/// <summary>
/// Converts the Query into it's SPARQL Algebra representation (as represented in the Leviathan API)
/// </summary>
/// <returns></returns>
public ISparqlAlgebra ToAlgebra()
{
//Firstly Transform the Root Graph Pattern to SPARQL Algebra
ISparqlAlgebra pattern;
if (this._rootGraphPattern != null)
{
if (Options.AlgebraOptimisation)
{
//If using Algebra Optimisation may use a special algebra in some cases
switch (this.SpecialType)
{
case SparqlSpecialQueryType.DistinctGraphs:
pattern = new SelectDistinctGraphs(this.Variables.First(v => v.IsResultVariable).Name);
break;
case SparqlSpecialQueryType.AskAnyTriples:
pattern = new AskAnyTriples();
break;
case SparqlSpecialQueryType.NotApplicable:
default:
//If not just use the standard transform
pattern = this._rootGraphPattern.ToAlgebra();
break;
}
}
else
{
//If not using Algebra Optimisation just use the standard transform
pattern = this._rootGraphPattern.ToAlgebra();
}
}
else
{
pattern = new Bgp();
}
//If we have a BINDINGS clause then we'll add it into the algebra here
if (this._bindings != null)
{
pattern = new Bindings(this._bindings, pattern);
}
//Then we apply any optimisers followed by relevant solution modifiers
switch (this._type)
{
case SparqlQueryType.Ask:
//Apply Algebra Optimisation is enabled
if (Options.AlgebraOptimisation)
{
pattern = this.ApplyAlgebraOptimisations(pattern);
}
return(new Ask(pattern));
case SparqlQueryType.Construct:
case SparqlQueryType.Describe:
case SparqlQueryType.DescribeAll:
case SparqlQueryType.Select:
case SparqlQueryType.SelectAll:
case SparqlQueryType.SelectAllDistinct:
case SparqlQueryType.SelectAllReduced:
case SparqlQueryType.SelectDistinct:
case SparqlQueryType.SelectReduced:
//Apply Algebra Optimisation if enabled
if (Options.AlgebraOptimisation)
{
pattern = this.ApplyAlgebraOptimisations(pattern);
}
//GROUP BY is the first thing applied
if (this._groupBy != null)
{
pattern = new GroupBy(pattern, this._groupBy);
}
//After grouping we do projection
//This will generate the values for any Project Expressions and Aggregates
pattern = new Project(pattern, this.Variables);
//Add HAVING clause after the projection
if (this._having != null)
{
pattern = new Having(pattern, this._having);
}
//We can then Order our results
//We do ordering before we do Select but after Project so we can order by any of
//the project expressions/aggregates and any variable in the results even if
//it won't be output as a result variable
if (this._orderBy != null)
{
pattern = new OrderBy(pattern, this._orderBy);
}
//After Ordering we apply Select
//Select effectively trims the results so only result variables are left
//This doesn't apply to CONSTRUCT since any variable may be used in the Construct Template
//so we don't want to eliminate anything
if (this._type != SparqlQueryType.Construct)
{
pattern = new Select(pattern, this.Variables);
}
//If we have a Distinct/Reduced then we'll apply those after Selection
if (this._type == SparqlQueryType.SelectAllDistinct || this._type == SparqlQueryType.SelectDistinct)
{
pattern = new Distinct(pattern);
}
else if (this._type == SparqlQueryType.SelectAllReduced || this._type == SparqlQueryType.SelectReduced)
{
pattern = new Reduced(pattern);
}
//Finally we can apply any limit and/or offset
if (this._limit >= 0 || this._offset > 0)
{
pattern = new Slice(pattern, this._limit, this._offset);
}
return(pattern);
default:
throw new RdfQueryException("Unable to convert unknown Query Types to SPARQL Algebra");
}
}
/// <summary>
/// Converts the Query into it's SPARQL Algebra representation (as represented in the Leviathan API)
/// </summary>
/// <returns></returns>
public ISparqlAlgebra ToAlgebra()
{
//Depending on how the query gets built we may not have had graph pattern optimization applied
