Module: RDF::Query::Executer

Included in:
Graph::Memory
Defined in:
lib/rdf/query/executer.rb

Overview

A mix-in module for graph implementations. If a Graph implementation cannot delegate the execute method to the underlying triplestore, then this module can be mixed in to provide Query execution. The graph must only implement the match method.

Instance Method Summary collapse

Instance Method Details

#execute(query) ⇒ Object

Returns the result of executing query on this graph.



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# File 'lib/rdf/query/executer.rb', line 9

def execute(query)
  result = nil
  
  where_clause = query.where_clause
  begin
    s, p, o = where_clause.shift
    result = match(s, p, o, result)
  end while where_clause.any? && result.success?
  
  result
end

#match(s, p, o, result = nil) ⇒ Object

Performs a match of s, p, and o and returns a set of bindings.

If s, p, or o are Ruby symbols, then they will be considered variables, and they will be bound to all possible nodes in the result.

If s, p, or o are BlankNodes that are unassociated with this graph, then they will be bound to all possible nodes in the result.



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# File 'lib/rdf/query/executer.rb', line 28

def match(s, p, o, result = nil)
  if result.nil?
    result = match_binding(s, p, o, RDF::Query::Binding.new)
    result
  else
    result = result.bindings.inject(RDF::Query::Result.new) do |r, b|
      r << match_binding(s, p, o, b)
      r
    end
    result
  end
end