/// <summary>
/// Creates a new Multiset by flattening a Group Multiset
/// </summary>
/// <param name="multiset">Group Multiset</param>
internal Multiset(GroupMultiset multiset)
{
foreach (String var in multiset.Variables)
{
this.AddVariable(var);
}
foreach (ISet s in multiset.Sets)
{
this.Add(s.Copy());
}
}
/// <summary>
/// Applies the Projection to the results of Evaluating the Inner Pattern
/// </summary>
/// <param name="context">Evaluation Context</param>
/// <returns></returns>
public BaseMultiset Evaluate(SparqlEvaluationContext context)
{
try
{
context.InputMultiset = context.Evaluate(this._pattern);//this._pattern.Evaluate(context);
}
catch (RdfQueryTimeoutException)
{
//If not partial results throw the error
if (!context.Query.PartialResultsOnTimeout)
{
throw;
}
}
IEnumerable <SparqlVariable> vars;
if (context.Query != null)
{
vars = context.Query.Variables;
}
else
{
vars = this._variables;
}
//For Null and Identity Multisets this is just a simple selection
if (context.InputMultiset is NullMultiset)
{
context.InputMultiset = new Multiset(vars.Select(v => v.Name));
context.OutputMultiset = context.InputMultiset;
}
else if (context.InputMultiset is IdentityMultiset)
{
context.InputMultiset = new Multiset(vars.Select(v => v.Name));
Set s = new Set();
context.InputMultiset.Add(s);
context.OutputMultiset = context.InputMultiset;
}
//If we have a Group Multiset then Projection is more complex
GroupMultiset groupSet = null;
if (context.InputMultiset is GroupMultiset)
{
groupSet = (GroupMultiset)context.InputMultiset;
//Project all simple variables for the Groups here
foreach (SparqlVariable v in vars.Where(v => v.IsResultVariable && !v.IsProjection && !v.IsAggregate))
{
//Can only project a variable if it's used in the GROUP OR if it was assigned by a GROUP BY expression
if (context.Query != null)
{
if (!groupSet.ContainsVariable(v.Name) && !context.Query.GroupBy.Variables.Contains(v.Name) && !context.Query.GroupBy.ProjectableVariables.Contains(v.Name))
{
throw new RdfQueryException("Cannot project the variable ?" + v.Name + " since this Query contains Grouping(s) but the given Variable is not in the GROUP BY - use the SAMPLE aggregate if you need to sample this Variable");
}
}
//Project the value for each variable
if (!groupSet.ContainsVariable(v.Name))
{
//Simple Variable Projection used in GROUP BY so grab first value as all should be same
//for the group
context.OutputMultiset.AddVariable(v.Name);
foreach (int id in groupSet.SetIDs)
{
INode value = groupSet.Contents[groupSet.GroupSetIDs(id).First()][v.Name];
context.OutputMultiset[id].Add(v.Name, value);
}
}
}
}
else if (context.Query != null && context.Query.IsAggregate)
{
context.OutputMultiset = new Multiset();
}
//Project the rest of the Variables
Set aggSet = new Set();
foreach (SparqlVariable v in vars.Where(v => v.IsResultVariable))
{
if (groupSet == null)
{
context.InputMultiset.AddVariable(v.Name);
}
else
{
context.OutputMultiset.AddVariable(v.Name);
}
if (v.IsAggregate)
{
//Compute the Aggregate
if (groupSet != null)
{
context.InputMultiset = groupSet.Contents;
foreach (int id in groupSet.SetIDs)
{
INode aggValue = v.Aggregate.Apply(context, groupSet.GroupSetIDs(id));
context.OutputMultiset[id].Add(v.Name, aggValue);
}
context.InputMultiset = groupSet;
}
else
{
INode aggValue = v.Aggregate.Apply(context, context.InputMultiset.SetIDs);
aggSet.Add(v.Name, aggValue);
}
}
else if (v.IsProjection)
{
if (context.Query != null && context.Query.IsAggregate && context.Query.GroupBy == null)
{
throw new RdfQueryException("Cannot project an expression since this Query contains Aggregates and no GROUP BY");
}
else
{
//Compute the Value of the Projection Expression for each Set
foreach (int id in context.InputMultiset.SetIDs)
{
ISet s = context.InputMultiset[id];
try
{
INode temp = v.Projection.Evaluate(context, id);
s.Add(v.Name, temp);
}
catch (RdfQueryException)
{
s.Add(v.Name, null);
}
}
}
}
else
{
if (context.Query != null && context.Query.IsAggregate && context.Query.GroupBy == null)
