LeftCellWrapper.cs source code in C# .NET

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Code:

/ 4.0 / 4.0 / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / DataEntity / System / Data / Map / ViewGeneration / Structures / LeftCellWrapper.cs / 1305376 / LeftCellWrapper.cs

                            //---------------------------------------------------------------------- 
// 
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// 
// @owner [....]
// @backupOwner [....] 
//--------------------------------------------------------------------- 

using System.Collections.Generic; 
using System.Data.Common.Utils;
using System.Text;
using System.Linq;
using System.Diagnostics; 
using System.Collections.ObjectModel;
using System.Data.Metadata.Edm; 
using System.Data.Common.Utils.Boolean; 
using System.Data.Mapping.ViewGeneration.Validation;
using System.Data.Mapping.ViewGeneration.QueryRewriting; 

namespace System.Data.Mapping.ViewGeneration.Structures
{
 
    // This class essentially stores a cell but in a special form. When we
    // are generating a view for an extent, we denote the extent's side (C or 
    // S) as the "left side" and the side being used in the view as the right 
    // side. For example, in query views, the C side is the left side.
    // 
    // Each LeftCellWrapper is a cell of the form:
    // Project[A1,...,An] (Select[var IN {domain}] (Extent)) = Expr
    // Where
    // - "domain" is a set of multiconstants that correspond to the different 
    //   variable values allowed for the cell query
    // - A1 ... An are denoted by Attributes in this and corresponds to 
    //   the list of attributes that are projected 
    // - Extent is the extent for which th view is being generated
    // - Expr is the expression on the other side to produce the left side of 
    //   the cell
    internal class LeftCellWrapper : InternalBase
    {
 
        #region Fields
        internal static readonly IEqualityComparer BoolEqualityComparer = new BoolWrapperComparer(); 
 
        private Set m_attributes;// project: attributes computed by
 
        // Expr (projected attributes that get set)
        private MemberMaps m_memberMaps;
        private CellQuery m_leftCellQuery; // expression that computes this portion
        private CellQuery m_rightCellQuery; // expression that computes this portion 

        private HashSet m_mergedCells; // Cells that this LeftCellWrapper (MergedCell) wraps. 
                                             // At first it starts off with a single cell and during cell merging 
                                             // cells from both LeftCellWrappers are concatenated.
        private ViewTarget m_viewTarget; 
        private FragmentQuery m_leftFragmentQuery; // Fragment query corresponding to the left cell query of the cell

        internal static readonly IComparer Comparer = new LeftCellWrapperComparer();
        internal static readonly IComparer OriginalCellIdComparer = new CellIdComparer(); 
        #endregion
 
 
        #region Constructor
        // effects: Creates a LeftCellWrapper of the form: 
        // Project[attrs] (Select[var IN {domain}] (Extent)) = cellquery
        // memberMaps is the set of maps used for producing the query or update views
        internal LeftCellWrapper(ViewTarget viewTarget, Set attrs,
                                 FragmentQuery fragmentQuery, 
                                 CellQuery leftCellQuery, CellQuery rightCellQuery, MemberMaps memberMaps, IEnumerable inputCells)
        { 
            m_leftFragmentQuery = fragmentQuery; 
            m_rightCellQuery = rightCellQuery;
            m_leftCellQuery = leftCellQuery; 
            m_attributes = attrs;
            m_viewTarget = viewTarget;
            m_memberMaps = memberMaps;
            m_mergedCells = new HashSet(inputCells); 
        }
 
        internal LeftCellWrapper(ViewTarget viewTarget, Set attrs, 
                                 FragmentQuery fragmentQuery,
                                 CellQuery leftCellQuery, CellQuery rightCellQuery, MemberMaps memberMaps, Cell inputCell) 
            : this(viewTarget, attrs, fragmentQuery, leftCellQuery, rightCellQuery, memberMaps, Enumerable.Repeat(inputCell, 1)) { }

        #endregion
 

 
        #region Properties 

        internal FragmentQuery FragmentQuery 
        {
            get { return m_leftFragmentQuery; }
        }
 
