Class: SPARQL::Algebra::Operator::Distinct

Inherits:
Operator::Unary
  • Object
show all
Includes:
Query
Defined in:
lib/sparql/algebra/operator/distinct.rb

Overview

The SPARQL GraphPattern distinct operator.

[9] SelectClause ::= 'SELECT' ( 'DISTINCT' | 'REDUCED' )? ( ( Var | ( '(' Expression 'AS' Var ')' ) )+ | '*' )

Examples:

SPARQL Grammar

PREFIX : <http://example.org/>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
SELECT DISTINCT ?v
WHERE { ?x ?p ?v }

SSE

(prefix ((: <http://example.org/>)
         (xsd: <http://www.w3.org/2001/XMLSchema#>))
  (distinct
    (project (?v)
      (bgp (triple ?x ?p ?v)))))

See Also:

Constant Summary collapse

NAME = 
[:distinct]

Instance Attribute Summary

Attributes included from Query

#solutions

Instance Method Summary collapse

Methods included from Query

#each_solution, #empty?, #failed?, #graph_name=, #matched?, #query_yields_boolean?, #query_yields_solutions?, #query_yields_statements?, #unshift, #variables

Instance Method Details

#execute(queryable, **options) {|solution| ... } ⇒ RDF::Query::Solutions

Executes this query on the given queryable graph or repository. Removes duplicate solutions from the solution set.

Parameters:

  • queryable (RDF::Queryable) —

    the graph or repository to query

  • options (Hash{Symbol => Object}) —

    any additional keyword options

Yields:

  • (solution) —

    each matching solution

Yield Parameters:

Yield Returns:

  • (void) —

    ignored

Returns:

See Also:



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# File 'lib/sparql/algebra/operator/distinct.rb', line 42

def execute(queryable, **options, &block)
  @solutions = queryable.query(operands.last, **options.merge(depth: options[:depth].to_i + 1)).distinct
  @solutions.each(&block) if block_given?
  @solutions
end

#to_sparql(**options) ⇒ String

Returns a partial SPARQL grammar for this operator.

Returns:

  • (String) 


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# File 'lib/sparql/algebra/operator/distinct.rb', line 53

def to_sparql(**options)
  operands.first.to_sparql(distinct: true, **options)
end