class SPARQL::Algebra::Operator::Union
The SPARQL
GraphPattern `union` operator.
@example
(prefix ((: <http://example/>)) (union (bgp (triple ?s ?p ?o)) (graph ?g (bgp (triple ?s ?p ?o)))))
Constants
- NAME
Public Instance Methods
execute(queryable, **options, &block)
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Executes each operand with `queryable` and performs the `union` operation by creating a new solution set consiting of all solutions from both operands.
@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/union.rb, line 34 def execute(queryable, **options, &block) debug(options) {"Union"} @solutions = RDF::Query::Solutions(operands.inject([]) do |memo, op| solns = op.execute(queryable, depth: options[:depth].to_i + 1, **options) debug(options) {"=> (op) #{solns.inspect}"} memo + solns end) debug(options) {"=> #{@solutions.inspect}"} @solutions.each(&block) if block_given? @solutions end
optimize!(**options)
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Optimizes this query.
Optimize operands and remove any which are empty.
@return [self] @see SPARQL::Algebra::Expression#optimize!
# File lib/sparql/algebra/operator/union.rb, line 64 def optimize!(**options) ops = operands.map {|o| o.optimize(**options) }.select {|o| o.respond_to?(:empty?) && !o.empty?} @operands = ops self end
validate!()
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The same blank node label cannot be used in two different basic graph patterns in the same query
Calls superclass method
SPARQL::Algebra::Operator#validate!
# File lib/sparql/algebra/operator/union.rb, line 47 def validate! left_nodes, right_nodes = operand(0).ndvars.map(&:name), operand(1).ndvars.map(&:name) unless (left_nodes.compact & right_nodes.compact).empty? raise ArgumentError, "sub-operands share non-distinguished variables: #{(left_nodes.compact & right_nodes.compact).to_sse}" end super end