Class: SPARQL::Algebra::Operator::PathOpt

Inherits:
Unary show all
Includes:
Query
Defined in:
vendor/bundler/ruby/2.5.0/bundler/gems/sparql-bb59900f675b/lib/sparql/algebra/operator/path_opt.rb

Overview

The SPARQL Property Path path? (ZeroOrOnePath) operator.

Constant Summary

NAME =
:path?

Constants inherited from Unary

Unary::ARITY

Constants inherited from SPARQL::Algebra::Operator

ARITY, IsURI, URI

Instance Attribute Summary

Attributes included from Query

#solutions

Attributes inherited from SPARQL::Algebra::Operator

#operands

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

Methods inherited from Unary

#initialize

Methods inherited from SPARQL::Algebra::Operator

#aggregate?, arity, #base_uri, base_uri, base_uri=, #boolean, #constant?, #each_descendant, #eql?, #evaluatable?, evaluate, #executable?, #first_ancestor, for, #initialize, #inspect, #ndvars, #node?, #operand, #optimize, #parent, #parent=, prefixes, #prefixes, prefixes=, #rewrite, #to_binary, #to_sxp, #to_sxp_bin, #validate!, #variable?, #vars

Methods included from Expression

cast, #constant?, #evaluate, extension, extensions, for, #invalid?, new, #node?, open, #optimize, parse, register_extension, #to_sxp_bin, #valid?, #validate!, #variable?

Constructor Details

This class inherits a constructor from SPARQL::Algebra::Operator::Unary

Instance Method Details

#execute(queryable, options = {}) {|solution| ... } ⇒ Object

Equivalent to:

(path x (path? :p) y) => (union (bgp ((x :p y))) (filter (x = x) (solution x y)))

Parameters:

  • queryable (RDF::Queryable)

    the graph or repository to query

  • options (Hash{Symbol => Object}) (defaults to: {})

    any additional keyword options

Options Hash (options):

Yields:

  • (solution)

    each matching solution

Yield Parameters:

Yield Returns:

  • (void)

    ignored

See Also:



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# File 'vendor/bundler/ruby/2.5.0/bundler/gems/sparql-bb59900f675b/lib/sparql/algebra/operator/path_opt.rb', line 33

def execute(queryable, options = {}, &block)
  subject, object = options[:subject], options[:object]
  debug(options) {"Path? #{[subject, operands, object].to_sse}"}

  solutions = RDF::Query::Solutions.new
  # Solutions where subject == object with no predicate
  case
  when subject.variable? && object.variable?
    # Nodes is the set of all subjects and objects in queryable
    # FIXME: should this be Queryable#enum_nodes?
    # All subjects which are `object`
    query = RDF::Query.new {|q| q.pattern(subject: subject)}
    queryable.query(query, options) do |solution|
      solution.merge!(object.to_sym => solution[subject])
      debug(options) {"(solution-s0)-> #{solution.to_h.to_sse}"}
      solutions << solution
    end if query.valid?

    # All objects which are `object`
    query = RDF::Query.new {|q| q.pattern(object: object)}
    queryable.query(query, options) do |solution|
      solution.merge!(subject.to_sym => solution[object])
      debug(options) {"(solution-o0)-> #{solution.to_h.to_sse}"}
      solutions << solution
    end if query.valid?
  when subject.variable?
    # All subjects which are `object`
    query = RDF::Query.new {|q| q.pattern(subject: object)}
    queryable.query(query, options) do |solution|
      solution.merge!(subject.to_sym => object)
      debug(options) {"(solution-s0)-> #{solution.to_h.to_sse}"}
      solutions << solution
    end if query.valid?

    # All objects which are `object`
    query = RDF::Query.new {|q| q.pattern(object: object)}
    queryable.query(query, options) do |solution|
      solution.merge!(subject.to_sym => object)
      debug(options) {"(solution-o0)-> #{solution.to_h.to_sse}"}
      solutions << solution
    end if query.valid?
  when object.variable?
    # All subjects which are `subject`
    query = RDF::Query.new {|q| q.pattern(subject: subject)}
    queryable.query(query, options) do |solution|
      solution.merge!(object.to_sym => subject)
      debug(options) {"(solution-s0)-> #{solution.to_h.to_sse}"}
      solutions << solution
    end if query.valid?

    # All objects which are `subject
    query = RDF::Query.new {|q| q.pattern(object: subject)}
    queryable.query(query, options) do |solution|
      solution.merge!(object.to_sym => subject)
      debug(options) {"(solution-o0)-> #{solution.to_h.to_sse}"}
      solutions << solution
    end if query.valid?
  else
    # Otherwise, if subject == object, an empty solution
    solutions << RDF::Query::Solution.new if subject == object
  end

  # Solutions where predicate exists
  query = if operand.is_a?(RDF::Term)
    RDF::Query.new do |q|
      q.pattern [subject, operand, object]
    end
  else
    operand
  end

  # Recurse into query
  solutions += 
  queryable.query(query, options.merge(depth: options[:depth].to_i + 1))
  solutions.each(&block) if block_given?
  solutions
end