/// <summary>
/// Sorts the given row set in the order of the scheme.
/// </summary>
/// <param name="rowSet"></param>
/// <remarks>
/// The values in <paramref name="rowSet"/> must be references to rows in
/// the domain of the table this scheme represents.
/// <para>
/// The returned set must be stable, meaning if values are equal they
/// keep the same ordering.
/// </para>
/// <para>
/// Note that the default implementation of this method can often be
/// optimized. For example, <see cref="InsertSearch"/> uses a secondary
/// RID list to sort items if the given list is over a certain size.
/// </para>
/// </remarks>
/// <returns>
/// Returns a <see cref="BlockIndex"/> that represents the given
/// <paramref name="rowSet"/> sorted in the order of this scheme.
/// </returns>
public IIndex <long> GetOrderedIndex(IList <long> rowSet)
{
// The length of the set to order
int rowSetLength = rowSet.Count;
// Trivial cases where sorting is not required:
// NOTE: We use readOnly objects to save some memory.
if (rowSetLength == 0)
{
return(EmptyList);
}
if (rowSetLength == 1)
{
return(OneList);
}
// This will be 'row set' sorted by its entry lookup. This must only
// contain indices to rowSet entries.
BlockIndex <long> newSet = new BlockIndex <long>();
if (rowSetLength <= 250000)
{
// If the subset is less than or equal to 250,000 elements, we generate
// an array in memory that contains all values in the set and we sort
// it. This requires use of memory from the heap but is faster than
// the no heap use method.
DataObject[] subsetList = new DataObject[rowSetLength];
for (int i = 0; i < rowSetLength; ++i)
{
subsetList[i] = GetCellContents(rowSet[i]);
}
// The comparator we use to sort
IIndexComparer <long> comparator = new SubsetIndexComparer(subsetList);
// Fill new_set with the set { 0, 1, 2, .... , row_set_length }
for (int i = 0; i < rowSetLength; ++i)
{
DataObject cell = subsetList[i];
newSet.InsertSort(cell, i, comparator);
}
}
else
{
// This is the no additional heap use method to sorting the sub-set.
// The comparator we use to sort
IIndexComparer <long> comparator = new SchemeIndexComparer(this, rowSet);
// Fill new_set with the set { 0, 1, 2, .... , row_set_length }
for (int i = 0; i < rowSetLength; ++i)
{
DataObject cell = GetCellContents(rowSet[i]);
newSet.InsertSort(cell, i, comparator);
}
}
return(newSet);
}
static ColumnIndex()
{
EmptyList = new BlockIndex <int>();
EmptyList.IsReadOnly = true;
OneList = new BlockIndex <int>();
OneList.Add(0);
OneList.IsReadOnly = true;
}
static SelectableScheme()
{
EmptyList = new BlockIndex <long>();
EmptyList.IsReadOnly = true;
OneList = new BlockIndex <long>();
OneList.Add(0);
OneList.IsReadOnly = true;
}
public IIndex <int> Order(IEnumerable <int> rows)
{
var rowSet = rows.ToList();
// The length of the set to order
int rowSetLength = rowSet.Count;
// Trivial cases where sorting is not required:
// NOTE: We use readOnly objects to save some memory.
if (rowSetLength == 0)
{
return(EmptyList);
}
if (rowSetLength == 1)
{
return(OneList);
}
// This will be 'row set' sorted by its entry lookup. This must only
// contain indices to rowSet entries.
var newSet = new BlockIndex <int>();
if (rowSetLength <= 250000)
{
// If the subset is less than or equal to 250,000 elements, we generate
// an array in memory that contains all values in the set and we sort
// it. This requires use of memory from the heap but is faster than
// the no heap use method.
var subsetList = new List <DataObject>(rowSetLength);
foreach (long row in rowSet)
{
subsetList.Add(GetValue(row));
}
// The comparator we use to sort
var comparer = new SubsetIndexComparer(subsetList.ToArray());
// Fill new_set with the set { 0, 1, 2, .... , row_set_length }
for (int i = 0; i < rowSetLength; ++i)
{
var cell = subsetList[i];
newSet.InsertSort(cell, i, comparer);
}
}
else
{
// This is the no additional heap use method to sorting the sub-set.
// The comparator we use to sort
var comparer = new IndexComparer(this, rowSet);
// Fill new_set with the set { 0, 1, 2, .... , row_set_length }
for (int i = 0; i < rowSetLength; ++i)
{
var cell = GetValue(rowSet[i]);
newSet.InsertSort(cell, i, comparer);
}
}
return(newSet);
}