCombineFn.of(combiner), displayDataForFn(combiner));
}
/**
* Returns a {@link Globally Combine.Globally} {@code PTransform} that uses the given {@code
* SerializableBiFunction} to combine all the elements in each window of the input {@code
* PCollection} into a single value in the output {@code PCollection}. The types of the input
* elements and the output elements must be the same.
*
* <p>If the input {@code PCollection} is windowed into {@link GlobalWindows}, a default value in
* the {@link GlobalWindow} will be output if the input {@code PCollection} is empty. To use this
* with inputs with other windowing, either {@link Globally#withoutDefaults} or {@link
* Globally#asSingletonView} must be called.
*
* <p>See {@link Globally Combine.Globally} for more information.
*/
public static <V> Globally<V, V> globally(SerializableBiFunction<V, V, V> combiner) {
return globally(BinaryCombineFn.of(combiner), displayDataForFn(combiner));
}
/**
* Returns a {@link Globally Combine.Globally} {@code PTransform} that uses the given {@code
* GloballyCombineFn} to combine all the elements in each window of the input {@code PCollection}
* into a single value in the output {@code PCollection}. The types of the input elements and the
* output elements can differ.
*
* <p>If the input {@code PCollection} is windowed into {@link GlobalWindows}, a default value in
* the {@link GlobalWindow} will be output if the input {@code PCollection} is empty. To use this
* with inputs with other windowing, either {@link Globally#withoutDefaults} or {@link
* Globally#asSingletonView} must be called.
*
* <p>See {@link Globally Combine.Globally} for more information.
*/
public static <InputT, OutputT> Globally<InputT, OutputT> globally(
GlobalCombineFn<? super InputT, ?, OutputT> fn) {
return globally(fn, displayDataForFn(fn));
}
private static <T> DisplayData.ItemSpec<? extends Class<?>> displayDataForFn(T fn) {
return DisplayData.item("combineFn", fn.getClass()).withLabel("Combiner");
}
private static <InputT, OutputT> Globally<InputT, OutputT> globally(
GlobalCombineFn<? super InputT, ?, OutputT> fn,
DisplayData.ItemSpec<? extends Class<?>> fnDisplayData) {
return new Globally<>(fn, fnDisplayData, true, 0, ImmutableList.of());
}
/**
* Returns a {@link PerKey Combine.PerKey} {@code PTransform} that first groups its input {@code
* PCollection} of {@code KV}s by keys and windows, then invokes the given function on each of the
* values lists to produce a combined value, and then returns a {@code PCollection} of {@code KV}s
* mapping each distinct key to its combined value for each window.
*
* <p>Each output element is in the window by which its corresponding input was grouped, and has
* the timestamp of the end of that window. The output {@code PCollection} has the same {@link
* org.apache.beam.sdk.transforms.windowing.WindowFn} as the input.
*
* <p>See {@link PerKey Combine.PerKey} for more information.
*/
public static <K, V> PerKey<K, V, V> perKey(SerializableFunction<Iterable<V>, V> fn) {
return perKey(IterableCombineFn.of(fn), displayDataForFn(fn));
}
/**
* Returns a {@link PerKey Combine.PerKey} {@code PTransform} that first groups its input {@code
* PCollection} of {@code KV}s by keys and windows, then invokes the given function on each of the
* values lists to produce a combined value, and then returns a {@code PCollection} of {@code KV}s
* mapping each distinct key to its combined value for each window.
*
* <p>Each output element is in the window by which its corresponding input was grouped, and has
* the timestamp of the end of that window. The output {@code PCollection} has the same {@link
* org.apache.beam.sdk.transforms.windowing.WindowFn} as the input.
*
* <p>See {@link PerKey Combine.PerKey} for more information.
*/
public static <K, V> PerKey<K, V, V> perKey(SerializableBiFunction<V, V, V> fn) {
return perKey(BinaryCombineFn.of(fn), displayDataForFn(fn));
}
/**
* Returns a {@link PerKey Combine.PerKey} {@code PTransform} that first groups its input {@code
* PCollection} of {@code KV}s by keys and windows, then invokes the given function on each of the
* values lists to produce a combined value, and then returns a {@code PCollection} of {@code KV}s
* mapping each distinct key to its combined value for each window.
*
* <p>Each output element is in the window by which its corresponding input was grouped, and has
* the timestamp of the end of that window. The output {@code PCollection} has the same {@link
* org.apache.beam.sdk.transforms.windowing.WindowFn} as the input.
*
* <p>See {@link PerKey Combine.PerKey} for more information.
*/
public static <K, InputT, OutputT> PerKey<K, InputT, OutputT> perKey(
GlobalCombineFn<? super InputT, ?, OutputT> fn) {
return perKey(fn, displayDataForFn(fn));
}
private static <K, InputT, OutputT> PerKey<K, InputT, OutputT> perKey(
GlobalCombineFn<? super InputT, ?, OutputT> fn,
DisplayData.ItemSpec<? extends Class<?>> fnDisplayData) {
return new PerKey<>(fn, fnDisplayData, false /*fewKeys*/);
}
/** Returns a {@link PerKey Combine.PerKey}, and set fewKeys in {@link GroupByKey}. */
private static <K, InputT, OutputT> PerKey<K, InputT, OutputT> fewKeys(
GlobalCombineFn<? super InputT, ?, OutputT> fn,
DisplayData.ItemSpec<? extends Class<?>> fnDisplayData) {
return new PerKey<>(fn, fnDisplayData, true /*fewKeys*/);
}
/**
* Returns a {@link GroupedValues Combine.GroupedValues} {@code PTransform} that takes a {@code
* PCollection} of {@code KV}s where a key maps to an {@code Iterable} of values, e.g., the result
* of a {@code GroupByKey}, then uses the given {@code SerializableFunction} to combine all the
* values associated with a key, ignoring the key. The type of the input and output values must be
* the same.
*
* <p>Each output element has the same timestamp and is in the same window as its corresponding
* input element, and the output {@code PCollection} has the same {@link
* org.apache.beam.sdk.transforms.windowing.WindowFn} associated with it as the input.
*
* <p>See {@link GroupedValues Combine.GroupedValues} for more information.
*
* <p>Note that {@link #perKey(SerializableFunction)} is typically more convenient to use than
* {@link GroupByKey} followed by {@code groupedValues(...)}.
*/
public static <K, V> GroupedValues<K, V, V> groupedValues(
SerializableFunction<Iterable<V>, V> fn) {
return groupedValues(IterableCombineFn.of(fn), displayDataForFn(fn));
}
/**
* Returns a {@link GroupedValues Combine.GroupedValues} {@code PTransform} that takes a {@code
* PCollection} of {@code KV}s where a key maps to an {@code Iterable} of values, e.g., the result
* of a {@code GroupByKey}, then uses the given {@code SerializableFunction} to combine all the
* values associated with a key, ignoring the key. The type of the input and output values must be
* the same.
*
* <p>Each output element has the same timestamp and is in the same window as its corresponding
* input element, and the output {@code PCollection} has the same {@link
* org.apache.beam.sdk.transforms.windowing.WindowFn} associated with it as the input.
*
* <p>See {@link GroupedValues Combine.GroupedValues} for more information.
*
* <p>Note that {@link #perKey(SerializableBiFunction)} is typically more convenient to use than
* {@link GroupByKey} followed by {@code groupedValues(...)}.
*/
public static <K, V> GroupedValues<K, V, V> groupedValues(SerializableBiFunction<V, V, V> fn) {
return groupedValues(BinaryCombineFn.of(fn), displayDataForFn(fn));
}
/**
* Returns a {@link GroupedValues Combine.GroupedValues} {@code PTransform} that takes a {@code
* PCollection} of {@code KV}s where a key maps to an {@code Iterable} of values, e.g., the result
* of a {@code GroupByKey}, then uses the given {@code CombineFn} to combine all the values
* associated with a key, ignoring the key. The types of the input and output values can differ.
*
* <p>Each output element has the same timestamp and is in the same window as its corresponding
* input element, and the output {@code PCollection} has the same {@link
* org.apache.beam.sdk.transforms.windowing.WindowFn} associated with it as the input.
*
* <p>See {@link GroupedValues Combine.GroupedValues} for more information.
*
* <p>Note that {@link #perKey(CombineFnBase.GlobalCombineFn)} is typically more convenient to use
* than {@link GroupByKey} followed by {@code groupedValues(...)}.
*/
public static <K, InputT, OutputT> GroupedValues<K, InputT, OutputT> groupedValues(
GlobalCombineFn<? super InputT, ?, OutputT> fn) {
return groupedValues(fn, displayDataForFn(fn));
}
private static <K, InputT, OutputT> GroupedValues<K, InputT, OutputT> groupedValues(
GlobalCombineFn<? super InputT, ?, OutputT> fn,
DisplayData.ItemSpec<? extends Class<?>> fnDisplayData) {
return new GroupedValues<>(fn, fnDisplayData);
}
/////////////////////////////////////////////////////////////////////////////
/**
* A {@code CombineFn<InputT, AccumT, OutputT>} specifies how to combine a collection of input
* values of type {@code InputT} into a single output value of type {@code OutputT}. It does this
* via one or more intermediate mutable accumulator values of type {@code AccumT}.
