michaelmior / NoSE

module NoSE

  module Search

    # A container for results from a schema search

    class Results

      attr_reader :cost_model

      attr_accessor :enumerated_indexes, :indexes, :total_size, :total_cost,

                    :workload, :update_plans, :plans,

                    :revision, :time, :command, :by_id_graph

      def initialize(problem = nil, by_id_graph = false)

        @problem = problem

        return if problem.nil?

        @by_id_graph = by_id_graph

        # Find the indexes the ILP says the query should use

        @query_indexes = Hash.new { |h, k| h[k] = Set.new }

        @problem.query_vars.each do |index, query_vars|

          query_vars.each do |query, var|

            next unless var.value

            @query_indexes[query].add index

          end

        end

      end

      # Provide access to the underlying model in the workload

      # @return [Model]

      def model

        @workload.nil? ? @model : @workload.model

      end

      # Assign the model to the workload if it exists, otherwise store it

      # @return [void]

      # After setting the cost model, recalculate the cost

      # @return [void]

      def cost_model=(new_cost_model)

        recalculate_cost new_cost_model

        @cost_model = new_cost_model

      end

      # After setting the cost model, recalculate the cost

      # @return [void]

        new_cost_model = @cost_model if new_cost_model.nil?

        (@plans || []).each do |plan|

          plan.each { |s| s.calculate_cost new_cost_model }

        end

        (@update_plans || []).each do |plan|

          plan.update_steps.each { |s| s.calculate_cost new_cost_model }

          plan.query_plans.each do |query_plan|

            query_plan.each { |s| s.calculate_cost new_cost_model }

          end

        end

        # Recalculate the total

        query_cost = (@plans || []).sum_by do |plan|

          plan.cost * @workload.statement_weights[plan.query]

        end

        update_cost = (@update_plans || []).sum_by do |plan|

          plan.cost * @workload.statement_weights[plan.statement]

        end

        @total_cost = query_cost + update_cost

      end

      # Validate that the results of the search are consistent

      # @return [void]

      def validate

        validate_indexes

        validate_query_indexes @plans

        validate_update_indexes

        planned_queries = plans.map(&:query).to_set

        fail InvalidResultsException unless \

          (@workload.queries.to_set - planned_queries).empty?

        validate_query_plans @plans

        validate_update_plans

        validate_objective

        freeze

      end

      # Set the query plans which should be used based on the entire tree

      # @return [void]

      def plans_from_trees(trees)

        @plans = trees.map do |tree|

          # Exclude support queries since they will be in update plans

          query = tree.query

          next if query.is_a?(SupportQuery)

          select_plan tree

        end.compact

      end

      # Select the single query plan from a tree of plans

      # @return [Plans::QueryPlan]

      # @raise [InvalidResultsException]

      def select_plan(tree)

        query = tree.query

        plan = tree.find do |tree_plan|

          tree_plan.indexes.to_set == @query_indexes[query]

        end

        plan.instance_variable_set :@workload, @workload

        fail InvalidResultsException if plan.nil?

        plan

      end

      private

      # Check that the indexes selected were actually enumerated

      # @return [void]

      def validate_indexes

        # We may not have enumerated ID graphs

        check_indexes = @indexes.dup

        @indexes.each do |index|

          check_indexes.delete index.to_id_graph

        end if @by_id_graph

        fail InvalidResultsException unless \

          (check_indexes - @enumerated_indexes).empty?

      end

      # Ensure we only have necessary update plans which use available indexes

      # @return [void]

      def validate_update_indexes

        @update_plans.each do |plan|

          validate_query_indexes plan.query_plans

          valid_plan = @indexes.include?(plan.index)

          fail InvalidResultsException unless valid_plan

        end

      end

      # Check that the objective function has the expected value

      # @return [void]

        if @problem.objective_type == Objective::COST

          query_cost = @plans.reduce 0 do |sum, plan|

            sum + @workload.statement_weights[plan.query] * plan.cost

          end

          update_cost = @update_plans.reduce 0 do |sum, plan|

            sum + @workload.statement_weights[plan.statement] * plan.cost

          end

          cost = query_cost + update_cost

          fail InvalidResultsException unless (cost - @total_cost).abs < 0.001

        elsif @problem.objective_type == Objective::SPACE

          size = @indexes.sum_by(&:size)

          fail InvalidResultsException unless (size - @total_size).abs < 0.001

        end

      end

      # Ensure that all the query plans use valid indexes

      # @return [void]

      def validate_query_indexes(plans)

        plans.each do |plan|

          plan.each do |step|

            valid_plan = !step.is_a?(Plans::IndexLookupPlanStep) ||

                         @indexes.include?(step.index)

            fail InvalidResultsException unless valid_plan

          end

        end

      end

      # Validate the query plans from the original workload

      # @return [void]

      def validate_query_plans(plans)

        # Check that these indexes are actually used by the query

        plans.each do |plan|

          fail InvalidResultsException unless \

            plan.indexes.to_set == @query_indexes[plan.query]

        end

      end

      # Validate the support query plans for each update

      # @return [void]

      def validate_update_plans

        @update_plans.each do |plan|

          plan.instance_variable_set :@workload, @workload

          validate_query_plans plan.query_plans

        end

      end

    end

    # Thrown when a search produces invalid results

    class InvalidResultsException < StandardError

    end

  end

end