Github user wzhfy commented on the issue:

    https://github.com/apache/spark/pull/16401
  
    do you mean no cache for `def statistics(conf)`:
    ```
    def statistics(conf: CatalystConf): Statistics = {
      if(conf.cboEnabled) newStats else oldStats
    }
    lazy val newStats...
    lazy val oldStats...
    ```
    or no cache for anything:
    ```
    def statistics(conf: CatalystConf): Statistics = {
      if(conf.cboEnabled) { calculate old stats } else { calculated new stats }
    }
    ```
    The lattter can be a performance hit because statistics need to be computed 
every time it's called.


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