Class: SPARQL::Algebra::Operator::With

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

Overview

The SPARQL UPDATE with operator.

The WITH clause provides a convenience for when an operation primarily refers to a single graph.

[41] Modify ::= ( ‘WITH’ iri )? ( DeleteClause InsertClause? | InsertClause ) UsingClause* ‘WHERE’ GroupGraphPattern

Examples:

SPARQL Grammar

PREFIX  :     <http://example/>
WITH :g
DELETE { <base:s> ?p ?o . }
WHERE { ?s ?p ?o }

SSE

(prefix ((: <http://example/>))
 (update
  (modify
   (with :g
    (bgp (triple ?s ?p ?o))
    (delete ((triple <base:s> ?p ?o)))))))

See Also:

Constant Summary collapse

NAME = 
:with

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.

Effectively filters results by setting a default graph_name variable so that it is used when binding to perform update operations on the appropriate triples.

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/with.rb', line 47

def execute(queryable, **options)
  debug(options) {"With: #{operand.to_sse}"}
  # Bound variable
  name = operands.shift

  unless queryable.has_graph?(name)
    debug(options) {"=> default data source #{name}"}
    load_opts = {logger: options.fetch(:logger, false), base_uri: name}
    debug(options) {"=> load #{name}"}
    queryable.load(name.to_s, **load_opts)
  end

  # Set name for RDF::Graph descendants having no graph_name to the name variable
  each_descendant do |op|
    case op
    when RDF::Query, RDF::Query::Pattern
      unless op.graph_name
        debug(options) {"set graph_name on #{op.to_sse}"}
        op.graph_name = RDF::Query::Variable.new(:__graph_name__, name)
      end
    end
  end
  query = operands.shift

  # Restrict query portion to this graph
  queryable.query(query, **options.merge(depth: options[:depth].to_i + 1)) do |solution|
    debug(options) {"(solution)=>#{solution.inspect}"}

    # Execute each operand with queryable and solution
    operands.each do |op|
      op.execute(queryable, solutions: solution, **options.merge(depth: options[:depth].to_i + 1))
    end
  end
end

#to_sparql(**options) ⇒ String

Returns a partial SPARQL grammar for this operator.

Returns:

  • (String) 


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# File 'lib/sparql/algebra/operator/with.rb', line 87

def to_sparql(**options)
  with, where, *ops = operands
  str = "WITH #{with.to_sparql(**options)}\n"

  # The content of the WHERE clause, may be USING
  content = where.to_sparql(top_level: false, **options)

  # DELETE | INSERT | DELETE INSERT
  str << ops.to_sparql(top_level: false, delimiter: "\n", **options) + "\n"

  # Append the WHERE or USING clause
  str << if where.is_a?(Using)
    content
  else
    Operator.to_sparql(content, project: nil, **options)
  end
end