        // effects: Returns the projected fields on the left side
        internal Set Attributes 
        { 
            get { return m_attributes; }
        } 

        // effects: Returns the original cell number from which the wrapper came
        internal string OriginalCellNumberString
        { 
            get
            { 
                return StringUtil.ToSeparatedString(m_mergedCells.Select(cell => cell.CellNumberAsString), "+", ""); 
            }
        } 

        // effects: Returns the right domain map associated with the right query
        internal MemberDomainMap RightDomainMap
        { 
            get { return m_memberMaps.RightDomainMap; }
        } 
 
        [Conditional("DEBUG")]
        internal void AssertHasUniqueCell() 
        {
            Debug.Assert(m_mergedCells.Count == 1);
        }
 
        internal IEnumerable Cells
        { 
            get { return m_mergedCells; } 
        }
 
        // requires: There is only one input cell in this
        // effects: Returns the  input cell provided to view generation as part of the mapping
        internal Cell OnlyInputCell
        { 
            get
            { 
                AssertHasUniqueCell(); 
                return m_mergedCells.First();
            } 
        }

        // effects: Returns the right CellQuery
        internal CellQuery RightCellQuery 
        {
            get { return m_rightCellQuery; } 
        } 

        internal CellQuery LeftCellQuery 
        {
            get { return m_leftCellQuery; }
        }
 

        // effects: Returns the extent for which the wrapper was built 
        internal EntitySetBase LeftExtent 
        {
            get 
            {
                return m_mergedCells.First().GetLeftQuery(m_viewTarget).Extent;
            }
        } 

        // effects: Returns the extent of the right cellquery 
        internal EntitySetBase RightExtent 
        {
            get 
            {
                EntitySetBase result = m_rightCellQuery.Extent;
                Debug.Assert(result != null, "Bad root value in join tree");
                return result; 
            }
        } 
 
        #endregion
 
        #region Methods

        // effects: Yields the input cells in wrappers
        internal static IEnumerable GetInputCellsForWrappers(IEnumerable wrappers) 
        {
            foreach (LeftCellWrapper wrapper in wrappers) 
            { 
                foreach (Cell cell in wrapper.m_mergedCells)
                { 
                    yield return cell;
                }
            }
        } 

        // effects: Creates a boolean variable representing the right extent or association end 
        internal RoleBoolean CreateRoleBoolean() 
        {
            if (RightExtent is AssociationSet) 
            {
                Set ends = GetEndsForTablePrimaryKey();
                if (ends.Count == 1)
                { 
                    AssociationSetEnd setEnd = ((AssociationSet)RightExtent).AssociationSetEnds[ends.First().Name];
                    return new RoleBoolean(setEnd); 
                } 
            }
            return new RoleBoolean(RightExtent); 
        }

        // effects: Given a set of wrappers, returns a string that contains the list of extents in the
        // rightcellQueries of the wrappers 
        internal static string GetExtentListAsUserString(IEnumerable wrappers)
        { 
            Set extents = new Set(EqualityComparer.Default); 
            foreach (LeftCellWrapper wrapper in wrappers)
            { 
                extents.Add(wrapper.RightExtent);
            }

            StringBuilder builder = new StringBuilder(); 
            bool isFirst = true;
            foreach (EntitySetBase extent in extents) 
            { 
                if (isFirst == false)
                { 
                    builder.Append(", ");
                }
                isFirst = false;
                builder.Append(extent.Name); 
            }
            return builder.ToString(); 
        } 

        internal override void ToFullString(StringBuilder builder) 
        {
            builder.Append("P[");
            StringUtil.ToSeparatedString(builder, m_attributes, ",");
            builder.Append("] = "); 
            m_rightCellQuery.ToFullString(builder);
        } 
 
        // effects: Modifies stringBuilder to contain the view corresponding
        // to the right cellquery 
        internal override void ToCompactString(StringBuilder stringBuilder)
        {
            stringBuilder.Append(OriginalCellNumberString);
        } 

