GroupJoinQueryOperator.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / Core / System / Linq / Parallel / QueryOperators / Binary / GroupJoinQueryOperator.cs / 1305376 / GroupJoinQueryOperator.cs
                        

                        
                            // ==++== 
//
//   Copyright (c) Microsoft Corporation.  All rights reserved.
//
// ==--== 
// =+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
// 
// GroupJoinQueryOperator.cs 
//
// [....] 
//
// =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

using System.Collections.Generic; 
using System.Diagnostics.Contracts;
using System.Threading; 
 
namespace System.Linq.Parallel
{ 
    /// 
    /// A group join operator takes a left query tree and a right query tree, and then yields
    /// the matching elements between the two. This can be used for outer joins, i.e. those
    /// where an outer element has no matching inner elements -- the result is just an empty 
    /// list. As with the join algorithm above, we currently use a hash join algorithm.
    ///  
    ///  
    /// 
    ///  
    /// 
    internal sealed class GroupJoinQueryOperator :  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, TOutput> m_resultSelector; // The result selection routine. 
        private readonly IEqualityComparer m_keyComparer; // An optional key comparison object.
 
        //----------------------------------------------------------------------------------------
        // Constructs a new join operator.
        //
 
        internal GroupJoinQueryOperator(ParallelQuery left, ParallelQuery right,
                                        Func leftKeySelector, 
                                        Func rightKeySelector, 
                                        Func, TOutput> 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);
        } 
 
        //---------------------------------------------------------------------------------------
        // Just opens the current operator, including opening the child and wrapping it with 
        // partitions as needed.
        //

        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); 
        }

        public override void WrapPartitionedStream(
            PartitionedStream leftStream, PartitionedStream rightStream, 
            IPartitionedStreamRecipient outputRecipient, bool preferStriping, QuerySettings settings)
        { 
            Contract.Assert(rightStream.PartitionCount == leftStream.PartitionCount); 
            int partitionCount = leftStream.PartitionCount;
 
            if (LeftChild.OutputOrdered)
            {
                WrapPartitionedStreamHelper(
                    ExchangeUtilities.HashRepartitionOrdered(leftStream, m_leftKeySelector, m_keyComparer, null, settings.CancellationState.MergedCancellationToken), 
                    rightStream, outputRecipient, partitionCount, settings.CancellationState.MergedCancellationToken);
            } 
            else 
            {
                WrapPartitionedStreamHelper( 
                    ExchangeUtilities.HashRepartition(leftStream, m_leftKeySelector, m_keyComparer, null, settings.CancellationState.MergedCancellationToken),
                    rightStream, outputRecipient, partitionCount, 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, int partitionCount, CancellationToken cancellationToken) 
        {
            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], null, m_resultSelector, m_keyComparer, 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
                .GroupJoin( 
                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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