//---------------------------------------------------------------------
// <copyright file="SymbolPair.cs" company="Microsoft">
// Portions of this file copyright (c) Microsoft Corporation
// and are released under the Microsoft Pulic License. See
// http://archive.msdn.microsoft.com/EFSampleProvider/Project/License.aspx
// or License.txt for details.
// All rights reserved.
// </copyright>
//---------------------------------------------------------------------
#if USE_ENTITY_FRAMEWORK_6
namespace System.Data.SQLite.EF6
#else
namespace System.Data.SQLite.Linq
#endif
{
using System.Diagnostics;
#if USE_ENTITY_FRAMEWORK_6
using System.Data.Entity.Core.Common.CommandTrees;
#else
using System.Data.Common.CommandTrees;
#endif
/// <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
}
}