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Contents
module SPARQL; module Algebra
class Operator
##
# The SPARQL GraphPattern `order` operator.
#
# @example
# (prefix ((foaf: <http://xmlns.com/foaf/0.1/>))
# (project (?name)
# (order ((asc ?name))
# (bgp (triple ?x foaf:name ?name)))))
#
# @see https://www.w3.org/TR/sparql11-query/#modOrderBy
class Order < Operator::Binary
include Query
NAME = [:order]
##
# Executes this query on the given `queryable` graph or repository.
# Orders a solution set returned by executing operand(1) using
# an array of expressions and/or variables specified in operand(0)
#
# @param [RDF::Queryable] queryable
# the graph or repository to query
# @param [Hash{Symbol => Object}] options
# any additional keyword options
# @yield [solution]
# each matching solution
# @yieldparam [RDF::Query::Solution] solution
# @yieldreturn [void] ignored
# @return [RDF::Query::Solutions]
# the resulting solution sequence
# @see https://www.w3.org/TR/sparql11-query/#sparqlAlgebra
def execute(queryable, **options, &block)
debug(options) {"Order"}
@solutions = queryable.query(operands.last, depth: options[:depth].to_i + 1, **options).order do |a, b|
operand(0).inject(0) do |memo, op|
debug(options) {"(order) #{op.inspect}"}
memo = begin
a_eval = op.evaluate(a, queryable: queryable, depth: options[:depth].to_i + 1, **options) rescue nil
b_eval = op.evaluate(b, queryable: queryable, depth: options[:depth].to_i + 1, **options) rescue nil
comp = Operator::Compare.evaluate(a_eval, b_eval).to_i
comp = -comp if op.is_a?(Operator::Desc)
comp
end if memo == 0
memo
end
end
@solutions.each(&block) if block_given?
@solutions
end
end # Order
end # Operator
end; end # SPARQL::Algebra
Version data entries
5 entries across 5 versions & 1 rubygems