Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / QueryOperators / Binary / ExceptQueryOperator.cs / 1305376 / ExceptQueryOperator.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== // =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ // // ExceptQueryOperator.cs // //[....] // // =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- using System.Collections.Generic; using System.Diagnostics.Contracts; using System.Threading; namespace System.Linq.Parallel { ////// Operator that yields the elements from the first data source that aren't in the second. /// This is known as the set relative complement, i.e. left - right. /// ///internal sealed class ExceptQueryOperator : BinaryQueryOperator { private readonly IEqualityComparer m_comparer; // An equality comparer. //---------------------------------------------------------------------------------------- // Constructs a new set except operator. // internal ExceptQueryOperator(ParallelQuery left, ParallelQuery right, IEqualityComparer comparer) :base(left, right) { Contract.Assert(left != null && right != null, "child data sources cannot be null"); m_comparer = comparer; m_outputOrdered = LeftChild.OutputOrdered; SetOrdinalIndex(OrdinalIndexState.Shuffled); } internal override QueryResults 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-partititioned. QueryResults leftChildResults = LeftChild.Open(settings, false); QueryResults rightChildResults = RightChild.Open(settings, false); return new BinaryQueryOperatorResults(leftChildResults, rightChildResults, this, settings, false); } public override void WrapPartitionedStream ( PartitionedStream leftStream, PartitionedStream rightStream, IPartitionedStreamRecipient outputRecipient, bool preferStriping, QuerySettings settings) { Contract.Assert(leftStream.PartitionCount == rightStream.PartitionCount); if (OutputOrdered) { WrapPartitionedStreamHelper ( ExchangeUtilities.HashRepartitionOrdered ( leftStream, null, null, m_comparer, settings.CancellationState.MergedCancellationToken), rightStream, outputRecipient, settings.CancellationState.MergedCancellationToken); } else { WrapPartitionedStreamHelper ( ExchangeUtilities.HashRepartition ( leftStream, null, null, m_comparer, settings.CancellationState.MergedCancellationToken), rightStream, outputRecipient, settings.CancellationState.MergedCancellationToken); } } //--------------------------------------------------------------------------------------- // This is a helper method. WrapPartitionedStream decides what type TLeftKey is going // to be, and then call this method with that key as a generic parameter. // private void WrapPartitionedStreamHelper ( PartitionedStream , TLeftKey> leftHashStream, PartitionedStream rightPartitionedStream, IPartitionedStreamRecipient outputRecipient, CancellationToken cancellationToken) { int partitionCount = leftHashStream.PartitionCount; PartitionedStream , int> rightHashStream = ExchangeUtilities.HashRepartition ( rightPartitionedStream, null, null, m_comparer, cancellationToken); PartitionedStream outputStream = new PartitionedStream (partitionCount, leftHashStream.KeyComparer, OrdinalIndexState.Shuffled); for (int i = 0; i < partitionCount; i++) { if (OutputOrdered) { outputStream[i] = new OrderedExceptQueryOperatorEnumerator ( leftHashStream[i], rightHashStream[i], m_comparer, leftHashStream.KeyComparer, cancellationToken); } else { outputStream[i] = (QueryOperatorEnumerator )(object) new ExceptQueryOperatorEnumerator (leftHashStream[i], rightHashStream[i], m_comparer, cancellationToken); } } outputRecipient.Receive(outputStream); } //--------------------------------------------------------------------------------------- // Returns an enumerable that represents the query executing sequentially. // internal override IEnumerable AsSequentialQuery(CancellationToken token) { IEnumerable wrappedLeftChild = CancellableEnumerable.Wrap(LeftChild.AsSequentialQuery(token), token); IEnumerable wrappedRightChild = CancellableEnumerable.Wrap(RightChild.AsSequentialQuery(token), token); return wrappedLeftChild.Except(wrappedRightChild, m_comparer); } //--------------------------------------------------------------------------------------- // Whether this operator performs a premature merge. // internal override bool LimitsParallelism { get { return false; } } //---------------------------------------------------------------------------------------- // This enumerator calculates the distinct set incrementally. It does this by maintaining // a history -- in the form of a set -- of all data already seen. It then only returns // elements that have not yet been seen. // class ExceptQueryOperatorEnumerator : QueryOperatorEnumerator { private QueryOperatorEnumerator , TLeftKey> m_leftSource; // Left data source. private QueryOperatorEnumerator , int> m_rightSource; // Right data source. private IEqualityComparer m_comparer; // A comparer used for equality checks/hash-coding. private Set m_hashLookup; // The hash lookup, used to produce the distinct set. private CancellationToken m_cancellationToken; private Shared m_outputLoopCount; //--------------------------------------------------------------------------------------- // Instantiates a new except query operator enumerator. // internal