{
//If this is an Aggregate without a GROUP BY projected variables are invalid
throw new RdfQueryException("Cannot project the variable ?" + v.Name + " since this Query contains Aggregates and no GROUP BY");
}
else if (context.Query != null && context.Query.IsAggregate && !context.Query.GroupBy.ProjectableVariables.Contains(v.Name))
{
//If this is an Aggregate with a GROUP BY projected variables are only valid if they occur in the GROUP BY
throw new RdfQueryException("Cannot project the variable ?" + v.Name + " since this Query contains Aggregates but the given Variable is not in the GROUP BY - use the SAMPLE aggregate if you need to access this variable");
}
//Otherwise we don't need to do anything with the Variable
}
}
if (context.Query != null && context.Query.IsAggregate && context.Query.GroupBy == null)
{
context.OutputMultiset.Add(aggSet);
}
else
{
context.OutputMultiset = context.InputMultiset;
}
return(context.OutputMultiset);
}
/// <summary>
/// Evaluates a Group By by generating a <see cref="GroupMultiset">GroupMultiset</see> from the Input Multiset
/// </summary>
/// <param name="context">SPARQL Evaluation Context</param>
/// <returns></returns>
public BaseMultiset Evaluate(SparqlEvaluationContext context)
{
BaseMultiset results = context.Evaluate(this._pattern);
context.InputMultiset = results;
//Identity/Null yields an empty multiset
if (context.InputMultiset is IdentityMultiset || context.InputMultiset is NullMultiset)
{
results = new Multiset();
}
GroupMultiset groupSet = new GroupMultiset(results);
List <BindingGroup> groups;
//Calculate Groups
if (context.Query.GroupBy != null)
{
groups = context.Query.GroupBy.Apply(context);
}
else if (this._grouping != null)
{
groups = this._grouping.Apply(context);
}
else
{
groups = new List <BindingGroup>()
{
new BindingGroup(results.SetIDs)
};
}
//Add Groups to the GroupMultiset
HashSet <String> vars = new HashSet <String>();
foreach (BindingGroup group in groups)
{
foreach (KeyValuePair <String, INode> assignment in group.Assignments)
{
if (vars.Contains(assignment.Key))
{
continue;
}
groupSet.AddVariable(assignment.Key);
vars.Add(assignment.Key);
}
groupSet.AddGroup(group);
}
//If grouping produced no groups and there are aggregates present
//then an implicit group is created
if (groups.Count == 0 && this._aggregates.Count > 0)
{
groupSet.AddGroup(new BindingGroup());
}
//Apply the aggregates
context.InputMultiset = groupSet;
context.Binder.SetGroupContext(true);
foreach (SparqlVariable var in this._aggregates)
{
if (!vars.Contains(var.Name))
{
groupSet.AddVariable(var.Name);
vars.Add(var.Name);
}
foreach (ISet s in groupSet.Sets)
{
try
{
INode value = var.Aggregate.Apply(context, groupSet.GroupSetIDs(s.ID));
s.Add(var.Name, value);
}
catch (RdfQueryException)
{
s.Add(var.Name, null);
}
}
}
context.Binder.SetGroupContext(false);
context.OutputMultiset = groupSet;
return(context.OutputMultiset);
}
/// <summary>
/// Creates a new Multiset by flattening a Group Multiset
/// </summary>
/// <param name="multiset">Group Multiset</param>
internal Multiset(GroupMultiset multiset)
{
foreach (String var in multiset.Variables)
{
this.AddVariable(var);
}
foreach (ISet s in multiset.Sets)
{
this.Add(s.Copy());
}
}
/// <summary>
/// Sets the Group Context for the Binder
/// </summary>
/// <param name="accessContents">Whether you want to access the Group Contents or the Groups themselves</param>
public override void SetGroupContext(bool accessContents)
{
if (accessContents)
{
if (this._context.InputMultiset is GroupMultiset)
{
this._groupSet = (GroupMultiset)this._context.InputMultiset;
this._context.InputMultiset = this._groupSet.Contents;
}
else
{
throw new RdfQueryException("Cannot set Group Context to access Contents data when the Input is not a Group Multiset");
}
}
else
{
if (this._groupSet != null)
{
this._context.InputMultiset = this._groupSet;
this._groupSet = null;
}
else
{
throw new RdfQueryException("Cannot set Group Context to acess Group data when there is no Group data available");
}
}
}
