mcs/class/referencesource/System.Data.Entity/System/Data/Objects/SpanIndex.cs

   1 //---------------------------------------------------------------------
   2 // <copyright file="SpanIndex.cs" company="Microsoft">
   3 //      Copyright (c) Microsoft Corporation.  All rights reserved.
   4 // </copyright>
   5 //
   6 // @owner Microsoft
   7 // @backupowner Microsoft
   8 //---------------------------------------------------------------------
   9
  10 using System;
  11 using System.Collections.Generic;
  12 using System.Diagnostics;
  13 using System.Data.Common;
  14 using System.Data.Common.Utils;
  15 using System.Data.Metadata.Edm;
  16 using System.Data.Common.CommandTrees;
  17
  18 namespace System.Data.Objects.Internal
  19 {
  20     /// <summary>
  21     /// An index containing information about how the query was spanned
  22     /// This helps to determine how to materialize the query result
  23     /// </summary>
  24     internal sealed class SpanIndex
  25     {
  26         #region Nested types
  27
  28         /// <summary>
  29         /// Helper class to compare two RowTypes using EdmEquals instead of reference equality.
  30         /// </summary>
  31         sealed private class RowTypeEqualityComparer : IEqualityComparer<RowType>
  32         {
  33             private RowTypeEqualityComparer() { }
  34             internal static readonly RowTypeEqualityComparer Instance = new RowTypeEqualityComparer();
  35
  36             #region IEqualityComparer<RowType> Members
  37
  38             public bool Equals(RowType x, RowType y)
  39             {
  40                 if (x == null || y == null)
  41                 {
  42                     return false;
  43                 }
  44
  45                 return x.EdmEquals(y);
  46             }
  47
  48             public int GetHashCode(RowType obj)
  49             {
  50                 return obj.Identity.GetHashCode();
  51             }
  52
  53             #endregion
  54         }
  55         #endregion
  56
  57         // When a query is spanned, the result is always a RowType
  58         // The _spanMap index maps RowTypes that are a span result to a map between
  59         // column ordinal and end member metadata of the type that is spanned
  60         private Dictionary<RowType, Dictionary<int, AssociationEndMember>> _spanMap;
  61
  62         // A map from a spanned RowType (or parent RowType) to the original TypeUsage prior
  63         // to the query being rewritten
  64         private Dictionary<RowType, TypeUsage> _rowMap;
  65
  66         internal SpanIndex()
  67         {
  68         }
  69
  70         internal void AddSpannedRowType(RowType spannedRowType, TypeUsage originalRowType)
  71         {
  72             Debug.Assert(spannedRowType != null, "Spanned RowType cannot be null");
  73             Debug.Assert(originalRowType != null, "Original RowType cannot be null");
  74             Debug.Assert(originalRowType.EdmType.BuiltInTypeKind == BuiltInTypeKind.RowType, "Original RowType must be a RowType");
  75
  76             if (null == _rowMap)
  77             {
  78                 _rowMap = new Dictionary<RowType, TypeUsage>(RowTypeEqualityComparer.Instance);
  79             }
  80
  81             _rowMap[spannedRowType] = originalRowType;
  82         }
  83
  84         internal TypeUsage GetSpannedRowType(RowType spannedRowType)
  85         {
  86             TypeUsage retType;
  87             if (_rowMap != null && _rowMap.TryGetValue(spannedRowType, out retType))
  88             {
  89                 return retType;
  90             }
  91             return null;
  92         }
  93
  94         internal bool HasSpanMap(RowType spanRowType)
  95         {
  96             Debug.Assert(spanRowType != null, "Span RowType cannot be null");
  97             if (null == _spanMap)
  98             {
  99                 return false;
 100             }
 101
 102             return _spanMap.ContainsKey(spanRowType);
 103         }
 104
 105         internal void AddSpanMap(RowType rowType, Dictionary<int, AssociationEndMember> columnMap)
 106         {
 107             Debug.Assert(rowType != null, "Span row type cannot be null");
 108             Debug.Assert(columnMap != null, "Span column map cannot be null");
 109
 110             if (null == _spanMap)
 111             {
 112                 _spanMap = new Dictionary<RowType, Dictionary<int, AssociationEndMember>>(RowTypeEqualityComparer.Instance);
 113             }
 114
 115             _spanMap[rowType] = columnMap;
 116         }
 117
 118         internal Dictionary<int, AssociationEndMember> GetSpanMap(RowType rowType)
 119         {
 120             Dictionary<int, AssociationEndMember> retMap = null;
 121             if (_spanMap != null && _spanMap.TryGetValue(rowType, out retMap))
 122             {
 123                 return retMap;
 124             }
 125
 126             return null;
 127         }
 128     }
 129 }