/// <summary>
/// Calculates the product of two mutlisets asynchronously with a timeout to restrict long running computations
/// </summary>
/// <param name="multiset">Multiset</param>
/// <param name="other">Other Multiset</param>
/// <param name="timeout">Timeout, if <=0 no timeout is used and product will be computed sychronously</param>
/// <returns></returns>
public static BaseMultiset ProductWithTimeout(this BaseMultiset multiset, BaseMultiset other, long timeout)
{
if (other is IdentityMultiset) return multiset;
if (other is NullMultiset) return other;
if (other.IsEmpty) return new NullMultiset();
if (timeout <= 0)
{
return multiset.Product(other);
}
//Invoke using an Async call
Multiset productSet = new Multiset();
StopToken stop = new StopToken();
GenerateProductDelegate d = new GenerateProductDelegate(GenerateProduct);
IAsyncResult r = d.BeginInvoke(multiset, other, productSet, stop, null, null);
//Wait
int t = (int)Math.Min(timeout, Int32.MaxValue);
r.AsyncWaitHandle.WaitOne(t);
if (!r.IsCompleted)
{
stop.ShouldStop = true;
r.AsyncWaitHandle.WaitOne();
}
return productSet;
}
public void SparqlAlgebraJoinMultiVariable1()
{
ISet x = new Set();
x.Add("a", this._factory.CreateUriNode(UriFactory.Create("http://x")));
x.Add("b", this._factory.CreateUriNode(UriFactory.Create("http://y")));
ISet y1 = new Set();
y1.Add("a", this._factory.CreateUriNode(UriFactory.Create("http://x")));
y1.Add("b", this._factory.CreateUriNode(UriFactory.Create("http://y")));
ISet y2 = new Set();
y2.Add("a", this._factory.CreateUriNode(UriFactory.Create("http://x")));
y2.Add("b", this._factory.CreateUriNode(UriFactory.Create("http://y")));
BaseMultiset lhs = new Multiset();
lhs.Add(x);
BaseMultiset rhs = new Multiset();
rhs.Add(y1);
rhs.Add(y2);
BaseMultiset joined = lhs.Join(rhs);
Assert.AreEqual(2, joined.Count);
}
/// <summary>
/// Does a Product of this Multiset and another Multiset
/// </summary>
/// <param name="other">Other Multiset</param>
/// <returns></returns>
public override BaseMultiset Product(BaseMultiset other)
{
if (other is IdentityMultiset)
{
return(this);
}
if (other is NullMultiset)
{
return(other);
}
if (other.IsEmpty)
{
return(new NullMultiset());
}
Multiset productSet = new Multiset();
foreach (ISet x in this.Sets)
{
foreach (ISet y in other.Sets)
{
productSet.Add(x.Join(y));
}
}
return(productSet);
}
public void SparqlAlgebraJoinMultiVariable4()
{
ISet x1 = new Set();
x1.Add("a", this._factory.CreateUriNode(UriFactory.Create("http://x1")));
x1.Add("b", this._factory.CreateUriNode(UriFactory.Create("http://y1")));
ISet x2 = new Set();
x2.Add("a", this._factory.CreateUriNode(UriFactory.Create("http://x2")));
x2.Add("b", this._factory.CreateUriNode(UriFactory.Create("http://y2")));
ISet y1 = new Set();
y1.Add("a", this._factory.CreateUriNode(UriFactory.Create("http://x1")));
y1.Add("b", this._factory.CreateUriNode(UriFactory.Create("http://y2")));
ISet y2 = new Set();
y2.Add("a", this._factory.CreateUriNode(UriFactory.Create("http://x2")));
y2.Add("b", this._factory.CreateUriNode(UriFactory.Create("http://y1")));
BaseMultiset lhs = new Multiset();
lhs.Add(x1);
lhs.Add(x2);
BaseMultiset rhs = new Multiset();
rhs.Add(y1);
rhs.Add(y2);
BaseMultiset joined = lhs.Join(rhs);
Assert.Equal(0, joined.Count);
}
/// <summary>
/// Does a Union of this Multiset and another Multiset.
/// </summary>
/// <param name="other">Other Multiset.</param>
/// <returns></returns>
public override BaseMultiset Union(BaseMultiset other)
{
if (other is IdentityMultiset)
{
return(this);
}
if (other is NullMultiset)
{
return(this);
}
if (other.IsEmpty)
{
return(this);
}
Multiset m = new Multiset();
foreach (ISet s in this.Sets)
{
m.Add(s.Copy());
}
foreach (ISet s in other.Sets)
{
m.Add(s.Copy());
}
return(m);
}
/// <summary>
/// Does a Product of this Multiset and another Multiset.
/// </summary>
/// <param name="other">Other Multiset.</param>
/// <returns></returns>
public virtual BaseMultiset Product(BaseMultiset other)
{
if (other is IdentityMultiset)
{
return(this);
}
if (other is NullMultiset)
{
return(other);
}
if (other.IsEmpty)
{
return(new NullMultiset());
}
#if NET40
if (Options.UsePLinqEvaluation)
{
// Determine partition sizes so we can do a parallel product
// Want to parallelize over whichever side is larger
PartitionedMultiset partitionedSet;
if (this.Count >= other.Count)
{
partitionedSet = new PartitionedMultiset(this.Count, other.Count);
this.Sets.AsParallel().ForAll(x => this.EvalProduct(x, other, partitionedSet));
}
else
{
partitionedSet = new PartitionedMultiset(other.Count, this.Count);
other.Sets.AsParallel().ForAll(y => this.EvalProduct(y, this, partitionedSet));
}
return(partitionedSet);
}
else
{
// Use serial calculation which is likely to really suck for big products
Multiset productSet = new Multiset();
foreach (ISet x in this.Sets)
{
foreach (ISet y in other.Sets)
{
productSet.Add(x.Join(y));
}
}
return(productSet);
}
#else
// Use serial calculation which is likely to really suck for big products
var productSet = new Multiset();
foreach (var x in Sets)
{
foreach (var y in other.Sets)
{
productSet.Add(x.Join(y));
}
}
return(productSet);
#endif
}
/// <summary>
/// Calculates the product of two mutlisets asynchronously with a timeout to restrict long running computations
/// </summary>
/// <param name="multiset">Multiset</param>
/// <param name="other">Other Multiset</param>
/// <param name="timeout">Timeout, if <=0 no timeout is used and product will be computed sychronously</param>
/// <returns></returns>
public static BaseMultiset ProductWithTimeout(this BaseMultiset multiset, BaseMultiset other, long timeout)
{
if (other is IdentityMultiset)
{
return(multiset);
}
if (other is NullMultiset)
{
return(other);
}
if (other.IsEmpty)
{
return(new NullMultiset());
}
//If no timeout use default implementation
if (timeout <= 0)
{
return(multiset.Product(other));
}
//Otherwise Invoke using an Async call
BaseMultiset productSet;
#if NET40 && !SILVERLIGHT
if (Options.UsePLinqEvaluation)
{
if (multiset.Count >= other.Count)
{
productSet = new PartitionedMultiset(multiset.Count, other.Count);
}
else
{
productSet = new PartitionedMultiset(other.Count, multiset.Count);
}
}
else
{
#endif
productSet = new Multiset();
#if NET40 && !SILVERLIGHT
}
#endif
StopToken stop = new StopToken();
GenerateProductDelegate d = new GenerateProductDelegate(GenerateProduct);
IAsyncResult r = d.BeginInvoke(multiset, other, productSet, stop, null, null);
//Wait
int t = (int)Math.Min(timeout, Int32.MaxValue);
r.AsyncWaitHandle.WaitOne(t);
if (!r.IsCompleted)
{
stop.ShouldStop = true;
r.AsyncWaitHandle.WaitOne();
}
return(productSet);
}
/// <summary>
/// Calculates the product of two multi-sets asynchronously with a timeout to restrict long running computations.
/// </summary>
/// <param name="multiset">Multiset.</param>
/// <param name="other">Other Multiset.</param>
/// <param name="timeout">Timeout, if <=0 no timeout is used and product will be computed synchronously.</param>
/// <returns></returns>
public static BaseMultiset ProductWithTimeout(this BaseMultiset multiset, BaseMultiset other, long timeout)
{
if (other is IdentityMultiset)
{
return(multiset);
}
if (other is NullMultiset)
{
return(other);
}
if (other.IsEmpty)
{
return(new NullMultiset());
}
// If no timeout use default implementation
if (timeout <= 0)
{
return(multiset.Product(other));
}
// Otherwise Invoke using an Async call
BaseMultiset productSet;
if (Options.UsePLinqEvaluation)
{
if (multiset.Count >= other.Count)
{
productSet = new PartitionedMultiset(multiset.Count, other.Count);
}
else
{
productSet = new PartitionedMultiset(other.Count, multiset.Count);
}
}
else
{
productSet = new Multiset();
}
var stop = new StopToken();
var t = (int)Math.Min(timeout, int.MaxValue);
var productTask = Task.Factory.StartNew(() => GenerateProduct(multiset, other, productSet, stop));
if (!productTask.Wait(t))
{
stop.ShouldStop = true;
productTask.Wait();
}
return(productSet);
}
/// <summary>
/// Joins this Multiset to another Multiset
/// </summary>
/// <param name="other">Other Multiset</param>
/// <returns></returns>
public override BaseMultiset Join(BaseMultiset other)
{
//If the Other is the Identity Multiset the result is this Multiset
if (other is IdentityMultiset)
{
return(this);
}
//If the Other is the Null Multiset the result is the Null Multiset
if (other is NullMultiset)
{
return(other);
}
//If the Other is Empty then the result is the Null Multiset
if (other.IsEmpty)
{
return(new NullMultiset());
}
//Find the First Variable from this Multiset which is in both Multisets
//If there is no Variable from this Multiset in the other Multiset then this
//should be a Join operation instead of a LeftJoin
List <String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0)
{
return(this.Product(other));
}
//Start building the Joined Set
Multiset joinedSet = new Multiset();
foreach (ISet x in this.Sets)
{
//For sets to be compatible for every joinable variable they must either have a null for the
//variable in one of the sets or if they have values the values must be equal
////This first check is to try speed things up, it looks whether there are solutions that may match
////without needing to do a full table scan of the RHS results as the subsequent LINQ call will do
////if (!joinVars.All(v => x[v] == null || other.ContainsValue(v, x[v]) || other.ContainsValue(v, null))) continue;
IEnumerable <ISet> ys = other.Sets.Where(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
//IEnumerable<ISet> ys = other.Sets.Where(s => s.IsCompatibleWith(x, joinVars));
foreach (ISet y in ys)
{
joinedSet.Add(x.Join(y));
}
}
return(joinedSet);
}
public void SparqlAlgebraJoinSingleVariable1()
{
ISet x = new Set();
x.Add("a", this._factory.CreateUriNode(UriFactory.Create("http://x")));
BaseMultiset lhs = new Multiset();
lhs.Add(x);
BaseMultiset rhs = new Multiset();
rhs.Add(x);
BaseMultiset joined = lhs.Join(rhs);
Assert.AreEqual(1, joined.Count);
}
/// <summary>
/// Does a Minus Join of this Multiset to another Multiset where any joinable results are subtracted from this Multiset to give the resulting Multiset
/// </summary>
/// <param name="other">Other Multiset</param>
/// <returns></returns>
public override BaseMultiset MinusJoin(BaseMultiset other)
{
//If the other Multiset is the Identity/Null Multiset then minus-ing it doesn't alter this set
if (other is IdentityMultiset)
{
return(this);
}
if (other is NullMultiset)
{
return(this);
}
//If the other Multiset is disjoint then minus-ing it also doesn't alter this set
if (this.IsDisjointWith(other))
{
return(this);
}
//Find the Variables that are to be used for Joining
List <String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0)
{
return(this.Product(other));
}
//Start building the Joined Set
Multiset joinedSet = new Multiset();
foreach (ISet x in this.Sets)
{
//New Minus logic based on the improved Join() logic
bool minus = other.Sets.Any(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
//If no compatible sets then this set is preserved
if (!minus)
{
joinedSet.Add(x);
}
}
return(joinedSet);
}
/// <summary>
/// Calculates the product of two mutlisets asynchronously with a timeout to restrict long running computations
/// </summary>
/// <param name="multiset">Multiset</param>
/// <param name="other">Other Multiset</param>
/// <param name="timeout">Timeout, if <=0 no timeout is used and product will be computed sychronously</param>
/// <returns></returns>
public static BaseMultiset ProductWithTimeout(this BaseMultiset multiset, BaseMultiset other, long timeout)
{
if (other is IdentityMultiset)
{
return(multiset);
}
if (other is NullMultiset)
{
return(other);
}
if (other.IsEmpty)
{
return(new NullMultiset());
}
if (timeout <= 0)
{
return(multiset.Product(other));
}
//Invoke using an Async call
Multiset productSet = new Multiset();
StopToken stop = new StopToken();
GenerateProductDelegate d = new GenerateProductDelegate(GenerateProduct);
IAsyncResult r = d.BeginInvoke(multiset, other, productSet, stop, null, null);
//Wait
int t = (int)Math.Min(timeout, Int32.MaxValue);
r.AsyncWaitHandle.WaitOne(t);
if (!r.IsCompleted)
{
stop.ShouldStop = true;
r.AsyncWaitHandle.WaitOne();
}
return(productSet);
}
/// <summary>
/// Creates a new Multiset Handler
/// </summary>
/// <param name="mset">Multiset</param>
public MultisetHandler(Multiset mset)
{
if (mset == null) throw new ArgumentNullException("mset", "Multiset to load into cannot be null");
this._mset = mset;
}
/// <summary>
/// Does a Left Join of this Multiset to another Multiset where the Join is predicated on the given Expression
/// </summary>
/// <param name="other">Other Multiset</param>
/// <param name="expr">Expression</param>
/// <returns></returns>
public override BaseMultiset LeftJoin(BaseMultiset other, ISparqlExpression expr)
{
//If the Other is the Identity/Null Multiset the result is this Multiset
if (other is IdentityMultiset) return this;
if (other is NullMultiset) return this;
if (other.IsEmpty) return this;
Multiset joinedSet = new Multiset();
LeviathanLeftJoinBinder binder = new LeviathanLeftJoinBinder(joinedSet);
SparqlEvaluationContext subcontext = new SparqlEvaluationContext(binder);
//Find the First Variable from this Multiset which is in both Multisets
//If there is no Variable from this Multiset in the other Multiset then this
//should be a Join operation instead of a LeftJoin
List<String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0)
{
//Calculate a Product filtering as we go
foreach (ISet x in this.Sets)
{
bool standalone = false;
foreach (ISet y in other.Sets)
{
ISet z = x.Join(y);
try
{
joinedSet.Add(z);
if (!expr.Evaluate(subcontext, z.ID).AsSafeBoolean())
{
joinedSet.Remove(z.ID);
standalone = true;
}
}
catch
{
joinedSet.Remove(z.ID);
standalone = true;
}
}
if (standalone) joinedSet.Add(x.Copy());
}
}
else
{
//This is the old algorithm which is correct but has complexity O(n^2) so it scales terribly
//foreach (ISet x in this.Sets)
//{
// IEnumerable<ISet> ys = other.Sets.Where(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
// //IEnumerable<ISet> ys = other.Sets.Where(s => s.IsCompatibleWith(x, joinVars));
// bool standalone = false;
// int i = 0;
// foreach (ISet y in ys)
// {
// i++;
// ISet z = x.Join(y);
// try
// {
// joinedSet.Add(z);
// if (!expr.Evaluate(subcontext, z.ID).AsSafeBoolean())
// {
// joinedSet.Remove(z.ID);
// standalone = true;
// }
// }
// catch
// {
// joinedSet.Remove(z.ID);
// standalone = true;
// }
// }
// if (standalone || i == 0) joinedSet.Add(x);
//}
//This is the new Join algorithm which is also correct but is O(2n) so much faster and scalable
//Downside is that it does require more memory than the old algorithm
List<HashTable<INode, int>> values = new List<HashTable<INode, int>>();
List<List<int>> nulls = new List<List<int>>();
foreach (String var in joinVars)
{
values.Add(new HashTable<INode, int>(HashTableBias.Enumeration));
nulls.Add(new List<int>());
}
//First do a pass over the LHS Result to find all possible values for joined variables
HashSet<int> matched = new HashSet<int>();
HashSet<int> standalone = new HashSet<int>();
foreach (ISet x in this.Sets)
{
int i = 0;
foreach (String var in joinVars)
{
INode value = x[var];
if (value != null)
{
values[i].Add(value, x.ID);
}
else
{
nulls[i].Add(x.ID);
}
i++;
}
}
//Then do a pass over the RHS and work out the intersections
foreach (ISet y in other.Sets)
{
IEnumerable<int> possMatches = null;
int i = 0;
foreach (String var in joinVars)
{
INode value = y[var];
if (value != null)
{
if (values[i].ContainsKey(value))
{
possMatches = (possMatches == null ? values[i].GetValues(value).Concat(nulls[i]) : possMatches.Intersect(values[i].GetValues(value).Concat(nulls[i])));
}
else
{
possMatches = Enumerable.Empty<int>();
break;
}
}
else
{
//Don't forget that a null will be potentially compatible with everything
possMatches = (possMatches == null ? this.SetIDs : possMatches.Intersect(this.SetIDs));
}
i++;
}
if (possMatches == null) continue;
//Now do the actual joins for the current set
//Note - We access the dictionary directly here because going through the this[int id] method
//incurs a Contains() call each time and we know the IDs must exist because they came from
//our dictionary originally!
