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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
//
// UnionQueryOperator.cs
//
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
using System.Collections.Generic;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Threading;
namespace System.Linq.Parallel
{
/// <summary>
/// Operator that yields the union of two data sources.
/// </summary>
/// <typeparam name="TInputOutput"></typeparam>
internal sealed class UnionQueryOperator<TInputOutput> :
BinaryQueryOperator<TInputOutput, TInputOutput, TInputOutput>
{
private readonly IEqualityComparer<TInputOutput>? _comparer; // An equality comparer.
//---------------------------------------------------------------------------------------
// Constructs a new union operator.
//
internal UnionQueryOperator(ParallelQuery<TInputOutput> left, ParallelQuery<TInputOutput> right, IEqualityComparer<TInputOutput>? comparer)
: base(left, right)
{
Debug.Assert(left != null && right != null, "child data sources cannot be null");
_comparer = comparer;
_outputOrdered = LeftChild.OutputOrdered || RightChild.OutputOrdered;
}
//---------------------------------------------------------------------------------------
// Just opens the current operator, including opening the child and wrapping it with
// partitions as needed.
//
internal override QueryResults<TInputOutput> Open(
QuerySettings settings, bool preferStriping)
{
// We just open our child operators, left and then right. Do not propagate the preferStriping value, but
// instead explicitly set it to false. Regardless of whether the parent prefers striping or range
// partitioning, the output will be hash-partitioned.
QueryResults<TInputOutput> leftChildResults = LeftChild.Open(settings, false);
QueryResults<TInputOutput> rightChildResults = RightChild.Open(settings, false);
return new BinaryQueryOperatorResults(leftChildResults, rightChildResults, this, settings, false);
}
public override void WrapPartitionedStream<TLeftKey, TRightKey>(
PartitionedStream<TInputOutput, TLeftKey> leftStream, PartitionedStream<TInputOutput, TRightKey> rightStream,
IPartitionedStreamRecipient<TInputOutput> outputRecipient, bool preferStriping, QuerySettings settings)
{
Debug.Assert(leftStream.PartitionCount == rightStream.PartitionCount);
int partitionCount = leftStream.PartitionCount;
// Wrap both child streams with hash repartition
if (LeftChild.OutputOrdered)
{
PartitionedStream<Pair<TInputOutput, NoKeyMemoizationRequired>, TLeftKey> leftHashStream =
ExchangeUtilities.HashRepartitionOrdered<TInputOutput, NoKeyMemoizationRequired, TLeftKey>(
leftStream, null, null, _comparer, settings.CancellationState.MergedCancellationToken);
WrapPartitionedStreamFixedLeftType<TLeftKey, TRightKey>(
leftHashStream, rightStream, outputRecipient, partitionCount, settings.CancellationState.MergedCancellationToken);
}
else
{
PartitionedStream<Pair<TInputOutput, NoKeyMemoizationRequired>, int> leftHashStream =
ExchangeUtilities.HashRepartition<TInputOutput, NoKeyMemoizationRequired, TLeftKey>(
leftStream, null, null, _comparer, settings.CancellationState.MergedCancellationToken);
WrapPartitionedStreamFixedLeftType<int, TRightKey>(
leftHashStream, rightStream, outputRecipient, partitionCount, settings.CancellationState.MergedCancellationToken);
}
}
//---------------------------------------------------------------------------------------
// A helper method that allows WrapPartitionedStream to fix the TLeftKey type parameter.
//
private void WrapPartitionedStreamFixedLeftType<TLeftKey, TRightKey>(
PartitionedStream<Pair<TInputOutput, NoKeyMemoizationRequired>, TLeftKey> leftHashStream, PartitionedStream<TInputOutput, TRightKey> rightStream,
IPartitionedStreamRecipient<TInputOutput> outputRecipient, int partitionCount, CancellationToken cancellationToken)
{
if (RightChild.OutputOrdered)
{
PartitionedStream<Pair<TInputOutput, NoKeyMemoizationRequired>, TRightKey> rightHashStream =
ExchangeUtilities.HashRepartitionOrdered<TInputOutput, NoKeyMemoizationRequired, TRightKey>(
rightStream, null, null, _comparer, cancellationToken);
WrapPartitionedStreamFixedBothTypes<TLeftKey, TRightKey>(
leftHashStream, rightHashStream, outputRecipient, partitionCount, cancellationToken);
}
else
{
PartitionedStream<Pair<TInputOutput, NoKeyMemoizationRequired>, int> rightHashStream =
ExchangeUtilities.HashRepartition<TInputOutput, NoKeyMemoizationRequired, TRightKey>(
rightStream, null, null, _comparer, cancellationToken);
WrapPartitionedStreamFixedBothTypes<TLeftKey, int>(
leftHashStream, rightHashStream, outputRecipient, partitionCount, cancellationToken);
}
}
//---------------------------------------------------------------------------------------
// A helper method that allows WrapPartitionedStreamHelper to fix the TRightKey type parameter.
