Thank you very much Tim. Provided link has clarified my doubt.  ... View more

Thanks Tim, How long Impala keeps/caches this metadata?  If statistics of tables which are participating in query are not available then will it be available after first run? What if I run the query after big interval, then also will metadata be available in cache?  What is my cluster or Impala is restarted? Does Impala perform some activity to get statistics of all the participating tables for the first time if statistics are not available and keep it in metastore or some where in DB? ... View more

Thank you very much Tim for providing this insight.  I have assumption that MEM_LIMIT option is asking for that amount of space for query. ... View more

Thanks Tim, This limit(3gb) only work when your IMPALAD's mem_limit is greater than 3gb. I've increased the IMPALAD's mem_limit by invoking the rest api and by manually changing the configuration of Impala but in this way you have to restart the Impala server then only mem_limit will work.  I can not understand if IMPALAD's mem_limit is 1gb and if I pass the higher mem_limit (query_option) in jdbc URL then it won't work. What is the point of providing this query option.  (1) If my query needed 3gb memory and IMPALAD's mem_limit is 1 gb and I am passing mem_limit=3gb is JDBC url then it won't work. I've to change the mem_limit of IMPALAD and restart the server. And  (2) If my query needed 500mb memory and IMPALAD's mem_limit is 1 gb then I don't need to pass mem_limit because in any case it is going to execute. Hope you understood my point. I can conclude that this query option can prevent query to take entire memory of IMPALAD, not for allocating the required memory. ... View more