        // effects: Writes m_cellWrappers to builder 
        internal static void WrappersToStringBuilder(StringBuilder builder, List wrappers, 
                                                     string header)
        { 
            builder.AppendLine()
                   .Append(header)
                   .AppendLine();
            // Sort them according to the original cell number 
            LeftCellWrapper[] cellWrappers = wrappers.ToArray();
            Array.Sort(cellWrappers, LeftCellWrapper.OriginalCellIdComparer); 
 
            foreach (LeftCellWrapper wrapper in cellWrappers)
            { 
                wrapper.ToCompactString(builder);
                builder.Append(" = ");
                wrapper.ToFullString(builder);
                builder.AppendLine(); 
            }
        } 
 

        // requires: RightCellQuery.Extent corresponds to a relationship set 
        // effects: Returns the ends to which the key of the corresponding
        // table (i.e., the left query) maps to in the relationship set. For
        // example, if RightCellQuery.Extent is OrderOrders and it maps to
        //  of table SOrders with key oid, this returns the 
        // end to which oid is mapped. Similarly, if we have a link table
        // with the whole key mapped to two ends of the association set, it 
        // returns both ends 
        private Set GetEndsForTablePrimaryKey()
        { 
            CellQuery rightQuery = RightCellQuery;
            Set result = new Set(EqualityComparer.Default);
            // Get the key slots for the table (they are in the slotMap) and
            // check for that slot on the C-side 
            foreach (int keySlot in m_memberMaps.ProjectedSlotMap.KeySlots)
            { 
                MemberProjectedSlot slot = (MemberProjectedSlot)rightQuery.ProjectedSlotAt(keySlot); 
                MemberPath path = slot.MemberPath;
                // See what end it maps to in the relationSet 
                AssociationEndMember endMember = (AssociationEndMember)path.RootEdmMember;
                Debug.Assert(endMember != null, "Element in path before scalar path is not end property?");
                result.Add(endMember);
            } 
            Debug.Assert(result != null, "No end found for keyslots of table?");
            return result; 
        } 

 
        internal MemberProjectedSlot GetLeftSideMappedSlotForRightSideMember(MemberPath member)
        {
            int projectedPosition = RightCellQuery.GetProjectedPosition(new MemberProjectedSlot(member));
            if (projectedPosition == -1) 
            {
                return null; 
            } 

            ProjectedSlot slot = LeftCellQuery.ProjectedSlotAt(projectedPosition); 

            if (slot == null || slot is ConstantProjectedSlot)
            {
                return null; 
            }
 
            return slot as MemberProjectedSlot; 
        }
 
        internal MemberProjectedSlot GetRightSideMappedSlotForLeftSideMember(MemberPath member)
        {
            int projectedPosition = LeftCellQuery.GetProjectedPosition(new MemberProjectedSlot(member));
            if (projectedPosition == -1) 
            {
                return null; 
            } 

            ProjectedSlot slot = RightCellQuery.ProjectedSlotAt(projectedPosition); 

            if (slot == null || slot is ConstantProjectedSlot)
            {
                return null; 
            }
 
            return slot as MemberProjectedSlot; 
        }
 
        internal MemberProjectedSlot GetCSideMappedSlotForSMember(MemberPath member)
        {
            if (m_viewTarget == ViewTarget.QueryView)
            { 
                return GetLeftSideMappedSlotForRightSideMember(member);
            } 
            else 
            {
                return GetRightSideMappedSlotForLeftSideMember(member); 
            }
        }

        #endregion 

        #region Equality Comparer class 
        // This class compares wrappers based on the Right Where Clause and 
        // Extent -- needed for the boolean engine
        private class BoolWrapperComparer : IEqualityComparer 
        {

            public bool Equals(LeftCellWrapper left, LeftCellWrapper right)
            { 
                // Quick check with references
                if (object.ReferenceEquals(left, right)) 
                { 
                    // Gets the Null and Undefined case as well
                    return true; 
                }
                // One of them is non-null at least
                if (left == null || right == null)
                { 
                    return false;
                } 
                // Both are non-null at this point 
                bool whereClauseEqual = BoolExpression.EqualityComparer.Equals(left.RightCellQuery.WhereClause,
                                                                               right.RightCellQuery.WhereClause); 

                return left.RightExtent.Equals(right.RightExtent) && whereClauseEqual;
            }
 
            public int GetHashCode(LeftCellWrapper wrapper)
            { 
                return BoolExpression.EqualityComparer.GetHashCode(wrapper.RightCellQuery.WhereClause) ^ wrapper.RightExtent.GetHashCode(); 
            }
        } 
        #endregion

