/// <summary>
/// Take the fields of the index and take value from the query
/// </summary>
/// <param name="index"> The index </param>
/// <returns> The key of the index </returns>
protected virtual IOdbComparable ComputeIndexKey(ClassInfoIndex index)
{
var attributesNames = ClassInfo.GetAttributeNames(index.AttributeIds);
var constraint = Query.GetCriteria();
var values = ((IInternalConstraint)constraint).GetValues();
return(IndexTool.BuildIndexKey(index.Name, values, attributesNames));
}