*
* <p>The overall process to combine a collection of input {@code InputT} values into a single
* output {@code OutputT} value is as follows:
*
* <ol>
* <li>The input {@code InputT} values are partitioned into one or more batches.
* <li>For each batch, the {@link #createAccumulator} operation is invoked to create a fresh
* mutable accumulator value of type {@code AccumT}, initialized to represent the
* combination of zero values.
* <li>For each input {@code InputT} value in a batch, the {@link #addInput} operation is
* invoked to add the value to that batch's accumulator {@code AccumT} value. The
* accumulator may just record the new value (e.g., if {@code AccumT == List<InputT>}, or
* may do work to represent the combination more compactly.
* <li>The {@link #mergeAccumulators} operation is invoked to combine a collection of
* accumulator {@code AccumT} values into a single combined output accumulator {@code
* AccumT} value, once the merging accumulators have had all all the input values in their
* batches added to them. This operation is invoked repeatedly, until there is only one
* accumulator value left.
* <li>The {@link #extractOutput} operation is invoked on the final accumulator {@code AccumT}
* value to get the output {@code OutputT} value.
* </ol>
*
* <p>For example:
*
* <pre><code>
* public class AverageFn extends{@literal CombineFn<Integer, AverageFn.Accum, Double>} {
* public static class Accum implements Serializable {
* int sum = 0;
* int count = 0;
*
* {@literal @Override}
* public boolean equals(@Nullable Object other) {
* if (other == null) return false;
* if (other == this) return true;
* if (!(other instanceof Accum))return false;
*
*
* Accum o = (Accum)other;
* if (this.sum != o.sum || this.count != o.count) {
* return false;
* } else {
* return true;
* }
* }
* }
*
* public Accum createAccumulator() {
* return new Accum();
* }
*
* public Accum addInput(Accum accum, Integer input) {
* accum.sum += input;
* accum.count++;
* return accum;
* }
*
* public Accum{@literal mergeAccumulators(Iterable<Accum> accums)} {
* Accum merged = createAccumulator();
* for (Accum accum : accums) {
* merged.sum += accum.sum;
* merged.count += accum.count;
* }
* return merged;
* }
*
* public Double extractOutput(Accum accum) {
* return ((double) accum.sum) / accum.count;
* }
* }{@literal
* PCollection<Integer> pc = ...;
* PCollection<Double> average = pc.apply(Combine.globally(new AverageFn()));
* }</code></pre>
*
* <p>Combining functions used by {@link Combine.Globally}, {@link Combine.PerKey}, {@link
* Combine.GroupedValues}, and {@code PTransforms} derived from them should be <i>associative</i>
* and <i>commutative</i>. Associativity is required because input values are first broken up into
* subgroups before being combined, and their intermediate results further combined, in an
* arbitrary tree structure. Commutativity is required because any order of the input values is
* ignored when breaking up input values into groups.
*
* <h3>Note on Data Encoding</h3>
*
* <p>Some form of data encoding is required when using custom types in a CombineFn which do not
* have well-known coders. The sample code above uses a custom Accumulator which gets coder by
* implementing {@link java.io.Serializable}. By doing this, we are relying on the generic {@link
* org.apache.beam.sdk.coders.CoderProvider}, which is able to provide a coder for any {@link
* java.io.Serializable} if applicable. In cases where {@link java.io.Serializable} is not
* efficient, or inapplicable, in general there are two alternatives for encoding:
*
* <ul>
* <li>Default {@link org.apache.beam.sdk.coders.CoderRegistry}. For example, implement a coder
* class explicitly and use the {@code @DefaultCoder} tag. See the {@link
* org.apache.beam.sdk.coders.CoderRegistry} for the numerous ways in which to bind a type
* to a coder.
* <li>CombineFn specific way. While extending CombineFn, overwrite both {@link
* #getAccumulatorCoder} and {@link #getDefaultOutputCoder}.
* </ul>
*
* @param <InputT> type of input values
* @param <AccumT> type of mutable accumulator values
* @param <OutputT> type of output values
*/
public abstract static class CombineFn<
InputT extends @Nullable Object,
AccumT extends @Nullable Object,
OutputT extends @Nullable Object>
extends AbstractGlobalCombineFn<InputT, AccumT, OutputT> {
/**
* Returns a new, mutable accumulator value, representing the accumulation of zero input values.
*/
public abstract AccumT createAccumulator();
/**
* Adds the given input value to the given accumulator, returning the new accumulator value.
*
* @param mutableAccumulator may be modified and returned for efficiency
* @param input should not be mutated
*/
public abstract AccumT addInput(AccumT mutableAccumulator, InputT input);
/**
* Returns an accumulator representing the accumulation of all the input values accumulated in
* the merging accumulators.
*
* @param accumulators only the first accumulator may be modified and returned for efficiency;
* the other accumulators should not be mutated, because they may be shared with other code
* and mutating them could lead to incorrect results or data corruption.
*/
public abstract AccumT mergeAccumulators(Iterable<AccumT> accumulators);
/**
* Returns the output value that is the result of combining all the input values represented by
* the given accumulator.
*
* @param accumulator can be modified for efficiency
*/
public abstract OutputT extractOutput(AccumT accumulator);
/**
* Returns an accumulator that represents the same logical value as the input accumulator, but
* may have a more compact representation.
*
* <p>For most CombineFns this would be a no-op, but should be overridden by CombineFns that
* (for example) buffer up elements and combine them in batches.
*
* <p>For efficiency, the input accumulator may be modified and returned.
*
* <p>By default returns the original accumulator.
*/
public AccumT compact(AccumT accumulator) {
return accumulator;
}
/**
* Applies this {@code CombineFn} to a collection of input values to produce a combined output
* value.
*
* <p>Useful when using a {@code CombineFn} separately from a {@code Combine} transform. Does
* not invoke the {@link #mergeAccumulators} operation.
*/
public OutputT apply(Iterable<? extends InputT> inputs) {
AccumT accum = createAccumulator();
for (InputT input : inputs) {
accum = addInput(accum, input);
}
return extractOutput(accum);
}
/**
* {@inheritDoc}
*
* <p>By default returns the extract output of an empty accumulator.
*/
@Override
public OutputT defaultValue() {
return extractOutput(createAccumulator());
}
/**
* Returns a {@link TypeDescriptor} capturing what is known statically about the output type of
* this {@code CombineFn} instance's most-derived class.
*
* <p>In the normal case of a concrete {@code CombineFn} subclass with no generic type
* parameters of its own, this will be a complete non-generic type.
*/
public TypeDescriptor<OutputT> getOutputType() {
return new TypeDescriptor<OutputT>(getClass()) {};
}
/**
* Returns a {@link TypeDescriptor} capturing what is known statically about the input type of
* this {@code CombineFn} instance's most-derived class.
*
* <p>In the normal case of a concrete {@code CombineFn} subclass with no generic type
* parameters of its own, this will be a complete non-generic type.
*/
public TypeDescriptor<InputT> getInputType() {
return new TypeDescriptor<InputT>(getClass()) {};
}
}
/////////////////////////////////////////////////////////////////////////////
/**
* An abstract subclass of {@link CombineFn} for implementing combiners that are more easily
* expressed as binary operations.
*/
public abstract static class BinaryCombineFn<V> extends CombineFn<V, Holder<V>, V> {
/**
* Returns a {@code CombineFn} that uses the given {@code SerializableBiFunction} to combine
* values.
*/
public static <V> BinaryCombineFn<V> of(SerializableBiFunction<V, V, V> combiner) {
return new BinaryCombineFn<V>() {
@Override
public V apply(V left, V right) {
return combiner.apply(left, right);
}
};
}
/** Applies the binary operation to the two operands, returning the result. */
public abstract V apply(V left, V right);
/** Returns the value that should be used for the combine of the empty set. */
public @Nullable V identity() {
return null;
}
@Override
public Holder<V> createAccumulator() {
return new Holder<>();
}
@Override
public Holder<V> addInput(Holder<V> accumulator, V input) {
if (accumulator.present) {
accumulator.set(apply(accumulator.value, input));
} else {
accumulator.set(input);
}
return accumulator;
}
@Override
public Holder<V> mergeAccumulators(Iterable<Holder<V>> accumulators) {
Iterator<Holder<V>> iter = accumulators.iterator();
if (!iter.hasNext()) {
return createAccumulator();
} else {
Holder<V> running = iter.next();
while (iter.hasNext()) {
Holder<V> accum = iter.next();
if (accum.present) {
if (running.present) {
running.set(apply(running.value, accum.value));
} else {
running.set(accum.value);
}
}
}
return running;
}
}
@Override
public V extractOutput(Holder<V> accumulator) {
if (accumulator.present) {
return accumulator.value;
} else {
return identity();
}
}
@Override
public Coder<Holder<V>> getAccumulatorCoder(CoderRegistry registry, Coder<V> inputCoder) {
return new HolderCoder<>(inputCoder);
}
@Override
public Coder<V> getDefaultOutputCoder(CoderRegistry registry, Coder<V> inputCoder) {
return inputCoder;
}
}
/**
* Holds a single value value of type {@code V} which may or may not be present.
*
* <p>Used only as a private accumulator class.
