从一个目录复制到另一个文件最快的方法 [英] Fastest way to copy files from one directory to another

问题描述

我需要从一个目录复制到另一个，这取决于在SQL数据库的表的文件名是否存在。

I need to copy files from one directory to another, depending on the existence of the file name in a table of SQL database.

有关此我使用下面的代码：

For this I use the following code:

using(SqlConnection connection = new SqlConnection("datasource or route"))
{

  connection.Open();

  using(SqlCommand cmd = new SqlCommand("SELECT idPic, namePicFile FROM DocPicFiles", connection))
  using (SqlDataReader reader = cmd.ExecuteReader())
  {

    if (reader != null)
    {
      while (reader.Read())
      {
        //picList IS AN ARRAY THAT Contains All the files names in a directory
        if (picList.Any(s => s.Contains(reader["namePicFile"].ToString())))
        {
          File.Copy("theFile  in the Directory or array picList",  "the destiny directory"+ ".jpg", false)
        }
      }
    }
  }
}

有没有什么办法，这能够在更短的时间内完成？它需要为做到这一点，为20.876的记录。

Is there any way that this can be done in less time? It takes 1 hour for do that, for 20.876 records.

推荐答案

由于您的I / O子系统几乎可以肯定是botteneck这里1个小时，使用并行任务库大概是尽善尽美：

Since your i/o subsystem is almost certainly the botteneck here, using the parallel task library is probably about as good as it gets:

static void Main(string[] args)
{
  DirectoryInfo source      = new DirectoryInfo( args[0] ) ;
  DirectoryInfo destination = new DirectoryInfo( args[1] ) ;

  HashSet<string> filesToBeCopied = new HashSet<string>( ReadFileNamesFromDatabase() , StringComparer.OrdinalIgnoreCase ) ;

  // you'll probably have to play with MaxDegreeOfParallellism so as to avoid swamping the i/o system
  ParallelOptions options= new ParallelOptions { MaxDegreeOfParallelism = 4 } ;

  Parallel.ForEach( filesToBeCopied.SelectMany( fn => source.EnumerateFiles( fn ) ) , options , fi => {
      string destinationPath = Path.Combine( destination.FullName , Path.ChangeExtension( fi.Name , ".jpg") ) ;
      fi.CopyTo( destinationPath , false ) ;
  }) ;

}

public static IEnumerable<string> ReadFileNamesFromDatabase()
{
  using ( SqlConnection connection = new SqlConnection( "connection-string" ) )
  using ( SqlCommand cmd = connection.CreateCommand() )
  {
    cmd.CommandType = CommandType.Text ;
    cmd.CommandText = @"
      select idPic ,
             namePicFile
      from DocPicFiles
      " ;

    connection.Open() ;
    using ( SqlDataReader reader = cmd.ExecuteReader() )
    {
      while ( reader.Read() )
      {
        yield return reader.GetString(1) ;
      }
    }
    connection.Close() ;

  }
}

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