11/19/2023
创建
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#region License
// Copyright 2005-2019 Paul Kohler (https://github.com/paulkohler/minisqlquery). All rights reserved.
// This source code is made available under the terms of the GNU Lesser General Public License v3.0
// https://github.com/paulkohler/minisqlquery/blob/master/LICENSE
#endregion
using System;
using System.Collections.Generic;
namespace MiniSqlQuery.Core.DbModel
{
/// <summary>Examins a <see cref="DbModelInstance"/> providing sort methods.</summary>
public class DbModelDependencyWalker
{
/// <summary>The _model.</summary>
private readonly DbModelInstance _model;
/// <summary>Initializes a new instance of the <see cref="DbModelDependencyWalker"/> class.</summary>
/// <param name="model">The database model instance.</param>
public DbModelDependencyWalker(DbModelInstance model)
{
if (model == null)
{
throw new ArgumentNullException("model");
}
_model = model;
}
/// <summary>Sorts the tables by checking the foreign key references recursivly building a list of tables in order.</summary>
/// <returns>An array of tables in dependency order.</returns>
public DbModelTable[] SortTablesByForeignKeyReferences()
{
List<DbModelTable> tables = new List<DbModelTable>();
// add tables with no FKs
foreach (DbModelTable table in _model.Tables)
{
if (table.ForeignKeyColumns.Count == 0)
{
tables.Add(table);
}
}
foreach (DbModelTable table in _model.Tables)
{
ProcessForeignKeyReferences(1, tables, table);
}
return tables.ToArray();
}
/// <summary>The process foreign key references.</summary>
/// <param name="level">The level.</param>
/// <param name="tablesList">The tables list.</param>
/// <param name="table">The table.</param>
/// <exception cref="InvalidOperationException"></exception>
private void ProcessForeignKeyReferences(int level, List<DbModelTable> tablesList, DbModelTable table)
{
if (tablesList.Contains(table))
{
return;
}
// recursive insurance ;-)
level++;
if (level > 1000)
{
throw new InvalidOperationException(string.Format("FK processor exceeded recursive level of 1000 at '{0}'.", table.Name));
}
// if there are FK refs, add the refered tables first
if (table.ForeignKeyColumns.Count > 0)
{
// if the table is not already in the list....
foreach (DbModelColumn fkColumn in table.ForeignKeyColumns)
{
// ensure its not a self referencing table
if (fkColumn.ForeignKeyReference.ReferenceTable != table)
{
ProcessForeignKeyReferences(++level, tablesList, fkColumn.ForeignKeyReference.ReferenceTable);
}
}
// now add the table if not in the list yet
if (!tablesList.Contains(table))
{
tablesList.Add(table);
}
}
}
}
}
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