Class: SPARQL::Algebra::Operator::DeleteWhere

Inherits:
Unary show all
Includes:
Update
Defined in:
lib/sparql/algebra/operator/delete_where.rb

Overview

The SPARQL UPDATE deleteWhere operator.

The DELETE WHERE operation is a shortcut form for the DELETE/INSERT operation where bindings matched by the WHERE clause are used to define the triples in a graph that will be deleted.

[40] DeleteWhere ::= ‘DELETE WHERE’ QuadPattern

Examples:

SPARQL Grammar

PREFIX     : <http://example.org/> 
PREFIX foaf: <http://xmlns.com/foaf/0.1/> 
DELETE WHERE { :a foaf:knows ?b }

SSE

(prefix
 ((: <http://example.org/>)
  (foaf: <http://xmlns.com/foaf/0.1/>))
 (update
  (deleteWhere ((triple :a foaf:knows ?b)))))

See Also:

Constant Summary collapse

NAME = 
[:deleteWhere]

Constants inherited from Unary

Unary::ARITY

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 Unary

#initialize

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::Unary

Instance Method Details

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

Query the operand, and delete all statements created by binding each solution to the patterns

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/delete_where.rb', line 43

def execute(queryable, **options)
  # Operands are an array of patterns and Queries (when named).
  # Create a new query made up all patterns
  patterns = operand.inject([]) do |memo, op|
    if op.respond_to?(:statements)
      memo += op.statements.to_a
    else
      memo << op
    end
    memo
  end
  query = RDF::Query.new(*patterns, **{}) # FIXME: added hash argument needed until Statement#to_hash removed.
  debug(options) {"DeleteWhere query #{query.to_sse}"}
  query.execute(queryable, **options.merge(depth: options[:depth].to_i + 1)) do |solution|
    debug(options) {"DeleteWhere solution #{solution.to_sse}"}
    query.each_statement do |pattern|
      pattern = pattern.dup.bind(solution)
      debug(options) {"DeleteWhere pattern #{pattern.to_sse}"}
      queryable.delete(RDF::Statement.from(pattern)) if pattern.bound? || pattern.constant?
    end
  end
  queryable
end

#to_sparql(**options) ⇒ String

Returns a partial SPARQL grammar for this term.

Returns:

  • (String) 


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# File 'lib/sparql/algebra/operator/delete_where.rb', line 72

def to_sparql(**options)
  "DELETE WHERE {\n" +
    operands.first.to_sparql(top_level: false, delimiter: ". \n", **options) +
    "\n}"
end