NAME

       Attean::QueryPlanner - Query planner

VERSION

       This document describes Attean::QueryPlanner version 0.019

SYNOPSIS

         use v5.14;
         use Attean;
         my $planner = Attean::QueryPlanner->new();
         my $default_graphs = [ Attean::IRI->new('http://example.org/') ];
         my $plan = $planner->plan_for_algebra( $algebra, $model, $default_graphs );
         my $iter = $plan->evaluate($model);
         while (my $result = $iter->next()) {
           say $result->as_string;
         }

DESCRIPTION

       The Attean::QueryPlanner class is a base class implementing common behavior for query planners.
       Subclasses will need to consume or compose the Attean::API::JoinPlanner role.

       Trivial sub-classes may consume Attean::API::NaiveJoinPlanner, while more complex planners may choose to
       implement complex join planning (e.g.  Attean::IDPQueryPlanner).

ATTRIBUTES

METHODS

       "new_temporary( $type )"
           Returns a new unique (in the context of the query planner) ID string that may be used for things like
           fresh (temporary) variables. The $type string is used in the generated name to aid in identifying
           different uses for the names.

       "plan_for_algebra( $algebra, $model, \@active_graphs, \@default_graphs )"
           Returns the first plan returned from "plans_for_algebra".

       "plans_for_algebra( $algebra, $model, \@active_graphs, \@default_graphs )"
           Returns Attean::API::Plan objects representing alternate query plans for evaluating the query
           $algebra against the $model, using the supplied $active_graph.

       "simplify_path( $subject, $path, $object )"
           Return a simplified Attean::API::Algebra object corresponding to the given property path.

       "new_projection( $plan, $distinct, @variable_names )"
           Return a new Attean::Plan::Project plan over $plan, projecting the named variables. $disctinct should
           be true if the caller can guarantee that the resulting plan will produce distinct results, false
           otherwise.

           This method takes care of computing plan metadata such as the resulting ordering.

       "bgp_join_plans( $bgp, $model, \@active_graphs, \@default_graphs, \@interesting_order, \@plansA,
       \@plansB, ... )"
           Returns a list of alternative plans for the join of a set of triples.  The arguments @plansA,
           @plansB, etc. represent alternative plans for each triple participating in the join.

       "group_join_plans( $model, \@active_graphs, \@default_graphs, \@interesting_order, \@plansA, \@plansB,
       ... )"
           Returns a list of alternative plans for the join of a set of sub-plans.  The arguments @plansA,
           @plansB, etc. represent alternative plans for each sub-plan participating in the join.

       "joins_for_plan_alternatives( $model, \@active_graphs, \@default_graphs, $interesting, \@plan_A,
       \@plan_B, ... )"
           Returns a list of alternative plans that may all be used to produce results matching the join of
           "plan_A", " plan_B ">, etc. Each plan array here (e.g. @plan_A) should contain equivalent plans.

       "access_plans( $model, $active_graphs, $pattern )"
           Returns a list of alternative Attean::API::Plan objects that may be used to produce results matching
           the Attean::API::TripleOrQuadPattern $pattern in the context of $active_graphs.

       "join_plans( $model, \@active_graphs, \@default_graphs, \@plan_left, \@plan_right, $type [, $expr] )"
           Returns a list of alternative plans for the join of one plan from @plan_left and one plan from
           @plan_right. The join $type must be one of 'inner', 'left', or 'minus', indicating the join algorithm
           to be used. If $type is 'left', then the optional $expr may be used to supply a filter expression
           that should be used by the SPARQL left-join algorithm.

BUGS

       Please report any bugs or feature requests to through the GitHub web interface at
       <https://github.com/kasei/attean/issues>.

SEE ALSO

AUTHOR

       Gregory Todd Williams  "<gwilliams@cpan.org>"

COPYRIGHT

       Copyright (c) 2014--2018 Gregory Todd Williams.  This program is free software; you can redistribute it
       and/or modify it under the same terms as Perl itself.