Class: SPARQL::Algebra::Operator::Exists

Inherits:

Unary

• Object
• SPARQL::Algebra::Operator
• Unary
• SPARQL::Algebra::Operator::Exists

Includes:

Evaluatable

Defined in:

vendor/bundler/ruby/2.5.0/bundler/gems/sparql-683a29666c28/lib/sparql/algebra/operator/exists.rb

Overview

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{...}).

Examples:

(prefix ((ex: <http://www.example.org/>))
  (filter (exists (bgp (triple ?s ?p ex:o)))
  (bgp (triple ?s ?p ?o))))

See Also:

• http://www.w3.org/TR/sparql11-query/#func-filter-exists

Constant Summary

NAME =

[:exists]

Constants inherited from Unary

Unary::ARITY

Constants inherited from SPARQL::Algebra::Operator

ARITY, IsURI, URI

Instance Attribute Summary

Attributes inherited from SPARQL::Algebra::Operator

#operands

Instance Method Summary

• #evaluate(bindings, options = {}) ⇒ RDF::Literal::Boolean

  Exvaluating this operator executes the query in the first operator passing in each existing bindings.

Methods included from Evaluatable

#apply, #memoize, #replace_aggregate!, #replace_vars!

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?, 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

#evaluate(bindings, options = {}) ⇒ RDF::Literal::Boolean

Exvaluating this operator executes the query in the first operator passing in each existing bindings.

Parameters:

• bindings (RDF::Query::Solution) —

  a query solution containing zero or more variable bindings

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

  ({}) options passed from query

• options[RDF::Queryable] (Hash) —

  a customizable set of options

Returns:

• (RDF::Literal::Boolean) —

  true or false

# File 'vendor/bundler/ruby/2.5.0/bundler/gems/sparql-683a29666c28/lib/sparql/algebra/operator/exists.rb', line 29

def evaluate(bindings, options = {})
  queryable = options[:queryable]
  !operand(0).execute(queryable, options.merge(
                                  solutions: RDF::Query::Solutions(bindings),
                                  depth: options[:depth].to_i + 1)).empty?
end