Module: Factbase::IndexedTerm

Defined in:
lib/factbase/indexed/indexed_term.rb

Overview

Term with an index.

Author

Yegor Bugayenko ([email protected])

Copyright

Copyright © 2024-2025 Yegor Bugayenko

License

MIT

Instance Method Summary collapse

Instance Method Details

#predict(maps, params) ⇒ Array<Hash>|nil

Reduces the provided list of facts (maps) to a smaller array, if it’s possible.

NIL must be returned if indexing is prohibited in this case.



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# File 'lib/factbase/indexed/indexed_term.rb', line 22

def predict(maps, params)
  key = [maps.object_id, @operands.first, @op]
  case @op
  when :one
    if @idx[key].nil?
      @idx[key] = []
      prop = @operands.first.to_s
      maps.to_a.each do |m|
        @idx[key].append(m) if !m[prop].nil? && m[prop].size == 1
      end
    end
    (maps & []) | @idx[key]
  when :exists
    if @idx[key].nil?
      @idx[key] = []
      prop = @operands.first.to_s
      maps.to_a.each do |m|
        @idx[key].append(m) unless m[prop].nil?
      end
    end
    (maps & []) | @idx[key]
  when :eq
    if @operands.first.is_a?(Symbol) && _scalar?(@operands[1])
      if @idx[key].nil?
        @idx[key] = {}
        prop = @operands.first.to_s
        maps.to_a.each do |m|
          m[prop]&.each do |v|
            @idx[key][v] = [] if @idx[key][v].nil?
            @idx[key][v].append(m)
          end
        end
      end
      vv =
        if @operands[1].is_a?(Symbol)
          params[@operands[1].to_s] || []
        else
          [@operands[1]]
        end
      if vv.empty?
        nil
      else
        j = vv.map { |v| @idx[key][v] || [] }.reduce(&:|)
        (maps & []) | j
      end
    end
  when :and
    r = nil
    if @operands.all? { |o| o.op == :eq } && @operands.size > 1 \
      && @operands.all? { |o| o.operands.first.is_a?(Symbol) && _scalar?(o.operands[1]) }
      key = [maps.object_id, @operands.map { |o| o.operands.first }, :multi_eq]
      props = @operands.map { |o| o.operands.first }.sort
      if @idx[key].nil?
        @idx[key] = {}
        maps.to_a.each do |m|
          _all_tuples(m, props).each do |t|
            @idx[key][t] = [] if @idx[key][t].nil?
            @idx[key][t].append(m)
          end
        end
      end
      tuples = _as_tuples(
        @operands.sort_by { |o| o.operands.first }.map do |o|
          if o.operands[1].is_a?(Symbol)
            params[o.operands[1].to_s] || []
          else
            [o.operands[1]]
          end
        end
      )
      j = tuples.map { |t| @idx[key][t] || [] }.reduce(&:|)
      r = (maps & []) | j
    else
      @operands.each do |o|
        n = o.predict(maps, params)
        if n.nil?
          r = nil
          break
        end
        if r.nil?
          r = n
        else
          r &= n.to_a
        end
        break if r.empty?
      end
    end
    r
  when :or
    r = nil
    @operands.each do |o|
      n = o.predict(maps, params)
      if n.nil?
        r = nil
        break
      end
      r = maps & [] if r.nil?
      r |= n.to_a
    end
    r
  when :not
    r = @operands.first.predict(maps, params)
    if r.nil?
      nil
    else
      (maps & []) | (maps.to_a - r.to_a)
    end
  end
end