*/
public static class Holder<V> {
private @Nullable V value;
private boolean present;
private Holder() {}
private Holder(V value) {
set(value);
}
private void set(V value) {
this.present = true;
this.value = value;
}
@Override
public String toString() {
return "Combine.Holder(value=" + value + ", present=" + present + ")";
}
}
/** A {@link Coder} for a {@link Holder}. */
private static class HolderCoder<V> extends StructuredCoder<Holder<V>> {
private Coder<V> valueCoder;
public HolderCoder(Coder<V> valueCoder) {
this.valueCoder = valueCoder;
}
@Override
public void encode(Holder<V> accumulator, OutputStream outStream)
throws CoderException, IOException {
encode(accumulator, outStream, Context.NESTED);
}
@Override
public void encode(Holder<V> accumulator, OutputStream outStream, Context context)
throws CoderException, IOException {
if (accumulator.present) {
outStream.write(1);
valueCoder.encode(accumulator.value, outStream, context);
} else {
outStream.write(0);
}
}
@Override
public Holder<V> decode(InputStream inStream) throws CoderException, IOException {
return decode(inStream, Context.NESTED);
}
@Override
public Holder<V> decode(InputStream inStream, Context context)
throws CoderException, IOException {
if (inStream.read() == 1) {
return new Holder<>(valueCoder.decode(inStream, context));
} else {
return new Holder<>();
}
}
@Override
public List<? extends Coder<?>> getCoderArguments() {
return Collections.singletonList(valueCoder);
}
@Override
public void verifyDeterministic() throws NonDeterministicException {
valueCoder.verifyDeterministic();
}
}
/**
* An abstract subclass of {@link CombineFn} for implementing combiners that are more easily and
* efficiently expressed as binary operations on <code>int</code>s
*
* <p>It uses {@code int[0]} as the mutable accumulator.
*/
public abstract static class BinaryCombineIntegerFn extends CombineFn<Integer, int[], Integer> {
/** Applies the binary operation to the two operands, returning the result. */
public abstract int apply(int left, int right);
/**
* Returns the identity element of this operation, i.e. an element {@code e} such that {@code
* apply(e, x) == apply(x, e) == x} for all values of {@code x}.
*/
public abstract int identity();
@Override
public int[] createAccumulator() {
return wrap(identity());
}
@Override
public int[] addInput(int[] accumulator, Integer input) {
accumulator[0] = apply(accumulator[0], input);
return accumulator;
}
@Override
public int[] mergeAccumulators(Iterable<int[]> accumulators) {
Iterator<int[]> iter = accumulators.iterator();
if (!iter.hasNext()) {
return createAccumulator();
} else {
int[] running = iter.next();
while (iter.hasNext()) {
running[0] = apply(running[0], iter.next()[0]);
}
return running;
}
}
@Override
public Integer extractOutput(int[] accumulator) {
return accumulator[0];
}
@Override
public Coder<int[]> getAccumulatorCoder(CoderRegistry registry, Coder<Integer> inputCoder) {
return DelegateCoder.of(
inputCoder, new ToIntegerCodingFunction(), new FromIntegerCodingFunction());
}
@Override
public Coder<Integer> getDefaultOutputCoder(CoderRegistry registry, Coder<Integer> inputCoder) {
return inputCoder;
}
private static int[] wrap(int value) {
return new int[] {value};
}
private static final class ToIntegerCodingFunction
implements DelegateCoder.CodingFunction<int[], Integer> {
@Override
public Integer apply(int[] accumulator) {
return accumulator[0];
}
@Override
public boolean equals(@Nullable Object o) {
return o instanceof ToIntegerCodingFunction;
}
@Override
public int hashCode() {
return this.getClass().hashCode();
}
}
private static final class FromIntegerCodingFunction
implements DelegateCoder.CodingFunction<Integer, int[]> {
@Override
public int[] apply(Integer value) {
return wrap(value);
}
@Override
public boolean equals(@Nullable Object o) {
return o instanceof FromIntegerCodingFunction;
}
@Override
public int hashCode() {
return this.getClass().hashCode();
}
}
}
/**
* An abstract subclass of {@link CombineFn} for implementing combiners that are more easily and
* efficiently expressed as binary operations on <code>long</code>s.
*
* <p>It uses {@code long[0]} as the mutable accumulator.
*/
public abstract static class BinaryCombineLongFn extends CombineFn<Long, long[], Long> {
/** Applies the binary operation to the two operands, returning the result. */
public abstract long apply(long left, long right);
/**
* Returns the identity element of this operation, i.e. an element {@code e} such that {@code
* apply(e, x) == apply(x, e) == x} for all values of {@code x}.
*/
public abstract long identity();
@Override
public long[] createAccumulator() {
return wrap(identity());
}
@Override
public long[] addInput(long[] accumulator, Long input) {
accumulator[0] = apply(accumulator[0], input);
return accumulator;
}
@Override
public long[] mergeAccumulators(Iterable<long[]> accumulators) {
Iterator<long[]> iter = accumulators.iterator();
if (!iter.hasNext()) {
return createAccumulator();
} else {
long[] running = iter.next();
while (iter.hasNext()) {
running[0] = apply(running[0], iter.next()[0]);
}
return running;
}
}
@Override
public Long extractOutput(long[] accumulator) {
return accumulator[0];
}
@Override
public Coder<long[]> getAccumulatorCoder(CoderRegistry registry, Coder<Long> inputCoder) {
return DelegateCoder.of(inputCoder, new ToLongCodingFunction(), new FromLongCodingFunction());
}
@Override
public Coder<Long> getDefaultOutputCoder(CoderRegistry registry, Coder<Long> inputCoder) {
return inputCoder;
}
private static long[] wrap(long value) {
return new long[] {value};
}
private static final class ToLongCodingFunction
implements DelegateCoder.CodingFunction<long[], Long> {
@Override
public Long apply(long[] accumulator) {
return accumulator[0];
}
@Override
public boolean equals(@Nullable Object o) {
return o instanceof ToLongCodingFunction;
}
@Override
public int hashCode() {
return this.getClass().hashCode();
}
}
private static final class FromLongCodingFunction
implements DelegateCoder.CodingFunction<Long, long[]> {
@Override
public long[] apply(Long value) {
return wrap(value);
}
@Override
public boolean equals(@Nullable Object o) {
return o instanceof FromLongCodingFunction;
}
@Override
public int hashCode() {
return this.getClass().hashCode();
}
}
}
/**
* An abstract subclass of {@link CombineFn} for implementing combiners that are more easily and
* efficiently expressed as binary operations on <code>double</code>s.
*
* <p>It uses {@code double[0]} as the mutable accumulator.
*/
public abstract static class BinaryCombineDoubleFn extends CombineFn<Double, double[], Double> {
/** Applies the binary operation to the two operands, returning the result. */
public abstract double apply(double left, double right);
/**
* Returns the identity element of this operation, i.e. an element {@code e} such that {@code
* apply(e, x) == apply(x, e) == x} for all values of {@code x}.
*/
public abstract double identity();
@Override
public double[] createAccumulator() {
return wrap(identity());
}
@Override
public double[] addInput(double[] accumulator, Double input) {
accumulator[0] = apply(accumulator[0], input);
return accumulator;
}
@Override
public double[] mergeAccumulators(Iterable<double[]> accumulators) {
Iterator<double[]> iter = accumulators.iterator();
if (!iter.hasNext()) {
return createAccumulator();
} else {
double[] running = iter.next();
while (iter.hasNext()) {
running[0] = apply(running[0], iter.next()[0]);
}
return running;
}
}
@Override
public Double extractOutput(double[] accumulator) {
return accumulator[0];
}
@Override
public Coder<double[]> getAccumulatorCoder(CoderRegistry registry, Coder<Double> inputCoder) {
return DelegateCoder.of(
inputCoder, new ToDoubleCodingFunction(), new FromDoubleCodingFunction());
}
@Override
public Coder<Double> getDefaultOutputCoder(CoderRegistry registry, Coder<Double> inputCoder) {
return inputCoder;
}
private static double[] wrap(double value) {
return new double[] {value};
}
private static final class ToDoubleCodingFunction
implements DelegateCoder.CodingFunction<double[], Double> {
@Override
public Double apply(double[] accumulator) {
return accumulator[0];
}
@Override
public boolean equals(@Nullable Object o) {
return o instanceof ToDoubleCodingFunction;
}
@Override
public int hashCode() {
return this.getClass().hashCode();
}
}
private static final class FromDoubleCodingFunction
implements DelegateCoder.CodingFunction<Double, double[]> {
@Override
public double[] apply(Double value) {
return wrap(value);
}
@Override
public boolean equals(@Nullable Object o) {
return o instanceof FromDoubleCodingFunction;
}
@Override
public int hashCode() {
return this.getClass().hashCode();
}
}
}
/////////////////////////////////////////////////////////////////////////////
/**
* A {@code CombineFn} that uses a subclass of {@link AccumulatingCombineFn.Accumulator} as its
* accumulator type. By defining the operations of the {@code Accumulator} helper class, the
* operations of the enclosing {@code CombineFn} are automatically provided. This can reduce the
* code required to implement a {@code CombineFn}.