foreach (int poss in possMatches)
{
if (this._sets[poss].IsCompatibleWith(y, joinVars))
{
ISet z = this._sets[poss].Join(y);
joinedSet.Add(z);
try
{
if (!expr.Evaluate(subcontext, z.ID).AsSafeBoolean())
{
joinedSet.Remove(z.ID);
standalone.Add(poss);
}
else
{
matched.Add(poss);
}
}
catch
{
joinedSet.Remove(z.ID);
standalone.Add(poss);
}
}
}
}
//Finally add in unmatched sets from LHS
foreach (int id in this.SetIDs)
{
if (!matched.Contains(id) || standalone.Contains(id)) joinedSet.Add(this._sets[id].Copy());
}
}
return joinedSet;
}
/// <summary>
/// Does a Product of this Multiset and another Multiset
/// </summary>
/// <param name="other">Other Multiset</param>
/// <returns></returns>
public override BaseMultiset Product(BaseMultiset other)
{
if (other is IdentityMultiset) return this;
if (other is NullMultiset) return other;
if (other.IsEmpty) return new NullMultiset();
Multiset productSet = new Multiset();
foreach (ISet x in this.Sets)
{
foreach (ISet y in other.Sets)
{
productSet.Add(x.Join(y));
}
}
return productSet;
}
/// <summary>
/// Evaluates the Graph Clause by setting up the dataset, applying the pattern and then generating additional bindings if necessary
/// </summary>
/// <param name="context">Evaluation Context</param>
/// <returns></returns>
public BaseMultiset Evaluate(SparqlEvaluationContext context)
{
BaseMultiset result;
//Q: Can we optimise GRAPH when the input is the Null Multiset to just return the Null Multiset?
if (this._pattern is Bgp && ((Bgp)this._pattern).IsEmpty)
{
//Optimise the case where we have GRAPH ?g {} by not setting the Graph and just returning
//a Null Multiset
result = new NullMultiset();
}
else
{
bool datasetOk = false;
try
{
List<String> activeGraphs = new List<string>();
//Get the URIs of Graphs that should be evaluated over
if (this._graphSpecifier.TokenType != Token.VARIABLE)
{
switch (this._graphSpecifier.TokenType)
{
case Token.URI:
case Token.QNAME:
Uri activeGraphUri = UriFactory.Create(Tools.ResolveUriOrQName(this._graphSpecifier, context.Query.NamespaceMap, context.Query.BaseUri));
if (context.Data.HasGraph(activeGraphUri))
{
//If the Graph is explicitly specified and there are FROM NAMED present then the Graph
//URI must be in the graphs specified by a FROM NAMED or the result is null
if (context.Query == null || !context.Query.NamedGraphs.Any() || context.Query.NamedGraphs.Any(u => EqualityHelper.AreUrisEqual(activeGraphUri, u)))
{
//Either there was no Query
//OR there were no Named Graphs (hence any Graph URI is permitted)
//OR the specified URI was a Named Graph URI
//In any case we can go ahead and set the active Graph
activeGraphs.Add(activeGraphUri.ToString());
}
else
{
//The specified URI was not present in the Default/Named Graphs so return null
context.OutputMultiset = new NullMultiset();
return context.OutputMultiset;
}
}
else
{
//If specifies a specific Graph and not in the Dataset result is a null multiset
context.OutputMultiset = new NullMultiset();
return context.OutputMultiset;
}
break;
default:
throw new RdfQueryException("Cannot use a '" + this._graphSpecifier.GetType().ToString() + "' Token to specify the Graph for a GRAPH clause");
}
}
else
{
String gvar = this._graphSpecifier.Value.Substring(1);
//Watch out for the case in which the Graph Variable is not bound for all Sets in which case
//we still need to operate over all Graphs
if (context.InputMultiset.ContainsVariable(gvar) && context.InputMultiset.Sets.All(s => s[gvar] != null))
{
//If there are already values bound to the Graph variable for all Input Solutions then we limit the Query to those Graphs
List<Uri> graphUris = new List<Uri>();
foreach (ISet s in context.InputMultiset.Sets)
{
INode temp = s[gvar];
if (temp != null)
{
if (temp.NodeType == NodeType.Uri)
{
activeGraphs.Add(temp.ToString());
graphUris.Add(((IUriNode)temp).Uri);
}
}
}
}
else
{
//Nothing yet bound to the Graph Variable so the Query is over all the named Graphs
if (context.Query != null && context.Query.NamedGraphs.Any())
{
//Query specifies one/more named Graphs
activeGraphs.AddRange(context.Query.NamedGraphs.Select(u => u.ToString()));
}
else
{
//Query is over entire dataset/default Graph since no named Graphs are explicitly specified
activeGraphs.AddRange(context.Data.GraphUris.Select(u => u.ToSafeString()));
}
}
}
//Remove all duplicates from Active Graphs to avoid duplicate results
activeGraphs = activeGraphs.Distinct().ToList();
//Evaluate the inner pattern
BaseMultiset initialInput = context.InputMultiset;
BaseMultiset finalResult = new Multiset();
//Evalute for each Graph URI and union the results
foreach (String uri in activeGraphs)
{
//Always use the same Input for each Graph URI and set that Graph to be the Active Graph
//Be sure to translate String.Empty back to the null URI to select the default graph
//correctly
context.InputMultiset = initialInput;
Uri currGraphUri = (uri.Equals(String.Empty)) ? null : UriFactory.Create(uri);
//Set Active Graph
if (currGraphUri == null)
{
//GRAPH operates over named graphs only so default graph gets skipped
continue;
}
else
{
//The result of the HasGraph() call is ignored we just make it so datasets with any kind of
//load on demand behaviour work properly
context.Data.HasGraph(currGraphUri);
//All we actually care about is setting the active graph
context.Data.SetActiveGraph(currGraphUri);
}
datasetOk = true;
//Evaluate for the current Active Graph
result = context.Evaluate(this._pattern);
//Merge the Results into our overall Results
if (result is NullMultiset || result is IdentityMultiset)
{
//Don't do anything
}
else
{
//If the Graph Specifier is a Variable then we must either bind the
//variable or eliminate solutions which have an incorrect value for it
if (this._graphSpecifier.TokenType == Token.VARIABLE)
{
String gvar = this._graphSpecifier.Value.Substring(1);
INode currGraph = (currGraphUri == null) ? null : new UriNode(null, currGraphUri);
foreach (int id in result.SetIDs.ToList())
{
ISet s = result[id];
if (s[gvar] == null)
{
//If Graph Variable is not yet bound for solution bind it
s.Add(gvar, currGraph);
}
else if (!s[gvar].Equals(currGraph))
{
//If Graph Variable is bound for solution and doesn't match
//current Graph then we have to remove the solution
result.Remove(id);
}
}
}
//Union solutions into the Results
finalResult.Union(result);
}
//Reset the Active Graph after each pass
context.Data.ResetActiveGraph();
datasetOk = false;
}
//Return the final result
if (finalResult.IsEmpty) finalResult = new NullMultiset();
context.OutputMultiset = finalResult;
}
finally
{
if (datasetOk) context.Data.ResetActiveGraph();
}
}
return context.OutputMultiset;
}
/// <summary>
/// Does an Exists Join of this Multiset to another Multiset where the Join is predicated on the existence/non-existence of a joinable solution on the RHS
/// </summary>
/// <param name="other">Other Multiset</param>
/// <param name="mustExist">Whether a solution must exist in the Other Multiset for the join to be made</param>
/// <returns></returns>
public override BaseMultiset ExistsJoin(BaseMultiset other, bool mustExist)
{
//For EXISTS and NOT EXISTS if the other is the Identity then it has no effect
if (other is IdentityMultiset) return this;
if (mustExist)
{
//If an EXISTS then Null/Empty Other results in Null
if (other is NullMultiset) return other;
if (other.IsEmpty) return new NullMultiset();
}
else
{
//If a NOT EXISTS then Null/Empty results in this
if (other is NullMultiset) return this;
if (other.IsEmpty) return this;
}
//Find the Variables that are to be used for Joining
List<String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0)
{
//All Disjoint Solutions are compatible
if (mustExist)
{
//If an EXISTS and disjoint then result is this
return this;
}
else
{
//If a NOT EXISTS and disjoint then result is null
return new NullMultiset();
}
}
//Start building the Joined Set
Multiset joinedSet = new Multiset();
//This is the old algorithm which is correct but naive with worse case O(n^2)
//foreach (ISet x in this.Sets)
//{
// //New ExistsJoin() logic based on the improved Join() logic
// bool exists = other.Sets.Any(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
// //bool exists = other.Sets.Any(s => s.IsCompatibleWith(x, joinVars));
// if (exists)
// {
// //If there are compatible sets and this is an EXIST then preserve the solution
// if (mustExist) joinedSet.Add(x);
// }
// else
// {
// //If there are no compatible sets and this is a NOT EXISTS then preserve the solution
// if (!mustExist) joinedSet.Add(x);
// }
//}
//This is the new algorithm which is also correct but is O(3n) so much faster and scalable
//Downside is that it does require more memory than the old algorithm
List<HashTable<INode, int>> values = new List<HashTable<INode, int>>();
List<List<int>> nulls = new List<List<int>>();
foreach (String var in joinVars)
{
values.Add(new HashTable<INode, int>(HashTableBias.Enumeration));
nulls.Add(new List<int>());
}
//First do a pass over the LHS Result to find all possible values for joined variables
foreach (ISet x in this.Sets)
{
int i = 0;
foreach (String var in joinVars)
{
INode value = x[var];
if (value != null)
{
values[i].Add(value, x.ID);
}
else
{
nulls[i].Add(x.ID);
}
i++;
}
}
//Then do a pass over the RHS and work out the intersections
HashSet<int> exists = new HashSet<int>();
foreach (ISet y in other.Sets)
{
IEnumerable<int> possMatches = null;
int i = 0;
foreach (String var in joinVars)
{
INode value = y[var];
if (value != null)
{
if (values[i].ContainsKey(value))
{
possMatches = (possMatches == null ? values[i].GetValues(value).Concat(nulls[i]) : possMatches.Intersect(values[i].GetValues(value).Concat(nulls[i])));
}
else
{
possMatches = Enumerable.Empty<int>();
break;
}
}
else
{
//Don't forget that a null will be potentially compatible with everything
possMatches = (possMatches == null ? this.SetIDs : possMatches.Intersect(this.SetIDs));
}
i++;
}
if (possMatches == null) continue;
//Look at possible matches, if is a valid match then mark the set as having an existing match
//Don't reconsider sets which have already been marked as having an existing match
foreach (int poss in possMatches)
{
if (exists.Contains(poss)) continue;
if (this._sets[poss].IsCompatibleWith(y, joinVars))
{
exists.Add(poss);
}
}
}
//Apply the actual exists
if (exists.Count == this.Count)
{
//If number of sets that have a match is equal to number of sets then we're either returning everything or nothing
if (mustExist)
{
return this;
}
else
{
return new NullMultiset();
}
}
else
{
//Otherwise iterate
foreach (ISet x in this.Sets)
{
if (mustExist)
{
if (exists.Contains(x.ID))
{
joinedSet.Add(x.Copy());
}
}
else
{
if (!exists.Contains(x.ID))
{
joinedSet.Add(x.Copy());
}
}
}
}
return joinedSet;
}
/// <summary>
/// Evaluates the Graph Clause by setting up the dataset, applying the pattern and then generating additional bindings if necessary
/// </summary>
/// <param name="context">Evaluation Context</param>
/// <returns></returns>
public BaseMultiset Evaluate(SparqlEvaluationContext context)
{
BaseMultiset result;
//Q: Can we optimise GRAPH when the input is the Null Multiset to just return the Null Multiset?
if (this._pattern is Bgp && ((Bgp)this._pattern).IsEmpty)
{
//Optimise the case where we have GRAPH ?g {} by not setting the Graph and just returning
//a Null Multiset
result = new NullMultiset();
}
else
{
bool datasetOk = false;
try
{
List <String> activeGraphs = new List <string>();
//Get the URIs of Graphs that should be evaluated over
if (this._graphSpecifier.TokenType != Token.VARIABLE)
{
switch (this._graphSpecifier.TokenType)
{
case Token.URI:
case Token.QNAME:
Uri activeGraphUri = new Uri(Tools.ResolveUriOrQName(this._graphSpecifier, context.Query.NamespaceMap, context.Query.BaseUri));
if (context.Data.HasGraph(activeGraphUri))
{
//If the Graph is explicitly specified and there are FROM NAMED present then the Graph
//URI must be in the graphs specified by a FROM NAMED or the result is null
if (context.Query != null &&
((!context.Query.DefaultGraphs.Any() && !context.Query.NamedGraphs.Any()) ||
context.Query.DefaultGraphs.Any(u => EqualityHelper.AreUrisEqual(activeGraphUri, u)) ||
context.Query.NamedGraphs.Any(u => EqualityHelper.AreUrisEqual(activeGraphUri, u)))
)
{
//Either there was no Query OR there were no Default/Named Graphs OR
//the specified URI was either a Default/Named Graph URI
//In any case we can go ahead and set the active Graph
activeGraphs.Add(activeGraphUri.ToString());
}
else
{
//The specified URI was not present in the Default/Named Graphs so return null
context.OutputMultiset = new NullMultiset();
return(context.OutputMultiset);
}
}
else
{
//If specifies a specific Graph and not in the Dataset result is a null multiset
context.OutputMultiset = new NullMultiset();
return(context.OutputMultiset);
}
break;
default:
throw new RdfQueryException("Cannot use a '" + this._graphSpecifier.GetType().ToString() + "' Token to specify the Graph for a GRAPH clause");
}
}
else
{
String gvar = this._graphSpecifier.Value.Substring(1);
//Watch out for the case in which the Graph Variable is not bound for all Sets in which case
//we still need to operate over all Graphs
if (context.InputMultiset.ContainsVariable(gvar) && context.InputMultiset.Sets.All(s => s[gvar] != null))
{
//If there are already values bound to the Graph variable for all Input Solutions then we limit the Query to those Graphs
List <Uri> graphUris = new List <Uri>();
foreach (ISet s in context.InputMultiset.Sets)
{
INode temp = s[gvar];
if (temp != null)
{
if (temp.NodeType == NodeType.Uri)
{
activeGraphs.Add(temp.ToString());
graphUris.Add(((IUriNode)temp).Uri);
}
}
}
}
else
{
//Nothing yet bound to the Graph Variable so the Query is over all the named Graphs
if (context.Query != null && context.Query.NamedGraphs.Any())
{
//Query specifies one/more named Graphs
activeGraphs.AddRange(context.Query.NamedGraphs.Select(u => u.ToString()));
}
else
{
//Query is over entire dataset/default Graph since no named Graphs are explicitly specified
activeGraphs.AddRange(context.Data.GraphUris.Select(u => u.ToSafeString()));
}
}
}
//Remove all duplicates from Active Graphs to avoid duplicate results
activeGraphs = activeGraphs.Distinct().ToList();
//Evaluate the inner pattern
BaseMultiset initialInput = context.InputMultiset;
BaseMultiset finalResult = new Multiset();
//Evalute for each Graph URI and union the results
foreach (String uri in activeGraphs)
{
//Always use the same Input for each Graph URI and set that Graph to be the Active Graph
//Be sure to translate String.Empty back to the null URI to select the default graph
//correctly
context.InputMultiset = initialInput;
Uri currGraphUri = (uri.Equals(String.Empty)) ? null : new Uri(uri);
//This bit of logic takes care of the fact that calling SetActiveGraph((Uri)null) resets the
//Active Graph to be the default graph which if the default graph is null is usually the Union of
//all Graphs in the Store
if (currGraphUri == null && context.Data.DefaultGraph == null && context.Data.UsesUnionDefaultGraph)
{
if (context.Data.HasGraph(null))
{
context.Data.SetActiveGraph(context.Data[null]);
}
else
{
continue;
}
}
else
{
context.Data.SetActiveGraph(currGraphUri);
}
datasetOk = true;
//Evaluate for the current Active Graph
result = context.Evaluate(this._pattern);
//Merge the Results into our overall Results
if (result is NullMultiset || result is IdentityMultiset)
{
//Don't do anything
}
else
{
//If the Graph Specifier is a Variable then we must either bind the
//variable or eliminate solutions which have an incorrect value for it
if (this._graphSpecifier.TokenType == Token.VARIABLE)
{
String gvar = this._graphSpecifier.Value.Substring(1);
INode currGraph = (currGraphUri == null) ? null : new UriNode(null, currGraphUri);
foreach (int id in result.SetIDs.ToList())
{
ISet s = result[id];
if (s[gvar] == null)
{
//If Graph Variable is not yet bound for solution bind it
s.Add(gvar, currGraph);
}
else if (!s[gvar].Equals(currGraph))
{
//If Graph Variable is bound for solution and doesn't match
//current Graph then we have to remove the solution
result.Remove(id);
}
}
}
//Union solutions into the Results
finalResult.Union(result);
}
//Reset the Active Graph after each pass
context.Data.ResetActiveGraph();
datasetOk = false;
}
//Return the final result
if (finalResult.IsEmpty)
{
finalResult = new NullMultiset();
}
context.OutputMultiset = finalResult;
}
finally
{
if (datasetOk)
{
context.Data.ResetActiveGraph();
}
}
}
return(context.OutputMultiset);
}
public virtual BaseMultiset GetMultiset(IStore store)
{
var ms = new Multiset(Columns);
foreach (var row in Rows)
{
var set = new Set();
for (int i = 0; i < Columns.Count; i++)
{
if (row[i] > 0)
{
set.Add(Columns[i], MakeNode(store, row[i]));
}
}
ms.Add(set);
}
return ms;
}
/// <summary>
/// Does a Minus Join of this Multiset to another Multiset where any joinable results are subtracted from this Multiset to give the resulting Multiset
/// </summary>
/// <param name="other">Other Multiset</param>
/// <returns></returns>
public override BaseMultiset MinusJoin(BaseMultiset other)
{
//If the other Multiset is the Identity/Null Multiset then minus-ing it doesn't alter this set
if (other is IdentityMultiset) return this;
if (other is NullMultiset) return this;
//If the other Multiset is disjoint then minus-ing it also doesn't alter this set
if (this.IsDisjointWith(other)) return this;
//Find the Variables that are to be used for Joining
List<String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0) return this.Product(other);
//Start building the Joined Set
Multiset joinedSet = new Multiset();
foreach (ISet x in this.Sets)
{
//New Minus logic based on the improved Join() logic
bool minus = other.Sets.Any(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
//If no compatible sets then this set is preserved
if (!minus)
{
joinedSet.Add(x);
}
}
return joinedSet;
}
/// <summary>
/// Does a Left Join of this Multiset to another Multiset where the Join is predicated on the given Expression.
