Class: SPARQL::Algebra::Operator::Count

Inherits:

SPARQL::Algebra::Operator

• Object
• SPARQL::Algebra::Operator
• SPARQL::Algebra::Operator::Count

Includes:

Aggregate

Defined in:

vendor/bundler/ruby/3.3.0/bundler/gems/sparql-796d3be4aa08/lib/sparql/algebra/operator/count.rb

Overview

The SPARQL count set function.

[127] Aggregate::= 'COUNT' '(' 'DISTINCT'? ( '*' | Expression ) ')' ...

Examples:

SPARQL Grammar

PREFIX : <http://www.example.org/>
SELECT (COUNT(?O) AS ?C)
WHERE { ?S ?P ?O }

SSE

(prefix ((: <http://www.example.org/>))
  (project (?C)
    (extend ((?C ??.0))
      (group () ((??.0 (count ?O)))
        (bgp (triple ?S ?P ?O))))))

SPARQL Grammar (count(*))

PREFIX : <http://www.example.org>

SELECT (COUNT(*) AS ?C)
WHERE { ?S ?P ?O }

SSE (count(*))

(prefix
 ((: <http://www.example.org>))
 (project (?C)
  (extend ((?C ??.0))
   (group () ((??.0 (count)))
    (bgp (triple ?S ?P ?O))))))

SPARQL Grammar (count(distinct *))

PREFIX : <http://www.example.org>

SELECT (COUNT(DISTINCT *) AS ?C)
WHERE { ?S ?P ?O }

SSE (count(distinct *))

(prefix
 ((: <http://www.example.org>))
 (project (?C)
  (extend ((?C ??.0))
   (group () ((??.0 (count distinct)))
    (bgp (triple ?S ?P ?O))))))

See Also:

• https://www.w3.org/TR/sparql11-query/#defn_aggCount

Constant Summary

NAME =

:count

Constants inherited from SPARQL::Algebra::Operator

ARITY, IsURI, URI

Constants included from Expression

Expression::PATTERN_PARENTS

Constants included from RDF::Util::Logger

RDF::Util::Logger::IOWrapper

Instance Attribute Summary

Attributes inherited from SPARQL::Algebra::Operator

#operands

Instance Method Summary

• #apply(enum, **options) ⇒ RDF::Literal::Integer

  Count is a SPARQL set function which counts the number of times a given expression has a bound, and non-error value within the aggregate group.

• #to_sparql(**options) ⇒ String

  Returns a partial SPARQL grammar for this operator.

Methods included from Aggregate

#aggregate, #replace_aggregate!, #replace_vars!

Methods inherited from SPARQL::Algebra::Operator

#aggregate?, arity, base_uri, #base_uri, base_uri=, #bind, #boolean, #constant?, #deep_dup, #each_descendant, #eql?, #evaluatable?, evaluate, #executable?, #first_ancestor, for, #formulae, #initialize, #inspect, #mergable?, #ndvars, #node?, #operand, #optimize, #optimize!, #parent, #parent=, #prefixes, prefixes, prefixes=, #rewrite, #to_binary, to_sparql, #to_sxp, #to_sxp_bin, #validate!, #variable?, #variables, #vars

Methods included from Expression

cast, #constant?, #evaluate, extension, extension?, extensions, for, #invalid?, new, #node?, open, #optimize, #optimize!, parse, register_extension, #to_sxp_bin, #valid?, #validate!, #variable?

Methods included from RDF::Util::Logger

#log_debug, #log_depth, #log_error, #log_fatal, #log_info, #log_recover, #log_recovering?, #log_statistics, #log_warn, #logger

Constructor Details

This class inherits a constructor from SPARQL::Algebra::Operator

Instance Method Details

#apply(enum, **options) ⇒ RDF::Literal::Integer

Count is a SPARQL set function which counts the number of times a given expression has a bound, and non-error value within the aggregate group.

Parameters:

• enum (Enumerable<Array<RDF::Term>>) —

  enum of evaluated operand

Returns:

• (RDF::Literal::Integer) —

  The number of non-error terms in the multiset

# File 'vendor/bundler/ruby/3.3.0/bundler/gems/sparql-796d3be4aa08/lib/sparql/algebra/operator/count.rb', line 60

def apply(enum, **options)
  RDF::Literal(enum.length)
end

#to_sparql(**options) ⇒ String

Returns a partial SPARQL grammar for this operator.

Returns:

• (String)

# File 'vendor/bundler/ruby/3.3.0/bundler/gems/sparql-796d3be4aa08/lib/sparql/algebra/operator/count.rb', line 69

def to_sparql(**options)
  distinct = operands.first == :distinct
  args = distinct ? operands[1..-1] : operands
  "COUNT(#{'DISTINCT ' if distinct}#{args.empty? ? '*' : args.to_sparql(**options)})"
end