//
private void WrapPartitionedStreamFixedBothTypes<TLeftKey, TRightKey>(
PartitionedStream<Pair<TInputOutput, NoKeyMemoizationRequired>, TLeftKey> leftHashStream,
PartitionedStream<Pair<TInputOutput, NoKeyMemoizationRequired>, TRightKey> rightHashStream,
IPartitionedStreamRecipient<TInputOutput> outputRecipient, int partitionCount,
CancellationToken cancellationToken)
{
if (LeftChild.OutputOrdered || RightChild.OutputOrdered)
{
IComparer<ConcatKey<TLeftKey, TRightKey>> compoundKeyComparer =
ConcatKey<TLeftKey, TRightKey>.MakeComparer(leftHashStream.KeyComparer, rightHashStream.KeyComparer);
PartitionedStream<TInputOutput, ConcatKey<TLeftKey, TRightKey>> outputStream =
new PartitionedStream<TInputOutput, ConcatKey<TLeftKey, TRightKey>>(partitionCount, compoundKeyComparer, OrdinalIndexState.Shuffled);
for (int i = 0; i < partitionCount; i++)
{
outputStream[i] = new OrderedUnionQueryOperatorEnumerator<TLeftKey, TRightKey>(
leftHashStream[i], rightHashStream[i], LeftChild.OutputOrdered, RightChild.OutputOrdered,
_comparer, compoundKeyComparer, cancellationToken);
}
outputRecipient.Receive(outputStream);
}
else
{
PartitionedStream<TInputOutput, int> outputStream =
new PartitionedStream<TInputOutput, int>(partitionCount, Util.GetDefaultComparer<int>(), OrdinalIndexState.Shuffled);
for (int i = 0; i < partitionCount; i++)
{
outputStream[i] = new UnionQueryOperatorEnumerator<TLeftKey, TRightKey>(
leftHashStream[i], rightHashStream[i], _comparer, cancellationToken);
}
outputRecipient.Receive(outputStream);
}
}
//---------------------------------------------------------------------------------------
// Returns an enumerable that represents the query executing sequentially.
//
internal override IEnumerable<TInputOutput> AsSequentialQuery(CancellationToken token)
{
IEnumerable<TInputOutput> wrappedLeftChild = CancellableEnumerable.Wrap(LeftChild.AsSequentialQuery(token), token);
IEnumerable<TInputOutput> wrappedRightChild = CancellableEnumerable.Wrap(RightChild.AsSequentialQuery(token), token);
return wrappedLeftChild.Union(wrappedRightChild, _comparer);
}
//---------------------------------------------------------------------------------------
// Whether this operator performs a premature merge that would not be performed in
// a similar sequential operation (i.e., in LINQ to Objects).
//
internal override bool LimitsParallelism
{
get { return false; }
}
//---------------------------------------------------------------------------------------
// This enumerator performs the union operation incrementally. It does this by maintaining
// a history -- in the form of a set -- of all data already seen. It is careful not to
// return any duplicates.
//
private sealed class UnionQueryOperatorEnumerator<TLeftKey, TRightKey> : QueryOperatorEnumerator<TInputOutput, int>
{
private QueryOperatorEnumerator<Pair<TInputOutput, NoKeyMemoizationRequired>, TLeftKey>? _leftSource; // Left data source.
private QueryOperatorEnumerator<Pair<TInputOutput, NoKeyMemoizationRequired>, TRightKey>? _rightSource; // Right data source.
private HashSet<TInputOutput>? _hashLookup; // The hash lookup, used to produce the union.
private readonly CancellationToken _cancellationToken;
private Shared<int>? _outputLoopCount;
private readonly IEqualityComparer<TInputOutput>? _comparer;
//---------------------------------------------------------------------------------------
// Instantiates a new union operator.
