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module SPARQL; module Algebra
class Operator
##
# The SPARQL logical `exists` operator.
#
# There is a filter operator EXISTS that takes a graph pattern. EXISTS returns `true`/`false` depending on whether the pattern matches the dataset given the bindings in the current group graph pattern, the dataset and the active graph at this point in the query evaluation. No additional binding of variables occurs. The `NOT EXISTS` form translates into `fn:not(EXISTS{...})`.
#
# @example
# (prefix ((ex: <http://www.example.org/>))
# (filter (exists (bgp (triple ?s ?p ex:o)))
# (bgp (triple ?s ?p ?o))))
#
# @see https://www.w3.org/TR/sparql11-query/#func-filter-exists
class Exists < Operator::Unary
include Evaluatable
NAME = [:exists]
##
# Exvaluating this operator executes the query in the first operator passing in each existing bindings.
#
# @param [RDF::Query::Solution] bindings
# a query solution containing zero or more variable bindings
# @param [Hash{Symbol => Object}] options ({})
# options passed from query
# @option options[RDF::Queryable] queryable
# queryable to execute, using bindings as an initial solution.
# @return [RDF::Literal::Boolean] `true` or `false`
def evaluate(bindings, **options)
queryable = options[:queryable]
!operand(0).execute(queryable, solutions: RDF::Query::Solutions(bindings),
depth: options[:depth].to_i + 1,
**options).empty?
end
end # Exists
end # Operator
end; end # SPARQL::Algebra
Version data entries
7 entries across 7 versions & 1 rubygems