        #region Comparer
        // A class that compares two cell wrappers. Useful for guiding heuristics 
        // and to ensure that the largest selection domain (i.e., the number of
        // multiconstants in "mc in {...}") is first in the list 
        private class LeftCellWrapperComparer : IComparer 
        {
 
            public int Compare(LeftCellWrapper x, LeftCellWrapper y)
            {

                // More attributes first -- so that we get most attributes 
                // with very few intersections (when we use the sortings for
                // that). When we are subtracting, attributes are not important 
 
                // Use FragmentQuery's attributes instead of LeftCellWrapper's original attributes in the comparison
                // since the former might have got extended to include all attributes whose value is determined 
                // by the WHERE clause (e.g., if we have WHERE ProductName='Camera' we can assume ProductName is projected)

                if (x.FragmentQuery.Attributes.Count > y.FragmentQuery.Attributes.Count)
                { 
                    return -1;
                } 
                else if (x.FragmentQuery.Attributes.Count < y.FragmentQuery.Attributes.Count) 
                {
                    return 1; 
                }
                // Since the sort may not be stable, we use the original cell number string to break the tie
                return String.CompareOrdinal(x.OriginalCellNumberString, y.OriginalCellNumberString);
            } 
        }
 
        // A class that compares two cell wrappers based on original cell number 
        internal class CellIdComparer : IComparer
        { 

            public int Compare(LeftCellWrapper x, LeftCellWrapper y)
            {
                return StringComparer.Ordinal.Compare(x.OriginalCellNumberString, y.OriginalCellNumberString); 
            }
        } 
 
        #endregion
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
//---------------------------------------------------------------------- 
// 
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// 
// @owner [....]
// @backupOwner [....] 
//--------------------------------------------------------------------- 

using System.Collections.Generic; 
using System.Data.Common.Utils;
using System.Text;
using System.Linq;
using System.Diagnostics; 
using System.Collections.ObjectModel;
using System.Data.Metadata.Edm; 
using System.Data.Common.Utils.Boolean; 
using System.Data.Mapping.ViewGeneration.Validation;
using System.Data.Mapping.ViewGeneration.QueryRewriting; 

namespace System.Data.Mapping.ViewGeneration.Structures
{
 
    // This class essentially stores a cell but in a special form. When we
    // are generating a view for an extent, we denote the extent's side (C or 
    // S) as the "left side" and the side being used in the view as the right 
    // side. For example, in query views, the C side is the left side.
    // 
    // Each LeftCellWrapper is a cell of the form:
    // Project[A1,...,An] (Select[var IN {domain}] (Extent)) = Expr
    // Where
    // - "domain" is a set of multiconstants that correspond to the different 
    //   variable values allowed for the cell query
    // - A1 ... An are denoted by Attributes in this and corresponds to 
    //   the list of attributes that are projected 
    // - Extent is the extent for which th view is being generated
    // - Expr is the expression on the other side to produce the left side of 
    //   the cell
    internal class LeftCellWrapper : InternalBase
    {
 
        #region Fields
        internal static readonly IEqualityComparer BoolEqualityComparer = new BoolWrapperComparer(); 
 
        private Set m_attributes;// project: attributes computed by
 
        // Expr (projected attributes that get set)
        private MemberMaps m_memberMaps;
        private CellQuery m_leftCellQuery; // expression that computes this portion
        private CellQuery m_rightCellQuery; // expression that computes this portion 

        private HashSet m_mergedCells; // Cells that this LeftCellWrapper (MergedCell) wraps. 
                                             // At first it starts off with a single cell and during cell merging 
                                             // cells from both LeftCellWrappers are concatenated.
        private ViewTarget m_viewTarget; 
        private FragmentQuery m_leftFragmentQuery; // Fragment query corresponding to the left cell query of the cell

        internal static readonly IComparer Comparer = new LeftCellWrapperComparer();
        internal static readonly IComparer OriginalCellIdComparer = new CellIdComparer(); 
        #endregion
 
