public static void Delete(this IndexBlock indexBlock, Table record, FileDBContext db)
{
Type type = record.GetType();
PropertyInfo property = type.GetProperty(indexBlock.BindMember);
TableIndexAttribute attr = property.GetCustomAttribute <TableIndexAttribute>();
if (attr == null)
{
throw new Exception(string.Format("No TableIndexAttribute binded!"));
}
FileStream fs = db.fileStream;
// 准备Key。
var key = property.GetValue(record) as IComparable;
SkipListNodeBlock[] rightNodes = FindRightMostNodes(key, indexBlock, db);
IComparable rightKey = db.GetRightObjKey(fs, indexBlock, rightNodes[0]);
// See if we actually found the node
if ((rightNodes[0].RightObj != indexBlock.SkipListTailNode) && (rightKey.CompareTo(key) == 0))
{
for (int i = 0; i <= indexBlock.CurrentLevel; i++)
{
// Since the node is consecutive levels, as soon as we don't find it on the next
// level, we can stop.
if (rightNodes[i].RightObj == indexBlock.SkipListTailNode)
{
break;
}
rightNodes[i].RightObj.TryLoadProperties(fs, SkipListNodeBlockLoadOptions.Key);
rightKey = rightNodes[i].RightObj.Key.GetObject <IComparable>(fs);
if (rightKey.CompareTo(key) != 0)
{
break;
} // 要删除的结点的高度比CurrentLevel低，所以会走到这里。
rightNodes[i].RightObj.TryLoadProperties(fs, SkipListNodeBlockLoadOptions.RightObj);
db.transaction.Add(rightNodes[i]);
db.transaction.Delete(rightNodes[i].RightObj);
rightNodes[i].RightObj = rightNodes[i].RightObj.RightObj;
}
//return true;
}
else
{
//return false;
}
// //itemsCount++;// 有的在内存，有的在文件，因此itemsCount不好使了。
}
public static void Insert(this IndexBlock indexBlock, Table item, DataBlock[] dataBlocksForValue, FileDBContext db)
{
Type type = item.GetType();
PropertyInfo property = type.GetProperty(indexBlock.BindMember);
TableIndexAttribute attr = property.GetCustomAttribute <TableIndexAttribute>();
if (attr == null)
{
throw new Exception(string.Format("No TableIndexAttribute binded!"));
}
// 准备Key。
IComparable key = property.GetValue(item) as IComparable;
byte[] keyBytes = key.ToBytes();
if (keyBytes.Length > Consts.maxDataBytes)
{
throw new Exception(string.Format("Toooo long is the key [{0}]", key));
}
DataBlock dataBlockForKey = new DataBlock()
{
ObjectLength = keyBytes.Length, Data = keyBytes,
};
SkipListNodeBlock[] rightNodes = FindRightMostNodes(key, indexBlock, db);
// Check if the item allready exists in the list. If it does, throw an exception -
// we will not allow duplicate items here.
FileStream fs = db.fileStream;
int maxLevel = db.headerBlock.MaxLevelOfSkipList;
IComparable rightKey = db.GetRightObjKey(fs, indexBlock, rightNodes[0]);
if ((rightNodes[0].RightObj != indexBlock.SkipListTailNode) &&
(rightKey.CompareTo(key) == 0)) // key相等，说明Value相同。此处不再使用NGenerics的Comparer<TKey>.Default这种可指定外部比较工具的模式，是因为那会由于忘记编写合适的比较工具而带来隐藏地很深的bug。
{
throw new Exception("Item Already In List");
}
else
{
int newLevel = PickRandomLevel(db, indexBlock);
if (newLevel > indexBlock.CurrentLevel)
{
for (int i = indexBlock.CurrentLevel + 1; i <= newLevel; i++)
{
rightNodes[i] = indexBlock.SkipListHeadNodes[i];
}
indexBlock.CurrentLevel = newLevel;
}
List <SkipListNodeBlock> nodeList = new List <SkipListNodeBlock>();
SkipListNodeBlock newNode = new SkipListNodeBlock()
{
Key = dataBlockForKey, Value = dataBlocksForValue,
};
nodeList.Add(newNode);
// Insert the item in the first level
newNode.RightObj = rightNodes[0].RightObj;
rightNodes[0].RightObj = newNode;
// And now insert the node in the rest of the levels, making sure
