activerecord/lib/active_record/statement_cache.rb


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module ActiveRecord

  # Statement cache is used to cache a single statement in order to avoid creating the AST again.
  # Initializing the cache is done by passing the statement in the initialization block:
  #
  #   cache = ActiveRecord::StatementCache.new do
  #     Book.where(name: "my book").limit(100)
  #   end
  #
  # The cached statement is executed by using the +execute+ method:
  #
  #   cache.execute
  #
  # The relation returned by the block is cached, and for each +execute+ call the cached relation gets duped.
  # Database is queried when +to_a+ is called on the relation.
  class StatementCache
    def initialize
      @relation = yield
      raise ArgumentError.new("Statement cannot be nil") if @relation.nil?
    end

    def execute(binds = nil)
      rel = @relation.dup
      if (binds != nil)         
        rel.replace_binds binds
      end
      rel.to_a
    end
  end
end