/// </summary>
/// <param name="other">Other Multiset.</param>
/// <param name="expr">Expression.</param>
/// <returns></returns>
public virtual BaseMultiset LeftJoin(BaseMultiset other, ISparqlExpression expr)
{
// If the Other is the Identity/Null Multiset the result is this Multiset
if (other is IdentityMultiset)
{
return(this);
}
if (other is NullMultiset)
{
return(this);
}
if (other.IsEmpty)
{
return(this);
}
Multiset joinedSet = new Multiset();
LeviathanLeftJoinBinder binder = new LeviathanLeftJoinBinder(joinedSet);
SparqlEvaluationContext subcontext = new SparqlEvaluationContext(binder);
// Find the First Variable from this Multiset which is in both Multisets
// If there is no Variable from this Multiset in the other Multiset then this
// should be a Join operation instead of a LeftJoin
List <String> joinVars = Variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0)
{
#if NET40
if (Options.UsePLinqEvaluation && expr.CanParallelise)
{
PartitionedMultiset partitionedSet = new PartitionedMultiset(this.Count, other.Count + 1);
this.Sets.AsParallel().ForAll(x => EvalLeftJoinProduct(x, other, partitionedSet, expr));
return(partitionedSet);
}
#endif
// Do a serial Left Join Product
// Calculate a Product filtering as we go
foreach (ISet x in Sets)
{
bool standalone = false;
bool matched = false;
foreach (ISet y in other.Sets)
{
ISet z = x.Join(y);
try
{
joinedSet.Add(z);
if (!expr.Evaluate(subcontext, z.ID).AsSafeBoolean())
{
joinedSet.Remove(z.ID);
standalone = true;
}
else
{
matched = true;
}
}
catch
{
joinedSet.Remove(z.ID);
standalone = true;
}
}
if (standalone && !matched)
{
joinedSet.Add(x.Copy());
}
}
#if NET40
#endif
}
else
{
// This is the new Join algorithm which is also correct but is O(2n) so much faster and scalable
// Downside is that it does require more memory than the old algorithm
List <MultiDictionary <INode, List <int> > > values = new List <MultiDictionary <INode, List <int> > >();
List <List <int> > nulls = new List <List <int> >();
foreach (String var in joinVars)
{
joinedSet.AddVariable(var);
values.Add(new MultiDictionary <INode, List <int> >(new FastVirtualNodeComparer()));
nulls.Add(new List <int>());
}
// First do a pass over the RHS Result to find all possible values for joined variables
foreach (ISet y in other.Sets)
{
int i = 0;
foreach (String var in joinVars)
{
INode value = y[var];
if (value != null)
{
if (values[i].TryGetValue(value, out List <int> ids))
{
ids.Add(y.ID);
}
else
{
values[i].Add(value, new List <int> {
y.ID
});
}
}
else
{
nulls[i].Add(y.ID);
}
i++;
}
}
// Then do a pass over the LHS and work out the intersections
#if NET40
if (Options.UsePLinqEvaluation && expr.CanParallelise)
{
this.Sets.AsParallel().ForAll(x => EvalLeftJoin(x, other, joinVars, values, nulls, joinedSet, subcontext, expr));
}
else
{
// Use a Serial Left Join
foreach (ISet x in this.Sets)
{
this.EvalLeftJoin(x, other, joinVars, values, nulls, joinedSet, subcontext, expr);
}
}
#else
// Use a Serial Left Join
foreach (var x in Sets)
{
EvalLeftJoin(x, other, joinVars, values, nulls, joinedSet, subcontext, expr);
}
#endif
}
return(joinedSet);
}
/// <summary>
/// Does a Left Join of this Multiset to another Multiset where the Join is predicated on the given Expression
/// </summary>
/// <param name="other">Other Multiset</param>
/// <param name="expr">Expression</param>
/// <returns></returns>
public override BaseMultiset LeftJoin(BaseMultiset other, ISparqlExpression expr)
{
//If the Other is the Identity/Null Multiset the result is this Multiset
if (other is IdentityMultiset) return this;
if (other is NullMultiset) return this;
if (other.IsEmpty) return this;
Multiset joinedSet = new Multiset();
LeviathanLeftJoinBinder binder = new LeviathanLeftJoinBinder(joinedSet);
SparqlEvaluationContext subcontext = new SparqlEvaluationContext(binder);
//Find the First Variable from this Multiset which is in both Multisets
//If there is no Variable from this Multiset in the other Multiset then this
//should be a Join operation instead of a LeftJoin
List<String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0)
{
//Calculate a Product filtering as we go
foreach (ISet x in this.Sets)
{
bool standalone = false;
foreach (ISet y in other.Sets)
{
ISet z = x.Join(y);
try
{
joinedSet.Add(z);
if (!expr.EffectiveBooleanValue(subcontext, z.ID))
{
joinedSet.Remove(z.ID);
standalone = true;
}
}
catch
{
joinedSet.Remove(z.ID);
standalone = true;
}
}
if (standalone) joinedSet.Add(x);
}
}
else
{
foreach (ISet x in this.Sets)
{
IEnumerable<ISet> ys = other.Sets.Where(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
//IEnumerable<ISet> ys = other.Sets.Where(s => s.IsCompatibleWith(x, joinVars));
bool standalone = false;
int i = 0;
foreach (ISet y in ys)
{
i++;
ISet z = x.Join(y);
try
{
joinedSet.Add(z);
if (!expr.EffectiveBooleanValue(subcontext, z.ID))
{
joinedSet.Remove(z.ID);
standalone = true;
}
}
catch
{
joinedSet.Remove(z.ID);
standalone = true;
}
}
if (standalone || i == 0) joinedSet.Add(x);
}
}
return joinedSet;
}
/// <summary>
/// Does an Exists Join of this Multiset to another Multiset where the Join is predicated on the existence/non-existence of a joinable solution on the RHS
/// </summary>
/// <param name="other">Other Multiset</param>
/// <param name="mustExist">Whether a solution must exist in the Other Multiset for the join to be made</param>
/// <returns></returns>
public override BaseMultiset ExistsJoin(BaseMultiset other, bool mustExist)
{
//For EXISTS and NOT EXISTS if the other is the Identity then it has no effect
if (other is IdentityMultiset) return this;
if (mustExist)
{
//If an EXISTS then Null/Empty Other results in Null
if (other is NullMultiset) return other;
if (other.IsEmpty) return new NullMultiset();
}
else
{
//If a NOT EXISTS then Null/Empty results in this
if (other is NullMultiset) return this;
if (other.IsEmpty) return this;
}
//Find the Variables that are to be used for Joining
List<String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0)
{
//All Disjoint Solutions are compatible
if (mustExist)
{
//If an EXISTS and disjoint then result is this
return this;
}
else
{
//If a NOT EXISTS and disjoint then result is null
return new NullMultiset();
}
}
//Start building the Joined Set
Multiset joinedSet = new Multiset();
foreach (ISet x in this.Sets)
{
//New ExistsJoin() logic based on the improved Join() logic
bool exists = other.Sets.Any(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
//bool exists = other.Sets.Any(s => s.IsCompatibleWith(x, joinVars));
if (exists)
{
//If there are compatible sets and this is an EXIST then preserve the solution
if (mustExist) joinedSet.Add(x);
}
else
{
//If there are no compatible sets and this is a NOT EXISTS then preserve the solution
if (!mustExist) joinedSet.Add(x);
}
}
return joinedSet;
}
/// <summary>
/// Joins this Multiset to another Multiset
/// </summary>
/// <param name="other">Other Multiset</param>
/// <returns></returns>
public override BaseMultiset Join(BaseMultiset other)
{
//If the Other is the Identity Multiset the result is this Multiset
if (other is IdentityMultiset) return this;
//If the Other is the Null Multiset the result is the Null Multiset
if (other is NullMultiset) return other;
//If the Other is Empty then the result is the Null Multiset
if (other.IsEmpty) return new NullMultiset();
//Find the First Variable from this Multiset which is in both Multisets
//If there is no Variable from this Multiset in the other Multiset then this
//should be a Join operation instead of a LeftJoin
List<String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0) return this.Product(other);
//Start building the Joined Set
Multiset joinedSet = new Multiset();
foreach (ISet x in this.Sets)
{
//For sets to be compatible for every joinable variable they must either have a null for the
//variable in one of the sets or if they have values the values must be equal
////This first check is to try speed things up, it looks whether there are solutions that may match
////without needing to do a full table scan of the RHS results as the subsequent LINQ call will do
////if (!joinVars.All(v => x[v] == null || other.ContainsValue(v, x[v]) || other.ContainsValue(v, null))) continue;
IEnumerable<ISet> ys = other.Sets.Where(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
//IEnumerable<ISet> ys = other.Sets.Where(s => s.IsCompatibleWith(x, joinVars));
foreach (ISet y in ys)
{
joinedSet.Add(x.Join(y));
}
}
return joinedSet;
}
/// <summary>
/// Does an Exists Join of this Multiset to another Multiset where the Join is predicated on the existence/non-existence of a joinable solution on the RHS
/// </summary>
/// <param name="other">Other Multiset</param>
/// <param name="mustExist">Whether a solution must exist in the Other Multiset for the join to be made</param>
/// <returns></returns>
public override BaseMultiset ExistsJoin(BaseMultiset other, bool mustExist)
{
//For EXISTS and NOT EXISTS if the other is the Identity then it has no effect
if (other is IdentityMultiset)
{
return(this);
}
if (mustExist)
{
//If an EXISTS then Null/Empty Other results in Null
if (other is NullMultiset)
{
return(other);
}
if (other.IsEmpty)
{
return(new NullMultiset());
}
}
else
{
//If a NOT EXISTS then Null/Empty results in this
if (other is NullMultiset)
{
return(this);
}
if (other.IsEmpty)
{
return(this);
}
}
//Find the Variables that are to be used for Joining
List <String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0)
{
//All Disjoint Solutions are compatible
if (mustExist)
{
//If an EXISTS and disjoint then result is this
return(this);
}
else
{
//If a NOT EXISTS and disjoint then result is null
return(new NullMultiset());
}
}
//Start building the Joined Set
Multiset joinedSet = new Multiset();
//This is the old algorithm which is correct but naive with worse case O(n^2)
//foreach (ISet x in this.Sets)
//{
// //New ExistsJoin() logic based on the improved Join() logic
// bool exists = other.Sets.Any(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
// //bool exists = other.Sets.Any(s => s.IsCompatibleWith(x, joinVars));
// if (exists)
// {
// //If there are compatible sets and this is an EXIST then preserve the solution
// if (mustExist) joinedSet.Add(x);
// }
// else
// {
// //If there are no compatible sets and this is a NOT EXISTS then preserve the solution
// if (!mustExist) joinedSet.Add(x);
// }
//}
//This is the new algorithm which is also correct but is O(3n) so much faster and scalable
//Downside is that it does require more memory than the old algorithm
List <HashTable <INode, int> > values = new List <HashTable <INode, int> >();
List <List <int> > nulls = new List <List <int> >();
foreach (String var in joinVars)
{
values.Add(new HashTable <INode, int>(HashTableBias.Enumeration));
nulls.Add(new List <int>());
}
//First do a pass over the LHS Result to find all possible values for joined variables
foreach (ISet x in this.Sets)
{
int i = 0;
foreach (String var in joinVars)
{
INode value = x[var];
if (value != null)
{
values[i].Add(value, x.ID);
}
else
{
nulls[i].Add(x.ID);
}
i++;
}
}
//Then do a pass over the RHS and work out the intersections
HashSet <int> exists = new HashSet <int>();
foreach (ISet y in other.Sets)
{
IEnumerable <int> possMatches = null;
int i = 0;
foreach (String var in joinVars)
{
INode value = y[var];
if (value != null)
{
if (values[i].ContainsKey(value))
{
possMatches = (possMatches == null ? values[i].GetValues(value).Concat(nulls[i]) : possMatches.Intersect(values[i].GetValues(value).Concat(nulls[i])));
}
else
{
possMatches = Enumerable.Empty <int>();
break;
}
}
else
{
//Don't forget that a null will be potentially compatible with everything
possMatches = (possMatches == null ? this.SetIDs : possMatches.Intersect(this.SetIDs));
}
i++;
}
if (possMatches == null)
{
continue;
}
//Look at possible matches, if is a valid match then mark the set as having an existing match
//Don't reconsider sets which have already been marked as having an existing match
foreach (int poss in possMatches)
{
if (exists.Contains(poss))
{
continue;
}
if (this._sets[poss].IsCompatibleWith(y, joinVars))
{
exists.Add(poss);
}
}
}
//Apply the actual exists
if (exists.Count == this.Count)
{
//If number of sets that have a match is equal to number of sets then we're either returning everything or nothing
if (mustExist)
{
return(this);
}
else
{
return(new NullMultiset());
}
}
else
{
//Otherwise iterate
foreach (ISet x in this.Sets)
{
if (mustExist)
{
if (exists.Contains(x.ID))
{
joinedSet.Add(x.Copy());
}
}
else
{
if (!exists.Contains(x.ID))
{
joinedSet.Add(x.Copy());
}
}
}
}
return(joinedSet);
}
/// <summary>
/// Processes an INSERT/DELETE command
/// </summary>
/// <param name="cmd">Insert/Delete Command</param>
public void ProcessModifyCommand(ModifyCommand cmd)
{
if (this._manager is IUpdateableGenericIOManager)
{
((IUpdateableGenericIOManager)this._manager).Update(cmd.ToString());
}
else
{
if (this._manager is IQueryableGenericIOManager)
{
//First build and make the query to get a Result Set
String queryText = "SELECT * WHERE " + cmd.WherePattern.ToString();
SparqlQueryParser parser = new SparqlQueryParser();
SparqlQuery query = parser.ParseFromString(queryText);
if (cmd.GraphUri != null && !cmd.UsingUris.Any()) query.AddDefaultGraph(cmd.GraphUri);
foreach (Uri u in cmd.UsingUris)
{
query.AddDefaultGraph(u);
}
foreach (Uri u in cmd.UsingNamedUris)
{
query.AddNamedGraph(u);
}
Object results = ((IQueryableGenericIOManager)this._manager).Query(query.ToString());
if (results is SparqlResultSet)
{
//Now need to transform the Result Set back to a Multiset
Multiset mset = new Multiset((SparqlResultSet)results);
//Generate the Triples for each Solution
List<Triple> deletedTriples = new List<Triple>();
Dictionary<String, List<Triple>> deletedGraphTriples = new Dictionary<string, List<Triple>>();
foreach (Set s in mset.Sets)
{
List<Triple> tempDeletedTriples = new List<Triple>();
try
{
ConstructContext context = new ConstructContext(null, s, true);
foreach (IConstructTriplePattern p in cmd.DeletePattern.TriplePatterns.OfType<IConstructTriplePattern>())
{
try
{
tempDeletedTriples.Add(p.Construct(context));
}
catch (RdfQueryException)
{
//If we get an error here then it means we could not construct a specific
//triple so we continue anyway
}
}
deletedTriples.AddRange(tempDeletedTriples);
}
catch (RdfQueryException)
{
//If we get an error here this means we couldn't construct for this solution so the
//solution is ignored for this graph
}
//Triples from GRAPH clauses
foreach (GraphPattern gp in cmd.DeletePattern.ChildGraphPatterns)
{
tempDeletedTriples.Clear();
try
{
String graphUri;
switch (gp.GraphSpecifier.TokenType)
{
case Token.URI:
graphUri = gp.GraphSpecifier.Value;
break;
case Token.VARIABLE:
if (s.ContainsVariable(gp.GraphSpecifier.Value))
{
INode temp = s[gp.GraphSpecifier.Value.Substring(1)];
if (temp == null)
{
//If the Variable is not bound then skip
continue;
}
else if (temp.NodeType == NodeType.Uri)
{
graphUri = temp.ToSafeString();
}
else
{
//If the Variable is not bound to a URI then skip
continue;
}
}
else
{
//If the Variable is not bound for this solution then skip
continue;
}
break;
default:
//Any other Graph Specifier we have to ignore this solution
continue;
}
if (!deletedGraphTriples.ContainsKey(graphUri)) deletedGraphTriples.Add(graphUri, new List<Triple>());
ConstructContext context = new ConstructContext(null, s, true);
foreach (IConstructTriplePattern p in gp.TriplePatterns.OfType<IConstructTriplePattern>())
{
try
{
tempDeletedTriples.Add(p.Construct(context));
}
catch (RdfQueryException)
{
//If we throw an error this means we couldn't construct a specific
//triple so we continue anyway
}
}
deletedGraphTriples[graphUri].AddRange(tempDeletedTriples);
}
catch (RdfQueryException)
{
//If we get an error here this means we couldn't construct for this solution so the
//solution is ignored for this graph
}
}
}
//Generate the Triples for each Solution
List<Triple> insertedTriples = new List<Triple>();
Dictionary<String, List<Triple>> insertedGraphTriples = new Dictionary<string, List<Triple>>();
foreach (Set s in mset.Sets)
{
List<Triple> tempInsertedTriples = new List<Triple>();
try
{
ConstructContext context = new ConstructContext(null, s, true);
foreach (IConstructTriplePattern p in cmd.InsertPattern.TriplePatterns.OfType<IConstructTriplePattern>())
{
try
{
tempInsertedTriples.Add(p.Construct(context));
}
catch (RdfQueryException)
{
//If we get an error here then it means we couldn't construct a specific
//triple so we continue anyway
}
}
insertedTriples.AddRange(tempInsertedTriples);
}
catch (RdfQueryException)
{
//If we get an error here this means we couldn't construct for this solution so the
//solution is ignored for this graph
}
//Triples from GRAPH clauses
foreach (GraphPattern gp in cmd.InsertPattern.ChildGraphPatterns)
{
tempInsertedTriples.Clear();
try
{
String graphUri;
switch (gp.GraphSpecifier.TokenType)
{
case Token.URI:
graphUri = gp.GraphSpecifier.Value;
break;
case Token.VARIABLE:
if (s.ContainsVariable(gp.GraphSpecifier.Value))
{
INode temp = s[gp.GraphSpecifier.Value.Substring(1)];
if (temp == null)
{
//If the Variable is not bound then skip
continue;
}
else if (temp.NodeType == NodeType.Uri)
{
graphUri = temp.ToSafeString();
}
else
{
//If the Variable is not bound to a URI then skip
continue;
}
}
else
{
//If the Variable is not bound for this solution then skip
continue;
}
break;
default:
//Any other Graph Specifier we have to ignore this solution
continue;
}
if (!insertedGraphTriples.ContainsKey(graphUri)) insertedGraphTriples.Add(graphUri, new List<Triple>());
ConstructContext context = new ConstructContext(null, s, true);
foreach (IConstructTriplePattern p in gp.TriplePatterns.OfType<IConstructTriplePattern>())
{
try
{
