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//---------------------------------------------------------------------
// <copyright file="Symbol.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//
// @owner Microsoft
// @backupOwner Microsoft
//---------------------------------------------------------------------
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 System.Data.SqlClient.SqlGen
{
/// <summary>
/// <see cref="SymbolTable"/>
/// This class represents an extent/nested select statement,
/// or a column.
///
/// The important fields are Name, Type and NewName.
/// NewName starts off the same as Name, and is then modified as necessary.
///
///
/// The rest are used by special symbols.
/// e.g. NeedsRenaming is used by columns to indicate that a new name must
/// be picked for the column in the second phase of translation.
///
/// IsUnnest is used by symbols for a collection expression used as a from clause.
/// This allows <see cref="SqlGenerator.AddFromSymbol(SqlSelectStatement, string, Symbol, bool)"/> to add the column list
/// after the alias.
///
/// </summary>
internal class Symbol : ISqlFragment
{
/// <summary>
/// Used to track the columns originating from this Symbol when it is used
/// in as a from extent in a SqlSelectStatement with a Join or as a From Extent
/// in a Join Symbol.
/// </summary>
private Dictionary<string, Symbol> columns;
internal Dictionary<string, Symbol> Columns
{
get
{
if (null == columns)
{
columns = new Dictionary<string, Symbol>(StringComparer.OrdinalIgnoreCase);
}
return columns;
}
}
/// <summary>
/// Used to track the output columns of a SqlSelectStatement it represents
/// </summary>
private Dictionary<string, Symbol> outputColumns;
internal Dictionary<string, Symbol> OutputColumns
{
get
{
if (null == outputColumns)
{
outputColumns = new Dictionary<string, Symbol>(StringComparer.OrdinalIgnoreCase);
}
return outputColumns;
}
}
private bool needsRenaming;
internal bool NeedsRenaming
{
get { return needsRenaming; }
set { needsRenaming = value; }
}
private bool outputColumnsRenamed;
internal bool OutputColumnsRenamed
{
get { return outputColumnsRenamed; }
set { outputColumnsRenamed = value; }
}
private string name;
public string Name
{
get { return name; }
}
private string newName;
public string NewName
{
get { return newName; }
set { newName = value; }
}
private TypeUsage type;
internal TypeUsage Type
{
get { return type; }
set { type = value; }
}
public Symbol(string name, TypeUsage type)
{
this.name = name;
this.newName = name;
this.Type = type;
}
/// <summary>
/// Use this constructor if the symbol represents a SqlStatement for which the output columns need to be tracked.
/// </summary>
/// <param name="name"></param>
/// <param name="type"></param>
/// <param name="outputColumns"></param>
/// <param name="outputColumnsRenamed"></param>
public Symbol(string name, TypeUsage type, Dictionary<string, Symbol> outputColumns, bool outputColumnsRenamed)
{
this.name = name;
this.newName = name;
this.Type = type;
this.outputColumns = outputColumns;
this.OutputColumnsRenamed = outputColumnsRenamed;
}
#region ISqlFragment Members
/// <summary>
/// Write this symbol out as a string for sql. This is just
/// the new name of the symbol (which could be the same as the old name).
///
/// We rename columns here if necessary.
/// </summary>
/// <param name="writer"></param>
/// <param name="sqlGenerator"></param>
public void WriteSql(SqlWriter writer, SqlGenerator sqlGenerator)
{
if (this.NeedsRenaming)
{
int i;
if (sqlGenerator.AllColumnNames.TryGetValue(this.NewName, out i))
{
string newNameCandidate;
do
{
++i;
newNameCandidate = this.NewName + i.ToString(System.Globalization.CultureInfo.InvariantCulture);
} while (sqlGenerator.AllColumnNames.ContainsKey(newNameCandidate));
sqlGenerator.AllColumnNames[this.NewName] = i;
this.NewName = newNameCandidate;
}
// Add this column name to list of known names so that there are no subsequent
// collisions
sqlGenerator.AllColumnNames[this.NewName] = 0;
// Prevent it from being renamed repeatedly.
this.NeedsRenaming = false;
}
writer.Write(SqlGenerator.QuoteIdentifier(this.NewName));
}
#endregion
}
}
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