Benefit of following setting.

[mahender bigdata]

Hi,

I have doubt on following setting, where i could not find clear meaning 
of these setting

 * SET hive.optimize.index.filter=false;



 * set hive.mapjoin.hybridgrace.hashtable=false;


 * set hive.optimize.null.scan=false;


 * Is there any negative by enabling hive.optimize.index.filter all the
   time.



 * If smaller dataset, try to run local mode i.e set
   hive.auto.convert.join=true; Can any one tell me what is meant by
   local mode and cluster/server mode ?

Thanks in advance

Mahender