JoinQueryOperator.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 / 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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