UnionQueryOperator.cs source code in C# .NET

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Code:

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

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

using System.Collections.Generic; 
using System.Diagnostics.Contracts;
using System.Threading; 
 
namespace System.Linq.Parallel
{ 
    /// 
    /// Operator that yields the union of two data sources.
    /// 
    ///  
    internal sealed class UnionQueryOperator :
        BinaryQueryOperator 
    { 

        private readonly IEqualityComparer m_comparer; // An equality comparer. 

        //----------------------------------------------------------------------------------------
        // Constructs a new union operator.
        // 

        internal UnionQueryOperator(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 || RightChild.OutputOrdered;
        } 

        //--------------------------------------------------------------------------------------- 
        // Just opens the current operator, including opening the child and wrapping it with 
        // partitions as needed.
        // 

        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); 
            int partitionCount = leftStream.PartitionCount;

            // Wrap both child streams with hash repartition
 
            if (LeftChild.OutputOrdered)
            { 
                PartitionedStream, TLeftKey> leftHashStream = 
                    ExchangeUtilities.HashRepartitionOrdered(
                        leftStream, null, null, m_comparer, settings.CancellationState.MergedCancellationToken); 

                WrapPartitionedStreamFixedLeftType(
                    leftHashStream, rightStream, outputRecipient, partitionCount, settings.CancellationState.MergedCancellationToken);
            } 
            else
            { 
                PartitionedStream, int> leftHashStream = 
                    ExchangeUtilities.HashRepartition(
                        leftStream, null, null, m_comparer, settings.CancellationState.MergedCancellationToken); 

                WrapPartitionedStreamFixedLeftType(
                    leftHashStream, rightStream, outputRecipient, partitionCount, settings.CancellationState.MergedCancellationToken);
            } 
        }
 
        //--------------------------------------------------------------------------------------- 
        // A helper method that allows WrapPartitionedStream to fix the TLeftKey type parameter.
        // 

        private void WrapPartitionedStreamFixedLeftType(
            PartitionedStream, TLeftKey> leftHashStream, PartitionedStream rightStream,
            IPartitionedStreamRecipient outputRecipient, int partitionCount, CancellationToken cancellationToken) 
        {
            if (RightChild.OutputOrdered) 
            { 
                PartitionedStream, TRightKey> rightHashStream =
                    ExchangeUtilities.HashRepartitionOrdered( 
                        rightStream, null, null, m_comparer, cancellationToken);

                WrapPartitionedStreamFixedBothTypes(
                    leftHashStream, rightHashStream, outputRecipient, partitionCount, cancellationToken); 
            }
            else 
            { 
                PartitionedStream, int> rightHashStream =
                    ExchangeUtilities.HashRepartition( 
                        rightStream, null, null, m_comparer, cancellationToken);

                WrapPartitionedStreamFixedBothTypes(
                    leftHashStream, rightHashStream, outputRecipient, partitionCount, cancellationToken); 
            }
        } 
 
        //---------------------------------------------------------------------------------------
        // A helper method that allows WrapPartitionedStreamHelper to fix the TRightKey type parameter. 
        //

        private void WrapPartitionedStreamFixedBothTypes(
            PartitionedStream, TLeftKey> leftHashStream, 
            PartitionedStream, TRightKey> rightHashStream,
            IPartitionedStreamRecipient outputRecipient, int partitionCount, 
            CancellationToken cancellationToken) 
        {
            if (LeftChild.OutputOrdered || RightChild.OutputOrdered) 
            {
                IComparer> compoundKeyComparer =
                    ConcatKey.MakeComparer(leftHashStream.KeyComparer, rightHashStream.KeyComparer);
 
                PartitionedStream> outputStream =
                    new PartitionedStream>(partitionCount, compoundKeyComparer, OrdinalIndexState.Shuffled); 
 
                for (int i = 0; i < partitionCount; i++)
                { 
                    outputStream[i] = new OrderedUnionQueryOperatorEnumerator(
                        leftHashStream[i], rightHashStream[i], LeftChild.OutputOrdered, RightChild.OutputOrdered,
                        m_comparer, compoundKeyComparer, cancellationToken);
                } 

                outputRecipient.Receive(outputStream); 
            } 
            else
            { 
                PartitionedStream outputStream =
                    new PartitionedStream(partitionCount, Util.GetDefaultComparer(), OrdinalIndexState.Shuffled);

                for (int i = 0; i < partitionCount; i++) 
                {
                    outputStream[i] = new UnionQueryOperatorEnumerator( 
                        leftHashStream[i], rightHashStream[i], 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.Union(wrappedRightChild, m_comparer);
        } 
 