 
        #region Constructor
        // effects: Creates a LeftCellWrapper of the form: 
        // Project[attrs] (Select[var IN {domain}] (Extent)) = cellquery
        // memberMaps is the set of maps used for producing the query or update views
        internal LeftCellWrapper(ViewTarget viewTarget, Set attrs,
                                 FragmentQuery fragmentQuery, 
                                 CellQuery leftCellQuery, CellQuery rightCellQuery, MemberMaps memberMaps, IEnumerable inputCells)
        { 
            m_leftFragmentQuery = fragmentQuery; 
            m_rightCellQuery = rightCellQuery;
            m_leftCellQuery = leftCellQuery; 
            m_attributes = attrs;
            m_viewTarget = viewTarget;
            m_memberMaps = memberMaps;
            m_mergedCells = new HashSet(inputCells); 
        }
 
        internal LeftCellWrapper(ViewTarget viewTarget, Set attrs, 
                                 FragmentQuery fragmentQuery,
                                 CellQuery leftCellQuery, CellQuery rightCellQuery, MemberMaps memberMaps, Cell inputCell) 
            : this(viewTarget, attrs, fragmentQuery, leftCellQuery, rightCellQuery, memberMaps, Enumerable.Repeat(inputCell, 1)) { }

        #endregion
 

 
        #region Properties 

        internal FragmentQuery FragmentQuery 
        {
            get { return m_leftFragmentQuery; }
        }
 
        // effects: Returns the projected fields on the left side
        internal Set Attributes 
        { 
            get { return m_attributes; }
        } 

        // effects: Returns the original cell number from which the wrapper came
        internal string OriginalCellNumberString
        { 
            get
            { 
                return StringUtil.ToSeparatedString(m_mergedCells.Select(cell => cell.CellNumberAsString), "+", ""); 
            }
        } 

        // effects: Returns the right domain map associated with the right query
        internal MemberDomainMap RightDomainMap
        { 
            get { return m_memberMaps.RightDomainMap; }
        } 
 
        [Conditional("DEBUG")]
        internal void AssertHasUniqueCell() 
        {
            Debug.Assert(m_mergedCells.Count == 1);
        }
 
        internal IEnumerable Cells
        { 
            get { return m_mergedCells; } 
        }
 
        // requires: There is only one input cell in this
        // effects: Returns the  input cell provided to view generation as part of the mapping
        internal Cell OnlyInputCell
        { 
            get
            { 
                AssertHasUniqueCell(); 
                return m_mergedCells.First();
            } 
        }

        // effects: Returns the right CellQuery
        internal CellQuery RightCellQuery 
        {
            get { return m_rightCellQuery; } 
        } 

        internal CellQuery LeftCellQuery 
        {
            get { return m_leftCellQuery; }
        }
 

        // effects: Returns the extent for which the wrapper was built 
        internal EntitySetBase LeftExtent 
        {
            get 
            {
                return m_mergedCells.First().GetLeftQuery(m_viewTarget).Extent;
            }
        } 

        // effects: Returns the extent of the right cellquery 
        internal EntitySetBase RightExtent 
        {
            get 
            {
                EntitySetBase result = m_rightCellQuery.Extent;
                Debug.Assert(result != null, "Bad root value in join tree");
                return result; 
            }
        } 
 
        #endregion
 
        #region Methods

        // effects: Yields the input cells in wrappers
        internal static IEnumerable GetInputCellsForWrappers(IEnumerable wrappers) 
        {
            foreach (LeftCellWrapper wrapper in wrappers) 
            { 
                foreach (Cell cell in wrapper.m_mergedCells)
                { 
                    yield return cell;
                }
            }
        } 