*
* <p>For example, the example from {@link CombineFn} above can be expressed using {@code
* AccumulatingCombineFn} more concisely as follows:
*
* <pre>{@code
* public class AverageFn
* extends AccumulatingCombineFn<Integer, AverageFn.Accum, Double> {
* public Accum createAccumulator() {
* return new Accum();
* }
* public class Accum
* extends AccumulatingCombineFn<Integer, AverageFn.Accum, Double>
* .Accumulator {
* private int sum = 0;
* private int count = 0;
* public void addInput(Integer input) {
* sum += input;
* count++;
* }
* public void mergeAccumulator(Accum other) {
* sum += other.sum;
* count += other.count;
* }
* public Double extractOutput() {
* return ((double) sum) / count;
* }
* }
* }
* PCollection<Integer> pc = ...;
* PCollection<Double> average = pc.apply(Combine.globally(new AverageFn()));
* }</pre>
*
* @param <InputT> type of input values
* @param <AccumT> type of mutable accumulator values
* @param <OutputT> type of output values
*/
public abstract static class AccumulatingCombineFn<
InputT,
AccumT extends AccumulatingCombineFn.Accumulator<InputT, AccumT, OutputT>,
OutputT>
extends CombineFn<InputT, AccumT, OutputT> {
/** The type of mutable accumulator values used by this {@code AccumulatingCombineFn}. */
public interface Accumulator<InputT, AccumT, OutputT> {
/** Adds the given input value to this accumulator, modifying this accumulator. */
void addInput(InputT input);
/** Adds the input values represented by the given accumulator into this accumulator. */
void mergeAccumulator(AccumT other);
/**
* Returns the output value that is the result of combining all the input values represented
* by this accumulator.
*/
OutputT extractOutput();
}
@Override
public final AccumT addInput(AccumT accumulator, InputT input) {
accumulator.addInput(input);
return accumulator;
}
@Override
public final AccumT mergeAccumulators(Iterable<AccumT> accumulators) {
AccumT accumulator = createAccumulator();
for (AccumT partial : accumulators) {
accumulator.mergeAccumulator(partial);
}
return accumulator;
}
@Override
public final OutputT extractOutput(AccumT accumulator) {
return accumulator.extractOutput();
}
}
/////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////
/**
* {@code Combine.Globally<InputT, OutputT>} takes a {@code PCollection<InputT>} and returns a
* {@code PCollection<OutputT>} whose elements are the result of combining all the elements in
* each window of the input {@code PCollection}, using a specified {@link CombineFn
* CombineFn&lt;InputT, AccumT, OutputT&gt;}. It is common for {@code InputT == OutputT}, but not
* required. Common combining functions include sums, mins, maxes, and averages of numbers,
* conjunctions and disjunctions of booleans, statistical aggregations, etc.
*
* <p>Example of use:
*
* <pre>{@code
* PCollection<Integer> pc = ...;
* PCollection<Integer> sum = pc.apply(
* Combine.globally(new Sum.SumIntegerFn()));
* }</pre>
*
* <p>Combining can happen in parallel, with different subsets of the input {@code PCollection}
* being combined separately, and their intermediate results combined further, in an arbitrary
* tree reduction pattern, until a single result value is produced.
*
* <p>If the input {@code PCollection} is windowed into {@link GlobalWindows}, a default value in
* the {@link GlobalWindow} will be output if the input {@code PCollection} is empty. To use this
* with inputs with other windowing, either {@link #withoutDefaults} or {@link #asSingletonView}
* must be called, as the default value cannot be automatically assigned to any single window.
*
* <p>By default, the {@code Coder} of the output {@code PValue<OutputT>} is inferred from the
* concrete type of the {@code CombineFn<InputT, AccumT, OutputT>}'s output type {@code OutputT}.
*
* <p>See also {@link #perKey}/{@link PerKey Combine.PerKey} and {@link #groupedValues}/{@link
* GroupedValues Combine.GroupedValues}, which are useful for combining values associated with
* each key in a {@code PCollection} of {@code KV}s.
*
* @param <InputT> type of input values
* @param <OutputT> type of output values
*/
public static class Globally<InputT, OutputT>
extends PTransform<PCollection<InputT>, PCollection<OutputT>> {
private final GlobalCombineFn<? super InputT, ?, OutputT> fn;
private final DisplayData.ItemSpec<? extends Class<?>> fnDisplayData;
private final boolean insertDefault;
private final int fanout;
private final List<PCollectionView<?>> sideInputs;
private Globally(
GlobalCombineFn<? super InputT, ?, OutputT> fn,
DisplayData.ItemSpec<? extends Class<?>> fnDisplayData,
boolean insertDefault,
int fanout,
List<PCollectionView<?>> sideInputs) {
this.fn = fn;
this.fnDisplayData = fnDisplayData;
this.insertDefault = insertDefault;
this.fanout = fanout;
this.sideInputs = sideInputs;
}
@Override
protected String getKindString() {
return String.format("Combine.globally(%s)", NameUtils.approximateSimpleName(fn));
}
/**
* Returns a {@link PTransform} that produces a {@code PCollectionView} whose elements are the
* result of combining elements per-window in the input {@code PCollection}. If a value is
* requested from the view for a window that is not present, the result of applying the {@code
* CombineFn} to an empty input set will be returned.
*/
public GloballyAsSingletonView<InputT, OutputT> asSingletonView() {
return new GloballyAsSingletonView<>(fn, fnDisplayData, insertDefault, fanout);
}
/**
* Returns a {@link PTransform} identical to this, but that does not attempt to provide a
* default value in the case of empty input. Required when the input is not globally windowed
* and the output is not being used as a side input.
*/
public Globally<InputT, OutputT> withoutDefaults() {
return new Globally<>(fn, fnDisplayData, false, fanout, sideInputs);
}
/**
* Returns a {@link PTransform} identical to this, but that uses an intermediate node to combine
* parts of the data to reduce load on the final global combine step.
*
* <p>The {@code fanout} parameter determines the number of intermediate keys that will be used.
*/
public Globally<InputT, OutputT> withFanout(int fanout) {
return new Globally<>(fn, fnDisplayData, insertDefault, fanout, sideInputs);
}
/**
* Returns a {@link PTransform} identical to this, but with the specified side inputs to use in
* {@link CombineFnWithContext}.
*/
public Globally<InputT, OutputT> withSideInputs(PCollectionView<?>... sideInputs) {
return withSideInputs(Arrays.asList(sideInputs));
}
/**
* Returns a {@link PTransform} identical to this, but with the specified side inputs to use in
* {@link CombineFnWithContext}.
*/
public Globally<InputT, OutputT> withSideInputs(
Iterable<? extends PCollectionView<?>> sideInputs) {
checkState(fn instanceof RequiresContextInternal);
return new Globally<>(
fn, fnDisplayData, insertDefault, fanout, ImmutableList.copyOf(sideInputs));
}
/** Returns the {@link GlobalCombineFn} used by this Combine operation. */
public GlobalCombineFn<? super InputT, ?, OutputT> getFn() {
return fn;
}
/** Returns the side inputs used by this Combine operation. */
public List<PCollectionView<?>> getSideInputs() {
return sideInputs;
}
/**
* Returns the side inputs of this {@link Combine}, tagged with the tag of the {@link
* PCollectionView}. The values of the returned map will be equal to the result of {@link
* #getSideInputs()}.
*/
@Override
public Map<TupleTag<?>, PValue> getAdditionalInputs() {
return PCollectionViews.toAdditionalInputs(sideInputs);
}
/** Returns whether or not this transformation applies a default value. */
public boolean isInsertDefault() {
return insertDefault;
}
@Override
public PCollection<OutputT> expand(PCollection<InputT> input) {
PCollection<KV<Void, InputT>> withKeys =
input
.apply(WithKeys.of((Void) null))
.setCoder(KvCoder.of(VoidCoder.of(), input.getCoder()));
Combine.PerKey<Void, InputT, OutputT> combine = Combine.fewKeys(fn, fnDisplayData);
if (!sideInputs.isEmpty()) {
combine = combine.withSideInputs(sideInputs);
}
PCollection<KV<Void, OutputT>> combined;
if (fanout >= 2) {
combined = withKeys.apply(combine.withHotKeyFanout(fanout));
} else {
combined = withKeys.apply(combine);
}
PCollection<OutputT> output = combined.apply(Values.create());
if (insertDefault) {
if (!output.getWindowingStrategy().getWindowFn().isCompatible(new GlobalWindows())) {
throw new IllegalStateException(fn.getIncompatibleGlobalWindowErrorMessage());
}
return insertDefaultValueIfEmpty(output);
} else {
return output;
}
}
@Override
public void populateDisplayData(DisplayData.Builder builder) {
super.populateDisplayData(builder);
Combine.populateDisplayData(builder, fn, fnDisplayData);
Combine.populateGlobalDisplayData(builder, fanout, insertDefault);
}
private PCollection<OutputT> insertDefaultValueIfEmpty(PCollection<OutputT> maybeEmpty) {
final PCollectionView<Iterable<OutputT>> maybeEmptyView = maybeEmpty.apply(View.asIterable());
final OutputT defaultValue = fn.defaultValue();
PCollection<OutputT> defaultIfEmpty =
maybeEmpty
.getPipeline()
.apply("CreateVoid", Create.of((Void) null).withCoder(VoidCoder.of()))
.apply(
"ProduceDefault",
ParDo.of(
new DoFn<Void, OutputT>() {
@ProcessElement
public void processElement(ProcessContext c) {
Iterator<OutputT> combined = c.sideInput(maybeEmptyView).iterator();
if (!combined.hasNext()) {
c.output(defaultValue);
}
}
})
.withSideInputs(maybeEmptyView))
.setCoder(maybeEmpty.getCoder())
.setWindowingStrategyInternal(maybeEmpty.getWindowingStrategy());
return PCollectionList.of(maybeEmpty).and(defaultIfEmpty).apply(Flatten.pCollections());
}
}
private static void populateDisplayData(
DisplayData.Builder builder,
HasDisplayData fn,
DisplayData.ItemSpec<? extends Class<?>> fnDisplayItem) {
builder.include("combineFn", fn).add(fnDisplayItem);
}
private static void populateGlobalDisplayData(
DisplayData.Builder builder, int fanout, boolean insertDefault) {
builder
.addIfNotDefault(DisplayData.item("fanout", fanout).withLabel("Key Fanout Size"), 0)
.add(
DisplayData.item("emitDefaultOnEmptyInput", insertDefault)
.withLabel("Emit Default On Empty Input"));
}
/**
* {@code Combine.GloballyAsSingletonView<InputT, OutputT>} takes a {@code PCollection<InputT>}
* and returns a {@code PCollectionView<OutputT>} whose elements are the result of combining all
* the elements in each window of the input {@code PCollection}, using a specified {@link
* CombineFn CombineFn&lt;InputT, AccumT, OutputT&gt;}. It is common for {@code InputT ==
* OutputT}, but not required. Common combining functions include sums, mins, maxes, and averages
* of numbers, conjunctions and disjunctions of booleans, statistical aggregations, etc.
