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/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / QueryOperators / Binary / JoinQueryOperator.cs / 1305376 / JoinQueryOperator.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== // =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ // // JoinQueryOperator.cs // //[....] // // =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- using System.Collections.Generic; using System.Diagnostics.Contracts; using System.Threading; namespace System.Linq.Parallel { ////// A join operator takes a left query tree and a right query tree, and then yields the /// matching pairs between the two. LINQ supports equi-key-based joins. Hence, a key- /// selection function for the left and right data types will yield keys of the same /// type for both. We then merely have to match elements from the left with elements from /// the right that have the same exact key. Note that this is an inner join. In other /// words, outer elements with no matching inner elements do not appear in the output. /// /// @ internal sealed class JoinQueryOperator : BinaryQueryOperator { private readonly Func m_leftKeySelector; // The key selection routine for the outer (left) data source. private readonly Func m_rightKeySelector; // The key selection routine for the inner (right) data source. private readonly Func m_resultSelector; // The result selection routine. private readonly IEqualityComparer m_keyComparer; // An optional key comparison object. //---------------------------------------------------------------------------------------- // Constructs a new join operator. // internal JoinQueryOperator(ParallelQuery left, ParallelQuery right, Func leftKeySelector, Func rightKeySelector, Func resultSelector, IEqualityComparer keyComparer) :base(left, right) { Contract.Assert(left != null && right != null, "child data sources cannot be null"); Contract.Assert(leftKeySelector != null, "left key selector must not be null"); Contract.Assert(rightKeySelector != null, "right key selector must not be null"); Contract.Assert(resultSelector != null, "need a result selector function"); m_leftKeySelector = leftKeySelector; m_rightKeySelector = rightKeySelector; m_resultSelector = resultSelector; m_keyComparer = keyComparer; m_outputOrdered = LeftChild.OutputOrdered; SetOrdinalIndex(OrdinalIndexState.Shuffled); } public override void WrapPartitionedStream ( PartitionedStream leftStream, PartitionedStream rightStream, IPartitionedStreamRecipient outputRecipient, bool preferStriping, QuerySettings settings) { Contract.Assert(rightStream.PartitionCount == leftStream.PartitionCount); if (LeftChild.OutputOrdered) { WrapPartitionedStreamHelper ( ExchangeUtilities.HashRepartitionOrdered(leftStream, m_leftKeySelector, m_keyComparer, null, settings.CancellationState.MergedCancellationToken), rightStream, outputRecipient, settings.CancellationState.MergedCancellationToken); } else { WrapPartitionedStreamHelper ( ExchangeUtilities.HashRepartition(leftStream, m_leftKeySelector, m_keyComparer, null, 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, m_rightKeySelector, m_keyComparer, null, cancellationToken); PartitionedStream outputStream = new PartitionedStream ( partitionCount, leftHashStream.KeyComparer, OrdinalIndexState); for (int i = 0; i < partitionCount; i++) { outputStream[i] = new HashJoinQueryOperatorEnumerator ( leftHashStream[i], rightHashStream[i], m_resultSelector, null, m_keyComparer, cancellationToken); } outputRecipient.Receive(outputStream); } internal override QueryResults Open(QuerySettings settings, bool preferStriping) { QueryResults leftResults = LeftChild.Open(settings, false); QueryResults rightResults = RightChild.Open(settings, false); return new BinaryQueryOperatorResults(leftResults, rightResults, this, settings, false); } //--------------------------------------------------------------------------------------- // 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.Join( wrappedRightChild, m_leftKeySelector, m_rightKeySelector, m_resultSelector, m_keyComparer); } //--------------------------------------------------------------------------------------- // Whether this operator performs a premature merge. // internal override bool LimitsParallelism { get { return false; } } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007.
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