tempInsertedTriples.Add(p.Construct(context));
}
catch (RdfQueryException)
{
//If we get an error here it means we couldn't construct a specific
//triple so we continue anyway
}
}
insertedGraphTriples[graphUri].AddRange(tempInsertedTriples);
}
catch (RdfQueryException)
{
//If we get an error here this means we couldn't construct for this solution so the
//solution is ignored for this graph
}
}
}
//Now decide how to apply the update
if (this._manager.UpdateSupported)
{
this._manager.UpdateGraph(cmd.GraphUri, insertedTriples, deletedTriples);
//We do these two operations sequentially even if in some cases they could be combined to ensure that the underlying
//Manager doesn't do any optimisations which would have the result of our updates not being properly applied
//e.g. ignoring Triples which are both asserted and retracted in one update
foreach (KeyValuePair<String, List<Triple>> graphDeletion in deletedGraphTriples)
{
this._manager.UpdateGraph(graphDeletion.Key, Enumerable.Empty<Triple>(), graphDeletion.Value);
}
foreach (KeyValuePair<String, List<Triple>> graphInsertion in insertedGraphTriples)
{
this._manager.UpdateGraph(graphInsertion.Key, graphInsertion.Value, Enumerable.Empty<Triple>());
}
}
else
{
Graph g = new Graph();
this._manager.LoadGraph(g, cmd.GraphUri);
g.Retract(deletedTriples);
this._manager.SaveGraph(g);
foreach (String graphUri in deletedGraphTriples.Keys.Concat(insertedGraphTriples.Keys).Distinct())
{
g = new Graph();
this._manager.LoadGraph(g, graphUri);
if (deletedGraphTriples.ContainsKey(graphUri)) g.Retract(deletedGraphTriples[graphUri]);
if (insertedGraphTriples.ContainsKey(graphUri)) g.Assert(insertedGraphTriples[graphUri]);
this._manager.SaveGraph(g);
}
}
}
else
{
throw new SparqlUpdateException("Cannot evaluate an INSERT/DELETE Command as the underlying Store failed to answer the query for the WHERE portion of the command as expected");
}
}
else
{
throw new NotSupportedException("INSERT/DELETE commands are not supported by this Update Processor as the manager for the underlying Store does not provide Query capabilities which are necessary to process this command");
}
}
}
/// <summary>
/// Does a Minus Join of this Multiset to another Multiset where any joinable results are subtracted from this Multiset to give the resulting Multiset
/// </summary>
/// <param name="other">Other Multiset</param>
/// <returns></returns>
public override BaseMultiset MinusJoin(BaseMultiset other)
{
//If the other Multiset is the Identity/Null Multiset then minus-ing it doesn't alter this set
if (other is IdentityMultiset)
{
return(this);
}
if (other is NullMultiset)
{
return(this);
}
//If the other Multiset is disjoint then minus-ing it also doesn't alter this set
if (this.IsDisjointWith(other))
{
return(this);
}
//Find the Variables that are to be used for Joining
List <String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0)
{
return(this.Product(other));
}
//Start building the Joined Set
Multiset joinedSet = new Multiset();
//This is the old algorithm which is correct but naive and has O(n^2) complexity
//foreach (ISet x in this.Sets)
//{
// //New Minus logic based on the improved Join() logic
// bool minus = other.Sets.Any(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
// //If no compatible sets then this set is preserved
// if (!minus)
// {
// joinedSet.Add(x);
// }
//}
//This is the new algorithm which is also correct but is O(3n) so much faster and scalable
//Downside is that it does require more memory than the old algorithm
List <HashTable <INode, int> > values = new List <HashTable <INode, int> >();
List <List <int> > nulls = new List <List <int> >();
foreach (String var in joinVars)
{
values.Add(new HashTable <INode, int>(HashTableBias.Enumeration));
nulls.Add(new List <int>());
}
//First do a pass over the LHS Result to find all possible values for joined variables
foreach (ISet x in this.Sets)
{
int i = 0;
foreach (String var in joinVars)
{
INode value = x[var];
if (value != null)
{
values[i].Add(value, x.ID);
}
else
{
nulls[i].Add(x.ID);
}
i++;
}
}
//Then do a pass over the RHS and work out the intersections
HashSet <int> toMinus = new HashSet <int>();
foreach (ISet y in other.Sets)
{
IEnumerable <int> possMatches = null;
int i = 0;
foreach (String var in joinVars)
{
INode value = y[var];
if (value != null)
{
if (values[i].ContainsKey(value))
{
possMatches = (possMatches == null ? values[i].GetValues(value).Concat(nulls[i]) : possMatches.Intersect(values[i].GetValues(value).Concat(nulls[i])));
}
else
{
possMatches = Enumerable.Empty <int>();
break;
}
}
else
{
//Don't forget that a null will be potentially compatible with everything
possMatches = (possMatches == null ? this.SetIDs : possMatches.Intersect(this.SetIDs));
}
i++;
}
if (possMatches == null)
{
continue;
}
//Look at possible matches, if is a valid match then mark the matched set for minus'ing
//Don't reconsider sets which have already been marked for minusing
foreach (int poss in possMatches)
{
if (toMinus.Contains(poss))
{
continue;
}
if (this._sets[poss].IsCompatibleWith(y, joinVars))
{
toMinus.Add(poss);
}
}
}
//Apply the actual minus
if (toMinus.Count == this.Count)
{
//If number of sets to minus is equal to number of sets then we're minusing everything
return(new NullMultiset());
}
else
{
//Otherwise iterate
foreach (ISet x in this.Sets)
{
if (!toMinus.Contains(x.ID))
{
joinedSet.Add(x.Copy());
}
}
}
return(joinedSet);
}
/// <summary>
/// Does an Exists Join of this Multiset to another Multiset where the Join is predicated on the existence/non-existence of a joinable solution on the RHS.
/// </summary>
/// <param name="other">Other Multiset.</param>
/// <param name="mustExist">Whether a solution must exist in the Other Multiset for the join to be made.</param>
/// <returns></returns>
public virtual BaseMultiset ExistsJoin(BaseMultiset other, bool mustExist)
{
// For EXISTS and NOT EXISTS if the other is the Identity then it has no effect
if (other is IdentityMultiset)
{
return(this);
}
if (mustExist)
{
// If an EXISTS then Null/Empty Other results in Null
if (other is NullMultiset)
{
return(other);
}
if (other.IsEmpty)
{
return(new NullMultiset());
}
}
else
{
// If a NOT EXISTS then Null/Empty results in this
if (other is NullMultiset)
{
return(this);
}
if (other.IsEmpty)
{
return(this);
}
}
// Find the Variables that are to be used for Joining
List <String> joinVars = Variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0)
{
// All Disjoint Solutions are compatible
if (mustExist)
{
// If an EXISTS and disjoint then result is this
return(this);
}
else
{
// If a NOT EXISTS and disjoint then result is null
return(new NullMultiset());
}
}
// Start building the Joined Set
Multiset joinedSet = new Multiset();
// This is the new algorithm which is also correct but is O(3n) so much faster and scalable
// Downside is that it does require more memory than the old algorithm
List <MultiDictionary <INode, List <int> > > values = new List <MultiDictionary <INode, List <int> > >();
List <List <int> > nulls = new List <List <int> >();
foreach (String var in joinVars)
{
joinedSet.AddVariable(var);
values.Add(new MultiDictionary <INode, List <int> >(new FastVirtualNodeComparer()));
nulls.Add(new List <int>());
}
// First do a pass over the LHS Result to find all possible values for joined variables
foreach (ISet x in Sets)
{
int i = 0;
foreach (String var in joinVars)
{
INode value = x[var];
if (value != null)
{
if (values[i].TryGetValue(value, out List <int> ids))
{
ids.Add(x.ID);
}
else
{
values[i].Add(value, new List <int> {
x.ID
});
}
}
else
{
nulls[i].Add(x.ID);
}
i++;
}
}
// Then do a pass over the RHS and work out the intersections
HashSet <int> exists = new HashSet <int>();
foreach (ISet y in other.Sets)
{
IEnumerable <int> possMatches = null;
int i = 0;
foreach (String var in joinVars)
{
INode value = y[var];
if (value != null)
{
if (values[i].ContainsKey(value))
{
possMatches = (possMatches == null ? values[i][value].Concat(nulls[i]) : possMatches.Intersect(values[i][value].Concat(nulls[i])));
}
else
{
possMatches = Enumerable.Empty <int>();
break;
}
}
else
{
// Don't forget that a null will be potentially compatible with everything
possMatches = (possMatches == null ? SetIDs : possMatches.Intersect(SetIDs));
}
i++;
}
if (possMatches == null)
{
continue;
}
// Look at possible matches, if is a valid match then mark the set as having an existing match
// Don't reconsider sets which have already been marked as having an existing match
foreach (int poss in possMatches)
{
if (exists.Contains(poss))
{
continue;
}
if (this[poss].IsCompatibleWith(y, joinVars))
{
exists.Add(poss);
}
}
}
// Apply the actual exists
if (exists.Count == Count)
{
// If number of sets that have a match is equal to number of sets then we're either returning everything or nothing
if (mustExist)
{
return(this);
}
else
{
return(new NullMultiset());
}
}
else
{
// Otherwise iterate
foreach (ISet x in Sets)
{
if (mustExist)
{
if (exists.Contains(x.ID))
{
joinedSet.Add(x.Copy());
}
}
else
{
if (!exists.Contains(x.ID))
{
joinedSet.Add(x.Copy());
}
}
}
}
return(joinedSet);
}
/// <summary>
/// Joins this Multiset to another Multiset
/// </summary>
/// <param name="other">Other Multiset</param>
/// <returns></returns>
public override BaseMultiset Join(BaseMultiset other)
{
//If the Other is the Identity Multiset the result is this Multiset
if (other is IdentityMultiset)
{
return(this);
}
//If the Other is the Null Multiset the result is the Null Multiset
if (other is NullMultiset)
{
return(other);
}
//If the Other is Empty then the result is the Null Multiset
if (other.IsEmpty)
{
return(new NullMultiset());
}
//Find the First Variable from this Multiset which is in both Multisets
//If there is no Variable from this Multiset in the other Multiset then this
//should be a Join operation instead of a LeftJoin
List <String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0)
{
return(this.Product(other));
}
//Start building the Joined Set
Multiset joinedSet = new Multiset();
//This is the old Join algorithm which while correct is O(n^2) so scales terribly
//foreach (ISet x in this.Sets)
//{
// //For sets to be compatible for every joinable variable they must either have a null for the
// //variable in one of the sets or if they have values the values must be equal
// ////This first check is to try speed things up, it looks whether there are solutions that may match
// ////without needing to do a full table scan of the RHS results as the subsequent LINQ call will do
// ////if (!joinVars.All(v => x[v] == null || other.ContainsValue(v, x[v]) || other.ContainsValue(v, null))) continue;
// IEnumerable<ISet> ys = other.Sets.Where(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
// //IEnumerable<ISet> ys = other.Sets.Where(s => s.IsCompatibleWith(x, joinVars));
// foreach (ISet y in ys)
// {
// joinedSet.Add(x.Join(y));
// }
//}
//This is the new Join algorithm which is also correct but is O(2n) so much faster and scalable
//Downside is that it does require more memory than the old algorithm
List <HashTable <INode, int> > values = new List <HashTable <INode, int> >();
List <List <int> > nulls = new List <List <int> >();
foreach (String var in joinVars)
{
values.Add(new HashTable <INode, int>(HashTableBias.Enumeration));
nulls.Add(new List <int>());
}
//First do a pass over the LHS Result to find all possible values for joined variables
foreach (ISet x in this.Sets)
{
int i = 0;
foreach (String var in joinVars)
{
INode value = x[var];
if (value != null)
{
values[i].Add(value, x.ID);
}
else
{
nulls[i].Add(x.ID);
}
i++;
}
}
#if NET40 && !SILVERLIGHT
if (Options.UsePLinqEvaluation)
{
//Use a paralllel join
other.Sets.AsParallel().ForAll(y => EvalJoin(y, joinVars, values, nulls, joinedSet));
}
else
{
#endif
//Use a serial join
//Then do a pass over the RHS and work out the intersections
foreach (ISet y in other.Sets)
{
this.EvalJoin(y, joinVars, values, nulls, joinedSet);
}
#if NET40 && !SILVERLIGHT
}
#endif
return(joinedSet);
}
/// <summary>
/// Does a Minus Join of this Multiset to another Multiset where any joinable results are subtracted from this Multiset to give the resulting Multiset.
/// </summary>
/// <param name="other">Other Multiset.</param>
/// <returns></returns>
public virtual BaseMultiset MinusJoin(BaseMultiset other)
{
// If the other Multiset is the Identity/Null Multiset then minus-ing it doesn't alter this set
if (other is IdentityMultiset)
{
return(this);
}
if (other is NullMultiset)
{
return(this);
}
// If the other Multiset is disjoint then minus-ing it also doesn't alter this set
if (IsDisjointWith(other))
{
return(this);
}
// Find the Variables that are to be used for Joining
List <String> joinVars = Variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0)
{
return(Product(other));
}
// Start building the Joined Set
Multiset joinedSet = new Multiset();
// This is the new algorithm which is also correct but is O(3n) so much faster and scalable
// Downside is that it does require more memory than the old algorithm
List <MultiDictionary <INode, List <int> > > values = new List <MultiDictionary <INode, List <int> > >();
List <List <int> > nulls = new List <List <int> >();
foreach (String var in joinVars)
{
values.Add(new MultiDictionary <INode, List <int> >(new FastVirtualNodeComparer()));
nulls.Add(new List <int>());
}
// First do a pass over the LHS Result to find all possible values for joined variables
foreach (ISet x in Sets)
{
int i = 0;
foreach (String var in joinVars)
{
INode value = x[var];
if (value != null)
{
if (values[i].TryGetValue(value, out List <int> ids))
{
ids.Add(x.ID);
}
else
{
values[i].Add(value, new List <int> {
x.ID
});
}
}
else
{
nulls[i].Add(x.ID);
}
i++;
}
}
// Then do a pass over the RHS and work out the intersections
HashSet <int> toMinus = new HashSet <int>();
foreach (ISet y in other.Sets)
{
IEnumerable <int> possMatches = null;
int i = 0;
foreach (String var in joinVars)
{
INode value = y[var];
if (value != null)
{
if (values[i].ContainsKey(value))
{
possMatches = (possMatches == null ? values[i][value].Concat(nulls[i]) : possMatches.Intersect(values[i][value].Concat(nulls[i])));
}
else
{
possMatches = Enumerable.Empty <int>();
break;
}
}
else
{
// Don't forget that a null will be potentially compatible with everything
possMatches = (possMatches == null ? SetIDs : possMatches.Intersect(SetIDs));
}
i++;
}
if (possMatches == null)
{
continue;
}
// Look at possible matches, if is a valid match then mark the matched set for minus'ing
// Don't reconsider sets which have already been marked for minusing
foreach (int poss in possMatches)
{
if (toMinus.Contains(poss))
{
continue;
}
if (this[poss].IsMinusCompatibleWith(y, joinVars))
{
toMinus.Add(poss);
}
}
}
// Apply the actual minus
if (toMinus.Count == Count)
{
// If number of sets to minus is equal to number of sets then we're minusing everything
return(new NullMultiset());
}
else
{
// Otherwise iterate
foreach (ISet x in Sets)
{
if (!toMinus.Contains(x.ID))
{
joinedSet.Add(x.Copy());
}
}
}
return(joinedSet);
}
/// <summary>
/// Evaluates the filtered product
/// </summary>
/// <param name="context">Evaluation Context</param>
/// <returns></returns>
public BaseMultiset Evaluate(SparqlEvaluationContext context)
{
BaseMultiset initialInput = context.InputMultiset;
BaseMultiset lhsResults = context.Evaluate(this._lhs);
if (lhsResults is NullMultiset || lhsResults.IsEmpty)
{
//If LHS Results are Null/Empty then end result will always be null so short circuit
context.OutputMultiset = new NullMultiset();
}
else
{
context.InputMultiset = initialInput;
BaseMultiset rhsResults = context.Evaluate(this._rhs);
if (rhsResults is NullMultiset || rhsResults.IsEmpty)
{
//If RHS Results are Null/Empty then end results will always be null so short circuit
context.OutputMultiset = new NullMultiset();
}
else if (rhsResults is IdentityMultiset)
{
//Apply Filter over LHS Results only - defer evaluation to filter implementation
context.InputMultiset = lhsResults;
UnaryExpressionFilter filter = new UnaryExpressionFilter(this._expr);
filter.Evaluate(context);
context.OutputMultiset = lhsResults;
}
else
{
//Calculate the product applying the filter as we go
#if NET40 && !SILVERLIGHT
if (Options.UsePLinqEvaluation && this._expr.CanParallelise)
{
PartitionedMultiset partitionedSet;
SparqlResultBinder binder = context.Binder;
if (lhsResults.Count >= rhsResults.Count)
{
partitionedSet = new PartitionedMultiset(lhsResults.Count, rhsResults.Count);
context.Binder = new LeviathanLeftJoinBinder(partitionedSet);
lhsResults.Sets.AsParallel().ForAll(x => this.EvalFilteredProduct(context, x, rhsResults, partitionedSet));
}
else
{
partitionedSet = new PartitionedMultiset(rhsResults.Count, lhsResults.Count);
context.Binder = new LeviathanLeftJoinBinder(partitionedSet);
rhsResults.Sets.AsParallel().ForAll(y => this.EvalFilteredProduct(context, y, lhsResults, partitionedSet));
}
context.Binder = binder;
context.OutputMultiset = partitionedSet;
}
else
{
#endif
BaseMultiset productSet = new Multiset();
SparqlResultBinder binder = context.Binder;
context.Binder = new LeviathanLeftJoinBinder(productSet);
foreach (ISet x in lhsResults.Sets)
{
foreach (ISet y in rhsResults.Sets)
{
ISet z = x.Join(y);
productSet.Add(z);
try
{
if (!this._expr.Evaluate(context, z.ID).AsSafeBoolean())
{
//Means the expression evaluates to false so we discard the solution
productSet.Remove(z.ID);
}
}
catch
{
//Means this solution does not meet the FILTER and can be discarded
productSet.Remove(z.ID);
}
}
//Remember to check for timeouts occassionaly
context.CheckTimeout();
}
context.Binder = binder;
context.OutputMultiset = productSet;
#if NET40 && !SILVERLIGHT
}
#endif
}
}
return(context.OutputMultiset);
}
/// <summary>
/// Joins this Multiset to another Multiset.
