private static void Merge(Page A, Page B, RecordMatcher Comparer)
{
List <Record> x = new List <Record>();
int ptrA = 0, ptrB = 0;
while (ptrA < A.Count && ptrB < B.Count)
{
if (Comparer.Compare(A.Cache[ptrA], B.Cache[ptrB]) < 0)
{
x.Add(A.Cache[ptrA]);
ptrA++;
}
else
{
x.Add(B.Cache[ptrB]);
ptrB++;
}
}
while (ptrA < A.Count)
{
x.Add(A.Cache[ptrA]);
ptrA++;
}
while (ptrB < B.Count)
{
x.Add(B.Cache[ptrB]);
ptrB++;
}
A.Cache = x.GetRange(0, A.Count);
B.Cache = x.GetRange(A.Count, B.Count);
}
// Distinct Support //
public static void Distinct(Table Element, RecordWriter Writer, RecordMatcher Comparer)
{
// Check if the table is a heap //
if (!(Element is HeapTable))
{
throw new Exception("Can only sort a HeapTable");
}
if (Element.Header.IndexHeaders.Count != 0)
{
throw new Exception("Can not sort a table with indexes");
}
// Step 1: sort table //
Sort(Element, Comparer);
// Step 2: create a shell //
//Table t = Element.Host.CreateTempTable(Element.Columns);
// Step 3: open a reader //
RecordReader rr = Element.OpenReader();
// Step 4: write to the shell //
Record lag = null;
while (rr.CanAdvance)
{
Record current = rr.ReadNext();
if (lag == null)
{
Writer.Insert(current);
}
else if (Comparer.Compare(lag, current) != 0)
{
Writer.Insert(current);
}
lag = current;
}
}
