lib/gitlab/database/as_with_materialized.rb


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# frozen_string_literal: true

module Gitlab
  module Database
    # This class is a special Arel node which allows optionally define the `MATERIALIZED` keyword for CTE and Recursive CTE queries.
    class AsWithMaterialized < Arel::Nodes::As
      extend Gitlab::Utils::StrongMemoize

      MATERIALIZED = 'MATERIALIZED '

      def initialize(left, right, materialized: true)
        if materialized && self.class.materialized_supported?
          right.prepend(MATERIALIZED)
        end

        super(left, right)
      end

      # Note: to be deleted after the minimum PG version is set to 12.0
      def self.materialized_supported?
        strong_memoize(:materialized_supported) do
          Gitlab::Database.main.version.match?(/^1[2-9]\./) # version 12.x and above
        end
      end

      # Note: to be deleted after the minimum PG version is set to 12.0
      # Update the documentation together when deleting the method
      # https://docs.gitlab.com/ee/development/merge_request_performance_guidelines.html#use-ctes-wisely
      def self.materialized_if_supported
        materialized_supported? ? 'MATERIALIZED' : ''
      end
    end
  end
end