        //---------------------------------------------------------------------------------------
        // Whether this operator performs a premature merge. 
        //

        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.
        //
 
        class UnionQueryOperatorEnumerator : QueryOperatorEnumerator
        { 
 
            private QueryOperatorEnumerator, TLeftKey> m_leftSource; // Left data source.
            private QueryOperatorEnumerator, TRightKey> m_rightSource; // Right data source. 
            private readonly int m_partitionIndex; // The current partition.
            private Set m_hashLookup; // The hash lookup, used to produce the union.
            private CancellationToken m_cancellationToken;
            private Shared m_outputLoopCount; 
            private readonly IEqualityComparer m_comparer;
 
            //---------------------------------------------------------------------------------------- 
            // Instantiates a new union operator.
            // 

            internal UnionQueryOperatorEnumerator(
                QueryOperatorEnumerator, TLeftKey> leftSource,
                QueryOperatorEnumerator, TRightKey> rightSource, 
                int partitionIndex, IEqualityComparer comparer,
                CancellationToken cancellationToken) 
            { 
                Contract.Assert(leftSource != null);
                Contract.Assert(rightSource != null); 

                m_leftSource = leftSource;
                m_rightSource = rightSource;
                m_partitionIndex = partitionIndex; 
                // @
                m_comparer = comparer; 
                m_cancellationToken = cancellationToken; 
            }
 
            //---------------------------------------------------------------------------------------
            // Walks the two data sources, left and then right, to produce the union.
            //
 
            internal override bool MoveNext(ref TInputOutput currentElement, ref int currentKey)
            { 
                if (m_hashLookup == null) 
                {
                    m_hashLookup = new Set(m_comparer); 
                    m_outputLoopCount = new Shared(0);
                }

                Contract.Assert(m_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 (m_leftSource != null)
                { 
                    // Iterate over this set's elements until we find a unique element.
                    TLeftKey keyUnused = default(TLeftKey);
                    Pair currentLeftElement = default(Pair);
 
                    int i = 0;
                    while (m_leftSource.MoveNext(ref currentLeftElement, ref keyUnused)) 
                    { 
                        if ((i++ & CancellationState.POLL_INTERVAL) == 0)
                            CancellationState.ThrowIfCanceled(m_cancellationToken); 

                        // We ensure we never return duplicates by tracking them in our set.
                        if (m_hashLookup.Add(currentLeftElement.First))
                        { 
#if DEBUG
                            currentKey = unchecked((int)0xdeadbeef); 
#endif 
                            currentElement = currentLeftElement.First;
                            return true; 
                        }
                    }

                    m_leftSource.Dispose(); 
                    m_leftSource = null;
                } 
 

                if (m_rightSource != null) 
                {
                    // Iterate over this set's elements until we find a unique element.
                    TRightKey keyUnused = default(TRightKey);
                    Pair currentRightElement = default(Pair); 

                    while (m_rightSource.MoveNext(ref currentRightElement, ref keyUnused)) 
                    { 
                        if ((m_outputLoopCount.Value++ & CancellationState.POLL_INTERVAL) == 0)
                            CancellationState.ThrowIfCanceled(m_cancellationToken); 

