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

Inherits:
Operator
  • Object
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]

Instance Method Summary collapse

Methods included from Update

#empty?, #graph_name=, #unshift, #variables

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