//
internal UnionQueryOperatorEnumerator(
QueryOperatorEnumerator<Pair<TInputOutput, NoKeyMemoizationRequired>, TLeftKey> leftSource,
QueryOperatorEnumerator<Pair<TInputOutput, NoKeyMemoizationRequired>, TRightKey> rightSource,
IEqualityComparer<TInputOutput>? comparer,
CancellationToken cancellationToken)
{
Debug.Assert(leftSource != null);
Debug.Assert(rightSource != null);
_leftSource = leftSource;
_rightSource = rightSource;
_comparer = comparer;
_cancellationToken = cancellationToken;
}
//---------------------------------------------------------------------------------------
// Walks the two data sources, left and then right, to produce the union.
//
internal override bool MoveNext([MaybeNullWhen(false), AllowNull] ref TInputOutput currentElement, ref int currentKey)
{
if (_hashLookup == null)
{
_hashLookup = new HashSet<TInputOutput>(_comparer);
_outputLoopCount = new Shared<int>(0);
}
Debug.Assert(_hashLookup != null);
// Enumerate the left and then right data source. When each is done, we set the
// field to null so we will skip it upon subsequent calls to MoveNext.
if (_leftSource != null)
{
// Iterate over this set's elements until we find a unique element.
TLeftKey keyUnused = default(TLeftKey)!;
Pair<TInputOutput, NoKeyMemoizationRequired> currentLeftElement = default(Pair<TInputOutput, NoKeyMemoizationRequired>);
int i = 0;
while (_leftSource.MoveNext(ref currentLeftElement, ref keyUnused))
{
if ((i++ & CancellationState.POLL_INTERVAL) == 0)
_cancellationToken.ThrowIfCancellationRequested();
// We ensure we never return duplicates by tracking them in our set.
if (_hashLookup.Add(currentLeftElement.First))
{
#if DEBUG
currentKey = unchecked((int)0xdeadbeef);
#endif
currentElement = currentLeftElement.First;
return true;
}
}
_leftSource.Dispose();
_leftSource = null;
}
if (_rightSource != null)
{
// Iterate over this set's elements until we find a unique element.
TRightKey keyUnused = default(TRightKey)!;
Pair<TInputOutput, NoKeyMemoizationRequired> currentRightElement = default(Pair<TInputOutput, NoKeyMemoizationRequired>);
while (_rightSource.MoveNext(ref currentRightElement, ref keyUnused))
{
Debug.Assert(_outputLoopCount != null);
if ((_outputLoopCount.Value++ & CancellationState.POLL_INTERVAL) == 0)
_cancellationToken.ThrowIfCancellationRequested();
// We ensure we never return duplicates by tracking them in our set.
if (_hashLookup.Add(currentRightElement.First))
{
#if DEBUG
currentKey = unchecked((int)0xdeadbeef);
#endif
currentElement = currentRightElement.First;
return true;
}
}
_rightSource.Dispose();
_rightSource = null;
}
return false;
}
protected override void Dispose(bool disposing)
{
_leftSource?.Dispose();
_rightSource?.Dispose();
}
}
private sealed class OrderedUnionQueryOperatorEnumerator<TLeftKey, TRightKey> : QueryOperatorEnumerator<TInputOutput, ConcatKey<TLeftKey, TRightKey>>
{
private readonly QueryOperatorEnumerator<Pair<TInputOutput, NoKeyMemoizationRequired>, TLeftKey> _leftSource; // Left data source.
private readonly QueryOperatorEnumerator<Pair<TInputOutput, NoKeyMemoizationRequired>, TRightKey> _rightSource; // Right data source.
private readonly IComparer<ConcatKey<TLeftKey, TRightKey>> _keyComparer; // Comparer for compound order keys.
#pragma warning disable CA1859
private IEnumerator<KeyValuePair<Wrapper<TInputOutput>, Pair<TInputOutput, ConcatKey<TLeftKey, TRightKey>>>>? _outputEnumerator; // Enumerator over the output of the union.
#pragma warning restore
private readonly bool _leftOrdered; // Whether the left data source is ordered.
private readonly bool _rightOrdered; // Whether the right data source is ordered.
private readonly IEqualityComparer<TInputOutput>? _comparer; // Comparer for the elements.
private readonly CancellationToken _cancellationToken;
//---------------------------------------------------------------------------------------
// Instantiates a new union operator.
