Class: SPARQL::Algebra::Operator::Clear

Inherits:
SPARQL::Algebra::Operator show all
Includes:
Update
Defined in:
lib/sparql/algebra/operator/clear.rb

Overview

The SPARQL UPDATE clear operator.

The CLEAR operation removes all the triples in the specified graph(s) in the Graph Store.

[32] Clear ::= ‘CLEAR’ ‘SILENT’? GraphRefAll

Examples:

SPARQL Grammar (SILENT DEFAULT)

CLEAR SILENT DEFAULT

SSE (SILENT DEFAULT)

(update (clear silent default))

SPARQL Grammar (IRI)

CLEAR GRAPH <http://example.com/>

SSE (IRI)

(update (clear <http://example.com/>))

See Also:

Constant Summary collapse

NAME = 
[:clear]

Constants inherited from SPARQL::Algebra::Operator

ARITY, IsURI, URI

Constants included from Expression

Expression::PATTERN_PARENTS

Instance Attribute Summary

Attributes inherited from SPARQL::Algebra::Operator

#operands

Instance Method Summary collapse

Methods included from Update

#graph_name=, #unshift, #variables

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, #initialize, #inspect, #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?

Constructor Details

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

Instance Method Details

#execute(queryable, **options) ⇒ RDF::Queryable

Executes this upate on the given writable graph or repository.

Parameters:

  • queryable (RDF::Queryable) —

    the graph or repository to write

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

    any additional keyword options

Options Hash (**options):

  • debug (Boolean) —

    Query execution debugging

Returns:

Raises:

  • (IOError) —

    If from does not exist, unless the silent operator is present

See Also:



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# File 'lib/sparql/algebra/operator/clear.rb', line 43

def execute(queryable, **options)
  debug(options) {"Clear"}
  silent = operands.first == :silent
  operands.shift if silent

  raise ArgumentError, "clear expected operand to be 'default', 'named', 'all', or an IRI" unless operands.length == 1
  case operands.last
  when :default
    queryable.each_graph do |g|
      g.clear! unless g.graph_name
    end
  when :named
    queryable.each_graph do |g|
      g.clear! if g.graph_name
    end
  when :all
    queryable.clear!
  when RDF::URI
    if g = queryable.each_graph.detect {|c| c.graph_name == operands.last}
      g.clear!
    else
      raise IOError, "clear operation graph does not exist" unless silent
    end
  else
    raise ArgumentError, "clear expected operand to be 'default', 'named', 'all', or an IRI" 
  end

  queryable
end

#to_sparql(**options) ⇒ String

Returns a partial SPARQL grammar for this operator.

Returns:

  • (String) 


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# File 'lib/sparql/algebra/operator/clear.rb', line 78

def to_sparql(**options)
  silent = operands.first == :silent
  str = "CLEAR "
  str << "SILENT " if operands.first == :silent
  str << "GRAPH " if operands.last.is_a?(RDF::URI)
  str << operands.last.to_sparql(**options)
end