class LD::Patch::Algebra::Delete

The LD Patch ‘delete` operator (incuding `deleteExisting`).

The Add operation is used to delete triples from the target graph with or without checking to see if the exist already.

@example

(add ((<a> <b> <c>)))

Constants

NAME

Public Instance Methods

execute(queryable, options = {}) click to toggle source

Executes this upate on the given ‘writable` graph or repository.

@param [RDF::Queryable] queryable

the graph or repository to write

@param [Hash{Symbol => Object}] options

any additional options

@option options [Boolean] :existing

Specifies that triples must already exist in the target graph

@return [RDF::Query::Solutions] A single solution including passed bindings with ‘var` bound to the solution. @raise [Error]

If `existing` is specified, and any triple is not found in the traget graph, or if unbound variables are used.

@see www.w3.org/TR/sparql11-update/

# File lib/ld/patch/algebra/delete.rb, line 30
def execute(queryable, options = {})
  debug(options) {"Delete"}
  bindings = options.fetch(:bindings)
  solution = bindings.first

  # Bind variables to triples
  triples = operand(0).dup.replace_vars! do |var|
    case var
    when RDF::Query::Pattern
      s = var.bind(solution)
      raise LD::Patch::Error.new("Operand uses unbound pattern #{var.inspect}", code: 400) if s.variable?
      s
    when RDF::Query::Variable
      raise LD::Patch::Error.new("Operand uses unbound variable #{var.inspect}", code: 400) unless solution.bound?(var)
      solution[var]
    end
  end

  # If `:new` is specified, verify that no triple in triples exists in queryable
  if @options[:existing]
    triples.each do |triple|
      raise LD::Patch::Error, "Target graph does not contain triple #{triple.to_ntriples}" unless queryable.has_statement?(triple)
    end
  end

  queryable.delete(*triples)
  bindings
end