        // effects: Creates a boolean variable representing the right extent or association end 
        internal RoleBoolean CreateRoleBoolean() 
        {
            if (RightExtent is AssociationSet) 
            {
                Set ends = GetEndsForTablePrimaryKey();
                if (ends.Count == 1)
                { 
                    AssociationSetEnd setEnd = ((AssociationSet)RightExtent).AssociationSetEnds[ends.First().Name];
                    return new RoleBoolean(setEnd); 
                } 
            }
            return new RoleBoolean(RightExtent); 
        }

        // effects: Given a set of wrappers, returns a string that contains the list of extents in the
        // rightcellQueries of the wrappers 
        internal static string GetExtentListAsUserString(IEnumerable wrappers)
        { 
            Set extents = new Set(EqualityComparer.Default); 
            foreach (LeftCellWrapper wrapper in wrappers)
            { 
                extents.Add(wrapper.RightExtent);
            }

            StringBuilder builder = new StringBuilder(); 
            bool isFirst = true;
            foreach (EntitySetBase extent in extents) 
            { 
                if (isFirst == false)
                { 
                    builder.Append(", ");
                }
                isFirst = false;
                builder.Append(extent.Name); 
            }
            return builder.ToString(); 
        } 

        internal override void ToFullString(StringBuilder builder) 
        {
            builder.Append("P[");
            StringUtil.ToSeparatedString(builder, m_attributes, ",");
            builder.Append("] = "); 
            m_rightCellQuery.ToFullString(builder);
        } 
 
        // effects: Modifies stringBuilder to contain the view corresponding
        // to the right cellquery 
        internal override void ToCompactString(StringBuilder stringBuilder)
        {
            stringBuilder.Append(OriginalCellNumberString);
        } 

        // effects: Writes m_cellWrappers to builder 
        internal static void WrappersToStringBuilder(StringBuilder builder, List wrappers, 
                                                     string header)
        { 
            builder.AppendLine()
                   .Append(header)
                   .AppendLine();
            // Sort them according to the original cell number 
            LeftCellWrapper[] cellWrappers = wrappers.ToArray();
            Array.Sort(cellWrappers, LeftCellWrapper.OriginalCellIdComparer); 
 
            foreach (LeftCellWrapper wrapper in cellWrappers)
            { 
                wrapper.ToCompactString(builder);
                builder.Append(" = ");
                wrapper.ToFullString(builder);
                builder.AppendLine(); 
            }
        } 
 

        // requires: RightCellQuery.Extent corresponds to a relationship set 
        // effects: Returns the ends to which the key of the corresponding
        // table (i.e., the left query) maps to in the relationship set. For
        // example, if RightCellQuery.Extent is OrderOrders and it maps to
        //  of table SOrders with key oid, this returns the 
        // end to which oid is mapped. Similarly, if we have a link table
        // with the whole key mapped to two ends of the association set, it 
        // returns both ends 
        private Set GetEndsForTablePrimaryKey()
        { 
            CellQuery rightQuery = RightCellQuery;
            Set result = new Set(EqualityComparer.Default);
            // Get the key slots for the table (they are in the slotMap) and
            // check for that slot on the C-side 
            foreach (int keySlot in m_memberMaps.ProjectedSlotMap.KeySlots)
            { 
                MemberProjectedSlot slot = (MemberProjectedSlot)rightQuery.ProjectedSlotAt(keySlot); 
                MemberPath path = slot.MemberPath;
                // See what end it maps to in the relationSet 
                AssociationEndMember endMember = (AssociationEndMember)path.RootEdmMember;
                Debug.Assert(endMember != null, "Element in path before scalar path is not end property?");
                result.Add(endMember);
            } 
            Debug.Assert(result != null, "No end found for keyslots of table?");
            return result; 
        } 

 
        internal MemberProjectedSlot GetLeftSideMappedSlotForRightSideMember(MemberPath member)
        {
            int projectedPosition = RightCellQuery.GetProjectedPosition(new MemberProjectedSlot(member));
            if (projectedPosition == -1) 
            {
                return null; 
            } 