*
* <p>Example of use:
*
* <pre>{@code
* PCollection<Integer> pc = ...;
* PCollection<Integer> sum = pc.apply(
* Combine.globally(new Sum.SumIntegerFn()));
* }</pre>
*
* <p>Combining can happen in parallel, with different subsets of the input {@code PCollection}
* being combined separately, and their intermediate results combined further, in an arbitrary
* tree reduction pattern, until a single result value is produced.
*
* <p>If a value is requested from the view for a window that is not present and {@code
* insertDefault} is true, the result of calling the {@code CombineFn} on empty input will
* returned. If {@code insertDefault} is false, an exception will be thrown instead.
*
* <p>By default, the {@code Coder} of the output {@code PValue<OutputT>} is inferred from the
* concrete type of the {@code CombineFn<InputT, AccumT, OutputT>}'s output type {@code OutputT}.
*
* <p>See also {@link #perKey}/{@link PerKey Combine.PerKey} and {@link #groupedValues}/{@link
* GroupedValues Combine.GroupedValues}, which are useful for combining values associated with
* each key in a {@code PCollection} of {@code KV}s.
*
* @param <InputT> type of input values
* @param <OutputT> type of output values
*/
public static class GloballyAsSingletonView<InputT, OutputT>
extends PTransform<PCollection<InputT>, PCollectionView<OutputT>> {
private final GlobalCombineFn<? super InputT, ?, OutputT> fn;
private final DisplayData.ItemSpec<? extends Class<?>> fnDisplayData;
private final boolean insertDefault;
private final int fanout;
private GloballyAsSingletonView(
GlobalCombineFn<? super InputT, ?, OutputT> fn,
DisplayData.ItemSpec<? extends Class<?>> fnDisplayData,
boolean insertDefault,
int fanout) {
this.fn = fn;
this.fnDisplayData = fnDisplayData;
this.insertDefault = insertDefault;
this.fanout = fanout;
}
@Override
public PCollectionView<OutputT> expand(PCollection<InputT> input) {
PCollection<OutputT> combined =
input.apply(
"CombineValues",
Combine.<InputT, OutputT>globally(fn).withoutDefaults().withFanout(fanout));
Coder<OutputT> outputCoder = combined.getCoder();
PCollectionView<OutputT> view =
PCollectionViews.singletonView(
combined,
(TypeDescriptorSupplier<OutputT>)
() -> outputCoder != null ? outputCoder.getEncodedTypeDescriptor() : null,
input.getWindowingStrategy(),
insertDefault,
insertDefault ? fn.defaultValue() : null,
combined.getCoder());
combined.apply("CreatePCollectionView", CreatePCollectionView.of(view));
return view;
}
public int getFanout() {
return fanout;
}
public boolean getInsertDefault() {
return insertDefault;
}
public GlobalCombineFn<? super InputT, ?, OutputT> getCombineFn() {
return fn;
}
@Override
public void populateDisplayData(DisplayData.Builder builder) {
super.populateDisplayData(builder);
Combine.populateDisplayData(builder, fn, fnDisplayData);
Combine.populateGlobalDisplayData(builder, fanout, insertDefault);
}
}
/**
* Converts a {@link SerializableFunction} from {@code Iterable<V>}s to {@code V}s into a simple
* {@link CombineFn} over {@code V}s.
*
* <p>Used in the implementation of convenience methods like {@link
* #globally(SerializableFunction)}, {@link #perKey(SerializableFunction)}, and {@link
* #groupedValues(SerializableFunction)}.
*/
public static class IterableCombineFn<V> extends CombineFn<V, List<V>, V>
implements NameOverride {
/**
* Returns a {@code CombineFn} that uses the given {@code SerializableFunction} to combine
* values.
*/
public static <V> IterableCombineFn<V> of(SerializableFunction<Iterable<V>, V> combiner) {
return of(combiner, DEFAULT_BUFFER_SIZE);
}
/**
* Returns a {@code CombineFn} that uses the given {@code SerializableFunction} to combine
* values, attempting to buffer at least {@code bufferSize} values between invocations.
*/
public static <V> IterableCombineFn<V> of(
SerializableFunction<Iterable<V>, V> combiner, int bufferSize) {
return new IterableCombineFn<>(combiner, bufferSize);
}
private static final int DEFAULT_BUFFER_SIZE = 20;
/** The combiner function. */
private final SerializableFunction<Iterable<V>, V> combiner;
/** The number of values to accumulate before invoking the combiner function to combine them. */
private final int bufferSize;
private IterableCombineFn(SerializableFunction<Iterable<V>, V> combiner, int bufferSize) {
this.combiner = combiner;
this.bufferSize = bufferSize;
}
@Override
public List<V> createAccumulator() {
return new ArrayList<>();
}
@Override
public List<V> addInput(List<V> accumulator, V input) {
accumulator.add(input);
if (accumulator.size() > bufferSize) {
return mergeToSingleton(accumulator);
} else {
return accumulator;
}
}
@Override
public List<V> mergeAccumulators(Iterable<List<V>> accumulators) {
return mergeToSingleton(Iterables.concat(accumulators));
}
@Override
public V extractOutput(List<V> accumulator) {
return combiner.apply(accumulator);
}
@Override
public List<V> compact(List<V> accumulator) {
return accumulator.size() > 1 ? mergeToSingleton(accumulator) : accumulator;
}
@Override
public void populateDisplayData(DisplayData.Builder builder) {
super.populateDisplayData(builder);
builder.add(DisplayData.item("combineFn", combiner.getClass()).withLabel("Combiner"));
}
private List<V> mergeToSingleton(Iterable<V> values) {
List<V> singleton = new ArrayList<>();
singleton.add(combiner.apply(values));
return singleton;
}
@Override
public String getNameOverride() {
return NameUtils.approximateSimpleName(combiner);
}
}
/**
* Converts a {@link SerializableFunction} from {@code Iterable<V>}s to {@code V}s into a simple
* {@link CombineFn} over {@code V}s.
*
* <p>@deprecated Use {@link IterableCombineFn} or the more space efficient {@link
* BinaryCombineFn} instead (which avoids buffering values).
*/
@Deprecated
public static class SimpleCombineFn<V> extends IterableCombineFn<V> {
/**
* Returns a {@code CombineFn} that uses the given {@code SerializableFunction} to combine
* values.
*/
public static <V> SimpleCombineFn<V> of(SerializableFunction<Iterable<V>, V> combiner) {
return new SimpleCombineFn<>(combiner);
}
protected SimpleCombineFn(SerializableFunction<Iterable<V>, V> combiner) {
super(combiner, IterableCombineFn.DEFAULT_BUFFER_SIZE);
}
}
/////////////////////////////////////////////////////////////////////////////
/**
* {@code PerKey<K, InputT, OutputT>} takes a {@code PCollection<KV<K, InputT>>}, groups it by
* key, applies a combining function to the {@code InputT} values associated with each key to
* produce a combined {@code OutputT} value, and returns a {@code PCollection<KV<K, OutputT>>}
* representing a map from each distinct key of the input {@code PCollection} to the corresponding
* combined value. {@code InputT} and {@code OutputT} are often the same.
*
* <p>This is a concise shorthand for an application of {@link GroupByKey} followed by an
* application of {@link GroupedValues Combine.GroupedValues}. See those operations for more
* details on how keys are compared for equality and on the default {@code Coder} for the output.
*
* <p>Example of use:
*
* <pre>{@code
* PCollection<KV<String, Double>> salesRecords = ...;
* PCollection<KV<String, Double>> totalSalesPerPerson =
* salesRecords.apply(Combine.<String, Double, Double>perKey(
* Sum.ofDoubles()));
* }</pre>
*
* <p>Each output element is in the window by which its corresponding input was grouped, and has
* the timestamp of the end of that window. The output {@code PCollection} has the same {@link
* org.apache.beam.sdk.transforms.windowing.WindowFn} as the input.