//
internal OrderedUnionQueryOperatorEnumerator(
QueryOperatorEnumerator<Pair<TInputOutput, NoKeyMemoizationRequired>, TLeftKey> leftSource,
QueryOperatorEnumerator<Pair<TInputOutput, NoKeyMemoizationRequired>, TRightKey> rightSource,
bool leftOrdered, bool rightOrdered, IEqualityComparer<TInputOutput>? comparer, IComparer<ConcatKey<TLeftKey, TRightKey>> keyComparer,
CancellationToken cancellationToken)
{
Debug.Assert(leftSource != null);
Debug.Assert(rightSource != null);
_leftSource = leftSource;
_rightSource = rightSource;
_keyComparer = keyComparer;
_leftOrdered = leftOrdered;
_rightOrdered = rightOrdered;
_comparer = comparer ?? EqualityComparer<TInputOutput>.Default;
_cancellationToken = cancellationToken;
}
//---------------------------------------------------------------------------------------
// Walks the two data sources, left and then right, to produce the union.
//
internal override bool MoveNext([MaybeNullWhen(false), AllowNull] ref TInputOutput currentElement, ref ConcatKey<TLeftKey, TRightKey> currentKey)
{
Debug.Assert(_leftSource != null);
Debug.Assert(_rightSource != null);
if (_outputEnumerator == null)
{
IEqualityComparer<Wrapper<TInputOutput>> wrapperComparer = new WrapperEqualityComparer<TInputOutput>(_comparer);
Dictionary<Wrapper<TInputOutput>, Pair<TInputOutput, ConcatKey<TLeftKey, TRightKey>>> union =
new Dictionary<Wrapper<TInputOutput>, Pair<TInputOutput, ConcatKey<TLeftKey, TRightKey>>>(wrapperComparer);
Pair<TInputOutput, NoKeyMemoizationRequired> elem = default(Pair<TInputOutput, NoKeyMemoizationRequired>);
TLeftKey leftKey = default(TLeftKey)!;
int i = 0;
while (_leftSource.MoveNext(ref elem, ref leftKey))
{
if ((i++ & CancellationState.POLL_INTERVAL) == 0)
_cancellationToken.ThrowIfCancellationRequested();
ConcatKey<TLeftKey, TRightKey> key =
ConcatKey<TLeftKey, TRightKey>.MakeLeft(_leftOrdered ? leftKey : default);
Pair<TInputOutput, ConcatKey<TLeftKey, TRightKey>> oldEntry;
Wrapper<TInputOutput> wrappedElem = new Wrapper<TInputOutput>(elem.First);
if (!union.TryGetValue(wrappedElem, out oldEntry) || _keyComparer.Compare(key, oldEntry.Second) < 0)
{
union[wrappedElem] = new Pair<TInputOutput, ConcatKey<TLeftKey, TRightKey>>(elem.First, key);
}
}
TRightKey rightKey = default(TRightKey)!;
while (_rightSource.MoveNext(ref elem, ref rightKey))
{
if ((i++ & CancellationState.POLL_INTERVAL) == 0)
_cancellationToken.ThrowIfCancellationRequested();
ConcatKey<TLeftKey, TRightKey> key =
ConcatKey<TLeftKey, TRightKey>.MakeRight(_rightOrdered ? rightKey : default);
Pair<TInputOutput, ConcatKey<TLeftKey, TRightKey>> oldEntry;
Wrapper<TInputOutput> wrappedElem = new Wrapper<TInputOutput>(elem.First);
if (!union.TryGetValue(wrappedElem, out oldEntry) || _keyComparer.Compare(key, oldEntry.Second) < 0)
{
union[wrappedElem] = new Pair<TInputOutput, ConcatKey<TLeftKey, TRightKey>>(elem.First, key);
}
}
_outputEnumerator = union.GetEnumerator();
}
if (_outputEnumerator.MoveNext())
{
Pair<TInputOutput, ConcatKey<TLeftKey, TRightKey>> current = _outputEnumerator.Current.Value;
currentElement = current.First;
currentKey = current.Second;
return true;
}
return false;
}
protected override void Dispose(bool disposing)
{
Debug.Assert(_leftSource != null && _rightSource != null);
_leftSource.Dispose();
_rightSource.Dispose();
}
}
}
}
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