/// </summary>
/// <param name="other">Other Multiset.</param>
/// <returns></returns>
public virtual BaseMultiset Join(BaseMultiset other)
{
// If the Other is the Identity Multiset the result is this Multiset
if (other is IdentityMultiset)
{
return(this);
}
// If the Other is the Null Multiset the result is the Null Multiset
if (other is NullMultiset)
{
return(other);
}
// If the Other is Empty then the result is the Null Multiset
if (other.IsEmpty)
{
return(new NullMultiset());
}
// Find the First Variable from this Multiset which is in both Multisets
// If there is no Variable from this Multiset in the other Multiset then this
// should be a Product operation instead of a Join
List <String> joinVars = Variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0)
{
return(Product(other));
}
// Start building the Joined Set
Multiset joinedSet = new Multiset();
// This is the new Join algorithm which is O(2n) so much faster and scalable
// Downside is that it does require more memory than the old algorithm
List <MultiDictionary <INode, List <int> > > values = new List <MultiDictionary <INode, List <int> > >();
List <List <int> > nulls = new List <List <int> >();
foreach (String var in joinVars)
{
joinedSet.AddVariable(var);
values.Add(new MultiDictionary <INode, List <int> >(new FastVirtualNodeComparer()));
nulls.Add(new List <int>());
}
// First do a pass over the LHS Result to find all possible values for joined variables
foreach (ISet x in Sets)
{
var i = 0;
foreach (var var in joinVars)
{
var value = x[var];
if (value != null)
{
if (values[i].TryGetValue(value, out List <int> ids))
{
ids.Add(x.ID);
}
else
{
values[i].Add(value, new List <int> {
x.ID
});
}
}
else
{
nulls[i].Add(x.ID);
}
i++;
}
}
#if NET40
if (Options.UsePLinqEvaluation)
{
// Use a paralllel join
other.Sets.AsParallel().ForAll(y => EvalJoin(y, joinVars, values, nulls, joinedSet));
}
else
{
// Use a serial join
// Then do a pass over the RHS and work out the intersections
foreach (ISet y in other.Sets)
{
this.EvalJoin(y, joinVars, values, nulls, joinedSet);
}
}
#else
// Use a serial join
// Then do a pass over the RHS and work out the intersections
foreach (ISet y in other.Sets)
{
EvalJoin(y, joinVars, values, nulls, joinedSet);
}
#endif
return(joinedSet);
}
/// <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>
/// Evaluates the Graph Clause by setting up the dataset, applying the pattern and then generating additional bindings if necessary
/// </summary>
/// <param name="context">Evaluation Context</param>
/// <returns></returns>
public BaseMultiset Evaluate(SparqlEvaluationContext context)
{
// Q: Can we optimise GRAPH when the input is the Null Multiset to just return the Null Multiset?
bool datasetOk = false;
try
{
List <String> activeGraphs = new List <string>();
// Get the URIs of Graphs that should be evaluated over
if (_graphSpecifier.TokenType != Token.VARIABLE)
{
switch (_graphSpecifier.TokenType)
{
case Token.URI:
case Token.QNAME:
Uri activeGraphUri = UriFactory.Create(Tools.ResolveUriOrQName(_graphSpecifier, context.Query.NamespaceMap, context.Query.BaseUri));
if (context.Data.HasGraph(activeGraphUri))
{
// If the Graph is explicitly specified and there are FROM/FROM NAMED present then the Graph
// URI must be in the graphs specified by a FROM/FROM NAMED or the result is null
if (context.Query == null ||
((!context.Query.DefaultGraphs.Any() && !context.Query.NamedGraphs.Any()) ||
context.Query.NamedGraphs.Any(u => EqualityHelper.AreUrisEqual(activeGraphUri, u)))
)
{
// Either there was no Query
// OR there were no Default/Named Graphs (hence any Graph URI is permitted)
// OR the specified URI was a Named Graph URI
// In any case we can go ahead and set the active Graph
activeGraphs.Add(activeGraphUri.AbsoluteUri);
}
else
{
// The specified URI was not present in the Named Graphs so return null
context.OutputMultiset = new NullMultiset();
return(context.OutputMultiset);
}
}
else
{
// If specifies a specific Graph and not in the Dataset result is a null multiset
context.OutputMultiset = new NullMultiset();
return(context.OutputMultiset);
}
break;
default:
throw new RdfQueryException("Cannot use a '" + _graphSpecifier.GetType().ToString() + "' Token to specify the Graph for a GRAPH clause");
}
}
else
{
String gvar = _graphSpecifier.Value.Substring(1);
// Watch out for the case in which the Graph Variable is not bound for all Sets in which case
// we still need to operate over all Graphs
if (context.InputMultiset.ContainsVariable(gvar) && context.InputMultiset.Sets.All(s => s[gvar] != null))
{
// If there are already values bound to the Graph variable for all Input Solutions then we limit the Query to those Graphs
List <Uri> graphUris = new List <Uri>();
foreach (ISet s in context.InputMultiset.Sets)
{
INode temp = s[gvar];
if (temp == null)
{
continue;
}
if (temp.NodeType != NodeType.Uri)
{
continue;
}
activeGraphs.Add(temp.ToString());
graphUris.Add(((IUriNode)temp).Uri);
}
}
else
{
// Nothing yet bound to the Graph Variable so the Query is over all the named Graphs
if (context.Query != null && context.Query.NamedGraphs.Any())
{
// Query specifies one/more named Graphs
activeGraphs.AddRange(context.Query.NamedGraphs.Select(u => u.AbsoluteUri));
}
else if (context.Query != null && context.Query.DefaultGraphs.Any() && !context.Query.NamedGraphs.Any())
{
// Gives null since the query dataset does not include any named graphs
context.OutputMultiset = new NullMultiset();
return(context.OutputMultiset);
}
else
{
// Query is over entire dataset/default Graph since no named Graphs are explicitly specified
activeGraphs.AddRange(context.Data.GraphUris.Select(u => u.ToSafeString()));
}
}
}
// Remove all duplicates from Active Graphs to avoid duplicate results
activeGraphs = activeGraphs.Distinct().ToList();
// Evaluate the inner pattern
BaseMultiset initialInput = context.InputMultiset;
BaseMultiset finalResult = new Multiset();
// Evalute for each Graph URI and union the results
foreach (String uri in activeGraphs)
{
// Always use the same Input for each Graph URI and set that Graph to be the Active Graph
// Be sure to translate String.Empty back to the null URI to select the default graph
// correctly
context.InputMultiset = initialInput;
Uri currGraphUri = (uri.Equals(String.Empty)) ? null : UriFactory.Create(uri);
// Set Active Graph
if (currGraphUri == null)
{
// GRAPH operates over named graphs only so default graph gets skipped
continue;
}
// The result of the HasGraph() call is ignored we just make it so datasets with any kind of
// load on demand behaviour work properly
context.Data.HasGraph(currGraphUri);
// All we actually care about is setting the active graph
context.Data.SetActiveGraph(currGraphUri);
datasetOk = true;
// Evaluate for the current Active Graph
BaseMultiset result = context.Evaluate(_pattern);
// Merge the Results into our overall Results
if (result is NullMultiset)
{
// Don't do anything, adds nothing to the results
}
else if (result is IdentityMultiset)
{
// Adds a single row to the results
if (_graphSpecifier.TokenType == Token.VARIABLE)
{
// Include graph variable if not yet bound
INode currGraph = new UriNode(null, currGraphUri);
Set s = new Set();
s.Add(_graphSpecifier.Value.Substring(1), currGraph);
finalResult.Add(s);
}
else
{
finalResult.Add(new Set());
}
}
else
{
// If the Graph Specifier is a Variable then we must either bind the
// variable or eliminate solutions which have an incorrect value for it
if (_graphSpecifier.TokenType == Token.VARIABLE)
{
String gvar = _graphSpecifier.Value.Substring(1);
INode currGraph = new UriNode(null, currGraphUri);
foreach (int id in result.SetIDs.ToList())
{
ISet s = result[id];
if (s[gvar] == null)
{
// If Graph Variable is not yet bound for solution bind it
s.Add(gvar, currGraph);
}
else if (!s[gvar].Equals(currGraph))
{
// If Graph Variable is bound for solution and doesn't match
// current Graph then we have to remove the solution
result.Remove(id);
}
}
}
// Union solutions into the Results
finalResult.Union(result);
}
// Reset the Active Graph after each pass
context.Data.ResetActiveGraph();
datasetOk = false;
}
// Return the final result
if (finalResult.IsEmpty)
{
finalResult = new NullMultiset();
}
context.OutputMultiset = finalResult;
}
finally
{
if (datasetOk)
{
context.Data.ResetActiveGraph();
}
}
return(context.OutputMultiset);
}
private BaseMultiset StreamingEvaluate(SparqlEvaluationContext context, int pattern, out bool halt)
{
halt = false;
//Handle Empty BGPs
if (pattern == 0 && this._triplePatterns.Count == 0)
{
context.OutputMultiset = new IdentityMultiset();
return context.OutputMultiset;
}
BaseMultiset initialInput, localOutput, results;
//Set up the Input and Output Multiset appropriately
switch (pattern)
{
case 0:
//Input is as given and Output is new empty multiset
initialInput = context.InputMultiset;
localOutput = new Multiset();
break;
case 1:
//Input becomes current Output and Output is new empty multiset
initialInput = context.OutputMultiset;
localOutput = new Multiset();
break;
default:
//Input is join of previous input and ouput and Output is new empty multiset
if (context.InputMultiset.IsDisjointWith(context.OutputMultiset))
{
//Disjoint so do a Product
initialInput = context.InputMultiset.Product(context.OutputMultiset);
}
else
{
//Normal Join
initialInput = context.InputMultiset.Join(context.OutputMultiset);
}
localOutput = new Multiset();
break;
}
context.InputMultiset = initialInput;
context.OutputMultiset = localOutput;
//Get the Triple Pattern we're evaluating
ITriplePattern temp = this._triplePatterns[pattern];
int resultsFound = 0;
if (temp is TriplePattern)
{
//Find the first Triple which matches the Pattern
TriplePattern tp = (TriplePattern)temp;
foreach (Triple t in tp.GetTriples(context))
{
//Remember to check for Timeout during lazy evaluation
context.CheckTimeout();
if (tp.Accepts(context, t))
{
resultsFound++;
context.OutputMultiset.Add(tp.CreateResult(t));
//Recurse unless we're the last pattern
if (pattern < this._triplePatterns.Count - 1)
{
results = this.StreamingEvaluate(context, pattern + 1, out halt);
//If recursion leads to a halt then we halt and return immediately
if (halt) return results;
//Otherwise we need to keep going here
//So must reset our input and outputs before continuing
context.InputMultiset = initialInput;
context.OutputMultiset = new Multiset();
resultsFound--;
}
else
{
//If we're at the last pattern and we've found a match then we can halt
halt = true;
//Generate the final output and return it
if (context.InputMultiset.IsDisjointWith(context.OutputMultiset))
{
//Disjoint so do a Product
context.OutputMultiset = context.InputMultiset.ProductWithTimeout(context.OutputMultiset, context.QueryTimeout - context.QueryTime);
}
else
{
//Normal Join
context.OutputMultiset = context.InputMultiset.Join(context.OutputMultiset);
}
return context.OutputMultiset;
}
}
}
}
else if (temp is FilterPattern)
{
FilterPattern fp = (FilterPattern)temp;
ISparqlFilter filter = fp.Filter;
ISparqlExpression expr = filter.Expression;
//Find the first result of those we've got so far that matches
if (context.InputMultiset is IdentityMultiset || context.InputMultiset.IsEmpty)
{
try
{
//If the Input is the Identity Multiset then the Output is either
//the Identity/Null Multiset depending on whether the Expression evaluates to true
if (expr.EffectiveBooleanValue(context, 0))
{
context.OutputMultiset = new IdentityMultiset();
}
else
{
context.OutputMultiset = new NullMultiset();
}
}
catch
{
//If Expression fails to evaluate then result is NullMultiset
context.OutputMultiset = new NullMultiset();
}
}
else
{
foreach (int id in context.InputMultiset.SetIDs)
{
//Remember to check for Timeout during lazy evaluation
context.CheckTimeout();
try
{
if (expr.EffectiveBooleanValue(context, id))
{
resultsFound++;
context.OutputMultiset.Add(context.InputMultiset[id]);
//Recurse unless we're the last pattern
if (pattern < this._triplePatterns.Count - 1)
{
results = this.StreamingEvaluate(context, pattern + 1, out halt);
//If recursion leads to a halt then we halt and return immediately
if (halt) return results;
//Otherwise we need to keep going here
//So must reset our input and outputs before continuing
context.InputMultiset = initialInput;
context.OutputMultiset = new Multiset();
resultsFound--;
}
else
{
//If we're at the last pattern and we've found a match then we can halt
halt = true;
//Generate the final output and return it
if (context.InputMultiset.IsDisjointWith(context.OutputMultiset))
{
//Disjoint so do a Product
context.OutputMultiset = context.InputMultiset.ProductWithTimeout(context.OutputMultiset, context.RemainingTimeout);
}
else
{
//Normal Join
context.OutputMultiset = context.InputMultiset.Join(context.OutputMultiset);
}
return context.OutputMultiset;
}
}
}
catch
{
//Ignore expression evaluation errors
}
}
}
}
//If we found no possibles we return the null multiset
if (resultsFound == 0) return new NullMultiset();
//We should never reach here so throw an error to that effect
//The reason we'll never reach here is that this method should always return earlier
throw new RdfQueryException("Unexpected control flow in evaluating a Streamed BGP for an ASK query");
}
private BaseMultiset StreamingEvaluate(SparqlEvaluationContext context, int pattern, out bool halt)
{
halt = false;
//Handle Empty BGPs
if (pattern == 0 && this._triplePatterns.Count == 0)
{
context.OutputMultiset = new IdentityMultiset();
return(context.OutputMultiset);
}
BaseMultiset initialInput, localOutput, results = null;
//Determine whether the Pattern modifies the existing Input rather than joining to it
bool modifies = (this._triplePatterns[pattern] is FilterPattern);
bool extended = (pattern > 0 && this._triplePatterns[pattern - 1] is BindPattern);
bool modified = (pattern > 0 && this._triplePatterns[pattern - 1] is FilterPattern);
//Set up the Input and Output Multiset appropriately
switch (pattern)
{
case 0:
//Input is as given and Output is new empty multiset
if (!modifies)
{
initialInput = context.InputMultiset;
}
else
{
//If the Pattern will modify the Input and is the first thing in the BGP then it actually modifies a new empty input
//This takes care of FILTERs being out of scope
initialInput = new Multiset();
}
localOutput = new Multiset();
break;
case 1:
//Input becomes current Output and Output is new empty multiset
initialInput = context.OutputMultiset;
localOutput = new Multiset();
break;
default:
if (!extended && !modified)
{
//Input is join of previous input and output and Output is new empty multiset
if (context.InputMultiset.IsDisjointWith(context.OutputMultiset))
{
//Disjoint so do a Product
initialInput = context.InputMultiset.ProductWithTimeout(context.OutputMultiset, context.RemainingTimeout);
}
else
{
//Normal Join
initialInput = context.InputMultiset.Join(context.OutputMultiset);
}
}
else
{
initialInput = context.OutputMultiset;
}
localOutput = new Multiset();
break;
}
context.InputMultiset = initialInput;
context.OutputMultiset = localOutput;
//Get the Triple Pattern we're evaluating
ITriplePattern temp = this._triplePatterns[pattern];
int resultsFound = 0;
int prevResults = -1;
if (temp is TriplePattern)
{
//Find the first Triple which matches the Pattern
TriplePattern tp = (TriplePattern)temp;
IEnumerable <Triple> ts = tp.GetTriples(context);
//In the case that we're lazily evaluating an optimisable ORDER BY then
//we need to apply OrderBy()'s to our enumeration
//This only applies to the 1st pattern
if (pattern == 0)
{
if (context.Query != null)
{
if (context.Query.OrderBy != null && context.Query.IsOptimisableOrderBy)
{
IComparer <Triple> comparer = context.Query.OrderBy.GetComparer(tp);
if (comparer != null)
{
ts = ts.OrderBy(t => t, comparer);
}
else
{
//Can't get a comparer so can't optimise
this._requiredResults = -1;
}
}
}
}
foreach (Triple t in ts)
{
//Remember to check for Timeouts during Lazy Evaluation
context.CheckTimeout();
if (tp.Accepts(context, t))
{
resultsFound++;
if (tp.IndexType == TripleIndexType.NoVariables)
{
localOutput = new IdentityMultiset();
context.OutputMultiset = localOutput;
}
else
{
context.OutputMultiset.Add(tp.CreateResult(t));
}
//Recurse unless we're the last pattern
if (pattern < this._triplePatterns.Count - 1)
{
results = this.StreamingEvaluate(context, pattern + 1, out halt);
//If recursion leads to a halt then we halt and return immediately
if (halt && results.Count >= this._requiredResults && this._requiredResults != -1)
{
return(results);
}
else if (halt)
{
if (results.Count == 0)
{
//If recursing leads to no results then eliminate all outputs
//Also reset to prevResults to -1
resultsFound = 0;
localOutput = new Multiset();
prevResults = -1;
}
else if (prevResults > -1)
{
if (results.Count == prevResults)
{
//If the amount of results found hasn't increased then this match does not
//generate any further solutions further down the recursion so we can eliminate
//this from the results
localOutput.Remove(localOutput.SetIDs.Max());
}
}
prevResults = results.Count;
//If we're supposed to halt but not reached the number of required results then continue
context.InputMultiset = initialInput;
context.OutputMultiset = localOutput;
}
else
{
//Otherwise we need to keep going here
//So must reset our input and outputs before continuing
context.InputMultiset = initialInput;
context.OutputMultiset = new Multiset();
resultsFound--;
}
}
else
{
//If we're at the last pattern and we've found a match then we can halt
halt = true;
//Generate the final output and return it
if (context.InputMultiset.IsDisjointWith(context.OutputMultiset))
{
//Disjoint so do a Product
results = context.InputMultiset.ProductWithTimeout(context.OutputMultiset, context.RemainingTimeout);
}
else
{
//Normal Join
results = context.InputMultiset.Join(context.OutputMultiset);
}
//If not reached required number of results continue
if (results.Count >= this._requiredResults && this._requiredResults != -1)
{
context.OutputMultiset = results;
return(context.OutputMultiset);
}
}
}
}
}
else if (temp is FilterPattern)
{
FilterPattern filter = (FilterPattern)temp;
ISparqlExpression filterExpr = filter.Filter.Expression;
if (filter.Variables.IsDisjoint(context.InputMultiset.Variables))
{
//Remember to check for Timeouts during Lazy Evaluation
context.CheckTimeout();
//Filter is Disjoint so determine whether it has any affect or not
if (filter.Variables.Any())
{
//Has Variables but disjoint from input => not in scope so gets ignored
//Do we recurse or not?