                        // We ensure we never return duplicates by tracking them in our set.
                        if (m_hashLookup.Add(currentRightElement.First))
                        { 
#if DEBUG
                            currentKey = unchecked((int)0xdeadbeef); 
#endif 
                            currentElement = currentRightElement.First;
                            return true; 
                        }
                    }

                    m_rightSource.Dispose(); 
                    m_rightSource = null;
                } 
 
                return false;
            } 

            protected override void Dispose(bool disposing)
            {
                if (m_leftSource != null) 
                {
                    m_leftSource.Dispose(); 
                } 
                if (m_rightSource != null)
                { 
                    m_rightSource.Dispose();
                }
            }
        } 

        class OrderedUnionQueryOperatorEnumerator : QueryOperatorEnumerator> 
        { 
            private QueryOperatorEnumerator, TLeftKey> m_leftSource; // Left data source.
            private QueryOperatorEnumerator, TRightKey> m_rightSource; // Right data source. 
            private IComparer> m_keyComparer; // Comparer for compound order keys.
            private IEnumerator, Pair>>> m_outputEnumerator; // Enumerator over the output of the union.
            private bool m_leftOrdered; // Whether the left data source is ordered.
            private bool m_rightOrdered; // Whether the right data source is ordered. 
            private IEqualityComparer m_comparer; // Comparer for the elements.
            private CancellationToken m_cancellationToken; 
 
            //----------------------------------------------------------------------------------------
            // Instantiates a new union operator. 
            //

            internal OrderedUnionQueryOperatorEnumerator(
                QueryOperatorEnumerator, TLeftKey> leftSource, 
                QueryOperatorEnumerator, TRightKey> rightSource,
                bool leftOrdered, bool rightOrdered, IEqualityComparer comparer, IComparer> keyComparer, 
                CancellationToken cancellationToken) 
            {
                Contract.Assert(leftSource != null); 
                Contract.Assert(rightSource != null);

                m_leftSource = leftSource;
                m_rightSource = rightSource; 
                m_keyComparer = keyComparer;
 
                m_leftOrdered = leftOrdered; 
                m_rightOrdered = rightOrdered;
                m_comparer = comparer; 

                if (m_comparer == null)
                {
                    m_comparer = EqualityComparer.Default; 
                }
 
                m_cancellationToken = cancellationToken; 
            }
 
            //---------------------------------------------------------------------------------------
            // Walks the two data sources, left and then right, to produce the union.
            //
 
            internal override bool MoveNext(ref TInputOutput currentElement, ref ConcatKey currentKey)
            { 
                Contract.Assert(m_leftSource != null); 
                Contract.Assert(m_rightSource != null);
 
                if (m_outputEnumerator == null)
                {
                    IEqualityComparer> wrapperComparer = new WrapperEqualityComparer(m_comparer);
                    Dictionary, Pair>> union = 
                        new Dictionary, Pair>>(wrapperComparer);
 
                    Pair elem = default(Pair); 
                    TLeftKey leftKey = default(TLeftKey);
 
                    int i = 0;
                    while (m_leftSource.MoveNext(ref elem, ref leftKey))
                    {
                        if ((i++ & CancellationState.POLL_INTERVAL) == 0) 
                            CancellationState.ThrowIfCanceled(m_cancellationToken);
 
                        ConcatKey key = 
                            ConcatKey.MakeLeft(m_leftOrdered ? leftKey : default(TLeftKey));
                        Pair> oldEntry; 
                        Wrapper wrappedElem = new Wrapper(elem.First);

                        if (!union.TryGetValue(wrappedElem, out oldEntry) || m_keyComparer.Compare(key, oldEntry.Second) < 0)
                        { 
                            union[wrappedElem] = new Pair>(elem.First, key);
                        } 
                    } 

                    TRightKey rightKey = default(TRightKey); 
                    while (m_rightSource.MoveNext(ref elem, ref rightKey))
                    {
                        if ((i++ & CancellationState.POLL_INTERVAL) == 0)
                            CancellationState.ThrowIfCanceled(m_cancellationToken); 

                        ConcatKey key = 
                            ConcatKey.MakeRight(m_rightOrdered ? rightKey : default(TRightKey)); 
                        Pair> oldEntry;
                        Wrapper wrappedElem = new Wrapper(elem.First); 

                        if (!union.TryGetValue(wrappedElem, out oldEntry) || m_keyComparer.Compare(key, oldEntry.Second) < 0)
                        {
                            union[wrappedElem] = new Pair>(elem.First, key); ; 
                        }
                    } 
 
                    m_outputEnumerator = union.GetEnumerator();
                } 

                if (m_outputEnumerator.MoveNext())
                {
                    Pair> current = m_outputEnumerator.Current.Value; 
                    currentElement = current.First;
                    currentKey = current.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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