public IEnumerable <int> All(int offset)
{
MetaItemsPage <T> page = this[offset];
if (page == null)
{
yield break;
}
else
{
foreach (var ofs in page.Items.SelectMany(i => i.Value))
{
yield return(ofs);
}
}
}
/// <summary>
/// Used to search by comparison operators inside a given item page
/// </summary>
/// <param name="offset">offset (ID) of the item page</param>
/// <param name="key">key to compare</param>
/// <param name="oper">comparison operator</param>
/// <returns></returns>
public IEnumerable <KeyValuePair <T, List <int> > > FindByOper(int offset, T key, TokenType oper)
{
MetaItemsPage <T> page = this[offset];
if (page == null)
{
yield break;
}
else
{
var collection = Enumerable.Empty <KeyValuePair <T, List <int> > >();
switch (oper)
{
case TokenType.Equal:
collection = page.Items.Where(i => i.Key.Equals(key));
break;
case TokenType.NotEqual:
collection = page.Items.Where(i => i.Key.CompareTo(key) != 0);
break;
case TokenType.Less:
collection = page.Items.Where(i => i.Key.CompareTo(key) < 0);
break;
case TokenType.LessOrEqual:
collection = page.Items.Where(i => i.Key.CompareTo(key) <= 0);
break;
case TokenType.Greater:
collection = page.Items.Where(i => i.Key.CompareTo(key) > 0);
break;
case TokenType.GreaterOrEqual:
collection = page.Items.Where(i => i.Key.CompareTo(key) >= 0);
break;
default:
throw new ArgumentException($"invalid operator: {oper}");
}
foreach (var ofs in collection)
{
yield return(ofs);
}
}
}
/// <summary>
/// Finds an key in a page according to its offset
/// </summary>
/// <param name="offset">offset (ID) of page</param>
/// <param name="key">key</param>
/// <returns></returns>
public DbKeyValues <T> Find(int offset, T key)
{
MetaItemsPage <T> page = this[offset];
if (page == null)
{
return(null);
}
var pair = page.Items.FirstOrDefault(i => i.Key.Equals(key));
return((pair.Key == null) ?
null :
new DbKeyValues <T>()
{
Key = pair.Key,
Values = pair.Value
});
}
public DbIndexItems(CsvDb db, string tableName, string columnName)
{
if ((Database = db) == null)
{
throw new ArgumentException("Database is undefined");
}
Index = Database.Index(tableName, columnName);
if (Index == null)
{
throw new ArgumentException($"Column [{columnName}] does not exists in table [{tableName}].");
}
//load structure
PathToItems = io.Path.Combine(Database.BinaryPath, $"{Index.Indexer}.bin");
if (!io.File.Exists(PathToItems))
{
throw new ArgumentException($"Could not find indexer in database");
}
Hash = new Dictionary <int, MetaItemsPage <T> >();
//read main structure of item pages
using (reader = new io.BinaryReader(io.File.OpenRead(PathToItems)))
{
//Header
PageCount = reader.ReadInt32();
Int32 keyTypeValue = reader.ReadInt32();
KeyType = (DbColumnType)keyTypeValue;
//read all pages main info
for (var pi = 0; pi < PageCount; pi++)
{
var flags = reader.ReadInt32();
var pageType = flags & 0b011;
if (pageType != Consts.BTreePageItemsFlag)
{
throw new ArgumentException("Invalid indexer");
}
var uniqueKeyValue = (flags & Consts.BTreeUniqueKeyValueFlag) != 0;
var offset = reader.ReadInt32();
var pageSize = reader.ReadInt32();
var itemsCount = reader.ReadInt32();
//skip keys and values
//sizeof: flags, offset, pageSize, itemsCount
var sizeOfInt32 = sizeof(Int32);
var dataStart = 4 * sizeOfInt32;
var skip = pageSize - dataStart;
reader.BaseStream.Seek(skip, io.SeekOrigin.Current);
var page = new MetaItemsPage <T>()
{
Flags = flags,
UniqueKeyValue = uniqueKeyValue,
Offset = offset,
PageSize = pageSize,
ItemsCount = itemsCount,
DataStart = dataStart,
Parent = this,
Frequency = 0.0,
Number = pi
};
//add to hash dictionary for fast retrieval
Hash.Add(page.Offset, page);
}
}
//update item page count
Index.ItemPages = Hash.Count;
}