if (pattern < this._triplePatterns.Count - 1)
{
//Recurse and return
results = this.StreamingEvaluate(context, pattern + 1, out halt);
return(results);
}
else
{
//We don't affect the input in any way so just return it
return(context.InputMultiset);
}
}
else
{
//No Variables so have to evaluate it to see if it gives true otherwise
try
{
if (filterExpr.EffectiveBooleanValue(context, 0))
{
if (pattern < this._triplePatterns.Count - 1)
{
//Recurse and return
results = this.StreamingEvaluate(context, pattern + 1, out halt);
return(results);
}
else
{
//Last Pattern and we evaluate to true so can return the input as-is
halt = true;
return(context.InputMultiset);
}
}
}
catch (RdfQueryException)
{
//Evaluates to false so eliminates all solutions (use an empty Multiset)
return(new Multiset());
}
}
}
else
{
//Remember to check for Timeouts during Lazy Evaluation
context.CheckTimeout();
//Test each solution found so far against the Filter and eliminate those that evalute to false/error
foreach (int id in context.InputMultiset.SetIDs.ToList())
{
try
{
if (filterExpr.EffectiveBooleanValue(context, id))
{
//If evaluates to true then add to output
context.OutputMultiset.Add(context.InputMultiset[id]);
}
}
catch (RdfQueryException)
{
//Error means we ignore the solution
}
}
//Remember to check for Timeouts during Lazy Evaluation
context.CheckTimeout();
//Decide whether to recurse or not
resultsFound = context.OutputMultiset.Count;
if (pattern < this._triplePatterns.Count - 1)
{
//Recurse then return
//We can never decide whether to recurse again at this point as we are not capable of deciding
//which solutions should be dumped (that is the job of an earlier pattern in the BGP)
results = this.StreamingEvaluate(context, pattern + 1, out halt);
return(results);
}
else
{
halt = true;
//However many results we need we'll halt - previous patterns can call us again if they find more potential solutions
//for us to filter
return(context.OutputMultiset);
}
}
}
else if (temp is BindPattern)
{
BindPattern bind = (BindPattern)temp;
ISparqlExpression bindExpr = bind.AssignExpression;
String bindVar = bind.VariableName;
if (context.InputMultiset.ContainsVariable(bindVar))
{
throw new RdfQueryException("Cannot use a BIND assigment to BIND to a variable that has previously been used in the Query");
}
else
{
//Remember to check for Timeouts during Lazy Evaluation
context.CheckTimeout();
//Compute the Binding for every value
context.OutputMultiset.AddVariable(bindVar);
foreach (ISet s in context.InputMultiset.Sets)
{
ISet x = s.Copy();
try
{
INode val = bindExpr.Value(context, s.ID);
x.Add(bindVar, val);
}
catch (RdfQueryException)
{
//Equivalent to no assignment but the solution is preserved
}
context.OutputMultiset.Add(x);
}
//Remember to check for Timeouts during Lazy Evaluation
context.CheckTimeout();
//Decide whether to recurse or not
resultsFound = context.OutputMultiset.Count;
if (pattern < this._triplePatterns.Count - 1)
{
//Recurse then return
results = this.StreamingEvaluate(context, pattern + 1, out halt);
return(results);
}
else
{
halt = true;
//However many results we need we'll halt - previous patterns can call us again if they find more potential solutions
//for us to extend
return(context.OutputMultiset);
}
}
}
else
{
throw new RdfQueryException("Encountered a " + temp.GetType().FullName + " which is not a lazily evaluable Pattern");
}
//If we found no possibles we return the null multiset
if (resultsFound == 0)
{
return(new NullMultiset());
}
else
{
//Generate the final output and return it
if (!modifies)
{
if (context.InputMultiset.IsDisjointWith(context.OutputMultiset))
{
//Disjoint so do a Product
results = context.InputMultiset.ProductWithTimeout(context.OutputMultiset, context.RemainingTimeout);
}
else
{
//Normal Join
results = context.InputMultiset.Join(context.OutputMultiset);
}
context.OutputMultiset = results;
}
return(context.OutputMultiset);
}
}
/// <summary>
/// Joins this Multiset to another Multiset
/// </summary>
/// <param name="other">Other Multiset</param>
/// <returns></returns>
public override BaseMultiset Join(BaseMultiset other)
{
//If the Other is the Identity Multiset the result is this Multiset
if (other is IdentityMultiset) return this;
//If the Other is the Null Multiset the result is the Null Multiset
if (other is NullMultiset) return other;
//If the Other is Empty then the result is the Null Multiset
if (other.IsEmpty) return new NullMultiset();
//Find the First Variable from this Multiset which is in both Multisets
//If there is no Variable from this Multiset in the other Multiset then this
//should be a Join operation instead of a LeftJoin
List<String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0) return this.Product(other);
//Start building the Joined Set
Multiset joinedSet = new Multiset();
//This is the old Join algorithm which while correct is O(n^2) so scales terribly
//foreach (ISet x in this.Sets)
//{
// //For sets to be compatible for every joinable variable they must either have a null for the
// //variable in one of the sets or if they have values the values must be equal
// ////This first check is to try speed things up, it looks whether there are solutions that may match
// ////without needing to do a full table scan of the RHS results as the subsequent LINQ call will do
// ////if (!joinVars.All(v => x[v] == null || other.ContainsValue(v, x[v]) || other.ContainsValue(v, null))) continue;
// IEnumerable<ISet> ys = other.Sets.Where(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
// //IEnumerable<ISet> ys = other.Sets.Where(s => s.IsCompatibleWith(x, joinVars));
// foreach (ISet y in ys)
// {
// joinedSet.Add(x.Join(y));
// }
//}
//This is the new Join algorithm which is also correct but is O(2n) so much faster and scalable
//Downside is that it does require more memory than the old algorithm
List<HashTable<INode, int>> values = new List<HashTable<INode, int>>();
List<List<int>> nulls = new List<List<int>>();
foreach (String var in joinVars)
{
values.Add(new HashTable<INode, int>(HashTableBias.Enumeration));
nulls.Add(new List<int>());
}
//First do a pass over the LHS Result to find all possible values for joined variables
foreach (ISet x in this.Sets)
{
int i = 0;
foreach (String var in joinVars)
{
INode value = x[var];
if (value != null)
{
values[i].Add(value, x.ID);
}
else
{
nulls[i].Add(x.ID);
}
i++;
}
}
#if NET40 && !SILVERLIGHT
if (Options.UsePLinqEvaluation)
{
//Use a paralllel join
other.Sets.AsParallel().ForAll(y => EvalJoin(y, joinVars, values, nulls, joinedSet));
}
else
{
#endif
//Use a serial join
//Then do a pass over the RHS and work out the intersections
foreach (ISet y in other.Sets)
{
this.EvalJoin(y, joinVars, values, nulls, joinedSet);
}
#if NET40 && !SILVERLIGHT
}
#endif
return joinedSet;
}
public void SparqlMultisetLeftJoin()
{
//Create a load of Nodes to use in the tests
Graph g = new Graph();
g.NamespaceMap.AddNamespace(String.Empty, new Uri("http://example.org"));
IUriNode s1 = g.CreateUriNode(":s1");
IUriNode s2 = g.CreateUriNode(":s2");
IUriNode p1 = g.CreateUriNode(":p1");
IUriNode p2 = g.CreateUriNode(":p2");
IUriNode rdfsLabel = g.CreateUriNode("rdfs:label");
ILiteralNode o1 = g.CreateLiteralNode("Some Text");
ILiteralNode o2 = g.CreateLiteralNode("1", new Uri(XmlSpecsHelper.XmlSchemaDataTypeInteger));
//Create an ID and Null Multiset
IdentityMultiset id = new IdentityMultiset();
NullMultiset nullset = new NullMultiset();
//Create and Populate a Multiset
Multiset m = new Multiset();
Set s = new Set();
s.Add("s", s1);
s.Add("p", p1);
s.Add("o", o1);
m.Add(s);
s = new Set();
s.Add("s", s2);
s.Add("p", p2);
s.Add("o", o2);
m.Add(s);
//Create and Populate another Multiset
Multiset n = new Multiset();
s = new Set();
s.Add("s", s1);
s.Add("label", o1);
n.Add(s);
//Create and Populate another Multiset
Multiset d = new Multiset();
s = new Set();
s.Add("s1", s1);
s.Add("p1", p1);
s.Add("o1", o1);
d.Add(s);
s = new Set();
s.Add("s1", s2);
s.Add("p1", p2);
s.Add("o1", o2);
d.Add(s);
//Show the Sets
Console.WriteLine("LHS");
foreach (Set set in m.Sets)
{
Console.WriteLine(set.ToString());
}
Console.WriteLine();
Console.WriteLine("RHS");
foreach (Set set in n.Sets)
{
Console.WriteLine(set.ToString());
}
Console.WriteLine();
Console.WriteLine("D");
foreach (Set set in d.Sets)
{
Console.WriteLine(set.ToString());
}
Console.WriteLine();
//Try a Join to Identity
Console.WriteLine("Join ID-LHS");
BaseMultiset join = id.Join(m);
foreach (Set set in join.Sets)
{
Console.WriteLine(set.ToString());
}
Console.WriteLine();
//Try a Join to Identity
Console.WriteLine("Join LHS-ID");
join = m.Join(id);
foreach (Set set in join.Sets)
{
Console.WriteLine(set.ToString());
}
Console.WriteLine();
//Try a Join to Null
Console.WriteLine("Join NULL-LHS");
join = nullset.Join(m);
foreach (Set set in join.Sets)
{
Console.WriteLine(set.ToString());
}
Console.WriteLine();
//Try a Join to Null
Console.WriteLine("Join LHS-NULL");
join = m.Join(nullset);
foreach (Set set in join.Sets)
{
Console.WriteLine(set.ToString());
}
Console.WriteLine();
//Try a LeftJoin
Console.WriteLine("LeftJoin NULL-LHS");
BaseMultiset leftjoin = nullset.LeftJoin(m, new BooleanExpressionTerm(true));
foreach (Set set in leftjoin.Sets)
{
Console.WriteLine(set.ToString());
}
Console.WriteLine();
//Try a LeftJoin
Console.WriteLine("LeftJoin LHS-NULL");
leftjoin = m.LeftJoin(nullset, new BooleanExpressionTerm(true));
foreach (Set set in leftjoin.Sets)
{
Console.WriteLine(set.ToString());
}
Console.WriteLine();
//Try a Join
Console.WriteLine("Join LHS-RHS");
join = m.Join(n);
foreach (Set set in join.Sets)
{
Console.WriteLine(set.ToString());
}
Console.WriteLine();
//Try a LeftOuterJoin
Console.WriteLine("LeftJoin LHS-RHS");
leftjoin = m.LeftJoin(n, new BooleanExpressionTerm(true));
foreach (Set set in leftjoin.Sets)
{
Console.WriteLine(set.ToString());
}
Console.WriteLine();
//Try a Produce
Console.WriteLine("Product LHS-RHS");
BaseMultiset product = m.Product(n);
foreach (Set set in product.Sets)
{
Console.WriteLine(set.ToString());
}
Console.WriteLine();
//Try a Join to Self
Console.WriteLine("Product LHS-D");
product = m.Product(d);
foreach (Set set in product.Sets)
{
Console.WriteLine(set.ToString());
}
Console.WriteLine();
//Try a Union
Console.WriteLine("Union LHS-RHS");
BaseMultiset union = m.Union(n);
foreach (Set set in union.Sets)
{
Console.WriteLine(set.ToString());
}
Console.WriteLine();
}
/// <summary>
/// Does a Minus Join of this Multiset to another Multiset where any joinable results are subtracted from this Multiset to give the resulting Multiset
/// </summary>
/// <param name="other">Other Multiset</param>
/// <returns></returns>
public override BaseMultiset MinusJoin(BaseMultiset other)
{
//If the other Multiset is the Identity/Null Multiset then minus-ing it doesn't alter this set
if (other is IdentityMultiset) return this;
if (other is NullMultiset) return this;
//If the other Multiset is disjoint then minus-ing it also doesn't alter this set
if (this.IsDisjointWith(other)) return this;
//Find the Variables that are to be used for Joining
List<String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0) return this.Product(other);
//Start building the Joined Set
Multiset joinedSet = new Multiset();
//This is the old algorithm which is correct but naive and has O(n^2) complexity
//foreach (ISet x in this.Sets)
//{
// //New Minus logic based on the improved Join() logic
// bool minus = other.Sets.Any(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
// //If no compatible sets then this set is preserved
// if (!minus)
// {
// joinedSet.Add(x);
// }
//}
//This is the new algorithm which is also correct but is O(3n) so much faster and scalable
//Downside is that it does require more memory than the old algorithm
List<HashTable<INode, int>> values = new List<HashTable<INode, int>>();
List<List<int>> nulls = new List<List<int>>();
foreach (String var in joinVars)
{
values.Add(new HashTable<INode, int>(HashTableBias.Enumeration));
nulls.Add(new List<int>());
}
//First do a pass over the LHS Result to find all possible values for joined variables
foreach (ISet x in this.Sets)
{
int i = 0;
foreach (String var in joinVars)
{
INode value = x[var];
if (value != null)
{
values[i].Add(value, x.ID);
}
else
{
nulls[i].Add(x.ID);
}
i++;
}
}
//Then do a pass over the RHS and work out the intersections
HashSet<int> toMinus = new HashSet<int>();
foreach (ISet y in other.Sets)
{
IEnumerable<int> possMatches = null;
int i = 0;
foreach (String var in joinVars)
{
INode value = y[var];
if (value != null)
{
if (values[i].ContainsKey(value))
{
possMatches = (possMatches == null ? values[i].GetValues(value).Concat(nulls[i]) : possMatches.Intersect(values[i].GetValues(value).Concat(nulls[i])));
}
else
{
possMatches = Enumerable.Empty<int>();
break;
}
}
else
{
//Don't forget that a null will be potentially compatible with everything
possMatches = (possMatches == null ? this.SetIDs : possMatches.Intersect(this.SetIDs));
}
i++;
}
if (possMatches == null) continue;
//Look at possible matches, if is a valid match then mark the matched set for minus'ing
//Don't reconsider sets which have already been marked for minusing
foreach (int poss in possMatches)
{
if (toMinus.Contains(poss)) continue;
if (this._sets[poss].IsCompatibleWith(y, joinVars))
{
toMinus.Add(poss);
}
}
}
//Apply the actual minus
if (toMinus.Count == this.Count)
{
//If number of sets to minus is equal to number of sets then we're minusing everything
return new NullMultiset();
}
else
{
//Otherwise iterate
foreach (ISet x in this.Sets)
{
if (!toMinus.Contains(x.ID))
{
joinedSet.Add(x.Copy());
}
}
}
return joinedSet;
}
/// <summary>
/// Does a Left Join of this Multiset to another Multiset where the Join is predicated on the given Expression
/// </summary>
/// <param name="other">Other Multiset</param>
/// <param name="expr">Expression</param>
/// <returns></returns>
public override BaseMultiset LeftJoin(BaseMultiset other, ISparqlExpression expr)
{
//If the Other is the Identity/Null Multiset the result is this Multiset
if (other is IdentityMultiset)
{
return(this);
}
if (other is NullMultiset)
{
return(this);
}
if (other.IsEmpty)
{
return(this);
}
Multiset joinedSet = new Multiset();
LeviathanLeftJoinBinder binder = new LeviathanLeftJoinBinder(joinedSet);
SparqlEvaluationContext subcontext = new SparqlEvaluationContext(binder);
//Find the First Variable from this Multiset which is in both Multisets
//If there is no Variable from this Multiset in the other Multiset then this
//should be a Join operation instead of a LeftJoin
List <String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0)
{
//Calculate a Product filtering as we go
foreach (ISet x in this.Sets)
{
bool standalone = false;
foreach (ISet y in other.Sets)
{
ISet z = x.Join(y);
try
{
joinedSet.Add(z);
if (!expr.Evaluate(subcontext, z.ID).AsSafeBoolean())
{
joinedSet.Remove(z.ID);
standalone = true;
}
}
catch
{
joinedSet.Remove(z.ID);
standalone = true;
}
}
if (standalone)
{
joinedSet.Add(x.Copy());
}
}
}
else
{
//This is the old algorithm which is correct but has complexity O(n^2) so it scales terribly
//foreach (ISet x in this.Sets)
//{
// IEnumerable<ISet> ys = other.Sets.Where(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
// //IEnumerable<ISet> ys = other.Sets.Where(s => s.IsCompatibleWith(x, joinVars));
// bool standalone = false;
// int i = 0;
// foreach (ISet y in ys)
// {
// i++;
// ISet z = x.Join(y);
// try
// {
// joinedSet.Add(z);
// if (!expr.Evaluate(subcontext, z.ID).AsSafeBoolean())
// {
// joinedSet.Remove(z.ID);
// standalone = true;
// }
// }
// catch
// {
// joinedSet.Remove(z.ID);
// standalone = true;
// }
// }
// if (standalone || i == 0) joinedSet.Add(x);
//}
//This is the new Join algorithm which is also correct but is O(2n) so much faster and scalable
//Downside is that it does require more memory than the old algorithm
List <HashTable <INode, int> > values = new List <HashTable <INode, int> >();
List <List <int> > nulls = new List <List <int> >();
foreach (String var in joinVars)
{
values.Add(new HashTable <INode, int>(HashTableBias.Enumeration));
nulls.Add(new List <int>());
}
//First do a pass over the LHS Result to find all possible values for joined variables
HashSet <int> matched = new HashSet <int>();
HashSet <int> standalone = new HashSet <int>();
foreach (ISet x in this.Sets)
{
int i = 0;
foreach (String var in joinVars)
{
INode value = x[var];
if (value != null)
{
values[i].Add(value, x.ID);
}
else
{
nulls[i].Add(x.ID);
}
i++;
}
}
//Then do a pass over the RHS and work out the intersections
foreach (ISet y in other.Sets)
{
IEnumerable <int> possMatches = null;
int i = 0;
foreach (String var in joinVars)
{
INode value = y[var];
if (value != null)
{
if (values[i].ContainsKey(value))
{
possMatches = (possMatches == null ? values[i].GetValues(value).Concat(nulls[i]) : possMatches.Intersect(values[i].GetValues(value).Concat(nulls[i])));
}
else
{
possMatches = Enumerable.Empty <int>();
break;
}
}
else
{
//Don't forget that a null will be potentially compatible with everything
possMatches = (possMatches == null ? this.SetIDs : possMatches.Intersect(this.SetIDs));
}
i++;
}
if (possMatches == null)
{
continue;
}
//Now do the actual joins for the current set
//Note - We access the dictionary directly here because going through the this[int id] method
//incurs a Contains() call each time and we know the IDs must exist because they came from
//our dictionary originally!