*
* @param <K> the type of the keys of the input and output {@code PCollection}s
* @param <InputT> the type of the values of the input {@code PCollection}
* @param <OutputT> the type of the values of the output {@code PCollection}
*/
public static class PerKey<K, InputT, OutputT>
extends PTransform<PCollection<KV<K, InputT>>, PCollection<KV<K, OutputT>>> {
private final GlobalCombineFn<? super InputT, ?, OutputT> fn;
private final DisplayData.ItemSpec<? extends Class<?>> fnDisplayData;
private final boolean fewKeys;
private final List<PCollectionView<?>> sideInputs;
private PerKey(
GlobalCombineFn<? super InputT, ?, OutputT> fn,
DisplayData.ItemSpec<? extends Class<?>> fnDisplayData,
boolean fewKeys) {
this.fn = fn;
this.fnDisplayData = fnDisplayData;
this.fewKeys = fewKeys;
this.sideInputs = ImmutableList.of();
}
private PerKey(
GlobalCombineFn<? super InputT, ?, OutputT> fn,
DisplayData.ItemSpec<? extends Class<?>> fnDisplayData,
boolean fewKeys,
List<PCollectionView<?>> sideInputs) {
this.fn = fn;
this.fnDisplayData = fnDisplayData;
this.fewKeys = fewKeys;
this.sideInputs = sideInputs;
}
@Override
protected String getKindString() {
return String.format("Combine.perKey(%s)", NameUtils.approximateSimpleName(fn));
}
/**
* Returns a {@link PTransform} identical to this, but with the specified side inputs to use in
* {@link CombineFnWithContext}.
*/
public PerKey<K, InputT, OutputT> withSideInputs(PCollectionView<?>... sideInputs) {
return withSideInputs(Arrays.asList(sideInputs));
}
/**
* Returns a {@link PTransform} identical to this, but with the specified side inputs to use in
* {@link CombineFnWithContext}.
*/
public PerKey<K, InputT, OutputT> withSideInputs(
Iterable<? extends PCollectionView<?>> sideInputs) {
checkState(fn instanceof RequiresContextInternal);
return new PerKey<>(fn, fnDisplayData, fewKeys, ImmutableList.copyOf(sideInputs));
}
/**
* If a single key has disproportionately many values, it may become a bottleneck, especially in
* streaming mode. This returns a new per-key combining transform that inserts an intermediate
* node to combine "hot" keys partially before performing the full combine.
*
* @param hotKeyFanout a function from keys to an integer N, where the key will be spread among
* N intermediate nodes for partial combining. If N is less than or equal to 1, this key
* will not be sent through an intermediate node.
*/
public PerKeyWithHotKeyFanout<K, InputT, OutputT> withHotKeyFanout(
SerializableFunction<? super K, Integer> hotKeyFanout) {
return new PerKeyWithHotKeyFanout<>(fn, fnDisplayData, hotKeyFanout);
}
/**
* Like {@link #withHotKeyFanout(SerializableFunction)}, but returning the given constant value
* for every key.
*/
public PerKeyWithHotKeyFanout<K, InputT, OutputT> withHotKeyFanout(final int hotKeyFanout) {
return new PerKeyWithHotKeyFanout<>(
fn,
fnDisplayData,
new SimpleFunction<K, Integer>() {
@Override
public void populateDisplayData(Builder builder) {
super.populateDisplayData(builder);
builder.add(DisplayData.item("fanout", hotKeyFanout).withLabel("Key Fanout Size"));
}
@Override
public Integer apply(K unused) {
return hotKeyFanout;
}
});
}
/** Returns the {@link GlobalCombineFn} used by this Combine operation. */
public GlobalCombineFn<? super InputT, ?, OutputT> getFn() {
return fn;
}
/** Returns the side inputs used by this Combine operation. */
public List<PCollectionView<?>> getSideInputs() {
return sideInputs;
}
/**
* Returns the side inputs of this {@link Combine}, tagged with the tag of the {@link
* PCollectionView}. The values of the returned map will be equal to the result of {@link
* #getSideInputs()}.
*/
@Override
public Map<TupleTag<?>, PValue> getAdditionalInputs() {
return PCollectionViews.toAdditionalInputs(sideInputs);
}
@Override
public PCollection<KV<K, OutputT>> expand(PCollection<KV<K, InputT>> input) {
return input
.apply(fewKeys ? GroupByKey.createWithFewKeys() : GroupByKey.create())
.apply(
Combine.<K, InputT, OutputT>groupedValues(fn, fnDisplayData)
.withSideInputs(sideInputs));
}
@Override
public void populateDisplayData(DisplayData.Builder builder) {
super.populateDisplayData(builder);
Combine.populateDisplayData(builder, fn, fnDisplayData);
}
}
/** Like {@link PerKey}, but sharding the combining of hot keys. */
public static class PerKeyWithHotKeyFanout<K, InputT, OutputT>
extends PTransform<PCollection<KV<K, InputT>>, PCollection<KV<K, OutputT>>> {
private final GlobalCombineFn<? super InputT, ?, OutputT> fn;
private final DisplayData.ItemSpec<? extends Class<?>> fnDisplayData;
private final SerializableFunction<? super K, Integer> hotKeyFanout;
private PerKeyWithHotKeyFanout(
GlobalCombineFn<? super InputT, ?, OutputT> fn,
DisplayData.ItemSpec<? extends Class<?>> fnDisplayData,
SerializableFunction<? super K, Integer> hotKeyFanout) {
this.fn = fn;
this.fnDisplayData = fnDisplayData;
this.hotKeyFanout = hotKeyFanout;
}
@Override
protected String getKindString() {
return String.format("Combine.perKeyWithFanout(%s)", NameUtils.approximateSimpleName(fn));
}
@Override
public PCollection<KV<K, OutputT>> expand(PCollection<KV<K, InputT>> input) {
return applyHelper(input);
}
private <AccumT> PCollection<KV<K, OutputT>> applyHelper(PCollection<KV<K, InputT>> input) {
// Name the accumulator type.
@SuppressWarnings("unchecked")
final GlobalCombineFn<InputT, AccumT, OutputT> typedFn =
(GlobalCombineFn<InputT, AccumT, OutputT>) this.fn;
if (!(input.getCoder() instanceof KvCoder)) {
throw new IllegalStateException(
"Expected input coder to be KvCoder, but was " + input.getCoder());
}
@SuppressWarnings("unchecked")
final KvCoder<K, InputT> inputCoder = (KvCoder<K, InputT>) input.getCoder();
final Coder<AccumT> accumCoder;
try {
accumCoder =
typedFn.getAccumulatorCoder(
input.getPipeline().getCoderRegistry(), inputCoder.getValueCoder());
} catch (CannotProvideCoderException e) {
throw new IllegalStateException("Unable to determine accumulator coder.", e);
}
Coder<InputOrAccum<InputT, AccumT>> inputOrAccumCoder =
new InputOrAccum.InputOrAccumCoder<>(inputCoder.getValueCoder(), accumCoder);
// A CombineFn's mergeAccumulator can be applied in a tree-like fashion.
// Here we shard the key using an integer nonce, combine on that partial
// set of values, then drop the nonce and do a final combine of the
// aggregates. We do this by splitting the original CombineFn into two,
// on that does addInput + merge and another that does merge + extract.
