title: LevelDB: Lifetime and responsibility of comparators, block_cache and filter_policy?
body: <p>Do I need to delete my comparators, block_cache and filter_policy after closing my database? Do they need to exist during the lifetime of the database?</p>
  
  <p>I cannot find this info in any of the documentation.</p>
  
  <p>From looking at the source code, I'm guessing that I need to delete them after closing the database but they need to persist during the lifetime while it's open.</p>
  
  <p>Thanks</p>