public static IEnumerable <long> SelectRows(this ITable table, int column, Operator op, DataObject cell)
{
// If the cell is of an incompatible type, return no results,
DataType colType = table.TableInfo[column].DataType;
if (!cell.DataType.IsComparable(colType))
{
// Types not comparable, so return 0
return(new List <long>(0));
}
// Get the selectable scheme for this column
SelectableScheme ss = table.GetScheme(column);
// If the operator is a standard operator, use the interned SelectableScheme
// methods.
if (op.IsEquivalent(Operator.Equal))
{
return(ss.SelectEqual(cell));
}
if (op.IsEquivalent(Operator.NotEqual))
{
return(ss.SelectNotEqual(cell));
}
if (op.IsEquivalent(Operator.Greater))
{
return(ss.SelectGreater(cell));
}
if (op.IsEquivalent(Operator.Smaller))
{
return(ss.SelectLess(cell));
}
if (op.IsEquivalent(Operator.GreaterOrEqual))
{
return(ss.SelectGreaterOrEqual(cell));
}
if (op.IsEquivalent(Operator.SmallerOrEqual))
{
return(ss.SelectLessOrEqual(cell));
}
// If it's not a standard operator (such as IS, NOT IS, etc) we generate the
// range set especially.
SelectableRangeSet rangeSet = new SelectableRangeSet();
rangeSet.Intersect(op, cell);
return(ss.SelectRange(rangeSet.ToArray()));
}
/// <summary>
/// Calculates a list of <see cref="SelectableRange"/> objects that represent
/// the range of the expression.
/// </summary>
/// <param name="context"></param>
/// <param name="field"></param>
/// <param name="range"></param>
/// <param name="exp"></param>
private static void CalcRange(IQueryContext context, DataColumnInfo field, SelectableRangeSet range, Expression exp)
{
var binary = (BinaryExpression)exp;
Operator op = binary.Operator;
if (op.IsLogical())
{
if (op == Operator.And)
{
IList <Expression> andList = CreateAndList(new List <Expression>(), exp);
foreach (Expression expr in andList)
{
UpdateRange(context, range, field, expr);
}
}
else if (op == Operator.Or)
{
// Split left and right of logical operator.
Expression[] exps = { binary.Left, binary.Right };
// Calculate the range of the left and right
SelectableRangeSet left = new SelectableRangeSet();
CalcRange(context, field, left, exps[0]);
SelectableRangeSet right = new SelectableRangeSet();
CalcRange(context, field, right, exps[1]);
// Union the left and right range with the current range
range.Union(left);
range.Union(right);
}
else
{
throw new ApplicationException("Unrecognised logical operator.");
}
}
else
{
// Not an operator so this is the value.
UpdateRange(context, range, field, exp);
}
}
/// <summary>
/// Updates a range with the given expression.
/// </summary>
/// <param name="context"></param>
/// <param name="range"></param>
/// <param name="field"></param>
/// <param name="e"></param>
private static void UpdateRange(IQueryContext context, SelectableRangeSet range, DataColumnInfo field, Expression e)
{
var binary = (BinaryExpression)e;
Operator op = binary.Operator;
Expression[] exps = { binary.Left, binary.Right };
// Evaluate to an object
DataObject cell = exps[1].Evaluate(context);
// If the evaluated object is not of a comparable type, then it becomes
// null.
DataType fieldType = field.DataType;
if (!cell.DataType.IsComparable(fieldType))
{
cell = new DataObject(fieldType, null);
}
// Intersect this in the range set
range.Intersect(op, cell);
}
public override ITable Evaluate(IQueryContext context)
{
ITable t = Child.Evaluate(context);
Expression exp = expression;
// Assert that all variables in the expression are identical.
IEnumerable <ObjectName> allVars = exp.AllVariables();
ObjectName v = null;
foreach (ObjectName cv in allVars)
{
if (v != null && !cv.Equals(v))
{
throw new ApplicationException("Assertion failed: Range plan does not contain common variable.");
}
v = cv;
}
// Find the variable field in the table.
int col = ((Table)t).FindFieldName(v);
if (col == -1)
{
throw new ApplicationException("Couldn't find column reference in table: " + v);
}
DataColumnInfo field = t.TableInfo[col];
// Calculate the range
SelectableRangeSet range = new SelectableRangeSet();
CalcRange(context, field, range, exp);
// Select the range from the table
SelectableRange[] ranges = range.ToArray();
return(t.RangeSelect(v, ranges));
}