mcs/class/referencesource/System.Data.Entity/System/Data/Mapping/ViewGeneration/CqlGeneration/BooleanProjectedSlot.cs

   1 //---------------------------------------------------------------------
   2 // <copyright file="BooleanProjectedSlot.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.Data.Mapping.ViewGeneration.Structures;
  11 using System.Text;
  12 using System.Diagnostics;
  13 using System.Data.Common.CommandTrees;
  14 using System.Data.Common.CommandTrees.ExpressionBuilder;
  15 using System.Data.Common.Utils;
  16
  17 namespace System.Data.Mapping.ViewGeneration.CqlGeneration
  18 {
  19     /// <summary>
  20     /// This class represents slots for expressions over boolean variables, e.g., _from0, _from1, etc
  21     /// </summary>
  22     internal sealed class BooleanProjectedSlot : ProjectedSlot
  23     {
  24         #region Constructor
  25         /// <summary>
  26         /// Creates a boolean slot for expression that comes from originalCellNum, i.e.,
  27         /// the value of the slot is <paramref name="expr"/> and the name is "_from{<paramref name="originalCellNum"/>}", e.g., _from2
  28         /// </summary>
  29         internal BooleanProjectedSlot(BoolExpression expr, CqlIdentifiers identifiers, int originalCellNum)
  30         {
  31             m_expr = expr;
  32             m_originalCell = new CellIdBoolean(identifiers, originalCellNum);
  33
  34             Debug.Assert(!(expr.AsLiteral is CellIdBoolean) ||
  35                          BoolLiteral.EqualityComparer.Equals((CellIdBoolean)expr.AsLiteral, m_originalCell), "Cellid boolean for the slot and cell number disagree");
  36         }
  37         #endregion
  38
  39         #region Fields
  40         /// <summary>
  41         /// The actual value of the slot - could be <see cref="CellIdBoolean"/>!
  42         /// </summary>
  43         private readonly BoolExpression m_expr;
  44         /// <summary>
  45         /// A boolean corresponding to the original cell number (_from0)
  46         /// </summary>
  47         private readonly CellIdBoolean m_originalCell;
  48         #endregion
  49
  50         #region Methods
  51         /// <summary>
  52         /// Returns "_from0", "_from1" etc. <paramref name="outputMember"/> is ignored.
  53         /// </summary>
  54         internal override string GetCqlFieldAlias(MemberPath outputMember)
  55         {
  56             return m_originalCell.SlotName;
  57         }
  58
  59         internal override StringBuilder AsEsql(StringBuilder builder, MemberPath outputMember, string blockAlias, int indentLevel)
  60         {
  61             if (m_expr.IsTrue || m_expr.IsFalse)
  62             {
  63                 // No Case statement for TRUE and FALSE
  64                 m_expr.AsEsql(builder, blockAlias);
  65             }
  66             else
  67             {
  68                 // Produce "CASE WHEN boolExpr THEN True ELSE False END" in order to enforce the two-state boolean logic:
  69                 // if boolExpr returns the boolean Unknown, it gets converted to boolean False.
  70                 builder.Append("CASE WHEN ");
  71                 m_expr.AsEsql(builder, blockAlias);
  72                 builder.Append(" THEN True ELSE False END");
  73             }
  74             return builder;
  75         }
  76
  77         internal override DbExpression AsCqt(DbExpression row, MemberPath outputMember)
  78         {
  79             if (m_expr.IsTrue || m_expr.IsFalse)
  80             {
  81                 return m_expr.AsCqt(row);
  82             }
  83             else
  84             {
  85                 // Produce "CASE WHEN boolExpr THEN True ELSE False END" in order to enforce the two-state boolean logic:
  86                 // if boolExpr returns the boolean Unknown, it gets converted to boolean False.
  87                 return DbExpressionBuilder.Case(new DbExpression[] { m_expr.AsCqt(row) }, new DbExpression[] { DbExpressionBuilder.True }, DbExpressionBuilder.False);
  88             }
  89         }
  90
  91         internal override void ToCompactString(StringBuilder builder)
  92         {
  93             StringUtil.FormatStringBuilder(builder, "<{0}, ", m_originalCell.SlotName);
  94             m_expr.ToCompactString(builder);
  95             builder.Append('>');
  96         }
  97         #endregion
  98     }
  99 }