private IndexRangeSet CalcExpression(SqlExpression expression)
{
var indexRangeSet = new IndexRangeSet();
var calculator = new RangeSetCalculator(context, field, indexRangeSet);
return(calculator.Calculate(expression));
}
/// <inheritdoc/>
public override ITable Evaluate(IRequest context)
{
var t = Child.Evaluate(context);
var exp = Expression;
// Assert that all variables in the expression are identical.
var columnNames = exp.DiscoverReferences();
ObjectName columnName = null;
foreach (var cv in columnNames)
{
if (columnName != null && !cv.Equals(columnName))
{
throw new InvalidOperationException("Range plan does not contain common column.");
}
columnName = cv;
}
// Find the variable field in the table.
var col = t.IndexOfColumn(columnName);
if (col == -1)
{
throw new InvalidOperationException("Could not find column reference in table: " + columnName);
}
var field = t.TableInfo[col];
// Calculate the range
var range = new IndexRangeSet();
var calculator = new RangeSetCalculator(context, field, range);
range = calculator.Calculate(exp);
// Select the range from the table
var ranges = range.ToArray();
return(t.SelectRange(columnName, ranges));
}
public override SqlExpression VisitBinary(SqlBinaryExpression binaryEpression)
{
var op = binaryEpression.ExpressionType;
// Evaluate to an object
var value = binaryEpression.Right.EvaluateToConstant(context, null);
// If the evaluated object is not of a comparable type, then it becomes
// null.
var fieldType = field.ColumnType;
if (!value.Type.IsComparable(fieldType))
{
value = Field.Null(fieldType);
}
// Intersect this in the range set
indexRangeSet = indexRangeSet.Intersect(op, value);
return(base.VisitBinary(binaryEpression));
}
public override SqlExpression VisitBinary(SqlBinaryExpression binaryEpression)
{
if (binaryEpression.ExpressionType == SqlExpressionType.And)
{
rangeSet = UpdateRange(binaryEpression.Left);
rangeSet = UpdateRange(binaryEpression.Right);
}
else if (binaryEpression.ExpressionType == SqlExpressionType.Or)
{
var left = CalcExpression(binaryEpression.Left);
var right = CalcExpression(binaryEpression.Right);
rangeSet = rangeSet.Union(left);
rangeSet = rangeSet.Union(right);
}
else
{
rangeSet = UpdateRange(binaryEpression);
}
return(base.VisitBinary(binaryEpression));
}
public RangeSetCalculator(IRequest context, ColumnInfo field, IndexRangeSet rangeSet)
{
this.context = context;
this.field = field;
this.rangeSet = rangeSet;
}
public RangeSetUpdater(IRequest context, ColumnInfo field, IndexRangeSet indexRangeSet)
{
this.context = context;
this.field = field;
this.indexRangeSet = indexRangeSet;
}