            ProjectedSlot slot = LeftCellQuery.ProjectedSlotAt(projectedPosition); 

            if (slot == null || slot is ConstantProjectedSlot)
            {
                return null; 
            }
 
            return slot as MemberProjectedSlot; 
        }
 
        internal MemberProjectedSlot GetRightSideMappedSlotForLeftSideMember(MemberPath member)
        {
            int projectedPosition = LeftCellQuery.GetProjectedPosition(new MemberProjectedSlot(member));
            if (projectedPosition == -1) 
            {
                return null; 
            } 

            ProjectedSlot slot = RightCellQuery.ProjectedSlotAt(projectedPosition); 

            if (slot == null || slot is ConstantProjectedSlot)
            {
                return null; 
            }
 
            return slot as MemberProjectedSlot; 
        }
 
        internal MemberProjectedSlot GetCSideMappedSlotForSMember(MemberPath member)
        {
            if (m_viewTarget == ViewTarget.QueryView)
            { 
                return GetLeftSideMappedSlotForRightSideMember(member);
            } 
            else 
            {
                return GetRightSideMappedSlotForLeftSideMember(member); 
            }
        }

        #endregion 

        #region Equality Comparer class 
        // This class compares wrappers based on the Right Where Clause and 
        // Extent -- needed for the boolean engine
        private class BoolWrapperComparer : IEqualityComparer 
        {

            public bool Equals(LeftCellWrapper left, LeftCellWrapper right)
            { 
                // Quick check with references
                if (object.ReferenceEquals(left, right)) 
                { 
                    // Gets the Null and Undefined case as well
                    return true; 
                }
                // One of them is non-null at least
                if (left == null || right == null)
                { 
                    return false;
                } 
                // Both are non-null at this point 
                bool whereClauseEqual = BoolExpression.EqualityComparer.Equals(left.RightCellQuery.WhereClause,
                                                                               right.RightCellQuery.WhereClause); 

                return left.RightExtent.Equals(right.RightExtent) && whereClauseEqual;
            }
 
            public int GetHashCode(LeftCellWrapper wrapper)
            { 
                return BoolExpression.EqualityComparer.GetHashCode(wrapper.RightCellQuery.WhereClause) ^ wrapper.RightExtent.GetHashCode(); 
            }
        } 
        #endregion

        #region Comparer
        // A class that compares two cell wrappers. Useful for guiding heuristics 
        // and to ensure that the largest selection domain (i.e., the number of
        // multiconstants in "mc in {...}") is first in the list 
        private class LeftCellWrapperComparer : IComparer 
        {
 
            public int Compare(LeftCellWrapper x, LeftCellWrapper y)
            {

                // More attributes first -- so that we get most attributes 
                // with very few intersections (when we use the sortings for
                // that). When we are subtracting, attributes are not important 
 
                // Use FragmentQuery's attributes instead of LeftCellWrapper's original attributes in the comparison
                // since the former might have got extended to include all attributes whose value is determined 
                // by the WHERE clause (e.g., if we have WHERE ProductName='Camera' we can assume ProductName is projected)

                if (x.FragmentQuery.Attributes.Count > y.FragmentQuery.Attributes.Count)
                { 
                    return -1;
                } 
                else if (x.FragmentQuery.Attributes.Count < y.FragmentQuery.Attributes.Count) 
                {
                    return 1; 
                }
                // Since the sort may not be stable, we use the original cell number string to break the tie
                return String.CompareOrdinal(x.OriginalCellNumberString, y.OriginalCellNumberString);
            } 
        }
 
        // A class that compares two cell wrappers based on original cell number 
        internal class CellIdComparer : IComparer
        { 

            public int Compare(LeftCellWrapper x, LeftCellWrapper y)
            {
                return StringComparer.Ordinal.Compare(x.OriginalCellNumberString, y.OriginalCellNumberString); 
            }
        } 
 
        #endregion
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
                        

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