public ITable GetGroupValue(long rowid)
{
long n = (rowid * 2);
// Get the group position and size in the index
long groupPos = childGroupsIndex[n];
long groupSize = childGroupsIndex[n + 1];
// Create an interator over this subset of the filter index
SubsetRowCursor subset = new SubsetRowCursor(BaseTable.GetRowCursor(), groupPos, groupSize);
// Return the table subset
SubsetTable groupTable = new SubsetTable(BaseTable, subset);
// The subset retains the order of the child
groupTable.SetOrderCompositeIsChild();
// Return the group
return groupTable;
}
internal ITable FilterByScan(ITable table, Expression op)
{
// Default is to match table,
ITable resultTable = table;
long rowCount = table.RowCount;
// If the table is not empty,
if (rowCount > 0) {
// Put the table on the stack,
PushTable(table);
// The working set,
IIndex<RowId> workingSet = transaction.CreateTemporaryIndex<RowId>(rowCount);
// TODO: Common expression scans should be optimized
// Default scan (works for everything)
// Fetch the table's row iterator
IRowCursor cursor = table.GetRowCursor();
// Wrap in a forward prefetch iterator
cursor = new PrefetchRowCursor(cursor, table);
// True if all matched
bool allMatched = true;
// For each value,
while (cursor.MoveNext()) {
// Fetch the next row_id from the iterator
RowId rowid = cursor.Current;
// Set the top of stack table row_id
UpdateTableRow(rowid);
// Execute the expression,
ITable expResult = DoExecute(op);
// If it's true, add the row_id to the working set
if (BooleanResult(expResult)) {
// Note, we preserve the ordering of the table being filtered
workingSet.Add(rowid);
} else {
// Wasn't a true result, so we didn't all match.
allMatched = false;
}
}
// If we matched nothing
if (workingSet.Count == 0) {
// Return a subset of the given table that is empty
SubsetTable subsetTable = new SubsetTable(table);
// We inherit the order composite description from the child.
subsetTable.SetOrderCompositeIsChild();
resultTable = subsetTable;
}
// If we matched something
else {
// If all matched we return the table
if (allMatched) {
// Clear the working set and set the result table
workingSet.Clear();
resultTable = table;
} else {
// Something in working set, and we didn't match everything,
IRowCursor setCursor = new DefaultRowCursor(workingSet.GetCursor());
SubsetTable subsetTable = new SubsetTable(table, setCursor);
// We inherit the order composite description from the child.
subsetTable.SetOrderCompositeIsChild();
resultTable = subsetTable;
}
}
// Pop the current table from the stack
PopTable();
}
return resultTable;
}