/// <summary>
/// Evalutes a Join
/// </summary>
/// <param name="context">Evaluation Context</param>
/// <returns></returns>
public BaseMultiset Evaluate(SparqlEvaluationContext context)
{
BaseMultiset initialInput = context.InputMultiset;
BaseMultiset lhsResult = context.Evaluate(_lhs);
context.CheckTimeout();
if (lhsResult is NullMultiset)
{
context.OutputMultiset = lhsResult;
}
else if (lhsResult.IsEmpty)
{
context.OutputMultiset = new NullMultiset();
}
else
{
// Only Execute the RHS if the LHS has some results
context.InputMultiset = lhsResult;
BaseMultiset rhsResult = context.Evaluate(_rhs);
context.CheckTimeout();
context.OutputMultiset = lhsResult.Join(rhsResult);
context.CheckTimeout();
}
context.InputMultiset = context.OutputMultiset;
return(context.OutputMultiset);
}
/// <summary>
/// Evaluates the Path in the given context.
/// </summary>
/// <param name="context">Evaluation Context.</param>
/// <returns></returns>
public override BaseMultiset Evaluate(SparqlEvaluationContext context)
{
// Try and generate an Algebra expression
// Make sure we don't generate clashing temporary variable IDs over the life of the
// Evaluation
PathTransformContext transformContext = new PathTransformContext(PathStart, PathEnd);
if (context["PathTransformID"] != null)
{
transformContext.NextID = (int)context["PathTransformID"];
}
ISparqlAlgebra algebra = Path.ToAlgebra(transformContext);
context["PathTransformID"] = transformContext.NextID;
// Now we can evaluate the resulting algebra
BaseMultiset initialInput = context.InputMultiset;
bool trimMode = context.TrimTemporaryVariables;
bool rigMode = Options.RigorousEvaluation;
try
{
// Must enable rigorous evaluation or we get incorrect interactions between property and non-property path patterns
Options.RigorousEvaluation = true;
// Note: We may need to preserve Blank Node variables across evaluations
// which we usually don't do BUT because of the way we translate only part of the path
// into an algebra at a time and may need to do further nested translate calls we do
// need to do this here
context.TrimTemporaryVariables = false;
BaseMultiset result = context.Evaluate(algebra);
// Also note that we don't trim temporary variables here even if we've set the setting back
// to enabled since a Trim will be done at the end of whatever BGP we are being evaluated in
// Once we have our results can join then into our input
context.OutputMultiset = initialInput.Join(result);
}
finally
{
context.TrimTemporaryVariables = trimMode;
Options.RigorousEvaluation = rigMode;
}
return(context.OutputMultiset);
}
/// <summary>
/// Evaluates the BINDINGS modifier
/// </summary>
/// <param name="context">Evaluation Context</param>
/// <returns></returns>
public BaseMultiset Evaluate(SparqlEvaluationContext context)
{
//Evalute the Pattern
BaseMultiset results = context.Evaluate(this._pattern);//this._pattern.Evaluate(context);
//If the result is Null/Identity/Empty
if (results is NullMultiset || results is IdentityMultiset || results.IsEmpty)
{
context.OutputMultiset = results;
return(results);
}
else
{
//Result is an Join from the results to the Input Bindings
context.OutputMultiset = results.Join(this._bindings.ToMultiset());
return(context.OutputMultiset);
}
}
