Berkeley Db Associate关联数据函数的使用
Code
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.Serialization.Formatters.Binary;
using System.Text;
using BerkeleyDb;
namespace BerkeleyDBDemo
{
public class Class4
{
static void Main( string [] args)
{
using (Db db = new Db(DbCreateFlags.None))
{
db.RecLen = 5000 ;
db.RecPad = ' . ' ;
DbQueue file = (DbQueue)db.Open( null , @" task.aaa " , null , DbType.Queue, Db.OpenFlags.Create, 0 );
using (Db db2 = new Db(DbCreateFlags.None))
{
db2.SetFlags(DbFlags.Dup | DbFlags.DupSort);
DbFile secondfile = db2.Open( null , @" task.bbb " , null , DbType.BTree, Db.OpenFlags.Create, 0 );
file.Associate(secondfile,
delegate (DbFile _secondary, ref DbEntry _key, ref DbEntry _data, out DbEntry _k)
{
// _secondary二级库
// _key一级库
// _data一级库
// _result被创造的二级库key值
MemoryStream _stream = new MemoryStream();
BinaryFormatter _bf = new BinaryFormatter();
_stream.Write(_data.Buffer, 0 , _data.Size);
_stream.Seek( 0 , SeekOrigin.Begin);
Task task2 = (Task)_bf.Deserialize(_stream);
_stream.Close();
_k = DbEntry.InOut(Encoding.UTF8.GetBytes(task2.Author));
// _secondary.Put(null, ref _k, ref _key);
// _secondary.Sync();
return DbFile.KeyGenStatus.Success;
}, DbFile.AssociateFlags.Create);
/// /创建一个任务的一条数据
Task task = new Task()
{
Id = Guid.NewGuid().ToString(),
Author = " lexus " ,
CreatedDate = DateTime.Now
};
AddData(file, task);
AddData(file, task);
AddData(file, task);
task.Author = " bbb " ;
AddData(file, task);
task.Author = " ccc " ;
AddData(file, task);
file.Sync();
}
Console.WriteLine( " finished " );
}
Console.ReadLine();
}
private static void AddData(DbQueue file, Task task)
{
BinaryFormatter bf = new BinaryFormatter();
MemoryStream stream = new MemoryStream();
bf.Serialize(stream, task);
DbEntry key = DbEntry.Out( new byte [ 1024 ]);
DbEntry data = DbEntry.InOut(stream.ToArray());
stream.Close();
file.Append( null , ref key, ref data);
}
}
}
由于bdb无法使用sql，因此关联数据库的运用将使你减轻负担，要理解关联数据库可以将它理解成关系数据库中一对多关系，一端指primary db,多端指secondary db,具体可以参看其doc
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