foreach (int poss in possMatches)
{
if (this._sets[poss].IsCompatibleWith(y, joinVars))
{
ISet z = this._sets[poss].Join(y);
joinedSet.Add(z);
try
{
if (!expr.Evaluate(subcontext, z.ID).AsSafeBoolean())
{
joinedSet.Remove(z.ID);
standalone.Add(poss);
}
else
{
matched.Add(poss);
}
}
catch
{
joinedSet.Remove(z.ID);
standalone.Add(poss);
}
}
}
}
//Finally add in unmatched sets from LHS
foreach (int id in this.SetIDs)
{
if (!matched.Contains(id) || standalone.Contains(id))
{
joinedSet.Add(this._sets[id].Copy());
}
}
}
return(joinedSet);
}
/// <summary>
/// Converts a Bindings Clause to a Multiset
/// </summary>
/// <returns></returns>
public BaseMultiset ToMultiset()
{
if (this._vars.Any())
{
Multiset m = new Multiset();
foreach (String var in this._vars)
{
m.AddVariable(var);
}
foreach (BindingTuple tuple in this._tuples)
{
m.Add(new Set(tuple));
}
return m;
}
else
{
return new IdentityMultiset();
}
}
/// <summary>
/// Calculates the product of two mutlisets asynchronously with a timeout to restrict long running computations.
/// </summary>
/// <param name="multiset">Multiset.</param>
/// <param name="other">Other Multiset.</param>
/// <param name="timeout">Timeout, if <=0 no timeout is used and product will be computed sychronously.</param>
/// <returns></returns>
public static BaseMultiset ProductWithTimeout(this BaseMultiset multiset, BaseMultiset other, long timeout)
{
if (other is IdentityMultiset)
{
return(multiset);
}
if (other is NullMultiset)
{
return(other);
}
if (other.IsEmpty)
{
return(new NullMultiset());
}
// If no timeout use default implementation
if (timeout <= 0)
{
return(multiset.Product(other));
}
// Otherwise Invoke using an Async call
#if NET40
BaseMultiset productSet;
if (Options.UsePLinqEvaluation)
{
if (multiset.Count >= other.Count)
{
productSet = new PartitionedMultiset(multiset.Count, other.Count);
}
else
{
productSet = new PartitionedMultiset(other.Count, multiset.Count);
}
}
else
{
productSet = new Multiset();
}
#else
var productSet = new Multiset();
#endif
var stop = new StopToken();
var t = (int)Math.Min(timeout, int.MaxValue);
#if NET40 || NETSTANDARD1_4 || NETSTANDARD2_0
var productTask = Task.Factory.StartNew(() => GenerateProduct(multiset, other, productSet, stop));
if (!productTask.Wait(t))
{
stop.ShouldStop = true;
productTask.Wait();
}
return(productSet);
#else
GenerateProductDelegate d = new GenerateProductDelegate(GenerateProduct);
IAsyncResult r = d.BeginInvoke(multiset, other, productSet, stop, null, null);
// Wait
r.AsyncWaitHandle.WaitOne(t);
if (!r.IsCompleted)
{
stop.ShouldStop = true;
r.AsyncWaitHandle.WaitOne();
}
return(productSet);
#endif
}
/// <summary>
/// Joins this Multiset to another Multiset
/// </summary>
/// <param name="other">Other Multiset</param>
/// <returns></returns>
public override BaseMultiset Join(BaseMultiset other)
{
//If the Other is the Identity Multiset the result is this Multiset
if (other is IdentityMultiset) return this;
//If the Other is the Null Multiset the result is the Null Multiset
if (other is NullMultiset) return other;
//If the Other is Empty then the result is the Null Multiset
if (other.IsEmpty) return new NullMultiset();
//Find the First Variable from this Multiset which is in both Multisets
//If there is no Variable from this Multiset in the other Multiset then this
//should be a Join operation instead of a LeftJoin
List<String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0) return this.Product(other);
//Start building the Joined Set
Multiset joinedSet = new Multiset();
foreach (Set x in this.Sets)
{
//For sets to be compatible for every joinable variable they must either have a null for the
//variable in one of the sets or if they have values the values must be equal
IEnumerable<Set> ys = other.Sets.Where(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
foreach (Set y in ys)
{
joinedSet.Add(new Set(x, y));
}
}
return joinedSet;
}
/// <summary>
/// Does a Left Join of this Multiset to another Multiset where the Join is predicated on the given Expression
/// </summary>
/// <param name="other">Other Multiset</param>
/// <param name="expr">Expression</param>
/// <returns></returns>
public override BaseMultiset LeftJoin(BaseMultiset other, ISparqlExpression expr)
{
//If the Other is the Identity/Null Multiset the result is this Multiset
if (other is IdentityMultiset)
{
return(this);
}
if (other is NullMultiset)
{
return(this);
}
if (other.IsEmpty)
{
return(this);
}
Multiset joinedSet = new Multiset();
LeviathanLeftJoinBinder binder = new LeviathanLeftJoinBinder(joinedSet);
SparqlEvaluationContext subcontext = new SparqlEvaluationContext(binder);
//Find the First Variable from this Multiset which is in both Multisets
//If there is no Variable from this Multiset in the other Multiset then this
//should be a Join operation instead of a LeftJoin
List <String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0)
{
//Calculate a Product filtering as we go
foreach (ISet x in this.Sets)
{
bool standalone = false;
foreach (ISet y in other.Sets)
{
ISet z = x.Join(y);
try
{
joinedSet.Add(z);
if (!expr.EffectiveBooleanValue(subcontext, z.ID))
{
joinedSet.Remove(z.ID);
standalone = true;
}
}
catch
{
joinedSet.Remove(z.ID);
standalone = true;
}
}
if (standalone)
{
joinedSet.Add(x);
}
}
}
else
{
foreach (ISet x in this.Sets)
{
IEnumerable <ISet> ys = other.Sets.Where(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
//IEnumerable<ISet> ys = other.Sets.Where(s => s.IsCompatibleWith(x, joinVars));
bool standalone = false;
int i = 0;
foreach (ISet y in ys)
{
i++;
ISet z = x.Join(y);
try
{
joinedSet.Add(z);
if (!expr.EffectiveBooleanValue(subcontext, z.ID))
{
joinedSet.Remove(z.ID);
standalone = true;
}
}
catch
{
joinedSet.Remove(z.ID);
standalone = true;
}
}
if (standalone || i == 0)
{
joinedSet.Add(x);
}
}
}
return(joinedSet);
}
private BaseMultiset StreamingEvaluate(SparqlEvaluationContext context, int pattern, out bool halt)
{
halt = false;
//Handle Empty BGPs
if (pattern == 0 && this._triplePatterns.Count == 0)
{
context.OutputMultiset = new IdentityMultiset();
return(context.OutputMultiset);
}
BaseMultiset initialInput, localOutput, results;
//Set up the Input and Output Multiset appropriately
switch (pattern)
{
case 0:
//Input is as given and Output is new empty multiset
initialInput = context.InputMultiset;
localOutput = new Multiset();
break;
case 1:
//Input becomes current Output and Output is new empty multiset
initialInput = context.OutputMultiset;
localOutput = new Multiset();
break;
default:
//Input is join of previous input and ouput and Output is new empty multiset
if (context.InputMultiset.IsDisjointWith(context.OutputMultiset))
{
//Disjoint so do a Product
initialInput = context.InputMultiset.Product(context.OutputMultiset);
}
else
{
//Normal Join
initialInput = context.InputMultiset.Join(context.OutputMultiset);
}
localOutput = new Multiset();
break;
}
context.InputMultiset = initialInput;
context.OutputMultiset = localOutput;
//Get the Triple Pattern we're evaluating
ITriplePattern temp = this._triplePatterns[pattern];
int resultsFound = 0;
if (temp.PatternType == TriplePatternType.Match)
{
//Find the first Triple which matches the Pattern
IMatchTriplePattern tp = (IMatchTriplePattern)temp;
foreach (Triple t in tp.GetTriples(context))
{
//Remember to check for Timeout during lazy evaluation
context.CheckTimeout();
if (tp.Accepts(context, t))
{
resultsFound++;
context.OutputMultiset.Add(tp.CreateResult(t));
//Recurse unless we're the last pattern
if (pattern < this._triplePatterns.Count - 1)
{
results = this.StreamingEvaluate(context, pattern + 1, out halt);
//If recursion leads to a halt then we halt and return immediately
if (halt)
{
return(results);
}
//Otherwise we need to keep going here
//So must reset our input and outputs before continuing
context.InputMultiset = initialInput;
context.OutputMultiset = new Multiset();
resultsFound--;
}
else
{
//If we're at the last pattern and we've found a match then we can halt
halt = true;
//Generate the final output and return it
if (context.InputMultiset.IsDisjointWith(context.OutputMultiset))
{
//Disjoint so do a Product
context.OutputMultiset = context.InputMultiset.ProductWithTimeout(context.OutputMultiset, context.QueryTimeout - context.QueryTime);
}
else
{
//Normal Join
context.OutputMultiset = context.InputMultiset.Join(context.OutputMultiset);
}
return(context.OutputMultiset);
}
}
}
}
else if (temp.PatternType == TriplePatternType.Filter)
{
IFilterPattern fp = (IFilterPattern)temp;
ISparqlFilter filter = fp.Filter;
ISparqlExpression expr = filter.Expression;
//Find the first result of those we've got so far that matches
if (context.InputMultiset is IdentityMultiset || context.InputMultiset.IsEmpty)
{
try
{
//If the Input is the Identity Multiset then the Output is either
//the Identity/Null Multiset depending on whether the Expression evaluates to true
if (expr.Evaluate(context, 0).AsSafeBoolean())
{
context.OutputMultiset = new IdentityMultiset();
}
else
{
context.OutputMultiset = new NullMultiset();
}
}
catch
{
//If Expression fails to evaluate then result is NullMultiset
context.OutputMultiset = new NullMultiset();
}
}
else
{
foreach (int id in context.InputMultiset.SetIDs)
{
//Remember to check for Timeout during lazy evaluation
context.CheckTimeout();
try
{
if (expr.Evaluate(context, id).AsSafeBoolean())
{
resultsFound++;
context.OutputMultiset.Add(context.InputMultiset[id].Copy());
//Recurse unless we're the last pattern
if (pattern < this._triplePatterns.Count - 1)
{
results = this.StreamingEvaluate(context, pattern + 1, out halt);
//If recursion leads to a halt then we halt and return immediately
if (halt)
{
return(results);
}
//Otherwise we need to keep going here
//So must reset our input and outputs before continuing
context.InputMultiset = initialInput;
context.OutputMultiset = new Multiset();
resultsFound--;
}
else
{
//If we're at the last pattern and we've found a match then we can halt
halt = true;
//Generate the final output and return it
if (context.InputMultiset.IsDisjointWith(context.OutputMultiset))
{
//Disjoint so do a Product
context.OutputMultiset = context.InputMultiset.ProductWithTimeout(context.OutputMultiset, context.RemainingTimeout);
}
else
{
//Normal Join
context.OutputMultiset = context.InputMultiset.Join(context.OutputMultiset);
}
return(context.OutputMultiset);
}
}
}
catch
{
//Ignore expression evaluation errors
}
}
}
}
//If we found no possibles we return the null multiset
if (resultsFound == 0)
{
return(new NullMultiset());
}
//We should never reach here so throw an error to that effect
//The reason we'll never reach here is that this method should always return earlier
throw new RdfQueryException("Unexpected control flow in evaluating a Streamed BGP for an ASK query");
}
/// <summary>
/// Evaluates a setp of the Path
/// </summary>
/// <param name="context">Context</param>
/// <param name="path">Paths</param>
/// <param name="reverse">Whether to evaluate Paths in reverse</param>
/// <returns></returns>
protected List<INode> EvaluateStep(SparqlEvaluationContext context, List<INode> path, bool reverse)
{
if (this.Path is Property)
{
HashSet<INode> nodes = new HashSet<INode>();
INode predicate = ((Property)this.Path).Predicate;
IEnumerable<Triple> ts = (reverse ? context.Data.GetTriplesWithPredicateObject(predicate, path[path.Count - 1]) : context.Data.GetTriplesWithSubjectPredicate(path[path.Count - 1], predicate));
foreach (Triple t in ts)
{
if (reverse)
{
if (!path.Contains(t.Subject))
{
nodes.Add(t.Subject);
}
}
else
{
if (!path.Contains(t.Object))
{
nodes.Add(t.Object);
}
}
}
return nodes.ToList();
}
else
{
List<INode> nodes = new List<INode>();
BaseMultiset initialInput = context.InputMultiset;
Multiset currInput = new Multiset();
VariablePattern x = new VariablePattern("?x");
VariablePattern y = new VariablePattern("?y");
Set temp = new Set();
if (reverse)
{
temp.Add("y", path[path.Count - 1]);
}
else
{
temp.Add("x", path[path.Count - 1]);
}
currInput.Add(temp);
context.InputMultiset = currInput;
Bgp bgp = new Bgp(new PropertyPathPattern(x, this.Path, y));
BaseMultiset results = context.Evaluate(bgp);//bgp.Evaluate(context);
context.InputMultiset = initialInput;
if (!results.IsEmpty)
{
foreach (Set s in results.Sets)
{
if (reverse)
{
if (s["x"] != null)
{
if (!path.Contains(s["x"]))
{
nodes.Add(s["x"]);
}
}
}
else
{
if (s["y"] != null)
{
if (!path.Contains(s["y"]))
{
nodes.Add(s["y"]);
}
}
}
}
}
return nodes;
}
}
/// <summary>
/// Processes an INSERT command
/// </summary>
/// <param name="cmd">Insert Command</param>
/// <remarks>
/// <para>
/// <strong>Note:</strong> The underlying manager must implement the <see cref="IQueryableGenericIOManager">IQueryableGenericIOManager</see> interface in order for INSERT commands to be processed
/// </para>
/// </remarks>
public void ProcessInsertCommand(InsertCommand cmd)
{
if (this._manager is IUpdateableGenericIOManager)
{
((IUpdateableGenericIOManager)this._manager).Update(cmd.ToString());
}
else
{
if (this._manager is IQueryableGenericIOManager)
{
//Check IO Behaviour
//For a insert we either need the ability to Update Add Triples or to Overwrite Graphs
//Firstly check behaviour persuant to default graph if applicable
if (cmd.InsertPattern.TriplePatterns.OfType<IConstructTriplePattern>().Any())
{
//Must support notion of default graph
if ((this._manager.IOBehaviour & IOBehaviour.HasDefaultGraph) == 0) throw new SparqlUpdateException("The underlying store does not support the notion of an explicit unnamed Default Graph required to process this command");
//Must allow either OverwriteDefault or CanUpdateAddTriples
if ((this._manager.IOBehaviour & IOBehaviour.CanUpdateAddTriples) == 0 && (this._manager.IOBehaviour & IOBehaviour.OverwriteDefault) == 0) throw new SparqlUpdateException("The underlying store does not support the required IO Behaviour to implement this command");
}
//Then check behaviour persuant to named graphs if applicable
if (cmd.InsertPattern.HasChildGraphPatterns)
{
//Must support named graphs
if ((this._manager.IOBehaviour & IOBehaviour.HasNamedGraphs) == 0) throw new SparqlUpdateException("The underlying store does not support the notion of named graphs required to process this command");
//Must allow either CanUpdateAddTriples or OverwriteNamed
if ((this._manager.IOBehaviour & IOBehaviour.CanUpdateAddTriples) == 0 && (this._manager.IOBehaviour & IOBehaviour.OverwriteNamed) == 0) throw new SparqlUpdateException("The underlying store does not support the required IO Behaviour to implement this command");
}
//First build and make the query to get a Result Set
String queryText = "SELECT * WHERE " + cmd.WherePattern.ToString();
SparqlQueryParser parser = new SparqlQueryParser();
SparqlQuery query = parser.ParseFromString(queryText);
if (cmd.GraphUri != null && !cmd.UsingUris.Any()) query.AddDefaultGraph(cmd.GraphUri);
foreach (Uri u in cmd.UsingUris)
{
query.AddDefaultGraph(u);
}
foreach (Uri u in cmd.UsingNamedUris)
{
query.AddNamedGraph(u);
}
Object results = ((IQueryableGenericIOManager)this._manager).Query(query.ToString());
if (results is SparqlResultSet)
{
//Now need to transform the Result Set back to a Multiset
Multiset mset = new Multiset((SparqlResultSet)results);
//Generate the Triples for each Solution
List<Triple> insertedTriples = new List<Triple>();
Dictionary<String, List<Triple>> insertedGraphTriples = new Dictionary<string, List<Triple>>();
foreach (ISet s in mset.Sets)
{
List<Triple> tempInsertedTriples = new List<Triple>();
try
{
ConstructContext context = new ConstructContext(null, s, true);
foreach (IConstructTriplePattern p in cmd.InsertPattern.TriplePatterns.OfType<IConstructTriplePattern>())
{
try
{