// to update the the links
SkipListNodeBlock previousNode = null;
for (int i = 1; i <= indexBlock.CurrentLevel; i++)
{
previousNode = newNode;
newNode = new SkipListNodeBlock()
{
Key = dataBlockForKey, Value = dataBlocksForValue,
};
nodeList.Add(newNode);
newNode.RightObj = rightNodes[i].RightObj;
rightNodes[i].RightObj = newNode;
newNode.DownObj = previousNode;
}
for (int i = nodeList.Count - 1; i >= 0; i--)
{
db.transaction.Add(rightNodes[i]);
} // 加入事务，准备写入数据库。
for (int i = nodeList.Count - 1; i >= 0; i--)
{
db.transaction.Add(nodeList[i]);
} // 加入事务，准备写入数据库。
db.transaction.Add(dataBlockForKey); // 加入事务，准备写入数据库。
}
//itemsCount++;// 有的在内存，有的在文件，因此itemsCount不好使了。
}
/// <summary>
/// 系统启动时初始化各项常量。
/// </summary>
static Consts()
{
{
PropertyInfo[] properties = typeof(Table).GetProperties();
foreach (var property in properties)
{
TableIndexAttribute attr = property.GetCustomAttribute <TableIndexAttribute>();
if (attr != null && property.PropertyType == typeof(ObjectId))
{
Consts.TableIdString = property.Name;
break;
}
}
}
{
PageHeaderBlock page = new PageHeaderBlock();
using (MemoryStream ms = new MemoryStream())
{
formatter.Serialize(ms, page);
if (ms.Length > Consts.pageSize / 10)
{
throw new Exception("Page header block takes too much space!");
}
Consts.pageHeaderBlockLength = (Int16)ms.Length;
Consts.maxAvailableSpaceInPage = (Int16)(Consts.pageSize - ms.Length);
Consts.minOccupiedBytes = (Int16)(Consts.pageSize - Consts.maxAvailableSpaceInPage);
}
BlockCache.TryRemoveFloatingBlock(page);
}
{
PageHeaderBlock page = new PageHeaderBlock();
DBHeaderBlock dbHeader = new DBHeaderBlock();
TableBlock tableHead = new TableBlock();
Int16 usedSpaceInFirstPage;
using (MemoryStream ms = new MemoryStream())
{
formatter.Serialize(ms, page);
dbHeader.ThisPos = ms.Length;
formatter.Serialize(ms, dbHeader);
tableHead.ThisPos = ms.Length;
Consts.dbHeaderBlockLength = (Int16)(ms.Length - Consts.pageHeaderBlockLength);
formatter.Serialize(ms, tableHead);
Consts.tableBlockLength = (Int16)(ms.Length - tableHead.ThisPos);
usedSpaceInFirstPage = (Int16)ms.Length;
}
if (usedSpaceInFirstPage > Consts.pageSize)
{
throw new Exception("First page is full!");
}
BlockCache.TryRemoveFloatingBlock(page);
BlockCache.TryRemoveFloatingBlock(dbHeader);
BlockCache.TryRemoveFloatingBlock(tableHead);
}
{
IndexBlock block = new IndexBlock();
int length = block.ToBytes().Length;
if (length > Consts.pageSize / 10)
{
throw new Exception("index block takes too much space!");
}
Consts.indexBlockLength = (Int16)length;
BlockCache.TryRemoveFloatingBlock(block);
}
{
SkipListNodeBlock block = new SkipListNodeBlock();
int length = block.ToBytes().Length;
if (length > Consts.pageSize / 10)
{
throw new Exception("index block takes too much space!");
}
Consts.skipListNodeBlockLength = (Int16)length;
BlockCache.TryRemoveFloatingBlock(block);
}
{
PageHeaderBlock page = new PageHeaderBlock();
DataBlock dataBlock = new DataBlock();
dataBlock.Data = new byte[0];
Int16 minValue;
using (MemoryStream ms = new MemoryStream())
{
formatter.Serialize(ms, page);
long pos = ms.Length;
formatter.Serialize(ms, dataBlock);
Consts.dataBlockLength = (Int16)(ms.Length - pos);
if (ms.Length > Consts.pageSize / 10)
{
throw new Exception("data block's metadata takes too much space!");
}
minValue = (Int16)ms.Length;
}
Consts.maxDataBytes = (Int16)(Consts.pageSize - minValue);
BlockCache.TryRemoveFloatingBlock(page);
BlockCache.TryRemoveFloatingBlock(dataBlock);
}
}
