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// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Text;
using System.Data.SqlClient;
using System.Data.Metadata.Edm;
using System.Data.Common.CommandTrees;
namespace SampleEntityFrameworkProvider
{
/// <summary>
/// The SymbolPair exists to solve the record flattening problem.
/// <see cref="SqlGenerator.Visit(DbPropertyExpression)"/>
/// Consider a property expression D(v, "j3.j2.j1.a.x")
/// where v is a VarRef, j1, j2, j3 are joins, a is an extent and x is a columns.
/// This has to be translated eventually into {j'}.{x'}
///
/// The source field represents the outermost SqlStatement representing a join
/// expression (say j2) - this is always a Join symbol.
///
/// The column field keeps moving from one join symbol to the next, until it
/// stops at a non-join symbol.
///
/// This is returned by <see cref="SqlGenerator.Visit(DbPropertyExpression)"/>,
/// but never makes it into a SqlBuilder.
/// </summary>
class SymbolPair : ISqlFragment
{
public Symbol Source;
public Symbol Column;
public SymbolPair(Symbol source, Symbol column)
{
this.Source = source;
this.Column = column;
}
#region ISqlFragment Members
public void WriteSql(SqlWriter writer, SqlGenerator sqlGenerator)
{
// Symbol pair should never be part of a SqlBuilder.
Debug.Assert(false);
}
#endregion
}
}
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