Class: SPARQL::Algebra::Operator::Dataset

Inherits:
Binary show all
Includes:
Query
Defined in:
lib/sparql/algebra/operator/dataset.rb

Overview

The SPARQL GraphPattern dataset operator.

Instintiated with two operands, the first being an array of data source URIs, either bare, indicating a default dataset, or expressed as an array [:named, ], indicating that it represents a named data source.

Examples:

(prefix ((: <http://example/>))
  (dataset (<data-g1.ttl> (named <data-g2.ttl>))
    (bgp (triple ?s ?p ?o))))

See Also:

Constant Summary collapse

NAME = 
[:dataset]

Constants inherited from Binary

Binary::ARITY

Constants inherited from SPARQL::Algebra::Operator

ARITY

Instance Attribute Summary

Attributes included from Query

#solutions

Attributes inherited from SPARQL::Algebra::Operator

#operands, #options

Instance Method Summary collapse

Methods included from Query

#context=, #each_solution, #failed?, #matched?, #unshift, #variables

Methods inherited from Binary

#initialize

Methods inherited from SPARQL::Algebra::Operator

arity, base_uri, #base_uri, base_uri=, #boolean, #constant?, #eql?, #evaluatable?, evaluate, #executable?, for, #initialize, #inspect, #operand, prefixes, #prefixes, prefixes=, #to_sse, #to_sxp, #variable?

Methods included from Evaluatable

#apply, #evaluate, #memoize

Methods included from Expression

cast, #constant?, #evaluate, for, new, open, parse, #to_sse, #variable?

Constructor Details

This class inherits a constructor from SPARQL::Algebra::Operator::Binary

Instance Method Details

#execute(queryable, options = {}) ⇒ RDF::Query::Solutions

Executes this query on the given queryable graph or repository. Reads specified data sources into queryable. Named data sources are added using a context of the data source URI.

Datasets are specified in operand(1), which is an array of default or named graph URIs.

Parameters:

  • queryable (RDF::Queryable) —

    the graph or repository to query

  • options (Hash{Symbol => Object}) (defaults to: {}) —

    any additional keyword options

Returns:

See Also:


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# File 'lib/sparql/algebra/operator/dataset.rb', line 35

def execute(queryable, options = {})
  debug("Dataset", options)
  operand(0).each do |ds|
    load_opts = {}
    case ds
    when Array
      uri = if self.base_uri
        u = self.base_uri.join(ds.last)
        u.lexical = "<#{ds.last}>" unless u.to_s == ds.last.to_s
        u
      else
        ds.last
      end
      uri = self.base_uri ? self.base_uri.join(ds.last) : ds.last
      uri.lexical = ds.last
      load_opts[:context] = uri
      debug("=> read named data source #{uri}", options)
    else
      uri = self.base_uri ? self.base_uri.join(ds) : ds
      debug("=> read default data source #{uri}", options)
    end
    queryable.load(uri.to_s, load_opts)
  end

  @solutions = operands.last.execute(queryable, options.merge(:depth => options[:depth].to_i + 1))
end

#optimize ⇒ Union, RDF::Query

Returns an optimized version of this query.

If optimize operands, and if the first two operands are both Queries, replace with the unique sum of the query elements

Returns:


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# File 'lib/sparql/algebra/operator/dataset.rb', line 69

def optimize
  operands.last.optimize
end