public CollationIndexResolver(ITable table, IndexCollation collation)
{
this.table = table;
// Resolve the column names in the table into index references
int sz = collation.Columns.Length;
columns = new int[sz];
TableName tname = table.Name;
for (int i = 0; i < sz; ++i) {
string colName = collation.Columns[i].ColumnName;
int colOffset = table.Columns.IndexOf(colName);
if (colOffset == -1)
throw new ApplicationException("Column '" + colName + "' not found.");
columns[i] = colOffset;
}
// TODO: handle function indexes
}
public SystemIndexSetDataSource CreateIndex(TableName onTable, string indexName, string indexType, IndexCollation collation)
{
CheckNotDisposed();
// Check the table name given is qualified
CheckTableNameQualified(onTable);
// We can't create an index that already exists
if (IndexExists(onTable, indexName)) {
throw new ApplicationException("Index '" + indexName + "' already exists");
}
string[] columnNames = new string[collation.Columns.Length];
bool[] columnOrders = new bool[columnNames.Length];
for (int i = 0; i < columnNames.Length; i++) {
columnNames[i] = collation.Columns[i].ColumnName;
columnOrders[i] = collation.Columns[i].Ascending;
}
ITableIndex index = state.CreateIndex(new IndexName(onTable, indexName), indexType, columnNames, columnOrders);
if (index == null)
throw new ApplicationException("Unable to create index.");
long indexId = state.CreateUniqueId(SystemTableNames.Index);
// Create the index object
SystemIndexSetDataSource indexSet = new SystemIndexSetDataSource(this, index);
// Add this index item
AddIndex(indexId, onTable, indexName, indexType, collation);
// Log the change in the journal
journal.AddEntry(JournalCommandCode.IndexAdd, indexId);
OnChanged();
// Put it in the local cache
indexMap[indexId] = indexSet;
// Return the index
return indexSet;
}
internal void AddIndex(long indexId, TableName onTable, string indexName, string type, IndexCollation collation)
{
IMutableTable indexTable = GetTable(SystemTableNames.Index);
TableRow row = indexTable.NewRow();
row.SetValue(0, indexId);
row.SetValue(1, onTable.Schema);
row.SetValue(2, onTable.Name);
row.SetValue(3, indexName);
row.SetValue(4, type);
row.SetValue(5, collation.Function);
row.SetValue(6, collation.Type.ToString());
row.SetValue(7, user.Name);
indexTable.Insert(row);
indexTable.Commit();
RowId insertRowId = row.Id;
IMutableTable indexColumnTable = GetTable(SystemTableNames.ColumnSet);
for (int i = 0; i < collation.Columns.Length; i++) {
CollationColumn column = collation.Columns[i];
row = indexColumnTable.NewRow();
row.SetValue(0, indexId);
row.SetValue(1, onTable.Schema);
row.SetValue(2, onTable.Name);
row.SetValue(3, indexName);
row.SetValue(4, i);
row.SetValue(5, column.ColumnName);
row.SetValue(6, column.Ascending);
indexColumnTable.Insert(row);
}
indexColumnTable.Commit();
// If this isn't an index on the INDEXES or TABLES tables,););););
if (!onTable.Equals(SystemTableNames.Tables) &&
!onTable.Equals(SystemTableNames.Index)) {
// Update the indexes
IIndexSetDataSource[] idxs = GetTableIndexes(SystemTableNames.Index);
foreach (IIndexSetDataSource i in idxs) {
i.Insert(insertRowId);
}
}
}
public void PerformSample(SystemTransaction transaction)
{
// Translate into tables and column names
ITable tableSource = transaction.GetTable(var.TableName);
// DOn't bother unless the table has 64 or more values
if (tableSource.RowCount < (DivisionPointCount * 2)) {
sampleCount = 0;
totalSize = 0;
return;
}
// The number of elements in total
totalSize = tableSource.RowCount;
// The actual number of samples,
sampleCount = (int)System.Math.Min(tableSource.RowCount / 2, MaxSampleCount);
String col_name = var.Name;
int colId = tableSource.Columns.IndexOf(var.Name);
// Work out the size
long size = tableSource.RowCount;
// The sample point difference
double sampleDiff = (double)size / sampleCount;
// The index of the tables used in sampling
IIndex<RowId> sampleIndex = transaction.CreateTemporaryIndex<RowId>(sampleCount);
// Create a RowIndexCollation for this
SqlType type;
type = tableSource.Columns[colId].Type;
IndexCollation collation = new IndexCollation(type, col_name);
// Create the collation object,
CollationIndexResolver resolver = new CollationIndexResolver(tableSource, collation);
// The row cursor
IRowCursor rowCursor = tableSource.GetRowCursor();
RowId[] sampleRowset = new RowId[sampleCount];
// First read in the row_ids we are sampling,
{
// The current sample point
double p = 0;
// The number read,
int samplesRead = 0;
// Make a sorted sample index of the dataset
while (samplesRead < sampleCount) {
long pos = ((long)p) - 1;
pos = System.Math.Min(pos, tableSource.RowCount - 2);
rowCursor.MoveTo(pos);
if (!rowCursor.MoveNext())
throw new SystemException();
RowId rowId = rowCursor.Current;
sampleRowset[samplesRead] = rowId;
// Should this be Math.random(sample_diff * 2) for random distribution
// of the samples?
p += sampleDiff;
++samplesRead;
}
}
// Now read the samples,
{
int samplePoint = 0;
foreach (RowId rowId in sampleRowset) {
// Hint ahead the samples we are picking,
if ((samplePoint % 24) == 0) {
for (int i = samplePoint;
i < samplePoint + 24 && i < sampleRowset.Length;
++i) {
tableSource.PrefetchValue(-1, sampleRowset[i]);
}
}
// Pick the sample and sort it,
SqlObject[] sample = new SqlObject[] { tableSource.GetValue(colId, rowId) };
sampleIndex.Insert(sample, rowId, resolver);
++samplePoint;
}
}
// Now extract the interesting sample points from the sorted set
IIndexCursor<RowId> samplesCursor = sampleIndex.GetCursor();
long sampleIndexSize = sampleIndex.Count;
double divisionDiff = sampleIndexSize / (DivisionPointCount - 1);
for (int i = 0; i < DivisionPointCount; ++i) {
long samplePoint = (long)(divisionDiff * i);
if (samplePoint >= sampleIndexSize) {
samplePoint = sampleIndexSize - 1;
}
samplesCursor.Position = samplePoint - 1;
if (!samplesCursor.MoveNext())
throw new SystemException();
RowId rowId = samplesCursor.Current;
divisionPoints[i] = tableSource.GetValue(colId, rowId);
}
// Clear the temporary index
sampleIndex.Clear();
}