GlobalCombineFn<InputT, AccumT, AccumT> hotPreCombine;
GlobalCombineFn<InputOrAccum<InputT, AccumT>, AccumT, OutputT> postCombine;
if (typedFn instanceof CombineFn) {
final CombineFn<InputT, AccumT, OutputT> fn = (CombineFn<InputT, AccumT, OutputT>) typedFn;
hotPreCombine =
new CombineFn<InputT, AccumT, AccumT>() {
@Override
public AccumT createAccumulator() {
return fn.createAccumulator();
}
@Override
public AccumT addInput(AccumT accumulator, InputT value) {
return fn.addInput(accumulator, value);
}
@Override
public AccumT mergeAccumulators(Iterable<AccumT> accumulators) {
return fn.mergeAccumulators(accumulators);
}
@Override
public AccumT compact(AccumT accumulator) {
return fn.compact(accumulator);
}
@Override
public AccumT extractOutput(AccumT accumulator) {
return accumulator;
}
@Override
@SuppressWarnings("unchecked")
public Coder<AccumT> getAccumulatorCoder(
CoderRegistry registry, Coder<InputT> inputCoder)
throws CannotProvideCoderException {
return accumCoder;
}
@Override
public void populateDisplayData(DisplayData.Builder builder) {
builder.delegate(PerKeyWithHotKeyFanout.this);
}
};
postCombine =
new CombineFn<InputOrAccum<InputT, AccumT>, AccumT, OutputT>() {
@Override
public AccumT createAccumulator() {
return fn.createAccumulator();
}
@Override
public AccumT addInput(AccumT accumulator, InputOrAccum<InputT, AccumT> value) {
if (value.accum == null) {
return fn.addInput(accumulator, value.input);
} else {
return fn.mergeAccumulators(ImmutableList.of(accumulator, value.accum));
}
}
@Override
public AccumT mergeAccumulators(Iterable<AccumT> accumulators) {
return fn.mergeAccumulators(accumulators);
}
@Override
public AccumT compact(AccumT accumulator) {
return fn.compact(accumulator);
}
@Override
public OutputT extractOutput(AccumT accumulator) {
return fn.extractOutput(accumulator);
}
@Override
public Coder<OutputT> getDefaultOutputCoder(
CoderRegistry registry, Coder<InputOrAccum<InputT, AccumT>> accumulatorCoder)
throws CannotProvideCoderException {
return fn.getDefaultOutputCoder(registry, inputCoder.getValueCoder());
}
@Override
public Coder<AccumT> getAccumulatorCoder(
CoderRegistry registry, Coder<InputOrAccum<InputT, AccumT>> inputCoder)
throws CannotProvideCoderException {
return accumCoder;
}
@Override
public void populateDisplayData(DisplayData.Builder builder) {
builder.delegate(PerKeyWithHotKeyFanout.this);
}
};
} else if (typedFn instanceof CombineFnWithContext) {
final CombineFnWithContext<InputT, AccumT, OutputT> fnWithContext =
(CombineFnWithContext<InputT, AccumT, OutputT>) typedFn;
hotPreCombine =
new CombineFnWithContext<InputT, AccumT, AccumT>() {
@Override
public AccumT createAccumulator(Context c) {
return fnWithContext.createAccumulator(c);
}
@Override
public AccumT addInput(AccumT accumulator, InputT value, Context c) {
return fnWithContext.addInput(accumulator, value, c);
}
@Override
public AccumT mergeAccumulators(Iterable<AccumT> accumulators, Context c) {
return fnWithContext.mergeAccumulators(accumulators, c);
}
@Override
public AccumT compact(AccumT accumulator, Context c) {
return fnWithContext.compact(accumulator, c);
}
@Override
public AccumT extractOutput(AccumT accumulator, Context c) {
return accumulator;
}
@Override
@SuppressWarnings("unchecked")
public Coder<AccumT> getAccumulatorCoder(
CoderRegistry registry, Coder<InputT> inputCoder)
throws CannotProvideCoderException {
return accumCoder;
}
@Override
public void populateDisplayData(DisplayData.Builder builder) {
builder.delegate(PerKeyWithHotKeyFanout.this);
}
};
postCombine =
new CombineFnWithContext<InputOrAccum<InputT, AccumT>, AccumT, OutputT>() {
@Override
public AccumT createAccumulator(Context c) {
return fnWithContext.createAccumulator(c);
}
@Override
public AccumT addInput(
AccumT accumulator, InputOrAccum<InputT, AccumT> value, Context c) {
if (value.accum == null) {
return fnWithContext.addInput(accumulator, value.input, c);
} else {
return fnWithContext.mergeAccumulators(
ImmutableList.of(accumulator, value.accum), c);
}
}
@Override
public AccumT mergeAccumulators(Iterable<AccumT> accumulators, Context c) {
return fnWithContext.mergeAccumulators(accumulators, c);
}
@Override
public AccumT compact(AccumT accumulator, Context c) {
return fnWithContext.compact(accumulator, c);
}
@Override
public OutputT extractOutput(AccumT accumulator, Context c) {
return fnWithContext.extractOutput(accumulator, c);
}
@Override
public Coder<OutputT> getDefaultOutputCoder(
CoderRegistry registry, Coder<InputOrAccum<InputT, AccumT>> accumulatorCoder)
throws CannotProvideCoderException {
return fnWithContext.getDefaultOutputCoder(registry, inputCoder.getValueCoder());
}
@Override
public Coder<AccumT> getAccumulatorCoder(
CoderRegistry registry, Coder<InputOrAccum<InputT, AccumT>> inputCoder)
throws CannotProvideCoderException {
return accumCoder;
}
@Override
public void populateDisplayData(DisplayData.Builder builder) {
builder.delegate(PerKeyWithHotKeyFanout.this);
}
};
} else {
throw new IllegalStateException(
String.format("Unknown type of CombineFn: %s", typedFn.getClass()));
}
// Use the provided hotKeyFanout fn to split into "hot" and "cold" keys,
// augmenting the hot keys with a nonce.
final TupleTag<KV<KV<K, Integer>, InputT>> hot = new TupleTag<>();
final TupleTag<KV<K, InputT>> cold = new TupleTag<>();
PCollectionTuple split =
input.apply(
"AddNonce",
ParDo.of(
new DoFn<KV<K, InputT>, KV<K, InputT>>() {
transient int nonce;
@StartBundle
public void startBundle() {
// Spreading a hot key across all possible sub-keys for all bundles
// would defeat the goal of not overwhelming downstream reducers
// (as well as making less efficient use of PGBK combining tables).
// Instead, each bundle independently makes a consistent choice about
// which "shard" of a key to send its intermediate results.
nonce = ThreadLocalRandom.current().nextInt(Integer.MAX_VALUE);
}
@ProcessElement
public void processElement(
@Element KV<K, InputT> kv, MultiOutputReceiver receiver) {
int spread = hotKeyFanout.apply(kv.getKey());
if (spread <= 1) {
receiver.get(cold).output(kv);
} else {
receiver
.get(hot)
.output(KV.of(KV.of(kv.getKey(), nonce % spread), kv.getValue()));
}
}
})
.withOutputTags(cold, TupleTagList.of(hot)));
// The first level of combine should never use accumulating mode.
WindowingStrategy<?, ?> preCombineStrategy = input.getWindowingStrategy();
if (preCombineStrategy.getMode()
== WindowingStrategy.AccumulationMode.ACCUMULATING_FIRED_PANES) {
preCombineStrategy =
preCombineStrategy.withMode(WindowingStrategy.AccumulationMode.DISCARDING_FIRED_PANES);
}
// Combine the hot and cold keys separately.
PCollection<KV<K, InputOrAccum<InputT, AccumT>>> precombinedHot =
split
.get(hot)
.setCoder(
KvCoder.of(
KvCoder.of(inputCoder.getKeyCoder(), VarIntCoder.of()),
inputCoder.getValueCoder()))
.setWindowingStrategyInternal(preCombineStrategy)
.apply("PreCombineHot", Combine.perKey(hotPreCombine, fnDisplayData))
.apply(
"StripNonce",
MapElements.via(
new SimpleFunction<
KV<KV<K, Integer>, AccumT>, KV<K, InputOrAccum<InputT, AccumT>>>() {
@Override
public KV<K, InputOrAccum<InputT, AccumT>> apply(
KV<KV<K, Integer>, AccumT> elem) {
return KV.of(
elem.getKey().getKey(),
InputOrAccum.<InputT, AccumT>accum(elem.getValue()));
}
}))
.setCoder(KvCoder.of(inputCoder.getKeyCoder(), inputOrAccumCoder))
.apply(Window.remerge())
.setWindowingStrategyInternal(input.getWindowingStrategy());
PCollection<KV<K, InputOrAccum<InputT, AccumT>>> preprocessedCold =
split
.get(cold)
.setCoder(inputCoder)
.apply(
"PrepareCold",
MapElements.via(
new SimpleFunction<KV<K, InputT>, KV<K, InputOrAccum<InputT, AccumT>>>() {
@Override
public KV<K, InputOrAccum<InputT, AccumT>> apply(KV<K, InputT> element) {
return KV.of(
element.getKey(),
InputOrAccum.<InputT, AccumT>input(element.getValue()));
}
}))
.setCoder(KvCoder.of(inputCoder.getKeyCoder(), inputOrAccumCoder));
// Combine the union of the pre-processed hot and cold key results.
return PCollectionList.of(precombinedHot)
.and(preprocessedCold)
.apply(Flatten.pCollections())
.apply("PostCombine", Combine.perKey(postCombine, fnDisplayData));
}
@Override
public void populateDisplayData(DisplayData.Builder builder) {
super.populateDisplayData(builder);
Combine.populateDisplayData(builder, fn, fnDisplayData);
if (hotKeyFanout instanceof HasDisplayData) {
builder.include("hotKeyFanout", (HasDisplayData) hotKeyFanout);
}
builder.add(
DisplayData.item("fanoutFn", hotKeyFanout.getClass()).withLabel("Fanout Function"));
}
/**
* Used to store either an input or accumulator value, for flattening the hot and cold key
* paths.
