class SPARQL::Algebra::Operator::Order
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)))))
Constants
- NAME
Public Instance Methods
execute(queryable, **options, &block)
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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 www.w3.org/TR/sparql11-query/#sparqlAlgebra
# File lib/sparql/algebra/operator/order.rb, line 34 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 = begin Operator::Compare.evaluate(a_eval, b_eval, order_by: true).to_s.to_i rescue TypeError # Type sError is effectively zero debug(options) {"(order) rescue(#{$!}): #{a_eval.inspect}, #{b_eval.inspect}"} RDF::Literal(0) end comp = -comp if op.is_a?(Operator::Desc) comp end if memo == 0 memo end end @solutions.each(&block) if block_given? @solutions end