/// <exception cref="System.IO.IOException"></exception>
protected internal override bool FindRowImpl(IDictionary <string, object> rowPattern
)
{
IndexData indexData = _entryCursor.GetIndexData();
object[] rowValues = indexData.ConstructIndexRow(rowPattern);
if (rowValues == null)
{
// bummer, use the default table scan
return(base.FindRowImpl(rowPattern));
}
// sweet, we can use our index
if (!FindPotentialRow(rowValues, true))
{
// at end of index, no potential matches
return(false);
}
// find actual matching row
IDictionary <string, object> indexRowPattern = null;
if (rowPattern.Count == indexData.GetColumns().Count)
{
// the rowPattern matches our index columns exactly, so we can
// streamline our testing below
indexRowPattern = rowPattern;
}
else
{
// the rowPattern has more columns than just the index, so we need to
// do more work when testing below
indexRowPattern = new LinkedHashMap <string, object>();
foreach (IndexData.ColumnDescriptor idxCol in indexData.GetColumns())
{
indexRowPattern.Put(idxCol.GetName(), rowValues[idxCol.GetColumnIndex()]);
}
}
do
{
// there may be multiple columns which fit the pattern subset used by
// the index, so we need to keep checking until our index values no
// longer match
if (!CurrentRowMatches(indexRowPattern))
{
// there are no more rows which could possibly match
break;
}
// note, if rowPattern == indexRowPattern, no need to do an extra
// comparison with the current row
if ((rowPattern == indexRowPattern) || CurrentRowMatches(rowPattern))
{
// found it!
return(true);
}
}while (MoveToNextRow());
// none of the potential rows matched
return(false);
}