tempInsertedTriples.Add(p.Construct(context));
}
catch (RdfQueryException)
{
//If we get an error here then it means we couldn't construct a specific
//triple so we continue anyway
}
}
insertedTriples.AddRange(tempInsertedTriples);
}
catch (RdfQueryException)
{
//If we get an error here this means we couldn't construct for this solution so the
//solution is ignore for this graph
}
//Triples from GRAPH clauses
foreach (GraphPattern gp in cmd.InsertPattern.ChildGraphPatterns)
{
tempInsertedTriples.Clear();
try
{
String graphUri;
switch (gp.GraphSpecifier.TokenType)
{
case Token.URI:
graphUri = gp.GraphSpecifier.Value;
break;
case Token.VARIABLE:
if (s.ContainsVariable(gp.GraphSpecifier.Value))
{
INode temp = s[gp.GraphSpecifier.Value.Substring(1)];
if (temp == null)
{
//If the Variable is not bound then skip
continue;
}
else if (temp.NodeType == NodeType.Uri)
{
graphUri = temp.ToSafeString();
}
else
{
//If the Variable is not bound to a URI then skip
continue;
}
}
else
{
//If the Variable is not bound for this solution then skip
continue;
}
break;
default:
//Any other Graph Specifier we have to ignore this solution
continue;
}
if (!insertedGraphTriples.ContainsKey(graphUri)) insertedGraphTriples.Add(graphUri, new List<Triple>());
ConstructContext context = new ConstructContext(null, s, true);
foreach (IConstructTriplePattern p in gp.TriplePatterns.OfType<IConstructTriplePattern>())
{
try
{
tempInsertedTriples.Add(p.Construct(context));
}
catch (RdfQueryException)
{
//If we get an error here then it means we couldn't construct a specific
//triple so we continue anyway
}
}
insertedGraphTriples[graphUri].AddRange(tempInsertedTriples);
}
catch (RdfQueryException)
{
//If we get an error here this means we couldn't construct for this solution so the
//solution is ignore for this graph
}
}
}
//Now decide how to apply the update
if (this._manager.UpdateSupported)
{
this._manager.UpdateGraph(cmd.GraphUri, insertedTriples, Enumerable.Empty<Triple>());
foreach (KeyValuePair<String, List<Triple>> graphInsertion in insertedGraphTriples)
{
this._manager.UpdateGraph(graphInsertion.Key, graphInsertion.Value, Enumerable.Empty<Triple>());
}
}
else
{
Graph g = new Graph();
this._manager.LoadGraph(g, cmd.GraphUri);
g.Assert(insertedTriples);
this._manager.SaveGraph(g);
foreach (KeyValuePair<String, List<Triple>> graphInsertion in insertedGraphTriples)
{
g = new Graph();
this._manager.LoadGraph(g, graphInsertion.Key);
g.Assert(graphInsertion.Value);
this._manager.SaveGraph(g);
}
}
}
else
{
throw new SparqlUpdateException("Cannot evaluate an INSERT Command as the underlying Store failed to answer the query for the WHERE portion of the command as expected");
}
}
else
{
throw new NotSupportedException("INSERT commands are not supported by this Update Processor as the manager for the underlying Store does not provide Query capabilities which are necessary to process this command");
}
}
}
/// <summary>
/// Does an Exists Join of this Multiset to another Multiset where the Join is predicated on the existence/non-existence of a joinable solution on the RHS
/// </summary>
/// <param name="other">Other Multiset</param>
/// <param name="mustExist">Whether a solution must exist in the Other Multiset for the join to be made</param>
/// <returns></returns>
public override BaseMultiset ExistsJoin(BaseMultiset other, bool mustExist)
{
//For EXISTS and NOT EXISTS if the other is the Identity then it has no effect
if (other is IdentityMultiset)
{
return(this);
}
if (mustExist)
{
//If an EXISTS then Null/Empty Other results in Null
if (other is NullMultiset)
{
return(other);
}
if (other.IsEmpty)
{
return(new NullMultiset());
}
}
else
{
//If a NOT EXISTS then Null/Empty results in this
if (other is NullMultiset)
{
return(this);
}
if (other.IsEmpty)
{
return(this);
}
}
//Find the Variables that are to be used for Joining
List <String> joinVars = this._variables.Where(v => other.Variables.Contains(v)).ToList();
if (joinVars.Count == 0)
{
//All Disjoint Solutions are compatible
if (mustExist)
{
//If an EXISTS and disjoint then result is this
return(this);
}
else
{
//If a NOT EXISTS and disjoint then result is null
return(new NullMultiset());
}
}
//Start building the Joined Set
Multiset joinedSet = new Multiset();
foreach (ISet x in this.Sets)
{
//New ExistsJoin() logic based on the improved Join() logic
bool exists = other.Sets.Any(s => joinVars.All(v => x[v] == null || s[v] == null || x[v].Equals(s[v])));
//bool exists = other.Sets.Any(s => s.IsCompatibleWith(x, joinVars));
if (exists)
{
//If there are compatible sets and this is an EXIST then preserve the solution
if (mustExist)
{
joinedSet.Add(x);
}
}
else
{
//If there are no compatible sets and this is a NOT EXISTS then preserve the solution
if (!mustExist)
{
joinedSet.Add(x);
}
}
}
return(joinedSet);
}
/// <summary>
/// Evaluates a setp of the Path
/// </summary>
/// <param name="context">Context</param>
/// <param name="path">Paths</param>
/// <param name="reverse">Whether to evaluate Paths in reverse</param>
/// <returns></returns>
protected List <INode> EvaluateStep(SparqlEvaluationContext context, List <INode> path, bool reverse)
{
if (this.Path is Property)
{
HashSet <INode> nodes = new HashSet <INode>();
INode predicate = ((Property)this.Path).Predicate;
IEnumerable <Triple> ts = (reverse ? context.Data.GetTriplesWithPredicateObject(predicate, path[path.Count - 1]) : context.Data.GetTriplesWithSubjectPredicate(path[path.Count - 1], predicate));
foreach (Triple t in ts)
{
if (reverse)
{
if (!path.Contains(t.Subject))
{
nodes.Add(t.Subject);
}
}
else
{
if (!path.Contains(t.Object))
{
nodes.Add(t.Object);
}
}
}
return(nodes.ToList());
}
else
{
HashSet <INode> nodes = new HashSet <INode>();
BaseMultiset initialInput = context.InputMultiset;
Multiset currInput = new Multiset();
VariablePattern x = new VariablePattern("?x");
VariablePattern y = new VariablePattern("?y");
Set temp = new Set();
if (reverse)
{
temp.Add("y", path[path.Count - 1]);
}
else
{
temp.Add("x", path[path.Count - 1]);
}
currInput.Add(temp);
context.InputMultiset = currInput;
Bgp bgp = new Bgp(new PropertyPathPattern(x, this.Path, y));
BaseMultiset results = context.Evaluate(bgp); //bgp.Evaluate(context);
context.InputMultiset = initialInput;
if (!results.IsEmpty)
{
foreach (ISet s in results.Sets)
{
if (reverse)
{
if (s["x"] != null)
{
if (!path.Contains(s["x"]))
{
nodes.Add(s["x"]);
}
}
}
else
{
if (s["y"] != null)
{
if (!path.Contains(s["y"]))
{
nodes.Add(s["y"]);
}
}
}
}
}
return(nodes.ToList());
}
}
private BaseMultiset StreamingEvaluate(SparqlEvaluationContext context, int pattern, out bool halt)
{
halt = false;
//Handle Empty BGPs
if (pattern == 0 && this._triplePatterns.Count == 0)
{
context.OutputMultiset = new IdentityMultiset();
return context.OutputMultiset;
}
BaseMultiset initialInput, localOutput, results = null;
//Determine whether the Pattern modifies the existing Input rather than joining to it
bool modifies = (this._triplePatterns[pattern] is FilterPattern);
bool extended = (pattern > 0 && this._triplePatterns[pattern-1] is BindPattern);
bool modified = (pattern > 0 && this._triplePatterns[pattern-1] is FilterPattern);
//Set up the Input and Output Multiset appropriately
switch (pattern)
{
case 0:
//Input is as given and Output is new empty multiset
if (!modifies)
{
initialInput = context.InputMultiset;
}
else
{
//If the Pattern will modify the Input and is the first thing in the BGP then it actually modifies a new empty input
//This takes care of FILTERs being out of scope
initialInput = new Multiset();
}
localOutput = new Multiset();
break;
case 1:
//Input becomes current Output and Output is new empty multiset
initialInput = context.OutputMultiset;
localOutput = new Multiset();
break;
default:
if (!extended && !modified)
{
//Input is join of previous input and output and Output is new empty multiset
if (context.InputMultiset.IsDisjointWith(context.OutputMultiset))
{
//Disjoint so do a Product
initialInput = context.InputMultiset.ProductWithTimeout(context.OutputMultiset, context.RemainingTimeout);
}
else
{
//Normal Join
initialInput = context.InputMultiset.Join(context.OutputMultiset);
}
}
else
{
initialInput = context.OutputMultiset;
}
localOutput = new Multiset();
break;
}
context.InputMultiset = initialInput;
context.OutputMultiset = localOutput;
//Get the Triple Pattern we're evaluating
ITriplePattern temp = this._triplePatterns[pattern];
int resultsFound = 0;
int prevResults = -1;
if (temp is TriplePattern)
{
//Find the first Triple which matches the Pattern
TriplePattern tp = (TriplePattern)temp;
IEnumerable<Triple> ts = tp.GetTriples(context);
//In the case that we're lazily evaluating an optimisable ORDER BY then
//we need to apply OrderBy()'s to our enumeration
//This only applies to the 1st pattern
if (pattern == 0)
{
if (context.Query != null)
{
if (context.Query.OrderBy != null && context.Query.IsOptimisableOrderBy)
{
IComparer<Triple> comparer = context.Query.OrderBy.GetComparer(tp);
if (comparer != null)
{
ts = ts.OrderBy(t => t, comparer);
}
else
{
//Can't get a comparer so can't optimise
this._requiredResults = -1;
}
}
}
}
foreach (Triple t in ts)
{
//Remember to check for Timeouts during Lazy Evaluation
context.CheckTimeout();
if (tp.Accepts(context, t))
{
resultsFound++;
if (tp.IndexType == TripleIndexType.NoVariables)
{
localOutput = new IdentityMultiset();
context.OutputMultiset = localOutput;
}
else
{
context.OutputMultiset.Add(tp.CreateResult(t));
}
//Recurse unless we're the last pattern
if (pattern < this._triplePatterns.Count - 1)
{
results = this.StreamingEvaluate(context, pattern + 1, out halt);
//If recursion leads to a halt then we halt and return immediately
if (halt && results.Count >= this._requiredResults && this._requiredResults != -1)
{
return results;
}
else if (halt)
{
if (results.Count == 0)
{
//If recursing leads to no results then eliminate all outputs
//Also reset to prevResults to -1
resultsFound = 0;
localOutput = new Multiset();
prevResults = -1;
}
else if (prevResults > -1)
{
if (results.Count == prevResults)
{
//If the amount of results found hasn't increased then this match does not
//generate any further solutions further down the recursion so we can eliminate
//this from the results
localOutput.Remove(localOutput.SetIDs.Max());
}
}
prevResults = results.Count;
//If we're supposed to halt but not reached the number of required results then continue
context.InputMultiset = initialInput;
context.OutputMultiset = localOutput;
}
else
{
//Otherwise we need to keep going here
//So must reset our input and outputs before continuing
context.InputMultiset = initialInput;
context.OutputMultiset = new Multiset();
resultsFound--;
}
}
else
{
//If we're at the last pattern and we've found a match then we can halt
halt = true;
//Generate the final output and return it
if (context.InputMultiset.IsDisjointWith(context.OutputMultiset))
{
//Disjoint so do a Product
results = context.InputMultiset.ProductWithTimeout(context.OutputMultiset, context.RemainingTimeout);
}
else
{
//Normal Join
results = context.InputMultiset.Join(context.OutputMultiset);
}
//If not reached required number of results continue
if (results.Count >= this._requiredResults && this._requiredResults != -1)
{
context.OutputMultiset = results;
return context.OutputMultiset;
}
}
}
}
}
else if (temp is FilterPattern)
{
FilterPattern filter = (FilterPattern)temp;
ISparqlExpression filterExpr = filter.Filter.Expression;
if (filter.Variables.IsDisjoint(context.InputMultiset.Variables))
{
//Remember to check for Timeouts during Lazy Evaluation
context.CheckTimeout();
//Filter is Disjoint so determine whether it has any affect or not
if (filter.Variables.Any())
{
//Has Variables but disjoint from input => not in scope so gets ignored
//Do we recurse or not?
if (pattern < this._triplePatterns.Count - 1)
{
//Recurse and return
results = this.StreamingEvaluate(context, pattern + 1, out halt);
return results;
}
else
{
//We don't affect the input in any way so just return it
return context.InputMultiset;
}
}
else
{
//No Variables so have to evaluate it to see if it gives true otherwise
try
{
if (filterExpr.Evaluate(context, 0).AsSafeBoolean())
{
if (pattern < this._triplePatterns.Count - 1)
{
//Recurse and return
results = this.StreamingEvaluate(context, pattern + 1, out halt);
return results;
}
else
{
//Last Pattern and we evaluate to true so can return the input as-is
halt = true;
return context.InputMultiset;
}
}
}
catch (RdfQueryException)
{
//Evaluates to false so eliminates all solutions (use an empty Multiset)
return new Multiset();
}
}
}
else
{
//Remember to check for Timeouts during Lazy Evaluation
context.CheckTimeout();
//Test each solution found so far against the Filter and eliminate those that evalute to false/error
foreach (int id in context.InputMultiset.SetIDs.ToList())
{
try
{
if (filterExpr.Evaluate(context, id).AsSafeBoolean())
{
//If evaluates to true then add to output
context.OutputMultiset.Add(context.InputMultiset[id].Copy());
}
}
catch (RdfQueryException)
{
//Error means we ignore the solution
}
}
//Remember to check for Timeouts during Lazy Evaluation
context.CheckTimeout();
//Decide whether to recurse or not
resultsFound = context.OutputMultiset.Count;
if (pattern < this._triplePatterns.Count - 1)
{
//Recurse then return
//We can never decide whether to recurse again at this point as we are not capable of deciding
//which solutions should be dumped (that is the job of an earlier pattern in the BGP)
results = this.StreamingEvaluate(context, pattern + 1, out halt);
return results;
}
else
{
halt = true;
//However many results we need we'll halt - previous patterns can call us again if they find more potential solutions
//for us to filter
return context.OutputMultiset;
}
}
}
else if (temp is BindPattern)
{
BindPattern bind = (BindPattern)temp;
ISparqlExpression bindExpr = bind.AssignExpression;
String bindVar = bind.VariableName;
if (context.InputMultiset.ContainsVariable(bindVar))
{
throw new RdfQueryException("Cannot use a BIND assigment to BIND to a variable that has previously been used in the Query");
}
else
{
//Remember to check for Timeouts during Lazy Evaluation
context.CheckTimeout();
//Compute the Binding for every value
context.OutputMultiset.AddVariable(bindVar);
foreach (ISet s in context.InputMultiset.Sets)
{
ISet x = s.Copy();
try
{
INode val = bindExpr.Evaluate(context, s.ID);
x.Add(bindVar, val);
}
catch (RdfQueryException)
{
//Equivalent to no assignment but the solution is preserved
}
context.OutputMultiset.Add(x.Copy());
}
//Remember to check for Timeouts during Lazy Evaluation
context.CheckTimeout();
//Decide whether to recurse or not
resultsFound = context.OutputMultiset.Count;
if (pattern < this._triplePatterns.Count - 1)
{
//Recurse then return
results = this.StreamingEvaluate(context, pattern + 1, out halt);
return results;
}
else
{
halt = true;
//However many results we need we'll halt - previous patterns can call us again if they find more potential solutions
//for us to extend
return context.OutputMultiset;
}
}
}
else
{
throw new RdfQueryException("Encountered a " + temp.GetType().FullName + " which is not a lazily evaluable Pattern");
}
//If we found no possibles we return the null multiset
if (resultsFound == 0)
{
return new NullMultiset();
}
else
{
//Generate the final output and return it
if (!modifies)
{
if (context.InputMultiset.IsDisjointWith(context.OutputMultiset))
{
//Disjoint so do a Product
results = context.InputMultiset.ProductWithTimeout(context.OutputMultiset, context.RemainingTimeout);
}
else
{
//Normal Join
results = context.InputMultiset.Join(context.OutputMultiset);
}
context.OutputMultiset = results;
}
return context.OutputMultiset;
}
}