//which we should do here if query optimization is enabled
if (!this.IsOptimised && Options.QueryOptimisation)
{
this.Optimise();
}
//Firstly Transform the Root Graph Pattern to SPARQL Algebra
ISparqlAlgebra algebra;
if (this._rootGraphPattern != null)
{
if (Options.AlgebraOptimisation)
{
//If using Algebra Optimisation may use a special algebra in some cases
switch (this.SpecialType)
{
case SparqlSpecialQueryType.DistinctGraphs:
algebra = new SelectDistinctGraphs(this.Variables.First(v => v.IsResultVariable).Name);
break;
case SparqlSpecialQueryType.AskAnyTriples:
algebra = new AskAnyTriples();
break;
case SparqlSpecialQueryType.NotApplicable:
default:
//If not just use the standard transform
algebra = this._rootGraphPattern.ToAlgebra();
break;
}
}
else
{
//If not using Algebra Optimisation just use the standard transform
algebra = this._rootGraphPattern.ToAlgebra();
}
}
else
{
//No root graph pattern means empty BGP
algebra = new Bgp();
}
//If we have a top level VALUES clause then we'll add it into the algebra here
if (this._bindings != null)
{
algebra = Join.CreateJoin(algebra, new Bindings(this._bindings));
}
//Then we apply any optimisers followed by relevant solution modifiers
switch (this._type)
{
case SparqlQueryType.Ask:
//Apply Algebra Optimisation is enabled
if (Options.AlgebraOptimisation)
{
algebra = this.ApplyAlgebraOptimisations(algebra);
}
return(new Ask(algebra));
case SparqlQueryType.Construct:
case SparqlQueryType.Describe:
case SparqlQueryType.DescribeAll:
case SparqlQueryType.Select:
case SparqlQueryType.SelectAll:
case SparqlQueryType.SelectAllDistinct:
case SparqlQueryType.SelectAllReduced:
case SparqlQueryType.SelectDistinct:
case SparqlQueryType.SelectReduced:
//Apply Algebra Optimisation if enabled
if (Options.AlgebraOptimisation)
{
algebra = this.ApplyAlgebraOptimisations(algebra);
}
//GROUP BY is the first thing applied
//This applies if there is a GROUP BY or if there are aggregates
//With no GROUP BY it produces a single group of all results
if (this._groupBy != null || this._vars.Any(v => v.IsAggregate))
{
algebra = new GroupBy(algebra, this._groupBy, this._vars.Where(v => v.IsAggregate));
}
//After grouping we do projection
//We introduce an Extend for each Project Expression
foreach (SparqlVariable var in this._vars)
{
if (var.IsProjection)
{
algebra = new Extend(algebra, var.Projection, var.Name);
}
}
//Add HAVING clause after the projection
if (this._having != null)
{
algebra = new Having(algebra, this._having);
}
//We can then Order our results
//We do ordering before we do Select but after Project so we can order by any of
//the project expressions/aggregates and any variable in the results even if
//it won't be output as a result variable
if (this._orderBy != null)
{
algebra = new OrderBy(algebra, this._orderBy);
}
//After Ordering we apply Select
//Select effectively trims the results so only result variables are left
//This doesn't apply to CONSTRUCT since any variable may be used in the Construct Template
//so we don't want to eliminate anything
if (this._type != SparqlQueryType.Construct)
{
algebra = new Select(algebra, this.Variables);
}
//If we have a Distinct/Reduced then we'll apply those after Selection
if (this._type == SparqlQueryType.SelectAllDistinct || this._type == SparqlQueryType.SelectDistinct)
{
algebra = new Distinct(algebra);
}
else if (this._type == SparqlQueryType.SelectAllReduced || this._type == SparqlQueryType.SelectReduced)
{
algebra = new Reduced(algebra);
}
//Finally we can apply any limit and/or offset
if (this._limit >= 0 || this._offset > 0)
{
algebra = new Slice(algebra, this._limit, this._offset);
}
return(algebra);
default:
throw new RdfQueryException("Unable to convert unknown Query Types to SPARQL Algebra");
}
}