*/
private static class InputOrAccum<InputT, AccumT> {
public final @Nullable InputT input;
public final @Nullable AccumT accum;
private InputOrAccum(@Nullable InputT input, @Nullable AccumT aggr) {
this.input = input;
this.accum = aggr;
}
public static <InputT, AccumT> InputOrAccum<InputT, AccumT> input(InputT input) {
return new InputOrAccum<>(input, null);
}
public static <InputT, AccumT> InputOrAccum<InputT, AccumT> accum(AccumT aggr) {
return new InputOrAccum<>(null, aggr);
}
private static class InputOrAccumCoder<InputT, AccumT>
extends StructuredCoder<InputOrAccum<InputT, AccumT>> {
private final Coder<InputT> inputCoder;
private final Coder<AccumT> accumCoder;
public InputOrAccumCoder(Coder<InputT> inputCoder, Coder<AccumT> accumCoder) {
this.inputCoder = inputCoder;
this.accumCoder = accumCoder;
}
@Override
public void encode(InputOrAccum<InputT, AccumT> value, OutputStream outStream)
throws CoderException, IOException {
encode(value, outStream, Coder.Context.NESTED);
}
@Override
public void encode(
InputOrAccum<InputT, AccumT> value, OutputStream outStream, Coder.Context context)
throws CoderException, IOException {
if (value.input != null) {
outStream.write(0);
inputCoder.encode(value.input, outStream, context);
} else {
outStream.write(1);
accumCoder.encode(value.accum, outStream, context);
}
}
@Override
public InputOrAccum<InputT, AccumT> decode(InputStream inStream)
throws CoderException, IOException {
return decode(inStream, Coder.Context.NESTED);
}
@Override
public InputOrAccum<InputT, AccumT> decode(InputStream inStream, Coder.Context context)
throws CoderException, IOException {
if (inStream.read() == 0) {
return InputOrAccum.input(inputCoder.decode(inStream, context));
} else {
return InputOrAccum.accum(accumCoder.decode(inStream, context));
}
}
@Override
public List<? extends Coder<?>> getCoderArguments() {
return ImmutableList.of(inputCoder, accumCoder);
}
@Override
public void verifyDeterministic() throws Coder.NonDeterministicException {
inputCoder.verifyDeterministic();
accumCoder.verifyDeterministic();
}
}
}
}
/////////////////////////////////////////////////////////////////////////////
/**
* {@code GroupedValues<K, InputT, OutputT>} takes a {@code PCollection<KV<K, Iterable<InputT>>>},
* such as the result of {@link GroupByKey}, applies a specified {@link CombineFn
* CombineFn&lt;InputT, AccumT, OutputT&gt;} to each of the input {@code KV<K, Iterable<InputT>>}
* elements to produce a combined output {@code KV<K, OutputT>} element, and returns a {@code
* PCollection<KV<K, OutputT>>} containing all the combined output elements. It is common for
* {@code InputT == OutputT}, but not required. Common combining functions include sums, mins,
* maxes, and averages of numbers, conjunctions and disjunctions of booleans, statistical
* aggregations, etc.
*
* <p>Example of use:
*
* <pre>{@code
* PCollection<KV<String, Integer>> pc = ...;
* PCollection<KV<String, Iterable<Integer>>> groupedByKey = pc.apply(
* GroupByKey.create());
* PCollection<KV<String, Integer>> sumByKey =
* groupedByKey.apply(Combine.groupedValues(
* Sum.ofIntegers()));
* }</pre>
*
* <p>See also {@link #perKey}/{@link PerKey Combine.PerKey}, which captures the common pattern of
* "combining by key" in a single easy-to-use {@code PTransform}.
*
* <p>Combining for different keys can happen in parallel. Moreover, combining of the {@code
* Iterable<InputT>} values associated a single key can happen in parallel, with different subsets
* of the values being combined separately, and their intermediate results combined further, in an
* arbitrary tree reduction pattern, until a single result value is produced for each key.
*
* <p>By default, the {@code Coder} of the keys of the output {@code PCollection<KV<K, OutputT>>}
* is that of the keys of the input {@code PCollection<KV<K, InputT>>}, and the {@code Coder} of
* the values of the output {@code PCollection<KV<K, OutputT>>} is inferred from the concrete type
* of the {@code CombineFn<InputT, AccumT, OutputT>}'s output type {@code OutputT}.
*
* <p>Each output element has the same timestamp and is in the same window as its corresponding
* input element, and the output {@code PCollection} has the same {@link
* org.apache.beam.sdk.transforms.windowing.WindowFn} associated with it as the input.
*
* <p>See also {@link #globally}/{@link Globally Combine.Globally}, which combines all the values
* in a {@code PCollection} into a single value in a {@code PCollection}.
*
* @param <K> type of input and output keys
* @param <InputT> type of input values
* @param <OutputT> type of output values
*/
public static class GroupedValues<K, InputT, OutputT>
extends PTransform<
PCollection<? extends KV<K, ? extends Iterable<InputT>>>, PCollection<KV<K, OutputT>>> {
private final GlobalCombineFn<? super InputT, ?, OutputT> fn;
private final DisplayData.ItemSpec<? extends Class<?>> fnDisplayData;
private final List<PCollectionView<?>> sideInputs;
private GroupedValues(
GlobalCombineFn<? super InputT, ?, OutputT> fn,
DisplayData.ItemSpec<? extends Class<?>> fnDisplayData) {
this.fn = SerializableUtils.clone(fn);
this.fnDisplayData = fnDisplayData;
this.sideInputs = ImmutableList.of();
}
private GroupedValues(
GlobalCombineFn<? super InputT, ?, OutputT> fn,
DisplayData.ItemSpec<? extends Class<?>> fnDisplayData,
List<PCollectionView<?>> sideInputs) {
this.fn = SerializableUtils.clone(fn);
this.fnDisplayData = fnDisplayData;
this.sideInputs = sideInputs;
}
public GroupedValues<K, InputT, OutputT> withSideInputs(PCollectionView<?>... sideInputs) {
return withSideInputs(Arrays.asList(sideInputs));
}
public GroupedValues<K, InputT, OutputT> withSideInputs(
Iterable<? extends PCollectionView<?>> sideInputs) {
return new GroupedValues<>(fn, fnDisplayData, ImmutableList.copyOf(sideInputs));
}
/** Returns the {@link GlobalCombineFn} used by this Combine operation. */
public GlobalCombineFn<? super InputT, ?, OutputT> getFn() {
return fn;
}
public List<PCollectionView<?>> getSideInputs() {
return sideInputs;
}
@Override
public PCollection<KV<K, OutputT>> expand(
PCollection<? extends KV<K, ? extends Iterable<InputT>>> input) {
PCollection<KV<K, OutputT>> output =
input.apply(
ParDo.of(
new DoFn<KV<K, ? extends Iterable<InputT>>, KV<K, OutputT>>() {
@ProcessElement
public void processElement(final ProcessContext c) {
K key = c.element().getKey();
OutputT output;
if (fn instanceof CombineFnWithContext) {
output =
((CombineFnWithContext<? super InputT, ?, OutputT>) fn)
.apply(
c.element().getValue(),
new CombineWithContext.Context() {
@Override
public PipelineOptions getPipelineOptions() {
return c.getPipelineOptions();
}
@Override
public <T> T sideInput(PCollectionView<T> view) {
return c.sideInput(view);
}
});
} else if (fn instanceof CombineFn) {
output =
((CombineFn<? super InputT, ?, OutputT>) fn)
.apply(c.element().getValue());
} else {
throw new IllegalStateException(
String.format("Unknown type of CombineFn: %s", fn.getClass()));
}
c.output(KV.of(key, output));
}
@Override
public void populateDisplayData(DisplayData.Builder builder) {
builder.delegate(Combine.GroupedValues.this);
}
})
.withSideInputs(sideInputs));
try {
KvCoder<K, InputT> kvCoder = getKvCoder(input.getCoder());
@SuppressWarnings("unchecked")
Coder<OutputT> outputValueCoder =
((GlobalCombineFn<InputT, ?, OutputT>) fn)
.getDefaultOutputCoder(
input.getPipeline().getCoderRegistry(), kvCoder.getValueCoder());
output.setCoder(KvCoder.of(kvCoder.getKeyCoder(), outputValueCoder));
} catch (CannotProvideCoderException exc) {
// let coder inference happen later, if it can
}
return output;
}
/**
* Returns the {@link CombineFn} bound to its coders.
*
* <p>For internal use.
*/
public AppliedCombineFn<? super K, ? super InputT, ?, OutputT> getAppliedFn(
CoderRegistry registry,
Coder<? extends KV<K, ? extends Iterable<InputT>>> inputCoder,
WindowingStrategy<?, ?> windowingStrategy) {
KvCoder<K, InputT> kvCoder = getKvCoder(inputCoder);
return AppliedCombineFn.withInputCoder(fn, registry, kvCoder, sideInputs, windowingStrategy);
}
private KvCoder<K, InputT> getKvCoder(
Coder<? extends KV<K, ? extends Iterable<InputT>>> inputCoder) {
if (!(inputCoder instanceof KvCoder)) {
throw new IllegalStateException("Combine.GroupedValues requires its input to use KvCoder");
}
@SuppressWarnings({"unchecked", "rawtypes"})
KvCoder<K, ? extends Iterable<InputT>> kvCoder = (KvCoder) inputCoder;
Coder<K> keyCoder = kvCoder.getKeyCoder();
Coder<? extends Iterable<InputT>> kvValueCoder = kvCoder.getValueCoder();
if (!(kvValueCoder instanceof IterableCoder)) {
throw new IllegalStateException(
"Combine.GroupedValues requires its input values to use " + "IterableCoder");
}
@SuppressWarnings("unchecked")
IterableCoder<InputT> inputValuesCoder = (IterableCoder<InputT>) kvValueCoder;
Coder<InputT> inputValueCoder = inputValuesCoder.getElemCoder();
return KvCoder.of(keyCoder, inputValueCoder);
}
@Override
public void populateDisplayData(DisplayData.Builder builder) {
super.populateDisplayData(builder);
Combine.populateDisplayData(builder, fn, fnDisplayData);
}
}
}