ExceptQueryOperatorEnumerator( QueryOperatorEnumerator , TLeftKey> leftSource, QueryOperatorEnumerator , int> rightSource, IEqualityComparer comparer, CancellationToken cancellationToken) { Contract.Assert(leftSource != null); Contract.Assert(rightSource != null); m_leftSource = leftSource; m_rightSource = rightSource; m_comparer = comparer; m_cancellationToken = cancellationToken; } //---------------------------------------------------------------------------------------- // Walks the two data sources, left and then right, to produce the distinct set // internal override bool MoveNext(ref TInputOutput currentElement, ref int currentKey) { Contract.Assert(m_leftSource != null); Contract.Assert(m_rightSource != null); // Build the set out of the left data source, if we haven't already. if (m_hashLookup == null) { m_outputLoopCount = new Shared (0); // @ m_hashLookup = new Set (m_comparer); Pair rightElement = default(Pair ); int rightKeyUnused = default(int); int i = 0; while (m_rightSource.MoveNext(ref rightElement, ref rightKeyUnused)) { if ((i++ & CancellationState.POLL_INTERVAL) == 0) CancellationState.ThrowIfCanceled(m_cancellationToken); m_hashLookup.Add(rightElement.First); } } // Now iterate over the right data source, looking for matches. Pair leftElement = default(Pair ); TLeftKey leftKeyUnused = default(TLeftKey); while (m_leftSource.MoveNext(ref leftElement, ref leftKeyUnused)) { if ((m_outputLoopCount.Value++ & CancellationState.POLL_INTERVAL) == 0) CancellationState.ThrowIfCanceled(m_cancellationToken); if (m_hashLookup.Add(leftElement.First)) { // This element has never been seen. Return it. currentElement = leftElement.First; #if DEBUG currentKey = unchecked((int)0xdeadbeef); #endif return true; } } return false; } protected override void Dispose(bool disposing) { Contract.Assert(m_leftSource != null && m_rightSource != null); m_leftSource.Dispose(); m_rightSource.Dispose(); } } class OrderedExceptQueryOperatorEnumerator : QueryOperatorEnumerator { private QueryOperatorEnumerator , TLeftKey> m_leftSource; // Left data source. private QueryOperatorEnumerator , int> m_rightSource; // Right data source. private IEqualityComparer m_comparer; // A comparer used for equality checks/hash-coding. private IComparer m_leftKeyComparer; // A comparer for order keys. private IEnumerator , Pair >> m_outputEnumerator; // The enumerator output elements + order keys. private CancellationToken m_cancellationToken; //---------------------------------------------------------------------------------------- // Instantiates a new except query operator enumerator. // internal OrderedExceptQueryOperatorEnumerator( QueryOperatorEnumerator , TLeftKey> leftSource, QueryOperatorEnumerator , int> rightSource, IEqualityComparer comparer, IComparer leftKeyComparer, CancellationToken cancellationToken) { Contract.Assert(leftSource != null); Contract.Assert(rightSource != null); m_leftSource = leftSource; m_rightSource = rightSource; m_comparer = comparer; m_leftKeyComparer = leftKeyComparer; m_cancellationToken = cancellationToken; } //--------------------------------------------------------------------------------------- // Walks the two data sources, left and then right, to produce the distinct set // internal override bool MoveNext(ref TInputOutput currentElement, ref TLeftKey currentKey) { Contract.Assert(m_leftSource != null); Contract.Assert(m_rightSource != null); // Build the set out of the left data source, if we haven't already. if (m_outputEnumerator == null) { // @ Set rightLookup = new Set (m_comparer); Pair rightElement = default(Pair ); int rightKeyUnused = default(int); int i=0; while (m_rightSource.MoveNext(ref rightElement, ref rightKeyUnused)) { if ((i++ & CancellationState.POLL_INTERVAL) == 0) CancellationState.ThrowIfCanceled(m_cancellationToken); rightLookup.Add(rightElement.First); } var leftLookup = new Dictionary , Pair >( new WrapperEqualityComparer (m_comparer)); Pair leftElement = default(Pair ); TLeftKey leftKey = default(TLeftKey); while (m_leftSource.MoveNext(ref leftElement, ref leftKey)) { if ((i++ & CancellationState.POLL_INTERVAL) == 0) CancellationState.ThrowIfCanceled(m_cancellationToken); if (rightLookup.Contains(leftElement.First)) { continue; } Pair oldEntry; Wrapper wrappedLeftElement = new Wrapper (leftElement.First); if (!leftLookup.TryGetValue(wrappedLeftElement, out oldEntry) || m_leftKeyComparer.Compare(leftKey, oldEntry.Second) < 0) { // For each "elem" value, we store the smallest key, and the element value that had that key. // Note that even though two element values are "equal" according to the EqualityComparer, // we still cannot choose arbitrarily which of the two to yield. leftLookup[wrappedLeftElement] = new Pair (leftElement.First, leftKey); } } m_outputEnumerator = leftLookup.GetEnumerator(); } if (m_outputEnumerator.MoveNext()) { Pair currentPair = m_outputEnumerator.Current.Value; currentElement = currentPair.First; currentKey = currentPair.Second; return true; } return false; } protected override void Dispose(bool disposing) { Contract.Assert(m_leftSource != null && m_rightSource != null); m_leftSource.Dispose(); m_rightSource.Dispose(); } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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